USGSVerified account

THREAD: Major (Mw 7.1) quake occurred 17 km NNE of Ridgecrest, CA on China Lake Naval Air Center at 8:19pm local time, July 5, 2019. Closest large pop. center is Ridgecrest with pop. of 28k people. This is continuation of sequence that started w/Mw 6.4 approx. 36 hrs beforehand

Maximum shaking levels are MMI IX (Violent) in the epicentral region and very strong shaking (MMI VII) occurred over a 40 km wide region near the epicenter that includes the city of Ridgecrest.

ShakeAlert was issued 8.0s after origin time. Initial estimated mag. was 5.5 and final mag. was 6.3. Initial estimated location was 2.7 km from ANSS location. An alert was not issued via ShakeAlertLA app to Los Angeles b/c estimated intensity was below required threshold to alert

This mainshock appears to be located at the NW end of NW-oriented fault involved in the M6.4 and has a right-lateral strike-slip mechanism. The M6.4 earthquake on 7/4/2019 broke across two faults in the Airport Lake Fault Zone. This event appears to be on the same fault zone.

Shaking was widely felt throughout California, including light to moderate ground shaking in Los Angeles, weak shaking in the San Francisco Bay Area, and felt shaking extending at least as far east as Phoenix and as far north as Sacramento.

Scientists from the USGS and other organizations are on the ground and working to learn more about the surface rupture.

The ShakeAlert system detected quake in 8.0 sec. And, our real-time system first detected and reported the quake as a M7.1 at 8:21 pm within 2 minutes of the origin time. USGS quake websites were temporarily overwhelmed by the intense interest in quake, but are accessible now.