Surface wave tomography using active sources in engineering applications: A 3D experiment at a test site of known conditions

In this study a specific workflow is proposed for the application of Surface wave tomography in near surface applications using active sources. The proposed methodology can be implemented in 2D or 3D acquisition schemes, resulting in high resolution phase and group surface wave velocity maps that can be used for Vs estimation in the survey area. Our methodology starts with the implementation of a pre-processing procedure in which a series of common steps for the quality control and optimization of the data is applied. Then, a reliable reference phase velocity dispersion curve can be estimated internally from our data. This reference curve is used for the automatic assignment of phase and group delays between nearby stations in the time domain. Afterwards, high precision frequency-dependent phase and group velocity maps can be produced through inversion with the Eikonal equation. The proposed methodology is evaluated by application in a 3D acquisition example in a controlled test of known conditions. The resulting frequency-dependent phase and group velocity maps delineate efficiently the expected lateral and depth variations in the survey area. The comparison of the results with available geotechnical information and other geophysical methods confirms the method's validity, demon-strating the effectiveness of the technique and its value in near surface applications as an attractive tool for the calculation of quasi-3D shear wave velocity for a survey area.