A recent 4.4-magnitude earthquake that rattled Los Angeles has raised concerns over the lesser-known Puente Hills fault system. The Puente Hills fault system stretches from the southern San Gabriel Valley through downtown L.A. and out to Hollywood.
I need to clarify about seismicity rates in SoCal. Long term average since 1932 is ~10-12 M4s /yr. In the last 20 years, we have averaged about 5 /yr. So far in 2024, we have had 13 M4s. So lots of variability but 2024 is closer to normal than the quiet of the last 2 decades
— Dr. Lucy Jones (@DrLucyJones) August 13, 2024
Unlike the famous San Andreas Fault, the Puente Hills fault is a complex web of buried faults posing significant risks due to its location under densely populated areas.
LA kids learn the ultimate LA lesson on first day of school https://t.co/KdrUJwkh6E
— Shelby Grad (@shelbygrad) August 13, 2024
Seismologist Lucy Jones said, “We get about an order of magnitude more damage from a Puente Hills earthquake than from a San Andreas earthquake because so many people live so close. Buildings in the older parts of L.A. aren’t built to withstand earthquakes.”
Good morning Southern California! Did you feel the magnitude 3.9 quake about 4 miles west of Lake Elsinore at 9:39 am? The #ShakeAlert system was activated. See: https://t.co/xcuJ7KFNfm @Cal_OES @USGS_Quakes @ListosCA @CAGeoSurvey pic.twitter.com/CXWW244kxt
— USGS ShakeAlert (@USGS_ShakeAlert) August 15, 2024
Monday’s quake occurred along the same fault system responsible for the deadly 1987 Whittier Narrows earthquake, which claimed more than half a dozen lives and caused more than $350 million in damage. Since then, the Puente Hills fault system has been relatively quiet.
However, Southern California has seen increased seismic activity this year, bringing renewed attention to the risks posed by various fault lines. Jones said, “We’re thinking about the Puente Hills fault system because we had the earthquake right now. But everyone in Southern California lives within five miles of an active fault.”
Residents are encouraged to be prepared with an earthquake kit and to stay informed about earthquake safety measures.
This year, Southern California has endured more sizeable quakes than it has in decades, leaving residents on edge. The jarring trend continued Thursday with a magnitude 4.4 earthquake centered near Highland Park, the region’s 13th quake of magnitude 4.0 or greater, according to Dr.
Puente Hills fault system risks
Lucy Jones, a seismologist with the California Institute of Technology in Pasadena. Jones noted, “So, this is an active year, much like we used to see. It does seem like we should expect this to continue at a higher rate.”
Since 1932, the average number of earthquakes with magnitudes of 4.0 or greater in Southern California is between 10 and 12 annually, making the recent quake drought an anomaly.
The rate of seismic activity in 2024 aligns more closely with the historical average recorded over the past 90 years. Jones explained, “For every magnitude seven, you have 10 magnitude sixes, 100 magnitude fives, 1,000 magnitude fours, etc. So, if your rate of magnitudes fours goes up, your chance of having a bigger one would go up by about the same amount.”
The sudden flurry of quakes follows a period of decades in which Southern California experienced fewer than average large quakes.
Researchers at San Diego State University and the Scripps Institution of Oceanography noted that the San Andreas Fault has a history of unleashing massive earthquakes roughly every 180 years. Currently, it has been about 300 years since the last significant quake, known as the ‘Big One,’ struck Southern California. Local officials are urging residents to use these recent quakes as a reminder to be prepared at all times.
County Supervisor Kathryn Barger said, “Having lived through the Northridge earthquake, today’s tremor made me flashback to what we know are life-saving rules during an earthquake: drop, cover, and hold on. It was also a reminder that we live in earthquake country and need to be prepared.”
- ABC7.”Recent earthquakes raise concern over lesser-known – but dangerous – Puente Hills fault”.
- Patch.”SoCals String Of Strong Quakes May Mean More Big Ones Are Likely”.
- FoxLA.”Earthquake strikes Southern California near Lake Elsinore”.