MAJOR CALIFORNIA EARTHQUAKES ------------------------------------------------------------------------- Current Annual Likelihood Probability of of Occurrence Richter Occurrence in Next Region Fault System Magnitude[1] (Percent) 20-30 Years ------------------------------------------------------------------------- Los Angeles- Southern San Bernardino San Andreas 8.3 2-5 High San Francisco Northern Bay Area San Andreas 8.3 1 Moderate San Francisco Bay Area Hayward 7.4 1 Moderate Los Angeles Newport- Moderate Inglewood 7.5 0.1 -Low San Diego Rose Canyon 7.0 0.01 Low Riverside Moderate- San Bernardino Cucamonga 6.8 0.1 Low Los Angeles Santa Monica 6.7 0.01 Low ------------------------------------------------------------------------- [1] This is the estimated largest magnitude earthquake expected at a reasonable level of probability. The main shock can be expected to be followed by large aftershocks over a period of weeks or longer. Each large aftershock would be capable of producing additional significant damage and hampering disaster assistance operations. ------------------------------------------------------------------------- These earthquake scenarios represent the largest magnitude events estimated on the basis of a variety of geologic assumptions. The appropriateness of these assumptions depends on the intent of the analysis and the state of geologic knowledge. Therefore, the resulting estimates may not be appropriate for other purposes, such as the development of seismic design criteria for a specific site. The development of such criteria commonly requires detailed analyses of the site and its immediate geologic environment beyond the scope of this report. Consequently, detailed site analyses may require modification of the conclusions reached in this report, particularly fault systems other than the San Andreas and Hayward faults. B. GEOLOGIC EVIDENCE