Using remarkably sensitive new instruments, seismologists have detected minute geological changes that preceded small earthquakes along California's famed San Andreas Fault by as much as 10 hours.

To the surprise of many, the earthquake on April 18, 2008, about 120 miles east of St. Louis, originated in the Wabash Valley Fault and not the better-known and more-dreaded New Madrid Fault in Missouri's bootheel.

Like geological ninjas, earthquakes can strike without warning. But there may be a way to detect the footfalls of large earthquakes before they strike, alerting their potential victims a week or more in advance. A Stanford professor thinks a method to provide just such warnings may have been buried in the scientific literature for over 40 years.