Back-to-back small earthquakes jiggled the Sacramento Valley on Sunday morning — shakes hardly felt in an area of Northern California that rarely receives shaking.
A magnitude 3.8 earthquake occurred at 6:44 a.m. and was centered about 10 miles east of Willows in Glenn County, according to the U.S. Geological Survey. It was the largest quake on the Sacramento Valley floor since 1968, according to USGS records, and the strongest temblor in interior Northern California since a magnitude 5.7 quake struck the shores of Lake Almanor in 2013.
That was followed by a magnitude 2.5 temblor in the same area at 6:59 a.m. The quakes were about 20 miles west of Oroville, 20 miles south-southwest of Chico and 27 miles northwest of Yuba City.
Still, few people noticed.
It didn’t make a dent in the Sunday routine of Four Corners Market about a mile from the epicenter at the junction of Highways 45 and 162. Store clerk Skylar Fry said no one there felt a thing: “We must’ve all been too busy.”
“I had all my coffee guys here, and nobody noticed,” she said, adding that a woman had later come into the store and said she had felt it.
There were no reports of damage. Dispatchers at the California Highway Patrol’s Chico communication center and at the Yuba City Police Department said they had not received any calls.
The earthquakes’ epicenter was about a mile northwest of Butte City near Highway 45/162 and County Road 56, and was in an orchard several yards from the Sacramento River, according USGS preliminary reports. The larger quake had a depth of 15 miles below the surface.
According to the USGS’ “Did You Feel It” reporting system, fewer than 250 respondents were recorded by 7:10 a.m., with most respondents reporting “weak” or “light” shaking. Responses came from area near the temblors, as well as Chico, Marysville, Sacramento and Roseville.
Several users on social media said they felt the quake in places like Live Oak and Grass Valley, but only a little.
“It was unlike your typical earthquake,” wrote one user, Kimberly Hogan. “There were two percussions, first a small one and then a larger one. It knocked the house, woke everyone up and sent the cats running scared.”
“There was no shaking or rattling or movement. It felt like a giant knock to the house.”
Another user, Ian Leff, said it was “fairly strong in Yuba City but over very quickly,” making it hard to identify as an earthquake.
Earthquakes in the Sacramento Valley are exceedingly rare, and typically small. In the area around where Sunday’s earthquakes occurred, the USGS says only 14 other quakes of magnitude 2.5 or greater have happened in 10 years.
A magnitude 5.0 earthquake struck about four miles north of Sunday’s epicenter on April 28, 1968. That Sunday quake hit at 5:22 p.m. and was “felt over approximately 10,500 square miles, principally in Butte, Glenn, and Tehama Counties. Principal damage was to merchandise in stores. Glass door broke at Chico. Plaster cracked at Willows. A well west of Tehama reportedly went dry,” according to USGS seismologists in a summary of 1968’s earthquakes.
The Bee reported on the front page of the next day’s newspaper little damage from “real sharp” tremors — the quake tumbled copies of reports from the shelves in the state Capitol and had thrown a woman from her bed in Colusa.
A map of all significant earthquakes statewide from 1800 to 1999 shows there were no earthquakes magnitude 5 or higher with epicenters in the lower Sacramento Valley. The closest came in Solano County with 1892’s Vacaville-Winters earthquake, which was estimated to be a magnitude 6.4.
Last year, The Bee examined the Sacramento area’s earthquake risk in response to a reader question. Seismology experts and a professor who studies earthquake engineering told The Bee that the region’s earthquake risk is minor compared to the Bay Area or Los Angeles.