ASA 124th Meeting New Orleans 1992 October

1aUW5. Simulation of two-dimensional, fine-scale geomorphology.

J. W. Caruthers

NRL, Code 240, Stennis Space Center, MS 39529

J. C. Novarini

Planning Systems, Inc., Long Beach, MS 39560

Recent experimental work in the Acoustic Reverberation Special Research Program (ARSRP) demonstrated a need for two-dimensional fine-scale geomorphology to help explain observed scattering at 250 Hz in a rugged region just west of the Mid-Atlantic Ridge. Bathymetry resolved in 2-D to 100 m is available for the region, but at this frequency geomorphology at horizontal scales (about 1 m) is required. One-dimensional geomorphology with sufficient resolution has been simulated and molded to regional bathymetry established by a single line bathymetric profile resolved to 1 km by Goff and Jordan [WHOI ARSRP TN#2 (1992)] based on their earlier work [J. Geophys. Res. 93, 13 589--13 608 (1988)]. While some scattering theories can handle only 1-D geomorphology and produce 2-D scattering fields, others are designed to use 2-D geomorphology and produce 3-D scattering fields. Caruthers and Novarini had earlier developed a 2-D surface simulation technique [TAMU TN#71-13-T (1971)] that, so far, had been applied only to sea-surface simulation and scattering [J. Acoust. Soc. Am. 53, 876--884 (1973) and J. Acoust. Soc. Am. 91, 813--822 (1992)]. Although the simulation technique presented here is essentially the same as that developed by Caruthers and Novarini and Goff and Jordan, unique features of this current work are (1) the sea floor is simulated in fine-scale detail in 2 D, (2) local spectra of deterministic bathymetry in small regions are use to dictate the form of spectra extended to higher resolution, and (3) the technique for molding the simulated geomorphology to the deterministic bathymetry using a coupling of wave-number bands is new. [This work is supported by ONR.]