Thickness Variations in Layered Subsurface Models - Effects on Simulated MASW.

Seismic surface wave methods allow to retrieve the shallow subsurface shear wave velocity. Among these, the “Multi-channel Analysis of Surface Waves” is to date one of the most widely adopted non-invasive active-source approaches in the professional world for the evaluation of the stiffness properties of the ground for geotechnical engineering purposes. The method utilizes the dispersive nature of surface waves by constructing the dispersion curve which is then inverted to obtain the shear wave velocity profile. Dispersion curves generation typically requires the transformation of the recorded seismograms into the frequency-velocity (f-V) domain. Commercially available inversion algorithms assume the subsurface model as a stack of homogeneous parallel layers, but unfortunately this may lead to misleading results if the actual soil profile is far from the assumed 1D geometry. We nvestigate the effects of lateral heterogeneities due to variations of layer thicknesses on the f-V spectrum to assess the limitations of the 1D approach and thus to judge the reliability of such surface waves interpretation.