The California National Guard was sending 200 troops, logistical support and aircraft after a 7.1-magnitude earthquake hit South California on Friday evening, said a senior officer on Saturday.

David Baldwin, major general of California Military Department, said the Pentagon had been notified and the entire California Military Department was put on alert.

Friday's temblor was centered near Ridgecrest, a city in Kern County located 272 km north of downtown Los Angeles. It is the largest Southern California quake in at least 20 years and was followed by a series of large and small aftershocks.

The powerful quake came only one day after a 6.4-magnitude earthquake struck the region on Thursday morning.

The two major earthquakes and the aftershocks have caused significant damage to many local businesses and damage assessments are ongoing, said California Governor's Office of Emergency Services on Saturday afternoon.

All roads are open near the Ridgecrest earthquakes and aftershocks, including California State Road 178, which was re-opened after emergency temporary repairs, said California Department of Transportation. "Heavy equipment will be used to make permanent repairs."

The two earthquakes caused widespread structural damage to roads, waterlines and gas lines, which resulted in some structural fires in the regions. No fatalities have been reported.