Geoacoustic Inversion of Mid-Frequency Bottom Loss Data in Shallow Water off the East Coast of Korea

Abstract

Mid-frequency bottom loss measurements over a grazing angle range of 25 to 70 degrees at frequencies of 6, 8, and 10 kHz were made off the east coast of Korea in October 2008. In this paper, geoacoustic parameters including the sediment sound speed, density, attenuation coefficient, and thickness of the surficial sediment layer are estimated via comparison between the measured bottom loss and a bottom reflection forward model based on the two-layered fluid sediment structure. A global search is performed over the search space of geoacoustic parameters by a genetic algorithm method, in which the weighted squared error between the data and the model predictions is used as an objective function to be minimized. The inversion result shows that a thin lower sound speed layer with a thickness of 0.4m overlies the higher sound speed sediment. This result is consistent with marine geological observations conducted at the experimental site. (C) 2012 The Japan Society of Applied Physics