Seismic Swarm S20190712.1 Near Searles Valley, California
SeismoSight registered Swarm S20190712.1 beginning at 23:20 on 11 July 2019 and concluding at 16:04 on 12 July 2019. The sequence occurred 17 km west of Searles Valley, California, and comprised 29 earthquakes over 16 hours and 44 minutes.
The events displayed a range of magnitudes from 0.3 to 2.4, with focal depths between 0 and 17 km. The largest shock reached magnitude 2.4 at 15:42 on 12 July at 9 km depth. Other notable events included magnitudes 2.1 and 2.2, both recorded on 12 July. Shallower events clustered near the surface, while deeper shocks extended to 17 km, illustrating typical variability in a compact swarm sequence.
This swarm forms part of the broader seismic environment surrounding Searles Valley in the Mojave Desert. The region lies within the Eastern California Shear Zone, where distributed strike-slip faulting accommodates a portion of the relative motion between the Pacific and North American plates. Historical records since 2000 document 19 swarms in the immediate area, with notable concentrations in 2010 (three swarms) and 2019 (seven swarms). Earlier episodes occurred in 2006, 2009, 2011, 2012, 2013, 2015, 2016, and 2018.
The swarm center lies approximately 1 km from the epicenter of the magnitude 7.1 Ridgecrest earthquake of 6 July 2019. That mainshock, part of the Ridgecrest Earthquake Sequence, produced widespread surface rupture and aftershock activity across the same fault network. The timing and location of Swarm S20190712.1 indicate it belongs to the continuing aftershock process following the July 2019 sequence.
Such swarms contribute to ongoing strain release without a single dominant mainshock. Depths spanning the upper crust align with the regional seismogenic zone, where brittle failure predominates above approximately 15–20 km. The modest magnitudes observed remain consistent with background aftershock decay rates following a large regional event.
SeismoSight internal classification
USGS Earthquake Catalog (regional context)
California Geological Survey (tectonic framework)