2024 sees Southern California’s highest M4+ earthquake count since 1988, return to long-term average
Featured image: Earthquakes in Southern California from August 8 - 15, 2024. Credit: TW/SAM, ESRI
Since 1932, Southern California has averaged 10 – 12 M4 earthquakes annually. However, in the last 20 years, this number dropped to around 5 per year. In 2024, with 13 M4s already recorded, the region is seeing a return to its long-term average.
Southern California is experiencing a significant increase in seismic activity this year, with two notable M4+ earthquakes occurring in the past week alone. A M4.4 earthquake struck near Highland Park on Monday, August 12, 2024, shaking areas across Los Angeles, Orange, and Riverside counties. This followed an M5.2 quake centered near Bakersfield, felt across the region less than a week prior.
2024 is on track to be one of the most active years for earthquakes in Southern California since 1988, according to Dr. Lucy Jones, a seismologist with the California Institute of Technology.
“2024 has had more [M4+] earthquakes than any year we’ve seen since 1988,” Jones said in an interview with KTLA 5 Morning News on August 13. According to Jones, Southern California has already experienced 13 earthquakes of magnitude 4.0 or greater this year, a sharp increase compared to the annual average of five such quakes over the past 20 years.
“Just remember that the last 20 years have been quiet and we should be expecting in the long run to see more than we have recently,” Jones said.
For clarity, the long-term average for M4 earthquakes in Southern California since 1932 is about 10 – 12 per year. The past 20 years in Southern California have seen a drop to about 5 per year, but 2024, with 13 M4s thus far, suggests a return to the historical norm.
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
According to the USGS, the recent M4.4 quake, which occurred at 12:20 local time (LT) on Monday, is believed to be associated with the Puente Hills thrust fault system. This earthquake appeared to be based on the same group of faults that produced the 1987 Whittier Narrows quake, according to Jones.
Jones pointed out that the quake occurred in roughly the same location as the M3.4 quake on June 2. “There have been others in the past,” she said. “In 1989, we had a pair of 4.5-magnitude quakes that were also in the system and just a half-hour apart.”
This surge in seismic activity could mean an increased potential for larger earthquakes in the future. The increased rate of smaller quakes could be a precursor to more significant seismic events, according to Jones.
“The most constant feature of earthquakes is the relative number of large to small,” Jones said. “So, if your rate of magnitude fours goes up, your chance of having a bigger one would go up by about the same amount.”
According to Jones, despite the rising frequency of earthquakes, California is better prepared than ever for a major seismic event. “So, this is an active year, much like we used to see,” she said. “It does seem like we should expect this to continue at a higher rate.”
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Adding to the concerns of the local population, local media today are reporting the discovery of an extremely rare deep-sea “doomsday fish” off the coast of Southern California.
“Last weekend, some lucky kayakers and snorkelers came across a rare deep-sea fish in La Jolla Cove. The seagoers spotted a 12-foot [3.6 m] oarfish, and to give you an idea of how rare this encounter is, only 20 oarfish have washed up in California since 1901,” said the Scripps Institution of Oceanography at UC San Diego.
These fish have earned their alarming nickname due to their reputation as harbingers of earthquakes or other bad events, according to the Ocean Conservancy. Reportedly, twenty such fish washed up on the shores of Japan just before the catastrophic 2011 earthquake. The California oarfish was indeed found just two days before the M4.4 earthquake struck the region and rattled Los Angeles, CBS reported.
The belief that oarfish can predict earthquakes is deeply rooted in Japanese folklore and has persisted for centuries.
In Japanese culture, oarfish are known as “Ryūgū no tsukai,” which translates to “messenger from the Sea God’s palace.” According to legend, these creatures are believed to be divine messengers sent from the undersea world, emerging from the deep ocean to warn of impending doom, particularly earthquakes and tsunamis. The rarity of oarfish sightings, combined with their mysterious and otherworldly appearance, has fueled the idea that their sudden appearance near the shore is a sign of a disturbance in the ocean’s depths.
The association between oarfish and earthquakes has been reinforced by several high-profile incidents.
For example, in the months leading up to the catastrophic 2011 Tōhoku earthquake and tsunami in Japan, there were multiple reports of oarfish washing ashore. These sightings were widely reported in Japanese media and led to speculation that they were warning signs of the disaster to come. This event strengthened the belief in the oarfish’s role as an omen.
Kiyoshi Wadatsumi, an ecological seismologist, has noted that deep-sea fish such as the oarfish may be more sensitive to movements near active faults, but this sensitivity does not equate to reliable earthquake prediction.
Further, a study published in the Bulletin of the Seismological Society of America by Joseph L. Kirschvink discusses animal behavior before earthquakes. While animals may detect certain seismic precursors, such as changes in magnetic or electric fields, the study concludes that these responses are not consistent or well-understood enough to form the basis of an early warning system.
References:
1 Seismologist warns of increasing earthquake activity in Southern California – KTLA 5 – August 13, 2024
2 Extremely rare “doomsday fish” found off Southern California coast – CBS – August 15, 2024
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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