A TIME-SERIES ANALYSIS OF SOUND-PROPAGATION IN A STRONGLY MULTIPATH SHALLOW-WATER ENVIRONMENT WITH AN ADIABATIC NORMAL-MODE APPROACH

Measured time series were generated by small omnidirectional explosive sources in a shallow water area, A bottom-mounted hydrophone recorded sound signals that propagated over a sloping bottom, The time series in the 250-500 Hz band were analyzed with a broad-band adiabatic norma l mode approach. The measured waveforms contain numerous bottom intera cting multipaths that are complicated by the subbottom structure that contains high-velocity layers near the water-sediment interface. Sever al of the details of the geoacoustic structure and the depth of the wa ter column at the receiver are inferred from comparisons of the measur ed data to simulated time series. The sensitivity of broad-band matche d-field ambiguity surfaces in the range-depth plane for a single recei ver to selected waveguide parameters is examined, A consistent analysi s is made where the simulated time series are compared to the measured time series along with the single-receiver matched-field localization solutions for ranges out to 5 km. In this range interval, it was foun d that the peak cross-correlation between the measured and simulated t ime series varied between 0.84 and 0.69, The difference between the GP S range and the range obtained from the matched-field solution varied from 0 to 63 m, The geoacoustic structure obtained in the analysis con sists of an 8-m low-velocity sediment layer over an 8-m high-velocity layer followed by a higher velocity, infinite half-space.