- Simulation of a magnitude-7 quake on the San Andreas Fault. Seismic waves radiate outward, then deep into L.A.
A seismology study by scientists from Stanford and MIT, published in the journal Science on Friday, finds that if the Big One hits the San Andreas Fault near Palm Springs, some seismic waves will travel near the path of the 10 Freeway into the heart of Los Angeles, where the city and its suburbs will suffer stronger ground motions than previously believed. Downtown L.A. will endure three times the shaking of surrounding areas, scientists now say.
The study shows that a “funneling action” of seismic waves will roll straight into the Los Angeles Basin through a 60-mile-long corridor, striking a 13-million population region that stretches from the Santa Monica Mountains to Newport Bay and inland to the basins of the San Gabriel and Santa Ana rivers. The study confirms a 2006 supercomputer simulation that predicted L.A. could endure worse shaking than long feared. Greg Beroza, a professor at School of Earth Sciences of Stanford University who led the study, explains (See VIDEO below):
The study used “virtual earthquakes” to predict ground motion. Scientists used data taken of weak vibrations beneath the ground – which are actually generated by the movement of ocean waves and then transmitted into the earth – to construct a major, fake earthquake, according to Denolle.
“Those waves [are] transferred to the sea bottom. These get transmitted to the crust where we actually have instruments recording,” says Denolle.Weak ground vibrations, known as “the ambient seismic field” in geology, are present all the time, but they’re so mild that they’re unnoticeable. Scientists have known about the ambient seismic field for more than 100 years, but viewed them as interference in their efforts to study earthquakes. Now, with this study, scientists made use of them – as proxies for strong seismic waves created by a big earthquake.
Full article: ‘The Big One’ Earthquake Will Hit L.A. Harder Than We Thought, Scientists Say (LA Weekly)