Southern California Hit by Three Earthquakes in a Single Day

Southern California was hit by three earthquakes on Monday, according to data logged by the U.S. Geological Survey (USGS).

At 11:19 p.m. last night, a magnitude 3.5 tremor was recorded roughly eight miles from Morongo Valley, San Bernardino County, taking place at a depth of four miles.

According to the USGS data, a magnitude 3.4 tremor hit San Bernardino County east of Los Angeles at 1:28 a.m. on Monday, striking close to the city of Loma Linda. Shortly after, recorded at 2:56 a.m., a magnitude 3.6 earthquake was felt at the Mojave Desert near the Kern County city of Ridgecrest, initially striking close to Little Lake.

There were no reports of injuries or damage as a result of the earthquakes, according to ABC7. Still, the two similarly-sized earthquakes earlier Monday morning sparked social media comments from some California residents who said they felt the impacts.

"I was already half asleep playing Sims then I felt the earthquake now I'm fully awake," one Twitter user noted in a post that was liked more than 100 times.

Others took a relaxed approach to reports about the tremors. "It's weird to live in a place where frequent, tiny earthquakes are normal. California keeps you on your toes!" tweeted Danielle Crespo. Another person said: "You know you're from California when 'earthquake' is trending yet no one you know in real life [has] mentioned it."

Some California residents in closer proximity to the Morongo Valley quake shared their experiences to the European-Mediterranean Seismological Centre (EMSC).

"Heard it more than we felt it. Very light movement but the sound it made, confirmed it was coming from deep underground," said one person based in Banning, roughly 13 miles southwest from the epicenter. A person in Desert Hot Springs, 14 miles south of the epicenter, described it as being "an abrupt shake lasting about two seconds."

By most accounts, the later Morongo Valley quake was fairly tame. "One little shake but made me realize that it was an earthquake," noted a person about 17 miles away.

Magnitude is a measure of an earthquake's size. Experts from Michigan Tech have said that quakes between magnitude 2.5 and magnitude 5.4 are often felt, however they typically only cause minor damage.

In comparison, quakes between 6.1 and 6.9 can cause significant damage to populated areas, while quakes of more than magnitude 7.0 are considered to be major.

"An earthquake is what happens when two blocks of the earth suddenly slip past one another," the USGS says. "The surface where they slip is called the fault. The location below the earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter."

As reported, both the San Bernardino County and Mojave Desert are found along the San Andreas Fault, an 800-mile region known for its turbulent tectonic activity. It forms the tectonic boundary between the Pacific Plate and the North American Plate.

According to the USGS, the largest historical earthquakes that occurred along the San Andreas fault were in 1857 and 1906, with the latter, estimated at a magnitude 8.3, claiming 700 lives and causing millions of dollars worth of damage in the state.

 San Andreas Fault
A sign posted at the San Andreas Fault, separating the Pacific and the North American tectonic plates near Parkfield, California on July 12, 2019 in a remote part of California but one of the most heavily studied quake areas in the world. FREDERIC J. BROWN/AFP/Getty