Kind of surprised no one from Southern California mentioned the 5.2 quake that struck near Julian, about 40 miles NE of San Diego around 10:08 am local time today. From the LA Times:
The epicenter was about 3 miles southwest of one of the main mapped segments of the Elsinore fault, and roughly 40 miles northeast of downtown San Diego and 117 miles southeast of downtown Los Angeles.
The Elsinore fault is one to watch for Southern California. The California Geological Survey's fault map shows the greater Elsinore fault zone stretching from the Mexican border through the Riverside County cities of Temecula, Murrieta and Lake Elsinore.
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"The scary part about it is, if [an earthquake] started rupturing where this one did, and it ruptured to the north," shaking energy would be directed into the Los Angeles area, said seismologist Lucy Jones, a Caltech research associate.
One particularly alarming scenario would be an earthquake that starts on the Elsinore fault and continues onto the Whittier fault, producing an earthquake greater than magnitude 7 that is "just going to pour all the energy straight into the L.A. Basin. It's one of the scary earthquakes," Jones said.
Such a quake could trigger worse shaking in Los Angeles than even the much-feared San Andreas fault, as the Elsinore fault is closer to the city.
The immediate repercussions of Monday's temblor were relatively minor, owing to its epicenter being in a remote location, its modest magnitude, and its depth, some 8.9 miles underground.
The most intense shaking was considered somewhere between moderate to strong on the Modified Mercalli Intensity Scale — enough to break dishes and overturn unstable objects, and possibly to overturn heavy furniture. Shaking was considered "light" in downtown San Diego and "weak" in downtown L.A.
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At the San Diego Zoo Safari Park, elephants formed a circle around their young when the ground started shaking.
Definitely check out the SDZ footage of the elephants reacting to the quake — fascinating!
Some people on social media told the U.S. Geological Survey that they got an earthquake early warning — fueled by the ShakeAlert system — on their cellphones.
“That was awesome! GREAT EARLY WARNING!!!” a resident told the USGS’ ShakeAlert social media account on X. “I got the alert on my phone near downtown San Diego several seconds before the primary [shaking] wave hit. WELL DONE!”
This is definitely a big step forward in real-time earthquake warning from when I was a seismic analyst in the area 30+ years ago, even if it’s just a matter of seconds before you start feeling the actual shaking.
It has been 31 years since the magnitude 6.7 Northridge earthquake hit Los Angeles, and 35 years since the magnitude 6.9 Loma Prieta earthquake ruptured under Santa Cruz County, causing extensive damage across the San Francisco Bay Area.
But that quiet period won't last forever.
Fortunately, it doesn’t look like this particular quake is a precursor to the next Big One just yet.
