Magnitude 4.6 Earthquake Shakes Santa Cruz County and Wider Northern California

A magnitude 4.6 earthquake struck Santa Cruz County, California, early Thursday morning, jolting residents across Northern California as far away as San Francisco.

The quake occurred at 1:41 a.m. near Boulder Creek, less than a mile from the community, and about 11 miles northwest of Santa Cruz. The U.S. Geological Survey (USGS) reported that the earthquake's epicenter was close to both the San Andreas and Zayante faults—fault lines known for heightened seismic risk in the area.

Initial reports from the earthquake early warning system estimated the magnitude at 4.9, but this was later revised to 4.6 as additional data became available. Jessica Sigala, a USGS geophysicist, explained that quick alerts are issued to maximize warning time, with magnitudes adjusted upon further analysis. Sigala said that aftershocks can be expected in the coming hours and days, though they will likely be less intense.

The California Department of Forestry and Fire Protection’s San Mateo-Santa Cruz Unit confirmed that there were no immediate reports of damage following the shaking. According to the USGS, moderate shaking occurred in communities closest to the epicenter in the Santa Cruz Mountains, sufficient to wake sleepers, while lighter shaking was felt throughout Silicon Valley and weaker tremors reached the wider San Francisco Bay Area.

Residents reported receiving USGS ShakeAlert notifications moments before feeling the quake, illustrating a trend toward increased public readiness during seismic events. Thursday’s event occurred approximately 14 miles northwest of the epicenter of the historic 1989 Loma Prieta earthquake, emphasizing the ongoing seismic vulnerability of the region.

As of Thursday morning, there were no injuries or significant damage reported, and officials indicated that monitoring for aftershocks is ongoing.