Wave-equation based migration of primaries and free-surface multiples simultaneously with artifact suppressing.

Free-surface related multiples exist widely in marine seismic data. Imaging with multiples rather than suppression has particular benefits because multiples have more information than primaries, such as wider illumination and higher vertical resolution. One-way wave-equation based pre-stack depth migration (OWPSDM) is an effective imaging tool with high calculation efficiency. By using an OWPSDM operator, primaries and multiples are imaged simultaneously. The artifacts caused by the cross-correlation between forward-propagated source and backward-propagated multiples can be suppressed by an approach with the following three steps: for the first step, the source is replaced by the recorded field data together with a wavelet and the data is the recorded field data. The imaging results contain both real structure images and artifacts. For the second step, the source is the wavelet and the data is replaced by the predicted free-surface related multiples. Artifacts can be obtained after using the imaging condition at each depth. Lastly, artifacts can be suppressed by adaptive subtraction from the images obtained in the first step. Numerical tests on synthetic data of a three-layer model show that our scheme provides regions with wider illumination and balanced image amplitudes compared to the images obtained with primaries only. Artifacts caused by the cross-correlation between a forward-propagated wavelet and backward-propagated free-surface multiples were properly predicted and suppressed. Applying the proposed method to real deep marine data shows that the image quality of deep target layers is improved, with balanced illumination and fewer artifacts. [ABSTRACT FROM AUTHOR]