Wavefield-extrapolation imaging for echo data of sea-bed sediment layers

I.IntroductionImagingechodataofseabedsedimentlayersisoneofimportantpartsingeoacousticalstudies.Theechodatareflectedfromtheillterfacesofsea-bedlayersarereceivedatseasurfacebyahydrophonestreamerwithaseismicprofiler.Throughimageprocessing,theacctiratestructureofseabedsedimentlayerscanbereconstructedeffectively'l'].Thusthismethodisoftenregardedasatoolfortargetdetection.Anexampleofcommon-shot-pointrecordstoexplainthesignificanceofthemethodisshownasfollows:InFig.1(a),Risalayerbetweentwohomogeneou…

Wavefield-extrapolation imaging for echo data of sea-bed sediment layers

Imaging sea-bed sediment layers from echo data, which are collected by a system composed of a seismic profiler and a hydrophone streamer towed behind the profiler, is a way to reconstruct the structure of sedimeat layers with acoustic wav equation. The equation which describes the wave propagation is used for backward extrapolation of echo data observed at sea surface. When the medium is homogeneous or horizontally layered, time imaging approach is valid. However, in the case where a considerable lateral variation in velocity exists, the image section processed with the time approach does not represent the real structure, because of distortions caused by thin-lens effect similar as in optics. In this case, depth imaging approach must be used for both the time-shift correction of refraction terms and the convergence of diffractions simultaneously as wavefields are downward continued. As a result, the good image can be derived to determine the structure of sea-bed sediment layers.