A powerful earthquake rocked Southern California on Friday, which at first measurement was stronger than the one that hit on Independence Day and therefore could be the biggest quake to hit the region in 20 years.

The U.S. Geological Survey measured a preliminary 7.1-magnitude earthquake hitting at about 8:20 p.m. local time on Friday about 10 and a half miles from Ridgecrest, roughly 150 miles north of Los Angeles. This is around the same spot where Thursday’s 6.4-magnitude earthquake, now considered a foreshock, hit.