Geoacoustic inversion with two source-receiver arrays in shallow water.
A geoacoustic inversion scheme based on a double beamforming algorithm in shallow water is proposed and tested. Double beamforming allows identification of multi-reverberated eigenrays propagating between two vertical transducer arrays according to their emission and reception angles and arrival times. Analysis of eigenray intensities yields the bottom reflection coefficient as a function of angle of incidence. By fitting the experimental reflection coefficient with a theoretical prediction, values of the acoustic parameters of the waveguide bottom can be extracted. The procedure was initially tested in a small-scale tank experiment for a waveguide with a Plexiglas bottom. Inversion results for the speed of shear waves in Plexiglas are in good agreement with the table values. A similar analysis was applied to data collected during an at-sea experiment in shallow coastal waters of the Mediterranean. Bottom reflection coefficient was fitted with the theory in which bottom sediments are modeled as a multi-layered system. Retrieved bottom parameters are in quantitative agreement with those determined from a prior inversion scheme performed in the same area. The present study confirms the interest in processing source-receiver array data through the double beamforming algorithm, and indicates the potential for application of eigenray intensity analysis to geoacoustic inversion problems.
Sukhovich
Alexey
A
Laboratoire de Géophysique Interne et Tectonophysique, Université Joseph Fourier, CNRS UMR 5559, Grenoble 38041, France. alexey.sukhovich@obs.ujf-grenoble.fr
Roux
Philippe
P
Wathelet
Marc
M
D000162:Acoustics / Q000295:instrumentation*; D000465:Algorithms; D004867:Equipment Design; D005844:Geology / Q000295:instrumentation*; D008962:Models, Theoretical; D009038:Motion; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D014867:Water
D014867:Water