Assessing the risk of subsidence of a sinkhole collapse using ground penetrating radar and electrical resistivity tomography

In Segovia Province, Spain, there are numerous carbonate rock outcrops that are affected by karstification processes, in which there are numerous galleries, caves and sinkholes. This is the case of the Sima de Madrona, a sinkhole collapse caused by the sinking of dolostone. The objective of this study was to ascertain the existence and the characteristics of cavities and galleries, as well as to evaluate the risk of subsidence in the area, by applying shallow and non-invasive geophysical techniques: ground penetrating radar and electrical resistivity tomography. The joint combination of these two independent shallow geophysical techniques has provided the best combination of investigation depth (up to 8 m) and resolution needed to image small to medium (~ 1 to 4 m) size cavities. The associated risks are evident because the cavities found herein affect various anthropic structures: a highway and crop fields.

► GPR and ERT techniques are useful to detect underground cavities.
► Both known and unknown cavities related to a sinkhole have been detected.
► Shallow geophysical methods are useful for assessing the risk of subsidence.