California earthquake: Quake hits California near Mexico border followed by swarm

California has seen a swarm of earthquakes today at the US-Mexico border. The United States Geological Survey (USGS) detected a magnitude 4.0 earthquake to the east of El Centro at 2am this morning before a swarm of lower magnitude tremors shook the area. Some 12 earthquakes followed in the same area, all surging from 2.10am to 10am.

According to the USGS, the smaller earthquakes were of low magnitude, each ranging from 2.5 to 3.3.

Most also struck far below the surface, roughly 11km (six miles) deep.

Officials recorded no damage as a result of the earthquake cluster in the nearby town of El Centro, which has a population of 44,000.

El Centro sits in Imperial County, one of the US’s most important agricultural centres.

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The 2010 Baja California earthquake was a magnitude 7.2 event felt throughout Mexico and Southern California, and the most severe in the region since the 1952 Kern County earthquake.

Two to four people are thought to have died when the earthquake hit.

Before the 2010 event was the 1979 Imperial Valley quake, a 6.4 magnitude event which caused extensive damage to the Imperial County area.

According to official figures, the earthquake caused $30 million worth of damage, injured 91 people, and damaged more than 1,500 homes.

While seismologists are studying the earthquake swarms in the Imperial Fault Zone, the fabled ‘Big One’ – a magnitude 6 or stronger earthquake which could rock California – has sprung back into relevance.

Researchers recently detected seismic activity along the Californian Garlock fault, located in California’s Mojave Desert, which has until recently been dormant.

The fault is capable of causing a magnitude 8 earthquake, and researchers believe the Ridgecrest earthquakes in July this year awakened it.

Speaking to Business Insider, Richard Allen, director of the University of California’s Seismological Laboratory said: “The two Ridgecrest earthquakes were fairly large-magnitude earthquakes and they’re fairly close to the Garlock fault, so the change that they caused in the stress fields would obviously have an impact.”