ASA 124th Meeting New Orleans 1992 October

2pAO6. Issues important in modal tomography.

E. C. Shang

Y. Y. Wang

CIRES, Univ. of Colorado/NOAA/Wave Propagation Lab., 325 Broadway, Boulder, CO 80303

T. F. Gao

Inst. of Acoust., Academia Sinica, Beijing, People's Republic of China

Modal ocean acoustic tomography working at lower frequencies (lower than 100 Hz) is appropriate for basin scale ocean monitoring. One of the advantages of modal tomography is that it does not need to identify rays and measure the travel time by identified and resolved rays as in ray tomography. With a vertical receiving array, the modal features of each individual mode can be measured by mode filtering, or on the other hand, to measure the total field at each hydrophone for the matched-field processing (MFP). However, there are some important issues that need to be investigated and clarified. The following issues will be addressed in this talk: (1) The forward model (data) should be based on adiabatic or nonadiabatic mode? (2) The measured modal features (travel time perturbation, etc.) have a linear or nonlinear relationship with the sound-speed profile (SSP) perturbation? (3) How to solve the 2(pi) ambiguity in modal phase tomography? [Work supported by NOAA.]