S047-0010
Fault Complexity of The 2019 Ridgecrest Earthquake Sequence As Inferred From PGV of Guided Waves

Monday, 14 December 2020
Poster
Mark Goldman1, Rufus Catchings2, Joanne H Chan3, Coyn Criley3, Jamison Haase Steidl4 and Amir A Allam5, (1)USGS Western Regional Offices Menlo Park, Earthquake Science Center, Menlo Park, CA, United States, (2)USGS, Earthquake Science Center, Menlo Park, CA, United States, (3)U.S. Geological Survey, Earthquake Science Center, Mountain View, CA, United States, (4)University of California, Santa Barbara, Earth Research Institute, Santa Barbara, CA, United States, (5)University of Alaska Fairbanks, Fairbanks, AK, United States
Abstract:
We evaluate guided-wave data from aftershocks that occurred on both the NW-SE- and the NE-SW-trending causative faults of the 2019 Ridgecrest earthquake sequence, along which the Mw 7.1 and Mw 6.4 earthquakes occurred, respectively, and compare our guided-wave indicators of faulting with mapped surface ruptures along both faults. Along the NW-SE-trending fault, we measure peak ground velocity (PGV) of guided-waves that were generated by an aftershock (3.8 km deep, Mw 4.7) located near the northwest end of the fault and recorded by an ~8-km-long linear array (Array B4) near the southeast end of the fault. High PGV of guided-wave values along Array B4 indicate that the fault zone is at least 5 km wide near the southern end of the fault, with faulting occurring along several discrete fault traces, consistent with surface geologic mapping. However, the PGV data indicate that the southwest part of the rupture zone, which was more discontinuously mapped at the surface than the northeast part of the same rupture zone, is more likely connected to the main fault at depth. Along the NE-SW-trending fault, we measure guided wave PGVs that were generated from an aftershock (10.5 km deep, Mw 3.6) located near the northeastern end of the fault and recorded by a ~3.5-km-long array (Array A1) near the southwestern end of the fault rupture. High PGV of guided-wave values along Array A1 indicate that the fault zone is at least as wide as the recording array (3.5 km), with faulting occurring along discrete fault traces. The data indicate that the main near-surface fault trace at Array A1 is located at and near the largest mapped surface ruptures, but we do not observe high PGV values near one of the mapped surface ruptures, which may not be directly connected to the main causative fault at depth. Data from both recording arrays show that seismic energy freely travels across both causative faults of a complex fault system that is at least several kilometers wide near the surface.
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