SOUTHERN CALIFORNIA, Sept. 14 (Our California Times) — A cluster of dozens of small earthquakes shook parts of Southern California over slightly more than 18 hours, according to earthquake records from the U.S. Geological Survey. The events were concentrated near Lennox and Westmont in South Los Angeles, with reported magnitudes ranging from 1.0 to 2.7.
The activity occurred near the Newport-Inglewood Fault Zone, a major fault system that runs through the Los Angeles region. But the available records do not establish that a mapped section of that fault caused the earthquakes. They also do not show that the swarm changed the region’s broader earthquake risk.
What happened?
The reported sequence began at about 8 p.m. Friday and continued until about 2:30 p.m. Saturday. Residents in Lennox, Westmont, Hawthorne, Inglewood and other South Los Angeles communities reported light shaking.
The exact number of events depends on the catalog snapshot and the geographic area counted. Reports based on USGS records described the activity as “dozens” of earthquakes. Other accounts cited totals of about 90 or 93 events. Still other counts included a broader area and reported more than 60 or more than 80 earthquakes.
The supplied records do not establish whether those totals used the same boundaries, time period or minimum magnitude. The most consistent details are the location around Lennox and Westmont, the roughly 18-hour period and the magnitude range of 1.0 to 2.7.
What is a swarm?
An earthquake swarm is a group of earthquakes that occurs in a relatively small area over a short period. Unlike a typical mainshock-aftershock sequence, a swarm may not have one clearly dominant earthquake followed by smaller events.
Small earthquakes are common in California. Many are too weak to be felt, although a group of them can draw attention when they occur close together or near populated areas. The magnitude scale is logarithmic, meaning that each whole-number increase represents a much larger earthquake, not simply one that is a little stronger.
Is the Newport-Inglewood Fault Zone responsible?
The events were reported near the Newport-Inglewood Fault Zone, which extends through the Los Angeles region toward Newport Beach before continuing offshore. A scientific explainer using USGS data describes the zone as a fragmented stretch about 40 miles, or 65 kilometers, long.
Being near a fault zone does not by itself prove that the earthquakes occurred on a particular mapped fault. One account said the specific fault or underground structure responsible for the events had not been confirmed. The available material does not provide the earthquake depths, detailed fault-plane solutions or a direct statement from a seismologist identifying the source structure.
That distinction matters because earthquake locations are estimates, and several faults or smaller cracks can exist in the same area. A location near a known fault system is evidence of geographic proximity, not proof of cause.
Does the swarm signal a larger earthquake?
The available information does not answer that question. No official forecast, hazard assessment or change in earthquake probability was included in the records supplied for this event.
A swarm can stop after hours or continue longer, and small earthquakes do not by themselves establish that a larger earthquake is about to occur. Any conclusion about future risk would require analysis of the complete seismic sequence and the local fault structure by earthquake scientists.
No peer-reviewed study about this particular swarm, named research team, formal uncertainty estimate or independent replication was supplied. The information currently available is an earthquake-catalog account of what happened, not a completed scientific study testing why the sequence occurred or what it means for future earthquakes.
What is known now?
The strongest conclusion is limited but clear: Southern California experienced a concentrated burst of small earthquakes near Lennox and Westmont, and some people in nearby communities felt light shaking. The activity was near the Newport-Inglewood Fault Zone, but the available records do not confirm that the zone itself generated the events.
The swarm’s occurrence does not, on its own, demonstrate a new hazard, predict a major earthquake or prove a change in the region’s long-term earthquake risk.
