Map of expected levels of shaking from future earthquakes based on anticipated earthquakes and general geology. Bands of highest expected shaking generally follow the active faults; shaking levels are also influenced by the type of materials underlying an area - soft sediment, like that around the Bay margin, tends to amplify and prolong shaking. Note that much of the Bay region has the potential to be shaken very strongly during future earthquakes. Figure modified from U.S. Geological Survey, General Information Product 15, 2005 and, in turn, from http://www.consrv.ca.gov/cgs/rghm/psha/index.htm .