Seismic Swarm S20130826.1: Analysis of Activity near Bodfish, California
The seismic swarm designated S20130826.1 occurred approximately 22 km east-southeast of Bodfish in Kern County, California. It began at 18:50 UTC on 25 August 2013 and ended at 10:08 UTC on 28 August 2013, spanning 63 hours and 18 minutes during which 38 earthquakes were recorded.
The sequence initiated with a magnitude 4.1 event at 1 km depth. Subsequent events were predominantly of low magnitude, with the majority below 2.0 and depths ranging from 0 to 7 km. Notable events included a magnitude 3.6 quake at 2 km depth shortly after the initial shock, followed by a magnitude 2.6 event at 3 km depth later that evening. Activity gradually declined over the following days, with the final recorded event measuring magnitude 0.6 at the surface.
This swarm reflects typical characteristics of clustered seismicity in the region, where shallow crustal events occur in response to local stress adjustments along minor faults. No damage or felt reports beyond the immediate area were associated with the sequence.
Bodfish lies within the Kern River Valley of the southern Sierra Nevada, a zone of active tectonics influenced by the interaction between the Pacific and North American plates. The area features the north-south trending Kern Canyon Fault, a Quaternary-active structure capable of producing moderate earthquakes. Regional geology includes granitic basement rocks of the Sierra Nevada batholith overlain by sedimentary and volcanic units, with deformation distributed across the Walker Lane belt to the east. Historical seismicity in Kern County includes the 1952 magnitude 7.3 Kern County earthquake along the White Wolf Fault, underscoring the area's potential for larger events amid ongoing plate-boundary strain.
Since 1 January 2000, only two prior swarms have been documented in this locale: one in 2003 and another in 2008. These infrequent clusters suggest episodic release of accumulated strain rather than persistent high-rate activity.
The 2013 swarm provides insight into shallow seismogenic processes in the southern Sierra Nevada, where low-magnitude events at depths under 5 km predominate. Such sequences aid in refining models of fault interaction and seismic hazard assessment for the Kern River region.
References
USGS Earthquake Hazards Program catalog and fault database
California Geological Survey regional geologic maps
SeismoSight internal swarm classification records