Los Angeles Earthquake Will Be Bigger Than Expected: Scientists Predict Huge San Andreas Fault Quake Using Virtual Modelling [VIDEO]
Scientists based out of Stanford University are claiming that 'virtual earthquakes' produced by weak vibrations generated by the Earth's oceans can be used to predict the ground movement and the threats from real quakes to buildings. Perhaps more pressingly, based on their study, the researchers are warning that there will be a major quake south of Los Angeles, and that it will create stronger than expected ground movement. The research is published in the Jan. 24 issue of the journal Science
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The new prediction technique relies on seismic waves. Typically associated with earthquakes, seismic waves can be found in the ground even when there is no quake, according to study leader Greg Beroza, a geophysics professor at Stanford. The new technique is designed to use the ambient seismic field generated by ocean waves interacting with the Earth, which are "billions of times weaker than the seismic waves generated by earthquakes," Beroza said in a press release.
While scientists have known about the ambient seismic field for long, it was to this point mostly considered a nuisance as it interfered with their earthquake research. Seismologists have, however, developed techniques that allow them to isolate certain waves. Denolle used the same technique that uses weak ambient seismic waves to predict the actions of stronger waves generated by actual earthquakes, and installed seismometers along the San Andreas Fault to measure ambient seismic waves. The mathematical technique the scientists developed mimicked the waves that originate deep within the Earth.
The researchers used the approach to confirm an earthquake prediction made in 2006 using supercomputer simulations. According to this prediction, a rupture in the southern San Andreas Fault section of California could amplify along a 60-mile natural conduit connecting Los Angeles. The funneling action (also known as a waveguide-to-basin effect) could not be verified earlier because no major earthquake along the San Andreas Fault has occurred over the last 150 years. The virtual earthquake approach, however, solves this problem.
Los Angeles is a precarious city: it is built on top of a large sedimentary basin that is very susceptible to getting shaken up by earthquakes. If seismic waves were to reach the LA basin, the sediment would amplify their effect, and direct the waves right towards downtown. As a result, Los Angeles is sitting atop a huge risk, just in case a large earthquake of 7 or more magnitude was to hit along the southern San Andreas Fault, near the Salton Sea.
The virtual earthquake approach, according to Beroza and his team, can be used to analyze threats to other earthquake threatened cities like Seattle, Mexico City, Tokyo and several more. "All of these cities are earthquake threatened, and all of them have an extra threat because of the basin amplification effect," Beroza said.
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