ASA 124th Meeting New Orleans 1992 October

4pUW2. Limitation of reflecting irregular bathymetry on matched-field processing.

Orest Diachok

James F. Smith

Acoust. Div., Naval Res. Lab., Washington, DC 20375

Simulations of the potential of matched-field tomography for inverting ocean sound-speed structure (Tolstoy and Diachok, 1991) have to date neglected effects of bottom interacting modes. A study to determine the effect of experimentally obtained bathymetry in the thinly sedimented Pacific on matched-field processing has been conducted. The range- and depth-dependent sound speed in the water column was obtained from tomography data. The acoustic field used as synthetic data ``measured'' at the array was calculated by the parabolic equation program FEPE (Collins, 1991). The program was shown to be highly accurate (0.15 dB at 1000 km at 15 Hz) in matched-field studies against ``exact'' results produced by the normal modes program KRAKEN (Porter, 1991) in a range-independent environment. The effects of irregular bathymetry and shifts in bottom sound speeds were studied through simulations conducted at a frequency of 14 Hz at various ranges and bottom sound speeds. The results showed an increase in signal array degradation and reduced source localization. Effects of interaction with far and near sides of seamounts (relative to array position), and the overall trend of signal loss with range due to multiple interactions with the bottom will be discussed.