A 3D Electric Resistivity Tomography Carried Out to Characterize the Subsoil (Fractures and Subsidence) Beneath a Reside

A residential complex named La Concordia suffers of strong damage in their structure due to fractures and subsidence within the subsoil. This complex consists of six four storey buildings in an area of 33x80 m2, located towards the eastern portion of Mexico City (Iztacalco County). An Electric Resistivity Tomography (ERT) was carried out to characterize the subsoil beneath the buildings. Since there is no possible to deploy the geophysical transects through the edifices, a special array type (horseshoe geometry) ‘L’ employing a Wenner-Schlumberger technique was performed to bound the affected site. In addition, equatorial-dipole and minimum-coupling arrays were carried out to fully ‘illuminate’ beneath the constructions. The computed depth of investigation reached was 10 m. Several computed resistivity anomalies were associated to a fracturing pattern that possesses a preferential NW-SE direction. The main fracture inferred seems to extend beyond the limits of the surveyed area. It is very likely that fractures have been produced due to the poorly consolidated clays that cover most of the central part of the Valley of Mexico; the intense water extraction, that form ‘voids’ in the subsoil causing subsidence effects and finally the existence of regional faults to greater extent that control these shallow features.