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Dissertations / Theses on the topic 'Earthquakes Volcanoes'
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Roberts, Nick Stuart. "Earthquake distributions at volcanoes : models and field observations." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/23653.
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Volcanic earthquakes can provide significant insight into physical processes acting at volcanoes, such as magma accumulation and the mechanisms of deformation of the volcanic edifice. At the same time a statistical analyses of volcanic seismicity prior to an eruption (for example variations in the Gutenberg-Richter b-value – a measure of the proportion of large and small events) are a key component of the practical problem of forecasting eruptions. This thesis aims to tackle two key areas of research that are closely related to these important overall goals, by comparing seismic data obtained from currently-active volcanoes with direct field observation of faulting and fracturing from an exhumed extinct volcano. First I introduce a new approach that improves the accuracy and reliability of calculating spatial and temporal variations of the seismic b-value for frequency-magnitude distributions at active volcanoes, and apply it to several test cases. An extensive literature review highlights a large variability and lack of standardisation of methodology used to analyse frequency-magnitude distributions in the past. Motivated by this, I introduce and test a new workflow to standardise calculating completeness magnitudes of seismic catalogues. The review also highlights the fact that uncertainties in estimating the threshold magnitude of complete reporting have been ignored to date. Here I use synthetic catalogues to quantify this previously unidentified source of error, and provide a template to estimate the total error in b-value. In standard analysis it is also common to sample time windows subjectively, although this can introduce bias. Here I develop a new objective, iterative sampling method that calculates the b-value as a full probability density function which need not have a Gaussian error structure. Application of this method reveals ‘mode-switching’ behaviour for the first time in volcanic seismic catalogues. The results also show b-values often do have a value indistinguishable from that of tectonic seismicity (b=1 within error). Nevertheless there are also several robust examples of real high b-values, as high as 3.3. The second part of the study is based on a field campaign to investigate the fracture zones from an exhumed volcanic setting on the Isle of Rum, NW Scotland. Lithological and structural mapping is used to collect structural data that is then used to quantify and explain complex fracture patterns and the underlying intra-magma chamber processes that occurred there in the geological past. In particular I identify a singular collapse event within the youngest volcanic unit, the Central Intrusion. This is responsible for forming the observed igneous breccias and the lineaments on satellite images that I interpret as contemporaneous faults. Using appropriate scaling relations, I infer the b-value for the Rum lineaments data. This would have been relatively high, at a value of approximately 1.9. The final part of the study compares the fracture data on Rum to earthquake distributions at El Hierro volcano, Canary Islands. Here I show the level of fractal clustering is similar in both an extinct (60 Ma) and a currently active volcano. Both show similar high levels of clustering. However, in both cases there is a difference between the capacity and correlation dimensions (D₀≠D₂), implying the set of rupture sources or mapped fault traces form a multi-fractal set. Broadly, the scaling of fracture sets in an ancient volcano has similar properties to those observed in a modern volcano, except that the Rum data imply a greater absolute degree of spatial clustering of deformation than that for the recent unrest at El Hierro.
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Hill-Butler, C. "Evaluating the effect of large magnitude earthquakes on thermal volcanic activity : a comparative assessment of the parameters and mechanisms that trigger volcanic unrest and eruptions." Thesis, Coventry University, 2015. http://curve.coventry.ac.uk/open/items/5f612a7d-ebbf-4d38-90aa-89c4984a1c0f/1.
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Volcanic eruptions and unrest have the potential to have large impacts on society causing social, economic and environmental losses. One of the primary goals of volcanological studies is to understand a volcano’s behaviour so that future instances of unrest or impending eruptions can be predicted. Despite this, our ability to predict the onset, location and size of future periods of unrest remains inadequate and one of the main problems in forecasting is associated with the inherent complexity of volcanoes. In practice, most reliable forecasts have employed a probabilistic approach where knowledge of volcanic activity triggers have been incorporated into scenarios to indicate the probability of unrest. The proposed relationship between large earthquakes and volcanic activity may, therefore, indicate an important precursory signal for volcanic activity forecasting. There have been numerous reports of a spatial and temporal link between volcanic activity and high magnitude seismic events and it has been suggested that significantly more periods of volcanic unrest occur in the months and years following an earthquake than expected by chance. Disparities between earthquake-volcano assessments and variability between responding volcanoes, however, has meant that the conditions that influence a volcano’s response to earthquakes have not been determined. Using data from the MODVOLC algorithm, a proxy for volcanic activity, this research examined a globally comparable database of satellite-derived volcanic radiant flux to identify significant changes in volcanic activity following an earthquake. Cases of potentially triggered volcanic activity were then analysed to identify the earthquake and volcano parameters that influence the relationship and evaluate the mechansisms proposed to trigger volcanic activity following an earthquake. At a global scale, this research identified that 57% [8 out of 14] of all large magnitude earthquakes were followed by increases in global volcanic activity. The most significant change in volcanic radiant flux, which demonstrates the potential of large earthquakes to influence volcanic activity at a global scale, occurred between December 2004 and April 2005. During this time, new thermal activity was detected at 10 volcanoes and the total daily volcanic radiant flux doubled within 52 days. Within a regional setting, this research also identified that instances of potentially triggered volcanic activity were statistically different to instances where no triggering was observed. In addition, assessments of earthquake and volcano parameters identified that earthquake fault characteristics increase the probability of triggered volcanic activity and variable response proportions at individual volcanoes and regionally demonstrated the critical role of the state of the volcanic system in determining if a volcano will respond. Despite the identification of these factors, this research was not able to define a model for the prediction of volcanic activity following earthquakes and, alternatively, proposed a process for response. In doing so, this thesis confirmed the potential use of earthquakes as a precursory indicator to volcanic activity and identified the most likely mechanisms that lead to seismically triggered volcanic unrest.
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Woods, Jennifer. "Dyke-induced earthquakes during the 2014-15 Bárðarbunga-Holuhraun rifting event, Iceland." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289448.
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Understanding dykes is vital as they serve both as bodies that build the crust and as conduits that feed eruptions. The 2014-15 Bárðarbunga-Holuhraun rifting event comprised the best-monitored dyke intrusion to date and the largest eruption in Iceland in 230 years. Over a 13 day period magma propagated laterally from the subglacial Bárðarbunga volcano, Iceland, along a 48 km path before erupting in the Holuhraun lava field on 29 August 2014. A huge variety of seismicity was produced, including over 30,000 volcano-tectonic earthquakes (VTs) associated with the dyke propagation at ∼ 6 km depth below sea level, and long-period seismicity - both long-period earthquakes (LPs) and tremor - associated with the eruption processes. The Cambridge University seismic network in central Iceland recorded the dyke seismicity in unprecedented detail, allowing high resolution analyses to be carried out. This dissertation comprises two parts: study of 1) the volcano-tectonic dyke-induced seismicity and 2) the long-period seismicity associated with eruption processes. Volcano-tectonic earthquakes induced by the lateral dyke intrusion were relocated, using cross-correlated, sub-sample relative travel times. The ∼ 100 m spatial resolution achieved reveals the complexity of the dyke propagation pathway and dynamics (jerky, segmented), and allows us to address the precise relationship between the dyke and seismicity. The spatio-temporal characteristics of the induced seismicity can be directly linked in the first instance to propagation of the tip and opening of the dyke, and following this - after dyke opening - indicate a relationship with magma pressure changes (i.e. dyke inflation/deflation), followed by a general 'post-opening' decay. Seismicity occurs only at the base of the dyke, where dyke-imposed stresses - combined with the background tectonic stress (from regional extension over > 200 years since last rifting) - are sufficient to induce failure of pre-existing weaknesses in the crust, while the greatest opening is at shallower depths. Emplacement oblique to the spreading ridge resulted in left-lateral shear motion along the distal dyke section (studied here), and a prevalence of left-lateral shear failure. Fault plane strikes are predominately independent of the orientation of lineations delineated by the hypocenters, indicating that they are controlled by the underlying host rock fabric. Long-period earthquakes and tremor were systematically detected and located during the dyke propagation phase and the first week of the eruption. Clusters of highly similar, repetitive LPs were identified, with a peak frequency of ∼ 1 Hz and clear P and S phases followed by a long-duration coda. The source mechanisms were remarkably consistent between clusters and also fundamentally different to those of the VTs. The clusters were accurately located near each of three ice cauldrons (depressions formed by basal melting) that were observed on the surface of Dyngjujökull glacier above the path of the dyke. Most events were in the vicinity of the northernmost cauldron, at shallower depth than the VTs associated with lateral dyke propagation. At the two northerly cauldrons, periods of shallow seismic tremor following the clusters of LPs were also observed. Given that the LPs occurred at ∼ 4 km depth and in swarms during times of dyke-stalling, it is inferred that they result from excitation of magmatic fluid-filled cavities and indicate magma ascent. The tremor may then represent the climax of the vertical melt movement, arising from either rapid, repeated excitation of the same LP cavities, or sub-glacial eruption processes. This long-period seismicity therefore highlights magma pathways between the depth of the dyke-VT earthquakes and the surface. Notably, no tremor is detected associated with each cauldron, despite melt reaching the base of the overlying ice cap, a concern for hazard forecasting.
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Fuchs, Florian [Verfasser]. "Dynamic triggering: The effects of remote earthquakes on volcanoes, hydrothermal systems and tectonics / Florian Fuchs." Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1077289243/34.
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Loureiro, Miguel. "Of the earthquake and other stories : the continuity of change in Pakistan-administered Kashmir." Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/43284/.
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On October 8th 2005 the villages surrounding Chinati bazaar in Bagh district of Pakistani-administered Kashmir (PaK) were hit by an earthquake measuring 7.6 on the Richter scale that affected the lives of more than 3.5 million people in PaK and Khyber Pukhtunkhwa. In this thesis I attempt to understand, through the stories and narratives of the people of Chinati bazaar, how they lived through, made sense of, and dealt with the earthquake and its aftermath. I use participant observation and conversations to tell the stories of those affected by the earthquake in their own voices as much as possible. The storytellers of the bazaar lived through two types of events: the earthquake itself and the post-earthquake rehabilitation and reconstruction process. The latter brought with it both positive and negative impacts: if, on the one hand, it brought progress and a new hope that life could be ‘Built Back Better', on the other hand, it brought a different type of suffering – one that led to a loss of honour and dignity, resulted in social upheavals, and led to the exclusion and marginalization of certain groups. In this thesis I focus on both these ‘events'. Through these stories I build an argument about post-disaster discourses of change. I argue that while the narratives of the storytellers of Chinati bazaar posit the earthquake as a point of rupture in their confabulated stories, from which the collective memory of the bazaar dates its movement towards becoming modern and global, these changes have their origins instead in ‘bigger' stories of modernisation and globalisation that predate the earthquake and that highlight and emphasise more continuous processes of change that have been occurring over a longer period of time. In this thesis I analyse how these two competing discourses of rupture and dramatic change on the one hand, and slow, continuous change on the other, play out in the lives of the storytellers of Chinati Bazaar.
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Feng, Lujia. "Investigations of volcanic and earthquake-related deformation: observations and models from Long Valley Caldera, Northwestern Peloponnese, and Northwestern Costa Rica." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41220.
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The advent of Global Positioning System (GPS) has revolutionized geodesy with high accuracy, fast speed, simple use, and low cost. This dissertation investigates three topics on volcano and earthquake-related deformation using GPS measurements and models to demonstrate the power of the new generation of geodetic methods. The three topics include the 2002-2003 continued episodic inflation at Long Valley Caldera in eastern California, the coseismic and postseismic response of the energetic 2008 MW 6.4 Achaia-Elia Earthquake in northwest Peloponnese, Greece, and the interseismic megathrust coupling and forearc sliver transport near the Nicoya Peninsula in northwest Costa Rica.
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Ratdomopurbo, Antonius. "Étude sismologique du volcan Merapi et formation du dome de 1994." Grenoble 1, 1995. http://www.theses.fr/1995GRE10064.
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Le merapi est un volcan qui a une activite quasi-continue. L'explosion est normalement accompagnee par une serie de nuees-ardentes, dites merapiennes. La chronologie d'activite volcanique varie d'une activite a l'autre, il est donc difficile de trouver le niveau d'activite sismique critique pour ce volcan. En principe, il y a 2 types d'activite: avec et sans seismes volcanotectoniques de types vta et vtb. Les donnees de seismes de types vta et vtb recoltees au courant de l'annee 1991 qui ont servi a cette etude, ont fait l'objet d'un traitement de routine (depouillement, localisation de l'hypocentre,). Ce traitement nous a conduit a remarquer que les seismes de type vta et ceux de vtb sont separes par une zone asismique a environ 1. 5 km de profondeur. Ce resultat et celui de l'analyse petrographique (berthommier et al. , 1992) conduisent a l'existence d'une poche magmatique a cette profondeur. Parmi les seismes de type vtb, nous avons trouve certains de forme similaire, que l'on appelle doublets ou multiplets. En analysant la variation du delai le long du sismogramme, en utilisant la methode inter-spectrale de la fenetre mobile, nous avons constate que la vitesse sismique a augmente d'environ 1. 7% de janvier a septembre 1991. Cette valeur est de l'ordre de dix fois celle observee sur la region tectonique. L'augmentation de vitesse est generee par la croissance de la pression du magma avant l'eruption. La surveillance de la formation du dome de 1994 a montre que, au bout d'un moment, le processus s'arrete. Nous supposons que ceci est du a l'equilibre qui s'etablit entre la pression du magma a l'extremite du conduit et la pression lithostatique que genere le dome lui meme. Si cet equilibre quasi-stable est interrompu, l'explosion se produit comme celle du 22 novembre 1994
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Hidayati, Sri. "Study on volcano-tectonic earthquakes at Sakurajima volcano and its surroundings." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136776.
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Bracamontes, Dulce Maria Vargas. "Stress models related to volcano-tectonic earthquakes." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540585.
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Jeddi, Zeinab. "Seismological Investigation of Katla Volcanic System (Iceland) : 3D Velocity Structure and Overall Seismicity Pattern." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303342.
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The work in this thesis concentrates on Katla volcano in southern Iceland. This is one of Europe’s most active volcanoes and its history tells us that it poses many threats to society, both locally (Iceland) and on a broader scale (Europe). Its geological setting is complex, where the effects of a melting anomaly in the mantle and a changing rift geometry, perturb the classical setting of volcanism in a rifting setting. The work has focused on two aspects. The first is the varying distribution of physical properties in the subsurface around the volcano. The second is the distribution of microearthquakes around the volcano. The physical properties that we study are the speeds of seismic waves that reflect variations of temperature, composition and fracturing of the rocks. These can, therefore, help us learn about long-term processes in the volcano. The seismicity gives shorter-term information about deformation associated with current processes. I have applied two tomographic techniques to study Katla’s subsurface to a depth of 5-10 km, namely local-earthquake and ambient-noise tomography. The former makes use of the timing of waves generated by local earthquakes to constrain the earthquakes’ locations and the distribution of wave speed. Here I have concentrated on compressional waves or P waves with a typical frequency content around 10 Hz. With the latter, surface waves are extracted from microseismic noise that is generated far away at sea and their timing is measured to constrain their wave-speed distribution, which then is used to map shear-wave velocity variations. This is done at a typical frequency of 0.3 Hz. I find that the volcano contains rocks of higher velocity than its surroundings, that Katla’s caldera is underlain by low velocities at shallow depth that may be explained by hot or partially molten rocks and that beneath the caldera lies a volume of particularly high velocities that may constitute differentiated cumulates. But, I also find that it is not simple to compare results from such different wave types and discuss a number of complications in that regard. In addition to the well-known microearthquake distribution in the caldera region of Katla and to its west, we have discovered two additional areas of microearthquake activity on the volcano’s flanks, south and east of the caldera. These point to current activity and are, therefore, of interest from a hazard point of view. However, it is difficult to pinpoint their underlying process. Speculation about possible interpretation leads me to hydrothermal processes or small pockets of melt ascending due to their buoyancy or locally enhancing fluid pressure, thereby lowering the effective stress.
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Sadikin, Nurlia. "Volcano-tectonic Earthquakes and Magma Supply System at Guntur Volcano, with Long-term Dormant Period." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124353.
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Beale, Jacob N. "Local Earthquake Tomography at Mt. Pinatubo, Philippines." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34635.
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A new high-resolution 3-dimensional P-wave velocity model for Mt. Pinatubo volcano was developed by tomographic inversion of P-wave arrivals from 3,007 earthquakes recorded during a four month period from May to August, 1991. The arrivals were recorded by a network of seismic stations, consisting of seven pre-eruption stations and seven post-eruption stations. Two stations survived the June eruptions. First-arrival travel times were calculated using a finite-difference solution to the eikonal equation. An iterative, linearized approximation of the nonlinear tomography problem was used to solve separately for both velocity structure and hypocenter locations. Several inversions performed with different initial parameters and convergence schemes, and synthetic checkerboard reconstructions indicate a horizontal spatial resolution of velocity perturbations near 4 km. However, the network sparseness allows for a substantial trade-off between focal depth, origin time, and the vertical velocity profile. Many hypocenter clusters collapse from diffuse clouds into tighter features after 3-D relocation. These bands of earthquakes appear to represent fault-related structures. Three low-velocity (relative to the horizontal average) anomalies exist within the well-resolved portion of the velocity model. These anomalies are spatially associated with pre- and post-eruption earthquakes oriented along mapped surface fault zones. Similar anomalies observed at different volcanoes have been previously interpreted as magma related. The low-velocity anomalies at Pinatubo are interpreted as highly fractured, hot volumes of mostly competent rock, which may contain partial melt.Master of Science
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Sgattoni, Giulia <1986>. "Characteristics and Geological Origin of Earthquakes and Tremor at Katla Volcano (S-Iceland)." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7439/.
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Katla is a hazardous volcano in south Iceland, hosting a large caldera covered by the Mýrdalsjökull glacier. The last phreatomagmatic eruption occurred in 1918 and the present repose time is the longest known in history. The 2010 eruption of the neighbouring Eyjafjallajökull volcano prompted scientists’ concerns because the two volcanoes are tectonically connected. No visible eruption occurred, but in July 2011 a 23 hour tremor burst was associated with a glacial flood which caused damage to infrastructure. Deepening of the geothermally fed ice cauldrons, increased earthquake activity within the caldera and new seismicity on the south flank were also observed. Analysis of seismic data, including development of new location strategies, and a geological field study of the south flank were conducted to interpret the seismic sources. The tremor burst consisted of two volcano-related phases originated at the active cauldrons and a third phase generated by the flood. The increased seismicity inside the caldera and evidence of rapid ice melting may indicate that the volcano-related tremor was caused by a subglacial eruption. Alternatively, tremor may have been generated by hydrothermal boiling induced by the flood. The seismicity on the south flank consists of long-period repeating events occurring with regular time intervals, modulated by seasons (higher occurrence in summer). Because of the temporal evolution, hypocentre depth distribution and coincidence with the 2011 unrest, a volcano-related source is considered more likely than a glacial one. Hydrothermal processes may be easier to reconcile with the seasonal pattern than magmatic, although no direct indication of hydrothermal activity was found. A field survey revealed previously unknown flank eruption sites within the south flank. A magmatic source for the seismicity should therefore not be discarded. This observation is of major importance for hazard assessment of the south flank of Katla.
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Konstantinou, Konstantinos I. "Seismological studies of magma injection processes : volcano monitoring and imaging of magma chambers." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3847/.
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The processes associated with magma injection at shallow depths within the crust have been the topic of many geophysical studies, some investigating the seismicity that accompanies volcanic activity and others attempting to map the subsurface extent and geometry of the resulting magma bodies. The aim of this study is to obtain a better understanding of these processes by investigating the nature of seismic signals that accompany volcanic eruptions and by seismically imaging a magma body beneath a mid-ocean ridge, both located on, or adjacent to Iceland. The seismic phenomena associated with the 1996 Vatnajӧkull subglacial eruption in central Iceland, have been studied using data recorded by both temporary (HOTSPOT) and permanent (SIL) seismic networks. These networks comprise 60 broadband and short-period three-component seismographs and cover most parts of the country. Two very active volcanic systems, Bárdarbunga and Grimsvӧtn, are situated underneath the Vatnajokull ice cap. The volcanoseismic signals recorded there were categorised according to their waveform shape and frequency content, into three groups: (a) low-frequency events (1-2 Hz); (b) mixed-frequency events (1-4 Hz); and (c) volcanic tremor. The eruption was preceded by intense seismic activity which began with a = 5.6 earthquake located at the Bárdarbunga volcanic system. The epicentres of the earthquake swarm that followed the M(_w), = 5.6 event initially delineated the Bárdarbunga caldera rim and then migrated towards Grimsvӧtn, to a place where a fissure was later observed. Pre-eruptive tremor started at least two days before the eruption as a harmonic signal around five narrow frequency bands (0.5-0.7, 1.6, 2.2, 2.8 and 3.2 Hz). Co-eruptive tremor started as a broadband, continuous signal which evolved into low-amplitude background tremor interrupted by high-amplitude, cigar-shaped bursts. Further analysis revealed that continuous tremor and the cigar-shaped bursts had all the characteristics of low- dimensional chaotic signals. Geophysical and geochemical evidence suggest that a lateral migration of magma from Bárdarbunga facilitated the rupture of the roof of a magma chamber, situated at the fissure area, which subsequently erupted as tephra on the glacier. The second phase of the RAMESSES (Reykjanes Ridge Axial Melt Experiment: Structural Synthesis from Electromagnetic and Seismics) experiment involved the acquisition of multichannel seismic reflection data from 39 along- and across-axis lines shot over the magmatically active 57º 45'N axial volcanic ridge. The data from one along-axis line were processed using a variety of techniques that mainly aimed at reducing the large amount of coherent noise present, a result of scattered energy at the rough seabed. The final processed section revealed a number of reflection events that could be interpreted as intra-crustal reflections, originating from the interface between pillow lavas and sheeted dykes, and from the top part of a thin melt lens.
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Tameguri, Takeshi. "Mechanism of explosive eruptions from source mechanism analyses of explosion earthquakes at Sakurajima volcano, Japan." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149986.
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Triastuty, Hetty. "Temporal change in hydrothermal activity inferred from transition of characteristics of volcanic earthquakes at Kuchinoerabujima volcano, Japan." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120668.
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Rodgers, Melanie. "Unusual Patterns of Seismicity during Eruptive and Non-eruptive Periods at the Persistently Restless Telica Volcano, Nicaragua." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4934.
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Telica Volcano, Nicaragua, is a persistently restless volcano with high rates of seismicity that can vary from less than ten events to over a thousand events per day. Low-frequency (LF) events dominate the seismic catalogue and seismicity rates at Telica show little clear correlation with periods of eruption. As such, traditional methods of forecasting of volcanic activity based on increases in seismicity and recognition of LF activity are not applicable. A single seismic station has been operating at Telica since 1993, and in 2010 we installed a broadband seismic and continuous GPS network (TESAND network) at Telica. In this study we investigate the seismic characteristics surrounding a nine-month period of phreatic to phreatomagmatic explosions in 1999, and also from the initial three-and-a-half year deployment of the TESAND network, including a three-month phreatic vulcanian eruptive period in 2011. We demonstrate that pertinent information can be obtained from analysis of single-station data, and while large seismic networks are preferable when possible, we note that for many volcanoes this is not possible. We find unusual patterns of seismicity before both eruptive periods; rather than a precursory increase in seismicity as is observed prior to many volcanic eruptions, we observe a decrease in seismicity many months prior to eruption. We developed a new program for cross-correlation of large seismic data catalogues and analysed multiplet activity surrounding both eruptive periods. We observed that the formation of new multiplets corresponds to periods of high event rates (during inter-eruptive periods) and high percentages of daily events that belong to a multiplet. We propose a model for the seismicity patterns observed at Telica, where changes in seismicity are related to a cyclic transition between open-system degassing and closed-system degassing. Periods of open-system degassing occur during non-eruptive episodes and are characterised by high event rates, a broad range of frequency content of events and high degrees of waveform correlation. A transition to closed-system degassing could be due to sealing of fluid pathways in the magmatic and/or hydrothermal system, or due to magma withdrawal. Periods of closed-system degassing are characterised by low event rates, higher frequency contents and low degrees of waveform correlation. Eruptive periods may then represent a transition from closed-system degassing to open-system degassing, however the system must also be capable of transitioning to open-system degassing without eruption. These observations have important implications for volcano monitoring and eruption forecasting at persistently restless volcanoes. Rather than a precursory increase in seismicity as is often observed prior to eruption at other volcanoes, our observations indicate that phreatic eruptions at Telica occur after a decrease in seismicity, a corresponding change in the frequency content of events, and a decrease in waveform correlation. These changes may represent a period of closed-system degassing that could culminate in phreatic eruptions. The inclusion of real-time analysis of variations in frequency content and multiplet activity provides critical information for volcano monitoring institutions.
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Iguchi, Masato. "A Vertical Expansion Source Model for the Mechanisms of Earthquakes Originated in the Magma Conduit of an Andesitic Volcano : Sakurajima, Japan." 京都大学 (Kyoto University), 1994. http://hdl.handle.net/2433/86447.
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Mattingly, Keith. "Approaching Psychosocial Adaptation to a Post-Crisis Environment through Case Studies of Javanese Disaster Survivors and Refugees in Sweden." Thesis, Uppsala universitet, Teologiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256912.
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The psychosocial well-being of survivors of armed conflicts, forced displacement, and/or natural disasters is becoming more and more an integral component of holistic humanitarian response. Yet many organisations rely on broad, generalised manuals or guidelines which do not take into account the unique characteristics of societies and target populations. This paper describes the author’s research with disaster survivors in Java, Indonesia, and refugee in Sweden, aiming to characterise the process of recovery, adaptation and integration through beneficiaries’ own words. The author looks at how theory can be applied, such as whether a hierarchy of needs can be universally relevant, how the host Swedish society affects refugees’ experiences, which so-called “states of being” subjects experience, and how religion and cultural differences like individualism and collectivism influence one’s ability to regain psychosocial well-being. The author used both in-depth interviews and quantitative questionnaires to obtain data. Results showed an incredible level of resilience and positivity among all groups, though Indonesians reported family, spirituality and the community as major helping factors, while many refugees in Sweden pointed to their own individual determination and will to succeed. Many Indonesians identified economic livelihood as the biggest remaining gap, while refugees in Sweden spoke of language skills, educational qualifications and employment as keys to success and integration. Many challenges and gaps remain, especially for newly arrived refugees facing an increasingly difficult job market and fewer opportunities.
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Lehto, Heather L. "Investigation of Stress Changes at Mount St. Helens, Washington, and Receiver Functions at the Katmai Volcanic Group, Alaska, with an Additional Section on the Assessment of Spreadsheet-based Modules." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4124.
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Forecasting eruptions using volcano seismology is a subject that affects the lives and property of millions of people around the world. However, there is still much to learn about the inner workings of volcanoes and how this relates to the chance of eruption. This dissertation attempts to increase the breadth of knowledge aimed at helping to understand when a volcano is likely to erupt and how large that eruption might be. Chapters 2 and 3 focus on a technique that uses changes in the local stress field beneath a volcano to determine the source of these changes and help forecast eruptions, while Chapter 4 focuses on a technique that shows great potential to be used to image magma chambers beneath volcanoes by using receiver functions.
In Chapters 2 and 3 the source mechanisms of shallow volcano-tectonic earthquakes recorded at Mount St. Helens are investigated by calculating hypocenter locations and fault plane solutions (FPS) for shallow earthquakes recorded during two eruptive periods (1981-1986 and 2004-2008) and two non-eruptive periods (1987-2004 and 2008-2011). FPS show a mixture of normal, reverse, and strike-slip faulting during all periods, with a sharp increase in strike-slip faulting observed in 1987-1997 and an increase in normal faulting between 1998 and 2004 and again on September 25-29, 2004. FPS P-axis orientations (a proxy for ó1) show a ~90° rotation with respect to regional ó1 (N23°E) during 1981-1986 and 2004-2008, bimodal orientations (~N-S and ~E-W) during 1987-2004, and bimodal orientations at ~N-E and ~S-W from 2008-2011. These orientations are believed to be due to pressurization accompanying the shallow intrusion and subsequent eruption of magma as domes during 1981-1986 and 2004-2008, and the buildup of pore pressure beneath a shallow seismogenic volume during 1987-2004 and 2008-2011.
Chapter 4 presents a study using receiver functions, which show the relative response of the Earth beneath a seismometer. Receiver functions are produced by deconvolving the vertical component of a seismogram from the horizontal components. The structure of the ground beneath the seismometer can then be inferred from the arrivals of P-to-S converted phases. Receiver functions were computed for the Katmai Volcanic Group, Alaska, at two seismic stations (KABU and KAKN) between January 2005 and July 2011. Receiver functions from station KABU clearly showed the arrival of the direct P-wave and the arrival from the Moho; however, receiver functions from station KAKN did not show the arrival from the Moho. In addition, changes in the amplitude and polarity of arrivals on receiver functions suggested that the structure beneath both KABU and KAKN was complex. Station KABU is likely underlain by dipping layers and/or anisotropy, while station KAKN may lie over a basin structure, an attenuating body, or some other highly complex structure. However, it is impossible to say for certain what the structure is under either station as the azimuthal coverage is poor and thus the structure is unable to be modeled.
This dissertation also includes a section (Chapter 6) on the assessment of spreadsheet-based modules used in two Introductory Physical Geology courses at the University of South Florida (USF). When faculty at USF began using spreadsheet-based modules to help teach students math and geology concepts the students complained that they spent more time learning how to use Excel than they did learning the concepts presented in the modules. To determine whether the sharp learning curve for Excel was hindering learning we divided the students in two Introductory Physical Geology courses into two groups: one group was given a set of modules which instructed them to use Excel for all calculations; the other group was simply told to complete the calculations but was not instructed what method to use. The results of the study show that whether or not the students used Excel had very little to do with the level of learning they achieved. Despite complaints that Excel was hindering their learning, students in the study attained high gains for both the math and geology concepts presented in the modules whether they used Excel or not.
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Shuler, Ashley Elizabeth. "Investigations of Anomalous Earthquakes at Active Volcanoes." Thesis, 2012. https://doi.org/10.7916/D8ZG70BP.
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This dissertation investigates the link between volcanic unrest and the occurrence of moderate-to-large earthquakes with a specific type of focal mechanism. Vertical compensated-linear-vector-dipole (vertical-CLVD) earthquakes have vertical pressure or tension axes and seismic radiation patterns that are inconsistent with the double-couple model of slip on a planar fault. Prior to this work, moderate-to-large vertical-CLVD earthquakes were known to be geographically associated with volcanic centers and vertical-CLVD earthquakes were linked to a tsunami in the Izu-Bonin volcanic arc and a subglacial fissure eruption in Iceland. Vertical-CLVD earthquakes are some of the largest and most anomalous earthquakes to occur in volcanic systems, yet their physical mechanisms remain controversial largely due to the small number of observations. Five vertical-CLVD earthquakes with vertical pressure axes are identified near Nyiragongo volcano in the Democratic Republic of the Congo. Three earthquakes occur within days of a fissure eruption at Nyiragongo, and two occur several years later in association with the refilling of the lava lake in the summit crater of the volcano. Detailed study of these events shows that the earthquakes have slower source processes than tectonic earthquakes with similar magnitudes and locations. All five earthquakes are interpreted as resulting from slip on inward-dipping ring-fault structures located above deflating shallow magma chambers. The Nyiragongo study supports the interpretation that vertical-CLVD earthquakes may be causally related to dynamic physical processes occurring inside the edifices or magmatic plumbing systems of active volcanoes. Two seismicity catalogs from the Global Centroid Moment Tensor (CMT) Project are used to search for further examples of shallow earthquakes with robust vertical-CLVD focal mechanisms. CMT solutions for approximately 400 target earthquakes are calculated and 86 vertical-CLVD earthquakes are identified near active volcanoes. Together with the Nyiragongo study, this work increases the number of well-studied vertical-CLVD earthquakes from 14 to 101. Vertical-CLVD earthquakes have focal depths in the upper ~10 km of the Earth's crust, and ~80% have centroid locations within 30 km of an active volcanic center. Vertical-CLVD earthquakes are observed near several different types of volcanoes in a variety of geographic and tectonic settings, but most vertical-CLVD earthquakes are observed near basaltic-to-andesitic stratovolcanoes and submarine volcanoes in subduction zones. Vertical-CLVD earthquakes are linked to tsunamis, volcanic earthquake swarms, effusive and explosive eruptions, and caldera collapse, and approximately 70% are associated with documented volcanic eruptions or episodes of volcanic unrest. Those events with vertical pressure axes typically occur after volcanic eruptions initiate, whereas events with vertical tension axes commonly occur before the start of volcanic unrest. Both types of vertical-CLVD earthquakes have longer source durations than tectonic earthquakes of the same magnitude. The isotropic and pure vertical-CLVD components of the moment tensor cannot be independently resolved using our long-period seismic dataset. As a result, several physical mechanisms can explain the retrieved deviatoric vertical-CLVD moment tensors, including dip-slip motion on ring faults, volume exchange between two reservoirs, the opening and closing of tensile cracks, and volumetric sources. An evaluation of these mechanisms is performed using constraints obtained from detailed studies of individual vertical-CLVD earthquakes. Although no single physical mechanism can explain all of the characteristics of vertical-CLVD earthquakes, a ring-faulting model consisting of slip on inward- or outward-dipping ring faults triggered by the inflation or deflation of a shallow magma chamber can account for their seismic radiation patterns and source durations, as well as their temporal relationships with volcanic unrest. The observation that most vertical-CLVD earthquakes are associated with volcanoes with caldera structures supports this interpretation.
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Χαχλιουτάκη, Μαρία-Ελένη. "Η προσέγγιση γεωλογικών φαινομένων στο νηπιαγωγείο : οι ιδέες των παιδιών προσχολικής ηλικίας για τους σεισμούς και τα ηφαίστεια." Thesis, 2014. http://hdl.handle.net/10889/8291.
Full textAbstract:
Οι σεισμοί και οι ηφαιστειακές εκρήξεις αποτελούν την επιφανειακή έκφραση μιας δυναμικής του βάθους. Αυτό από μόνο του παραπέμπει σε κάτι μη απτό και μη άμεσα παρατηρήσιμο. Όμως τα δύο αυτά φαινόμενα καταφέρνουν να κεντρίσουν το ενδιαφέρον μικρών και μεγάλων κάνοντάς τους να σχηματίζουν τις δικές τους παραστάσεις για τις δύο έννοιες. Στην παρούσα έρευνα, μελετήσαμε τις ιδέες που κατέχουν τα παιδιά της προσχολικής ηλικίας για τους σεισμούς, τα ηφαίστεια και τη δημιουργία αυτών, πριν αλλά και μετά από μια οργανωμένη διδακτική παρέμβαση. Επίσης, έγινε προσπάθεια καταγραφής των συναισθημάτων που εκφράζονται από τα παιδιά για το φαινόμενο του σεισμού αλλά και των μέτρων προστασίας που τείνουν να υιοθετούν σε μια τέτοια περίσταση. Το δείγμα αποτέλεσαν 63 παιδιά προσχολικής ηλικίας από ένα δημόσιο Νηπιαγωγείο στην ευρύτερη περιοχή της Πάτρας. Τα παιδιά φάνηκε πως είχαν σχηματίσει ήδη πριν τη διδακτική παρέμβαση κάποιες πρώτες παραστάσεις για τα φαινόμενα αυτά. Μετά την ολοκλήρωση της διδακτικής παρέμβασης παρατηρήθηκε ότι οι παραστάσεις αυτές βελτιώθηκαν αρκετά με κάποιες από αυτές να πλησιάζουν αρκετά το επιστημονικό μοντέλο. Τέλος, τα συναισθήματα που εκφράστηκαν από τα παιδιά καθ’ όλη τη διάρκεια της μελέτης αυτής σχετίζονταν με την κατανόηση της σημαντικότητας του εν λόγω θέματος: παρατηρήθηκε μια μετάβαση από το συναίσθημα φόβου ή πανικού σε συναισθήματα που είχαν να κάνουν περισσότερο με ηρεμία και διατήρηση της ψυχραιμίας προκειμένου να προστατευθούν σε περίπτωση σεισμού.Earthquakes and volcanic eruptions are the surface expression of a dynamic depth. This by itself refers to something intangible and not directly observable; but these two phenomena manage to pique the interest of both preschoolers and adults and make them form their own representations for both concepts. In this research, we studied the ideas held by the preschoolers on earthquakes, volcanoes and the creation of these two, before and after an organized teaching intervention. Also, an attempt was made to record the emotions expressed by children about the earthquakes and the protective measures they tend to adopt in such situations. The sample consisted of 63 preschool children from a public kindergarten located in the city of Patras. Ever before the teaching intervention, children had already formed some early representations for these phenomena, representations that were enriched (approaching even the scientific model) after the didactic intervention had been completed. Finally, the feelings expressed by the children throughout the study resulted from the understanding of the significance of this issue: there was a transition from the feeling of fear or panic to feelings that had more to do with staying calm and keeping their composure (in order to protect themselves) in a case of an earthquake.
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Pesicek, Jeremy D. "High-precision earthquake locations at Great Sitkin Volcano, Andreanof Islands, Alaska, 1999-2005." 2006. http://catalog.hathitrust.org/api/volumes/oclc/71825411.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 2006.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 17-19).
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Xu, Wenbin. "Volcanic and Tectonic Activity in the Red Sea Region (2004-2013): Insights from Satellite Radar Interferometry and Optical Imagery." Diss., 2015. http://hdl.handle.net/10754/556550.
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Studying recent volcanic and tectonic events in the Red Sea region is important for improving our knowledge of the Red Sea plate boundary and for regional geohazard assessments. However, limited information has been available about the past activity due to insufficient in-situ data and remoteness of some of the activity. In this dissertation, I have used satellite remote sensing to derive new information about several recent volcanic and tectonic events in the Red Sea region. I first report on three volcanic eruptions in the southern Red Sea, the 2007-8 Jebel at Tair eruption and the 2011-12 & 2013 Zubair eruptions, which resulted in formation of two new islands. Series of high- resolution optical images were used to map the extent of lava flows and to observe and analyze the growth and destructive processes of the new islands. I used Interferometric Synthetic Aperture Radar (InSAR) data to study the evolution of lava flows, to estimate their volumes, as well as to generate ground displacements maps, which were used to model the dikes that fed the eruptions. I then report on my work of the 2009 Harrat Lunayyir dike intrusion and the 2004 Tabuk earthquake sequence in western Saudi Arabia. I used InSAR observations and stress calculations to study the intruding dike at Harrat Lunayyir, while I combined InSAR data and Bayesian estimation to study the
Tabuk earthquake activity.
The key findings of the thesis are: 1) The recent volcanic eruptions in the southern
Red Sea indicate that the area is magmatically more active than previously acknowledged
and that a rifting episode has been taken place in the southern Red Sea; 2) Stress interactions between an ascending dike intrusion and normal faulting on graben-bounding faults above the dike can inhibit vertical propagation of magma towards the surface; 3) InSAR observations can improve locations of shallow earthquakes and fault model uncertainties are useful to associate earthquake activity with mapped faults; 4). The successful application of satellite remote sensing technologies in studying the recent volcanic and tectonic processes in the Red Sea region implies that remote sensing data
are an important resource for the local authorities to monitor geohazards.
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Nan-TingYen and 顏楠庭. "The Resistivity Change of the Shallow Surface before and after the Earthquake and Rainfall at Gunshuiping Mud Volcano." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/sv43z6.
Full textAbstract:
碩士國立成功大學
地球科學系
105
In order to understand the influence of earthquakes on mud volcanoes, this study used the geophysical method - RIP method to investigate the change of underground electrical properties in this area for about one year, and measured the monthly resistivity of a mud crater to understand the factors, which may affected resistivity. The Gunshuiping Mud Volcano is located in a 175-m × 90-m platform in Southwest of Taiwan. There are four main mud-volcano craters：Craters No.1, 2, 3and 4. In this study, we conducted three survey lines by using the Wenner configuration to obtain the resistivity profile images. The results showed that after Meinong Earthquake, the resistivity rose obviously within about 10 meters under the surface, while the resistivity of the mud horizontal conduits declined. We also found that the original crater (No.3) was stopped and replaced by another crater (No.1) in the scene. We inferred that when the earthquake happened, due to the impact of seismic waves by the earthquake, just as the soda shaken, the gas was hard to be saved in the mud so that it escaped to the surroundings and caused the gas content of the shallow surface to increase. Beside, because the cracks of the original crater collapsed, the gas needed another crack to release so that madeanother crater re-activite. The data show that there was a decrease of resistivity in most areas when there was significant rainfall before the measurement. On the contrary, the resistivity of mud in the dry season may increased slightly due to the water content decreased. However, after the typhoon it showed a different situation with the foresaid: we found the original active crater (No.1) was stopped again and it a new crater (No.4) was in 20 meters outside on site to continue the activity.
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"Mechanical Modeling of Natural and Anthropogenic Fluid-Rock Interactions: Volcano Deformation and Induced Seismicity." Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.51147.
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abstract: The dynamic Earth involves feedbacks between the solid crust and both natural and anthropogenic fluid flows. Fluid-rock interactions drive many Earth phenomena, including volcanic unrest, seismic activities, and hydrological responses. Mitigating the hazards associated with these activities requires fundamental understanding of the underlying physical processes. Therefore, geophysical monitoring in combination with modeling provides valuable tools, suitable for hazard mitigation and risk management efforts. Magmatic activities and induced seismicity linked to fluid injection are two natural and anthropogenic processes discussed in this dissertation.
Successful forecasting of the timing, style, and intensity of a volcanic eruption is made possible by improved understanding of the volcano life cycle as well as building quantitative models incorporating the processes that govern rock melting, melt ascending, magma storage, eruption initiation, and interaction between magma and surrounding host rocks at different spatial extent and time scale. One key part of such models is the shallow magma chamber, which is generally directly linked to volcano’s eruptive behaviors. However, its actual shape, size, and temporal evolution are often not entirely known. To address this issue, I use space-based geodetic data with high spatiotemporal resolution to measure surface deformation at Kilauea volcano. The obtained maps of InSAR (Interferometric Synthetic Aperture Radar) deformation time series are exploited with two novel modeling schemes to investigate Kilauea’s shallow magmatic system. Both models can explain the same observation, leading to a new compartment model of magma chamber. Such models significantly advance the understanding of the physical processes associated with Kilauea’s summit plumbing system with potential applications for volcanoes around the world.
The unprecedented increase in the number of earthquakes in the Central and Eastern United States since 2008 is attributed to massive deep subsurface injection of saltwater. The elevated chance of moderate-large damaging earthquakes stemming from increased seismicity rate causes broad societal concerns among industry, regulators, and the public. Thus, quantifying the time-dependent seismic hazard associated with the fluid injection is of great importance. To this end, I investigate the large-scale seismic, hydrogeologic, and injection data in northern Texas for period of 2007-2015 and in northern-central Oklahoma for period of 1995-2017. An effective induced earthquake forecasting model is developed, considering a complex relationship between injection operations and consequent seismicity. I find that the timing and magnitude of regional induced earthquakes are fully controlled by the process of fluid diffusion in a poroelastic medium and thus can be successfully forecasted. The obtained time-dependent seismic hazard model is spatiotemporally heterogeneous and decreasing injection rates does not immediately reduce the probability of an earthquake. The presented framework can be used for operational induced earthquake forecasting. Information about the associated fundamental processes, inducing conditions, and probabilistic seismic hazards has broad benefits to the society.Dissertation/Thesis
Doctoral Dissertation Geological Sciences 2018
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Pavlacký, Matěj. "Pozdně minojská sídliště opuštěná či zničená následkem santorinské katastrofy." Master's thesis, 2012. http://www.nusl.cz/ntk/nusl-308277.
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This thesis examines Late Minoan Settlements in Crete that were destroyed or abandoned due to the consequences of the Santorini volcano eruption. A summary of geological history of Crete, Thera and the surrounding area is given in the first part. The next chapter sums up the research in the fields of relative and mainly absolute chronology, of which scientists have not yet been able to provide a convincing calendar date for the eruption of the volcano nor a possible fixed absolute chronology of the general Later Bronze Age not only in the Aegean. The development of the Santorini Volcano eruption in the Late Minoan IA period (LM IA) is described. According to the research, this eruption must have caused earthquakes and tsunamis. The possible impact on the near island of Crete, its inhabitants and settlements, mainly in the coastal area of north-northeast part of the island, is also discussed.