A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...

Five degrees separated each line with the long line separated by ten degrees, and the short
lines with a ten degrees separation. Lines were closely spaced near the dome and spread
apart as they radiated away from the dome. Receiver station spacing was 165 feet (50m)
along each line segment. At each station was a six-element array using 10-Hz
geophones. Source locations approximated concentric circles and had a shot spacing of
165 feet (50m) along the arc. Most disruptions in the shot pattern were due to cultural
obstacles located in the north and west portions of the survey (Constance et al., 1999).
Obstacles included power lines, roads, and Interstate Highway 10 cutting across the
northern portion of the survey (Figure 32).
A 90º sector of the 360º coverage was active for each shot with 19 active receiver lines
per shot, which was between 1400 and 2000 active channels. For each active 90º receiver
sector the center rack of source locations, forming an arc through the receiver lines, was
detonated and recorded. Since the entire receiver line was active, there was no radial roll.
After each shot the active receiver spread was advanced 10º or two receiver lines and the
next sequence of shots were recorded (Constance et al., 1999).
Innovative acquisition such as this has several benefits both recognized and many likely
not realized. One aspect is the fold (Figure 33). Higher fold close to the dome was to
enhance illumination of steeply dipping beds and illuminate areas of complex structure.
Another intention of this acquisition design was to keep raypaths from passing through
the salt so that depth imaging would not be necessary (Constance et al., 1999).
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