This is an example of a 2-dimensional numerical acoustic 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.

enlarged animation (~ 2.8 MB)

Model parameters

nx	180
nz	60
delta_x	10 m
delta_z	10 m
delta_t	40 ms
t_max	1.5 s
f_max	50 Hz
vp_1	1000 m/s
vp_2	2000 m/s

The subsurface model has a free surface at the top where strong reflections are generated. Also at the interface waves are partly reflected and partly transmitted into the lower layer. 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.