A series of animations are presented by which the propagation of seismic shear waves from  deep and shallow earthquakes are visualized. The wavefront movies are created by taking multiple time slices of synthetic seismograms across a grid of points throughout the mantle, from the surface to the core and from the focus to the antipode. The large number of synthetic seismograms are computed across two-dimensional grid using a summation of the Earth's torsional modes of oscillations. This yields a complete record of the SH wavefield.  For comparison, ray-tracing of the waves shown are also presented for a slice across a spherically symmetric mantle model. The associated time-distance curves for specific SH motion are visualized, to demonstrate the unique relation between a given ray path and its arrival time. The effect of the earthquake focal depth and station azimuth on the wave shape and amplitude is demonstrated. The movies show how the initially spherical SH wavefront becomes many different seismic phases fter its interaction with the Earth's major interfaces such as the surface, upper-mantle and core-mantle discontinuities. The movies are put into a Shockwave format, available for public use through Netscape.




For more detail see the paper :
Wysession M. E. and Shore P. J. (1994), Visualization of Whol Mantle Propagation of Seismic Shear Energy Using Normal Mode Summation, Pure and appl. geophys. vol. 142, pp.295-310.