The application of GPR and ERI in combination with exposure logging and retrodeformation analysis to characterize sinkholes and reconstruct their impact on fluvial sedimentation |
| |
| Authors: | Mario Zarroca Xavier Comas Francisco Gutiérrez Domingo Carbonel Rogelio Linares Carles Roqué Morteza Mozafari Jesús Guerrero Xavier M Pellicer |
| |
| Institution: | 1. Department of Geology, Autonomous University of Barcelona, Barcelona, Spain;2. Department of Geosciences, Florida Atlantic University, Davie, FL, USA;3. Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Zaragoza, Spain;4. àrea de Geodinàmica Externa i Geomorfologia, Universitat de Girona, Girona, Spain;5. Department of Earth Sciences, Shiraz University, Iran;6. Geological Survey of Ireland, Dublin, Ireland |
| |
| Abstract: | This work illustrates the practicality of investigating sinkholes integrating data gathered by ground penetrating radar (GPR), electrical resistivity imaging (ERI) and trenching or direct logging of the subsidence‐affected sediments in combination with retrodeformation analysis. This mutidisciplinary approach has been tested in a large paleosinkhole developed during the deposition of a Quaternary terrace on salt‐bearing evaporites. The subsidence structure, exposed in an artificial excavation, is located next to Puilatos, a village that was abandoned in the 1970s due to severe subsidence damage. Detailed logging of the exposure revealed that the subsidence structure corresponds to an asymmetric sagging and collapse paleosinkhole with no clear evidence of recent activity. The sedimentological and structural relationships together with the retrodeformation analysis indicate that synsedimentary subsidence controlled channel location, the development of a palustrine environment and local changes in the channel pattern. GPR profiles were acquired using an array of systems with different antenna frequencies, including some recently developed shielded antennas with improved vertical resolution and penetration depth. Although radargrams imaged the faulted sagging structure and provided valuable data on fault throw, they did not satisfactorily image the complex architecture of the fluvial deposit. ERI showed lower resolution but higher penetration depth when compared to GPR, roughly capturing the subsidence structure and yielding information on the thickness of the high‐resistivity alluvium and the nature of the underlying low‐resistivity karstic residue developed on top of the halite‐bearing evaporitic bedrock. Data comparison allows the assessment of the advantages and limitations of these complementary techniques, highly useful for site‐specific sinkhole risk management. Copyright © 2016 John Wiley & Sons, Ltd. |
| |
| Keywords: | evaporite karst near‐surface geophysics trenching sagging sinkhole Ebro Valley (northeast Spain) |
|
|
