Seismic radiation from tensile and shear point dislocations between similar and dissimilar solids

We examine the characteristics of seismic radiation produced by localized fault-opening and shear motions in a homogeneous solid, along with the effects of having dissimilar solids across the fault on the seismic radiation. The study employs calculations of synthetic seismograms generated at various receiver locations by shear and tensile dislocation sources. The results indicate that, in contrast to the standard case of shear dislocation, the body wave amplitudes of the fault-parallel component generated at near-fault seismograms by tensile dislocation are considerably larger than those of the fault-normal component. The P and S arrivals from a shear dislocation at receivers on the opposite sides of a fault in a homogeneous solid have the same polarities on the fault-normal component and opposite polarities on the fault-parallel and vertical components. However, for a tensile dislocation source the situation is exactly reversed. The existence of a velocity contrast across the fault produces additional phases that mask somewhat the above signals. However, the generated amplitudes and other waveform characteristics may be used to distinguish between the physical fault plane and the auxiliary plane. The recording and analysis of the discussed signals for regular earthquakes that are dominated by shear motion will require high-resolution receivers located very close to the fault.