ASA 126th Meeting Denver 1993 October 4-8

2aAO7. Broadband geoacoustic inversion in shallow Arctic water.

John W. Wolf

Naval Res. Lab., Washington, DC 20375

A broadband technique used successfully to localize acoustic sources and determine water depth and array position at a deep Pacific Ocean site [P. C. Mignerey, Oceans '90 Proc., 121--124] is used to determine geoacoustic parameters at a shallow water site in the Arctic. The technique minimizes differences between calculated impulse response times and pulse arrival times measured on a vertical array. Initially the method is used to localize the source (SUS) and determine bottom depth and array orientation. The method is then applied to pulse arrivals that penetrate the upper sedimentary layers of the shallow bottom. The inversion provides compressional speed profiles and sediment layer thicknesses of the bottom near the array site. Differences between calculated arrival times and data show a significant decrease, i.e., improvement, when using the geoacoustic profile as determined by the inversion technique. Broadband matched-field processing is used to demonstrate inversion effects on processor performance. The results demonstrate the broadband method to be useful for geoacoustic surveys of shallow water environments.