Characterisation of a Subsidence Zone by Means of Ert, Refraction Seismic and Remi: A Case Study

Abstract

Summary The neighbourhood of “Barri de l’Estació” is located in the south of the municipality of Sallent de Llobregat, in the Bages region, Spain. During the twentieth century, the main locality’s socioeconomic activity was based on extracting potash from the Cardona Formation through the Enrique Mine’s underground galleries. The galleries, in combination with various regional and local compressive structures and the presence of three aquifers have produced differential settlement and subsidence of such a magnitude that in 2009 all the residences and buildings in the area were demolished. Several geophysical studies have been carried out to explore the subsurface and locate a cavity discovered in 1954 by the mining company Potasas Ibéricas S.A. up to 110 metres high, with the roof located 160 metres below the “Barri de l’Estació” zone. In this study, we have carried out near-surface geophysical surveys using refraction seismic, MASW seismic and electrical tomography in order to characterize the subsurface of the area affected by subsidence. The results show a relationship between the most affected zones by subsidence phenomena and low values of both resistivity and P and S wave velocities.