The USGS is releasing a new tool to help mitigate loss of life and property - a 3D computer model of the upper 20 miles of the Earth's crust in the greater San Francisco Bay Area that will enable researchers to accurately predict the shaking levels of past and future earthquakes. Previous work by the USGS and others has shown that the 3D structure of the Earth has a significant impact on how strongly an earthquake is felt at different locations and on the duration of the shaking. Because seismic waves propagate through different rock types with differing speeds that...