Two massive earthquakes rocked Southern California last week, damaging roads and sparking fires but miraculously failing to cause any serious injuries. A magnitude-6.4 earthquake struck in the late morning 10 miles from Ridgecrest, Calif., a city of 27,000 about 125 miles northeast of Los Angeles. It proved to be the foreshock of a second quake the next evening, magnitude 7.1—11 times stronger. The two seismic events were the most powerful earthquakes to hit California in two decades. Phoenix and Las Vegas felt tremors, and the quakes left a fissure wide enough to be seen from space. There were 5,400 aftershocks in the first 100 hours after the 6.4 quake, and experts say 30,000 aftershocks could come by year’s end. Ridgecrest was spared more serious damage because its recently constructed buildings stand on rock, rather than the soft sediment under much of Los Angeles.