RTM using effective boundary saving: A staggered grid GPU implementation

Exact reconstruction

To make sure that the proposed effective boundary saving strategy does not introduce any kind of error/artifacts for the source wavefield, the first example is designed using a constant velocity model: velocity=2000 m/s, $nz=nx=320$ , $\Delta z=\Delta x=5m$ . The source position is set at the center of the model. The modeling process is performed $nt=1000$ time samples. We record the modeled wavefield snap at $k=420$ and $k=500$ , as shown in the top panels of Figure 6. The backward propagation starts from $k=1000$ and ends up with $k=1$ . In the backward steps, the reconstructed wavefield at $k=500$ and $k=420$ are also recorded, shown in the bottom panels of Figure 6. We also plot the wavefield in the boundary zone in both two panels. Note that the correctness of the wavefield in the original model zone is guaranteed while the wavefield in the boundary zone does not need to be correct.

fig6
Figure 6. The wavefield snaps with a constant velocity model: velocity=2000 m/s, $nz=nx=320$ , $\Delta z=\Delta x=5m$ , source at the center. The forward modeling is conducted with $nt=1000$ time samples. (a-b) Modeled wavefield snaps at $k=420$ and $k=500$ . The backward propagation starts from $k=1000$ and ends at $k=1$ . (c-d) Reconstructed wavefield snaps at $k=500$ and $k=420$ . Note the correctness of the wavefield in the original model zone is guaranteed while the wavefield in the boundary zone may be incorrect (32 layers of the boundary on each side are also shown in the figure).

RTM using effective boundary saving: A staggered grid GPU implementation