Today, thousands of Bay Area phones chimed in near unison as a ShakeAlert warning flashed across screens after a moderate earthquake struck inland Mendocino County. The familiar drop, cover and hold on tone cut into commutes and coffee runs, even as early word of serious damage was scarce. Across the North Bay, residents reported a brief jolt that rattled pictures and shelves for a few seconds before the shaking faded.
The quake registered as a preliminary magnitude 5.6 and was centered near Redwood Valley in Mendocino County at about 8:10 AM PDT, according to the U.S. Geological Survey. Initial data placed the epicenter roughly 11 kilometers north of Redwood Valley, and the agency noted that its maps and intensity pages will continue to update as additional reports come in.
ShakeAlert push notifications lit up phones across the Bay Area, as reported by KRON4, which also cited the National Tsunami Warning Center in saying there was no tsunami danger. The station reported no preliminary injuries or structural damage, and a KRON4 viewer in Lake County told the outlet the shaking lasted about seven seconds.
Where people felt it
Reactions varied widely. In inland Mendocino, Lake County and Ukiah, people reported clear shaking and some items tumbling from shelves. Closer to the core of the Bay Area, many San Francisco and Peninsula residents said the alert blared but they felt little or nothing at all. The U.S. Geological Survey's citizen-reporting "Did You Feel It?" system will gather those experiences to help map shaking intensity and track any aftershocks.
How the alerts work
ShakeAlert uses a dense web of seismometers and rapid automated algorithms to estimate an earthquake's size and location within seconds, then pushes warnings to phones and critical systems before the strongest shaking arrives. University partners and research labs contribute to the network, and the Berkeley Seismology Lab has detailed how early warning detection ties into public apps like MyShake that tap into the same infrastructure.
If you felt shaking, check yourself and those around you for injuries, move away from broken glass or unstable furniture, and report major damage to local authorities once it is safe to do so. For a quick refresher on basic preparedness steps, including drop, cover and hold on, securing heavy items and assembling an emergency kit, see guidance from the American Red Cross.
If you noticed the quake, you can share your experience through the MyShake app so scientists and emergency managers can refine shaking maps. This story will be updated as officials and seismologists release new information, and KRON4 is continuing to post updates for its readers and viewers.
