This is an example of a 2-dimensional numerical elastic simulation. The table shows the modelling parameters. The animation shows the seismogram section (bottom) and a series of snapshots (top) at times delta_t apart. The snapshots are displayed together with the step-like subsurface structure. The seismogram section grows with time according to the time of the displayed snapshot.

In the elastic case four different representations for the modelling results are given. From left to right pressure, shear, horizontal and vertical displacement amplitude are given.

enlarged animation (~ 2.3 MB)

Model parameters

nx	225
nz	125
delta_x	10 m
delta_z	10 m
delta_t	40 ms
t_max	0.96 s
f_max	50 Hz
vp_1	2000 m/s
vs_1	1155 m/s
rho_1	2000 kg/m^3
vp_2	4000 m/s
vs_2	2310 m/s
rho_2	3000 kg/m^3

The source is of explosive type with a Gaussian spatial distribution which only generates P-waves. At the interface waves are partly reflected and partly transmitted into the lower layer. At this interface mode conversion from P- to S-waves take place. Note the diffracted energy from the corners of the step in the snapshots. These diffractions can also be seen in the later part of the seismogram.  The event at the far right side at late times is due to a headwave.

Reference:
Kosloff, D., Filho, A.Q., Tessmer, E., Behle, A., 1989,
Numerical Solution of the Acoustic and Elastic Wave Equations by a New Rapid Expansion Method,
Geophys. Prospecting, Vol. 37, 383 - 394.