ASA 126th Meeting Denver 1993 October 4-8

4aUW3. Trends in signal loss due to reflecting irregular bathymetry in matched-field processing.

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 bathymetry in the thinly sedimented Pacific on matched-field processing has been conducted. A range- and depth-dependent sound-speed field was used. 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 in matched-field studies against ``exact'' results produced by the normal modes program KRAKEN (Porter, 1991). The effects of irregular bathymetry and shifts in bottom sound speeds were studied through simulations conducted over extensive range and frequency intervals. The results showed an increase in signal array degradation with increasing range and frequency 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.