6.4-magnitude quake hits California, strongest in 20 years  

A massive earthquake measuring 6.4 on the Richter scale jolted a remote area in California's Searles Valley, the strongest temblor to hit the US state in 20 years.

The quake struck at 5.33 p.m. on Thursday and was initially determined to be at 35.70 degrees north latitude and 117.51 degrees west longitude, according to the U.S. Geological Survey (USGS).

The nearest city rocked by the quake is Ridgecrest, which has a population of 28,000 and is located about 18 km southwest of the epicenter and 250 km northeast of downtown Los Angeles, reports Xinhua news agency.

Ridgecrest Mayor Peggy Breeden declared a state of emergency. She said crews were responding to at least five fires across the city and that crews were assessing broken gas lines.

The quake was felt across the Los Angeles region. Many local residents tweeted that they felt the shakes and steady sways which lasted for almost 30 seconds but not so strong like in 1994, when a 6.7 magnitude earthquake hit Northridge area of Los Angeles and killed 57 people.

"At this time, the LAPD has not received any reports of damage or calls for service within the City of Los Angeles related to the #earthquake. Remember, 911 is only to report emergencies. This was a strong one, and a good reminder to be prepared," the Los Angeles Police Department tweeted.

"Been fully briefed on earthquake in Southern California. All seems to be very much under control!" President Donald Trump tweeted later.

In San Bernardino County, the quake broke water mains, downed power lines, cracked buildings and caused cracks on roads, local ABC 7 news channel reported.

Seismologist Lucy Jones from California Institute of Technology (CalTech) said that the quakes' damage was limited since the epicenter was in a remote area.

She said that CalTech received a 48-second warning that the quake was coming, however, users of the Shake Alert, an app designed for earthquake alarm to residents, did not receive an alert because the quake in Los Angeles measured only a magnitude of 4.5, which is under the 5.0 threshold required for an alert.

She also said the quake occurred on a strike fault about 16 km from Ridgecrest instead of the San Andreas fault, an area with a lot of faults but not long fault.

The San Andreas Fault, a continental transform fault that forms the tectonic boundary between the Pacific Plate and the North American Plate, extends some 1,300 km through California.

Many researches predicted that it could generate a large-scale earthquake in southern California.

Dozens of aftershocks were recorded by the USGS near Searles Valley.