Laboratoire de Géophysique Interne et Tectonophysique, Université Joseph Fourier, CNRS UMR 5559, Grenoble 38041, France.
J Acoust Soc Am. 2010 Aug;128(2):702-10. doi: 10.1121/1.3455822.
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.
提出并测试了一种基于浅海双波束形成算法的地声反演方案。双波束形成允许根据发射和接收角以及到达时间识别在两个垂直换能器阵列之间传播的多反射本征射线。本征射线强度分析得出作为入射角函数的底部反射系数。通过将实验反射系数拟合到理论预测中，可以提取波导底部的声参数值。该过程最初在具有有机玻璃底部的波导的小尺度水箱实验中进行了测试。有机玻璃中剪切波速度的反演结果与表值吻合较好。类似的分析应用于在地中海近岸浅水区进行的海上实验中收集的数据。底部反射系数与底部沉积物建模为多层系统的理论相拟合。从同一区域进行的先前反演方案中得出的底部参数与所得到的参数定量一致。本研究证实了通过双波束形成算法处理声源-接收器阵列数据的兴趣，并表明了本征射线强度分析在地声反演问题中的应用潜力。
