A fault zone off the Santa Monica coast could result in a larger, higher magnitude earthquake than previously thought according to a new study.
Instead of a 7.4 magnitude earthquake, which is already considered severe, scientists now say the fault system is capable of triggering up to a 7.8 quake. While the difference may not seem major, it is an increase of close to four times the amount of energy being released, according to calculations by the United States Geological Survey.
Dubbed the Palos Verde fault zone (PVFZ), the network runs close to 70 miles from the Santa Monica Bay, south down the coast, under the Palos Verdes peninsula and out into the ocean off of Dana Point.
Scientists say this new knowledge reveals the potential for an earthquake more destructive than both the 2019 Ridgecrest quake and the 1994 Northridge earthquake, which caused significant damage in Santa Monica.
The study, conducted by a group of three Harvard earth and planetary scientists, compiled data from a variety of sources to piece together a model of the fault zone in far more detail than had been done before. They discovered a system of interconnected fractures, rather than the string of separate, smaller fragments previously thought to make up the fault zone.
“The sizes of these segments indicate that PVFZ is capable of larger events than previously reported,” the study says. Adding, “the Santa Monica Bay segment and RCFZ (Redondo Canyon Fault Zone) should be considered as active seismic sources capable of moderate‐to‐large magnitude earthquake events that would directly impact the metropolitan Los Angeles area.”
The study also suggests that the Palos Verdes fault has a faster slip rate than other active fault zones in LA county, meaning that more energy is being generated and stored to eventually be released in the form of an earthquake. Such an earthquake would cause mass damage and destruction and could also result in tsunamis in the Santa Monica area.
“Given the offshore extent of the fault, it might be capable of generating local tsunamis in the San Pedro and Santa Monica Bay, as well as in the Los Angeles and Long Beach Harbors,” the study says.
The PVFZ appears to be less active than other fault zones including the San Andreas fault which ruptures every couple hundred years. The PVFZ has a recurrence interval of 580-610 years for single segment ruptures and 760-1110 years for the type of multisegment ruptures that could produce a 7.8 quake.
While this makes it unlikely for a major earthquake caused by the PVFZ to occur anytime soon, the new study serves as a reminder to individuals and governments to take steps to be prepared in the event that an earthquake does occur.
The report is available online at https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/112/5/2689/615140/Origin-of-the-Palos-Verdes-Restraining-Bend-and
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