Seismic Swarm S20130406.1 Near Coso Junction, California
Seismic swarm S20130406.1 occurred in the Coso Volcanic Field region of eastern California, centered 8 km east of Coso Junction. The sequence began at 01:11 on 5 April 2013 and concluded at 21:26 on 8 April 2013, spanning 92 hours and 15 minutes. During this period, 59 earthquakes were recorded, with magnitudes ranging from -0.1 to 2.6 and focal depths predominantly between 0 and 4 km.
The swarm exhibited typical characteristics of clustered microseismicity, with the largest event reaching magnitude 2.6 on 5 April at 11:51. Subsequent notable shocks included magnitudes of 2.4 and 2.2 on 6 April, alongside numerous events below magnitude 1.0. Depths remained shallow throughout, consistent with activity in a geothermal and volcanic setting where fluid migration influences fault slip.
The Coso Volcanic Field lies within the Basin and Range province, featuring Quaternary rhyolite domes, basaltic flows, and extensive geothermal systems. High heat flow and active tectonics associated with the Walker Lane belt contribute to frequent earthquake swarms. Historical records indicate 39 swarms in the area since 2000, with annual counts varying from one to seven events per year in peak periods such as 2004, 2006, and 2010.
This swarm aligns with patterns observed in prior episodes, underscoring the region's persistent seismic productivity driven by both tectonic extension and hydrothermal processes. No damage or felt reports beyond instrumental detection were associated with the sequence.
References
SeismoSight internal swarm classification records.
USGS Earthquake Catalog and Coso Volcanic Field geological summaries.
California Geological Survey reports on eastern California seismicity.