ESTIMATION OF SHEAR-WAVE VELOCITY IN SHALLOW MARINE-SEDIMENTS

A method for estimating shear wave velocity in shallow marine sediment s from the dispersive characteristics of seismic interface waves trave ling at the water/sediment boundary is presented. Interface waves are recorded using an array of geophones placed on the seafloor, and the s hear 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 emphasi zing the capabilities and limitations of the method. The inversion sch eme has been tested at selected sites to compare its estimates with ex isting direct measurements of shear speed, and it has been proven reli able and accurate. Moreover, the proposed scheme is able to predict sh ear speed to a typical depth of 15-40 meters within the sediment, whic h generally exceeds the depth for which direct measurements are availa ble.