ASA 126th Meeting Denver 1993 October 4-8

2pUW9. Long-range continuous-wave and time-domain simulations of ocean acoustic scatter from a subbottom anelastic corner.

Stanley A. Chin-Bing

Naval Res. Lab., Stennis Space Center, MS 39529-5004

Joseph E. Murphy Gongqin Li

Univ. of New Orleans, New Orleans, LA 70148

Recent long-range acoustic reconnaissance experiments done in the mid-Atlantic ridge region show strong reverberation from many ocean bottom features. Two types of features characteristic of this region, and possible contributors to this reverberation, are seafloor ridge corners---``inner'' corners and ``outer'' corners---formed by two ridge faces intersecting at near-right angles. Corners formed by faces intersecting at near 90(degrees) are termed ``inner'' corners and those formed by faces intersecting at near 270(degrees) are termed ``outer'' corners. Via computer simulations, the effects of an anelastic seafloor corner on the acoustic field originating from a distant source have been investigated. Both an ``inner'' corner and an ``outer'' corner were used in the study. The effects of thin sediment layers covering the corners were also investigated. Simulations were made using continuous-wave (cw) computer models: the parabolic equation model, fepe, for long-range propagation of the acoustic fields to and from the vicinity of the corners, and the seismoacoustic finite-element model, safe, to determine the scattered fields from the anelastic corners. Time-domain calculations were obtained from FFTs of the cw fields. Examples will be presented that show the effects from these two corner types. [Work supported by NRL, ONR, and the ONR Acoustic Reverberation SRP.]