Structural pattern of subsidence in an urban area of the southeastern Mexico Basin inferred from electrical resistivity tomography

Abstract

Most of the urban area in the Basin of Mexico is underlain by sediments of the former lakes of Chalco, Xochimilco, Mexico, Texcoco, Xaltocan and Zumpango, which offer poor foundation conditions for buildings. Water supply requirements have led to overexploitation of the aquifers, and the increased exacerbating the rate of subsidence causes housing units and roads to deteriorate. In order to understand the location of the cracking and fracturing pattern, a geophysical study using electrical resistivity tomography was performed in a populated zone of the southeastern Mexico Basin. Five two–dimensional resistivity profiles were acquired. Discontinuities in the resistive horizon (probably in extrusive igneous material) were identified. The discontinuities could be related to cracks and fractures observed on the surface which had previously damaged housing construction.
A three–dimensional resistivity profile was also obtained. The 3D image confirms results obtained from 2D models, and shows a resistive layer with lateral discontinuities. The inferred fracture pattern has a preferential NW–SE direction, related to the a subsidence process produced by overexploitation of the aquifer in the area.