It's a little too quiet in California, seismically speaking. The state is experiencing a century-long lull in large, ground-rupturing earthquakes, temblors that actually offset the earth at the surface. The 7.9-magnitude Great San Francisco Earthquake of 1906 was a ground-rupturing quake; photographs taken in its aftermath show roads and fences with new bends and twists. Now, new research finds that this 100-year earthquake gap is very unlikely to be a statistical fluke. Instead, something geological is probably causing the peaceful period. "We're unusually quiet," said study co-author Glenn Biasi, a geophysicist at the U.S. Geological Survey (USGS) in Pasadena, California. "The biggest faults and the faults carrying most of the slip have not ponied up."