PROSPECTS FOR LARGER OR MORE FREQUENT EARTHQUAKES IN THE LOS-ANGELES METROPOLITAN REGION

Far too few moderate earthquakes have occurred within the Los Angeles, California, metropolitan region during the 200-year-long historic per iod to account for observed strain accumulation, indicating that the h istoric era represents either a lull between dusters of moderate earth quakes or part of a centuries-long interseismic period between much la rger (moment magnitude, M(W), 7.2 to 7.6) events. Geologic slip rates and relations between moment magnitude, average coseismic slip, and ru pture area show that either of these hypotheses is possible, but that the latter is the more plausible of the two. The average time between M(W) 7.2 to 7.6 earthquakes from a combination of six fault systems wi thin the metropolitan area was estimated to be about 140 years.