EST IMATED GROUND MOTIONS IN LOS ANGELES DUE TO M W = 7 EARTHQUAKE ON THE ELYS IAN THRUST FAULT

The Elysian thrust fault has been identified as a blind thrust fault (Davis et al., 1989; Hauksson and Jones, 1989) representing a potentially serious seis-mic hazard to the metropolitan Los Angeles and its neighboring areas. We have simulated time histories, peak ground accelerations and their uncertain-ties using a semi-empirical method for a M w = 7.0 earthquake on the Elysian thrust fault using a flat-layered crustal structure. The accelerograms from the 4 October 1987 Whittier-Narrows aftershock (10h:50m; M L = 5.3) are used to represent the source functions of each subfault on the fault surface. To account for the velocity variation in the surface sediments, we compared simulated ground motions using two separate shearwave velocities, 0.6 km/ sec and 0.9 km/sec, respectively, in the top layer of the crustal model. The use of such a simple crustal model is validated by modeling the accelero-grams recorded during the 1 October 1987 Whittier-Narrows mainshock (M L = 6.0). The duration and the relative frequency content observed on thes