UCLA

Site response effects are described by ergodic ground motion models, which are developed using global data from sites with diverse site conditions, using the time-averaged shear-wave velocity in the upper 30 m (VS30) and isosurface depths (z1.0 or z2.5). Site responses in sedimentary basins may have specific dependencies on the geometry and extent of the sedimentary structure in addition to VS30 and isosurface depths. We investigate here the effects of basin-to-basin categorization on site response. Using southern California data, we highlight differences in mean site amplification for eight large sedimentary basins with different geologic origins. The mean response in all basins shows significant relative amplification at long periods (T > 0.5 sec) and none at shorter periods (T < 0.3 sec). Comparisons of basin-specific responses reveal that coastal basins exhibit greater levels of relative long-period amplification than inland, fault-bounded sedimentary basins.