Geotechnical investigation using interface waves for determination of shear properties in the upper seafloor

This paper presents the results of an experiment conducted to determine shear wave velocity as function of depth using an array on the seafloor and explosive sound sources. The equipment used is the same as normally used in refraction surveying. By increasing the recording time, also the slower propagating interface waves is captured in addition to the faster refracted compressional waves. The analysis is first to determine the dispersion characteristics of the recorded interface wave and secondly to convert dispersion into shear speed as function of depth in the seafloor. The result of the experiment is compared with the shear values obtained in an geotechnical investigation that had been conducted earlier at the same site. The comparison shows that the acoustically determined shear profiles are quite similar to those obtained by geotechnical investigation and evaluation. It is therefore concluded that the approach can be used as an addition and supplement in refraction surveying giving a estimate of the shear profile of the seafloor.