Abstract

Near-field displacement, velocity and acceleration ground motion are computed for a buried finite strike-slip fault using generalized multipolar ray theory to study the effects of rupture velocity, rise time of particle displacement, direction of rupture relative to observing station and the presence of the free surface. Computed displacement seismograms demonstrate that the rise time and rupture velocity can be traded off to produce similar wave shapes emphasizing the difficulty of separating the effects of rise time and rupture velocity. On the other hand, synthetic accelerograms exhibit much character as the rise time becomes a small part of the rupture duration, and individual contributions to the acceleration signals such as the P- and S-wave stopping phase can be seen. Near-field synthetic accelerograms hold promise for the study of fault rupture parameters. For the strike-slip model studied, allowance for the presence of a free surface by doubling of the amplitude of infinite space signals seems to be approximately correct even in the case of computed vertical component accelerograms. However, this result is not generally true for the residual static displacements. The known result of the appearance of Rayleigh waves at horizontal distances greater than five times the source depth is confirmed for dislocation sources.

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