ASA 125th Meeting Ottawa 1993 May

3aUW11. Imaging of ocean subbottom structure using swath mapping data: Feasibility studies.

Mrinal K. Sen

Faruq A. Akbar

Paul L. Stoffa

Inst. for Geophys., Univ. of Texas at Austin, 8701 N. MoPac Expwy., Austin, TX 78759

Joseph A. Gettrust

NRL-Stennis Space Center, MS 39529

With the aim of resolving small scale geologic features within upper 100 m of sediments, NRL-SSC has developed a high-resolution swath mapping device based on SeaMARC sidescan sonar technology but with additional parametric 500-Hz, 1-kHz, and 2-kHz source capability. Methods have been developed for modeling and imaging of such data in order to address the problem of image resolution. A modeling method that uses an elastic Kirchhoff--Helmholtz (KH) formulation rapidly calculates the arrival time, and amplitude of scattered signal. KH synthetics have been compared with elastic finite difference results. Synthetic phase data are computed by ray tracing for a given subsurface model. Also, a Kirchhoff migration code has been developed that uses both the travel time and angle for imaging conditions. The imaging method has been tested on synthetic data with various degree of random noise added so as to investigate how the signal-to-noise ratio affects the images. These methods will be applied to real data collected by NRL. Like any imaging method, we require an estimate of subsurface velocity. This is being done by using several different possible velocity models and comparing the imaging results. [Work supported by ONR.]