Knobles D P, Hodgkiss William, Chaytor Jason, Neilsen Tracianne, Lin Ying-Tsong
Platt Institute of Nuclear Physics, P.O. Box 27200, Austin, Texas 78755, USA.
Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093, USA.
J Acoust Soc Am. 2024 Jun 1;155(6):3559-3567. doi: 10.1121/10.0026202.
The coherent recombination of a direct and seabed reflected path is sensitive to the geophysical properties of the seabed. The concept of feature-based inversion is used in the analysis of acoustic data collected on a vertical line array (VLA) on the New England continental shelf break in about 200 m of water. The analysis approach for the measurements is based on a ray approach in which a direct and bottom reflected path is recombined, resulting in constructive and destructive interference of the acoustic amplitudes with frequency. The acoustic features have the form of prominent nulls of the measured received levels as a function of frequency as a broadband (500-4500 Hz) source passes the closest point of approach to the VLA. The viscous grain shearing (VGS) model is employed to parameterize a two-layer seabed model. The most likely seabed is a sand sediment with a porosity of about 0.42. There is a possibility of a thin (less than 0.5 m) surface layer having a slightly higher porosity between 0.45 and 0.50. Using the estimates for the VGS parameters inferred from the short-range frequency features, a normal mode model is used to predict the received acoustic levels over larger range scales.
直达路径与海底反射路径的相干重组对海底的地球物理特性很敏感。基于特征的反演概念用于分析在新英格兰大陆架断裂处约200米水深处的垂直线列阵（VLA）上收集的声学数据。测量的分析方法基于射线方法，其中直达路径和海底反射路径进行重组，导致声振幅随频率产生相长和相消干涉。当宽带（500 - 4500赫兹）声源经过最接近VLA的点时，声学特征表现为测量接收水平随频率的显著零点形式。采用粘性颗粒剪切（VGS）模型对双层海底模型进行参数化。最可能的海底是孔隙率约为0.42的砂质沉积物。有可能存在一层薄（小于0.5米）的表层，其孔隙率略高，在0.45至0.50之间。利用从短程频率特征推断出的VGS参数估计值，使用简正波模型来预测更大范围尺度上的接收声级。
