Seismic Swarm S20240419.3 Near Bodfish, California

A seismic swarm designated S20240419.3 occurred 11 km south-southwest of Bodfish in Kern County, California. The sequence began at 19:19 on 18 April 2024 and concluded at 17:27 on 19 April 2024, spanning 22 hours and 8 minutes. During this period, 25 earthquakes were recorded.

The largest event reached magnitude 4.3 at a depth of 3 km shortly after initiation. Subsequent activity included a magnitude 3.1 event at 04:51 on 19 April, also at 3 km depth. Most events clustered at depths of 2–5 km, with the majority at 3 km. Magnitudes ranged from 0.7 to 4.3, showing a typical swarm pattern of clustered, moderate-energy releases without a single dominant mainshock-aftershock sequence.

The swarm location lies within the southern Sierra Nevada, where the Kern Canyon Fault and associated structures accommodate regional extension and strike-slip motion. This tectonic setting reflects interaction between the Pacific and North American plates, with the area influenced by the nearby Garlock Fault system to the south. Crustal depths in this zone commonly host shallow seismicity due to brittle deformation in the upper 10–15 km of the lithosphere.

Historical records indicate eight prior swarms in the region since 2000. These occurred in 2001 (1 event), 2003 (3 events), 2004 (1 event), 2008 (1 event), 2013 (1 event), and 2022 (1 event). Such episodic clusters align with the area's known capacity for distributed, low-to-moderate magnitude activity along secondary faults.

Seismic swarms in this part of California often relate to fluid migration or aseismic slip triggering along fault networks. Depths predominantly near 3 km suggest involvement of shallow crustal layers potentially affected by hydrothermal or groundwater processes common in the Kern River Valley.

Monitoring by regional networks continues to track after-activity, supporting hazard assessment for nearby communities. Updated geological mapping confirms ongoing Quaternary faulting in the vicinity, consistent with the observed event distribution.

References

SeismoSight internal swarm classification S20240419.3
USGS Earthquake Hazards Program regional tectonic summaries
California Geological Survey fault activity database