Berkeley Seismic Moment Tensor Method, Uncertainty Analysis, and Study of Non-double-couple Seismic Events

Dreger, Douglas S.

doi:10.1007/978-3-319-77359-9_4

Cited by 6 publications

(3 citation statements)

References 32 publications

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“…Therefore, the results obtained using the REFOC are highly consistent with those using the HASH. To evaluate the reliability of the results, we further compared the focal mechanisms obtained using HASH and REFOC algorithms with the NCSS moment tensor solutions obtained by waveform modeling (Dreger, 2018). The focal mechanisms obtained using REFOC algorithm are more consistent with moment tensor solutions compared with those using HASH algorithm (Figure 6d), suggesting that the REFOC method can help to obtain more accurate focal mechanism solutions.…”

Section: Application To the Parkfield Areamentioning

confidence: 99%

A New Focal Mechanism Calculation Algorithm (REFOC) Using Inter‐Event Relative Radiation Patterns: Application to the Earthquakes in the Parkfield Area

2023

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Accurate earthquake focal mechanisms are essential for solving fault zone structure, estimating stress variations, and assessing seismic hazards. Small earthquakes' focal mechanisms are usually solved using P‐wave first‐motion polarities and/or S‐/P‐wave amplitude ratios, which are limited due to the low signal‐to‐noise ratio of small‐earthquake waveforms and a limited number of three‐component seismograms. To increase the number of high‐quality focal mechanisms, we develop a method that utilizes the inter‐event relative radiation patterns to perform a joint focal mechanism inversion of numerous clustered events (called REFOC). The method first uses P‐wave polarities and S‐/P‐wave amplitude ratios to constrain the initial solutions and then combines these solutions and the inter‐event P‐/P‐wave and S‐/S‐wave amplitude ratios to refine solutions. For example, we apply the method to 38,413 earthquakes in the Parkfield region, California. The REFOC outperforms traditional methods with 57% more solutions with <55° uncertainties (>70% of the catalog events) and 126% more solutions with <25° uncertainties (>40% of the catalog events), illuminating unprecedented fine‐scale rupture processes. Instead of rupturing along the main fault, many M < 2 focal mechanisms show >45° angular differences from the 2004 Mw 6.0 Parkfield earthquake. The variation of focal mechanism properties is spatially related to the variation of fault strength and geometry, and temporally correlated with the shear stress variations before, during, and after the 2004 Mw 6.0 earthquake. The observations highlight the potential of applying REFOC to monitor unprecedented details of fault zone structure and stress field, providing new insights into fault rupture physics, seismotectonic processes, and seismic hazards.

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Section: Application To the Parkfield Areamentioning

confidence: 99%

A New Focal Mechanism Calculation Algorithm (REFOC) Using Inter‐Event Relative Radiation Patterns: Application to the Earthquakes in the Parkfield Area

2023

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“…To retrieve the moment tensor solutions for Mw ≥ 3.3 events, we adopted the Time-Domain Moment Tensor inversion algorithm from the Berkeley Seismological Laboratory [20][21][22]. We constrain the inversion to solve for the best fitting deviatoric solution only, with no isotropic component.…”

Section: Seismic Analysismentioning

confidence: 99%

Earthquake Source Investigation of the Kanallaki, March 2020 Sequence (North-Western Greece) Based on Seismic and Geodetic Data

et al. 2021

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The active collision of the Apulian continental lithosphere with the Eurasian plate characterizes the tectonics of the Epirus region in northwestern Greece, invoking crustal shortening. Epirus has not experienced any strong earthquakes during the instrumental era and thus there is no detailed knowledge of the way the active deformation is being expressed. In March 2020, a moderate size (Mw 5.8) earthquake sequence occurred close to the Kanallaki village in Epirus. The mainshock and major aftershock focal mechanisms are compatible with reverse faulting, on NNW-ESE trending nodal planes. We measure the coseismic surface deformation using radar interferometry and investigate the possible fault geometries based on seismic waveforms and InSAR data. Slip distribution models provide good fits to both nodal planes and cannot resolve the fault plane ambiguity. The results indicate two slip episodes for a N337° plane dipping 37° to the east and a single slip patch for a N137° plane dipping 43° to 55° to the west. Even though the area of the sequence is very close to the triple junction of western Greece, the Kanallaki 2020 activity itself seems to be distinct from it, in terms of the acting stresses.

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confidence: 99%

Regional Moment Tensor Inversion Using Rotational Observations

2021

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The application of the moment tensor (MT) inversion method is a useful and proven tool in seismology (e.g., D'Amico, 2018). Regional MT solutions are routinely determined in real-time by various universities and government agencies to quickly report important earthquake faulting mechanisms and moment magnitudes (e.g., Dreger, 2018; Pasyanos et al., 1996; Thio & Kanamori, 1995). These time-domain full-waveform methods typically use regional-distance long-period filtered body and surface waves to estimate the deviatoric or full-MT solution (Full-MT). The method works well with magnitude three to six earthquakes because of the assumption that the time-duration of the seismic source process is approximated by an impulse time-function in the frequency range of 0.1-0.01 Hz (or 10-100 s period). The Green's functions (GFs) are computed using simple one-dimensional layered Earth models since long-period waves traveling at surface-wave phase velocities have wavelengths that are larger than the scale-lengths of crustal heterogeneities. These long-period waves, at short source-to-receiver distances (<1000-km), travel for only several

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Berkeley Seismic Moment Tensor Method, Uncertainty Analysis, and Study of Non-double-couple Seismic Events

Cited by 6 publications

References 32 publications

A New Focal Mechanism Calculation Algorithm (REFOC) Using Inter‐Event Relative Radiation Patterns: Application to the Earthquakes in the Parkfield Area

A New Focal Mechanism Calculation Algorithm (REFOC) Using Inter‐Event Relative Radiation Patterns: Application to the Earthquakes in the Parkfield Area

Earthquake Source Investigation of the Kanallaki, March 2020 Sequence (North-Western Greece) Based on Seismic and Geodetic Data

Regional Moment Tensor Inversion Using Rotational Observations

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