Initial errors

From the initial migration I chose five reflectors to perform tomography with (Figure ). To constrain the upper portion of the model I chose the sea bottom reflection. 2-D tomography tests Clapp and Biondi (2000) indicated that largest error in the upper portion of the model was below the reflection at 1600 m. As a result I chose this reflector along with the salt top reflection and two reflectors on either side of the salt dome. To handle the steering filter dip calculation more accurately, I extend the reflectors on either side of salt artificially into the salt.

 

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Figure 3 Five reflectors used in tomography superimposed on the initial migration image. Note how two of the reflectors were extended into the salt to create better smoothing directions for the steering filter.

Excluding the artificially created reflector portions, I then calculated residual moveout along each of the reflectors (Figure ). Generally the second reflector showed little to no moveout errors while the three below showed some moveout error, especially directly above and the edge of the salt body.

 

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Figure 4 Initial semblance errors along the lower four reflectors used in tomography.