Numerical simulations were done by Tierra Geophysical, now part of Landmark Graphics Corporation. SEAM did not specify a specific approach to perform numerical simulations. Instead, SEAM developed quality requirements for the simulations and allowed vendors to meet those requirements using any numerical approach, whose specifics may remain unknown to SEAM. Hence, this chapter does not attempt to describe the specifics of the simulation computation. Rather, it focuses on
run parameters so that the data can be reproduced;
artifacts from postsimulation filtering to apply the SEAM far-field wavelet;
global amplitude scaling process;
use of ghost source and receivers so that absorbing upper surface data have the same wavelet as the free surface data;
the degree of variation in the data caused by factors such as a change to the simulation code, use of multiple compute clusters, and elimination of numerical problems that occurred on a very small percentage of the shots; and
problems that occurred, and how they were identified and corrected.
There are significant connections between this and Chapter 3 for topics of source wavelet, trace scaling, absorbing upper surface, and verification. Chapter 3 also covers vendor qualification procedure, requalification using the production model, and verification of production simulations.
The SEG-Y header definitions that were actually used are listed in Appendix A. The simulation specifications as actually implemented are listed in Appendix B. These evolved over time in response to knowledge gained and as more details were developed by the technical committees,