A SENSITIVITY ANALYSIS OF INVERSE SCATTERING MULTIPLE ATTENUATION TO SHALLOW WATERS

We here present a numerical sensitivity analysis of the inverse scatte ring multiple attenuation (ISMA) method to shallow water depths. We ha ve focused on two issues: (i) extrapolation of missing near traces and (ii) source signature estimation; a successful application of ISMA is dependent on the resolution of these two issues. We have generated no nlinear synthetic data for eight water depths from 30 to 240 m, every 30 m. The model used is one dimensional with a hard sea bottom. Below 60 m water depth, the multiple attenuation problem can be posed as a d econvolution problem, primaries and multiples are hardly distinguishab le. Assuming the nearest offset to be 200 m and using the classical cu bic spline interpolation method, we found that ISMA breaks dawn for wa ter depths less than 150 m. For these water depths, the occurrence of post-critical reflections before 200 m offset distorts the cubic splin e interpolation. For all the water depths studied in this experiment, the source estimation method in ISMA provides satisfactory results. Te sts with real data corresponding to 40 m water depth support the concl usions obtained on synthetic experiments.