Source complexity effects on ground shaking scenarios

Hazard analysis requires the parameterization of the seismic sources that can be expected to affect a selected place in terms of locations, magnitudes, focal mechanism and, for event with a significant magnitude, the dimension of the fault and the distribution of the slip on the fault surface. We use a kinematic approach to compute ground shaking scenarios, through the modelling of the source geometry and of the seismic moment distribution on the fault surface. We investigate three events: the Mw 5.2 Bovec (Slovenia) July 2004 one and the two Mw 6.5 Iceland June 2000 ones. We present the results in terms of contour map of the maximum horizontal ground acceleration extracted from the synthetics calculated on a grid of receivers equally spaced around the fault area. To reproduce the surface fault complexity we considered: a) a uniform seismic moment distribution; b) a seismic moment distribution with a single asperity located in the central part of the fault surface; c) a seismic moment distribution with two asperities and d) in one case the seismic moment distribution obtained from the inversion of strong ground motion data. Our results confirm that the slip distribution, and in particular the position of the asperities on the fault plane, plays a non-negligible role in seismic hazard assessment. If, in the future a variety of more or less characteristic slip distributions for a given set of faults in an active tectonic area can be assessed, the possible source-related variability of expected ground motion shaking in the region could be easily estimated.