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Journal articles on the topic 'Seismic moment tensor'

Author: Grafiati

Published: 4 June 2021

Last updated: 14 February 2022

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1

Ford, Sean R., Gordon D. Kraft, and Gene A. Ichinose. "Seismic moment tensor event screening." Geophysical Journal International 221, no. 1 (January 6, 2020): 77–88. http://dx.doi.org/10.1093/gji/ggz578.

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SUMMARY Event screening is an explosion monitoring practice that aims to identify an event as an explosion (‘screened in’) or not (‘screened out’). Confidence in event screening can be increased if multiple independent approaches are used. We describe a new approach to event screening using the seismic moment tensor and its representation on the hypersphere, specifically the 5-sphere of 6-degree unit vectors representing the normalized symmetric moment tensor. The sample of moment tensors from an explosion data set is unimodal on the 5-sphere and can be parametrized by the Langevin distribution, which is sometimes referred to as the Normal distribution on the hypersphere. Screening is then accomplished by finding the angle from the explosion population mean to any newly measured moment tensor and testing if that angle is in the tail of the Langevin distribution (conservatively quantified as greater than 99.9 per cent of the cumulative density). We apply the screen to a sample of earthquakes from the Western USA and the September 2017 explosion and subsequent collapse at the Pungyye-Ri Test Site in North Korea. All the earthquakes and the collapse screen out, but the explosion does not.

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2

Ahmed, Omar Qadir. "Earthquake Moment Tensor Analysis Using Broadband Seismic Waveforms." Journal of Zankoy Sulaimani - Part A 20, no. 3&4 (December 6, 2018): 49–56. http://dx.doi.org/10.17656/jzs.10734.

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3

Zhu, Lupei, and Yehuda Ben-Zion. "Parametrization of general seismic potency and moment tensors for source inversion of seismic waveform data." Geophysical Journal International 194, no. 2 (April 29, 2013): 839–43. http://dx.doi.org/10.1093/gji/ggt137.

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Abstract We decompose a general seismic potency tensor into isotropic tensor, double-couple tensor and compensated linear vector dipole using the eigenvectors and eigenvalues of the full tensor. Two dimensionless parameters are used to quantify the size of the isotropic and compensated linear vector dipole components. The parameters have well-defined finite ranges and are suited for non-linear inversions of source tensors from seismic waveform data. The decomposition and parametrization for the potency tensor are used to obtain corresponding results for a general seismic moment tensor. The relations between different parameters of the potency and moment tensors in isotropic media are derived. We also discuss appropriate specification of the relative size of different source components in inversions of seismic data.

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4

Diner, Çağrı. "The Structure of Moment Tensors in Transversely Isotropic Focal Regions." Bulletin of the Seismological Society of America 109, no. 6 (September 24, 2019): 2415–26. http://dx.doi.org/10.1785/0120180316.

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Abstract Full moment tensor inversion has become a standard method for understanding the mechanisms of earthquakes as the resolution of the inversion process increases. Thus, it is important to know the possible forms of non–double‐couple (non‐DC) moment tensors, which can be obtained because of either the different source mechanisms or the anisotropy of the focal regions. In this study, the form of the moment tensors of seismic sources occurring in transversely isotropic (TI) focal regions is obtained using the eigendecomposition of the elasticity tensor. More precisely, a moment tensor is obtained as a linear combination of the eigenspaces of TI elasticity tensor in which the coefficients of the terms are the corresponding eigenvalues multiplied with the projection of the potency tensor onto the corresponding eigenspaces. Moreover, the eigendecomposition method is also applied to obtain the three different forms of moment tensors in isotropic focal regions, in particular, for the shear source, tensile source, and for any type of potency tensor whose rank is three. This linear algebra point of view makes the structure of the moment tensors more apparent; for example, a shear source tensor is an eigenvector of isotropic elasticity tensor, and hence the resulting moment tensor is proportional to its shear source tensor. Moreover, a geometric interpretation for the scalar seismic moment, which is the norm of the moment tensor, for anisotropic focal regions is achieved through the eigendecomposition method. This method also gives a simple way to quantify the percentage of the isotropic component of the moment tensor of shear sources in TI focal regions. Hence, the complexities in the moment tensor introduced by the anisotropy of the focal region and by the source mechanism can be differentiated.

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5

Jost, M. L., and R. B. Herrmann. "A Student’s Guide to and Review of Moment Tensors." Seismological Research Letters 60, no. 2 (April 1, 1989): 37–57. http://dx.doi.org/10.1785/gssrl.60.2.37.

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Abstract A review of a moment tensor for describing a general seismic point source is presented to show a second order moment tensor can be related to simpler seismic source descriptions such as centers of expansion and double couples. A review of literature is followed by detailed algebraic expansions of the moment tensor into isotropic and deviatoric components. Specific numerical examples are provided in the appendices for use in testing algorithms for moment tensor decomposition.

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6

Dammeier, Franziska, Aurélie Guilhem, Jeffrey R. Moore, Florian Haslinger, and Simon Loew. "Moment Tensor Analysis of Rockslide Seismic Signals." Bulletin of the Seismological Society of America 105, no. 6 (November 10, 2015): 3001–14. http://dx.doi.org/10.1785/0120150094.

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7

Willemann, Raymond J. "Cluster analysis of seismic moment tensor orientations." Geophysical Journal International 115, no. 3 (December 1993): 617–34. http://dx.doi.org/10.1111/j.1365-246x.1993.tb01484.x.

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8

Kagan, Y. Y., and L. Knopoff. "The first-order statistical moment of the seismic moment tensor." Geophysical Journal International 81, no. 2 (May 1, 1985): 429–44. http://dx.doi.org/10.1111/j.1365-246x.1985.tb06411.x.

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9

Donner, S., M. Mustać, B. Hejrani, H. Tkalčić, and H. Igel. "Seismic moment tensors from synthetic rotational and translational ground motion: Green’s functions in 1-D versus 3-D." Geophysical Journal International 223, no. 1 (June 30, 2020): 161–79. http://dx.doi.org/10.1093/gji/ggaa305.

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SUMMARY Seismic moment tensors are an important tool and input variable for many studies in the geosciences. The theory behind the determination of moment tensors is well established. They are routinely and (semi-) automatically calculated on a global scale. However, on regional and local scales, there are still several difficulties hampering the reliable retrieval of the full seismic moment tensor. In an earlier study, we showed that the waveform inversion for seismic moment tensors can benefit significantly when incorporating rotational ground motion in addition to the commonly used translational ground motion. In this study, we test, what is the best processing strategy with respect to the resolvability of the seismic moment tensor components: inverting three-component data with Green’s functions (GFs) based on a 3-D structural model, six-component data with GFs based on a 1-D model, or unleashing the full force of six-component data and GFs based on a 3-D model? As a reference case, we use the inversion based on three-component data and 1-D structure, which has been the most common practice in waveform inversion for moment tensors so far. Building on the same Bayesian approach as in our previous study, we invert synthetic waveforms for two test cases from the Korean Peninsula: one is the 2013 nuclear test of the Democratic People’s Republic of Korea and the other is an Mw 5.4 tectonic event of 2016 in the Republic of Korea using waveform data recorded on stations in Korea, China and Japan. For the Korean Peninsula, a very detailed 3-D velocity model is available. We show that for the tectonic event both, the 3-D structural model and the rotational ground motion, contribute strongly to the improved resolution of the seismic moment tensor. The higher the frequencies used for inversion, the higher is the influence of rotational ground motions. This is an important effect to consider when inverting waveforms from smaller magnitude events. The explosive source benefits more from the 3-D structural model than from the rotational ground motion. Nevertheless, the rotational ground motion can help to better constraint the isotropic part of the source in the higher frequency range.

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10

Savage, J. C., and R. W. Simpson. "Surface strain accumulation and the seismic moment tensor." Bulletin of the Seismological Society of America 87, no. 5 (October 1, 1997): 1345–53. http://dx.doi.org/10.1785/bssa0870051345.

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Abstract Although the scalar moment accumulation rate within the seismogenic zone beneath a given area is sometimes deduced from the observed average surface strain accumulation rate over that same area (e.g., Working Group on California Earthquake Probabilities, 1995), the correspondence between the two is very uncertain. The equivalence between surface strain accumulation and scalar moment accumulation is based on Kostrov's (1974) relation between the average strain rate over a volume and the moment-rate tensor for that volume. The average strain rate over the volume is replaced by the average strain rate measured at the free surface to deduce an approximate moment-rate tensor. Only in exceptional circumstances will that moment-rate tensor correspond to a double-couple mechanism, a mechanism that can be represented by a scalar moment accumulation rate. More generally, the moment tensor must be resolved into the superposition of two or more double-couple mechanisms, and that resolution can be done in many ways, each with its own scalar moment rate. Thus the resolution is not unique. This is demonstrated by deducing scalar moment accumulation rates for a GPS network that covers most of California south of San Francisco. It is shown that resolutions into different double-couple mechanisms lead to scalar moment accumulation rates differing by factors of ∼2. We suggest that the minimum scalar moment rate equivalent to principal surface strain rates ɛ1 and ɛ2 acting over the area A is M0(min) = 2μHA Max (¦ɛ1¦, ¦ɛ2¦, ¦ɛ1 + ɛ2¦), where μ is the rigidity and H the depth of seismogenic zone, and the function Max is equal to the largest of its arguments. Within the uncertainites of measurement, the scalar moment accumulation rate in southern California based on that approximation is in balance with the average historic seismic moment release rate so that no current earthquake deficit need be accumulating.

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11

Dufumier, Hugues, and Jeannot Trampert. "Contribution of seismic tomography in moment-tensor inversions using teleseismic surface-wave spectra." Bulletin of the Seismological Society of America 87, no. 1 (February 1, 1997): 114–22. http://dx.doi.org/10.1785/bssa0870010114.

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Abstract The knowledge of lateral heterogeneities is crucial for path corrections in moment tensor inversions using surface waves. After some attempts to use regionalized Earth models for very long-period surface-wave moment-tensor inversions, recent tomographic Earth models offer the possibility to make short-period path corrections and therefore retrieve more reliable moment tensors for teleseismic earthquakes. First we try to evaluate the precision required for path corrections in comparison with source effects. Some selected Earth models are tested to evaluate how their results compare to those using multiple-frequency filtering techniques. Some real cases illustrate the sensitivity of moment-tensor solutions to the different path corrections, and it appears clearly that regionalized Earth models and tomographic models deduced from long-period data alone (greater than 150 sec) cannot lead to trustworthy broadband moment-tensor inversions. Recent tomographic models using phase velocities at much shorter periods (40 to 200 sec) offer a precision comparable to that of the multiple-frequency filtering technique. Both methods lead to acceptable source mechanisms, using a small number of stations, in more than two cases out of three. The use of recent global tomographic models based upon shorter-period surface waves might thus be a useful alternative to heavy multiple-frequency filtering techniques to automate source studies, especially for rapid determinations using a small number of stations.

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12

Day, Steven M., and Keith L. McLaughlin. "Seismic source representations for spall." Bulletin of the Seismological Society of America 81, no. 1 (February 1, 1991): 191–201. http://dx.doi.org/10.1785/bssa0810010191.

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Abstract Spall may be a significant secondary source of seismic waves from underground explosions. The proper representation of spall as a seismic source is important for forward and inverse modeling of explosions for yield estimation and discrimination studies. We present a new derivation of a widely used point force representation for spall, which is based on a horizontal tension crack model. The derivation clarifies the relationship between point force and moment tensor representations of the tension crack. For wavelengths long compared with spall depth, the two representations are equivalent, and the moment tensor time history is proportional to the doubly integrated time history of the point force. Numerical experiments verify that, for regional seismic phases, this equivalence is valid for all frequencies for which the point-source (long wavelength) approximation is valid. Further analysis shows that the moment tensor and point force representations retain their validity for nonplanar spall surfaces, provided that the average dip of the surface is small. The equivalency of the two representations implies that a singular inverse problem will result from attempts to infer simultaneously the spectra of both of these source terms from seismic waveforms. If the spall moment tensor alone is estimated by inversion of waveform data, the inferred numerical values of its components will depend inversely upon the source depth that is assumed in the inversion formalism.

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13

Abreu, Rafael, Stephanie Durand, and Christine Thomas. "The Asymmetric Seismic Moment Tensor in Micropolar Media." Bulletin of the Seismological Society of America 108, no. 3A (April 24, 2018): 1160–70. http://dx.doi.org/10.1785/0120170243.

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14

Xu, Yan, Keith D. Koper, Relu Burlacu, Robert B. Herrmann, and Dan-Ning Li. "A New Uniform Moment Tensor Catalog for Yunnan, China, from January 2000 through December 2014." Seismological Research Letters 91, no. 2A (February 5, 2020): 891–900. http://dx.doi.org/10.1785/0220190242.

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Abstract Because of the collision of the Indian and Eurasian tectonic plates, the Yunnan Province of southwestern China has some of the highest levels of seismic hazard in the world. In such a region, a catalog of moment tensors is important for estimating seismic hazard and helping understand the regional seismotectonics. Here, we present a new uniform catalog of moment tensor solutions for the Yunnan region. Using a grid-search technique to invert seismic waveforms recorded by the permanent regional network in Yunnan and the 2 yr ChinArray deployment, we present 1833 moment tensor solutions for small-to-moderate earthquakes that occurred between January 2000 and December 2014. Moment magnitudes in the new catalog vary from Mw 2.2 to 6.1, and the catalog is complete above Mw∼3.5–3.6. The moment tensors are constrained to be purely double-couple and show a variety of faulting mechanisms. Normal faulting events are mainly concentrated in northwest Yunnan, while farther south along the Sagaing fault the earthquakes are mostly thrust and strike slip. The remaining area includes all three styles of faulting but mostly strike slip. We invert the moment tensors for the regional stress field and find a strong correlation between spatially varying maximum horizontal stress and Global Positioning System observations of horizontal ground velocity. The stress field reveals clockwise rotation around the eastern Himalayan syntaxis, with northwest–southeast compression to the east of the Red River fault changing to northeast–southwest compression west of the fault. Almost 88% of the centroid depths are shallower than 16 km, consistent with a weak and ductile lower crust.

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15

Bai, Qipeng, Sidao Ni, Risheng Chu, and Zhe Jia. "gCAPjoint, A Software Package for Full Moment Tensor Inversion of Moderately Strong Earthquakes with Local and Teleseismic Waveforms." Seismological Research Letters 91, no. 6 (August 19, 2020): 3550–62. http://dx.doi.org/10.1785/0220200031.

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Abstract Earthquake moment tensors and focal depths are crucial to assessing seismic hazards and studying active tectonic and volcanic processes. Although less powerful than strong earthquakes (M 7+), moderately strong earthquakes (M 5–6.5) occur more frequently and extensively, which can cause severe damages in populated areas. The inversion of moment tensors is usually affected by insufficient local waveform data (epicentral distance <5°) in sparse seismic networks. It would be necessary to combine local and teleseismic data (epicentral distance 30°–90°) for a joint inversion. In this study, we present the generalized cut-and-paste joint (gCAPjoint) algorithm to jointly invert full moment tensor and centroid depth with local and teleseismic broadband waveforms. To demonstrate the effectiveness and explore the limitations of this algorithm, we perform case studies on three earthquakes with different tectonic settings and source properties. Comparison of our results with global centroid moment tensor and other catalog solutions illustrates that both non-double-couple compositions of the focal mechanisms and centroid depths can be reliably recovered for very shallow (<10 km) earthquakes and intermediate-depth events with this software package.

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16

Foulger, Gillian R., and Bruce R. Julian. "Earthquakes and errors: Methods for industrial applications." GEOPHYSICS 76, no. 6 (November 2011): WC5—WC15. http://dx.doi.org/10.1190/geo2011-0096.1.

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The high accuracies and realistic confidence assessments demanded for seismic monitoring of hydraulic fracturing work require specialist experimental approaches. These include seismic network design based on quantitative modeling, high-quality instrument deployments, and accurate and detailed crustal models. Confidence estimates must take into account uncertainties about crustal structure, which may dominate error budgets. Earthquake size should be expressed in terms of scalar seismic moment or the associated moment magnitude [Formula: see text], which is related to fundamental physical source processes, and not as traditional earthquake magnitudes. Representing earthquake mechanisms in terms of seismic moment tensors allows for processes such as volume changes and complex types of shearing that are important in hydrocarbon and geothermal reservoirs. Traditional fault-plane solutions are based on simplifying assumptions such as shear slip on a planar faults, and isotropic crustal structures, which may introduce large uncertainties. Quantitative assessment of confidence regions for moment-tensor source mechanisms, a newly emerging field, is important for distinguishing computational artifacts from real physical phenomena. We review methods currently available for realistic error estimation for earthquake locations and moment tensors, with particular emphasis on surface sensor arrays in geothermal areas.

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17

Minakov, Alexander, and Viktoriya Yarushina. "Elastoplastic source model for microseismicity and acoustic emission." Geophysical Journal International 227, no. 1 (May 31, 2021): 33–53. http://dx.doi.org/10.1093/gji/ggab207.

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SUMMARY The microseismic events can often be characterized by a complex non-double couple source mechanism. Recent laboratory studies recording the acoustic emission during rock deformation help connecting the components of the seismic moment tensor with the failure process. In this complementary contribution, we offer a mathematical model which can further clarify these connections. We derive the seismic moment tensor based on classical continuum mechanics and plasticity theory. The moment tensor density can be represented by the product of elastic stiffness tensor and the plastic strain tensor. This representation of seismic sources has several useful properties: (i) it accounts for incipient faulting as a microseismicity source mechanism, (ii) it does not require a pre-defined fracture geometry, (iii) it accounts for both shear and volumetric source mechanisms, (iv) it is valid for general heterogeneous and anisotropic rocks and (v) it is consistent with elasto-plastic geomechanical simulators. We illustrate the new approach using 2-D numerical examples of seismicity associated with cylindrical openings, analogous to wellbore, tunnel or fluid-rich conduit and provide a simple analytic expression of the moment density tensor. We compare our simulation results with previously published data from laboratory and field experiments. We consider four special cases corresponding to ‘dry’ elastically homogeneous and elastically heterogeneous isotropic rocks, ‘dry’ transversely isotropic rocks and ‘wet’ isotropic rocks. The model highlights theoretical links between stress state, geomechanical parameters and conventional representations of the moment tensor such as Hudson source type parameters.

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18

Rösler, Boris, and Suzan van der Lee. "Using Seismic Source Parameters to Model Frequency-Dependent Surface-Wave Radiation Patterns." Seismological Research Letters 91, no. 2A (January 2, 2020): 992–1002. http://dx.doi.org/10.1785/0220190128.

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Abstract The excitation of surface waves depends on the frequency-dependent eigenfunctions of the Earth, which are determined numerically. As a consequence, radiation patterns of Rayleigh and Love waves cannot be calculated analytically and vary with source depth and with frequency. Owing to the importance of surface-wave amplitudes for inversions of source processes as well as studies of the elastic and anelastic structure of the Earth, assessing surface-wave radiation patterns for different source mechanisms is desirable. A data product developed in collaboration with the Incorporated Research Institutions for Seismology (IRIS) Consortium provides visualizations of the radiation patterns for Rayleigh and Love waves for all possible source mechanisms. Radiation patterns for known earthquakes are based on the moment tensors reported by the Global Centroid Moment Tensor project. These source mechanisms can be modified or moment tensor components can be chosen by the user to assess their effect on Rayleigh- and Love-wave radiation patterns.

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19

Bowers, David, and John A. Hudson. "Defining the scalar moment of a seismic source with a general moment tensor." Bulletin of the Seismological Society of America 89, no. 5 (October 1, 1999): 1390–94. http://dx.doi.org/10.1785/bssa0890051390.

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Abstract We compare several published definitions of the scalar moment M0, a measure of the size of a seismic disturbance derived from the second-order seismic moment tensor M (with eigenvalues m1 ≥ m3 ≥ m2). While arbitrary, a useful definition is in terms of a total moment, MT0 = MI + MD, where MI = |M|, with M = (m1 + m2 + m3)/3, is the isotropic moment, and MD = max(|mj − M|; j = 1, 2, 3), is the deviatoric moment. This definition is consistent with other definitions of M0 if M is a double couple. This definition also gives physically appealing and simple results for the explosion and crack sources. Furthermore, our definitions of MT0, MI and MD are in accord with the parameterization of the moment tensor into a deviatoric part (represented by T which lies in [−1,1]) and a volumetric part (represented by k which lies in [−1, 1]) proposed by Hudson et al. (1989).

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20

FUKUYAMA, Eiichi, Mizuho ISHIDA, Douglas S. DREGER, and Hiroyuki KAWAI. "Automated Seismic Moment Tensor Determination by Using On-line Broadband Seismic Waveforms." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 51, no. 1 (1998): 149–56. http://dx.doi.org/10.4294/zisin1948.51.1_149.

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21

Rueda, J., and J. Mezcua. "Near-real-time Seismic Moment-tensor Determination in Spain." Seismological Research Letters 76, no. 4 (July 1, 2005): 455–65. http://dx.doi.org/10.1785/gssrl.76.4.455.

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22

Mochizuki, Eiji. "Seismic Excitation by Single Force and Asymmetric Moment Tensor." Journal of Physics of the Earth 43, no. 1 (1995): 45–57. http://dx.doi.org/10.4294/jpe1952.43.45.

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23

Pugh, D. J., and R. S. White. "MTfit: A Bayesian Approach to Seismic Moment Tensor Inversion." Seismological Research Letters 89, no. 4 (May 16, 2018): 1507–13. http://dx.doi.org/10.1785/0220170273.

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24

Kawakatsu, Hitoshi, and Jean-Paul Montagner. "Time-reversal seismic-source imaging and moment-tensor inversion." Geophysical Journal International 175, no. 2 (November 2008): 686–88. http://dx.doi.org/10.1111/j.1365-246x.2008.03926.x.

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25

Krieger, L., and S. Heimann. "MoPaD--Moment Tensor Plotting and Decomposition: A Tool for Graphical and Numerical Analysis of Seismic Moment Tensors." Seismological Research Letters 83, no. 3 (May 1, 2012): 589–95. http://dx.doi.org/10.1785/gssrl.83.3.589.

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26

Bonita, Jun D., Hiroyuki Kumagai, and Masaru Nakano. "Regional Moment Tensor Analysis in the Philippines: CMT Solutions in 2012–2013." Journal of Disaster Research 10, no. 1 (February 1, 2015): 18–24. http://dx.doi.org/10.20965/jdr.2015.p0018.

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Recently, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) has upgraded its seismic network, equipping it with accelerometers and broadband seismometers for intensity and focal mechanism determinations. As part of this upgrade, PHIVOLCS adapted the use of a source analysis system called SWIFT to determine the centroid moment tensor (SWIFT CMT). SWIFT CMT solutions were estimated for medium to large size earthquakes (4.1 ≤Mw≤ 7.6) in the Philippines for the period of January 2012 to November 2013 and were statistically evaluated with respect to the CMT solutions of the Global Centroid Moment Tensor (GCMT) Project. The seismic moments, moment magnitudes, centroid locations, depths and focal mechanisms of most of the SWIFT CMT solutions are found to be consistent to those of the GCMT solutions for earthquakes withMw≥ 4.6. The SWIFT system with the new broadband seismographic network provides more CMT solutions for moderate size earthquakes (Mw≥ 4.1) than GCMT. SWIFT proves to be useful in the development of the Philippines CMT catalogue that will lead to a better understanding of seismotectonics in the Philippines.

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27

Linzer, Lindsay M., Mark W. Hildyard, and Johan Wesseloo. "Complexities of underground mining seismic sources." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2196 (March 15, 2021): 20200134. http://dx.doi.org/10.1098/rsta.2020.0134.

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This paper presents a numerical investigation on the influence of the mining environment on seismic sources, with a focus on pillar failure mechanisms in tabular mining. We investigate the influence of the mining stope (underground excavation or void) on seismic inversions for the scalar moment, corner frequency, source radius, stress drop and moment tensor using synthetic events created within elastodynamic numerical modelling software, WAVE3D. The main objective is to determine whether the source parameters calculated from the recorded waveforms are due to a combination of the stope source and the pillar sources, rather than being related only to crushing of the pillar or shearing in the pillar footwall. The main finding is that the presence of stopes, and types of pillars, have a significant impact on the seismic moment and other source parameters. This is important since the moment is viewed as a robust parameter on which seismic magnitude is often based; however, this study indicates that moments calculated for pillar failure in a tabular stoping environments are less representative of the shearing or crushing source than originally thought. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

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28

Triantafyllis, N., E. Sokos, and A. Ilias. "Automatic moment tensor determination for the Hellenic Unified Seismic Network." Bulletin of the Geological Society of Greece 47, no. 3 (December 21, 2016): 1308. http://dx.doi.org/10.12681/bgsg.10912.

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Modern seismic networks with broadband sensors and real time digital telemetry made Moment Tensor (MT) determination a routine procedure. Automatic MT’s are now provided by global networks and a few very dense regional networks, within minutes after a significant event. An automatic MT determination wasn’t possible for the broader Hellenic area since seismic station density wasn’t sufficient. The creation of the Hellenic Unified Seismic Network (HUSN) provided the opportunity to apply an automated MT procedure using the available broad band data from almost one hundred stations. Thus the ISOLA code was extended towards the automatic operation based on Linux OS shell scripts, stand alone Fortran codes and SAC2000. Software supports both manual and automatic mode; at the first case, the user manually runs the program with the desired input parameters while at the latter, the system monitors a mailbox or RSS feed and if it receives an appropriate notification triggers the MT inversion procedure based on certain conditions. As it is setup now it calculates automatically the moment tensor of earthquakes larger than 3.5M w using data from HUSN. Application of an automated MT inversion procedure for HUSN will provide important real time information for studies like ground motion evaluation, tsunami warning etc.

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29

Boitz, Nepomuk, Anton Reshetnikov, and Serge A. Shapiro. "Visualizing effects of anisotropy on seismic moments and their potency-tensor isotropic equivalent." GEOPHYSICS 83, no. 3 (May 1, 2018): C85—C97. http://dx.doi.org/10.1190/geo2017-0442.1.

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Radiation patterns of earthquakes contain important information on tectonic strain responsible for seismic events. However, elastic anisotropy may significantly impact these patterns. We systematically investigate and visualize the effect of anisotropy on the radiation patterns of microseismic events. For visualization, we use a vertical-transverse-isotropic (VTI) medium. We distinguish between two different effects: the anisotropy in the source and the anisotropy on the propagation path. Source anisotropy mathematically comes from the matrix multiplication of the anisotropic stiffness tensor with the source strain expressed by the potency tensor. We analyze this effect using the corresponding radiation pattern and the moment tensor decomposition. Propagation anisotropy mathematically comes from the deviation between the polarization and the propagation direction of a quasi P-wave in an anisotropic medium. We investigate both effects separately by either assuming the source to be anisotropic and the propagation to be isotropic or vice versa. We find that both effects have a significant impact on the radiation pattern of a pure-slip source. Finally, we develop an alternative visualization of source mechanisms by plotting beach balls proportional to their potency tensors. For this, we multiply the potency tensor with an isotropic elasticity tensor having the equivalent shear modulus [Formula: see text] and [Formula: see text]. In this way, we visualize the tectonic deformation in the source, independently of the rock anisotropy.

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30

Krizova, D., J. Zahradnik, and A. Kiratzi. "Resolvability of Isotropic Component in Regional Seismic Moment Tensor Inversion." Bulletin of the Seismological Society of America 103, no. 4 (July 31, 2013): 2460–73. http://dx.doi.org/10.1785/0120120097.

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31

Kagan, Y. Y., and L. Knopoff. "The two-point correlation function of the seismic moment tensor." Geophysical Journal International 83, no. 3 (December 1, 1985): 637–56. http://dx.doi.org/10.1111/j.1365-246x.1985.tb04330.x.

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32

Jordan, Thomas H., and Alan Juarez. "Representation of complex seismic sources by orthogonal moment-tensor fields." Geophysical Journal International 216, no. 3 (November 21, 2018): 1867–89. http://dx.doi.org/10.1093/gji/ggy492.

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Vavryčuk, Václav. "Is the seismic moment tensor ambiguous at a material interface?" Geophysical Journal International 194, no. 1 (April 10, 2013): 395–400. http://dx.doi.org/10.1093/gji/ggt084.

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Oncescu, Mihnea Corneliu. "Relative seismic moment tensor determination for Vrancea intermediate depth earthquakes." Pure and Applied Geophysics PAGEOPH 124, no. 4-5 (1986): 931–40. http://dx.doi.org/10.1007/bf00879619.

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Jordan, Thomas H., and Alan Juarez. "Stress–strain characterization of seismic source fields using moment measures of mechanism complexity." Geophysical Journal International 227, no. 1 (June 5, 2021): 591–616. http://dx.doi.org/10.1093/gji/ggab218.

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SUMMARY Earthquake ruptures and seismic sequences can be very complex, involving slip in various directions on surfaces of variable orientation. How is this geometrical complexity in seismic energy release, here called mechanism complexity, governed by tectonic stress? We address this question using a probabilistic model for the distribution of double couples that is consistent with three assumptions commonly used in regional stress inversions: the tectonic stress is constant, slip vectors are aligned with the maximum shear traction in the plane of slip, and higher shear traction promotes more seismic energy release. We characterize the moment-tensor field of a stress-aligned source process in terms of an ordered set of principal-stress directions, a stress shape factor R, and a strain-sensitivity parameter $\kappa $. The latter governs the dependence of the seismic moment density on the shear-traction magnitude and therefore parametrizes the seismic strain response to the driving stress. These stress–strain characterization (SSC) parameters can be determined from moment measures of mechanism complexity observed in large earthquakes and seismic sequences. The moment measures considered here are the ratio of the Aki moment to the total seismic moment and the five fractions of the total-moment defined by linear mappings of the moment-tensor field onto an orthonormal basis of five deviatoric mechanisms. We construct this basis to be stress-oriented by choosing its leading member to be the centroid moment tensor (CMT) mechanism and three others representing orthogonal rotations of the CMT mechanism. From the projections of the stress-aligned field onto this stress-oriented basis, we derive explicit expressions for the expected values of the moment-fraction integrals as functions of R and $\kappa $. We apply the SSC methodology to a 39-yr focal mechanism catalogue of the San Jacinto Fault (SJF) zone and to realizations from the Graves–Pitarka stochastic rupture model. The SJF data are consistent with the SSC model, and the recovered parameters, $R = {\rm{ }}0.45 \pm 0.050$ and $\kappa = {\rm{ }}5.7 \pm 1.75$, indicate moderate mechanism complexity. The parameters from the Graves–Pitarka realizations, $R = {\rm{\ }}0.49 \pm 0.005,{\rm{\ \ }}\kappa = {\rm{\ }}9.5 \pm 0.375,$ imply lower mechanism complexity than the SJF catalogue, and their moment measures show inconsistencies with the SSC model that can be explained by differences in the modelling assumptions.

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Grechka, Vladimir, Zhao Li, Bo Howell, and Václav Vavryčuk. "Single-well moment tensor inversion of tensile microseismic events." GEOPHYSICS 81, no. 6 (November 2016): KS219—KS229. http://dx.doi.org/10.1190/geo2016-0186.1.

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Microseismic data acquired in a single observation well parallel to the axis of rotational symmetry of surrounding rocks — typically, in a vertical well drilled through a horizontally layered isotropic or vertically transversely isotropic formation — cannot be uniquely inverted for six independent components comprising the full seismic moment tensor. To constrain the inversion for such a survey geometry and medium symmetry, one might assume certain physical properties of seismic sources, the properties relating otherwise independent moment components to each other, regularizing moment tensor inversion, and helping reduce its ambiguity. Our paper examines one possibility of this kind: the assumption of a tensile fracture, rupturing the focal region along a plane of its greatest weakness. Mathematical formulation of inversion of single-well microseismic records for the parameters of tensile fractures reveals that the true solution, always recoverable from properly acquired data, might be accompanied by two spurious solutions. The analysis of those solutions leads to a criterion that, although not perfect, makes it possible to select the correct solution for the majority of elastic models. After being tested on synthetic, our methodology is applied to a field data set recorded with multiple vertical downhole arrays, demonstrating that the results of dual-well moment tensor inversion can be replicated with single-well data.

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Yao, Yi, and Yibo Wang. "Seismic radiation analyses in anisotropic media based on general dislocation source model." Journal of Geophysics and Engineering 18, no. 2 (April 2021): 231–40. http://dx.doi.org/10.1093/jge/gxab006.

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Abstract Anisotropy affects the focal mechanism and makes it complicated. A shear motion generates a pure double-couple (DC) source in isotropic media. While in anisotropic media, it will produce non-DC components, which contain isotropic (ISO) and compensated linear vector dipole (CLVD) components. Besides, coupled with the diversity of fault motion, the source may become extremely complicated. In this paper, the seismic moment tensor is obtained based on the dislocation model, and then a variety of analyses are performed with the moment tensor, including moment tensor decomposition, radiation pattern, radiated energy ratio and seismic propagation characteristics. Since the anisotropy of the medium also influences seismic wave propagation, a hypothesis is made that the source region is minimal and anisotropic, but the propagation path is isotropic. The research gives some interesting conclusions. It is found that the anisotropy mainly affects the focal mechanism under low slope angle while high slope angle has little effect on the polarity. In terms of the moment tensor decomposition, if only one of ISO or CLVD exists, it can be asserted that the source region is anisotropic because ISO components are accompanied by CLVD components in isotropy media. As for the DC component, the results indicate it is one of the most important factors for determining the ratio of radiant energy. This paper presents some valuable findings of the focal mechanism of the general dislocation source under anisotropy, which helps to recognise the source characteristics of the earthquake and build solid foundations for the subsequent inversion of the focal mechanism.

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Kwiatek, Grzegorz, T. H. W. Goebel, and Georg Dresen. "Seismic moment tensor andbvalue variations over successive seismic cycles in laboratory stick-slip experiments." Geophysical Research Letters 41, no. 16 (August 20, 2014): 5838–46. http://dx.doi.org/10.1002/2014gl060159.

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39

Agalos, A., P. Papadimitriou, N. Voulgaris, and K. Makropoulos. "Source parameters estimation from broadband regional seismograms for earthquakes in the Aegean region and the Gorda plate." Bulletin of the Geological Society of Greece 40, no. 3 (June 5, 2018): 1032. http://dx.doi.org/10.12681/bgsg.16795.

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Seismic moment tensors are estimated for earthquakes offshore Northern California and Greece using inversion of regionally recorded broadband seismograms. This study includes inversion results for the strongest events that occurred inside the Gorda plate and near the Mendocino triple junction from 1991 to 2005. The regional results are in good agreement with obtained teleseismic results. We finally applied the moment tensor inversion methodology and validation mainly to moderate sized earthquakes, with magnitude greater than M~4.0, in the Aegean area. The focal mechanisms of HI earthquakes that occurred during the time period between June 2003 and March 2007 were estimated using this procedure.

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Yunga, S., A. Lutikov, and O. Molchanov. "Non double couple seismic sources, faults interaction and hypothesis of self-organized criticality." Natural Hazards and Earth System Sciences 5, no. 1 (January 3, 2005): 11–15. http://dx.doi.org/10.5194/nhess-5-11-2005.

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Abstract. Non double couple (NDC) sources are considered in framework of the hypothesis that the process of seismic rupture can be viewed as a result of complicated fault geometry and its segmentation. Analytical approach is found to reveal reliability of NDC measure taking into consideration the values of seismic moment tensor errors. The study focuses on the comparison of the deformation modes of the NDC sources with the stress states in its vicinity. The deformation modes of faulting and fracturing at a small scale in NDC earthquake focus and at regional scale in geological unit were investigated using at the last case summation of seismic moment tensors. These local and regional deformation modes in some of geodynamic regimes confirm the self-similarity assumption. For the whole data set scaling relations seem to be more complicated. This feature implies that besides stresses second order factors, as the hydrothermal or magmatic pore fluids in rock, influence source characteristics and bring new complications in scaling relations.

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41

Dost, Bernard, Annemijn van Stiphout, Daniela Kühn, Marloes Kortekaas, Elmer Ruigrok, and Sebastian Heimann. "Probabilistic Moment Tensor Inversion for Hydrocarbon-Induced Seismicity in the Groningen Gas Field, the Netherlands, Part 2: Application." Bulletin of the Seismological Society of America 110, no. 5 (August 11, 2020): 2112–23. http://dx.doi.org/10.1785/0120200076.

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ABSTRACT Recent developments in the densification of the seismic network covering the Groningen gas field allow a more detailed study of the connection between induced seismicity and reactivated faults around the gas reservoir at 3 km depth. With the reduction of the average station distance from 20 km to 4–5 km, a probabilistic full-waveform moment tensor inversion procedure could be applied, resulting in both improved hypocenter location accuracy and full moment tensor solutions for events of M≥2.0 recorded in the period 2016–2019. Hypocenter locations as output from the moment tensor inversion are compared to locations from the application of other methods and are found similar within 250 m distance. Moment tensor results show that the double-couple (DC) solutions are in accordance with the known structure, namely normal faulting along 50°–70° dipping faults. Comparison with reprocessed 3D seismic sections, extended to a depth of 6–7 km, demonstrate that (a) most events occur along faults with a small throw and (b) reactivated faults in the reservoir often continue downward in the Carboniferous underburden. From non-DC contributions, the isotropic (ISO) component is dominant and shows consistent negative values, which is expected in a compacting medium. There is some indication that events connected to faults with a large throw (>70 m) exhibit the largest ISO component (40%–50%).

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Scognamiglio, L., E. Tinti, and A. Michelini. "Real-Time Determination of Seismic Moment Tensor for the Italian Region." Bulletin of the Seismological Society of America 99, no. 4 (July 29, 2009): 2223–42. http://dx.doi.org/10.1785/0120080104.

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43

Trifu, C.-I. "A Fast Evaluation of the Seismic Moment Tensor for Induced Seismicity." Bulletin of the Seismological Society of America 90, no. 6 (December 1, 2000): 1521–27. http://dx.doi.org/10.1785/0120000034.

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44

Chapman, C. H., and W. S. Leaney. "A new moment-tensor decomposition for seismic events in anisotropic media." Geophysical Journal International 188, no. 1 (November 28, 2011): 343–70. http://dx.doi.org/10.1111/j.1365-246x.2011.05265.x.

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45

Pondrelli, S., A. Morelli, and E. Boschi. "Seismic deformation in the Mediterranean area estimated by moment tensor summation." Geophysical Journal International 122, no. 3 (December 1995): 938–52. http://dx.doi.org/10.1111/j.1365-246x.1995.tb06847.x.

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46

Jordan, Thomas H., and Alan Juarez. "Erratum: ‘Representation of complex seismic sources by orthogonal moment–tensor fields’." Geophysical Journal International 222, no. 2 (June 13, 2020): 1333–38. http://dx.doi.org/10.1093/gji/ggaa164.

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47

Liu, Rui-Feng, Yun-Tai Chen, Gong-Wei Zhou, Yi-Min Tu, and Pei-Shan Chen. "Applications of seismic moment tensor inversion in fast response to earthquakes." Acta Seismologica Sinica 12, no. 2 (March 1999): 129–36. http://dx.doi.org/10.1007/s11589-999-0017-2.

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48

Saetang, Kasemsak. "Focal Mechanisms of Mw 6.3 Aftershocks from Waveform Inversions, Phayao Fault Zone, Northern Thailand." International Journal of Geophysics 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/9059825.

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The focal mechanisms of Mw 6.3 aftershocks, Chiang Rai Province, Northern Thailand, were determined by using a multistation waveform inversion. Three aftershocks were selected and their waveforms were inverted for moment tensor calculation. Waveform inversions were derived from three broadband stations with three components and epicentral distances less than 250 km after all seismic stations were considered. The deviatoric moment tensor inversion was used for focal mechanism calculations. Band-pass filtering in the range of 0.03–0.15 Hz was selected for reducing low- and high-frequency noise. Source positions were created by using a single-source inversion and a grid-search method computed to optimize the waveform match. The results showed stable moment tensors and fault geometries with the southwest azimuth in the northern part of the Payao Fault Zone (PFZ) with depths shallower than 10 km. Left-lateral strike-slip with a reverse component was detected. The tectonics of the PFZ is constrained by fault-plane solutions of earthquakes. WSW directional strikes are observed in the northern part of the PFZ.

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Białoń, Wojciech, Grzegorz Lizurek, Jerzy Dec, Kamil Cichostępski, and Kaja Pietsch. "Relocation of Seismic Events and Validation of Moment Tensor Inversion for SENTINELS Local Seismic Network." Pure and Applied Geophysics 176, no. 11 (June 17, 2019): 4701–28. http://dx.doi.org/10.1007/s00024-019-02249-6.

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Lizurek, Grzegorz, Jan Wiszniowski, N. V. Giang, D. Q. Van, L. V. Dung, V. D. Tung, and Beata Plesiewicz. "Background seismicity and seismic monitoring in the Lai Chau reservoir area." Journal of Seismology 23, no. 6 (October 25, 2019): 1373–90. http://dx.doi.org/10.1007/s10950-019-09875-6.

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Abstract Reservoir-triggered seismic activity depends not only on the technical characteristics of the future reservoir (filling volume, the height of water column) but also on the seismo-tectonics and the natural seismic processes occurring in the area before construction of an artificial reservoir. Passive seismic monitoring was realised near Lai Chau (Vietnam) before the impoundment started. It allowed exploration of the natural seismicity in the area of the future dam. Locations of seismic events several months prior to the reservoir impoundment were observed with ten stations installed in the reservoir vicinity. Events were mainly located near the dam along the Da river headwaters fault. However, only four stations were available for the entire period before the impoundment. Despite the network limitations, completeness of seismic catalogue and b value were determined and may be used as a baseline for analysis of the seismicity in this area after impoundment. The magnitude completeness level is significantly smaller than in the broader seismogenic zones covering an area of the dam. The b value differs from the results obtained for regional seismicity of Northeastern Vietnam. The capability of the local network for moment tensor inversion was estimated with the use of synthetic data tests. Test results provided the requirements for the station number according to azimuthal coverage of the network to obtain the reliable full moment tensor (MT) solution. Preliminary analysis of the seismic activity after Lai Chau reservoir impoundment indicates some changes in activity related to the impoundment and reservoir exploitation.

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