Match beam inversion of geoacoustic parameters from towed hydrophone streamer array data

摘要

The study estimates geoacoustic parameters of the sediment by inversion of acoustic data acquired from seismic hydrophone streamer array. Inversion is performed by beamforming technique as the data is pertaining to shallow water and there is no prior information on the sediment type and the profiles of subbottom sediment layers. Initially, the estimates of sediment speed are obtained from critical angle derived from beamformer output by conventional beamforming. The sediment speed is used to set the parameter search bounds for further inversion by beamforming technique. The search bounds for density and compressional attenuation coefficient is set accordingly. The feasibility of inversion is understood by undertaking synthetic runs followed by inversion of field data. The beam cutoff angles are determined from the beampattern and the arrivals pertaining to the sea bottom. The geoacoustic model comprises of a water column, two sediment layers and a sediment half space. The inversion results of field data sets are compared with results obtained by modal inversion. The results show negligible variation in estimated sound speed indicating similar sediment type. The sediment density and compressional attenuation coefficient exhibits lesser sensitivity toward inversion process.