Update: The magnitude of the earthquake was raised from 4.0 to 4.1.

The US Geological Survey said that a 4.1-magnitude earthquake was felt early on Sunday in northern San Diego County.

In 9:46 a.m., the epicenter was at Palomar Mountain State Park, 4.8 kilometers from the Palomar Observatory and 18 miles northeast of Escondido. The Elsinore fault zone is close by.

The USGS Did You Feel It website received 650 replies in less than 10 minutes from as far away as the Salton Sea and the Mexican border, as well as from the counties of Riverside and Orange.

Since the 4.8 on January 5 near Deep Springs, Inyo County, it was the biggest earthquake to hit California. It was also the biggest earthquake to hit San Diego County since the 4.2 in October 2012 at Oktillo Wells.