From CNN:
…researchers from the University of California, Berkeley, say the measurements of seismic waves soon after a temblor can signal whether it will be a minor or monster temblor.
They say the information could possibly be used in an alert system to give seconds to tens of seconds of advance notice of an impending quake — enough time for schoolchildren to take cover, power generators to trip off and valves to shut on pipelines.
“We’re not taking about a massive amount of time,” said Richard Allen, an assistant professor of earth and planetary science, who led the study.
More here.