MODELLING OF SEISMIC WAVES IN HETEROGENEOUS MEDIA USING A WAVELET-BASED METHOD: APPLICATION TO FAULT AND SUBDUCTION ZONES

Abstract

The wavelet approach to numerical simulation of elastic wave propagation is applied to models with localized heterogeneity, with significant contrasts with their surroundings. We consider zones with both lowered wave speed such as a fault gouge zone and elevated wave speeds such as in a subduction zone. In each of these situations the source lies within the heterogeneity. The representation of the source region has therefore been adapted to work directly in a heterogeneous environment, rather than using a locally homogeneous zone around the source. This extension also allows the wavelet method to be used with a wider variety of sources, e.g. propagating sources. For the fault zone we consider both point and propagating sources through a moment tensor representation and reveal significant trapped waves along the gouge zone as well as permanent displacements. For subduction zones a variety of effects are produced depending on the depth and position of the source relative to the subducting slab. A variety of secondary waves, such as reflected and interface waves, can be produced on wave trains at regional distances and tend to be more important for greater source depths.