Cascading, pulse-like ruptures during the 2019 Ridgecrest earthquakes, East California Shear Zone

Kejie Chen, Jean-Philippe Avouac, SAIF AATI, Chris Milliner, Fu Zheng, & Chuang Shi

Published August 15, 2019, SCEC Contribution #9815, 2019 SCEC Annual Meeting Poster #262

On July 4 2019, a Mw 6.5 earthquake struck the Searles Valley in California; 34 hours later, a larger Mw 7.1 shock ripped ~15 km to the northwest. Both ruptured previously unrecognized faults within the East California Shear Zone. Here, we present kinematic slip models of the two events based on measurements of static deformation from optical image correlation, Global Positioning System, and Synthetic Aperture Radar interferometry, combined with high-rate (1-Hz) Global Positioning System, strong motion and tele-seismic waveforms. They ruptured nearly orthogonal faults, a right-lateral NW trending fault about 60 km long and a left-lateral SW trending one about 22 km. The Mw 6.5 event initiated on a right-lateral NW striking fault and then ruptured a left-lateral fault to the surface, which triggered right-lateral slip during the Mw 7.1. The Mw 7.1 started as a bilateral, crack-like rupture on a segment that was brought closer to failure by the Mw 6.5 event and evolved into a pulse-like rupture on a segment that was actually unloaded by the Mw 6.5 event. The rupture propagated at a rather slow velocity of 2 km/s; it stopped abruptly at the Coso volcanic area in the North and at the Garlock Fault in the South. These earthquakes are part of a regional cluster of large magnitude earthquakes which includes the 1872, Mw 7.4-7.9, Owens Valley earthquake, the 1992, Mw 7.4 Landers earthquake and the 1999 Mw 7.1 Hector Mine earthquake. This study provides insight into the factors that control the mode and extent of seismic ruptures, and attest to the elevated seismicity level associated with an on-going and probably long-lived strain transient in the East California Shear Zone.

Citation
Chen, K., Avouac, J., AATI, S., Milliner, C., Zheng, F., & Shi, C. (2019, 08). Cascading, pulse-like ruptures during the 2019 Ridgecrest earthquakes, East California Shear Zone. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes