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By Hannah Parry
Associate News Editor
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A magnitude 5.6 earthquake struck Northern California on Wednesday, with shaking felt more than 100 miles away, according to the U.S. Geological Survey (USGS).
The quake, centered in Redwood Valley, north of San Francisco, struck at around 8.10 a.m. PT (11.10 a.m. ET) at a depth of 5 miles (8.1 kilometers).
California Governor Gavin Newsom’s office confirmed he had been briefed and was monitoring the situation.
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“Governor Newsom has been briefed on reports of an earthquake in Mendocino County. The Governor’s Office is closely coordinating with emergency officials and assessing potential impacts and damage,” the office wrote on X.
Newsweek pet reporter, Elizabeth O'Connell, was in a coffee shop in Fort Bragg, in Mendocino County, this morning when the quake struck.
"My mouth dropped because I had no idea what was happening," O'Connell, who is originally from Pennsylvania, said. "The baristas said something along the lines of 'oh yeah, earthquake.'"
O'Connell added that she heard the building creak and alarms began going off, but said that everyone else was "totally unfazed."
Fawnell Dale, a dispatch supervisor at the Mendocino County Sheriff’s Office, told AP that the shaking had been mild and the sheriff's office hadn’t gotten any reports of any damage or injuries.
Staff at Mendocino Coast Pharmacy were preparing to open when they received quake alerts on Wednesday morning.
“We looked at our phones, then we looked at each other, and that’s when we felt it,” Angie, who declined to give her last name, told AP. She said the rolling shake had lasted just a few seconds. "It wasn’t that big, but it was a little scary,” she said.
California residents in the area received earthquake alerts warning them that "strong shaking" was expected and urging them to "drop, cover, hold on."
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On social media, some joked that the effects were milder than the warnings suggested, with one user saying, "Good thing I stopped my zoom meeting to drop and cover, almost died today," while showing a lamp barely swinging on its chain.
"If you blinked you missed the shake," said one person from California, who claimed the mountains kept the shaking to a minimum.
Another posted about timing of the alert, saying, "OK, wow — my phone gave me an earthquake warning 20 seconds before I felt any shaking."
Where Was the Earthquake Felt?
The quake's epicenter was Redwood Valley, north of San Francisco, around 50 miles inland. It struck at a depth of 5 miles.
A quake map, from USGS, shows that people near the epicenter in Redwood Valley experienced strong to severe shaking this morning.
The earthquake was felt widely, including in the fishing city of Fort Bragg.
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Was There an Aftershock?
The magnitude 5.6 earthquake was followed by at least 12 much weaker 2.5 magnitude aftershocks within an hour.
Aftershocks are common following major earthquakes, but even smaller quakes can result in secondary quakes as stress adjusts along the fault line.
They typically occur within minutes of the initial earthquake, but tremors can occur hours or days later, typically at a weaker magnitude than the initial incident.
When Was California's Last Major Earthquake?
While today's earthquake was significant, the last major quake—defined as being a magnitude 7 or more—hit California in 2019.
The Ridgecrest earthquake was a powerful earthquake sequence that struck the Mojave Desert near Ridgecrest, California, on July 4 to 5, 2019. It began with a magnitude 6.4 quake on July 4, followed about 34 hours later by a larger magnitude 7.1 earthquake, which became the mainshock. The shaking was felt across much of California and was the state's largest earthquake in two decades.
Despite its size, damage was limited because the epicenter was in a sparsely populated area. The quake caused cracked roads, structural damage, power outages, and significant impacts at the nearby Naval Air Weapons Station China Lake, but no direct fatalities. Scientists also found the event unusual because it involved a complex network of intersecting faults rather than a single fault rupture, making it one of the most closely studied earthquake sequences in modern California history.
California Fault Stress Hits Highest Level in 1,000 Years
Wednesday's powerful quake comes after new research, led by earth scientists at the University of Hawaiʻi at Mānoa, found that tectonic stress along the San Andreas and San Jacinto fault systems in Southern California has climbed to the highest level seen in the past millennium.
Lead author Liliane Burkhard told Newsweek last week that the results showed that several fault segments are in a “critically loaded state."
"The most important thing to understand is that this is not a distant, theoretical risk," Burkhard added. "The stress that drives large earthquakes has been building continuously since 1857, and our model shows it has now exceeded anything we have seen in a thousand years of earthquake history.
"That does not mean an earthquake will happen tomorrow, but it does mean the system is as loaded as it has ever been in our record, and that the question is not really if but when. For anyone living in Southern California, that is a reason to take preparedness seriously, to know evacuation routes, to have a communication plan with friends and family, to have an emergency kit with water, food, and medication ready."
Burkhard added that Cajon Pass—a critical junction between the faults— may act as "an ’earthquake gate:’ sometimes blocking large ruptures from crossing between the faults and sometimes allowing them to pass through and involve both systems in a single event.”
Contact Newsweek editors on this story: Gabe Whisnant and Gray R. Thomas
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