Homework 1

Computational part

In this part, we will simulate and observe acoustic wave propagation in a simple velocity model shown in Figure 1(a). A wave snapshot is shown in Figure 1(b).

model,snap
Figure 1. (a) Velocity model for simple wave propagation experiments. (b) Wave snapshot with overlaid first-arrival wavefront.

1. Change directory to geo384w/hw1/simple
2. Run

   scons model.view
   

   to generate and view the velocity model from Figure 1(a).
3. Run

   scons wave.vpl
   

   to generate and observe a propagating wave on your screen.
4. Run

   scons fronts.vpl
   

   to generate and observe a propagating wavefront on your screen.
5. Run

   scons snap.view
   

   to generate and view a wave snapshot selected at 1 s as shown in Figure 1(b).
6. Open the file SConstruct in your favorite editor. Your task is to make the following modifications in it:
   • Find a parameter responsible for selecting the time frame for the snapshot in Figure 1(b). Modify it to increase the time from 1 s to your favorite point in the movie. Run scons snap.view again to verify your change.
   • Can you observe a geometrical part of the wave that is not captured by the wavefront? What is its physical meaning?
   • Find a parameter in the SConstruct file responsible for the vertical smoothness of the model in Figure 1(a). Modify it to increase the smoothness of the model in such a way that the first-arrival wavefront follows the wave geometry exactly. Run scons snap.view again to verify your change.
   • (EXTRA CREDIT) For extra credit, modify SConstruct to generate a movie of pictures like Figure 1(b) for a gradually increasing smoothness.
7. When you are satisfied with your results, run

   scons lock
   

   to lock the figures.

Homework 1