All the results that I will show in this paper are for a simple two layer
model. The bottom half space is isotropic and of very low density so that
there is a very high reflectivity for most angles. The surface layer is
highly anisotropic. It has orthorhombic symmetry with a horizontal plane
of symmetry. The medium is expected to exhibit triplication in the propagation
of shear waves. Most of the examples are for the response to a horizontal
traction applied along the vertical symmetry plane. In figure
I show the domain response for a run with no multiples and no
direct arrivals. The domain response is found by taking the
inverse fourier transform of the domain data that I have
calculated. The plot shows the x-component of displacement.
The uppermost event is the P-P wave reflection. The second
event is the P-S and S-P reflections. The third event which exhibits a
downwards concavity in the wavefront is the S-S wave reflection. The
range of *p* values used did not extend far enough to observe all of the
propagating S-waves.
Figure shows the same model but in this case the direct arrivals have
been calculated. Figure shows the same model with the first order
multiples calculated. The P-P-P multiple is almost hidden behind the S-S
arrival. The final event is the S-S-S-S arrival, in between there are
multiples with mixed wavetypes, P-P-P-S, P-P-S-S, and P-P-P-S. This figure
is already somewhat confusing. One advantage of the phase shift method is that
I can easily ``turn off'' some of these events to obtain a clearer picture.

Figure 7

Figure 8

Figure 9

12/18/1997