5.1 magnitude earthquake jolts southern California amid Hilary hurricane

Local officials said Sunday that an earthquake of 5.1 struck near Ojai, sending tremors to southern California, followed by four aftershocks with no damage reports received yet.

"There are no immediate reports of damage at this time however the quake was felt extensively throughout Ventura County," county emergency officials said.

The US Geological Survey reported there were at least four aftershocks of magnitude-3.0 or greater. 

The quake was centered four miles southeast of Ojai and 10 miles northeast of Ventura in a remote area of Sulphar Mountain — 60 miles northwest of downtown Los Angeles — and the tremors were felt in Malibu, Porter Ranch, parts of Los Angeles, Manhattan Beach and other locations.

The Ventura County Sheriff's Department did an aerial survey of Lake Casitas Dam, Matilija Dam and the city of Ojai and observed no damage.

Seismologist Dr Lucy Jones told the US media that "this location is interesting to have it there."

"This is first time we've had a 5 since 1932 in exactly this location, and even within the Ventura basin," Dr Jones said, adding that a magnitude 5.1 earthquake was reported in 1941 west of Sunday's quake. Some of the 1994 Northridge Earthquake aftershocks were east of the location.

Scott Thomsen, Ventura County Fire director of communications, said the department immediately implemented its earthquake plan that involves getting the trucks out of the firehouses. 

He added that "so far we have no reports of damage but we are checking."

He noted that the earthquake came just as officials were bracing for Tropical Storm Hilary.

“We are in the middle of the first tropical storm since 1939, and we just had an earthquake,” he said.

The calculations by the USGS suggested that the intensity of the earthquake was considered moderate based on the Modified Mercalli Intensity scale — enough to break windows, overturn unstable objects and stop pendulum clocks.

The county officials said the earthquake occurred along the Sisar fault system.