Dissertations / Theses: 'Induced seismicity'

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Larsson, Kristina. "Mining induced seismicity in Sweden." Licentiate thesis, Luleå, 2004. http://epubl.luth.se/1402-1757/2004/80.

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Li, Junlun Ph D. Massachusetts Institute of Technology. "Study of induced seismicity for reservoir characterization." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84917.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The main goal of the thesis is to characterize the attributes of conventional and unconventional reservoirs through passive seismicity. The dissertation is comprised of the development and applications of three new methods, each of which focuses on a different aspect of fractures/faults and the resulting seismicity. In general, the thesis work discusses reservoir characterization from two aspects: 1) understanding fractures and faults in reservoirs as seismic sources with induced seismicity, and then inferring other properties of the reservoirs, such as stress regime and velocity structure (Chapters 2, 3, 4); 2) understanding the fractures in reservoirs as seismic scatterers (Chapter 5). First, I introduce a new method to determine the source mechanisms of the induced earthquakes by incorporating high frequency waveform matching, first P-arrival polarities and average S/P amplitude ratios. The method is applied to 40 induced earthquakes from an oil/gas field in Oman monitored by a sparse near-surface seismic network and a deep borehole seismic network. The majority of the events have a strike direction parallel with the major NE-SW faults in the region, and some events trend parallel with the NW-SE conjugate faults. The results are consistent with the in-situ well breakout measurements and the current knowledge of the stress direction of this region. The source mechanisms of the studied events together with the hypocenter distribution indicate that the microearthquakes are caused by the reactivation of preexisting faults. Then I introduce a new method to locate microseismic events induced by hydraulic fracturing with simultaneous anisotropic velocity inversion using differential arrival times and differential back azimuths. We derive analytical sensitivities for the elastic moduli (Cij) and layer thickness L for the anisotropic velocity inversion. The method is then applied to a microseismic dataset monitoring a Middle Bakken completion in the Beaver Lodge area of North Dakota. Our results show: 1) moderate-to-strong anisotropy exists in all studied sedimentary layers, especially in both the Upper Bakken and Lower Bakken shale formations, where the Thomsen parameters (E and y) can be over 40%; 2) all events selected for high signal-to-noise ratio and used for the joint velocity inversion are located in the Bakken and overlying Lodgepole formations, i.e., no strong events are located in the Three Forks formation below the Bakken; 3) more than half of the strong events are in two clusters at about 100 and 150 meters above the Middle Bakken. Re-occurrence of strong, closely clustered events suggests activation of natural fractures or faults in the Lodgepole formation. Finally, I introduce a new hybrid method to model the shear (SH) wave scattering from arbitrarily shaped fractures embedded in a heterogeneous medium by coupling the boundary element method (BEM) and the finite difference method (FDM) in the frequency domain. The hybrid method can calculate scattering from arbitrarily shaped fractures very rapidly, thus Monte Carlo simulations for characterizing the statistics of fracture attributes can be performed efficiently. The advantages of the hybrid method are demonstrated by modeling waves scattered from tilted fractures embedded in complex media. Interesting behaviors of the scattered waves, such as frequency shift with the scattering order and coherent pattern of scattered waves through strong heterogeneities, are observed. This method can be used to analyze and interpret the scattered coda waves in the microseismic observations, e.g., the reverberating multiples in the Bakken microseismic data which cannot be explained by the determined layered anisotropic velocity model alone.
by Junlun Li.
Ph.D.

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Holmgren, Joanna. "Induced Seismicity in the Dannemora Mine, Sweden." Thesis, Uppsala universitet, Geofysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267361.

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Induced seismicity is a common phenomenon that occurs as soon as the stress state in the subsurface is externally altered in a way that faults are destabilized. It is especially problematic in stable tectonic regions where the area is not used to earthquakes; the infrastructure is not built to withstand ground movement and thus when the induced seismicity occurs damage can follow. In this thesis, mining-induced seismicity has been studied at the Dannemora mine, located in central Sweden, with the aim to locate the seismicity and gain understanding of its occurrence and behavior. The mining company, Dannemora Mineral AB, provided with blasting locations and times, as well as maps over the mine's orebodies and stopes. Seismic data acquired between 01 July 2014 - 25 March 2015 from 4 temporary seismic stations, deployed in the summer of 2014 surrounding the mine, along with 8 SNSN stations was analyzed. The project encompassed field work and processing of the data, which involved different methods to investigate the characteristics of the mine's seismicity: Statistics were kept to record the activity rate of the seismicity over time; spectral analysis was used to study the frequency content of the seismicity; particle motion plots were constructed to identify body-phases in the seismicity; Local Earthquake Tomography was used to upgrade the velocity model of the mine and to relocate the induced seismicity with more accuracy; cross-correlation was used to find events originating from similar sources; and finally, magnitude analysis was used to compare the different types of seismicity within the mine. Three main types of induced events were observed in the mine: low-frequency events with clear first arrivals, emergent events with long duration, and high-frequency events that could either have clear first arrivals or emergent-like with long durations. Through the analysis of their characteristics, they were linked to different types of rockbursts. The low-frequency events were linked to both reactivation of fault zones triggered by the mine activity, and rockbursts within the mine directly related to the mining. The emergent and high-frequency events were also linked to rockbursts directly related to the mine activity, e.g. ejection of rock from the tunnel walls or arch collapses in stopes.

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Bredenkamp, Ben. "Analysis and modelling of mining induced seismicity." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2257.

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Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006.
Earthquakes and other seismic events are known to have catastrophic effects on people and property. These large-scale events are almost always preceded by smallerscale seismic events called precursors, such as tremors or other vibrations. The use of precursor data to predict the realization of seismic hazards has been a long-standing technical problem in different disciplines. For example, blasting or other mining activities have the potential to induce the collapse of rock surfaces, or the occurrence of other dangerous seismic events in large volumes of rock. In this study, seismic data (T4) obtained from a mining concern in South Africa were considered using a nonlinear time series approach. In particular, the method of surrogate analysis was used to characterize the deterministic structure in the data, prior to fitting a predictive model. The seismic data set (T4) is a set of seismic events for a small volume of rock in a mine observed over a period of 12 days. The surrogate data were generated to have structure similar to that of T4 according to some basic seismic laws. In particular, the surrogate data sets were generated to have the same autocorrelation structure and amplitude distributions of the underlying data set T4. The surrogate data derived from T4 allow for the assessment of some basic hypotheses regarding both types of data sets. The structure in both types of data (i.e. the relationship between the past behavior and the future realization of components) was investigated by means of three test statistics, each of which provided partial information on the structure in the data. The first is the average mutual information between the reconstructed past and futures states of T4. The second is a correlation dimension estimate, Dc which gives an indication of the deterministic structure (predictability) of the reconstructed states of T4. The final statistic is the correlation coefficients which gives an indication of the predictability of the future behavior of T4 based on the past states of T4. The past states of T4 was reconstructed by reducing the dimension of a delay coordinate embedding of the components of T4. The map from past states to future realization of T4 values was estimated using Long Short-Term Recurrent Memory (LSTM) neural networks. The application of LSTM Recurrent Neural Networks on point processes has not been reported before in literature. Comparison of the stochastic surrogate data with the measured structure in the T4 data set showed that the structure in T4 differed significantly from that of the surrogate data sets. However, the relationship between the past states and the future realization of components for both T4 and surrogate data did not appear to be deterministic. The application of LSTM in the modeling of T4 shows that the approach could model point processes at least as well or even better than previously reported applications on time series data.

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Boonzaaier, Leandro. "Self-organised criticality and seismicity." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53047.

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Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: In this thesis we give an overview of self-organised criticality and its application to studying seismicity. We recall some of the basic models and techniques for studying self-organised critical systems. We discuss one of these, the sandpile model, in detail and show how various properties of the model can be calculated using a matrix formulation thereof. A correspondence between self-organised critical systems and seismicity is then proposed. Finally, we consider the timeevolution of the sandpile model by using a time-to-failure analysis, originally developed in the study of seismicity and obtain results for the sandpile model that show similarities with that of the analyses of seismic data.
AFRIKAANSE OPSOMMING: In hierdie tesis gee ons 'n oorsig van self-organiserende kritikaliteit en die toepassing daarvan in die studie van seismisiteit. Ons beskryf die basiese modelle en tegnieke vir die studie van self-organiserende kritiese sisteme. Ons bespreek een van hierdie, die sandhoopmodel, in besonderheid en wys hoe om verskeie eienskappe van die model te bereken deur gebruik te maak van 'n matriks-formulering daarvan. Ons stel dan 'n korrespondensie tussen self-organiserende kritiese sisteme en seismisiteit voor. Ter afsluiting ondersoek ons die tydontwikkeling van die sand hoopmodel deur gebruik te maak van 'n deurbreektyd analise wat oorspronklik in die bestudering seismiese data ontwikkel is. Die resultate vir die analise van die sandhoopmodel toon ooreenkomste met dit wat verkry word vir seismiese data.

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Hooper, Heather J. (Heather Julie) 1975. "Analysis and modeling of induced seismicity in petroleum reservoirs." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/54445.

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Thesis (S.M. in Geosystems)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002.
Includes bibliographical references (p. 53).
Since 1998, a producing oil field in Oman has been experiencing microearthquake activity. The aim of this project is to compare numerical models of wave propagation using simple source representations to a small subset of these microearthquakes, with three goals in mind: 1) to understand whether the microearthquakes are generated by movement along a known fault system in the field, or by some other mechanism; 2) if the source is fault related, to better understand what kind of movement is occurring on the fault; and 3) to see if this simple modeling method provides useful results, and forms a basis for future work. Synthetic waveforms are generated using a one-dimensional, discrete wavenumber numerical model (Bouchon, 1980) with two simple source representations: an explosive point source and a vertical force. Comparison of the synthetic waveforms to the microearthquake data indicates that the vertical force results in a better match than the explosive point source. In addition, a simple model consisting of the superposition of four vertical forces (representing vertical fault rupture), results in waveforms that are very similar to the recorded events. These results suggest that the source of the microearthquakes is motion along a near-vertical normal fault system that has been mapped in the field. These results are also consistent with work by Sze and Toksoz (2001) in which relocation of the same events imaged a near-vertical normal fault in the field. Further work using fault rupture source modeling may provide additional insight into the amount of fault motion that is occurring in relation to these events.
by Heather J. Hooper.
S.M.in Geosystems

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Kondas, Sean Michael. "Crustal unloading as a source of induced seismicity in Plainfield, Connecticut:." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:109092.

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Thesis advisor: John E. Ebel
Thesis advisor: Mark D. Behn
On January 12, 2015, a magnitude 3.1 mainshock occurred in Plainfield, Connecticut near Wauregan Tilcon Quarry, causing modified Mercalli II-IV intensities. Shortly after the event, a team from Weston Observatory installed portable seismographs in the epicentral area. The portable array detected hundreds of small earthquakes from around the quarry, with 26 events that were accurately located. P-wave first motion directions obtained from readings of the mainshock suggest a thrusting focal mechanism on a NNE-SSW trending fault. In this research, we collected 113 gravity measurements in the proximity of the quarry to verify and correct local fault geometry proposed by historic aeromagnetic and geologic mapping. Interpretations of the computed simple Bouguer anomaly are consistent with historic mapping, with a few exceptions. The gravity survey constrains a NNE-SSW trending fault that dips west underneath the quarry, inferred to be the Lake Char-Honey Hill Fault, and reduces ambiguity in the position of an undefined ESE-WNW trending fault, which appears to be on strike to intersect the quarry. A 3D boundary element program (3D~Def) is used to simulate quarry-induced stress changes on these faults in order to analyze the possibility of inducing seismicity through crustal unloading in the region. Quarry operations resulted in the removal of mass from the crust, which decreased lithostatic load. In a setting confined by a maximum horizontal compressional stress, decreasing the lithostatic load, orminimum principal stress (σ3), shifts a Mohr-Coulomb diagram toward failure. The boundary element model shows that following the excavation of materials at the quarry, positive Coulomb failure stress changes occur on the west dipping Lake Char-Honey Hill Fault. In agreement with past studies, our results suggest that quarrying operations can trigger seismic activity in specific settings with stress regime, fault orientations, and rock characteristics such as those that exist in the northeastern U.S. In order to mitigate the risk for future earthquakes related to quarrying operations, these factors must be considered before operations begin
Thesis (MS) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences

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Al-busaidi, Ahmed. "Distinct element modelling of hydraulically-induced fracture and associated seismicity." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406824.

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Martínez-Garzón, Patricia [Verfasser]. "Seismo-mechanical reservoir characterization from fluid-induced seismicity / Patricia Martínez-Garzón." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1056908165/34.

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Sarkar, Sudipta. "Reservoir monitoring using induced seismicity at a petroleum field in Oman." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45765.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.
Includes bibliographical references.
This thesis presents methods of analysis and results from a petroleum reservoir monitoring application using induced seismicity data. The dissertation work is comprised of four major studies, each focusing on a different aspect of induced seismicity. First, methods and issues in location of induced seismicity are discussed, and strategies are proposed for determining accurate hypocenters of induced events. The importance of velocity model and how it impacts the depth determination of reservoir-induced events are demonstrated with real field data. A location method that is better-suited than other existing methods for this application is proposed. The accuracy and efficiency of this proposed location method is demonstrated with field data application.Secondly, event locations and interpretations are presented for about 1300 induced events recorded by a near-surface network over a seven year period at a petroleum field in Oman. The event hypocenters delineate two major northeast-southwest striking faults in the field, which are consistent with fault maps derived from reflection seismic interpretations. Spatiotemporal analysis of induced event locations reveals ongoing large scale fault reactivation in the field, and also suggests compaction of the gas reservoir as the major cause and water injection in the oil reservoir as the secondary cause for inducing seismicity in the field.Thirdly, event locations and interpretations are presented for a different set of induced seismicity data recorded by a deep-borehole network over an 11-month period at the same field. About 5400 events are located and analyzed, and detailed mapping of faults and fractures using the event hypocenters are presented.
(cont.) Patterns of seismicity also reveal faults and fracture systems previously unmapped by reflection seismic. While this dataset allows for much finer interpretation, the results between the two network data are found to be consistent and comparable.Finally, the double-difference relocation and tomography method is applied for event relocation and imaging of the reservoir. Better correlation of relocated events with faults is observed from application of this method to the surface-network events, and detailed velocity and structure images for the reservoir are obtained from application of tomography with the deep network events.
by Sudipta Sarkar.
Ph.D.

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Quick, Tyler James. "Evaluating Liquefaction Triggering Potential from Induced Seismicity in Oklahoma, Texas, and Kansas." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104061.

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Deep wastewater injection-induced seismicity has led to over a thousand magnitude (Mw) > 3 earthquakes and four Mw>5 earthquakes in Oklahoma, Texas, and Kansas (OTK) over the last ten years. Liquefaction observed following the 3 September 2016, Mw5.8 Pawnee, OK, induced earthquake raises concerns regarding the liquefaction risk posed by future induced earthquakes. The stress-based simplified liquefaction evaluation procedure is widely used to evaluate liquefaction potential. However, empirical aspects of this procedure were primarily developed for tectonic earthquakes in active shallow-crustal tectonic regimes (e.g., California). Consequently, due to differences in ground motion characteristics and regional geology, the depth-stress reduction factor (rd) and Magnitude Scaling Factor (MSF) relationships used in these variants may be unsuitable for use with induced earthquakes in OTK. This is because both rd, which accounts for the non-rigid soil profile response, and MSF, which accounts for shaking duration, are affected by ground motion and soil profile characteristics. The objective of this research is to develop and test a new liquefaction triggering model for use in assessing the regional liquefaction hazard in OTK from injection-induced earthquakes. This model incorporates induced seismicity-specific rd and MSF relationships. To assess model efficacy, the liquefaction potential is evaluated for several sites impacted by the 2016 Pawnee earthquake using the model developed herein, as well as several models commonly used to evaluate liquefaction potential for tectonic earthquakes. Estimates are then compared with field observations of liquefaction made following the Pawnee event. This analysis shows that, at most sites, the induced seismicity-specific model more accurately predicts liquefaction severity than do models developed for tectonic earthquakes, which tend to over-predict liquefaction severity. The liquefaction triggering model developed herein is also used to assess the minimum magnitude (Mmin) of induced earthquakes capable of triggering liquefaction. For sites capable of supporting structures, it is shown that Mmin = 5.0 is sufficient to fully capture liquefaction hazard from induced events in OTK. However, for extremely liquefaction-susceptible soil profiles that are potentially relevant to other infrastructure (e.g., pipelines and levees), consideration of Mmin as low as 4.0 may be required.
Doctor of Philosophy
Seismic activity caused by deep wastewater injection has caused over a thousand magnitude (Mw) > 3 earthquakes and four Mw>5 earthquakes in Oklahoma, Texas, and Kansas (OTK) over the last ten years. These events are referred to as induced earthquakes. Liquefaction observed following the 3 September 2016, Mw5.8 Pawnee, OK, induced earthquake raises concerns regarding the liquefaction risk posed by future induced earthquakes. The stress-based simplified liquefaction evaluation procedure is widely used to evaluate liquefaction potential. However, to date, variants of this procedure were developed primarily for natural, tectonic earthquakes in active seismic areas such as California. Due to differences between induced and tectonic earthquakes as well as regional geology, existing variants of the simplified procedure may be unsuitable for use with induced earthquakes in OTK. The objective of this research is to develop and test a new liquefaction triggering model for use in assessing the regional liquefaction hazard in OTK from injection-induced earthquakes. The model was developed using regional induced earthquake ground motion recordings and soil profiles. To assess model accuracy, liquefaction potential is assessed at several sites impacted by the 2016 Pawnee earthquake using the new model, as well as several models commonly used to evaluate liquefaction potential for tectonic earthquakes. Estimates are then compared with field observations of liquefaction made following the Pawnee event. This analysis shows that, at most sites, the induced seismicity-specific model more accurately predicts liquefaction severity than do models developed for tectonic earthquakes, which tend to over-predict liquefaction severity. The liquefaction triggering model developed herein is used to assess the minimum magnitude (Mmin) of induced earthquakes capable of triggering liquefaction. For sites capable of supporting structures, it is shown that Mmin = 5.0 is sufficient to fully capture liquefaction hazard from induced events in OTK. However, for extremely liquefaction-susceptible soil profiles potentially relevant to other infrastructure (e.g., pipelines and levees), Mmin as low as 4.0 may be required.

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Fadugba, Oluwaseun Idowu. "Detection of induced seismicity due to oil and gas extraction in the Northern Gulf of Mexico, USA." Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104632.

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Thesis advisor: John E. Ebel
Drilling operations and extraction of oil and gas (O&G) may lead to subsurface slumping or compression of sediments due to reduced vertical principal stress which may lead to small earthquakes at the drilling site. O&G extraction is common in the northern Gulf of Mexico (NGM) and only thirty-five earthquakes of magnitudes between 2.3 and 6.0 have been recorded in the area from 1974 to the present. The purpose of this research is to detect more earthquakes using stacks of seismic data from the Transportable USArray (TA) from 2011 to 2013, and determine the spatiotemporal relationship between the detected earthquakes and O&G extraction. Five new small offshore earthquakes, that may be associated with the offshore O&G production, have been detected in the data. Spatial correlation of the epicenters with offshore drilling sites shows that the earthquakes may be due to the O&G extraction
Thesis (MS) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences

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Wang, Pengyun. "A Statistical Approach for Assessing Seismic Transitions Associated with Fluid Injections." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/730.

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The wide application of fluid injection has caused a concern of the potential critical risk associated with induced seismicity. To help clarify the concern, this dissertation proposes a statistical approach for assessing seismic transitions associated with fluid injections by scientifically analyzing instrumental measures of seismic events. The assessment problem is challenging due to the uncertain effects of wastewater injections on regional seismicity, along with the limited availability of seismic and injection data. To overcome the challenge, three statistical methods are developed, with each being focused on a different aspect of the problem. Specifically, a statistical method is developed for early detection of induced seismicity, with the potential of allowing for site managers and regulators to act promptly and preparing communities for the increased seismic risk; the second method aims for addressing the further need of quantitatively assessing the transition of induced seismicity, which can reveal the underlying process of induced seismicity and provide data to support probabilistic seismic hazard analysis; and finally, the third method steps further to characterize the process of spatial distribution of induced seismicity, which accounts for spatial evolution of induced seismicity. All the proposed methods are built on the principles of Bayesian technique, which provides a flexible inference framework to incorporate domain expertise and data uncertainty. The effectiveness of the proposed methods is demonstrated using the earthquake dataset for the state of Oklahoma, which shows a promising result: the detection method is able to issue warning of induced seismicity well before the occurrence of severe consequences; the transition model provides a significantly better fit to the dataset than the classical model and sheds light on the underlying transition of induced seismicity in Oklahoma; and the spatio-temporal model provides a most comprehensive characterization of the dataset in terms of its spatial and temporal properties and is shown to have a much better short-term forecasting performance than the “naïve methods”. The proposed methods can be used in combination as a decision-making support tool to identify areas with increasing levels of seismic risk in a quantitative manner, supporting a comprehensive assessment to decide which risk-mitigation strategy should be recommended.

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Sadtler, Daniel Allan. "Passive Tomography to Image Stress Redistribution Prior to Failure on Berea Sandstone and Marcellus Shale for Caprock Integrity." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32402.

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A recent concern is the cause and effect of global climate change. Many institutions give credit for these changes to the increased levels of greenhouse gases in the atmosphere, in particular the increase in the amount of carbon dioxide present. There is a growing interest in carbon capture and storage (CCS) as a means to reduce the global impact of CO2 on the climate as a greenhouse gas. Carbon capture is the process of removing CO2 from the atmosphere as well as preventing it from entering the atmosphere by means of exhaust. The captured carbon is stored underground in reservoirs. These reservoirs have the storage space to handle the volume of CO2 injected as well as a caprock layer preventing the injection fluid from returning to the surface. Additionally, CO2 can be used for enhanced oil recovery (EOR). To monitor the injection sites used for the CO2 storage or EOR process, the integrity of the caprock as well as the surrounding rock formations are the locations of interest. Knowing when a joint or a fracture is going to slip is necessary to prevent major failures within geologic strata. It is necessary to prevent these slips from occurring to retain the integrity of the caprock, which is keeping the fluid within the reservoirs. Passive acoustic emissions monitoring was used to determine how effectively failure locations could be located in three unique tests. Coupled with double difference tomography, the failure of a Berea Sandstone sample and Marcellus Shale sample were calculated to determine how well the stress redistribution within the sample could be mapped using the recorded data. For the main indenter tests two samples were tested, a piece of Berea Sandstone and a piece of Marcellus Shale. The secondary test was a transform shear test using sandstone, and the third test for caprock upheaval test attempted to recreate the failure of caprock due to injection pressure. For all tests, the samples were monitored using acoustic emissions software until failure or it was deduced that the test would not produce failure. The secondary tests did not progress through the data analysis as far as the indentation tests, however valuable information was gathered from these tests. The shear test demonstrated the iii effectiveness of the passive acoustic emissions monitoring system to record shear failure. This test provides confidence in this technology to record and located events that are not occurring in compression. The caprock upheaval tests were not successful in causing failure in the caprock, however during the testing the passive acoustic emissions monitoring system was able record and locate events that occurred within the sample around the boundary on the reservoir. At the reservoir boundaries there was evidence of fluid flowing through the reservoir, and the events align with these locations. This positive result shows that the monitoring system is able to locate events induced by fluid injection. The results of these tests provide confidence in the passive acoustic emissions monitoring system to record accurate data for the caprock integrity monitoring. The tomograms created from the recorded data accurately imaged the areas of interest within the rock samples. From these results, passive acoustic emissions monitoring systems coupled with double difference tomography has proven capable of monitoring homogeneous samples within a laboratory environment. With further testing, this technology could possibly be a viable option for monitoring carbon sequestration sites.
Master of Science

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Hesseltine, Garth. "Micro- to Macro-Scale Structural and Lithological Architecture of Basal Nonconformities: Implications for Fluid Flow and Injection Induced Seismicity." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7497.

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Rising incidents of earthquakes caused by human activity in the United States, known as induced earthquakes, is a growing concern. Induced earthquakes may occur when fluid and/or wastewater is injected several kilometers beneath the Earth’s surface into sedimentary rocks. Fluids and pressures can migrate from the sedimentary rocks, which are typically friendlier to fluid flow, into underlying less friendlier crystalline rocks along fluid pathways weakening and possibly reactivating preexisting faults. Understanding potential fluid pathways and/or barriers from the sedimentary rocks to crystalline rocks is crucial. I investigate the structure, composition, and heterogeneity of rocks near the contact between the sedimentary and crystalline rocks, known as nonconformities, and highlight their possible role in the transmission of fluids and porefluid pressures into the crystalline basement. To characterize nonconformities, we examined outcrop analogs and drillcore of nonconformities in New Mexico, Colorado, and Michigan. Geochemical, structural, and hydrological techniques were used to analyze the nonconformities at microscopic to megascopic scales. The nonconformities observed in this study consist of variably deformed, weathered, and altered igneous and metamorphic crystalline basement overlain by sedimentary rocks cut by outcrop- and map-scale faults. The nonconformity at the New Mexico sites includes a clay-rich weathered horizon atop deformed and jointed crystalline basement. Heterogeneity observed in the fracture and joint networks within the crystalline basement contributes to permeability heterogeneity and anisotropy. The crystalline basement adjacent to the nonconformity at the Colorado site is relatively fresh and unweathered and overlain by low permeability sandstones. The nonconformity and underlying slates in the Michigan drillcore are overprinted by hydrothermal alteration and carbonate mineralization, which provides evidence of hydrological communication between sedimentary and crystalline rocks. The nonconformities display a range of structural, hydrological, and geochemical styles and characteristics which vary over relatively small spatial extents. The geological and hydrogeological histories and complexities of nonconformity analogs provide valuable information to understand how fluids, past, and present, interact with the contact. This study introduces some of the factors that may control fluid flow adjacent to nonconformities and their possible significance to the interplay of deformation, fluid flow, and induced seismicity.

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De, Simone Silvia. "Induced seismicity in enhanced geothermal systems : assessment of thermo-hydro-mechanical effects." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405890.

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Micro-seismicity, and especially felt seismicity, induced by Enhanced Geothermal Systems (EGS) operations is a matter of scientific interest, not only because of the related risks and concerns, but also because the correspondence between injection and seismic activity still remains unclear. The Thesis aims to deepen the understanding of the involved Thermo-Hydro-Mechanical (THM) processes, in order to explain and manage co- and post-injection seismicity. First, we investigate the HM coupling and its effects on pressure response. Fluids injection exerts a force over the aquifer that causes deformation. This implies that Specific Storage, which reflects the capacity of permeable media to deform, cannot be treated as a single parameter, like in classical groundwater hydrology, because deformation also depends on aquifer geometry and on surrounding formations, which constrain displacements. We demonstrate the non-local nature of storage (i.e., its dependence on the poroelastic response over the whole aquifer) by means of analytical solutions to the transient pressure response to injection into one-dimensional and cylindrical finite aquifers, while acknowledging HM coupling. We find that the pressure response is faster and much greater than predicted with traditional solutions. Second, we consider non-isothermal injection and compare the effects of HM and TM couplings. We present analytical expressions for long-term hydraulic and thermal stresses and displacements for unidirectional and radial geometries. To obtain them, we assume steady-state fluid flow and develop an easy-to-use solution to the transient heat transport problem. The solution is then used to illustrate the poroelastic and thermoelastic response and, in particular, the sensitivity of stresses to the outer mechanical boundary conditions. Third, we perform coupled HM and THM simulations of cold water injection in a fault-intact rock system, which allows us to analyze mechanical stability changes during injection in the vicinity of the well. Simulation results show that temperature drop induces a significant perturbation of stresses in the intact rock near the injection well. This perturbation is likely to induce seismicity around critically oriented fractures. HM simulations show that fracture stability depends on the orientation of the faults and on the initial stress tensor. Results show that TM effects dominate and could induce seismicity, when the largest confining stress acts perpendicular to a fracture. Finally, we investigate the mechanisms that may induce seismicity after the end of fluid injection into a deep geothermal system (post-injection seismicity). Apart from the direct impact of fluid pressure increase, we acknowledge thermal effects due to cooling and stress redistribution caused by shear slip along favorably oriented fractures during injection. The effect of these three processes are analyzed both separately and superimposed. We find that post-injection seismicity may occur on unfavorably oriented faults that were originally stable. During injection, such faults become destabilized by thermal and shear slip stress changes, but remain static by the superposition of the stabilizing effect of pressure forces. However, these fractures become unstable and fail when the pressure forcing dissipates shortly after injection stops abruptly, which suggests that a slow reduction in injection rate may alleviate post-injection seismicity.
La micro-sismicitat induïda per operacions relacionades amb els Sistemes Geotèrmics Estimulats ha originat un gran interès científic, no només pel risc i la preocupació que comporta, sinó també perquè la relació entre la injecció de fluids i l'activitat sísmica no s'entén completament. Aquesta tesi pretén avançar en la comprensió dels processos hidro-termo-mecànics (THM) que causen aquesta sismicitat, per poder explicar-la i gestionar-la. En primer lloc, hem investigat l'acoblament hidro-mecànic (HM) i el seu efecte sobre les pressions. En Hidrologia Subterrània clàssica l'emmagatzematge especifico expressa la capacitat de l'aqüífer de deformar-se després d'una variació de pressió. Malgrat això, la sobrepressió generada per la injecció exerceix una força que deforma tot l'aqüífer, depenent de la seva geometria i de les formacions adjacents. Per això, l'emmagatzematge no es pot expressar amb un sol paràmetre, sinó que depèn de la resposta poro-elàstica de tot l'aqüífer, per la qual cosa diem que l'emmagatzematge específic és "no-local", cosa que vam mostrar mitjançant solucions analítiques de la resposta transitòria al problema HM de la injecció en aqüífers de dimensió finita, amb geometria tant unidimensional com cilíndrica. Seguidament, hem considerat una injecció no isoterma i comparat els efectes de l'acoblament hidro-mecànic (HM) i termo-mecànic (TM). Hem obtingut expressions analítiques per a les tensions i els desplaçaments induïts a llarg termini per la pertorbació hidràulica i tèrmica, en el cas de dominis unidireccional i radial. Per a això, hem considerat flux estacionari i desenvolupat una solució analítica senzilla per al transport de calor en règim transitori, la qual cosa ens ha permès calcular la resposta poro i termo-elàstica i en particular la sensibilitat de les tensions a les condicions mecàniques en el contorn exterior. A continuació, hem desenvolupat simulacions HM i THM acoblades de la injecció d'aigua freda en un sistema format per una falla embeguda en una roca intacta, a fi d'analitzar les variacions de l'estabilitat mecànica durant la injecció. Les simulacions HM mostren que l'estabilitat de les fractures depèn de la seva orientació i del tensor de tensions inicial. Concloem que la reducció de temperatura provoca prop del pou una forta pertorbació de les tensions, que pot induir sismes en fractures orientades críticament, especialment quan la tensió màxima actua perpendicularment a la fractura. Finalment, hem estudiat els mecanismes que poden induir sismes quan s'atura la injecció de fluids en sistemes geotèrmics profunds (sismicitat post-injecció). A més de l'efecte directe de l'augment de la pressió, hem considerat l'efecte tèrmic a causa del refredament i la redistribució de tensions generada pel moviment de cisalla que ocorre durant la injecció en fractures favorablement orientades. Aquests efectes s'han analitzat tant per separat com superposats. Dels resultats podem deduir que la sismicitat post-injecció pot ocórrer al llarg de fractures que eren inicialment estables i es desestabilitzen durant la injecció, a causa de les tensions tèrmiques i a les induïdes per la cisalla, però es mantenen estables gràcies a les forces de pressió. Posteriorment, aquestes fractures trenquen quan s'interromp la injecció, ja que les pressions es dissipen ràpidament. Això suggereix que la sismicitat post-injecció pot atenuar-se amb una reducció lenta del cabal d'injecció.

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17

Gunasekera, Rashmin C. "Induced seismicity and environmental change at The Geysers geothermal area in California." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3817/.

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Intensive exploitation of the reservoir at The Geysers geothermal area, California, induces myriads of small-magnitude earthquakes that are monitored by a dense, permanent seismometer network that covers most of the reservoir. However, majority of the seismic stations, which belong to the UNOCAL network are poorly calibrated. Station polarities, and sensor orientations for the 8 three-component stations of this network were determined by using accurate focal mechanism solutions from a temporary network and using a simple method of observing the waveform from known earthquake locations. Using data from the UNOCAL network, tomographic inversions were performed for the three-dimensional Vp and Vp/Vs-ratio structure of the reservoir for February 1993, October 1996 and August 1998, adding to the inversions for April 1991 and December 1994 that had already been performed by other investigators. The extensive low -Vp/Vs anomaly known to characterise the reservoir grew progressively in strength from a maximum of 9% to a maximum of 12.4% at sea level during the seven-year study period. The anomaly growth is attributed to the depletion of pore liquid water in the reservoir and its replacement with steam. This causes Vp to decrease by increasing compressibility, and Vs to increase because of the reduction in pore pressure and the drying of argillaceous minerals, e.g., illite, which increases the shear modulus. All these effects serendipitously combine to lower the Vp/Vs ratio, resulting in an exceptionally strong overall effect that provides a convenient tool for monitoring reservoir depletion in the seismogenic zone. Variations in the separate Vp and Vs fields indicate that water depletion was the most important process in the central part of the exploited reservoir, and that pressure reduction and mineral drying were the dominant effects more northwesterly and southeasterly. Relative relocation of micro earthquakes was also performed using the same network. Four regions were studied. Although most multiplets relocated into tighter clusters and the reduction in the RMS of the relative relocations was good, further work is needed to substantiate these initial findings.

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18

Gonçalves, da Silva Bruno Miguel. "Fracturing processes and induced seismicity due to the hydraulic fracturing of rocks." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107063.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 449-458).
Hydraulic fracturing is a method used routinely in oil and gas exploitation and in engineered geothermal systems. While used frequently, there are aspects of hydraulic fracturing, such as the propagation of the newly-created fractures and interaction between natural and newly-created fractures, which are not well understood. Since data from field hydraulic stimulations may be difficult to obtain and interpret, laboratory testing and numerical modeling play a major role in understanding the hydraulically fracturing processes. A test setup was developed to simultaneously apply a vertical stress to rock specimens and a hydraulic pressure to pre-cut flaws with various geometries, leading to the initiation and propagation of new cracks. The test setup allowed one to obtain high-resolution and high-speed video images of the hydraulic fracturing processes and to monitor acoustic emissions in Barre granite specimens subjected to constant vertical stresses of 0 or 5 MPa. The imaging data were used to determine the mechanisms of development of the visible fractures produced during the tests. The acoustic emission data were used to estimate the mechanisms responsible for the development of micro-cracks. In order to understand the fracturing behavior of the hydraulically loaded rock specimens, particularly the effect of the ratio between the water pressure applied in the flaws (WP) and the vertical load applied to the specimen (VL), a finite element analysis was performed using the same loading conditions of the experiments. The experiments showed that most visible cracks observed were tensile and that the patterns of the hydraulic fractures produced were strongly dependent on the vertical load applied. They also showed that the water pressure necessary to propagate fractures is dependent on the vertical load and on the flaw geometry. The numerical analysis showed that the ratio WP/VL plays a crucial role in the magnitude and shape of the stress field around a flaw tip, and therefore in the location of tensile and shear fracture initiation. The study of micro-seismic events indicated that tensile and shear micro-cracks frequently developed before visible tensile cracks in the tests with no and 5 MPa of vertical load, respectively. The results presented improve the knowledge of the physical processes involved in the hydraulic fracturing of rocks.
by Bruno Miguel Gonçalves da Silva.
Ph. D.

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19

Sze, Edmond Kin-Man. "Induced seismicity analysis for reservoir characterization at a petroleum field in Oman." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33722.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005.
Includes bibliographical references.
This thesis presents the analysis and interpretation of passive seismic data collected in a 20-month monitoring period. The investigation is divided into four studies, each focusing on a different aspect of the seismic data to infer the reservoir properties. First, I applied three different methods (the iterative linearized, nonlinear grid-search, and double-difference methods) to relocate 405 microearthquakes that occurred between October 1999 and June 2001 in a producing field in Oman. A numerical technique is applied to "collapse" the relocated hypocenters and to find the simplest structural interpretation consistent with the data. Comparing the methods, the applicability of waveform correlation methods such as the double-difference in this case is limited by the relatively large number of events with dissimilar waveforms. Unlike the iterative linearized method, the nonlinear grid-search method gives the best results with the smallest average rms error of the absolute locations because it avoids the local minimum problem.
(cont.) The relocated hypocenters clearly delineate nearly vertical, northeast-southwest striking faults near the crest of the field, which is consistent with the graben fault system mapped by surface geologic surveys and reflection seismic interpretations. I also performed statistical tests to estimate location errors, and found that the station geometry is the major factor that limits the accuracy of focal depths. Secondly, this thesis presents a non-linear wavelet-based approach to linear waveform inversion of high-frequency seismograms for the estimation of a point source mechanism and its time function. For earthquake mechanism inversions, it is important to stabilize the problem by reducing the number of parameters to be determined. Commonly, overlapping isosceles triangles or boxcar functions are used for the parameterization of the moment tensor rate functions (MTRFs). Here, I develop a wavelet-based strategy that allows us to construct an adaptive, problem-dependent parameterization for the MTRFs employing fractional spline wavelets. Synthetic results demonstrate that the adaptive parameterization improves the numerical approximation to the model space and therefore, allows more accurate estimations of the MTRFs.
(cont.) The waveform inversion is performed in the wavelet domain and leads to a multiresolution sparse matrix representation of the inverse problem. At each resolution level a regularized least-squares solution is obtained using the conjugate gradient method. The wavelet-based waveform inversion method has been applied successfully in three real- data examples: the April 22, 2002 Au Sable Forks, New York earthquake, the September 3, 2002 Yorba Linda, California earthquakes, and 11 M>1 microearthquakes in a producing field in Oman. In the Oman field, the dominant styles of focal mechanism are left-lateral strike-slip for events with focal depths less than 1.5 km, and dip-slip along an obliquely trending fault for those with focal depths greater than 2.0 km. Thirdly, the covariance matrix method of shear-wave splitting analysis is presented. Different from conventional methods that usually analyze only two horizontal components, this method processes all three components of the seismogram simultaneously, allowing not only orientation but also dip information of fractures to be resolved. Synthetic test results show that this method is stable even for high noise level.
(cont.) The method is applied to the Oman microearthquake records that display distinctive shear-wave splitting and polarization directions. From the polarizations, I estimate the predominant subsurface fracture directions and dipping angles. From the time delays of the split wave I determine the fracture density distributions in the reservoir. Finally, I examine the spatio-temporal characteristics of the microseismicity in the producing reservoir. The frequency-magnitude distribution measured by the b-value is determined using the maximum likelihood method. I found that b-values are higher for events below the deeper Shuaiba oil reservoir than those above. Also, the feasibility of monitoring the temporal change of b-values is demonstrated. The analysis of production and injection well data shows that seismicity event rates in the field all strongly correlated with gas production from the shallower Natih Formation. Microseismicity, focal mechanisms, GPS analysis, and production / injection well data all suggest the NE- SW bounding graben fault system responds elastically to the gas-production-induced stresses. Normal faulting is enhanced in the reservoirs by the compaction related stresses acting on the graben fault system.
by Edmond Kin-Man Sze.
Ph.D.

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Andersen, Lindsay Marguerite. "A relative moment tensor inversion technique applied to seismicity induced by mining." Thesis, University of the Witwatersrand, Johannesburg, 2001. http://hdl.handle.net/10539/20887.

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Three hybrid moment tensor inversion methods were developed for seismic sources originating from a small source region. These techniques attempt to compensate for various types of systematic error (or noise) that influence seismograms recorded in the underground environment in order to achieve an accurate and robust measure of the seismic moment tensor. The term 'hybrid' was used to distinguish between the relative method proposed by Dahm (1995) and the methods developed in this thesis. The hybrid methods were essentially weighting schemes designed to enhance the accuracy of the computed moment tensors by decreasing the influence of any low quality observations, to damp (or amplify) any signals that have been overestimated (or underestimated) due to local site effects, and to correct for raypath focussing or defocussing that results from inhomogeneities in the rockmass. The weighting or correction applied to a particular observation was derived from the residuals determined when observed data were compared with corresponding theoretical data (for a particular geophone site, sensor orientation and wave phase) and were calculated using a cluster of events rather than a single event. The first and second weighting schemes were indirectly related to the mean and the median of the residuals where the residuals were defined as the ratio of the theoretical to observed data. In the third scheme, the residuals were defined as the difference between the observed and theoretical data and the weights were based on the distance of a data point (measured in standard deviations) from the mean residual. In each of the weighting schemes, the correction was applied iteratively until the standard error of the least-squares solution (normalised to the scalar seismic moment) was a minimum. The schemes were non-linear because new weights were calculated for each iteration. A number of stability tests using synthetic data were carried out to quantify the source resolving capabilities of the hybrid methods under various extreme conditions. The synthetic events were pure double-couple sources having identical fault-plane orientations, and differing only in rake. This similarity in the mechanisms was chosen because the waveforms of tightly grouped events recorded underground often show high degrees of similarity. For each test, the results computed using the three hybrid methods were compared with one another and with those computed using the single event, absolute method and two relative methods (with and without a reference mechanism). In the noise-free situation, it was found that the relative method without reference mechanism showed the highest resolution of mechanisms, provided that the coverage of the focal sphere was not too sparse (> 3 stations). The hybrid method using a median correction was found to be the most robust of all the methods tested in the most extreme case of poor coverage (2 stations) of the focal sphere. When increasing levels of pseudo-random noise were applied to the data, the absolute moment tensor inversion method, the hybrid method using a median correction, and the hybrid method using a weighted mean correction all showed similar robustness and stability in extreme configurations concerning network coverage of the focal sphere and noise level. When increasing levels of systematic noise were added to the data, the hybrid methods using a median correction and weighted mean correction were found to exhibit similar robustness and stability in extreme configurations concerning network coverage of the focal sphere and systematic noise. In all situations investigated, these two hybrid methods outperformed the relative and absolute methods. The hybrid moment tensor inversion methods using a median and weighted mean correction were applied to a cluster of 14 events, having remarkably similar waveforms, recorded at Oryx Gold Mine. For comparative purposes, the absolute method was also applied. The inputs to the inversion methods consisted of the spectral plateaus of both P- and S-waves at frequencies below the comer frequency of the time-integrated displacement traces. The polarities of dominant motion were used as an additional constraint and were determined from cross-correlation of observed with synthetic P- or S-waves. The solutions computed using the hybrid moment tensor inversion using a median correction displayed a distinct improvement after the iterative residual correction procedure was applied. The radiation patterns and faultplane solutions showed a high degree of similarity, and are probably more accurate reflections of reality than those computed using the absolute moment tensor inversion methods. These observations are very encouraging and point towards the method's potential for use as a standard processing tool for mine seismicity. The implications of this work are a better understanding of the focal mechanisms of seismic events induced by mining activities, ultimately leading to improved safety underground.

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Warren, Justin Cable. "A Study of Mine-Related Seismicity in a Deep Longwall Coal Mine." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76766.

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This study involves seismic monitoring of a deep coal mine. The purpose is to examine the processes responsible for induced seismicity. A seismic network consisting of five three-component short-period seismometers located above the mine recorded the seismic data. The events discussed here occurred from March 1, 2009 until April 7, 2011 during the mining of three longwall panels and the data was telemetered to Blacksburg, Virginia. A correlation equation was developed to relate local magnitude estimated by automatic data processing software in near real-time to seismic moment for well-recorded events. Local magnitude is a relative measure of relative size for a suite of earthquakes, while seismic moment is an objective measure of the actual physical size. Using the calculated seismic moments, we calculated "moment magnitudes" (Mw) for all events, which allowed us to do further studies in terms of their absolute size as a function of both time and space. The results indicate that there are two distinct classes of seismic events at the mine. The first class consists of small (M<=0) earthquakes recorded near the moving mine face. The second class of seismicity occurs in the mined-out "gob" area of the longwall panel at a greater distance behind the moving face. Their occurrence and relation to the mining history, depth of overburden and geology of the roof rocks is a significant interest. Results show that thick overburden due to elevated topography has a positive correlation with the number of seismic events but is not the only controlling factor; other factors include gob size and geological variability. Another important observation is the high seismic attenuation of the rock mass above the mine. This appears to be the result of the fracturing and caving processes associated with the creation of the gob and the resulting subsidence of the ground surface.
Master of Science

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22

Hudyma, Martin Raymond. "Analysis and interpretation of clusters of seismic events in mines." University of Western Australia. School of Civil and Resource Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0054.

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Spatial clustering of seismic events in mines has been widely reported in literature. Despite obvious visual correlations between spatial clusters of seismic events and geomechanical structures in mines (such as pillars, dykes and faults), very limited research has been undertaken to utilise this information to filter seismic data. A linkage between spatial seismic event clusters and discrete rockmass failure mechanisms is tenuous and not well established using current seismic analysis techniques. A seismic event clustering methodology is proposed. The first component of the methodology uses a complete-linkage (CLINK) clustering routine to identify relatively compact clusters of seismic events. The CLINK clusters are then subjected to a singlelink clustering process, which uses spatial location and seismic source parameters as similarity measures. The resultant

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Rossi, Camilla <1992&gt. "Discrimination between natural and induced seismicity in the Hengill geothermal area, SW Iceland." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9760/3/rossi_camilla_tesi.pdf.

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The Hengill area is a complex tectonic and geothermal site, located at the triple junction between the Reykjanes Peninsula (RP), the Western Volcanic Zone (WVZ), and the South Iceland Seismic Zone (SISZ). Geothermal systems in the vicinity of the Hengill volcano are exploited for electrical power and heat production, and today the two largest operating geothermal power plants are located at the Nesjavellir and the Hellisheiði. The region is seismically highly active with several thousand earthquakes located yearly, and whose origin may be either natural or anthropogenic. The thesis focuses on the analysis and investigation of the

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24

Abolfazlzadeh, Yousef. "APPLICATION OF SEISMIC MONITORING IN CAVING MINES." Thesis, Laurentian University of Sudbury, 2013. https://zone.biblio.laurentian.ca/dspace/handle/10219/2110.

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Comprehensive and reliable seismic analysis techniques can aid in achieving successful inference of rockmass behaviour in different stages of the caving process. This case study is based on field data from Telfer sublevel caving mine in Western Australia. A seismic monitoring database was collected during cave progression and breaking into an open pit 550 m above the first caving lift. Five seismic analyses were used for interpreting the seismic events. Interpretation of the seismic data identifies the main effects of the geological features on the rockmass behaviour and the cave evolution. Three spatial zones and four important time periods are defined through seismic data analysis. This thesis also investigates correlations between the seismic event rate, the rate of the seismogenic zone migration, mucking rate, Apparent Stress History, Cumulative Apparent Volume rate and cave behaviour, in order to determine failure mechanisms that control cave evolution at Telfer Gold mine.

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25

Grigoli, Francesco. "Automated seismic event location by waveform coherence analysis." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7032/.

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Automated location of seismic events is a very important task in microseismic monitoring operations as well for local and regional seismic monitoring. Since microseismic records are generally characterised by low signal-to-noise ratio, such methods are requested to be noise robust and sufficiently accurate. Most of the standard automated location routines are based on the automated picking, identification and association of the first arrivals of P and S waves and on the minimization of the residuals between theoretical and observed arrival times of the considered seismic phases. Although current methods can accurately pick P onsets, the automatic picking of the S onset is still problematic, especially when the P coda overlaps the S wave onset. In this thesis I developed a picking free automated method based on the Short-Term-Average/Long-Term-Average (STA/LTA) traces at different stations as observed data. I used the STA/LTA of several characteristic functions in order to increase the sensitiveness to the P wave and the S waves. For the P phases we use the STA/LTA traces of the vertical energy function, while for the S phases, we use the STA/LTA traces of the horizontal energy trace and then a more optimized characteristic function which is obtained using the principal component analysis technique. The orientation of the horizontal components can be retrieved by robust and linear approach of waveform comparison between stations within a network using seismic sources outside the network (chapter 2). To locate the seismic event, we scan the space of possible hypocentral locations and origin times, and stack the STA/LTA traces along the theoretical arrival time surface for both P and S phases. Iterating this procedure on a three-dimensional grid we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatial and temporal coordinates of the seismic event. Location uncertainties are then estimated by perturbing the STA/LTA parameters (i.e the length of both long and short time windows) and relocating each event several times. In order to test the location method I firstly applied it to a set of 200 synthetic events. Then we applied it to two different real datasets. A first one related to mining induced microseismicity in a coal mine in the northern Germany (chapter 3). In this case we successfully located 391 microseismic event with magnitude range between 0.5 and 2.0 Ml. To further validate the location method I compared the retrieved locations with those obtained by manual picking procedure. The second dataset consist in a pilot application performed in the Campania-Lucania region (southern Italy) using a 33 stations seismic network (Irpinia Seismic Network) with an aperture of about 150 km (chapter 4). We located 196 crustal earthquakes (depth < 20 km) with magnitude range 1.1 < Ml < 2.7. A subset of these locations were compared with accurate locations retrieved by a manual location procedure based on the use of a double difference technique. In both cases results indicate good agreement with manual locations. Moreover, the waveform stacking location method results noise robust and performs better than classical location methods based on the automatic picking of the P and S waves first arrivals.
Die automatische Lokalisierung seismischer Ereignisse ist eine wichtige Aufgabe, sowohl im Bereich des Mikroseismischen Monitorings im Bergbau und von Untegrund Aktivitäten, wie auch für die lokale und regionale Überwachung von natürlichen Erdbeben. Da mikroseismische Datensätze häufig ein schlechtes Signal-Rausch-Verhältnis haben müssen die Lokalisierungsmethoden robust gegen Rauschsignale und trotzdem hinreichend genau sein. Aufgrund der in der Regel sehr hochfrequent aufgezeichneten Messreihen und der dadurch sehr umfangreichen Datensätze sind automatische Auswertungen erstrebenswert. Solche Methoden benutzen in der Regel automatisch gepickte und den P und S Phasen zugeordnete Ersteinsätze und Minimieren die Summe der quadratischen Zeitdifferenz zwischen den beobachteten und theoretischen Einsatzzeiten. Obgleich das automatische Picken der P Phase in der Regel sehr genau möglich ist, hat man beim Picken der S Phasen häufig Probleme, z.B. wenn die Coda der P Phase sehr lang ist und in den Bereich der S Phase hineinreicht. In dieser Doktorarbeit wird eine Methode vollautomatische, Wellenform-basierte Lokalisierungsmethode entwickelt, die Funktionen des Verhältnisses "Short Term Average / Long Term Average" (STA/LTA) verwendet und keine Pickzeiten invertiert. Die STA/LTA charakteristische Funktion wurde für unterschiedliche Wellenform Attribute getestet, um die Empfindlichkeit für P und S Phasen zu erhöhen. Für die P Phase wird die STA/LTA Funktion für die Energie der Vertikalkomponente der Bodenbewegung benutzt, wohingegen für die S Phase entweder die Energie der horizontalen Partikelbewegung oder eine optimierte Funktion auf Basis der Eigenwertzerlegung benutzt wird. Um die Ereignisse zu lokalisieren wird eine Gittersuche über alle möglichen Untergrundlokalisierungen durchgeführt. Für jeden räumlichen und zeitlichen Gitterpunkt werden die charakteristischen Funktionen entlang der theoretischen Einsatzkurve aufsummiert. Als Ergebnis erhält man eine 4-dimensionale Matrix über Ort und Zeit des Ereignisses, deren Maxima die wahrscheinlichsten Lokalisierungen darstellen. Um die Unsicherheiten der Lokalisierung abzuschätzen wurden die Parameter der STA/LTA Funktionen willkürlich verändert und das Ereignis relokalisiert. Die Punktwolke aller möglichen Lokalisierungen gibt ein Maß für die Unsicherheit des Ergebnisses. Die neu entwickelte Methode wurde an einem synthetischen Datensatz von 200 Ereignissen getestet und für zwei beobachtete Datensätze demonstriert. Der erste davon betrifft induzierte Seismizität in einem Kohlebergbau in Norddeutschland. Es wurden 391 Mikrobeben mit Magnituden zwischen Ml 0.5 und 2.0 erfolgreich lokalisiert und durch Vergleich mit manuell ausgewerteten Lokalisierungen verifziert.Der zweite Datensatz stammt von einem Anwednung auf des Regionale Überwachungsnetz in der Region Campania-Lucania (Süditalien) mit 33 seismischen Stationen und einer Apertur von etwa 150 km. Wir konnten 196 Erdbeben mit Tiefen < 20 km und Magnituden zwischen Ml 1.1 und 2.7 lokalisieren. Eine Untergruppe der eigenen Lokalisierungen wurde mit den Lokalisierungen einer Standard Lokalisierung sowie einer hochgenauen Relativlokalisierung verglichen. In beiden Fällen ist die Übereinstimmung mit den manuellen Lokalisierungen groß. Außerdem finden wir, dass die Wellenform Summations Lokalisierung ronbust gegen Rauschen ist und bessere Ergebnisse liefert als die Standard Lokalisierung, die auf dem automatischen Picken von Ersteinsatzzeiten alleine basiert.

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26

Ghaychi, Afrouz Setareh. "Seismic Wave Velocity Variations in Deep Hard Rock Underground Mines by Passive Seismic Tomography." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97890.

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Mining engineers are tasked with ensuring that underground mining operations be both safe and efficiently productive. Induced stress in deep mines has a significant role in the stability of the underground mines and hence the safety of the mining workplace because the behavior of the rock mass associated with mining-induced seismicity is poorly-understood. Passive seismic tomography is a tool with which the performance of a rock mass can be monitored in a timely manner. Using the tool of passive seismic tomography, the advance rate of operation and mining designs can be updated considering the induced stress level in the abutting rock. Most of our current understanding of rock mass behavior associated with mining-induced seismicity comes from numerical modeling and a limited set of case studies. Therefore, it is critical to continuously monitor the rock mass performance under induced stress. Underground stress changes directly influence the seismic wave velocity of the rock mass, which can be measured by passive seismic tomography. The precise rock mass seismicity can be modeled based on the data recorded by seismic sensors such as geophones of an in-mine microseismic system. The seismic velocity of rock mass, which refers to the propagated P-wave velocity, varies associated with the occurrence of major seismic events (defined as having a local moment magnitude between 2 to 4). Seismic velocity changes in affected areas can be measured before and after a major seismic event in order to determine the highly stressed zones. This study evaluates the seismic velocity trends associated with five major seismic events with moment magnitude of 1.4 at a deep narrow-vein mine in order to recognize reasonable patterns correlated to induced stress redistribution. This pattern may allow recognizing areas and times which are prone to occurrence of a major seismic event and helpful in taking appropriate actions in order to mitigate the risk such as evacuation of the area in abrupt cases and changing the aggressive mine plans in gradual cases. In other words, the high stress zones can be distinguished at their early stage and correspondingly optimizing the mining practices to prevent progression of high stress zones which can be ended to a rock failure. For this purpose a block cave mine was synthetically modeled and numerically analyzed in order to evaluate the capability of the passive seismic tomography in determining the induced stress changes through seismic velocity measurement in block cave mines. Next the same method is used for a narrow vein mine as a case study to determine the velocity patterns corresponding to each major seismic event.
Doctor of Philosophy
Mining activities unbalance the stress distribution underground, which is called mining induced stress. The stability of the underground mines is jeopardized due to accumulation of induced stress thus it is critical for the safety of the miners to prevent excessive induced stress accumulation. Hence it is important to continuously monitor the rock mass performance under the induced stress which can form cracks or slide along the existing discontinuities in rock mass. Cracking or sliding releases energy as the source of the seismic wave propagation in underground rocks, known as a seismic event. The velocity of seismic wave propagation can be recorded and monitored by installing seismic sensors such as geophones underground. The seismic events are similar to earthquakes but on a much smaller scale. The strength of seismic events is measured on a scale of moment magnitude. The strongest earthquakes in the world are around magnitude 9, most destructive earthquakes are magnitude 7 or higher, and earthquakes below magnitude 5 generally do not cause significant damage. The moment magnitude of mining induced seismic events is typically less than 3. In order to monitor mining induced stress variations, the propagated seismic wave velocity in rock mass is measured by a series of mathematical computations on recorded seismic waves called passive seismic tomography, which is similar to the medical CT-scan machine. Seismic wave velocity is like the velocity of the vibrating particles of rock due to the released energy from a seismic event. This study proposes to investigate trends of seismic velocity variations before and after each seismic event. The areas which are highly stressed have higher seismic velocities compared to the average seismic velocity of the entire area. Therefore, early recognition of highly stressed zones, based on the seismic velocity amount prior the occurrence of major seismic events, will be helpful to apply optimization of mining practices to prevent progression of high stress zones which can be ended to rock failures. For this purpose, time-dependent seismic velocity of a synthetic mine was compared to its stress numerically. Then, the seismic data of a narrow vein mine is evaluated to determine the seismic velocity trends prior to the occurrence of at least five major seismic events as the case study.

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27

Cuccio, Laura. "Geological Characterization of Precambrian Nonconformities: Implications for Injection-Induced Seismicity in the Midcontinent United States." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6889.

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The midcontinent United States, a region which typically does not experience many earthquakes, has experienced a significant increase in the number of earthquakes over the last decade. This increase in earthquake activity has been linked to wastewater injection, a process in which large volumes of wastewater from oil and gas extraction are injected into deep (2-3 km), high-permeability sedimentary rocks, near low-permeability Precambrian (>540-million-year-old) crystalline ‘basement’ rocks. The contact between these two rock types is referred to as the Precambrian nonconformity. Injection-induced earthquakes occur on or near basement-hosted faults due to an increase in pore fluid pressures, which implies that there may be a hydrological connection between the basement-hosted faults and the injection point. We hypothesize that the Precambrian nonconformity greatly influences this hydrological connection. We investigate the geologic properties of Precambrian nonconformity zone outcrop and core analogs to examine how the geology of the nonconformity zone controls fluid flow. Methods include mapping of geological materials and deformation structures (faults and fractures), mineralogical analysis, and geochemical analysis. These data sets allow us to infer the nature of fluid flow in the past, and make predictions about fluid flow in the future. In addition, this information is used to inform hydrological models, improving the ability to predict earthquakes due to wastewater injection. We identify three main geological scenarios that are likely to be encountered at the nonconformity. These are: 1) basal conglomerate, 2) weathered/altered horizon, and 3) mineralized contacts. These scenarios, or combinations of these scenarios, may be fractured or faulted, resulting in a variety of hydrological implications. The permeability of basal conglomerates and weathered horizons at the contact depends on the textures and minerals that are present. Regolith, clast-supported granitic wash, or poorly cemented conglomeratic horizons, may act as high permeability conduits, whereas a clay-rich grus or granitic wash, or tightly cemented conglomerate, may act as low permeability barriers. Mineralized contacts may act as low permeability barriers due to a reduction of pore space. The mineralized contact shows that the introduction of warm brines by modern injection may result in mineralization or chemical weathering, dynamically affecting permeability over time depending on the mineralogy of the host rock and chemical composition of the injected brine.

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28

Holtkamp, Stephen Gregg. "NEW METHODS FOR DETECTING EARTHQUAKE SWARMS AND TRANSIENT MOTION TO CHARACTERIZE HOW FAULTS SLIP." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1369741772.

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29

Olbert, Kai [Verfasser]. "Automatic processing of induced seismicity at the geothermal reservoirs Landau and Insheim / Kai Olbert." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/114359522X/34.

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30

Zangeneh, Neda. "Numerical simulation of hydraulic fracture, stress shadow effects and induced seismicity in jointed rock." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44779.

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Hydraulic fracturing provides a means to optimize shale gas completions by enhancing the permeability of what is otherwise very tight rock. However, the coupled nature of the processes involved (e.g., thermo-hydro-mechanical-chemical), interlinked with geological variability and uncertainty, makes it extremely difficult to fully predict the spatial and temporal evolution of the hydrofrac and surrounding invaded zone. Numerical design tools have been developed to contend with this complexity, but these have largely focused on the mechanics of brittle fracture propagation at the expense of making simplifying assumptions of the host geology within which the hydraulic fracture is propagating, namely treating it as a linear elastic continuum. In contrast, the reservoir rock conditions are much more complex. Present are natural discontinuities, including bedding planes, joints, shears and faults superimposed by the in-situ stress field. The natural discontinuities under the applied in-situ stress have the potential to either enhance or diminish the effectiveness of the hydraulic fracturing treatment and subsequent hydrocarbon production. Improved understanding of the interactions between the hydraulic fracture and natural fractures under the stress field would allow designers and operators to achieve more effective hydraulic fracturing stimulation treatments in unconventional reservoirs. To better account for the presence of natural discontinuities in shale gas reservoirs, this thesis investigates the use of the 2-D commercial distinct-element code UDECTM (Itasca Consulting Group, 1999) to simulate the response of a jointed rock mass subjected to static loading and hydraulic injection. The numerical models are developed to illustrate some important concepts of hydraulic fracturing such as the effect of natural fractures in fracture connectivity, effects of stress shadowing in multiple horizontal well completion, and the effect of fluid injection in induced seismicity, so they can be used to qualitatively evaluate the effects of the in-situ environment on the design and the consequences of the design on the in-situ environment.

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31

Collins, David Stephen. "Excavation induced seismicity in granite rock : a case study at the underground research laboratory, Canada." Thesis, Keele University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389605.

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This study presents a detailed investigation into the microseismic response of a rockmass being excavated in a high stress environment. AECL's Underground Research Laboratory, Manitoba, provided a unique opportunity to non-invasively monitor a tunnel excavation with a 3D microseismic array. The 46 m long cylindrical Mine-by tunnel was excavated at 420 m depth predominantly using a non-blasting method, therefore the damage zone and crack initiation is primarily due to the effect of stress redistribution and concentration following each excavation increment. Both manual and automated source parameter processing techniques are contrasted and used on the data set of over 20000 microseismic events of magnitude, MW =-1.5 to - 4.5. The relatively homogeneous and unfractured nature of the rockmass allowed the validity of fundamental spectral models to be tested. The seismicity is found to extend 1.0 m into the roof and floor regions of the tunnel and 0.8 m ahead of the tunnel face. Spatial and temporal trends in the source parameters are used to compare the seismic response of the two rock types present along the tunnel, namely granite and granodiorite. Seismicity starts earlier and occurs over a shorter time interval in the granite. Additionally, a late second phase of seismicity is found to occur in the granodiorite with these events having a similar magnitude to those at the excavation face. These trends, due to petrofabric and geotechnical differences in the two rock types, are important for safety reasons and mine design. The excellent sensor focal sphere coverage enabled the production of well constrained source mechanism solutions using both first motions and moment tensor analysis methods, and allowed source types to be contrasted with spectral parameters. Seismicity ahead of the tunnel face is predominantly deviatoric and it is concluded that this source type is resulting from movement on face parallel tensile cracks that formed early during the tunnel excavation

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32

Do, Nascimento Aderson F. "The role of pore pressure diffusion in a reservoir-induced seismicity site in NE Brazil." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13663.

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From August 1994 until May 1997, a network of 8 three-component digital seismographs operated at the Açu reservoir. A detailed analysis of this data forms the first part of this thesis. The earthquake locations revealed remarkably well-defined NE trending fault structures beneath the reservoir due to the simple seismic-wave velocity structure of the area. This digital data is shown here to be very suitable for focal mechanism determination and also to investigate seismic anisotropy in the area. This is possible due to the low attenuation of the seismic waves and good signal-to-noise ratio in the seismograms provided by the crystalline rocks of the area. The focal mechanism determination and the shear-wave study of this seismicity confirm that the area is in E-W compression and also that the shear-wave splitting is controlled by the seismic anisotropy associated with the Precambrian foliation. Moreover, this study shows that the seismicity migrates between different faults and within individual faults over different time periods. To investigate this behaviour and relate it to changing water levels in the reservoir and the resulting groundwater flow beneath, a fully three-dimensional groundwater flow code (PARADIGM) is used. PARADIGM is employed to simulate the pressure field in both the rock matrix and an idealised fault geometry. This flow modelling forms the second major component of this thesis. The significance of my approach is that I explicitly consider the physical meaning of hydraulic conductivity and storativity and their impact on fluid flow. In this model, both realistic information on the hydrogeological regime of the area and measurements of real fault zone hydraulic properties are included. The combination of the spatio-temporal analysis of the seismic activity and the numerical simulations carried out in PARADIGM provide new insights into the mechanism that causes the migratory behaviour.

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33

Needham, Daniel L. "Failure of asperities by hydraulically induced fatigue: a model for the generation of intraplate seismicity." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/43826.

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A model is proposed in which intraplate earthquakes are triggered by the tensile failure of asperities by subcritical crack growth. The principle subcritical crack growth mechanism is fatigue driven by cyclic tensile stresses within an asperity. Cyclic stresses result from cyclic pore pressure variations which propagate from the Earth's surface because of annual variations in the height of the water table. Asperities are postulated to be porous and permeable masses of saturated host rock hydrologically connected to fluids within an open fracture. Porosity and permeability within asperities are assumed to be due to microcracks within the rock matrix. Tensile stresses within an asperity are due partly to mechanical loads, but pore pressure is the primary Inechanism by which tension is developed and fatigue operates primarily in tension. Fatigue crack growth is enhanced by chemical subcritical crack growth mechanisms such as stress corrosion and these mechatusms are proposed to act in unison. Faulting may be initiated when a population of asperities is either driven to failure by these mechanisms alone or when it is weakened to the point at which it is vulnerable to small applied stresses. Numerical modeling of the interaction of pore pressures and stresses within asperities indicates that a small transient increase of pore pressure on the order of a fraction of a megapascal will increase the tensile stresses within an asperity by a fraction of a megapascal. Consequently, it may be possible for a small increase in pore pressure, due to elevated water table levels, to trigger asperity failure and result in seismicity.
Master of Science

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34

Warnana, Dwa Desa. "Rainwater infiltration and seismicity induced slope stability on residual soil using resistivity and microtremor measurements." Paris 6, 2013. http://www.theses.fr/2013PA066701.

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On évalue dans ce travail, en saison sèche comme en saison humide, la stabilité des pentes face à l’infiltration de la pluie et à l’activité sismique. Deux méthodes sont utilisées : la mesure de la résistivité électrique et celle des micro-trémors. Elles ont été mise en œuvre à Kemuning Lor Arjasa, Jember et Sumber Aji, Batu Malang. Les paramètres géotechniques et la résistivité des sols sont aussi analysés au laboratoire. Les données ainsi acquises, appuyées sur les modèles pétro-physiques, ont permis de proposer une interprétation quantitative de la structure du sous-sol. La mesure des micro-trémors est utilisée pour mieux comprendre les effets des tremblements de terre, définir des périodes propres des sites et localiser les pics d’amplitude (méthode du rapport déplacement horizontal sur déplacement vertical). On a pu ainsi proposer un indice de vulnérabilité et un déplacement en cisaillement. Les effets de la teneur en eau, de la cohésion, du poids spécifique et de l’angle de friction sur la résistivité électrique ont été précisés et un facteur empirique de sécurité a été déterminé et appliqué au suivi de résistivité en 2D en chaque lieu A Jember la pente est critique en saison humide. L’instabilité de pente induite par les séismes a pu être évaluée à partir de l’indice de vulnérabilité, elle est plus grande en saison humide qu’en saison sèche
This study aims to assess in the dry and rainy seasons the stability of slopes due to rain water infiltration and seismicity using resistivity and micro-tremor methods in Kemuning Lor Arjasa, Jember and Sumber Aji, Batu Malang. Geotechnical parameters and resistivity measurements in laboratory had also been carried out. A more detailed subsurface image deriving resistivity is verified to obtain quantitatively interpretation using geotechnical measurements and laboratory data as well as a petro-physical relation constitutive model. Microtremor measurements are used to better understand the soil effect induced by earthquakes. Hence, site period and peak amplitude is estimated from horizontal to vertical spectral ratio (HVSR) at study site. Finally, the slope stability that depends on soil vulnerability index and shear strain is able to calculate. The effects of moisture content, cohesion, unit weight, and friction angle on soil resistivity were determined. An empirical safety factor equation based on the rainwater infiltration-resistivity interaction and slope angles were determined and applied to 2-D resistivity monitoring in each location. It had been found that Jember slope was critical in the rainy season. The earthquake induced slope stability is assessed using the calculation of the soil vulnerability index and shear strain from microtremor measurements. The earthquake induced slope stability in the rainy season is found to be more vulnerable than in the dry season

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35

Konzen, Graydon Leo. "Regional-Scale Impacts of Fluid Composition and Geologic Structure for Injection-Induced Seismicity in the Southern U.S. Midcontinent." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99107.

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Over the last decade, an increase in earthquake occurrence in Oklahoma and Kansas has been linked to oilfield wastewater injection disposal, particularly into the regionally underpressured Arbuckle Group. The Arbuckle is hydraulically connected to Precambrian basement through an extensive fracture system, which transmits pressure perturbations from wastewater injections to seismogenic depths. Previous studies have convincingly attributed induced seismicity to pore pressure diffusion and solid elastic stressing, both resulting from fluid waste injection. Recent work adds to the physical understanding of injection-induced seismicity by demonstrating that the density differential between injection fluids and formation brines may also drive fluid pressure into the seismogenic basement. In this thesis, variable density groundwater flow is modeled in a numerical simulation comprising parts of the Anadarko Basin, the Anadarko Shelf, the Cherokee Platform, and the Nemaha Fault Zone as well as injection data from 2006-2018. Results show buoyancy forces interacting with regional stratigraphic dip to force density-driven pressure transients into the deep Anadarko Basin, aligning with previously unexplained earthquakes in that region.
Master of Science
Increased earthquake activity in Oklahoma and Kansas over the last decade is linked waste disposal related to hydrofracking. Oil and gas produced in the fracking process is often mixed with large amounts of water that is too salty to be used for public or industrial purposes, thus this water is disposed of via injection into deep rock layers in the upper portion of the Earth's interior, or crust. This injection disturbs the crust to trigger earthquakes where none have been historically observed. Previous studies examining this phenomenon assume that the rock layers of the crust lie flat and level; simplify the nature of major faults, or cracks, in the crust; and do not consider differences in water chemistry between injected water and water that already occupies the crust. The study developed in this thesis considers the effect of these three factors with regard to how they influence the extent of the linkage between waste water injection and earthquakes in Oklahoma and Kansas.

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36

Kinnaert, Xavier. "Data processing of induced seismicity : estimation of errors and of their impact on geothermal reservoir models." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH013/document.

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La localisation de séismes induits ainsi que les mécanismes au foyer associés sont des outils fréquemment utilisés afin, entre autres, d’imager la structure d’un réservoir. Cette thèse présente une technique permettant de quantifier les erreurs associées à ces deux paramètres. Par cette méthode, incertitudes et imprécisions sont distinguées. La méthode a été appliquée aux sites de Soultz et de Rittershoffen pour étudier l’impact de plusieurs critères sur la localisation de la sismicité induite. Ainsi, il a été montré que l’utilisation de capteurs installés profondément dans des puits et qu’une bonne couverture sismique azimutale réduit sérieusement les incertitudes de localisation. Les incertitudes du modèle de vitesse, représentées par une distribution gaussienne des modèles avec un écart de 5% autour du modèle de référence, multiplient les incertitudes de localisation par un facteur 2 à 3. Des simplifications utilisées pour le calcul ou une mauvaise connaissance du milieu peuvent mener à des imprécisions de l’ordre de 10% spatialement non isotropes. Ainsi, les structures du sous-sol peuvent être déformées dans les interprétations. L’application d’un tir de calibration peut néanmoins corriger ce fait en grande partie. L’étude d’erreurs associées aux mécanismes au foyer ne semble cependant pas conduire aux mêmes conclusions. Le biais angulaire peut certes être augmenté par l’omission de la faille dans le modèle de vitesse, mais dans plusieurs cas il est le même que dans le cas idéal voire diminué. En outre, une meilleure couverture sismique améliorerait toujours le mécanisme au foyer obtenu. Ainsi, il n’est pas conseillé d’imager un réservoir en n’utilisant que la localisation de séismes, mais une combinaison de plusieurs paramètres sismiques pourrait s’avérer efficace. La méthode appliquée dans le cadre de cette thèse pourra servir pour d’autres sites à condition d’en avoir une bonne connaissance a priori
Induced seismicity location and focal mechanisms are commonly used to image the sub-surface designin reservoirs among other tasks. In this Ph.D. the inaccuracies and uncertainties on earthquake location and focal mechanisms are quantified using a three-step method. The technique is applied to the geothermal sites of Soultz and Rittershoffen to investigate the effect of several criteria on thee arthquake location. A good azimuthal seismic coverage and the use of seismic down-hole sensors seriously decrease the location uncertainty. On the contrary, velocity model uncertainties, represented by a 5% Gaussian distribution of the velocity model around the reference model, will multiply location uncertainties by a factor of 2 to 3. An incorrect knowledge of the sub-surface or the simplifications performed before the earthquake location can lead to biases of 10% of the vertical distance separating the source and the stations with a non-isotropic spatial distribution. Hence the sub-surface design maybe distorted in the interpretations. To prevent from that fact, the calibration shot method was proved to be efficient. The study on focal mechanism errors seems to lead to different conclusions. Obviously, the angular bias may be increased by neglecting the fault in the velocity. But, it may also be the same as or even smaller than the bias calculated for the case simulating a perfect knowledge of the medium of propagation. Furthermore a better seismic coverage always leads to smaller angular biases. Hence,it is worth advising to use more than only earthquake location in order to image a reservoir. Other geothermal sites and reservoirs may benefit from the method developed here
Die korrekte Lokalisierung von induzierter Seismizität und den dazugehörigen Herdflächenlösungensind sehr wichtige Parameter. So werden zum Beispiel die Verteilung der Erdbeben und die Orientierung ihrer Herdflächenlösungen dazu benutzt um in der Tiefe liegende Reservoirs zulokalisieren und abzubilden. In dieser Doktorarbeit wird eine Technik vorgeschlagen um diemethodisch bedingten Fehler zu quantifizieren. Mit dieser Methode werden die verschiedenen Fehlerquellen, die Unsicherheiten und die Fehler im Modell getrennt. Die Technik wird für die geothermischen Felder in Soultz und in Rittershoffen benutzt um den Einfluss verschiedener Parameter (Annahmen) auf die Lokalisierung der induzierten Seismizität zu bestimmen. Es wurde festgestellt, dass Bohrlochseismometer und eine gute azimutale Verteilung der seismischen Stationen die Unbestimmtheiten verkleinern. Die Geschwindigkeitsunbestimmheiten, die durch eine Gauss-Verteilung mit 5% Fehler dargestellt werden, vervielfachen die Lokalisierungsungenauigkeiten um einen Faktor 2 bis 3. Eine ungenaue Kenntnis des Untergrunds oder die verwendete vereinfachte Darstellung der Geschwindigkeitsverhältnisse im Untergrund (notwendig um die synthetischen Rechnungen durchführen zu können) führen zu anisotropen Abweichungen und Fehlern in der Herdtiefe von bis zu 10%. Diese können die Interpretationen des Untergrunds deutlich verfälschen. Ein “calibration shot” kann diese Fehler korrigieren. Leider können die Fehler für die Herdflächenlösungen nicht in derselben Weise korrigiert werden. Es erscheint daher als keine gute Idee, ein Reservoir nur über die Lokalisierung von Erdbeben zu bestimmen. Eine Kombination mehrerer seismischer Methoden scheint angezeigt. Die hier besprochene Methode kann als Grundlage dienen für die Erkundung anderer (geothermischer)

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37

Chiorini, Sutton. "Strategies for Discriminating Earthquakes Using a Repeating Signal Detector to Investigate Induced Seismicity in Eastern Ohio." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1575050124689057.

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38

Johann, Lisa [Verfasser]. "Migration Patterns of Injection- and Postinjection-Induced Seismicity: Applications to Local and Regional Scales / Lisa Johann." Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1225741629/34.

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39

Nespoli, Massimo <1988&gt. "Modeling earthquake-fluid interaction: shallow effects on groundwater circulation and induced seismicity in deep geothermal exploitation." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7530/1/nespoli_massimo_tesi.pdf.

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The interaction between earthquakes and crustal fluids is a very complex topic due to several mechanisms that are involved and which influence each other. Some phenomena, like the alterations of springs discharge rates and fluid flow, liquefaction and changing of the water levels in phreatic wells are largely documented in the literature, but their explanation is not yet fully clear. Furthermore, these phenomena can greatly change with the rock type, the earthquake magnitude and the observation distance from the fault. Within a distance of a few fault lengths from the epicenter, an earthquake can alter both the regional stress field and the hydraulic properties of the rocks, influencing the underground fluid distribution. In this thesis, I apply the numerical simulator TOUGH2 to represent the changes in water level of some wells after the ML 5.9 earthquake that took place in Italy in 2012. The model shows that the wells response to the seismic event can be represented imposing a static stress change and highlights the role of the soil stratigraphy. This zone is also well known for localized methane seepages associated with anomalous soil temperatures. I simulate the process and draw some conclusions on the nature of this phenomenon and on the possible interactions with the local seismicity. Finally, I study the earthquake-fluid interaction from the opposite point of view: looking at how fluids can promote seismicity. I present the results obtained by coupling the TOUGH2 geothermal simulator with a stochastic seed model of seismicity. The coupled simulation could capture the main characteristics of the seismicity induced by the fluid injection in a seismically active area.
L'interazione tra terremoti e fluidi crostali è un argomento molto complesso per via dei numerosi meccanismi che sono coinvolti e che si influenzano a vicenda. Alcuni fenomeni, come l'alterazione delle sorgenti e del flusso di fluidi, la liquefazione e il cambiamento del livello d'acqua nei pozzi freatici, sono largamente documentati in letteratura, tuttavia la loro spiegazione non è ancora del tutto chiara. Oltretutto, questi fenomeni possono cambiare sensibilmente in base al tipo di roccia, alla magnitudo del terremoto e alla distanza dalla faglia. Entro una distanza di poche lunghezze di faglia dall'epicentro, un terremoto può modificare sia il campo di sforzo regionale che le proprietà idrauliche della roccia, influenzando la distribuzione dei fluidi nel sottosuolo. In questa tesi utilizzo il simulatore numerico TOUGH2 per rappresentare la variazione del livello d'acqua di alcuni pozzi successivamente al terremoto di magnitudo ML5.9 che avvenne in Italia nel 2012. Il modello mostra che la risposta dei pozzi al terremoto può essere rappresentata imponendo una variazione di stress statico ed evidenzia l'importanza della stratigrafia del sottosuolo. Questa zona è ben nota anche per emissioni di metano localizzate, associate a riscaldamenti anomali del sottosuolo. In questa tesi presento delle simulazioni per rappresentare questo processo e traggo alcune conclusioni circa la natura di questo fenomeno e sulle sue possibili interazioni con la sismicità locale. In ultimo, studio la relazione tra fluidi e terremoto dal punto di vista opposto: come I fluidi possono facilitare la sismicità. Presento i risultati ottenuti accoppiando il simulatore geotermico TOUGH2 con un modello sismico, stocastico, a “seed”. La simulazione accoppiata è in grado di catturare le caratteristiche principali della sismicità indotta dall'iniezione di fluidi in un'area sismicamente attiva.

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40

Nespoli, Massimo <1988&gt. "Modeling earthquake-fluid interaction: shallow effects on groundwater circulation and induced seismicity in deep geothermal exploitation." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7530/.

Full text

Abstract:

The interaction between earthquakes and crustal fluids is a very complex topic due to several mechanisms that are involved and which influence each other. Some phenomena, like the alterations of springs discharge rates and fluid flow, liquefaction and changing of the water levels in phreatic wells are largely documented in the literature, but their explanation is not yet fully clear. Furthermore, these phenomena can greatly change with the rock type, the earthquake magnitude and the observation distance from the fault. Within a distance of a few fault lengths from the epicenter, an earthquake can alter both the regional stress field and the hydraulic properties of the rocks, influencing the underground fluid distribution. In this thesis, I apply the numerical simulator TOUGH2 to represent the changes in water level of some wells after the ML 5.9 earthquake that took place in Italy in 2012. The model shows that the wells response to the seismic event can be represented imposing a static stress change and highlights the role of the soil stratigraphy. This zone is also well known for localized methane seepages associated with anomalous soil temperatures. I simulate the process and draw some conclusions on the nature of this phenomenon and on the possible interactions with the local seismicity. Finally, I study the earthquake-fluid interaction from the opposite point of view: looking at how fluids can promote seismicity. I present the results obtained by coupling the TOUGH2 geothermal simulator with a stochastic seed model of seismicity. The coupled simulation could capture the main characteristics of the seismicity induced by the fluid injection in a seismically active area.
L'interazione tra terremoti e fluidi crostali è un argomento molto complesso per via dei numerosi meccanismi che sono coinvolti e che si influenzano a vicenda. Alcuni fenomeni, come l'alterazione delle sorgenti e del flusso di fluidi, la liquefazione e il cambiamento del livello d'acqua nei pozzi freatici, sono largamente documentati in letteratura, tuttavia la loro spiegazione non è ancora del tutto chiara. Oltretutto, questi fenomeni possono cambiare sensibilmente in base al tipo di roccia, alla magnitudo del terremoto e alla distanza dalla faglia. Entro una distanza di poche lunghezze di faglia dall'epicentro, un terremoto può modificare sia il campo di sforzo regionale che le proprietà idrauliche della roccia, influenzando la distribuzione dei fluidi nel sottosuolo. In questa tesi utilizzo il simulatore numerico TOUGH2 per rappresentare la variazione del livello d'acqua di alcuni pozzi successivamente al terremoto di magnitudo ML5.9 che avvenne in Italia nel 2012. Il modello mostra che la risposta dei pozzi al terremoto può essere rappresentata imponendo una variazione di stress statico ed evidenzia l'importanza della stratigrafia del sottosuolo. Questa zona è ben nota anche per emissioni di metano localizzate, associate a riscaldamenti anomali del sottosuolo. In questa tesi presento delle simulazioni per rappresentare questo processo e traggo alcune conclusioni circa la natura di questo fenomeno e sulle sue possibili interazioni con la sismicità locale. In ultimo, studio la relazione tra fluidi e terremoto dal punto di vista opposto: come I fluidi possono facilitare la sismicità. Presento i risultati ottenuti accoppiando il simulatore geotermico TOUGH2 con un modello sismico, stocastico, a “seed”. La simulazione accoppiata è in grado di catturare le caratteristiche principali della sismicità indotta dall'iniezione di fluidi in un'area sismicamente attiva.

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Shabarchin, Oleg. "Induced seismicity and corrosion vulnerability assessment of oil and gas pipelines using a Bayesian belief network model." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57569.

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A substantial amount of oil and gas products are transported and distributed via pipelines, which can stretch for thousands of kilometers. Because of the adverse environmental impact and significant financial losses, the integrity of these pipelines is essential. British Columbia Oil and Gas Commission (BCOGC) has indicated metal loss due to corrosion as one of the primary causes of pipeline failures. Therefore, it is important to identify pipelines subjected to severe corrosion in order to improve corrosion mitigation and pipeline maintenance strategies, thus minimizing the likelihood of failure. To accomplish this task, this thesis presents a Bayesian belief network (BBN)-based probabilistic corrosion hazard assessment approach for oil and gas pipelines. A cause-effect BBN model has been developed by considering various types of information, such as analytical corrosion models, expert knowledge and published literature. Multiple corrosion models and failure pressure models have been incorporated into a single flexible network in order to estimate corrosion defects and the associated probability of failure. Besides corrosion hazard, BCOGC has reported multiple cases of anthropogenic seismicity, which also may compromise the pipeline integrity. To this end, this thesis explores the potential impact of induced seismicity on the oil and gas pipeline infrastructure. Spatial clustering analysis is used for earthquakes, previously registered in the region, to delineate areas, which are particularly prone to the induced seismicity. The state of the art ground motion prediction equation for induced seismicity is applied in a Monte Carlo simulation to obtain a stochastic field of the seismic intensity. Based on the established seismic fragility formulations for pipelines and mechanical characteristics as well as corrosion conditions, spatial and probabilistic distributions of the repair rate and probability of failure have been obtained and visualized with the aid of the Geographic Information System. The proposed model can help to identify vulnerable pipeline sections and rank them accordingly to enhance the informed decision making process. To demonstrate the application of the proposed approach, two case studies for the Northeastern British Columbia oil and gas pipeline infrastructure are presented.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

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Dinske, Carsten [Verfasser]. "Interpretation of fluid-induced seismicity at geothermal and hydrocarbon reservoirs of Basel and Cotton Valley / Carsten Dinske." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1025510666/34.

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Köpke, Rike [Verfasser], T. [Akademischer Betreuer] Kohl, and J. [Akademischer Betreuer] Schmittbuhl. "Fracture network characterization in enhanced geothermal systems by induced seismicity analysis / Rike Köpke ; T. Kohl, J. Schmittbuhl." Karlsruhe : KIT-Bibliothek, 2021. http://nbn-resolving.de/urn:nbn:de:101:1-2021092905002801218956.

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Minetto, Riccardo. "Essaims sismiques : comparaison des séismes naturels et induits." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALU009.

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Une séquence sismique est un ensemble de tremblements de terre qui se produisent avec une grande proximité spatiale et temporelle. Un essaim de séisme est un type de séquence sismique caractérisé par des tremblements de terre dont la localisation change au cours du temps et qui n’est pas dominé par un seul grand tremblement de terre.Dans cette thèse, j'étudie l'évolution spatio-temporelle d'essaims sismiques naturels et induits dans le but d'identifier les processus physiques qui les produisent et de caractériser les propriétés des systèmes de failles activés. Plus spécifiquement, je me concentre sur trois aspects clés de l'activité sismique : l'évolution temporelle du taux de sismicité, la localisation des séismes et la distribution des magnitudes. L'étude se concentre sur deux essaims sismiques. Le premier, d'origine naturelle, s'est produit dans la vallée de la Maurienne (Alpes françaises) entre 2017 et 2019, tandis que le second a été induit par des opérations de fracturation hydraulique à Preston New Road, au Royaume-Uni, en 2019. Pour assurer une analyse à haute résolution de ces séquences, j'ai d'abord créé des catalogues améliorés qui intègrent de nombreux événements nouvellement détectés ainsi que des magnitudes et des localisations plus précises.La migration des séismes pendant l'essaim de Maurienne suggère que cette séquence a pu être activée par une combinaison de multiples diffusions de fluides à haute pression et d'interactions entre séismes. De plus, la proportion de petits et grands événements (paramètre b de la loi de Gutenberg-Richter) varie dans l'espace, et ce changement peut être lié à la dimension des failles actives.En plus de l'étude de l'activité sismique, j'ai appliqué l'interférométrie du bruit sismique ambiant pour évaluer si les changements de contraintes pendant l'essaim ont créé des variations détectables de la vitesse des ondes sismiques. Les changements de vitesse semblent être principalement influencés par un processus saisonnier probablement lié aux variations de pression interstitielle dues aux précipitations. Cependant, pendant la période principale d'activité sismique, ces changements ont pu être amplifiées par les secousses du sol résultant de l'occurrence prolongée de séismes.La séquence de Preston New Road est caractérisée par un taux de sismicité et une distribution des magnitudes qui évoluent progressivement au fur et à mesure que les fluides sont injectés de manière répétée et que le volume de la zone sismogénique grandit. Ceci suggère que l'activité sismique au cours d'une phase d'injection dépend de l'historique des phases précédentes.Les séquences de Maurienne et de Preston New Road ne sont que deux exemples du phénomène plus large des essaims sismiques et induits. Néanmoins, ces deux séquences illustrent le fait que les essaims induits et naturels peuvent présenter des propriétés similaires dans leur évolution spatio-temporelle, comme la migration des séismes et la dépendance de la valeur de b à l'échelle du système de failles. Cela souligne la possibilité d'appliquer les connaissances acquises lors de l'étude d'un type d'essaim pour améliorer notre compréhension de l'autre
A seismic sequence is a cluster of earthquakes that occur in close spatial and temporal proximity. One type of seismic sequence is a seismic swarm, which is typically characterized by earthquakes whose location changes over time and by the absence of a single, dominant, large earthquake.In this thesis, I investigate the spatio-temporal evolution of natural and induced seismic swarms with the aim of identifying the physical processes that drive them and characterizing the properties of the activated fault systems. More specifically, I focus on three key aspects of the seismic activity: temporal evolution of the seismicity rate, earthquake location and frequency-magnitude distribution. The study focuses on two seismic swarms. The first one, of natural origin, occurred in the Maurienne valley (French Alps) between 2017 and 2019, while the second one was induced by hydraulic fracturing operations at Preston New Road, UK, in 2019. To ensure a high-resolution analysis of these sequences, I first created improved catalogs, which incorporate newly detected events and more accurate magnitudes and hypocenter locations.The migration of earthquakes during the Maurienne swarm suggests that this sequence may have been triggered by a combination of multiple pulses of high-pressure fluids and earthquake-to-earthquake interactions. Additionally, the proportion of small and large events (i.e., the b-value of the Gutenberg-Richter law) varies in space, and this change may be linked to the size of the active fault systems.In addition to the study of the seismic activity, I applied ambient noise interferometry to assess if stress changes during the Maurienne swarm produced detectable variations in seismic wave velocity. The velocity changes appear to be primarily influenced by a seasonal process possibly related to pore pressure variations due to rainfall. However, during the main period of seismic activity, such changes may also be accentuated by the continuous ground shaking resulting from the prolonged occurrence of earthquakes.The Preston New Road sequence is characterized by a seismicity rate and a frequency-magnitude distribution that gradually evolve as fluids are repeatedly injected and the seismogenic volume expands in size. This suggests that the seismic activity during an injection stage depends on the injection history of past stages.The Maurienne and Preston New Road sequences are just two examples of the broader phenomenon of seismic and induced swarms. Nonetheless, these two sequences illustrate that induced and natural swarms can exhibit similar patterns in their spatio-temporal evolution, such as earthquake migration and the dependence of the b-value on the scale of the fault system. This emphasizes the potential of applying the knowledge gained from studying one type of swarm to improve our understanding of the other

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Skoumal, Robert J. "Characterizing induced and natural earthquake swarms using correlation algorithms." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1460552844.

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Dias, Fábio Luiz. "Estudo da Camada de Basalto em Bebedouro, Bacia do Paraná, com Função do Receptor - Implicações para a Sismicidade Induzida por Poços Profundos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-12062018-172635/.

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Este trabalho consiste no estudo da estrutura sedimentar da Bacia do Paraná da região de Bebedouro utilizando função do receptor, ondas de superfície e sísmica de refração. Funções do Receptor (FR) mostram a resposta da estrutura geológica abaixo de uma estação sismográfica. Para diminuir a não unicidade na inversão do traço de uma FR, foram usadas curvas de dispersão de ondas de superfície como vínculos adicionais. Ondas de superfície foram também obtidas com a correlação cruzada de ruído sísmico ambiental. Esse método passivo permite a obtenção de dispersão em períodos intermediários entre os dados de telessismos e os dados de sísmica rasa auxiliando na determinação estruturas sedimentares. Foi utilizada a inversão conjunta de FR de alta e baixa frequência, dispersão de fase e grupo de períodos menores que 2 s e dispersão de ondas Love e Rayleigh continentais (períodos entre 10 e 100 s). Na inversão conjunta, foram usados vários modelos iniciais diferentes para garantir melhor cobertura do espaço de soluções possíveis. Os resultados mostram uma camada de basalto com uma espessura entre 200 e 400 m, sob uma camada superficial de arenito de 50 a 100m. O embasamento da bacia está torno de 2.5 3.0 km. A espessura e razão Vp/Vs crustal da região foi estimada em 40.0 (1.0) km e 1.78 (0.02). Foi possível identificar zonas de baixa velocidade dentro do pacote de basalto, possivelmente relacionadas a zonas de fraturas ou camadas de basalto alterado. Estas camadas de baixa velocidade estão na parte sul, próximas à área de maior sismicidade induzida e também relativamente mais perto dos poços profundos de maior vazão. Isto corrobora com a hipótese de que a sismicidade local está associada à exploração de poços e estrutura de falhas pré -existentes.
A study of the seismic structure of the Paraná Basin in Bebedouro, SP, was carried out with Receiver Functions (RF). Both low frequency (with ~0.5 Hz low pass filter) and high-frequency (~10Hz) RFs were jointly inverted with surface wave dispersion curves. Surface-wave data included: long-period group velocities of Rayleigh and Love waves from continental-scale tomography in the period range 10-100 s (useful to control crustal scale structure and Moho depth), intermediate period group velocities near 1s period obtained from cross-correlation of ambient noise (useful to control sedimentary structure), phase velocities near 0.2-1.0 s obtained from local earthquakes, and phase velocities of Rayleigh waves from shallow seismic refraction data near ~0.1 s period (useful to control shallow layers). Joint inversion was obtained with several different initial models to better cover all possible solutions. The results indicate that the basalt layer is 200 to 400m thick, beneath sandstones of about 50 100m thick. The Basin basement was detected between 2.5 3.0 km depth, consistent with expected values from regional bore-hole data in the Paraná Basin. Beneath several stations a low-velocity zone was detected in the middle of the basalt pack which is interpreted as a zone of fractured or altered basalt. This anomalous low-velocity layer was detected near the most seismically active zone in the Andes district. It is also relatively close to the deep wells with larger outflow. The existence of this low-velocity zone in the middle of the basalt layer is consistent with the model proposed for the water-well induced seismicity.

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PANEBIANCO, SERENA. "Fluid injections in the subsurface: a multidisciplinary approach for better understanding their implications on induced seismicity and the environment." Doctoral thesis, Università degli studi della Basilicata, 2022. http://hdl.handle.net/11563/154467.

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Fluid injections in the subsurface are common operations in underground industrial activities such as oil and gas exploitation, geothermal energy development, and carbon capture and storage (CCS). In recent years, it became a focal point as new drilling technologies (e.g., hydraulic fracturing) enable the extraction of oil and gas in unconventional reservoirs and the development of CCS injection techniques became a key research topic in the context of the low-carbon energy transition. Fluid injections have drawn the attention also in the general public because of their main potential implications such as the induced seismicity phenomenon (Rubinstein and Mahani, 2015) and the environmental pollution (Burton et al., 2016, Pitchel et al., 2016). Considering the strong socioeconomic impact of fluid injection operations (National Research Council, 2013; Ellsworth, 2013; Grigoli et al., 2017) the current research in this field needs the integration of multidisciplinary studies, involving knowledge on geology, seismology, source physics, hydrogeology, fluid geochemistry, rocks geomechanics for a complete understanding of the phenomenon and to set-up the most effective and “best practice” protocols for the monitoring of areas where injection operation are performed. On this basis, this work applied a multidisciplinary approach integrating seismological methods, geochemical studies, and machine learning techniques. Two key-study areas characterized by high fluid-rock interaction and fluid-injection in the subsurface were analyzed: i) the High Agri Valley (hereinafter HAV), hosting the largest onshore oil field in West Europe, in which wastewater disposal operations have been carried out since 2006 at the Costa Molina 2 injection well and where both natural and induced seismicity clusters were recognized; ii) the Mefite d’Ansanto, the largest natural emission of CO2-rich gases with mantle-derived fluids (from non‐volcanic environment) ever measured on the Earth (Carcausi et al., 2013; Caracausi and Paternoster, 2015; Chiodini et al, 2010). Regarding the HAV study area, we reconstructed the preliminary catalogue of seismicity through accurate absolute locations in a 3D-velocity model (Serlenga and Stabile, 2019) of earthquakes detected from the local seismic INSIEME network managed by the CNR-IMAA. A total of 852 between local tectonic and induced earthquakes occurred in the HAV between September 2016 and March 2019. We tested the potential of the unsupervised machine-learning approach as an automated tool to make faster dataset exploratory analysis, founding the density-based approach (DBSCAN algorithm-Density-Based Spatial Clustering of Applications with Noise, Ester et al., 1996) particularly suitable for the fast identification of clusters in the catalogue resulting from both injection-induced events and tectonic local earthquake swarms. Moreover, we proposed a semi-automated workflow for earthquake detection and location with the aim to improve the current standard procedures, quite time-consuming and strictly related to human operators. The workflow, integrating manual, semi-automatic and automatic detection and location methods enabled us to characterize a low magnitude natural seismic sequence occurred in August 2020 in the southwestern area of the HAV (Castelsaraceno sequence) in a relatively short time with respect to the application of standard techniques, thus representing a starting point for the improvement of the efficiency of seismic monitoring techniques of both anthropogenic and natural seismicity in the HAV. Our multidisciplinary approach involved the geochemical study of the HAV groundwaters with the aim to: (1) determine the geochemical processes controlling the chemical composition; (2) define a geochemical conceptual model regarding fluid origin (deep vs shallow) and mixing processes by means isotopic data; (3) establish a geochemical baseline for the long-term environmental monitoring of the area. A total of 39 water samples were collected from springs and wells located at the main hydro-structures bordering the valley to determine chemical (major, minor and trace elements) and isotopic composition (e.g., dD, d18O, d13C-TDIC and noble gas). All investigated water samples have a meteoric origin, although some springs show long and deep flow than the other ones, and a bicarbonate alkaline-earth composition, thus suggesting the carbonate hydrolysis as the main water-rock interaction process. Our results demonstrated that HAV groundwater is chemically suitable for drinking use showing no criticalities for potentially toxic metals reported by the Italian and European legislation guidelines. Particular attention was given on thermal water of Tramutola well, built by Agip S.p.a. for oil & gas exploration, with the occurrence of bubbling gases. The geochemical study highlighted a substantial difference of these CH4-dominated thermal fluids with the rest of the dataset. Helium isotope (3He/4He) indicate a prevalent radiogenic component with a contribution of mantle-derived helium (~20%) and the average δ13C-CO2 value is of – 4.6 ‰ VPDB, consistent with a mantle origin. Methane isotope composition indicates a likely microbial isotopic signature (δ13C-CH4 =−63.1‰, −62.4‰, δD-CH4=−196‰, −212‰), probably due to biodegradation processes of thermogenic hydrocarbons. The methane output at the well, evaluated by means of anemometric measurement of the volume flow (m3/h) is of ~156 t/y, that represent about 1.5% of total national anthropogenic sources related to fossil fuel industry (Etiope et al., 2007). Our work highlighted that Tramutola well may represent a key natural laboratory to better understand the complex coupling effects between mechanical and fluid-dynamic processes in earthquake generation. Moreover, the integration of seismic and geochemical data in this work allowed us to identify the most suitable locations for the future installation of multiparametric stations for the long-term monitoring of the area and development of integrated research in the HAV. Regarding the Mefite d’Ansanto, we analyzed the background seismicity in the emission area recorded by a dense temporary seismic network deployed at the site between 30-10-2019 and 02-11-2019. First, we implemented and tested an automated detection algorithm based on non-parametric statistics of the recorded amplitudes at each station, collecting a total dataset of 8561 events. Then, both unsupervised (DBSCAN) and supervised (KNN-k-nearest neighbors classification, Fix & Hodges, 1951) machine learning techniques were applied, based on specific parameters (duration, RMS-amplitude and arrival slope) of the detected events. DBSCAN algorithm allowed to determine characteristic bivariate correlations among tremors parameters: a high linear correlation (r~0.6-0.7) between duration and RMS-amplitude and a lower one (r~0.5-0.6) between amplitude and arrival slope (first arrival parametrization). These relationships let us to define training samples for the KNN algorithm, which allowed to classify tremor signals at each station and to automatically discriminate between tremors and accidentally detected anthropogenic noise. Results allowed to extract new information on seismic tremor at Mefite d’Ansanto, previously poorly quantitively analyzed, and its discrimination, thus providing a starting workflow for monitoring the non-volcanic emission. Isotopic geochemistry (3He/4He, 4 He/20Ne, δ13CCO2) indicated a mixing of mantle (30%-40%) and crust-derived fluids. The source location of the emission related tremor would represent a step forward in its characterization, and for setting up more advanced automated detection and machine learning classification techniques to exploit the information provided by seismic tremor for an improved automatic monitoring of non-volcanic, CO2 -gas emissions.

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Holcomb, Andrew. "INITIAL MICROSEISMIC RECORDINGS AT THE ONSET OF UNCONVENTIONAL HYDROCARBON DEVELOPMENT IN THE ROME TROUGH, EASTERN KENTUCKY." UKnowledge, 2017. http://uknowledge.uky.edu/ees_etds/51.

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The Cambrian Rogersville Shale is a part of a hydrocarbon system in the Rome Trough of eastern Kentucky and West Virginia that can only be produced unconventionally. In Kentucky, the Rogersville Shale ranges in depth from ~1,800 to ~3,700 m below the surface with the crystalline basement ~1,000 m lower than the formation’s base. Baseline Rome Trough microseismicity data were collected, focusing on wastewater injection wells and recently completed and planned unconventional hydrocarbon test wells in the Rogersville Shale, using thirteen broadband seismic stations installed between June, 2015 and June, 2016 and existing University of Kentucky and central and eastern United States network stations. In addition, the network’s minimum detection threshold, the magnitude at which the theoretical signal exceeds the noise by a factor of 3 between 1 and 20 Hz for at least 4 stations, was estimated for the project area. Thirty-eight local and regional events were located and magnitudes were calculated for each event. No events were proximal to operating disposal or hydrocarbon test wells, nor did any occur in the eastern Kentucky’s Rome Trough. The minimum detection threshold varies between 0.4 and 0.7 Mw from 0000-1100 UTC and 0.6 to 0.9 Mw from 1100-2300 UTC.

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Carr, Steve Asamoah Boamah. "Crustal stress changes induced by seasonal hydrological load variations in correlation with seismicity rate changes in the Malawi Rift System." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1621867336511141.

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Smith, Sarah L. R. "Re-evaluation of the 2009-2011 Southern Fort-Worth Basin (TX) Earthquakes: Potential Relationships with Hydraulic Fracturing and Wastewater Injection." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501284292875227.

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Dissertations / Theses on the topic 'Induced seismicity'

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