Publication Date:
2002-09-01
Description:
Resistivity imaging (electric tomography) is a methodology for defining lateral variations of resistivity associated with structural anomalies such as caves, water contamination, and fractured zones among others. Important urban areas in Mexico City are currently at high risk of collapse. Cavities and shallow fractures have been created as a result of mining in hilly regions beneath several of today’s urbanized neighborhoods located in the southwestern portion of Mexico City. Selected areas have been investigated. Caves and tunnels were found for depths ranging between [Formula: see text] up to [Formula: see text]. Diameters of such features were between [Formula: see text] up to [Formula: see text]. Some of these structures are across paved roads and beneath buildings and houses, running for several tens of meters in length. Topographic effects were also studied in one profile. It showed important inaccuracies in resolving the geometry of the cave, mainly in terms of depth to the top, where differences of [Formula: see text] were encountered. GPR (Ground Penetrating Radar) was also used to confirm the results obtained in a resistivity profile surveyed on a test site. Results are very encouraging, demonstrating that the resistivity imaging helped to locate and characterize mined areas, jointly with other geophysical methods. Unfortunately, true resistivity is not well resolved, because of inherent ambiguity of the inverse method used.
Print ISSN:
1083-1363
Electronic ISSN:
1943-2658
Topics:
Geosciences
Permalink