Subbottom profiling using a ship towed line array and geoacoustic inversion.
Bottom profiling traditionally uses broadband signals received on a line array at long ranges to estimate the bottom layer structure and thickness. In this paper, a subbottom profiling method is developed and applied to a ship-towed line array using the same ship towed source to estimate the subbottom layer structure and thickness. A ship towed line-array system can be used to estimate bottom properties using geoacoustic inversion and can cover a wide area in a short time. It needs some prior information about the subbottom structure and layer thickness, without which the solution can be ambiguous and even erratic when resolving parameters over a wide area. It is shown that the required subbottom information can be obtained from the time-angle relation by beamforming the same acoustic signal data used for geoacoustic inversion. The time-angle analysis is used to expose the prevalent physics intrinsic to geoacoustic inversion. One finds that the tau-p relation of the bottom and the bottom reflection coefficients, sampled at discrete angles associated with bottom and multiple surface-bottom returns, are often adequate, for many practical applications, to uniquely determine the geoacoustic bottom at low (< or =1 kHz) frequencies.
Yang
T C
TC
Naval Research Laboratory, 4555 Overlook Ave., Washington, DC 20375, USA. yang@wave.nrl.navy.mil
Yoo
Kwang
K
Fialkowski
L T
LT
D000162:Acoustics; D019015:Geologic Sediments; D008962:Models, Theoretical; D009038:Motion; D009791:Oceanography / Q000379:methods*; D009792:Oceans and Seas; D012767:Ships; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013997:Time Factors