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Station 2 with borehole C-10 intersecting the Shear Zone fault and borehole C-11 intersecting the Woolsey member at depth. a Map of the northeast edge of SSFL with well locations marked. b Bent shale (green line boundary) juxtaposed to sandstone (black line boundary). c Interpreted image from the OPTV showing fractures, sheared fractures, veins, and slip surfaces. d Schematic 3D block diagram showing the SZF at this location. The well traces (turquoise) and their intersection with the Woolsey member and the Shear Zone fault are shown. Approximate locations of figure parts b-c also are marked
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Faults influence groundwater flow paths. The transport of groundwater contaminants within the faulted sandstones and shales of Chatsworth Formation exposed in southern California, USA, have been investigated. Structural and hydrogeological data are combined to interpret the hydraulic-head drop measured across a fault with tens of meters of oblique-...
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... SZF were delineated at two stations (Nos. 1 and 2) about 2 km apart from each other (see Fig. 1 for the locations). Station 1 encompasses an outcrop along the southern portion of the fault (Figs. 5a and 6), while Station 2 includes a borehole interpreted as intersecting the central portion of the fault and one of the shale units offset at depth ( Fig. 7c-d). The former has the advantage of showing a transversal section of the fault zone in a large surface, whereas the latter reveals an image of a portion of the fault zone at the subsurface thereby avoiding effects of weathering and the related cover. Fig. 6 Photographs of different portions of the Shear Zone fault at Station 1. a Fault ...
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... station includes the borehole C-10 (see Fig. 7a for location), which reaches a depth of approximately 194 m. Previous investigators (MWH 2009) interpreted that near its bottom (at about 189 m) this borehole intersects the fault zone (Fig. 7d). Geophysical data (i.e., gamma-ray, electric resistiv- ity, and optical televiewer) were available for this well. Images from the optical ...
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... station includes the borehole C-10 (see Fig. 7a for location), which reaches a depth of approximately 194 m. Previous investigators (MWH 2009) interpreted that near its bottom (at about 189 m) this borehole intersects the fault zone (Fig. 7d). Geophysical data (i.e., gamma-ray, electric resistiv- ity, and optical televiewer) were available for this well. Images from the optical televiewer (OPTV) were interpreted and integrated with ex-situ characterization of the last 6 m of the recovered rock core. Figure 7c shows the interpreted OPTV image where fractures (including ...
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... from the optical televiewer (OPTV) were interpreted and integrated with ex-situ characterization of the last 6 m of the recovered rock core. Figure 7c shows the interpreted OPTV image where fractures (including sheared fractures or faults), veins, and slip surfaces are identified and highlighted with different colors. At the bottom of the image (189.2 m depth) a slip surface juxtaposes fractured sandstones against highly deformed shale fault rock. ...
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... or faults), veins, and slip surfaces are identified and highlighted with different colors. At the bottom of the image (189.2 m depth) a slip surface juxtaposes fractured sandstones against highly deformed shale fault rock. This slip surface, which dips 75° toward SE, is here interpreted as the southeastern boundary of the Shear Zone fault (Fig. 7d). About 4 m of shale fault rock were captured in the core. The shale fault rock was highly folded and brecciated with a locally complex cataclastic texture. A semi-quantitative x-ray diffraction analysis was performed on two representative samples of the shale fault rock to identify their mineralogical composi- tion. Both samples ...
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... very small amount (3-5 %) of quartz also was found in one of the samples. Similar to the observations at Station 1, the shales show a plastic behavior in contrast to the brittle behavior of the sandstones. One image taken at the depth where the fault zone boundary was inferred shows a highly bent shale strata juxtaposed against a sandstone sliver (Fig. 7b). The architecture of the SZF in the subsurface, consisting of plastic shale bent against fractured sandstones and shale-rich fault rock, resembles that docu- mented at the surface at Station 1. Therefore, it is suggested that the mechanism of incorporating shale into the fault zone is the same in both portions of the fault. This ...
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... SZF in the subsurface, consisting of plastic shale bent against fractured sandstones and shale-rich fault rock, resembles that docu- mented at the surface at Station 1. Therefore, it is suggested that the mechanism of incorporating shale into the fault zone is the same in both portions of the fault. This station also has a borehole, C-11, (see Fig. 7a for location) intersecting what is inferred to be the fine-grained (∼45 % of the bulk composition) Woolsey member at around 185 m depth, thereby revealing the throw of the Woolsey member. On the southeast side of the fault zone the Woolsey member crops out 230 m northeast of borehole C-11, suggesting an apparent vertical separation ...
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... intersecting what is inferred to be the fine-grained (∼45 % of the bulk composition) Woolsey member at around 185 m depth, thereby revealing the throw of the Woolsey member. On the southeast side of the fault zone the Woolsey member crops out 230 m northeast of borehole C-11, suggesting an apparent vertical separation along the SZF of about 170 m (Fig. ...
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Citations
... procesos de deformación asociados con fallamiento (Wilson et al., 2003), la propagación de la rotura durante un sismo (Choi et al., 2012) y la permeabilidad en la corteza (Caine et al., 1996;Kim y Sanderson, 2010). Este último campo es fundamental en aplicaciones asociadas con el estudio de acuíferos, yacimiento de hidrocarburos y minerales, y almacenamiento de CO 2 (Dockrill y Shipton, 2010;Rotevatn y Fossen, 2011;Cilona et al., 2015). A pesar de los avances en el conocimiento de las zonas de daño, aún se desconoce con detalle las variaciones en la cantidad, arreglo, distribución y conectividad de las fracturas, más aún si las fallas tienen una historia compleja de deformación, que implica varios episodios de actividad con distinta cinemática. ...
We analyze the number, length, distribution, and fracture
connectivity associated with the San Miguel de Allende fault (FSMA). For
this analysis, we estimated parameters such as density, box dimension, fragmentation dimension, and connectivity. Our results show that
within the damage zone of the FSMA, three fracture generation events
occurred. The first (D1) is associated with the Late Cretaceous-Paleogene
orogenic event and formed subvertical calcite veins with NE-SW and
NW-SE orientations. The other two events (D2 and D3) are related to
the Cenozoic activity of the FSMA in the Oligocene-Miocene, generating
subvertical open fractures, and gypsum and amorphous quartz veins,
with NE-SW, NW-SE, and N-S preferential orientations. Fractures in
the damage zone are mainly extensional, hybrid, and shear. They have
an average density of 3000 fractures/m2, a box dimension between 1.31
and 1.84, and a fragmentation dimension between 1.86 and 3.81. Its
connectivity exceeds the threshold of 2 connections per fracture (C=2) in
the ternary diagram of nodes I, Y, and X, which suggests good connectivity
between the fractures, while the parameter Fm, which characterizes the
architecture of the fault zone and permeability, shows that the damage
zone of the FSM acts as a conduit. Based on our results, we suggest that
fracture reactivation is an effective mechanism for strain accommodation
and increases the number, connectivity, and permeability of fractures in
the damage zones.
... Exploration data and actual underground exposure data show that the faults in the mine field are affected by development characteristics such as fault mechanical properties, lithology of upper and lower walls, and fault scale, 26 which makes the water content and water conductivity different in different sections. Affected by changes in hydrogeological conditions in various areas, the lithologic docking relationship and stress state distribution of the same fault are different in different areas, so the water content and conductivity of the same fault in different directions and different parts may change; that is, local water conduction and local water resistance or a fault exposed for the first time will lead to delayed water conduction during mining disturbances. ...
Mine water disasters are one of the main disasters threatening safe mine operations. If a fault becomes a water guide channel, it often causes serious water inrush accidents in mining. Therefore, accurate evaluation of fault hydraulic conductivity is very important for the prediction and prevention of mine water disasters. To prevent and control mine water disasters and ensure safe mining of coal seams in the presence of faults, this paper takes the F22 fault in the Jinqiao Coal Mine as an example; proposes three highly applicable fault water conductivity evaluation methods based on analysis of water-rock stress, difference analysis of hydrochemical characteristics, and difference analysis of water pressures for the same aquifer on both sides of the fault; and comprehensively analyzes and evaluates the water conductivity of the F22 fault. The results are as follows: the cross-sectional pressure of the fault is greater than the aquifer water pressure and the plastic deformation strength of mudstone combined. The hydrochemical characteristics of the three-ash aquifers on both sides of the fault are obviously different. The water in the three-ash aquifer on one side of the fault has been drained for a long time, while the water pressure on the other side of the fault has not changed significantly. Based on a comprehensive analysis, it is judged that the F22 fault is not water-conducting. The evaluation results are consistent with geophysical explorations and the actual mine roadway exposure, which verifies the feasibility and rationality of the fault water conductivity evaluation method described above.
... These structures may also form conduits to groundwater flow or complex conduit-barrier systems (Caine et al., 1996). Geologic structures that act as hydrogeologic barriers can form important controls on groundwater flow (Bense et al., 2003;Cilona et al., 2015), chemistry (Gumm et al., 2016;Mayer et al., 2007), groundwater age (Castro & Goblet, 2005;Marshall et al., 2020), discharge processes (Bense & Kooi, 2004;Gleeson & Novakowski, 2009), and drawdown (Hadley et al., 2019;Marshall et al., 2019). Locating and characterizing hydrogeologic barriers can be difficult and costly. ...
Hydrogeological barriers can significantly impact groundwater model predictions. They are, however, often excluded from, or misrepresented in, groundwater models if their presence is unknown or their properties are poorly constrained. Here we show that sharp barriers can be included in groundwater model inversion, even where their presence is uncertain. We describe an approach utilizing ‘phantom structures’—randomly located, linear groups of model cells assigned a unique hydraulic conductivity value—to improve identifiability of barriers. Algorithmic parameter estimation using PEST is implemented to determine model structures that best match the hydraulic head and groundwater age observation data from a hypothetical aquifer. Our results show that for a series of case studies, this method was successful in inferring the appropriate location and properties of hydrogeological barriers, when that barrier was not aligned with the dominant flow direction. We compare these results to model inversion using traditional pilot points. The phantom structures approach shows promise in identifying hydrogeological structures and in reproducing groundwater flow across a model domain. Our results demonstrate that the geometric properties of geological structures can remain flexible in a model inversion. This is a step towards reducing conceptual model uncertainty where the presence and properties of hydrogeologic barriers are undefined.
... Thus, for example, along-fault flow may be detected from the upward flow of warmer (Bense et al., 2008) or older (e.g., Castro and Goblet, 2005;Raiber et al., 2015;Gumm et al., 2016;Batlle-Aguilar et al., 2017) water into shallow aquifers, or the presence of radioisotopes produced within the fault itself (e.g., radon; Pereira et al., 2010). Several papers have described hydraulic head changes across faults, which are generally taken to indicate the role of these faults as barriers to cross-fault flow (e. g., Haneberg, 1995;Cilona et al., 2015;Delinom, 2009;Bense et al., 2003, Bense et al., 2008. Recently, Marshall et al. (2020) showed that the diversion of groundwater flow around faults that are barriers to flow may result in increases in groundwater age downstream of such structures. ...
Faults can act as barriers to cross-fault flow, conduits to along-fault flow or both. Groundwater age inferred from hydrochemical data is one of the few tools that can estimate both barrier and conduit behaviour of the fault and associated fault damage zone. Conduit behaviour has been previously inferred from the existence of young water in deep aquifers or old water in shallow aquifers. While the ability of groundwater age to estimate the barrier behaviour of faults has been illustrated theoretically, it has not yet been observed in the field. Here, conceptual models of hydraulic head and groundwater age perpendicular to and across faults are discussed in terms of the resistance to flow across the fault (fault width divided by cross-fault hydraulic conductivity), the resistance to flow around the fault (fault length divided by aquifer hydraulic conductivity) and the recharge regime. To examine these conceptual models, field measurements of hydraulic head, ¹⁴C, chloride and electrical conductivity in groundwater are presented along transects across three contrasting fault systems. Large cross-fault head and age gradients are apparent at two of the three sites. At one of these sites, where regional flow is mostly parallel to the fault, ¹⁴C age and chloride data are used to estimate the rate of cross-fault flow. At the third site, there may not be a barrier to cross-fault flow, as there is no clear increase in either head or age gradient. The studies illustrate the importance of high data density to characterise fault zones, particularly for groundwater age which will vary both with depth and horizontal location along a transect. Although our data does not indicate conduit behaviour, such behaviour has been suggested based on groundwater chemistry at other locations along the fault strike at two of the sites.
... Caine et al., 1996;Faulkner et al., 2003;Kim and Sanderson, 2010), en particulier pour le piège et les migrations des ressources en eau (e.g. Bense et al., 2008;Cilona et al., 2015), en hydrocarbures (e.g. Rotevatn and Fossen, 2011), pour la séquestration du CO2 (e.g. ...
L’étude des failles affectant la croûte supérieure suscite un intérêt particulier pour la modélisation de leur impact sur l’écoulement des fluides et le comportement mécanique de la croûte terrestre. Les zones d’endommagements de failles sont d’importantes structures aux multiples implications pour les problématiques de gestions des ressources et de risque/aléa sismiques. Cette thèse a pour objectif de déterminer la distribution de l’endommagement autour des failles, comprendre sa croissance et étudier son impact sur la loi d’échelle Déplacement – Epaisseur d’endommagement (D-T). Pour répondre à cette problématique, deux approches complémentaires sont développées : des études tectoniques d’exemples naturels et des modélisations analogiques de failles normales. Ce manuscrit présente de nouvelles cartographies de l’endommagement, une première loi D-T pour les failles dans des roches carbonatées, ainsi que les premières expériences de modélisation analogique dédiées à l’étude de l’endommagement. Les résultats montrent que la distribution de l’endommagement autour des failles est hétérogène et asymétrique, principalement influencée parles nombreuses interactions de failles lors de leur croissance (segmentation, failles conjuguées). Une loi D-T spécifique à l’endommagement de type wall damage est établie, qui montre une corrélation normale entre D et T pour les failles de rejet inférieur à 100 m et confirme l’existence d’un seuil d’épaisseur d’endommagement au-delà de 100 m de rejet. Pour expliquer cette loi nous proposons un modèle de croissance de zone d’endommagement contrôlée par les processus d’interaction et de coalescence de la segmentation précoce. Les expériences de modélisations analogiques ont permis de décrire deux nouveaux types d’endommagement (graben damage et dip-change link damage), et d’identifier unetransition de mode de déformation, depuis un cisaillement dilatant segmenté vers un cisaillement compactant localisé dans les zones de failles. Elles démontrent également que l’initiation de la segmentation, la sélection de l’activité des segments, leurs interactions et leurs coalescences sont des processus essentiels contrôlant le développement des zones d’endommagement et la loi D-T. Nous proposons que l’épaisseur de l’unité fragile contenant les failles est un paramètre principal du contrôle de l’évolution de la segmentation, de la localisation de la déformation et donc du seuil d’épaisseur d’endommagement observé.
... Other studies have shown that fractional flow can be developed in some 2D heterogeneous transmissivity fields, such as long-range correlated media (e.g., Walker et al., 2006;de Dreuzy and Davy, 2007). Comparing an analogous problem for heat transfer in a linear system (Carslaw and Jaeger, 1959, p. 412-415), Doe (1991) also suggested that non-integral MWH, 2007;Cilona et al., 2015Cilona et al., , 2016. b) Configuration of observation wells analyzed and distances investigated. ...
... The area is characterized by a semi-arid climate with a mean recharge of 19 mm per year (Manna et al., 2016). The Upper Cretaceous Chatworth Formation represents the main stratigraphic unit exposed at the site and consists of a composite turbidite sequence (Link et al., 1984) characterized by a typical bedding strike of N • 70E and dip of approximately 25-35 • NW (MWH, 2007;Cilona et al., 2015). The Chatworth Formation is primarily sandstones, referred to as mostly coarse-grained units, interbedded with shales and siltstones, referred to as fine-grained units (MWH, 2007;Cilona et al., 2015;Cilona et al., 2016). ...
... The Upper Cretaceous Chatworth Formation represents the main stratigraphic unit exposed at the site and consists of a composite turbidite sequence (Link et al., 1984) characterized by a typical bedding strike of N • 70E and dip of approximately 25-35 • NW (MWH, 2007;Cilona et al., 2015). The Chatworth Formation is primarily sandstones, referred to as mostly coarse-grained units, interbedded with shales and siltstones, referred to as fine-grained units (MWH, 2007;Cilona et al., 2015;Cilona et al., 2016). ...
A long duration pumping test conducted over 151 days in a fractured sandstone and shale formation displays a nonstandard drawdown response and anomalous pressure diffusion, which cannot be properly interpreted using existing frameworks (e.g., homogeneous, double porosity, boundary conditions, and fractal models). An alternative framework with simple geometry and more complex hydraulic properties is thus proposed to interpret such kind of drawdown responses. The analytical development allows first to demonstrate all scaling relations in this interpretation framework. Then, and most importantly, the multi-scale hydraulic test provides consistent scalings of transmissivity, T, to storativity, S, over distances ranging from 83 to 383 m in a faulted area. Drawdown analysis in several monitoring wells shows persistent decrease of transmissivity in highly channelized fracture flow structures. In one structure, the cubic dependency of transmissivity to storativity identifies a well-defined fault and also demonstrates the validity of Poiseuille flow at a scale rarely investigated. In the other structure, the linear dependency of transmissivity to storativity indicates that the flow-bearing structure is the surrounding fracture network. Well-designed pumping tests combined with scaling analysis driven by geological evidence thus provide essential information on flow-bearing structures for site characterization and modeling tasks. At least for moderate to low permeable fractured rocks, the scaling of transmissivity to storativity appears to be more informative than any separate interpretation of hydraulic property scaling exponents.
... the Santa Susana Field Laboratory (SSFL) located in Southern California. This site consists of a highly fractured and faulted formation of massive sandstone, inter-bedded with shales and siltstones (Cilona et al., 2015;Cilona et al., 2016). Slug tests were conducted in 1.5 m length intervals in the open holes (r w = 0.0635 m) isolated by straddlepacker equipment (r c = 0.0159 m) using air pressure to initiate the slug test (Quinn et al., 2012). ...
Slug tests are one of the most common field methods for estimating local hydraulic conductivity, for fast and low-cost characterization of aquifer heterogeneity. In highly permeable zones, underdamped responses, identified by oscillations of the water level, are generally observed. Several analytical solutions have been developed for modeling underdamped slug test responses. Interpreting these tests in fractured rocks can be challenging due to system complexity, which ultimately raises questions about the appropriate model for interpreting a given dataset. In order to obtain insights on this fundamental problem for slug test analyses in fractured rocks, a complete evaluation on three transient solutions for linear, radial and spherical flow configuration extended to include inertial and wellbore skin effects in a fully penetrating well is proposed. A first comparison between these transient solutions and the classical steady-state model shows that, in some cases, the latter may underestimate hydraulic conductivity. Next, parameter sensitivity and uncertainty analyses were conducted on each solution to evaluate the classical problem of non-uniqueness between models and parameters. As expected, the results from sensitivity analysis show that the hydraulic conductivity parameter is the most sensitive regardless of model configuration. For specific storage, sensitivity is important for the linear model, moderate for the radial model and negligible for the spherical model. For the skin factor, however, sensitivity is negligible for the linear model, moderate for the radial model and most important for the spherical model. These results were next confirmed by performing Bayesian inferences using Markov Chain Monte Carlo technique to evaluate uncertainty on each parameter. Uncertainties appear significant for negligibly sensitive parameters but nearly insignificant for the most sensitive parameters. For all flow configurations, hydraulic conductivity appears however to be accurately estimated. Examples of interpretations for data collected in fractured rocks illustrate the application of these models and provide some recommendations.
... Detecting hydrogeologic barriers in the subsurface is important because they can compartmentalise groundwater flow (Ferrill et al. 2004;Marshall et al. 2019) and provide a mechanism for spring and wetland formation (Babiker and Gudmundsson 2004;Gleeson and Novakowski 2009). Steep hydraulic head gradients have been observed across hydrogeologic barriers under natural flow regimes; therefore, detailed potentiometric surface mapping can assist in their identification (Bense et al. 2003;Stamatis and Voudouris 2003;Bense and van Balen 2004;Cilona et al. 2015). Yet hydraulic head distributions may not definitively indicate the presence of barriers, particularly if the sampling density is low (Bredehoeft et al. 1992;Smerdon and Turnadge 2015). ...
... A sharp change in hydraulic head is observed across the fully-penetrating barrier. Sharp hydraulic head changes across barriers have been observed in several field studies through regional potentiometric mapping (Bense et al. 2003;Stamatis and Voudouris 2003;Bense and van Balen 2004;Ferrill et al. 2004;Cilona et al. 2015). The maximum difference in hydraulic head between cases with and without a barrier was only 2.6 m in this study; however, this is dependent on the model geometry, boundary conditions, and applied stresses. ...
Hydraulic head and groundwater age data are effective in building understanding of groundwater systems. Yet their joint role in
detecting and characterising low-permeability geological structures, i.e. hydrogeologic barriers such as faults and dykes, has not
been widely studied. Here, numerical flow and transport models, using MODFLOW-NWT and MT3D-USGS, were developed
with different hydrogeologic barrier configurations in a hypothetical aquifer. Computed hydraulic head and groundwater age
distributions were compared to those without a barrier. The conjoint use of these datasets helps in detecting vertically-oriented
barriers. Two forms of recharge were compared: (1) applied across the entire aquifer surface (uniform), and (2) applied to the
upstream part of the aquifer (upgradient). The hydraulic head distribution is significantly impacted by a barrier that penetrates the
aquifer’s full vertical thickness. This barrier also perturbs the groundwater age distribution when upgradient recharge prevails;
however, with uniform recharge, groundwater age is not successful in detecting the barrier. When a barrier is buried, such as by
younger sediment, hydraulic head data also do not clearly identify the barrier. Groundwater age data could, on the other hand,
prove to be useful if sampled at depth-specific intervals. These results are important for the detection and characterisation of
hydrogeologic barriers, whichmay play a significant role in the compartmentalisation of groundwater flow, spring dynamics, and
drawdown and recovery associated with groundwater extraction.
... The lateral sealing capability of a fault results from the sand/shale juxtaposition or by the creation of a very low permeability fault core in a highly permeable host rock [2,3]. In some hydrocarbon reservoirs faults acts as a barrier for lateral flow, and reservoir compartmentalization occurs [4]. ...
... The resulting fault zone structures (shown schematically in Figure 1) depend on the depth of the deformation zone, the host rock type, the tectonic environment and the magnitude of displacement and fluid flow. In low porosity rocks or under low confining stresses, the damage zone consists of dilatant fractures [10], while compaction bands or cataclastic deformation bands are also developed in high porosity sandstones [2,3,[11][12][13][14][15]. Therefore, permeability of fault damage zone may increase due to presence of dilatant fractures in shale-host zones and may be reduced in high permeability sand-host zones due to compaction band and intrusion of shale from adjoining shale beds. ...
Selection of deep saline aquifers for CO2 storage mandates evaluating probable leakage rates. Estimation of fault leakage potential and most probable leakage rates is an integral component of this analysis in regions where faults are frequently present. Due to the nature of the processes involved in the creation of faults and the environmental settings in their immediate vicinity, a large variation in properties may exist in fault structure. These may involve the existence of extreme heterogeneities and fractures at various scales. Heterogeneities may result in local trapping of CO2 while fractures may facilitate CO2 migration. In this study we examine the effects of fault heterogeneities and fractures distributions on leakage rates, and their implications for storage integrity. Fault characteristics from Southern Louisiana have been used to create a representative fault model to be used in 3D reservoir simulations. In order to account for varying fault structure, a total of nine cases are modelled, six without a central impermeable core and three with an impermeable central core. The simulation results show that a complex set of flow features exist in fluid flow inside the fault structure. Under the modelled conditions the heterogeneities impede the upward motion of leaking CO2, but the existence of high permeability channels nullify the positive impacts of local capillary trapping in the fault damage zone. The fracture presence results in substantial leakage rates, compared to cases where fractures are absent. It is also observed that faults with large shale gouge ratios act as flow barriers unless a high degree of fracturing exists in the fault damage zone. Significant differences in flow occur inside the fractures and matrix, and leakage rates measured at one point in space may not represent the actual behavior.
... On the contrary, the fault zones with a mylonite core have significantly lower permeability (Caine et al. 1996). The effects of faults on groundwater flow are small and localized, as observed by Ran et al. 2013 for normal displacements and Cilona et al. 2015 for strike-slip systems. In the Mazhou River basin (Fig. 2), a single thermal spring illustrates upward heat migration from the bedrock to the shallow zone along a fault, affecting the local groundwater path. ...
Shenzhen is the major financial and high-tech center in southern China. The megacity has grown rapidly in the last 40 years with the population increasing from about 30,000 in 1979 to 20 million in 2016. The study area (2,015 km2) is about 42% urban and 58% undeveloped land. The rapid development of the megacity has resulted in severe degradation of the groundwater and surface-water resources and has created a nearly insatiable demand for water, with an average consumption of 2000 × 106 m3/year. Groundwater is an important component of the baseflow of the many streams in the area and is used for potable water supply and irrigation in some of the rural parts of the municipality. This study develops a conceptual model and quantitative framework for assessing the groundwater resources of Shenzhen. The groundwater system consists of shallow aquifers of alluvium and weathered bedrock overlying low permeability igneous and sedimentary rocks. The complex geologic setting was conceptualized as a block structure with blocks bounded by high-angle faults. The water budget in Shenzhen was quantified. The estimated average groundwater discharge is about 12% of annual precipitation. The study provides a starting point to investigate how a megacity such as Shenzhen should manage and protect its groundwater as a strategic resource and environmental asset. It is also a basic management tool for analyzing and contributing to urban drainage concepts such as the “sponge city”.
