By Casey Frye, CCNN Writer
Ocean waves typically interfere with measurements from seismographs – instruments used to detect and record earthquakes. Now, however, researchers from Stanford University and MIT have found that ocean waves can be used to simulate ground motions that occur in real earthquakes.
As waves smack against coastlines, they send ripples of ground vibrations. While these signals are not a large as actual quakes, scientists can detect the tiny quivers over large distances. This is especially true of regions which lie over sedimentary basins – large areas of sunken crust filled broken down matter. Since these zones are softer than the rock that surrounds them, they amplify waves and create larger motions.
“If you try to extract that signal, you get something that looks pretty much like an earthquake, which we call the ‘virtual earthquake,’” says German Prieto, an assistant professor of geophysics in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We’re looking at… how the amplitude of that signal changes with position. A similar effect will happen for a future earthquake.”
The scientists used this virtual earthquake method to confirm that LA will experience a major earthquake over the San Andreas Fault – an 810-mile-long fracture in the Earth’s crust running through the state of California. “The seismic waves are essentially guided into the sedimentary basin that underlies Los Angeles,” said study leader Greg Beroza, a geophysics professor at Stanford. “Once there, the waves reverberate and are amplified, causing stronger shaking than would otherwise occur.”
Since the method is inexpensive, researchers say it can be used to detect potential earthquakes in developing nations.
Featured image courtesy of Ikluft on Wikipedia. Image of virtual earthquake courtesy of Stanford University on YouTube.