Map of known active geologic faults in the San Francisco Bay region
Map of known active geologic faults in the San Francisco Bay region, California, including the Hayward Fault. The 72 percent probability of a magnitude (M) 6.7 or greater earthquake in the region includes well-known major plate-boundary faults, lesser-known faults, and unknown faults. The percentage shown within each colored circle is the probability that a M 6.7 or greater earthquake will occur somewhere on that fault system by the year 2043. The dark, thick lines outlined in various colors represent major plate boundary faults; the thinner, yellow lines mark lesser-know, smaller faults.