However, the other three were weaker than Friday' 3.2 magnitude tremor. Concord sits just five miles from the Hayward Fault, a 74-mile fault line that runs along the foot of the East Bay hills.

The 13-story Warren Hall was built about 2,000 feet (600 metres) from the Hayward Fault, which researchers consider one of the most dangerous fault lines in the country.

West Oakland, Calif., on Thursday, July 22, 2021. (Jane Tyska/Digital First Media/East Bay Times via Getty Images) "Large earthquakes on the Hayward fault have happened before and will happen again.

In a 2018 report, the U.S.G.S. looked at what would happen if a magnitude 7.0 earthquake occurred on the Hayward Fault and estimated that 800 people would die and 18,000 would be injured from ...