A 4-magnitude earthquake struck near the San Francisco Bay area Sunday afternoon. The quake, centered around Concord, California, hit at 3:13 p.m. PDT, according to the U.S. Geological Survey (USGS). This was the strongest in a series of quakes Sunday.

A 2.7-magnitude quake followed about a minute later. Earlier, at 3:01 p.m. PDT, a 2.5-magnitude earthquake hit. A 2.4-magnitude earthquake hit at 3:28 p.m., and a 1.6-magnitude earthquake hit at 3:56 p.m. The quakes were about two-thirds of a mile south of Concord. There were no immediate reports of damage, the San Francisco Chronicle reports.

The series did not strike Rafael Abreu, geophysicist for the USGS, as strange.

“We are in this area that’s very close to a major tectonic boundary,” Abreu said. “When I would be concerned is a week goes by and there’s no quake in California.”