Nearly 100 small earthquakes shook South Los Angeles in less than a day, part of a wider cluster of tremors rattling Southern California this week.
Quick Take
- The U.S. Geological Survey recorded 90 small quakes near Lennox and Westmont from Friday night into Saturday morning.
- Magnitudes ranged from 1.0 to 2.7, with the strongest jolts felt across South Los Angeles.
- The cluster spread beyond city limits, including a 2.6 quake near Inglewood and a 3.4 quake near Avalon.
- Scientists call this pattern an “earthquake swarm,” a known and recurring type of activity in California.
A Sudden Burst Shakes South Los Angeles
The United States Geological Survey recorded 90 small earthquakes around unincorporated Lennox and Westmont starting at 8:05 p.m. Friday and continuing into Saturday. The quakes ranged in magnitude from 1.0 to 2.7. Residents in the area felt repeated shaking through the night, though the tremors stayed small enough to avoid major damage reports.
The New York Post described the burst as dozens of earthquakes striking Southern California on Saturday, with the heaviest activity concentrated in South Los Angeles. The sudden cluster included a 2.7-magnitude quake centered in the Westmont area, matching the strongest events logged by federal seismic monitors that same weekend.
Wider Cluster Spreads Across the Region
Live USGS mapping tools confirmed multiple nearby events, including a 1.9-magnitude quake 4 kilometers southeast of Lennox and another 5 kilometers northwest of East Los Angeles, both logged early Saturday morning. These entries lined up with the broader swarm reported by local outlets, showing the shaking was not limited to one single spot.
The activity did not stop at city borders. A preliminary 2.6-magnitude quake struck near Inglewood at 4:32 a.m. Saturday, while a 3.4-magnitude quake hit 26 kilometers southeast of Avalon later that morning, making it the largest quake logged for the Los Angeles area in the past month.
Statewide tracking added more context. The USGS reported 31 earthquakes of magnitude 2.5 or greater across California in a single day, and a separate 3.4-magnitude quake had already rattled the Ontario area earlier in September, shaking parts of San Bernardino County.
Why Scientists Call This a “Swarm”
Seismologists classify clusters like this one as earthquake swarms rather than a typical mainshock-and-aftershock sequence. Swarms lack one dominant large quake. Instead, they feature many similarly sized tremors that can start, stop, and restart without warning, making them harder to summarize than a single big event followed by smaller ones.
We have an earthquake swarm currently in process in the Los Angeles Basin. No major quakes yet, but over 100 minor ones in that large cluster. Consider how the massive erosion that struck many SoCal beaches transported tons of sand to new locations and altered mass distribution. pic.twitter.com/kzHx4TQ6LF
— Stefan Burns (@StefanBurnsGeo) September 13, 2026
California has a long history of these swarms. Similar clusters have hit the San Ramon Valley repeatedly since 1970, and a four-year swarm near Cahuilla was later linked to natural underground fluid movement rather than a single fault rupture. Researchers say swarms are common enough that they rarely signal an imminent major quake.
The Southern California Earthquake Data Center at Caltech continues to track the region using a live feed that updates every five minutes, drawing from the same network the USGS relies on. No major damage or injuries have been reported from this week’s cluster, and monitoring continues as the sequence plays out.
Sources:
nypost.com, latimes.com, earthquakelist.org, earthquake.usgs.gov, earthquake.ca.gov, earthquaketracker.org, scedc.caltech.edu