GPR application for the characterization of sinkholes in Teresina, Brazil

Abstract

The town of Teresina, in the state of Piauí, Brazil, presents a history of land sinking processes. Two sinking events deserve to be highlighted, the frst occurred in 1999 at Simplício Mendes Street and the other occurred on July 31, 2008, at Francisco Mendes Street. To identify possible shallow caves and associated structures, the Geological Survey of Brazil/CPRM developed a Ground Penetrating Radar (GPR) study to verify the ccurrence of refection patterns characteristic of these dissolution structures. In the feld, the team conducted GPR sections along streets with a history of collapse. The GPR results obtained with shielded antennas of 200 MHz allowed the identifcation of old areas of collapse of the terrain, to a maximum depth of 3m. In addition, the results obtained by this study show the potential of applying the GPR method in the characterization of the subsoil of paved streets, making it possible to identify various layers: asphalt, actual pavement, subgrade pavement, soil, saprolite, and mixed material. The high clay content of the subsoil does not allow the GPR to investigate further depths in the research area. The interpretation of aero-magnetometric data shows that the occurrence of sinkholes is associated with magnetic lineaments mainly in the NW–SE direction and enhances the understanding of the structural framework of the study area.