Earthquake swarm south of Coso Volcanic Field continues with declining intensity. We continue to monitor

Release Date:

The seismic activity that started on the evening of July 5 at the southern margin of Coso Volcanic Field in Inyo County, California continues at a rate of about 600 M1.0 or greater earthquakes per day.

The activity was triggered by a magnitude M5.4 earthquake at 9:19 PM PDT located 20 km (~20 miles) ESE of Little Lake, which itself was an aftershock of the M7.1 earthquake that occurred about an hour earlier on the 5th, located 17 km NNE of Ridgecrest to the south. The intensity of the activity at Coso is gradually declining. Of the approximately 1600 earthquakes detected at M1.0 or above since July 8, only 12 have been M3.0 or above, with the largest two registering M4.1.

The current activity at Coso can be considered distant aftershocks, or triggered earthquakes. The M7.1 on July 5 occurred on a NW-trending fault oriented toward the Coso area, and it is common for large earthquakes to cause aftershocks beyond the actual fault rupture. No ground deformation indicative of volcanic activity has been detected, and there is no imminent threat of an eruption. The California Volcano Observatory will continue to monitor the situation for any sign of volcanic activity and provide updates as warranted.