Moment-Tensor Determination by Nonlinear Inversion of Amplitudes

Godano, Maxime; Bardainne, T.; Régnier, Marc; Deschamps, A.

doi:10.1785/0120090380

Cited by 30 publications

(12 citation statements)

References 32 publications

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“…On the other hand, Horalek et al (2010) studied 45 of the largest M 1.4-2.9 earthquakes from a 2003 borehole injection experiment and found that DC mechanisms dominated the sequence. Godano et al (2011) studied four microearthquakes induced in the Soultz-sous-Forets HDR reservoir and obtained moment tensor solutions having high uncertainty associated with low isotropic and CLVD components. Deichmann and Giardini (2009) found that seismicity induced by the enhanced geothermal system of Basel, Switzerland, generally have focal mechanisms that indicate shear failure on preexisting faults, with some focal mechanisms showing signs of non-DC components with volume change.…”

Section: Introductionmentioning

confidence: 99%

A Systematic Analysis of Seismic Moment Tensor at The Geysers Geothermal Field, California

Boyd¹,

Dreger²,

Lai³

et al. 2015

Bulletin of the Seismological Society of America

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The Geysers geothermal field is one of the most seismically active regions in northern California. Most of the events occur at shallow depths and are related to stress and hydrological perturbations due to energy production operations. To better understand the relationships between seismicity and operations, better source mechanism information is needed. Seismic moment tensors offer insight into the nature of equivalent forces causing the seismicity. Fifty-three M >3 events located at The Geysers geothermal field were selected from the University of California Berkeley Moment Tensor Catalog for analysis of seismic moment tensor solutions and associated uncertainties. Deviatoric and full moment tensor solutions were computed, and statistical tests were employed to assess solution stability, resolution, and significance. In this study, we examine several source models including double-couple (DC), pure isotropic (ISO; volumetric change), and volume-compensated linear vector dipole (CLVD) sources, as well as compound sources such as DC CLVD, DC ISO, and shear-tensile sources. In general, we find from a systematic approach toward characterizing uncertainties in moment tensor solutions that The Geysers earthquakes, as a population, deviate significantly from northern California seismicity in terms of apparent volumetric source terms and complexity.

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Section: Introductionmentioning

confidence: 99%

A Systematic Analysis of Seismic Moment Tensor at The Geysers Geothermal Field, California

Boyd¹,

Dreger²,

Lai³

et al. 2015

Bulletin of the Seismological Society of America

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“…The basic tool for quantifying earthquake sources is the seismic moment tensor. The moment tensor is calculated using amplitudes of seismic waves (Vavryčuk et al 2008; Fojtíková et al 2010; Godano et al 2011), amplitude ratios (Miller et al 1998; Hardebeck & Shearer 2003; Jechumtálová & Šílený 2005) or full waveforms (Dziewonski et al 1981; Sipkin 1986; Kikuchi & Kanamori 1991; Šílený et al 1992). The inversion of full waveforms is a widely used approach applicable on all scales: from micro‐ to large macro‐earthquakes.…”

Section: Introductionmentioning

confidence: 99%

Moment tensor inversion of waveforms: a two-step time-frequency approach

Vavryčuk¹,

Kühn

2012

Geophysical Journal International

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SUMMARY We present a moment tensor inversion of waveforms, which is more robust and yields more stable and more accurate results than standard approaches. The inversion is performed in two steps and combines inversions in time and frequency domains. First, the inversion for the source‐time function is performed in the frequency domain using complex spectra. Second, the time‐domain inversion for the moment tensor is performed using the source‐time function calculated in the first step. In this way, we can consider a realistic, complex source‐time function and still keep the final moment tensor inversion linear. Using numerical modelling, we compare the efficiency and accuracy of the proposed approach with standard waveform inversions. We study the sensitivity of the retrieved double‐couple and non‐double‐couple components of the moment tensors to noise in the data, to inaccuracies of the location and of the velocity model, and to the type of the focal mechanism. Finally, the proposed moment tensor inversion is tested on real data observed in a complex 3‐D inhomogeneous geological environment: a production blast and a rockburst in the Pyhäsalmi ore mine, Finland.

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“…Here we assume the focal mechanism of the small induced events can be represented by pure double couples (Rutledge & Phillips, 2002), though it is possible that a volume change or Compensated Linear Vector Dipoles (CLVD) part may also exist, especially in hydraulic fracturing cases, and the nondouble-couple components are informative for understanding the rock failure under highpressure fluid (Ross & Foulger, 1996;Jechumtálová & Eisner, 2008;Šílený et al, 2009;Song & Toksoz, 2010). The constraining of focal mechanism as double couple (DC) can eliminate the spurious non-DC components in the inversion raised by modeling the wave propagation in anisotropic medium with isotropic Green's functions or inaccuracy of the velocity model (Šílený & Vavryčuk, 2002;Godano et al, 2011). However, if strong non-DC components actually exist in the source rupture process, the determined fault plane may be biased (e.g., Jechumtálová & Šílený, 2001;Jechumtálová & Šílený, 2005).…”

Section: Focal Mechanism Determination Methodsmentioning

confidence: 99%

“…There have been many studies on determining the focal mechanism of the induced seismicity in cases of enhanced geothermal system development, mining and hydraulic fracturing. Godano et al (2011) used the direct amplitudes of P, SV and SH to study the focal mechanisms of induced microearthquakes in a geothermal site using full-space homogeneous velocity models. Nolen-Hoeksema et al (2001) used the first half cycle after the first arrivals from the observed seismograms and synthetics from full-space Green's functions to determine the focal mechanisms of several hydraulic fracture events.…”

Section: Introductionmentioning

confidence: 99%

Focal mechanism determination of induced microearthquakes in an oil field using full waveforms from shallow and deep seismic networks

Küleli

Zhang

et al. 2011

GEOPHYSICS

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A new, high frequency, full waveform matching method is used to study the focal mechanisms of small, local earthquakes induced in an oil field, which are monitored by a sparse near-surface network and a deep borehole network. The determined source properties are helpful for understanding the local stress regime in this field. During the waveform inversion, we maximize both the phase and amplitude matching between the observed and modeled waveforms. We also use the polarities of the first P-wave arrivals and the average S/P amplitude ratios to better constrain the matching. An objective function is constructed to include all four criteria. For different hypocenters and source types, comprehensive synthetic tests show that our method is robust to determine the focal mechanisms under the current array geometries, even when there is considerable velocity inaccuracy. The application to several tens of induced microseismic events showed satisfactory waveform matching between modeled and observed seismograms. The majority of the events have a strike direction parallel with the major NE-SW faults in the region, and some events trend parallel with the NW-SE conjugate faults. The results are consistent with the in-situ well breakout measurements and the current knowledge on the stress direction of this region. The source mechanisms of the studied events together with the hypocenter distribution indicate that the microearthquakes are caused by the reactivation of preexisting faults. We observed that the faulting mechanism varies with depth, from strike-slip dominance at shallower depth to normal faulting dominance at greater depth.

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Moment-Tensor Determination by Nonlinear Inversion of Amplitudes

Cited by 30 publications

References 32 publications

A Systematic Analysis of Seismic Moment Tensor at The Geysers Geothermal Field, California

A Systematic Analysis of Seismic Moment Tensor at The Geysers Geothermal Field, California

Moment tensor inversion of waveforms: a two-step time-frequency approach

Focal mechanism determination of induced microearthquakes in an oil field using full waveforms from shallow and deep seismic networks

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