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

1pUW20. Preliminary analysis from rapid-fire experiment over Whiskey Hole; ARSRP '93.

J. Robert Fricke

Dept. Ocean Eng., 77 Massachusetts Ave., Cambridge, MA 02139

This paper presents a preliminary analysis of the rapid-fire data taken over Whiskey Hole during the Cory '93 cruise. The data were collected at 90-s ping intervals to investigate variability between pings and to map the basement under the Whiskey Hole sediment pond. Analysis shows that the sediments at this site have a maximum thickness of 150 m. Over a range of grazing angle 30(degrees)<(gamma)<90(degrees), attenuation due to the sediments is modest, maximum of 3 dB, both over the pond and on the hill sides surrounding the pond. Heterogeneity of the sediments is unimportant. Surface waves effects are not seen in the data, which is discrete in both cross and along track directions. A scatterer density of O(10) per square kilometer is estimated with an average lineal spacing between scatterers of 250 m. Most of the data observed are vertically propagating multipath reverberation. In a small window near the beginning of the record direct scatter is seen. Also, occasionally in the late-time record a few high-energy direct scatter events are seen punching through the reverberant noise floor. [Work supported by ONR.]