Seismic Swarm S20160217.1 Near Wilkerson, California: Analysis and Regional Context

A seismic swarm designated S20160217.1 occurred 7 km south-southwest of Wilkerson in Inyo County, California. The sequence began at 12:39 on 16 February 2016 and concluded at 07:49 on 18 February 2016, spanning 43 hours and 10 minutes. During this interval, 37 earthquakes were recorded, with magnitudes ranging from 0.6 to 4.7 and focal depths primarily between 6 km and 15 km.

The swarm initiated with a magnitude 1.1 event at 14 km depth. Activity intensified later that evening, including a magnitude 4.7 earthquake at 15 km depth at 23:04, followed closely by a magnitude 4.3 event at the same depth at 23:27. Subsequent events showed a gradual decline in frequency and magnitude, with the majority occurring at depths of 13–15 km. The final recorded event was a magnitude 0.9 quake at 14 km depth.

This swarm represents one of only three such sequences documented in the area since 2000. Earlier swarms occurred in 2007 (two events) and 2012 (one event), indicating episodic clustered seismicity rather than continuous aftershock sequences.

The Wilkerson region lies within Owens Valley, part of the eastern Sierra Nevada boundary zone in the Basin and Range province. Tectonic extension accommodates right-lateral shear between the Pacific and North American plates along the Eastern California Shear Zone. The valley is bounded by the Sierra Nevada frontal fault system to the west and the Owens Valley fault to the east. The latter produced the 1872 Owens Valley earthquake, estimated at magnitude 7.4–7.8, which generated surface rupture exceeding 100 km.

Seismicity in this area reflects both normal and strike-slip faulting at depths typically less than 20 km. Updated regional monitoring by the USGS and California Geological Survey confirms ongoing microseismicity consistent with the observed swarm patterns. No surface rupture or significant damage was associated with the 2016 sequence.

References

USGS Earthquake Catalog
California Geological Survey Fault Activity Map
SeismoSight internal swarm classification records