California faces threat of back-to-back mega-quakes
The mega-quakes in Turkey this week showcase how a magnitude 7.8 quake could trigger a magnitude 7.5 aftershock on a different fault, with 60 miles of distance between the epicenters. A similar seismic scenario could occur in California. … In a U.S. Geological Survey report published in 2008 detailing a hypothetical magnitude 7.8 earthquake in Southern California, scientists said a plausible aftershock scenario included a magnitude 6.95 quake that would shake Sacramento and Modesto three days after the mainshock, endangering the stability of the levees, which are crucial for maintaining flood control and water movement from the northern Sierra Nevada to cities across the state.