Abstract

Site amplification factors at frequencies of 1.5, 3, 6, and 12 Hz were determined for 158 stations of the Southern California Seismic Network (SCSN) from coda waves of 306 local earthquakes using a recursive stochastic inverse method. Our results for southern California are consistent with those of central California obtained by Su et al. (1992), in that the site amplification at a station is systematically related to the surface geology of the station site. The site amplification is high for young, Quaternary sediments and decreases with increasing geologic age at all frequencies between 1.5 and 12 Hz. This decreasing rate is higher for younger rock sites, gradually becomes lower with increasing geologic age, and appears to be insignificant when the site reaches Mesozoic age or older. The relationship between site amplification and geologic age obtained for southern California agrees with that for central California. Amplification factors at 158 sites in southern California were combined with those at 132 sites in central California through a common reference site. The result is a unique data base of site-specific uniformly referenced amplification factors throughout central and southern California.

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