Southern California Earthquake
Magnitude 3.7 Earthquake Shakes Southern California Communities Near Dana Point
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Key Points
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The USGS initially reported the main quake as magnitude 3.5 before revising it upward to 3.7.
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The USGS had received 30 online felt reports for the main quake, with weak shaking reported in communities including La Mesa, San Diego and Escondido.
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The magnitude-2.8 aftershock was centered about 20 miles southwest of Dana Point at a depth of 10 miles; six people had submitted felt reports.
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How strongly the quake was felt depended not only on its magnitude and distance from a person, but also on local soil conditions: looser soil can amplify shaking.
A magnitude-3.7 earthquake struck Southern California on Monday afternoon, centered about 18 miles southwest of Dana Point at a shallow depth of roughly 5 miles. NBC Los Angeles reported that light shaking rippled across San Diego-area communities including La Mesa and Escondido. The USGS initially measured the quake at magnitude 3.5 before revising it upward to 3.7.
A magnitude-2.8 aftershock followed about a minute later, centered roughly 20 miles southwest of Dana Point at a depth of 10 miles. NBC Los Angeles noted that earthquakes of these magnitudes are typically felt by people but cause little to no structural damage. The USGS received 30 felt reports for the main quake and six for the aftershock.
Why Some Areas Felt It Harder Than Others
The strength of the shaking depends on three factors: magnitude, distance from the epicenter, and local soil conditions. USGS data shows that looser soil can amplify ground motion, making the same earthquake feel stronger in some neighborhoods than others. This is why residents in different parts of San Diego and Orange counties reported varying levels of shaking intensity.
USGS Revised Its Initial Magnitude Estimate Upward
The USGS first reported Monday's earthquake as magnitude 3.5, then revised the measurement to 3.7 after processing additional seismic data. Such revisions are routine—early estimates rely on preliminary readings from nearby sensors, while final measurements incorporate data from a broader network of stations. NBC Los Angeles tracked the revisions as the USGS released updates.
Light Shaking Reported Across Three Counties
Communities from San Diego to Orange County felt the quake on Monday at 1:20 p.m. Felt reports came in from La Mesa, Escondido, and other neighborhoods near the epicenter. NY Post reported that shaking was felt as far south as San Diego and east into inland communities, confirming the quake's wide reach across the region.
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