4.6 Earthquake Jolts Boulder Creek Before Dawn
No injuries or damage reported; USGS puts odds of a felt aftershock at 60% within the week
An earthquake rattled Boulder Creek and surrounding areas early Thursday morning, waking residents across the Santa Cruz County and knocking items off shelves near its epicenter. The U.S. Geological Survey (USGS) placed the final magnitude at 4.6 striking at 1:41am just east of town at a depth of 6.8 miles.
More than 25,000 people filed shaking reports with the USGS within hours, spanning from Sacramento to King City. USGS ShakeAlert sent alerts to phones seconds before the ground moved. No injuries have been reported. CAL FIRE CZU enacted its earthquake procedure and inspected all of their fire stations and buildings with no damage detected.
The epicenter sits just west of the San Andreas Fault, though multiple fault strands lace the Santa Cruz Mountains, including the Zayante, San Gregorio, and Sargent faults. The area has generated damaging earthquakes in 1838, 1865, 1906, and the magnitude 6.9 Loma Prieta disaster on October 17, 1989, which killed 63 people across the Bay Area and caused severe damage in Boulder Creek and throughout Santa Cruz County.
The USGS aftershock forecast gives roughly 60% odds that at least one magnitude 3.0 or greater earthquake will strike the same area within the next seven days. The chance of a magnitude 4.0 or greater aftershock is about 14%; a magnitude 5.0 or greater sits near 2%. The agency expects the forecast to shift most rapidly in the first 72 hours. As of 6 a.m. Thursday, no aftershocks had been recorded.
USGS seismologist Robert de Groot told ABC7 News: “There are on the order of 50 earthquakes a day in California. These magnitude earthquakes don’t happen very frequently, but they happen frequently enough that there are these reminders that we do live in earthquake country.”
Residents near the epicenter are encouraged to inspect their properties in daylight for cracked drywall, chimney damage, or signs of foundational shifting. If a felt aftershock occurs: drop, cover, and hold on. Live earthquake data and the updated aftershock forecast are available at earthquake.usgs.gov.
Seismic data sourced from USGS and ShakeAlert.
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