ESTIMATION OF SHEAR-WAVE VELOCITY IN SHALLOW MARINE-SEDIMENTS

A method for estimating shear wave velocity in shallow marine sediments from the dispersive characteristics of seismic interface waves traveling at the water/sediment boundary is presented. Interface waves are recorded using an array of geophones placed on the seafloor, and the shear wave velocity is estimated by a nonlinear least-square inversion algorithm, with smoothing constraints to avoid numerical instability. A detailed description of the algorithm is given, particularly emphasizing the capabilities and limitations of the method. The inversion scheme has been tested at selected sites to compare its estimates with existing direct measurements of shear speed, and it has been proven reliable and accurate. Moreover, the proposed scheme is able to predict shear speed to a typical depth of 15-40 meters within the sediment, which generally exceeds the depth for which direct measurements are available.