The first quake, registering at a magnitude-2.6, struck around 9:27 p.m. at a depth of less than two miles. At least 18 other quakes hit the same area within about 20 minutes.
A magitude-2.6 quake was the last to hit around 10:01 p.m. at a depth of nearly two miles. The weakest ones to strike measured at 2.5.
The quakes occurred in the same region where a magnitude-5.3 quake hit on Saturday.
There were no immediate reports of damage or injuries.
The Brawley Seismic Zone has started up again tonight, slightly north of last Saturday's events, as though the fault extended a bit to the north. Looking back, a similar extended swarm happened in 1978. Like I said last week, they continue until they stop.— Dr. Lucy Jones (@DrLucyJones) June 12, 2021
The Associated Press contributed to this report.