Use of Rayleigh and Love waves in Seismic Surface wave testing

Abstract

Seismic surface wave tests have made an impact in the Geotechnical Engineering industry due to their non-invasive and inexpensive procedures for attaining important soil parameters, such as the small strain shear modulus (G0) by measuring the shear wave velocity (Vs) profile. Essentially, conventional surface wave tests incorporate Rayleigh waves alone due to the ease in their generation and detection in the fields. However, another type of surface wave, known as Love waves, is often neglected during testing due to the difficulties faced in integrating Love waves in the tests. The study explored the use of both Rayleigh and Love waves to obtain the Vs profile using synthetic data and experimental data, which was collected at two selected test sites. Two approaches were investigated for the generation of Love waves through the Continuous Surface Wave (CSW) tests and Spectral Analysis of Surface Wave (SASW) tests using standard test specifications. Surface wave signals from these tests were processed using Python based codes to determine and interpret the respective dispersion points. The dispersion data from both the synthetic and experimental data were used to conduct discrete and joint inversions, from which the spread in the Vs profiles was evaluated within misfit limits. The study demonstrated that by using both Rayleigh and Love waves in a joint inversion, the spread in the Vs can be reduced compared to using Rayleigh waves alone. However, this is only possible when the quality of the Rayleigh and Love wave signals are good. The generation of good quality Love wave signals remains a major problem when using joint inversions and it is recommended that newer and improved designs be tested and evaluated.