Vásquez Serrano et al. RMCG | v. 36 | núm. 1 | www.rmcg.unam.mx | DOI: http://dx.de fracturas geológicas en el pozo Agrícola Oriental 2C, Ciudad de México y su relación con fallas mayores: Revista Mexicana de Ciencias Geológicas, v. 36, núm. 1, p. 38-53.
RESUMENEn años recientes, en la Ciudad de México se han realizado varios pozos exploratorios de hasta 2000 m de profundidad, con el fin de encontrar acuíferos que ayuden a disminuir el desabasto de agua potable para el área metropolitana. En particular, en el pozo Agrícola Oriental 2C, perforado en la Alcaldía de Iztacalco, se recuperaron varios núcleos, uno de los cuales mide 9 m, ubicado entre 1550 y 1559 m de profundidad, cercano al contacto entre rocas calcáreas del Cretácico y rocas volcánicas del Oligoceno, a ~1560 m de profundidad. El núcleo muestra que las rocas volcánicas se encuentran afectadas por una cantidad importante de fracturas, las cuales pueden ser divididas en dos familias con base en su relleno y relaciones de corte (F1 y F2). Las fracturas más jóvenes (F2) se relacionan con una falla, llamada informalmente en este trabajo falla Agrícola Oriental, que pone en contacto rocas sedimentarias y volcánicas.Palabras clave: fractura geológica; análisis fractal; arreglo de fracturas; intensidad de fracturas; falla Agrícola Oriental.
ABSTRACTIn the last years several exploratory wells have been drilled in Mexico City down to 2000 m depth, with the aim to explore deep aquifers to cover the water deficiency in the metropolitan area. In particular, in the Agricola Oriental 2C well, located in the Iztacalco municipality, several cores were recovered; one of them is 9 m long, located between 1550 and 1559 m depth. This core is situated close to the contact between an Oligocene volcanic unit and a Cretaceous limestone at ~1560 m depth. The study core shows that the volcanic rocks are affected by an important number of fractures, which can be divided into two families according to their intersection relationships and fill material (F1 and F2). The younger fractures (F2) are related with a fault, informally named here as Agricola Oriental fault, which sets in tectonic contact the sedimentary and the volcanic rocks.The fractures were characterized through a detailed analysis of their number, geometry and spatial arrangement, using the scan line method and taking into account both families of fractures. These variables were expressed such as fracture intensity, box and correlation fractal dimensions, Lyapunov exponent, variation coefficient, and cumulative frequency exponent. Our results show that the spacing between fractures and the aperture follow a power law in a log-log graph of the cumulative frequency analysis that results in a fractal behavior. The pattern values showed in the fracture intensity, fractal dimension, Lyapunov exponent, and aperture cumulative frequency exponent progressively diminish as the distance to the fault increases. In turn, the coefficients of variation and spacing cumulative frequency exponent have a different pattern: Análisis de...