Two sets of earthquake swarms have hit California. What's going on along the Mexico border?

Two sets of earthquake swarms have hit California. What's going on along the Mexico border?

Rong-Gong Lin II

Another earthquake swarm has been rumbling along the California-Mexico border.

More than two dozen quakes greater than magnitude 2.5 have occurred since just after midnight Saturday, with epicenters about 175 miles southeast of downtown Los Angeles and 100 miles northeast of San Diego, according to the U.S. Geological Survey.

They have occurred largely along farmland between the towns of Brawley and Imperial in Imperial County. The largest quake was a magnitude 3.9 that struck at 4:05 p.m. Saturday, bringing light shaking to the Imperial Valley as well as south of the border and rattling Mexicali.

Good afternoon Southern California, did you feel the magnitude 3.9 quake about 3 miles southwest of Brawley at 4:05 pm? The #ShakeAlert system was activated. See: https://earthquake.usgs.gov/earthquakes/eventpage/ci40591055/executive… @Cal_OES @CAGeoSurvey

Good morning Southern California! Did you feel the magnitude 4.1 quake about 11 miles southeast of Ocotillo Wells at 5:17 am? The #ShakeAlert system was activated. See: https://earthquake.usgs.gov/earthquakes/eventpage/ew1716207460/executive… @Cal_OES @CAGeoSurvey @USGS_Quakes

An even larger earthquake — a magnitude 4.1 — occurred at 5:17 a.m. Monday about 28 miles northwest of the swarm that began Saturday.

The epicenter of that quake was in a remote desert area east of Anza-Borrego Desert State Park, and weak shaking was felt as far away as San Diego, parts of Orange County, Temecula, the Coachella Valley, El Centro and Holtville.

A separate swarm of earthquakes occurred a week ago, about 40 miles southeast of the most recent quake activity. Last week's swarm occurred about 18 miles southeast of Mexicali in Baja California, with the largest a magnitude 4.2 that was felt as far away as El Centro in California and Yuma, Ariz.

Earthquake swarms are common in the Imperial Valley. Swarms have happened many times in this part of California without being followed by a major, damaging earthquake.

Nonetheless, scientists typically pay close attention to the area, where there are many faults. And there have been moments of greater concern in recent years.

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