An aerial view of the Palos Verdes Peninsula. (Allen J. Schaben / Los Angeles Times)
A fault system running nearly 70 miles along the coast of Los Angeles and Orange counties has the potential to trigger a magnitude 7.8 earthquake, according to a new study that is the latest to highlight the seismic threats facing Southern California.
Known as the Palos Verdes fault zone, the system runs deep beneath the Palos Verdes Peninsula. It previously was thought to be a segmented network of smaller faults, but a closer look by scientists at Harvard University suggests it’s a system of interconnected, closely spaced planar fractures stretching from the Santa Monica Bay to the waters off Dana Point.
The analysis determined the fault system, which runs beneath numerous neighborhoods as well as the ports of Long Beach and L.A., has a much larger surface area that could rupture in the same seismic event, making it capable of a far more powerful quake than was previously known.
Scientists found the fault could produce a quake of a magnitude comparable to one from the San Andreas fault. Earlier estimates said the fault zone could generate up to a magnitude 7.4 earthquake, but the new study shows it could produce a quake as strong as 7.8.
The difference may be only a few decimal points, but an earthquake’s energy is measured exponentially. According to the U.S. Geological Survey, a magnitude 7.8 quake produces quadruple the energy of a magnitude 7.4.