Earthquake Swarm S20220204.1 Near Little Lake, California

Seismic swarm S20220204.1 occurred 12 km northeast of Little Lake in Kern County, California. The sequence began at 04:28 UTC on 3 February 2022 and concluded at 04:34 UTC on 6 February 2022, spanning 72 hours and 6 minutes. During this interval, 45 earthquakes were recorded, with magnitudes ranging from -0.5 to 2.2 and focal depths predominantly between 1 and 6 km.

The events clustered tightly in both space and time, a hallmark of swarm behavior rather than a typical mainshock-aftershock sequence. The largest event reached magnitude 2.2 at a depth of 1 km on 3 February at 17:08 UTC. Most activity remained below magnitude 1.0, with 28 events at or below 0.5. Depths showed a shallow bias, consistent with fluid-driven processes or minor fault slip within the upper crust.

The Little Lake region sits within the Eastern California Shear Zone, a network of northwest-trending strike-slip faults that accommodate a portion of the Pacific-North America plate boundary motion. Local geology includes Quaternary alluvial deposits overlying Mesozoic basement rocks, with proximity to the Coso Volcanic Field influencing crustal permeability and geothermal gradients. This setting promotes episodic swarm activity through fluid migration along pre-existing fractures.

Historical records indicate persistent swarm occurrence in the area. Since 1 January 2000, 112 swarms have been identified. Annual counts show marked variability: 31 swarms in 2019 and 22 in 2020 coincide with the aftermath of the Ridgecrest earthquake sequence, while earlier years such as 2004 and 2010 recorded 7 events each. The 2022 swarm represents the sole documented sequence that year through early February.

Such swarms reflect the region's tectonic regime, where distributed deformation and hydrothermal circulation facilitate numerous small-magnitude events without producing a dominant mainshock. Monitoring data confirm that activity remained confined to a compact source volume, with no escalation to higher magnitudes during the three-day period.

References

SeismoSight internal swarm catalog (S20220204.1 parameters and historical statistics)
USGS Earthquake Catalog for regional context and fault mapping