STOCHASTIC AND FULL-WAVEFIELD FINITE-FAULT GROUND-MOTION SIMULATIONS OF THE M7.1, MESSINA 1908 EARTHQUAKE (Southern Italy)

Abstract

In the framework of an ongoing Italian national research project we are studying the Messina 1908 earthquake, the first to be recorded adequately by seismological and geodetic instrumentation that allowed subsequent quantitative investigations of its source properties. We use a high-frequency stochastic finite-fault modeling (Motazedian and Atkinson, 2005) to simulate the ground-shaking for a number of different source models (Basili et al. 2008), either constrained from past source studies of this event or simulated. Although inherently kinematic, our approach accounts for the physics of the source using a procedure to generate physically consistent earthquake-rupture models (Guatteri et al., 2004). Considering the width of the seismogenic zone and appropriate source-scaling relation, we generate heterogeneous slip models that obey to the source complexity of past earthquakes (Mai and Beroza, 2002). By also constraining the point of rupture initiation based on empirical findings and energy-balance arguments (Mai et al., 2005), we generate a suite of earthquake source models to compute far-field ground-shaking. The Housner parameter from the stochastic high-frequency simulations is than compared with the felt intensity (MCS scale). The developed procedure is a necessary tool to take into account the influence of directivity effects in simulating ground shaking scenarios using realistic slip distribution on the fault. Furthermore, we carry out full-wavefield ground-motion calculations (at frequencies f < 3 Hz) to compare those low-frequency simulations with (a) the stochastic simulations and (b) appropriate ground-motion prediction equations. The combined approach helps to examine the validation range of the two methods (distinguishing the influence of the near-field and far-field motions on the shaking level), and may serve as a basis to develop a hybrid technique which combines the two methods for generating fully broadband synthetic seismograms.