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A high-resolution seismic catalog for the initial 2019 Ridgecrest Earthquake sequence: Foreshocks, aftershocks, and faulting complexity

David R. Shelly
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Abstract

I use template matching and precise relative relocation techniques to develop a high-resolution earthquake catalog for the initial portion of the 2019 Ridgecrest earthquake sequence, from July 4-16, encompassing the foreshock sequence and the first 10+ days of aftershocks following the M w 7.1 mainshock. Using 13,525 routinely cataloged events as waveform templates, I detect and precisely locate a total of 34,091 events. Precisely located earthquakes reveal numerous cross-cutting fault structures with dominantly perpendicular SW- and NW-strikes. Foreshocks of the M w 6.4 event appear to align on a NW-striking fault. Aftershocks of the M w 6.4 event suggest that it further ruptured this NW-striking fault, as well as the SW-striking fault where surface rupture was observed. Finally, aftershocks of the M w 7.1 show a highly complex distribution, illuminating a primary NW-striking fault zone consistent with surface rupture, but also numerous cross-cutting SW-striking faults. Aftershock relocations suggest that the M w 7.1 event ruptured adjacent to the previous NW-striking rupture of the M w 6.4, perhaps activating a subparallel structure southwest of the earlier rupture. Both the NW and SE rupture termini of the M w 7.1 rupture exhibited multiple-fault branching, with particularly high rates of aftershocks and multiple fault orientations in the dilatational quadrant NE of the NW rupture terminus.

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Seismological Research LettersArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 33.73347670599252° to 36.00467348670187° latitude; -119.66308593749999° to -114.63134765625001° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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David R. Shelly. 2020-01-22. A high-resolution seismic catalog for the initial 2019 Ridgecrest Earthquake sequence: Foreshocks, aftershocks, and faulting complexity. https://doi.org/10.1785/0220190309

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