Warning signs detected hours ahead of big earthquakes

Established earthquake warning systems provide at best just a minute or two of notice —and that’s only if the shaking doesn’t start under your feet. Decades of searching for a better warning sign—fluctuations in the geochemistry of groundwater , electromagnetic effects in the upper atmosphere, and even changes in animal behavior—have failed. Many question whether such a precursor signal even exists. Now, researchers say they have identified nearly imperceptible shifts along fault zones up to 2 hours before large earthquakes, according to a report today in Science . Although existing monitoring systems cannot yet pick up this signal in real time, the discovery points toward a future where residents could retreat to safe havens ahead of the most catastrophic quakes. “It’s just tantalizing,” says Richard Allen, a seismologist at the University of California, Berkeley, who was not involved in the work. “The whole idea of being able to predict the onset of [an] earthquake rupture is a really big deal.” Earthquakes occur when two blocks of Earth’s crust, locked together along a fault, build up stress until they slip in spectacular fashion. Researchers have long debated whether this rupture happens in a near instant or starts slowly, building up speed in a way that might be detected ahead of time. Signs of such precursor signals have been seen for individual quakes, but they have never yielded a signal t...
Source: ScienceNOW - Category: Science Source Type: news