Apex-Shifted Diffraction Model Building

Process designed to generate the model of Apex-Shifted Diffraction Multiples (ASDM)

The calculation is based on a simple constant velocity migration/demigration on prestack gathers. The input must be in 2D cmp gathers. The output is either image or model in the same type of gather.

In order to select the ASDM, the process first transforms the data into image domain by utilizing a simple constant velocity migration. Then the image undergoes several steps for the selection of the ASDM. In practice, these steps include: 1) a near-offset mute to mute the primary events; 2) a top mute to mute above water-layer related multiple; and 3) an amplitude thresholding step to select the strong events in the image domain. In the last step, various amplitude averaging schemes can also be considered.

For the thresholding step in the image domain, the whole gather can be considered as one window or multiple windows, in which amplitude averaging and a constant threshold factor are calculated within each window and interpolated smoothly between the centers of the windows and then applied. Demigration of the image after thresholding/selection in the image domain will reveal the stronger events in the x-t domain. An additional thresholding step can be applied in the x-t domain to obtain the final model.

Commonly, an adaptive subtraction step follows this process to remove the apex-shifted diffraction multiples from the input data.

ApexShifted Diffraction Model Building

Apex ApexShifted Diffraction Model Building

Move the Slider Left or Right to see before and after

Got it
Stack after DME
Stack after 2DSRME

Example Set 2:

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to Visualize the Images

Got it
CDP Gather After DME
CDP Gather After DME
Input CDP gathers
Input CDP Gathers
Differnece Difference