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Figure 5 shows a super-gather, consisting of all the
traces in the survey binned as a function of offset. The left panel
shows the raw data, and the center panel shows the same data after
pre-processing.
sgather
Figure 5 Super-gather: entire dataset stacked into
offset bins. Left panel shows raw data, center panel show processed
data after pre-processing, and right panel shows semblance scan
We processed the data with our in-house software, SEPlib3D,
which provides a flexible environment for research in 3-D seismology.
The simple processing flow consisted of:
- 1.
- Trace edits
- 2.
- Groundroll removal:
A low-cut filter was sufficient to remove the groundroll.
See Figure 6 for its impulse response and spectrum.
- 3.
- Top mute to remove the refracted arrivals.
- 4.
- Time-varying gain correction: tpow=2.
- 5.
- NMO and stack:
The right panel of Figure 5 shows a semblance scan
from the super-gather. The velocity information provided by the 3-D
dataset was limited by the small maximum offset. However, the small
maximum offset also means the dataset is not very sensitive to
move-out velocity. In any case, NMO was
applied with a constant velocity of 240 m/s, the RMS velocity of the
water-table reflector, which had been more accurately estimated from
the larger offset 2-D surveys.
impulse
Figure 6 Impulse response of low-cut filter.
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Next: Results and conclusions
Up: Rickett & Bachrach: High-resolution
Previous: Geometry
Stanford Exploration Project
7/5/1998