Seismic Swarm S20201030.1 Near Searles Valley, California

SeismoSight registered swarm S20201030.1 approximately 47 km north of Searles Valley in California. The sequence began at 11:05 on 29 October 2020 and concluded at 13:51 on 31 October 2020, spanning 50 hours and 46 minutes. During this period, 54 earthquakes were recorded.

The events exhibited magnitudes between 0.1 and 2.4, with the largest event measuring 2.4 at a depth of 1 km on 31 October. Depths remained predominantly shallow, ranging from 1 km to 8 km, consistent with activity in the upper crust. The swarm displayed typical characteristics of clustered seismicity, featuring multiple events within short time intervals rather than a single mainshock-aftershock pattern.

This region forms part of the Eastern California Shear Zone, a tectonically active area accommodating right-lateral shear between the Pacific and North American plates. The local geology includes Quaternary alluvial deposits overlying older metamorphic and igneous basement rocks, with fault systems such as the Garlock Fault and nearby segments of the Little Lake Fault contributing to seismic potential. The area experienced significant activity during the 2019 Ridgecrest earthquake sequence, which included magnitude 6.4 and 7.1 events located nearby and highlighted ongoing strain accumulation.

Historical records indicate nine seismic swarms in the vicinity since 2000. These occurred in 2000, 2002, 2008, 2014, 2015, 2019 (three swarms), and 2020. Such swarms often reflect fluid migration or aseismic slip along faults in this extensional and shear-dominated setting.

The 2020 swarm adds to the understanding of episodic seismicity in the Searles Valley region, where shallow crustal events predominate due to the local fault architecture and geothermal influences from the nearby Coso area.

References

USGS Earthquake Catalog California Geological Survey Regional Reports SeismoSight Internal Database