A magnitude-4.0 earthquake struck the Bay Area early Monday morning.
According to the U.S. Geological Survey, the tremor occurred at 6:49 a.m. in the Piedmont area of Oakland.
The earthquake was initially reported as a preliminary magnitude of 4.2 but was quickly downgraded. It has been followed by seven aftershocks ranging from 0.9 to 2.39 in magnitude.
According to the USGS, the earthquake just over three miles underground in the vicinity of the Hayward Fault. It was felt in downtown San Francisco, along the Peninsula and in the East Bay.
According to Keith Knudsen, deputy director of the Menlo Park-based Earthquake Science Center, said people reported feeling "intense shaking" because of the quake's shallowness.
BART experienced a major systemwide delay but said that train tracks were not damaged.
The Piedmont Police Department said it felt a quick, sharp jolt but no damage has been reported so far. Fire departments from Alameda and Contra Costa counties as well as the California Highway Patrol said that there have been no calls of any damage or injuries.
A magnitude-4.0 quake can cause light damage, including pictures falling off walls and glasses tumbling off shelves. But its typically not strong enough to threaten structures, Knudsen said.
The last major earthquake on the Hayward Fault occurred in 1868, Knudsen said, adding that such temblors usually take place roughly every 150 years. It's been 147 years so seismologists wouldn't be "surprised" if such an earthquake were to strike the area in the future, he noted.
Knudsen also stressed the importance of being ready for earthquakes by storing enough water for three days, creating a communication plan with family members and investigating whether the buildings in which we spend time are "seismically resilient."
"We use these small events as reminders that we live in earthquake country," Knudsen said. "We should do those things we all know to do to be prepared."