Seismic Swarm S20031208.1 Near Bodfish, California

Seismic swarm S20031208.1 occurred 18 km south-southwest of Bodfish in Kern County, California. The sequence began at 07:54 on 8 December 2003 and concluded at 20:01 on 9 December 2003, spanning 36 hours and 6 minutes. During this interval, 46 earthquakes were recorded.

The events exhibited low magnitudes, ranging from 0.8 to 2.5. The largest shock measured 2.5 and occurred at 07:15 on 9 December. Most events clustered between magnitudes 1.2 and 1.7. Focal depths remained predominantly shallow, with the majority at or near 4 km; a smaller number reached 10–11 km. Activity showed a relatively steady rate throughout the first day, followed by a decline on 9 December after the peak event.

This swarm represents the third documented swarm sequence in the region since 1 January 2000. Earlier swarms occurred in 2001 (one sequence) and 2003 (two sequences total, including the present event).

The Bodfish area lies in the southern Sierra Nevada foothills of Kern County. The local geology consists primarily of Mesozoic granitic plutons intruded into older metamorphic rocks, overlain in places by Cenozoic sedimentary and volcanic deposits. The region experiences tectonic deformation linked to the broader Pacific–North American plate boundary, with contributions from both strike-slip motion along the Garlock Fault system to the south and normal faulting associated with eastern Sierra extensional regimes. Historical seismicity in Kern County includes the major 1952 Kern County earthquake (M7.3) located farther south, underscoring the area’s long-term potential for both isolated large events and clustered microseismicity.

Data for swarm S20031208.1 were obtained from SeismoSight internal records. Geological context draws on standard references for California tectonics and regional mapping.