Dozens of earthquakes shook parts of Southern California over the weekend. The phenomenon is called a swarm.
The Los Angeles Times said that the swarm of 90 small quakes rattled South Los Angeles on Friday and Saturday.
They were all near the Newport-Inglewood Fault and followed a 3.2 quake on the same fault.
The Newport-Inglewood Fault line runs from Culver City to Newport Beach.
Saturday, September 12, 2026, 3:55 PM: There have now been over 70 small earthquakes in the Lennox, California region in the last 24 hours. I’m watching this swarm very closely as it crosses over the Newport-Inglewood Fault. #CAwx #earthquake #LosAngeles pic.twitter.com/ULa3VEk7gP
— Jason D Farhang (@jason61987) September 12, 2026
So when does a series of earthquakes become a swarm?
The U.S. Geological Survey said there isn’t a definition for when a mainshock or aftershock becomes a swarm.
“The “swarm” designation is typically applied when we observe relatively many earthquakes within a relatively small area, which just don’t fit the pattern of a mainshock-aftershock sequence," the agency said in 2019.
© 2026 Cox Media Group
