There is a 25 percent chance of a strong and potentially damaging aftershock in the next seven days following Sunday’s 6.0-magnitude earthquake near American Canyon, U.S. Geological Survey officials said Monday.
The estimate comes a day after state geologists estimated the probability of strong aftershocks from the "South Napa earthquake" at more than 50 percent. The quake struck at 3:20 a.m. Sunday northwest of American Canyon about seven miles below the earth’s surface, USGS officials said.