The 5.4 magnitude aftershock, the biggest so far, struck early on Friday local time, in the same desert region as Thursday's 6.4 quake, which damaged roads and buildings and sparked fires.
There have already been more than 80 smaller aftershocks.
The main quake is the largest in southern California since a 1994 magnitude 6.6 earthquake struck a heavily populated area of Los Angeles, killing 57 people and causing billions of dollars of damage.
