Land subsidence associated with the overexploitation of aquifers is a process that costs millions of dollars annually for the repair of affected infrastructure and buildings (Viets et al. 1979; Herrera-García et al. 2021; Kok and Costa 2021). This phenomenon is well known, and since the 1960s, the United Nations Educational, Scientific and Cultural Organization (UNESCO) has organized symposiums and working groups to study and address this problem; the current one is the "International Land Subsidence Initiative" (https://www.landsubsidence-unesco.org/). Therefore, knowing, understanding, and addressing the problem is necessary since it is a hazard that can potentially generate risk areas. Locally, state governments systematically monitor subsidence, such as the State Government of Aguascalientes (2024) or the Arizona Geological Survey (2024). Land subsidence's potential risks and dangers emphasize the urgency and importance of our research and understanding of this phenomenon.
The effects of subsidence on the surface are the formation of cracks and scour, also affecting agricultural land, industrial, infrastructure, and urban areas (Herrera-García et al. 2021). Cracks form in valleys where overexploitation of the aquifer generates a mass deficit that favors the compaction of the sedimentary fill, so the cracks track follows the trend of basement faults (Burbey 2002; Gutiérrez-Yurrita 2010; Galloway and Burbey 2011; Hernández-Marín et al. 2017; Figueroa-Miranda et al. 2018; Carreón-Freyre et al. 2019). Mitigation impacts and control of cracks have been studied for several decades (e.g. Poland 1984; Galloway et al. 1999; Galloway et al. 2008). One of the main problems is the difficulty in filling them, and although techniques are also applied to mitigate the process, such as artificial water recharge, it continues (Galloway and Burbey 2011).
Subsidence monitoring is often carried out with techniques ranging from the use of extensometers, geopositioners, precision topography, satellite images, InSAR, and Lidar, among others (Castellazzi et al. 2016; Figueroa-Miranda et al. 2018; Cigna and Tapete 2021). In this way, subsidence and fracturing are continuously monitored in sites with agricultural and industrial activities and urban areas. However, where subsidence is slow, its effects are barely perceptible.
Subsidence and crack formations can generate risk areas in the short, medium, and long term, affecting the population and their assets and causing socioeconomic and environmental losses (Herrera-García et al. 2021).
In population seats, the lack of interest may be because if a fracture does not require repair, it may be ignored; furthermore, due to their small dimensions of a few meters, they are not considered possible precursors of cracks or subsidence. Commonly, their origin is associated with the settlement of the land, the natural configuration of urbanization, the passage of vehicles, and low-quality materials and construction processes.
Escalona-Alcázar et al. (2015) proposed the hypothesis that basement faulting also influences the formation and distribution of fractures in sidewalks, streets, and walls. The tendency of fracturing that forms in urban infrastructure is subparallel to the main basement faults (Escalona-Alcázar et al. 2015, 2023; Barrios del Río 2018; Muro-Ortega et al. 2022; Sánchez-Pérez et al. 2022).
In the Las Pilas community, Zacatecas, located on the western edge of the Sierra de Zacatecas and adjacent to the overexploited Calera Aquifer, fractures in sidewalks, walls and streets were systematically measured to define their preferred orientation and its relationship with the deformation of the basement according to the methodology proposed by Escalona-Alcázar et al. (2015) and Muro-Ortega et al. (2022). No subsidence monitoring technique has yet been applied in the Las Pilas community because no subsidence has been observed.
The community of Las Pilas is in the western part of the Sierra de Zacatecas (Fig. 1) in the morphogenetic region "Erosion and pluvial accumulation" (Lugo-Hubp 1990). The principal geomorphic agent in this region is the wind, while the water erosion effect is light to moderate (Peltier 1950; Fookes et al. 1971). The Arroyo Las Pilas is the northern limit of the community (Fig. 2); it is oriented NW-SE with almost perpendicular tributaries. The water erosion is low mainly because most streams are intermittent and to a small extent (Lugo-Hubp 1990). Slopes between 6° and 15° are adjacent to the main channel and where most tributaries are formed. In the community's central and southern parts, the slopes are less than 6° and appear to be aligned with a normal fault.