CSMIP 95-03

"Site Response Studies for Purpose of Revising NEHRP Seismic Provisions"

by C.B. Crouse

March 1995, 68 pp.

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A strong-motion database was compiled for California earthquakes of surface-wave magnitudes, Ms ≥ 6, occurring from 1933 through 1992. The database consisted of horizontal peak ground acceleration and 5 percent damped response spectra of accelerograms recorded on four different local geologies: bedrock (class A), soft rock or stiff soil (class B), medium stiff soil (class C), and soft soil (class D). The results of regression analyses of the database within each of these site classes were used to derive a set of site-dependent spectral amplification factors for oscillator periods between 0.1 and 4.0 sec and ground acceleration levels between 0.1 and 0.4 g. The amplification factors at 0.3 and 1.0 sec periods are generally similar to those recommended during the 1992 NCEER Site Response Workshop.