A moderate earthquake measuring 5.2 on the Richter scale struck Southern California on Monday morning, sending ShakeAlert warnings to mobile phones across the region. The tremor was centred near Julian, a small mountain town with around 1,500 residents, located in San Diego County.
While the quake caused minor damage, it served as a reminder of the region’s ongoing seismic activity.
Where and When Did the Earthquake Strike?
Time of Earthquake: Just after 10 a.m. (local time)
Epicentre: Near Julian, San Diego County
Depth: Approximately 8 miles (around 14 kilometres) below the surface
Despite being relatively deep underground, the tremor was strong enough to be widely felt. Residents reported:
Items falling off shelves
Boulders tumbling onto rural roads
A general jolt across the region
ShakeAlert: Why Your Phone Buzzed with an Earthquake Warning
As the ground shook, ShakeAlert, the region’s early warning system, quickly issued alerts to mobile phones. Interestingly, the initial alert listed the quake as magnitude 6.2, which was later corrected to 5.2.
Why the Mistake?
According to Allen Husker from the Southern California Seismic Network:
“The alerting system prioritises speed over precision. Its main goal is to warn people of possible danger as soon as possible.”
What Seismologists Are Saying
Experts confirmed that this quake was not unexpected and may be linked to the Elsinore Fault, one of Southern California’s most active fault lines. It runs parallel to the more famous San Andreas Fault.
Was There a Warning Sign?
Yes. According to renowned seismologist Lucy Jones, a 3.5-magnitude foreshock hit the same area just the day before:
“There was a foreshock to this earthquake. The chance that this 5.2 would itself be a foreshock to something bigger is still the same — about a 5% chance.”
Depth Matters
Gabrielle Tepp, a seismologist at Caltech, explained that the depth of the quake made a difference:
“If you have an earthquake that’s very shallow and right under your feet, it’s going to feel a lot stronger than one that’s 14 kilometres below.”
Is There a Risk of a Bigger Earthquake?
While the 5.2-magnitude quake startled many, seismologists are not expecting a larger event to follow. However, they advise the public to stay prepared, as Southern California remains a seismically active region.
Key Takeaways
A 5.2-magnitude earthquake struck near Julian, San Diego County, on Monday morning.
ShakeAlert warnings were quickly sent to mobile phones, although the system briefly overestimated the quake’s strength.
Minor damage was reported, including falling items and loose boulders.
The quake likely occurred along the Elsinore Fault, one of the region’s major fault lines.
Experts advise staying informed but not panicking, as a larger quake is unlikely but not impossible.
Sources
ABC7 Los Angeles – Source Article
USGS – United States Geological Survey
Southern California Seismic Network
Caltech Seismology