Earthquake Swarm VS20250410.1 Near Calipatria, California
A seismic swarm designated VS20250410.1 occurred 15 km west-northwest of Calipatria in Imperial County, California. The sequence began at 05:24 on 10 April 2025 and concluded at 14:45 on 11 April 2025, spanning 33 hours and 21 minutes. During this period, 64 earthquakes were recorded.
The events clustered tightly in both time and space, with magnitudes ranging from 0.2 to 3.2. Depths remained shallow, predominantly between 0 and 5 km, though a few reached 8–11 km. The largest event, magnitude 3.2, occurred at 02:52 on 11 April at 3 km depth. Other notable shocks included a magnitude 3.1 at 12:49 on 10 April and a magnitude 2.8 at 08:55 on the same day. Most activity featured magnitudes below 2.0, consistent with swarm behavior rather than a mainshock-aftershock sequence.
This swarm unfolded within the Imperial Valley, part of the Salton Trough—a tectonically active pull-apart basin formed by the interaction of the San Andreas Fault system and the divergent boundary between the Pacific and North American plates. The region lies along the Brawley Seismic Zone, where right-lateral strike-slip faulting and geothermal processes drive frequent small earthquakes. Shallow depths reflect the thin crust and high heat flow associated with the underlying magmatic and hydrothermal systems linked to the Salton Sea geothermal field.
Imperial Valley has a well-documented history of earthquake swarms. Since 2000, 99 swarms have occurred in the area, with notable clusters in 2009 (11 swarms), 2010 (13), 2012 (11), 2013 (13), and 2021 (8). These episodes typically involve hundreds to thousands of events over days to weeks and are often linked to fluid migration along faults or pressure changes in geothermal reservoirs. The 2025 swarm fits this pattern, adding to the cumulative record of swarm activity that underscores the valley’s elevated seismic hazard.
No damage or felt reports beyond minor shaking were associated with the largest events, as is common for swarms of this scale. Continued monitoring remains essential given the proximity to critical infrastructure, including irrigation canals and geothermal facilities.
References
- USGS Earthquake Catalog (earthquake.usgs.gov)
- Southern California Seismic Network (scsn.org)
- California Geological Survey fault and seismicity maps