Seismic Swarm S20060104.1: Analysis of Activity Near Little Lake, California
Seismic swarm S20060104.1 occurred 16 km northeast of Little Lake, California, in the tectonically active transition zone between the Sierra Nevada and the Basin and Range province. This area features extensive normal and strike-slip faulting associated with regional extension and the Eastern California Shear Zone. The swarm initiated at 15:37 on 3 January 2006 and concluded at 08:35 on 6 January 2006, spanning 64 hours and 57 minutes. During this interval, 37 earthquakes were recorded, with magnitudes ranging from 0.2 to 2.5 and focal depths predominantly between 0 and 6 km.
The sequence began with the largest event, a magnitude 2.5 earthquake at a depth of 0 km. Subsequent activity included numerous microearthquakes clustered in the first hours, followed by sporadic events through 4 and 5 January. Depths remained shallow overall, with most events occurring at or near 1 km, consistent with fluid migration or minor fault slip in the upper crust. The final recorded event was a magnitude 0.6 earthquake at 3 km depth on 6 January.
This swarm aligns with the region's history of episodic seismic clusters. Since 1 January 2000, 18 swarms have been documented in the vicinity, distributed as follows: four in 2000, four in 2001, two in 2002, seven in 2004, and one in 2005. Such patterns reflect ongoing tectonic strain accumulation along local fault systems, occasionally influenced by geothermal processes in the broader Coso Volcanic Field area.
Geologically, Little Lake lies within a zone of Quaternary volcanism and active faulting. The surrounding landscape includes basaltic lava flows and cinder cones, with the nearest major structure being the Little Lake Fault. Seismicity in this setting typically arises from right-lateral shear and normal faulting, with swarms often indicating aseismic slip or pore-pressure changes at shallow depths.
The 2006 swarm's low-magnitude, high-frequency character and limited duration underscore the area's background microseismicity rather than a precursor to larger tectonic release. Continued monitoring supports refined models of strain distribution in this portion of eastern California.
References
- SeismoSight internal swarm classification records
- USGS Earthquake Catalog (historical swarm statistics 2000–2005)
- California Geological Survey, Regional Fault and Seismic Hazard Assessment reports