Shallow water sediment properties derived from high‐frequency shear and interface waves

摘要: Low-frequency sound propagation in shallow water environments is not restricted to the column but also involves subbottom. Thus, as well being important for geophysical description of seabed, subbottom velocity/attenuation structure essential input predictive models. To estimate this structure, bottom-mounted sources and receivers were used make measurements shear compressional wave sediments continental shelf, usually where boreholes high-resolution reflection profiles give substantial supporting geologic information about subsurface. This colocation provides an opportunity compare seismically determined estimates physical properties seabed with “ground truth” properties. Measurements made 1986 source/detector offsets up 200 m producing velocity versus depth upper 30–50 (and P lesser depths). 1988 smaller source devices designed emphasize higher frequencies recorded by array 30 sensors spaced at 1-m intervals improve spatial sampling resolution structure. These investigations waves have shown that significant lateral vertical variations are common principally created erosional depositional processes associated glacial cycles sea level oscillations during Quaternary. When relatively uniform over length profiles, fields ordered, matching data full waveform synthetics has been successful, models consistent subsurface lithology indicated coring results. Both body interface modeled a function aid synthetic seismograms other analytical techniques. Some results strong evidence anisotropy heterogeneity 5–10 extremely high gradients topmost 1–2 m, possibly exceeding s−1.