9503991 Bielak This proposal is concerned with the development of efficient parallel algorithms for the numerical study of wave phenomena that arise when waves propagating within an infinite or semi-infinite medium encounter obstacles in their path. The focus of this proposal is to successfully integrate absorbing boundary techniques, which primarily aim at the reduction of computational domains, with parallel numerical algorithms that exploit distributed memory multiprocessor systems. The ultimate objective is the physical understanding of the modeled system: in this proposal the primary application target is the elastic wave propagation arising in the simulation of the ground motion of large basins.