A moderate earthquake struck east of Los Angeles on Tuesday and was felt south to the Mexican border and east to Las Vegas.
There were no reports of injuries, major damage or power outages.
The earthquake occurred at 11:42am local time (1842 GMT) about 48km east of Los Angeles in the community of Chino Hills. It was followed by at least two dozen aftershocks.
The quake was initially measured by the US Geological Survey at magnitude 5.8 but was later downgraded to 5.4.