IWAVE Structure and Basic Use Cases

Simulation

Recall that output files for IWAVE applications must exist prior to execution. Therefore, to simulate 12 shots at intervals of 400 m over the model depicted in Figure 1, the first step is to create a suitable SEGY data set to hold the output. Therefore the SConstruct script creates the output file of zero SEGY traces ( line8-12km.su), subsequently filled with samples by IWAVE, all as part of the same Flow command. As note above, the source must be properly embedded in a space-time field (collection of SEGY traces) for each shot location. The utility trace/main/towed_array.x provides a convenient method for combining the position data of a prototype SEGY trace file with a choice of source array to produce translations of a source array to correct shot positions. Other parameters are as in the single-shot case. The result is displayed in Figure 11.

line8-12km
Figure 11. Response of 13 seafloor pressure sensors spaced 400 m apart at 1.875 km depth, to 400 shots spaced 25 m apart at 6 m depth, sources are isotropic point radiators, source pulse is Gaussian derivative with peak frequency 5 Hz. Velocity-squared model depicted in Figure 1.

Perusal of the project/SConstruct script shows that in the invocation of acd.x, only the filenames have changed. The dataflow design of IWAVE, in which data objects determine the way in which they are read/written, implies that the information about changed source/receiver geometry and data volume does not need to be explicitly passed to the simulation command.

IWAVE Structure and Basic Use Cases