Delineating a low velocity zone using joint inversion of rayleigh-wave dispersion curve

Abstract

Seismic methods widely used to study the shallow subsurface for different purposes. Analysis of P-wave refraction cannot uniquely determine the seismic velocities as a function of depth when a low velocity layer is present. It is situation commonly encountered in geotechnical site investigation. Utilization of Rayleigh wave dispersion can be uses to determine the structure with existence of low velocity zone. In this study, we discuss efficiency and effectiveness of a joint inversion of Rayleigh wave dispersion curve which combining the genetic algorithm and the Occam’s algorithm to delineate a low velocity zone. Numerical test is presented. The shear wave velocity and thickness errors which is the difference between the true and inverted model parameters is used to appraise the value accuracy inversion model. The result provides accurate solution models with is 2.3 % and is 13.4%. Finally, we demonstrates the joint inversion scheme to invert Rayleigh wave dispersion curve which calculated by phase-shift method from a real example data.