Bay Geophyical of Traverse City, Michigan, used @2D to find voids and merging utilities along a buried concrete pipeline. The only data input used to produce the velocity model was the first arrival shear wave travel-time data, and array geometry. No other a priori data were used. This is a velocity model from one of the lines. Notice the detail at which near-surface velocities were modeled. In fact, the petroleum industry uses our software for near-surface velocity static corrections because of the detail in which near-surface velocities are revealed. The pipeline runs parallel to the seismic array. The poured concrete pipeline bed is shown correctly at about 15 feet depth (elevation of 11 feet). The soil above the pipeline shows a gradient as a result of burial pressure. A utility tunnel intersecting the pipeline was imaged at about offset 290 feet, centered at about 10 feet depth (elevation of about 16 feet). The velocity model also picked up some subtle lateral velocity features in the soil associated with the construction and burial of the tunnel. There is also a localized slight velocity reversal, indicating a void, at about offset 370 feet, elevation about 6 feet.
There was no need to guess if the target area was properly sampled during the interpretation. SeisOpt® @2D provides a hit count plot of ray coverage in the subsurface. If an area is not sampled, SeisOpt® truncates it so you don’t try and make an interpretation of potential artifacts. As you can see, there was dense ray coverage of the entire velocity model, indicating a high degree of confidence in the interpretation.
