A 4.1-magnitude earthquake rocked on Monday a remote area in northern San Diego County, about 112 kilometres southeast of Los Angeles.
The temblor struck at 4:35 a.m. local time, said seismologist Anthony Guarino at California Institute of Technology.
Los Angeles police said they received no immediate reports of damages or injuries.
About two hours after the San Diego County earthquake, a magnitude 3.6 quake hit an area about 208 kilometres southeast of San Francisco, according to the US Geological Surveys.
There is no immediate report of damage of injuries from the quake.