Joint traveltime tomography for seawater based on ocean bottom seismometer and towed streamer observations
In marine seismic exploration,overlooking the heterogeneity of seawater can introduce artifacts in subsequent tomography or imaging process.Therefore,it is crucial to establish precise seawater velocity model.The data captured by ocean bottom seismometers(OBSs)records transmitted waves with substantial ray angles,offering valuable vertical resolution for seawater velocity modeling.Towed streamer observations can complement the under-sampling issues resulting from the sparse distribution of OBSs.Additionally,they help determine seafloor depth,which,in turn,can be used to update OBS positions.The combined utilization of OBS and towed streamer observations allows us to overcome the limitations of each method and significantly enhances the accuracy of seawater velocity modeling.This paper proposed a joint tomographic method based on OBS and towed streamer observations.It leverages the traveltimes of seawater-transmitted waves and seabed-reflected waves to inverse the distribution of seawater sound velocity and seabed depth while concurrently updating OBS depths.The validity of this method is confirmed through both two-dimensional theoretical models and field data experiments.The results unequivocally demonstrate that this proposed approach accurately determines seawater sound velocity distribution and seabed depth,consequently improving the alignment of traveltimes with seismic phases and providing a precise model of heterogeneous seawater velocity for subsequent imaging.
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