REMOTE DETERMINATION OF IN-SITU SEDIMENT PARAMETERS USING LOVE WAVES

In situ properties of near-bottom sediments are determined using an ex perimental technique based on the dispersive properties of horizontall y polarized surface waves generally known as Love waves. This techniqu e basically consists of generating the Love waves, analyzing the recor ded seismic signals to determine dispersion, and, finally, mathematica lly inverting the dispersion data to obtain a geoacoustic model of the sediment. In the field experiments, Love waves are generated using a torsional source and the generated signals are recorded with a linear array of gimbaled geophones that measure transverse horizontal motion. Experimental dispersion curves (wave velocity versus frequency), are then obtained from the recorded wavelets. These velocity waveforms are usually composed of overlapping modes and in order to reduce the infl uence of modal interference on the experimental phase velocity dispers ion curves, a phase-matched filter is used to extract a smoothed phase velocity dispersion curve for the fundamental mode. The dispersion cu rve is then mathematically inverted to obtain a sediment model using a constrained least-squares method with singular-value decomposition an d it is shown that the maximum parameter resolution depth can be estim ated from the generalized inverse. Practical use of the technique is d emonstrated by an analysis of the results of a field experiment carrie d out in a marine sand sediment. (C) 1995 Acoustical Society of Americ a.