A specific barrier model for the quantitative description of inhomogeneous faulting and the prediction of strong ground motion; Part II, Applications of the model

The specific barrier model is applied to a set of five moderate to strong Californian earthquakes. Barrier intervals, local stress drops, cohesive zone size, and cohesive stress are inferred. The San Fernando earthquake of 1971 revealed a strong frequency dependence of Q (sub beta ) , suggesting that the high frequencies may not be as strongly attenuated as initially thought. Thus the fall-off at high frequencies of observed spectra may not be a propagation path effect but primarily a source effect. The cut-off frequency observed on the source acceleration power spectra is interpreted in terms of the cohesive zone size and cohesive stress which arrest the localized fractures on the fault plane. The barrier interval increases with the increase in maximum slip. Local strain drop was found to increase slightly (factor of 2) with earthquake size. This verifies the relation between barrier interval and maximum slip. Strikingly similar source parameters were found between the Fort Tejon (1857) and Kern County (1952) earthquakes and between the Long Beach (1933) and Parkfield (1966) earthquakes. The former have long barrier intervals and large slips while the latter have short barrier intervals and small slips. San Fernando (1971) and Borrego Mountain (1968) earthquakes lie between these two extremes.--Modified journal abstract.