A High-Resolution Seismic Catalog for the Initial 2019 Ridgecrest Earthquake Sequence: Foreshocks, Aftershocks, and Faulting Complexity

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 4 to 16 July, 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 crosscutting fault structures with dominantly perpendicular southwest and northwest strikes. Foreshocks of the M-w 6.4 event appear to align on a northwest-striking fault. Aftershocks of the M-w 6.4 event suggest that it further ruptured this northwest-striking fault, as well as the southwest-striking fault where surface rupture was observed. Finally, aftershocks of the M-w 7.1 show a highly complex distribution, illuminating a primary northwest-striking fault zone consistent with surface rupture but also numerous crosscutting southwest-striking faults. Aftershock relocations suggest that the M-w 7.1 event ruptured adjacent to the previous northwest-striking rupture of the M-w 6.4, perhaps activating a subparallel structure southwest of the earlier rupture. Both the northwest and southeast 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 northeast of the northwest rupture terminus.