Seismic Swarm S20140701.1: Analysis of Activity Near Coso Junction, California

The seismic swarm designated S20140701.1 was recorded in the Coso Junction region of California. Activity began at 21:59 on 30 June 2014 and concluded at 21:23 on 9 July 2014. Over 215 hours and 23 minutes, a total of 167 earthquakes were detected, with the epicentral area located approximately 10 km north of Coso Junction.

This swarm occurred within the Coso Volcanic Field, a geologically active area in eastern California characterized by Quaternary volcanism, geothermal systems, and extensional tectonics associated with the Basin and Range province. The region features rhyolitic domes, basaltic flows, and hydrothermal features that contribute to elevated seismic hazard. Shallow crustal faulting and fluid migration linked to geothermal reservoirs frequently trigger earthquake swarms here, distinguishing them from typical mainshock-aftershock sequences.

Examination of the first 100 events reveals predominantly low-magnitude activity. Magnitudes ranged from 0.0 to 3.1, with the majority below 2.0. Depths were consistently shallow, concentrated between 0 and 6 km, pointing to processes in the upper crust such as fluid pressure changes or minor magmatic movement. Notable events included a magnitude 3.0 quake on 1 July at 3 km depth and a magnitude 3.1 event on 2 July at 2 km depth. Temporal clustering showed peak rates during the initial days, with events distributed across small spatial clusters.

Historical records indicate persistent swarm activity in the area since 2000. A total of 43 swarms have been documented, with annual counts varying as follows: 6 in 2000, 4 in 2001, 2 in 2002, 9 in 2004, 2 in 2005, 5 in 2006, 1 in 2009, 5 in 2010, 3 in 2012, 5 in 2013, and 1 in 2014. These patterns underscore the ongoing tectonic and volcanic influences shaping seismicity in the Coso region.

Such swarms provide valuable data for monitoring geothermal fields and assessing volcanic risk. Continued observation supports improved understanding of fault interactions and fluid dynamics in this tectonically dynamic setting.

References

SeismoSight internal swarm classification records.
USGS Earthquake Catalog for regional context.
California Geological Survey reports on Coso Volcanic Field.