We have applied the methodology outlined in the previous section to the modeling of earthquake-induced ground motion in the San Fernando Basin in Southern California. Specifically, the geographic region extending from -118.7500 to -118.1628 degrees longitude and -34.0828 to -34.3833 degrees latitude is modeled as a rectangular parallelepiped 54km long by 33km wide by 15km deep. The properties of the basin are described by the triplet of shear-wave velocity, dilatational-wave velocity, and density; for this application the material database has been obtained from the geology-based velocity model of Magistrale, McLaughlin, and Day . For the above geographic region, Fig. 2 shows the shear-wave velocity distribution at a depth of one meter from the surface of the valley. The figure shows a variation in shear-wave velocity of at least a factor of seven. This factor exceeds 20 when properties at depth are considered.
Click to take a close look (Same for figures below)
Figure 2: Near-surface distribution of shear-wave velocity in the San Fernando Valley; actual depth is 1m.