A magnitude 5.6 earthquake struck Northern California on Wednesday at 11:10 a.m. ET, sending shockwaves that were felt across California, Nevada, and Oregon. The U.S. Geological Survey (USGS) reported the epicenter was located less than 120 miles north of San Francisco, near Redwood Valley.
The tremors traveled more than 600 miles, reaching Coos Bay, Oregon, to the north and Salinas, California, to the south. This included the entire San Francisco Bay Area, home to over seven million people, affecting cities such as San Jose, Sacramento, Concord, Oakland, Stockton, and Modesto. Some residents described the shaking as intense, with one individual in Ukiah stating it was the largest earthquake they had experienced in their 54 years of living there.
Officials sounded the earthquake alert system for tremors stronger than magnitude 4.5. While the strongest shaking reached level seven in some areas, indicating "very strong" shaking and the potential for moderate damage, no injuries have been reported at this time. Several aftershocks, all measuring stronger than magnitude 2.0, were recorded in the hours following the initial quake.
The earthquake's epicenter was identified within seven miles of the Maacama Fault zone. This fault is a significant, active strike-slip fault known for its potential to cause strong shaking and damage in Mendocino and Sonoma counties. The Maacama Fault is part of the larger San Andreas Fault system.
USGS scientists have previously warned about the seismic activity in the region. According to a 2015 report, there is a 95 percent probability that at least one major earthquake, exceeding magnitude 6.7, will occur in the Bay Area by 2043. The agency has also issued warnings regarding aftershocks, estimating a nearly 90 percent chance of another earthquake stronger than magnitude 3.0 occurring in the next week, a 40 percent risk of a quake stronger than magnitude 4.0, and a seven percent chance of another quake exceeding magnitude 5.0.
In response to the seismic event, the California Governor's Office of Emergency Services issued a 'drop, cover, and hold on' warning through the MyShake App to approximately 657,000 people. The American Red Cross provided guidance on these safety measures, emphasizing that dropping to the ground protects individuals from being knocked over, covering the head and neck shields against falling debris, and crawling under sturdy furniture or moving to an interior wall can provide further protection. Holding on until the shaking stops is the final step in this safety protocol.