Stanislaus County experienced a series of earthquakes Monday evening, including one with a 4.5 magnitude, the U.S. Geological Survey reported.

The earthquakes were centered in the area of Diablo Grande and Westley. There were no reports of injuries or damages.

The earthquakes that were felt on Monday were the most notable and sizeable but were not the first the western area of Stanislaus County has been experiencing of recent. Since the last week of August the region has had a sequence of earthquakes that is up to 18 at this point, said USGS Research Geologist Chad Trexler.

“They have mostly been small, so they haven’t been felt,” Trexler said.

Trexler said the earthquakes haven’t come from a single fault line but rather activity from the Greenville Fault that runs through the interior of Diablo Grande and the Great Valley Fault System, which runs along the western edge of the San Joaquin Valley.

“Earthquakes out in that area are not super common but not unprecedented,” Trexler said. “In the last 30 to 40 years there have been dozens of earthquakes out there, they’re just not necessarily ones that people feel.”

The first earthquake that most people reported feeling hit at 5:15 p.m. Monday and was a 4.0 magnitude, about 14 kilometers south-southwest of Westley with a depth of 0.1 kilometers.

The largest of the quakes on Monday hit at 9:13 p.m. Monday and was a 4.5 magnitude, 15 kilometers from Westley and a depth of 3.5 kilometers.

“The big take away from this is that though this wasn’t on a fault like San Andreas that always gets talked about, it is a reminder that there are other faults in California and people should be prepared,” Trexler said.

The USGS manages ShakeAlert, an earthquake early warning system. detects significant earthquakes quickly enough so that alerts can be delivered to people and automated systems potentially seconds before shaking arrives. The purpose of the system is to reduce the impact of earthquakes and save lives and property. To learn more about ShakeAlert and to sign up for it, visit usgs.gov/ShakeAlert.

Ready.gov/earthquakes advises people to prepare for an earthquake by creating a family emergency communications plan that has an out-of-state contact. Plan where to meet if you get separated. Make a supply kit that includes enough food and water for several days, a flashlight, a fire extinguisher and a whistle.

To read more earthquake safety tips and preparation advice, visit ready.gov/earthquakes.