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Quake swarm unleashes 400 tiny temblors on Southern California. What does it mean?

Watch a simulation of an 8.0 earthquake striking California

Here is a simulation of ground motion after a magnitude 8 earthquake on the San Andreas fault, showing ground shaking throughout Southern California for more than 75 seconds after the rupture begins near Parkfield. San Diego Supercomputer Center r
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Here is a simulation of ground motion after a magnitude 8 earthquake on the San Andreas fault, showing ground shaking throughout Southern California for more than 75 seconds after the rupture begins near Parkfield. San Diego Supercomputer Center r

More than 430 tiny temblors have rattled Southern California in the past 10 days or so, some just strong enough to be felt by residents, LAist reports.

But the swarm of earthquakes hitting the Inland Empire, stretching from eastern Los Angeles to the Mojave Desert, probably doesn’t indicate a major quake’s on the way, KTLA reported.

“This is just a place where the earth sputters along instead of letting go all at once,” seismologist Lucy Jones wrote on Twitter.

The two largest quakes, registering 3.4 and 3.2 magnitude, took place Sunday afternoon, KABC reported. Other earthquakes have reached as low as 0.8 magnitude.

FEMA released a video on tips on what people should do in the event of an earthquake.

But Jones wrote on Twitter that even some of the smaller quakes, normally undetectable, may have been felt by residents since most were relatively shallow.

“When the quake is only 1 mile down, instead of 5 miles or more, you are that much closer to the event,” Jones wrote.

While quake swarms sometimes suggest a larger quake may be imminent, seismologist Robert Graves with the U.S. Geological Survey says that’s “highly unlikely” this time, KTLA reported.

“This activity is probably related just to the ongoing tectonic stress that builds up in Southern California and is being relieved on some very small fault structures that do not reach the surface,” Graves said, according to the station.

Jones, writing on Twitter, called the Inland Empire “a perennial hotspot of small quakes.”

“In other words, ordinary, common California quakes,” she wrote.

(Oliver Morrison/The Wichita Eagle)

Researchers recently found that Southern California had experienced 10 times more quakes than previously thought in the last decade, the Los Angeles Times reported.

Almost 90% of the 1.8 million quakes now believed to have hit the region in the past 10 years were too small to be detectable by computing systems, according to the publication.

California is expanding an early earthquake warning system that could give people as long as a minute to prepare for a disaster.

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Don Sweeney has been a newspaper reporter and editor in California for more than 25 years. He has been a real-time reporter based at The Sacramento Bee since 2016.

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