Triggered slip on the Little Lake Fault Zone resulting from the 2019 Ridgecrest Earthquake Sequence, California
Abstract
The July 4, 2019 Mw 6.4 earthquake event in Ridgecrest, CA generated ~18km of left-lateral displacement on a northeast-southwest oriented fault zone, followed by the July 5, Mw 7.1 mainshock event, which generated ~50 km of right-lateral surface displacement on an intersecting northwest-southeast oriented fault zone. Previous earthquake events in the Ridgecrest area generated surface rupture: Indian Wells Valley M5.2 earthquake event on October 1, 1982, (Roquemore, and Zellmer, 1983), and the Ridgecrest ML5.8 earthquake on September 20, 1995 (SCEC Earthquake Data Center). North-trending, primarily right-lateral slip displacement and ground cracking from the 1982 event was expressed as left-stepping en-echelon segments, with down-to the east vertical displacement. Dextral triggered slip was documented from the 1995 event. In 1988, the California Geological Survey evaluated these fault traces and recommended them for zoning as Alquist-Priolo (AP) Earthquake Fault Zones (Wills, 1988).
Our field mapping for the 2019 Ridgecrest Earthquake documented triggered slip in areas of previously mapped Quaternary faults and AP zoned fault traces. North-trending previously un-mapped faults were also noted. We measured dextral displacement on faults with existing geomorphic scarps that ruptured in the 1982 event. Zones of displacement were located up to ~15km west of the Mw 7.1 epicenter. We present a comparison of rupture characteristics from each of these three earthquake events, and include a summary of our 2019 triggered slip observations which will be used to update the existing Alquist-Priolo Earthquake Fault Zone maps. We conclude that triggered slip is valuable for locating active faults and should be utilized as much as possible in future earthquakes. Particularly because cracking can be minor, there exists an urgency, post-event, to collect these data before it is obscured.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S31F0459H
- Keywords:
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- 7299 General or miscellaneous;
- SEISMOLOGY