Possible Earthquake Warning Discovery

There's not much detail to go on, but scientists have identified small seismic waves that occurred 10 hours before a magnitude 3 quake near Parkfield, California. They believe they may be able to use waves like these as part of an early warning system that would allow evacuation of vulnerable areas before a quake.

A little more helpful info is in this article.

More info on Paul Silver, one of the scientists involved in the research. The linked article uses the word "birefringence" which I think we should all use in a sentence today...or this weekend, at least.

BIREFRINGENCE - Property of a mineral if a ray of light passing through it experiences two refractive indices. The effect is to change the polarization state of the transmitted light. The extent of the change depends on the material and the thickness of the specimen. Birefringence can be induced in some materials by the presence of an applied or residual stress.