Statistical approach for cavity detection using seismic refraction and electrical resistivity data

Abstract

To test limitations and effectiveness of seismic tomography when coupled to geoelectrical technique for cavity detection 2D synthetic models were used. Synthetic models were created with different number of cavity and blocks of highly cohesive lithological material (high seismic velocity and resistivity values). A modified version of multiple gradient (Martorana et al., 2016) has been used for electrical sequence. The cluster analysis performed on static units defined by electrical resistivity values, P wave velocities, and seismic density on coincident sections, allowed to interpret subsoil structures. The use of the non-hierarchical clustering algorithm has been chosen because it is less influenced by abnormal values, and allows a statistical unit to change its cluster during the iterative process. Depending on the choice of the number of clusters to be identified, cluster distribution maps have been constructed in the multi-parameter space, allowing defining certain variability limits for the selected parameters, for synthetic and experimental data. Finally, experimental data show that electrical and seismic tomographies is not influenced by the presence of cavities without lateral continuity.