It is not flat because of the slight decrease of shear-wave velocity near the surface. In performing the computations, four ground motion models are compared. Uses only the 1996 USGS source and distance model, but propagates these through the deep soil model described above. The same deep soil model is used. The same deep soil model is used.
Site effects are minimal.
The major difference with respect to the USGS model is in the shape of the source spectrum for large earthquakes. This model has an intermediate trend. The following pages compare the plots of the four ground motion models. The Peak Acceleration plots will focus on the high frequency component of the expected ground motion, while the 1.0 Sec Pseudo Acceleration focuses on a lower frequency. The striking feature is the boomerang shaped high expected ground motions in the northern part of the embayment, at some distance from current microseismicity.