A day after a powerful quake rattled Southern California, residents of Ridgecrest were shaken awake Friday morning by a 5.4 magnitute aftershock.
The quake was reported at 4:07 a.m. Friday morning, and the epicenter was Searles Valley again.
The first large quake, a magnitude-6.4, happened Fourth of July morning, with residents reporting feeling it from the high desert to the coast. Damage to the high desert town of Ridgecrest prompted the governor to declare a state of emergency.
The Thursday quake, Southern California's largest magnitude earthquake in the last 20 years, was also centered in Searles Valley, about 150 miles north of Los Angeles. The quake was felt from Las Vegas to San Diego.
It was followed by a swarm of aftershocks ranging from magnitude 2.8 to magnitude 4.2.
The quakes were in the same area that was struck by a magnitude-5.4 quake in 1995. That Aug. 17 earthquake, centered north of Ridgecrest, was followed by more than 2,500 aftershocks during the following five weeks.
On Sept. 20 that same year, a second large earthquake struck the region. At magnitude-5.8, it was likely on the same fault system as the earlier quake. More than 1,900 aftershocks followed the September earthquake.
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In October 1999, one of the largest earthquakes recorded in Southern California was centered in the region. The magnitude-7.1 Hector Mine quake produced shaking throughout SoCal and in parts of Arizona to Nevada from its epicenter in the Mojave Desert. It was in such a remote location that it was named after an open quarry pit and caused little damage, aside from a surface rupture in the Twentynine Palms Marine Base.