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Considerable progress has been made recently in quantifying geometrical and physical properties of fault surfaces and adjacent fractured and granulated damage zones in active faulting environments. There has also been significant progress in developing rheologies and computational frameworks that can model the dynamics of fault zone processes. This volume provides state-of-the-art theoretical and observational results on the mechanics, structure and evolution of fault zones. Subjects discussed include damage rheologies, development of instabilities, fracture and friction, dynamic rupture experiments, and analyses of earthquake and fault zone data.
Fault zones, hosted in fractured carbonate reservoirs, can behave as either high porosity and permeability conduits, favoring the migration of fluids; or, conversely, as low porosity and permeability barriers, retarding fluid flow, due to the presence of fine-grained fault gouges (Agosta and Aydin, 2006, Agosta and Kirschner, 2003). Due to these reasons, fault zones can have great economical importance for the hydrocarbon industry. Furthermore, within fault zones, the cyclic accumulation and sudden release of trapped, high pressure fluids can trigger earthquakes and aftershocks (Miller et al. 2004). In this project, we referred to the classical fault zone architecture models defined by Sibson (1977) and Chester et al. (1993), in which faults are built up of a fault core (where most of the displacement is localised), a damage zone (containing fractured host rocks) and the protolith (the unfractured host rock). Faults, with displacements ranging from cm- to km-scale have been studied within two study areas, Flamborough Head, UK and the Gubbio fault in the Northern Apennines, Italy. Flamborough Head is a peninsula in East Yorkshire, which represents analogues for hydrocarbon rich, fractured North Sea chalk reservoirs; whereas the Gubbio fault is a regional scale, seismically active normal fault, characterized by complex fault zone architectures, cutting through different types of carbonates. At both study areas, field-based, outcrop-scale structural observations were completed in order to explore the internal architecture and infer the fluid transmissibility of the fault zones. Additionally, microscale structural observations were made using representative thin sections, collected from the different fault zone domains of the studied fault zones. Qualitative structural observations were complemented with quantitative analyses to study the variation of fracture and vein density and connectivity patterns across the fault zones, which were later used as a proxy for fluid transmissibility. These analyses included established 1D (transects) and 2D (image analysis) methods and a newly developed workflow for the modelling of fracture networks in 3D, based on LiDAR data. 3D modelling of fracture networks was developed using different fracture height/length aspect ratios. The quantitative comparison of different aspect ratio 3D models with established 1D and 2D results, by using misfit graphs, enabled to validate the different 3D models and to estimate the mean aspect ratio of fractures within the fault zones. Qualitative and quantitative results were integrated in conceptual fault zone architecture and fluid flow models. At Flamborough Head small (cm-scale) and larger (up to 20 m) displacement normal faults were studied in two different types of chalks: one characterized by cm-scale interlayered marl horizons and another one, absent of it. Within the marl-free host rock, in the fault zones of both the small and the large displacement faults, fluid assisted deformation features, such as veins, are often observed. On the contrary, in marl-rich units, fluid assisted deformation features are absent, while fractures filled with intruded marl from the interlayered horizons are common. This suggests that the occurrence of fluid flow in this lithology is primarily controlled by the protolith. 1D quantitative analysis at Flamborough Head showed that, as also predicted by classical fault zone models, vein density progressively increases in the damage zones of faults moving from the protolith towards the fault core. 2D quantitative analysis showed that fracture connectivity remains as low as background values in the outer parts of the damage zones, whereas it increases rapidly in the inner parts. By comparing the fracture density and connectivity patterns measured from different aspect ratio 3D models with results measured from 1D and 2D analyses showed that the most realistic model is the 1/5 fracture aspect ratio one. The Gubbio fault cuts through a carbonatic multilayer containing carbonates with different marl content. In the Marne a Fucoidi formation marl is homogenously distributed, while in the overlying Scaglia Group marl is absent. Within the damage zone, hosted in the Marne a Fucoidi formation, fluid assisted deformation features are rare and are only present in the damage zones of subsidiary faults that entirely cut through the formation, linking the under and overlying marl free carbonates. On the contrary, within the damage zone, hosted in the Scaglia Group, fluid assisted deformation features are common, especially close to the fault core of the Gubbio fault and in the damage zone of subsidiary faults. Similarly to Flamborough Head, this suggests that the occurrence of fluid flow is primarily controlled by the nature of the protolith. As predicted by classical fault zone models, 1D quantitative analysis across the Gubbio fault showed that vein density increases in the damage zone moving from the protolith towards the fault core. Similarly to results from Flamborough Head, 2D quantitative analysis showed that fracture connectivity is low in the outer parts of the damage zones, but increases rapidly within the inner parts, and the comparison of 3D models with 1D and 2D results showed that the most realistic model is the 1/5 aspect ratio one. The conceptual fluid flow models, built for the study areas, highlights: a) the importance of different marl content host rocks controlling the initiation of fluid flow; b) the development of smaller and larger displacement normal faults and the effects of their displacements on fluid transmissibility; c) the effects of fault damage zones, positioned in an overlapping geometry, resulting in the development high and low fracture connectivity subdomains and fracture corridors; d) the differences in the relative variation of fracture/vein density and connectivity throughout the damage zone compared to background values; e) the fluid transmissibility of the different fault rocks, located within different subdomains of the fault core and f) the anisotropy of fluid transmissibility in the fault core.
The spatial patterns of bimaterial interfaces along the Parkfield section of the San Andreas Fault (SAF) and central section of the Calaveras Fault are systematically investigated with large data sets of near-fault waveforms. Different from the usage of direct P and S waves in traditional tomographic studies, a particular seismic phase named fault zone head wave (FZHW) is used to image the bimaterial fault interfaces. The results show clear variations of seismic velocities contrast both along-strike and along-depth directions in both regions, which is in general consistent with local geological setting at surface and existing 3D tomography results. In the Parkfield section of SAF, the result of velocity contrast is used to test the relationship between preferred rupture directions of M6 Parkfield earthquakes and bimaterial interface. Strong velocity contrast (~5-10%) near Middle Mountain (MM) could control the rupture directions of nearby earthquakes to SE, such as the case for 1966 M6 Parkfield earthquake. In comparison, weak velocity contrast (~0-2%) near the epicenter of the 2004 Parkfield M6 earthquake (i.e., Gold Hill) probably has no influence on controlling its rupture direction, which is consistent with the bilateral rupture of the 2004 Parkfield earthquake. In the central Calaveras Fault, a detailed analysis of the moveout between FZHWs and direct P waves revealed the existence of a complicated fault structure with velocity contrast increasing from NW to SE of station CCO. The high velocity contrast SE of station CCO could be caused by a low-velocity zone SE of station CCO. : The spatio-temporal variations of seismic velocity around the central Calaveras Fault and its nearby region are investigated based on the waveform analysis of 333 repeating clusters following the 1984 ML6.2 Morgan Hill earthquake. Clear reduction of seismic velocity is shown for all repeating clusters immediately after the mainshock, followed by a logarithmic recovery. The coseismic change mostly occurs at shallow layers (top few hundred meters) for the region away from the rupture area of the mainshock, but extends much deeper around the rupture zone of the Morgan Hill earthquake. The estimated depth of the damage zone is up to 6 km in the fault based on the repeating clusters directly beneath station CCO.
The destructive force of earthquakes has stimulated human inquiry since ancient times, yet the scientific study of earthquakes is a surprisingly recent endeavor. Instrumental recordings of earthquakes were not made until the second half of the 19th century, and the primary mechanism for generating seismic waves was not identified until the beginning of the 20th century. From this recent start, a range of laboratory, field, and theoretical investigations have developed into a vigorous new discipline: the science of earthquakes. As a basic science, it provides a comprehensive understanding of earthquake behavior and related phenomena in the Earth and other terrestrial planets. As an applied science, it provides a knowledge base of great practical value for a global society whose infrastructure is built on the Earth's active crust. This book describes the growth and origins of earthquake science and identifies research and data collection efforts that will strengthen the scientific and social contributions of this exciting new discipline.
This open access book gathers authoritative contributions concerning multiscale problems in biomechanics, geomechanics, materials science and tribology. It is written in memory of Sergey Grigorievich Psakhie to feature various aspects of his multifaceted research interests, ranging from theoretical physics, computer modeling of materials and material characterization at the atomic scale, to applications in space industry, medicine and geotectonics, and including organizational, psychological and philosophical aspects of scientific research and teaching as well. This book covers new advances relating to orthopedic implants, concerning the physiological, tribological and materials aspects of their behavior; medical and geological applications of permeable fluid-saturated materials; earthquake dynamics together with aspects relating to their managed and gentle release; lubrication, wear and material transfer in natural and artificial joints; material research in manufacturing processes; hard-soft matter interaction, including adhesive and capillary effects; using nanostructures for influencing living cells and for cancer treatment; manufacturing of surfaces with desired properties; self-organization of hierarchical structures during plastic deformation and thermal treatment; mechanics of composites and coatings; and many more. Covering established knowledge as well as new models and methods, this book provides readers with a comprehensive overview of the field, yet also with extensive details on each single topic.
Scientific understanding of fluid flow in rock fracturesâ€"a process underlying contemporary earth science problems from the search for petroleum to the controversy over nuclear waste storageâ€"has grown significantly in the past 20 years. This volume presents a comprehensive report on the state of the field, with an interdisciplinary viewpoint, case studies of fracture sites, illustrations, conclusions, and research recommendations. The book addresses these questions: How can fractures that are significant hydraulic conductors be identified, located, and characterized? How do flow and transport occur in fracture systems? How can changes in fracture systems be predicted and controlled? Among other topics, the committee provides a geomechanical understanding of fracture formation, reviews methods for detecting subsurface fractures, and looks at the use of hydraulic and tracer tests to investigate fluid flow. The volume examines the state of conceptual and mathematical modeling, and it provides a useful framework for understanding the complexity of fracture changes that occur during fluid pumping and other engineering practices. With a practical and multidisciplinary outlook, this volume will be welcomed by geologists, petroleum geologists, geoengineers, geophysicists, hydrologists, researchers, educators and students in these fields, and public officials involved in geological projects.
Paleoseismology has become an important component of seismic risk analysis, which is mandated for nuclear power plants, dams, waste repositories, and other critical structures. This book is the first in the English language to be devoted solely to paleoseismology. It summarizes the development of the field from the 1960s to the present, encompassing material that is currently widely dispersed in journal articles. Includes a comprehensive review of the techniques currently used in paleoseismology Emphasizes practical methods of data collection and field studies Covers interpretation of field data based on current theory concerning fault segmentation and recurrence cycles Contains more than 170 line drawings and 50 photographs of paleoseismic phenomena
Atlas of Structural Geology features a broad and inclusive range of high-quality meso- and micro-scale full-color photographs, descriptions, and captions related to the deformation of rocks and geologic structures. It is a multi-contributed, comprehensive reference that includes submissions from many of the world’s leading structural geologists, making it the most thorough and comprehensive reference available to the scientific community. All types of structures are featured, including structures related to ductile and brittle shear zones, sigma- and delta-structures, mineral fish, duplexes and trapezoids, shear related folds, and flanking structures in meso- and micro-scales. A stunning collection of the world’s most beautiful and arresting geologic structures, the Atlas of Structural Geology is the ideal aid in the retention of key concepts in geology. Presents more than 250 top-quality, full-color photographs contributed by the world’s most respected structural geologists Features a broad range of morphological variations of geologic structures, making it the most up-to-date and inclusive reference of its kind Edited by a structural geologist with 14 years of experience in related research and instruction Aids researchers in developing mathematical and analogue models on the peculiarity and uniqueness of the world’s most iconic structures