Yes, The 5.5 Earthquake You Felt Was A Ridgecrest Aftershock

Surface ruptures and offsets caused by a magnitude 7.1 earthquake on July 5, 2019 are seen as the sun sets along State Route 178 between Ridgecrest and Trona, California. (ROBYN BECK/AFP via Getty Images)

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The earthquake that hit Southern California around 6:30 p.m. on Wednesday evening was basically an aftershock of last summer's Ridgecrest earthquakes, according to seismologist Dr. Lucy Jones.

The temblor was a magnitude 5.5 centered about 10 miles south of Searles Valley in the Mojave Desert. It originated at a depth of 6.9 kilometers.

"It is indeed an aftershock to the earthquake that occurred last July," Jones told KPCC's Nick Roman. "It's been 11 months since the main shock, and that is actually a pretty common pattern that we see. So when one earthquake happens, it makes other earthquakes more likely. And the bigger it is, the more earthquakes it triggers and the larger earthquakes it triggers. The number dies off with time, but the magnitude doesn't. The relative number of large to small stays the same."

Jones also said 40,000 quakes have occured in the Ridgecrest area since last summer.

As she did when the first big Ridgecrest earthquake happened last year, Jones reminded everyone there's about a 5% chance a larger earthquake will follow.

That's what happened in the summer of 2019.

On July 4, 2019, a 6.4 magnitude earthquake hit the Ridgecrest area. A day later, a 7.1 magnitude earthquake hit the same area. The back-to-back earthquakes destroyed homes and sparked fires, causing $100 million of damage.

An onlooker views newly ruptured ground after a 7.1 magnitude earthquake struck the Ridgecrest area on July 5, 2019. (Mario Tama/Getty Images)

Residents of Ridgecrest and other towns in the Mojave Valley felt aftershocks, including a 4.9 earthquake on July 12, for weeks.

So far, there are no reports of serious damage in Ridgecrest, which is located in the northeast corner Kern County, approximately 150 miles from Los Angeles.

It appears that ShakeAlert issued a message about Wednesday night's earthquake, but it's unclear who received it. Anecdotally, most people in Los Angeles didn't seem to get the alert — but some did.

Julian Lozos was in the San Fernando Valley when he got a warning on his phone. He told KPCC/LAist, "I was admittedly really excited to get the alert, because I haven't gotten one before. I downloaded the apps the day they were released, but hadn't seen them in action until today. It said San Bernardino County, so I knew I had some time. I got up and walked to my kitchen table and got under it, held on and waited. I'm a bad judge of time, but I'd say I felt shaking maybe 10 seconds later."

If shaking from an earthquake doesn't reach a certain threshold, which it may not have in much of Los Angeles county, ShakeAlert won't send a text alert to users.

Ridgecrest residents inspect a recent fault rupture following two large earthquakes near Ridgecrest, California in July 2019 near Ridgecrest, California. (Mario Tama/Getty Images)

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