Another swarm of earthquakes has been rumbling along the California-Mexico border.
According to the U.S. Geological Survey, more than two dozen earthquakes larger than magnitude 2.5 have occurred since shortly after midnight Saturday, with epicenters about 175 miles southeast of downtown Los Angeles and 100 miles north. northeast of San Diego.
They have occurred primarily along farmland between the towns of Brawley and Imperial in Imperial County. The largest earthquake was magnitude 3.9 and occurred at 4:05 pm on Saturday, causing light tremors in the Imperial Valley as well as south of the border and shaking Mexicali.
An even larger earthquake, magnitude 4.1, occurred at 5:17 a.m. Monday, about 28 miles northwest of the swarm that began Saturday.
The epicenter of that earthquake occurred 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 , Downtown and Holtville.
Another earthquake swarm occurred about a week ago, about 40 miles southeast of the most recent seismic activity. Last week's swarm occurred about 18 miles southeast of Mexicali in Baja California, and the largest was a magnitude 4.2 that was felt as far away as El Centro in California and Yuma, Arizona.
Earthquake swarms are common in the Imperial Valley, seismologist Lucy Jones said on social media Saturday. Swarms have occurred many times in this part of California without being followed by a major and damaging earthquake.
However, scientists usually pay close attention to the area, where there are many faults.
The region was particularly active with earthquakes in the late 1970s and 1980s.
Of the largest earthquakes in historic times in the area — a magnitude 6.9 earthquake in 1940 and a magnitude 6.4 earthquake in the Imperial Valley in 1979 — they occurred without prior swarms, Jones said. The 1979 earthquake caused $30 million in damage, injured 91 people, and damaged more than 1,500 homes and more than 400 commercial buildings.
In 1987, more significant earthquakes occurred in the area. The Superstition Hills earthquake, which followed a magnitude 6.2 tremor on a nearby fault that occurred 11 hours earlier, caused $4 million in damage and injured 94 people in Imperial County and left 3,000 dead. temporarily homeless people in the Mexicali area.
South of the California-Mexico border, a magnitude 7.2 earthquake struck on Easter Sunday 2010, killing two people in Mexicali and damaging buildings on both sides of the border.
