Book Title: Structural Geology Applied to Fractured Aquifer Characterization

The study of fractured (hard rock) aquifers is increasingly pressing because they occupy vast areas of all continents, and the dependence on this type of aquifer for water supply is growing fast. In hard rocks, groundwater flows through void spaces that are present in fractures that form a connected network; its characterization requires knowledge of structural geology and rock mechanics. This book shows how these disciplines allow us to unveil the logic of the organization of a fracture network and help us build more realistic conceptual models.

The permeability of hard rocks is related to fracture connectivity and aperture, and both are constrained by a number of structural geology and rock mechanics factors. In this way, this book brings insight to questions such as: How does the geometry of different fracture types influence connectivity and aperture? How do tectonic regimes (compressive, extensional and strike slip) influence the general configuration of a fracture network? How does the brittle deformation history affect the architecture and connectivity of the fracture system? How does the current in situ stress field affects the aperture of fractures?

Different rock types, such as sedimentary, volcanic, metamorphic, and intrusive rocks have their own typical discontinuities and pre-existent structures. This influences how the in-situ stresses develop different fracture network architectures. Conceptual models of fracture networks, their connectivity, and preferential groundwater flow pathways, in different geological settings, are presented and explained.

Due to the heterogeneous distribution of the fracture porosity, hard rock aquifers pose many scientific and methodological challenges. One way to overcome these difficulties is to conduct detailed fracture surveys, on large rock exposures, when possible, and to apply structural geology and rock mechanics fundamentals to the collected data. Such work gradually builds knowledge on the organizational logic of fracture systems and how it affects groundwater flow.