SAN DIEGO — An earthquake with a preliminary magnitude of 4.1 struck near Palomar Observatory in north San Diego County Sunday morning, according to United States Geological Survey.

The quake was reported at 9:46 a.m. about three miles to the west-southwest of the observatory, USGS reported. The astronomical research center is located atop Palomar Mountain, about 26 miles northeast of Valley Center.

The quake was felt as far south as Chula Vista and as far north as Riverside County, USGS reported. Outside of the mountainous area surrounding the epicenter, shaking was reported most strongly in North County communities like Escondido, Oceanside and San Marcos.

“There were 2 main jolts with a rapid shaking,” the National Weather Service wrote on Twitter.

Representatives for San Diego’s police and fire departments told FOX 5 there were no immediate reports of major damage or injury.

Escondido resident Margaret Moir said she’s lived in the community for 40 years and that Sunday’s quake was “probably the second strongest we’ve felt.”

“My son said, ‘Why don’t you get under the desk?'” Moir said. “And I said, ‘It’s already gone.'”

Seismic readings for earthquakes are sometimes adjusted over time as analysts get more data. In the case of Sunday’s quake, the preliminary magnitude was briefly modified to 4.0, before being bumped back up to 4.1.

FOX 5’s Clara Benitez contributed to this report.