USGS geologist Kate Scharer led a team that investigated the timing of sand, mud and gravel deposits that were episodically ripped apart by earthquakes along the San Andreas Fault over the last 1,200 years. They found evidence of 10 ground-rupturing earthquakes between 800 A.D. and the last rupture in 1857. “In the area of the Grapevine we had a 100-mile or so stretch where we didn’t have good information on the timing of earthquakes back for the last thousand years or so,” Scharer said.