Geological risk assessment by a fracture measurement procedure in an urban area of Zacatecas, Mexico

Geological hazards represent medium- and long-term risks, when they affect urban infrastructure and residential areas as they become a source of danger for the population. In 2000, fracture formation on a couple of streets was reported in the town of Villa Hidalgo, Zacatecas. The first official fracturing report was issued 11 years later and it stated that the fractures were associated with an N–S fault. This paper proposes a hypothesis on the origin of the fractures due to slow land subsidence based on systematic measurement of fractures in frontages, streets, and sidewalks in the locality. The data measured in each fracture were: azimuth, dip, dip direction, length, thickness, azimuth of the extension axis, and fracture density. The fracturing risk and hazard analysis integrates the field data together with the edaphology, geology, slope, population, infrastructure, and services. The risk and hazard range from “medium” to “very high” in a belt oriented N–S of 200 m wide at 100 m to the west of La Ballena-Villa Hidalgo fault, at the eastern edge of Villa Hidalgo graben. The risk distribution area is probably associated with the steplike structure of the basement. Aquifer overexploitation, deficiencies in construction procedures and the geomorphic process also seem to have facilitated the fracture formation.