Efectos de las fallas asociadas a sobreexplotación de acuíferos y la presencia de fallas potencialmente sísmicas en Morelia, Michoacán, México

Abstract

During the last two decades differential ground subsidence has affected many urban centers in Mexico. This process has been commonly related only to over-exploitation of subsurface water resources. In this work we discuss general problems of geological faulting in urban centers and we present the description of faults in Morelia, Michoacán state. In Morelia, differential ground subsidence started in 1983 when ground gashes with very small displacement started to form. Subsequently these gashes evolved to form a network of normal faults that accumulated up to 100 m displacement. These faults trend between N30°E and N80°E and coincide with the orientation of regional tectonic faulting affecting the basin basement. The vertical displacement of these faults is 4 to 6 cm per year. The deformation zone affected by a single fault, estimated by the damage caused to man-made structures, depends on the geometry of the fault and can be as wide as 5 m. Since 1983 faults affected a significant number of buildings, some of them to such an extend, that they had to be demolished. Other man-made structures such as streets, drainage and water pipes were also damaged. Two of the faults recognized in Morelia are of clear tectonic origin and we considere them potentially seismic. They belong to the Morelia-Acambay fault system, which experienced historic earthquakes. Constant landslides are associated with one of them. Fault displacements in Morelia and other cities in Mexico (Celaya, Queretaro, Salamanca, Irapuato, Aguascalientes etc.) have a strong impact on the society, as they affect industrial parks, hospitals, underdeveloped districts and residential zones.