A University of California, Berkeley, seismologist has discovered a way to provide seconds to tens of seconds of advance warning about impending ground shaking from an earthquake.

While a few seconds may not sound like much, it is enough time for school children to dive under their desks, gas and electric companies to shut down or isolate their systems, phone companies to reroute traffic, airports to halt takeoffs and landings, and emergency providers to pinpoint probable trouble areas. Such actions can save lives and money.

An early warning system like this is possible thanks to the work of Richard Allen, UC Berkeley assistant professor of earth and planetary science, who in the last five years has demonstrated that within a few seconds of an earthquake rupture, he can predict the total magnitude of the quake and its destructive potential.

In San Francisco, for example, Allen estimates that it's likely the city could receive 20 seconds' warning of an impending temblor.

"We can determine the magnitude within a couple of seconds of initiation of rupture and predict the ground motion from seconds to tens of seconds before it's felt," Allen said. He and his colleagues are now testing a system, ElarmS, that would make these predictions, and the researchers are working with the U.S. Geological Survey (USGS) to determine how accurate these warnings would be.