Kirchhoff Migration
The same techniques applied on the zero-offset section with the single hyperbola were applied on the zero-offset CMP section. For this section, the subsurface distance between CDP's was 20 meters instead of 25. This section has a single, homogeneous boundary at a 400 meter depth. From our data, we can observe it is found at the 0.55 second 2 way traveltime. In order to obtain an approximate migration velocity, we divided the distance by half the travel time: \(v=\frac{d}{t}=\frac{2\left(400\ m\right)}{0.55\ s}=1455\ \frac{m}{s}\). We chose this approximate velocity as our constant velocity value in the VFNDEF module.
We adjusted our display parameters to be able to visualize the reflector we were interested in (Fig \ref{618756}). The AGC window was adjusted to 500 ms and the data was gained by -2 dB. This way we could observe the data between 0.00 and 1.00 seconds that was barely visible before, without gaining the reflectors below 0.55 seconds too much. Those had negative amplitudes, meaning that it was just artifact error. The main interface is the strongest reflector, which is what we wanted. After applying the Kirchhoff migration module with a 20 meter spacing between CDP's and 60° as the maximum dip to migrate, the data showed some curvature when approaching the syncline (Fig \ref{268565}). The maximum dip was changed to 30° to observe the results when the angle was decreased (Fig \ref{905736}). The reflector near the syncline became faded and less continuous. We increased the velocity to 1600 m/s and returned the dip angle to 60 (Fig \ref{126906}), which gave us the right migration. The boundary clearly shows a syncline in the middle of the data. Anything over 1600 m/s would overmigrate the data, giving us a hyperbola that curved upwards. We changed the angle of maximum dip to migrate to 45 and 80 under the same velocity of 1600 m/s, which did not have any significant changes in the data.