ASA 127th Meeting M.I.T. 1994 June 6-10

3pUW1. High-resolution geoacoustic modeling for SWellEX-1 using a geographic information system (GIS).

Richard T. Bachman

Ocean and Atmospheric Sci. Div., Code 541, NRaD, San Diego, CA 92152-6435

The SWellEX-1 (shallow-water evaluation cell) area is a complex shallow water environment of approximately 400 km[sup 2] immediately offshore of San Diego, California. In it, thinly sedimented terraces separate steep scarps. The terraces and scarps are old erosional surfaces with moderate relief. Sediment thickness ranges from zero to tens of meters over a basement of sandstone and mudstone. The IDRISI geographic information system was used to assemble and analyze geologic and geoacoustic data, and to provide that data to a database server that will support high-fidelity acoustic simulation codes. Data for the initial effort consisted of SeaBeam and National Ocean Service depth soundings, published geological maps, published sediment thickness charts combined with the results of a shallow seismic reflection survey, and published sediment charts. Data provided to the acoustic codes at a grid spacing of 2 arcseconds are depth; sediment thickness; sediment compressional and shear properties and density (varying with depth in the sediment); and basement properties.