Every year approximately 500 earthquakes occur in the state of California that are large enough to be felt. San Diego County, in comparison to other southern California areas, has sparse seismicity. However, since 1984, earthquake activity in San Diego County has doubled over that of the preceding 50 years.
Ongoing field and laboratory studies suggest the largest credible earthquake predicted for the coastal and metropolitan areas is a M7.2 on the Rose Canyon Fault and a M7.6 from either the Elsinore Fault or the San Jacinto Fault in the north and east county areas. In addition, studies suggest the following maximum likely magnitudes for local faults: La Nacion (M6.2 to 6.6), Coronado Bank (M6.0 to 7.7), San Diego Trough (M6.1 to 7.7), San Clemente (M6.6 to 7.7).
It should also be noted that some faults are hidden beneath unperturbed sediments (blind fault) and only discovered after an earthquake occurs.