Annual Report 2000 - WIT

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101
versa where the two integrals are asymptotically inverse operations to each other. The
transformation pair for the 2D case reads:
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Where denotes the so-called configuration parameter which includes shot- and
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receiver coordinates. stands for the image in the depth domain ¡
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and
denotes the data in the time domain. Amplitudes are accounted for with a weight function
that changes for each configuration and model dimension. In this paper, ¤ we
focus on the true-amplitude migration process. However, demigration as transformation
from depth to time is mentioned for completeness.
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TRUE AMPLITUDE PRESTACK MIGRATION AND DEMIGRATION
0 0.5 1 1.5 2 2.5
Time (sec)
Receiver Shot position Number (km)
0 1 2 3 4 5 46 7 8 9 10 6 11 12 13 148 15 16 17 18 10 19 20
Prestack Data
Figure 2: The first 10 shotgathers of the synthetic prestack dataset calculated by dynamic
raytracing. Only primary PP reflections were considered.
We first demonstrate the method using a simple model consisting of a dipping interface
which allows us to check the algorithm and compare amplitudes easily. An
input marine multicoverage dataset (Figure 2) was constructed using dynamic raytracing.
The data includes elastic amplitudes (however, only PP reflections were taken
into account) and 3D geometrical spreading, thus representing an acquisition line over
a 2.5D model. Figure 3 a shows the smoothed velocity model used to compute the
necessary one-way traveltimes and dynamic attributes. The migrated result is shown
in Figure 3 b for every offset. Due to the acquisition geometry, parts of the reflector