Brawley, California Rocked by 150+ Earthquakes in One Day

Over a span of just about 24 hours, there were more than 150 earthquakes in Imperial County, transforming the usual quake hotspot in Southern California into one of the most active in the United States this weekend.

The U.S. Geological Survey (USGS), the federal agency that tracks earthquakes around the country, reported that the largest was a magnitude 4.4 felt near Brawley at 12:10 a.m. PDT on May 10.

In San Diego, residents reported light to moderate tremors, and in communities across the U.S.-Mexico border, residents in Mexicali reported moderate shaking. So far, there have been no immediate reports of significant damage or injuries caused by the swarm.

Why Imperial County Gets Frequent Earthquake Swarms

Imperial County is located in the Brawley Seismic Zone, a geologically active area where the San Andreas Fault, Imperial Fault, and several smaller fault systems converge. Geothermal fields are also located in the region and there are thousands of small earthquakes annually.

The USGS advises the public about earthquake sequences: “Earthquake swarms are normal in this region and do not signal an imminent, larger earthquake. Unlike a traditional earthquake sequence in which one large earthquake is followed by aftershocks, swarms are a series of earthquakes of similar magnitudes over hours or days.”

The quakes started Saturday in a series of magnitude 3’s near Brawley, a population of some 26,000 residents, about 115 miles east of San Diego. The 4.4 quake was the largest event in the sequence, with dozens of smaller aftershocks that continued until Sunday morning.

Is the Ground Still Moving?

The USGS earthquake feed also recorded more quakes on Sunday, several of which were magnitude 2.5 or higher. Following each rupture, the stress underground adjusts, leading to an incremental stress adjustment for nearby faults. Most of these aftershocks are not strong enough to cause damage to buildings, but they can last for days or weeks.

The California Governor’s Office of Emergency Services notes that “small earthquakes regularly occur in California and may not be noticed. The shaking continues for local residents, and is sometimes troubling but predictable.”

What Happens Next

Earthquake scientists do not know precisely when the earthquakes will cease or when and how much a larger quake will occur. After major events, the USGS estimates probabilities, but notes that most swarms tend to wane over time.

As per ABC7 reports, the City of Brawley wrote in a statement, “At this time, there are no reports of significant damage or threats to public safety. However, residents are encouraged to remain alert and prepared, as aftershocks may occur.”

Imperial County has had larger earthquakes in the past, such as the 1979 Imperial Valley earthquake, which was a magnitude 6.5 and caused damage to buildings, roads and irrigation canals.

State officials advise anchoring heavy furniture, assembling emergency supplies and enrolling in the California MyShake early warning system.

Read More: