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1
Tang, Qingsong, Shuhang Tang, Bing Luo, Xin Luo, Liang Feng, Siyao Li, and Guanghui Wu. "Seismic Description of Deep Strike-slip Fault Damage Zone by Steerable Pyramid Method in the Sichuan Basin, China." Energies 15, no. 21 (October 31, 2022): 8131. http://dx.doi.org/10.3390/en15218131.
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Large quantities of gas resources have been found in the Paleo-Mesozoic carbonate rocks in the Sichuan Basin. However, many wells cannot obtain high production in deep low porosity-permeability reservoirs. For this contribution, we provide a steerable pyramid method for identifying the fault damage zone in the Kaijiang–Liangping platform margin, which is infeasible by conventional seismic methods. The results show that steerable pyramid processing could enhance the seismic fault imaging and a series of NW-trending strike-slip faults are found along the trend of the carbonate platform margin. The steerable pyramid attribute presents distinct vertical and horizontal boundaries of the fault damage zone, and heterogeneous intensity of an un-through-going damage zone. The width of the fault damage zone is generally varied in the range of 100–500 m, and could be increased to more than 1000 m in the fault overlap zone, intersection area, and fault tips. Further, the fault damage zone plays a constructive role in the high gas production in the deep tight carbonate reservoir. The results suggest the steerable pyramid method is favorable for identifying the weak strike-slip faults and their damage zone. The width of the fault damage zone is closely related to fault displacement, and the much wider damage zone is generally influenced by the fault overlapping and interaction. The fractured reservoirs in the fault damage zone could be a new favorable exploitation domain in the Sichuan Basin.
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Torabi, A., T. S. S. Ellingsen, M. U. Johannessen, B. Alaei, A. Rotevatn, and D. Chiarella. "Fault zone architecture and its scaling laws: where does the damage zone start and stop?" Geological Society, London, Special Publications 496, no. 1 (August 7, 2019): 99–124. http://dx.doi.org/10.1144/sp496-2018-151.
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AbstractDamage zones of different fault types are investigated in siliciclastics (Utah, USA), carbonates (Majella Mountain, Italy) and metamorphic rocks (western Norway). The study was conducted taking measurements of deformation features such as fractures and deformation bands on multiple 1D scanlines along fault walls. The resulting datasets are used to plot the frequency distribution of deformation features and to constrain the geometrical width of the damage zone for the studied faults. The damage-zone width of a single fault is constrained by identifying the changes in the slope of cumulative plots made on the frequency data. The cumulative plot further shows high deformation frequency by a steep slope (inner damage zone) and less deformation as a gentle slope (outer damage zone). Statistical distributions of displacement and damage-zone width and their relationship are improved, and show two-slope power-law distributions with a break point at c. 100 m displacement. Bleached sandstones in the studied siliciclastic rocks of Utah are associated with a higher frequency of deformation bands and a wider damage zone compared to the unbleached zone of similar lithology. Fault damage zones in the carbonate rocks of Majella are often host to open fractures (karst), demonstrating that they can also be conductive to fluid flow.
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Li, Jinxuan, Songfeng Guo, Shengwen Qi, Qianhui Wei, Bowen Zheng, Yu Zou, Yongchao Li, Yaguo Zhang, and Xiao Lu. "Spatial Variations of Deformation along a Strike-Slip Fault: A Case Study of Xianshuihe Fault Zone, Southwest China." Applied Sciences 14, no. 6 (March 14, 2024): 2439. http://dx.doi.org/10.3390/app14062439.
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The distribution of damage zones around a fault has long been regarded as a frontier and hot spot in the field of geoscience but is still not fully understood. In this study, we conducted field investigations and tests around the Xianshuihe fault zone (XSHF), a left-lateral strike-slip fault with a length of about 400 km located in the eastern margin of the Tibetan Plateau. The results reveal that the fracture frequency and rock strength parameters present a spatially asymmetric distribution along the fault and have a negative power-law correlation with the distance from the fault. The widths of the damage zones are approximately 20.8 km and 17.1 km in the southwest and northeast directions, respectively. Combined with the previous studies, we presented a negative power-law function to depict the correlation between slip displacement and the width of the damage zone and found that the growth rate of damage zone in faults with low displacement is greater than that in those with large displacement. The study demonstrates that the asymmetric distribution of the damage zone surrounding the XSHF is mainly due to the stress redistribution in different damage zones stemming from the left echelon and different activity rates of the blocks on both sides of the XSHF.
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Alaei, Behzad, and Anita Torabi. "Seismic imaging of fault damaged zone and its scaling relation with displacement." Interpretation 5, no. 4 (November 30, 2017): SP83—SP93. http://dx.doi.org/10.1190/int-2016-0230.1.
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We have studied seismically resolved damaged zone of normal faults in siliciclastic rocks of the Norwegian continental shelf. The workflow we have developed reveals structural details of the fault damaged zone and in particular, the subsidiary synthetic faults, horsetail at the main lateral fault tips at different depths and fault bend. These subsidiary or small fault segments form an area that can be clearly followed laterally and vertically. We call this area fault damaged zone. The studied damaged zone on seismic data comprises the fault core and the fault damage zone, as defined in outcrop studies. Spectral decomposition (short-time Fourier transform for time-frequency resolution and continuous wavelet transform) was performed on the data centered around faulted intervals. The magnitude of higher frequencies was used to generate coherence attribute volumes. Coherence attributes were filtered to enhance fault images. This integrated workflow improves fault images on reflection seismic data. Our approach reveals details of damaged zone geometry and morphology, which are comparable with the outcrop studies of similar examples conducted by previous researchers or us. We have extracted the fault geometry data including the segment length, displacement, and damaged zone width at different depths. Our results show that subsidiary faults, fault bends, linkage of fault segments, and branching in the fault tip (horsetail structure or process zone) all affect the width of the damaged zone and the distribution of displacement. We have seen a distinct increase in the fault damaged zone width near the fault bend locations. The fault segment length decreases with depth toward the lower fault tip, which is below the base Cretaceous unconformity. In addition, the displacement increases below the unconformity. In general, there is a positive correlation between fault displacement and the corresponding damaged zone width measured in this study, which is in agreement with previous studies.
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Lyu, Wenya, Lianbo Zeng, Zonghu Liao, Yuanyuan Ji, Peng Lyu, and Shaoqun Dong. "Fault damage zone characterization in tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China: Integrating cores, image logs, and conventional logs." Interpretation 5, no. 4 (November 30, 2017): SP27—SP39. http://dx.doi.org/10.1190/int-2016-0231.1.
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Fault damage zones around faults have a significant influence on fluid flow in tight-oil sandstones because they commonly act as localized conduits. Faults are developed in the tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China. We integrate cores, image logs, and conventional logs from vertical wells to characterize subsurface fault damage zones in the tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China. The results indicate that fault damage zones are intensively fractured or intensely broken in the cores. These fault damage zones present borehole collapse and widen sinusoidal curves in the image logs. The fractures in fault damage zones are predominant high dip angles. The fracture intensity decays with the increasing orthogonal distance from the faults within a fault damage zone. In fault damage zones, acoustic log (AC) values and compensated neutron log (CNL) values increase; density log (DEN) values decrease, dual induction log (ILD and ILM) and laterolog 8 (LL8) values decrease, the caliper log (CAL) presents borehole enlargement, and comprehensive fracture index log (CFI) values are greater than 0.43 and average 0.78. To identify fault damage zones by conventional logs in vertical wells, it is critical to distinguish fault damage zones from the background fractured zones. The ILM, CNL, ILD, LL8, and AC logs would be more useful than DEN logs for the distinction between background fractured zones and fault damage zones. The responses of fault damage zones in conventional logs are more intensive than those of background fractured zones, and the heights of fault damage zones are much greater than those of background fractured zones, which can be used for the distinction between fault damage zones and background fractured zones.
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Bloom, Colin K., Andrew Howell, Timothy Stahl, Chris Massey, and Corinne Singeisen. "The influence of off-fault deformation zones on the near-fault distribution of coseismic landslides." Geology 50, no. 3 (November 22, 2021): 272–77. http://dx.doi.org/10.1130/g49429.1.
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Abstract Coseismic landslides are observed in higher concentrations around surface-rupturing faults. This observation has been attributed to a combination of stronger ground motions and increased rock mass damage closer to faults. Past work has shown it is difficult to separate the influences of rock mass damage from strong ground motions on landslide occurrence. We measured coseismic off-fault deformation (OFD) zone widths (treating them as a proxy for areas of more intense rock mass damage) using high-resolution, three-dimensional surface displacements from the 2016 Mw 7.8 Kaikōura earthquake in New Zealand. OFD zones vary in width from ~50 m to 1500 m over the ~180 km length of ruptures analyzed. Using landslide densities from a database of 29,557 Kaikōura landslides, we demonstrate that our OFD zone captures a higher density of coseismic landslide incidence than generic “distance to fault rupture” within ~650 m of surface fault ruptures. This result suggests that the effects of rock mass damage within OFD zones (including ground motions from trapped and amplified seismic waves) may contribute to near-fault coseismic landslide occurrence in addition to the influence of regional ground motions, which attenuate with distance from the fault. The OFD zone represents a new path toward understanding, and planning for, the distribution of coseismic landslides around surface fault ruptures. Inclusion of estimates of fault zone width may improve landslide susceptibility models and decrease landslide risk.
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Zhao, Zhan, Jingtao Liu, Wenlong Ding, Ruiqiang Yang, and Gang Zhao. "Analysis of Seismic Damage Zones: A Case Study of the Ordovician Formation in the Shunbei 5 Fault Zone, Tarim Basin, China." Journal of Marine Science and Engineering 9, no. 6 (June 6, 2021): 630. http://dx.doi.org/10.3390/jmse9060630.
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Fault damage zone has an important influence on subsurface fluid flow and petrophysical properties. Therefore, it is of great significance to study the characteristics of fault damage zone for oil and gas development of ultra-deep carbonate formation. This study uses seismic data and the derived variance attribute to identify two types of damage zones and analyze the spatial geometric characteristics of the damage zones. The results show that the type 1 damage zone is wider than the type 2 damage zone. The width of damage zones distributed on both sides of the Shunbei 5 fault core shows obvious asymmetry, and the damage zone width and throw conforms to the typical power-law distribution on the log-log plot. We discuss the factors affecting the width of the damage zone and its formation process. Finally, we discuss the influence of the damage zones on oil and gas exploration. It seems that the seismic variance attribute is a useful technique for characterizing the ultra-deep strike-slip fault damage zones.
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Huang, Rui, Liqun Li, and Zhiyi Chen. "Effects of Reverse Fault Dislocation Application Method for Tunnelling Through Active Faults." IOP Conference Series: Earth and Environmental Science 1334, no. 1 (May 1, 2024): 012026. http://dx.doi.org/10.1088/1755-1315/1334/1/012026.
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Abstract Active faults seriously threaten the structural integrity of mountain tunnels in seismic zones, and reverse faults are the most hazardous. A tunnel project in the western region was used as a reference to analyze the damage mechanism of tunnels under different modes of reverse fault displacement. The ABAQUS finite element analysis software was employed for the numerical simulation, and a quasi-static method was adopted to analyze the displacement and stress response patterns of the tunnel structure traversing the fault under three typical modes of reverse fault displacement. This led to deriving the tunnel structure’s longitudinal damage modes and impact zones based on reverse fault displacement. The study revealed that the damage modes of the tunnel under different fault displacement modes varied, which was reflected in the different degrees of shear and compression. Regardless of the fault displacement mode, the tunnel structure located within the fault fracture zone was severely damaged, with the most severe damage occurring at the interface between the fixed plate and the fault displacement section. Therefore, in the design, special attention should be paid to the displacement resistance performance of the dangerous sections of the tunnel. The research results provide significant reference and guidance for similar projects.
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Liao, Zonghu, Luyao Hu, Xiaodi Huang, Brett M. Carpenter, Kurt J. Marfurt, Saiyyna Vasileva, and Yun Zhou. "Characterizing damage zones of normal faults using seismic variance in the Wangxuzhuang oilfield, China." Interpretation 8, no. 4 (June 30, 2020): SP53—SP60. http://dx.doi.org/10.1190/int-2020-0004.1.
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We have investigated the distribution and thickness of damage zones for a system of secondary normal faults in the subsurface of the Wangxuzhuang oilfield, China. Based on seismic variance analysis, we find (1) four isolated faults with approximately 2 km length and approximately 200 m damage-zone thickness. The damage zones of these isolated faults reveal a decaying intensity of deformation from the fault core to the protolith, which fits a power-law form [Formula: see text] similar to that observed in the field. (2) A merged fault with approximately 400 m thickness. (3) A bifurcated fault with approximately 400 m thickness and three linked segments. Damage zones that consist of several subsidiary faults are thicker than those of isolated faults. The displacement-length analyses of the four isolated faults suggest the constant-length growth of the limestone in this case. We determine the potential to apply seismic variance to systematically characterize damage zones as potential fluid migration conduits on the basin scale.
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Pilecka, Elżbieta, Krystyna Stec, Jacek Chodacki, Zenon Pilecki, Renata Szermer-Zaucha, and Krzysztof Krawiec. "The Impact of High-Energy Mining-Induced Tremor in a Fault Zone on Damage to Buildings." Energies 14, no. 14 (July 7, 2021): 4112. http://dx.doi.org/10.3390/en14144112.
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Seismic energy propagation from the hypocentre of mining-induced tremors usually causes an uneven distribution of the peak ground velocity PGVHmax in tectonically complicated structures, and consequently, an uneven distribution of damage to buildings located on the ground surface. This study aimed to estimate the impact of high-energy mining-induced tremors in fault zones on damage to buildings. In the study, we describe a case of one of the highest-energy mining-induced tremors E = 4.0 · 108 J (local magnitude ML = 3.6) that occurred in the Upper Silesian Coal Basin (USCB), Poland. The hypocentre of the tremor was most probably located in the Barbara fault zone, one of the larger faults in that western part of the USCB. Numerous damaged buildings on the terrain surface were registered, both in the epicentral zone and at a greater distance from the epicentre, mostly from the southern side of the Barbara fault zone. We calculated that the tremor was characterised by a normal slip mechanism associated with the same kind of fault as the Barbara fault. The azimuth of the nodal planes was similar to the west-east direction, which is consistent with the azimuth of the Barbara fault. From the focal mechanism, the greatest propagation of seismic energy occurred in south and west-east directions from the tremor hypocentre towards the surface. It was found that from the northern side of the hanging wall of the Barbara fault, there were 14 instances of damage (19%), and in the southern part of a hanging wall, there were 58 (81%). Therefore, the directionality of seismic energy propagation is aligned with the focal mechanism acting in the Barbara fault. It has also been concluded that a width of the zone of up to about 1200 m along the Barbara fault is the most threatening on the basis of registered building damage in the geological conditions of USCB. The study has shown that in assessing the impact of mining-induced tremors on buildings and the environment, the disturbance of seismic energy propagation by larger faults should be considered.
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Tillner, Elena, Maria Langer, Thomas Kempka, and Michael Kühn. "Fault damage zone volume and initial salinity distribution determine intensity of shallow aquifer salinisation in subsurface storage." Hydrology and Earth System Sciences 20, no. 3 (March 8, 2016): 1049–67. http://dx.doi.org/10.5194/hess-20-1049-2016.
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Abstract. Injection of fluids into deep saline aquifers causes a pore pressure increase in the storage formation, and thus displacement of resident brine. Via hydraulically conductive faults, brine may migrate upwards into shallower aquifers and lead to unwanted salinisation of potable groundwater resources. In the present study, we investigated different scenarios for a potential storage site in the Northeast German Basin using a three-dimensional (3-D) regional-scale model that includes four major fault zones. The focus was on assessing the impact of fault length and the effect of a secondary reservoir above the storage formation, as well as model boundary conditions and initial salinity distribution on the potential salinisation of shallow groundwater resources. We employed numerical simulations of brine injection as a representative fluid. Our simulation results demonstrate that the lateral model boundary settings and the effective fault damage zone volume have the greatest influence on pressure build-up and development within the reservoir, and thus intensity and duration of fluid flow through the faults. Higher vertical pressure gradients for short fault segments or a small effective fault damage zone volume result in the highest salinisation potential due to a larger vertical fault height affected by fluid displacement. Consequently, it has a strong impact on the degree of shallow aquifer salinisation, whether a gradient in salinity exists or the saltwater–freshwater interface lies below the fluid displacement depth in the faults. A small effective fault damage zone volume or low fault permeability further extend the duration of fluid flow, which can persist for several tens to hundreds of years, if the reservoir is laterally confined. Laterally open reservoir boundaries, large effective fault damage zone volumes and intermediate reservoirs significantly reduce vertical brine migration and the potential of freshwater salinisation because the origin depth of displaced brine is located only a few decametres below the shallow aquifer in maximum. The present study demonstrates that the existence of hydraulically conductive faults is not necessarily an exclusion criterion for potential injection sites, because salinisation of shallower aquifers strongly depends on initial salinity distribution, location of hydraulically conductive faults and their effective damage zone volumes as well as geological boundary conditions.
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Ma, Yuchuan, Guangcai Wang, Rui Yan, Bo Wang, Huaizhong Yu, Chen Yu, Chong Yue, and Yali Wang. "Relationship between Earthquake-Induced Hydrologic Changes and Faults." Water 13, no. 19 (October 8, 2021): 2795. http://dx.doi.org/10.3390/w13192795.
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Hydraulic properties of fault zones are important to understanding the pore pressure development and fault stability. In this work, we examined the relationship between water level changes caused by the 2008 Wenchuan Mw 7.9 earthquake and faults using four wells with the same lithology around the Three Gorges Dam, China. Two of the wells penetrating the fault damage zones recorded sustained water level changes, while the other two wells that are not penetrating any fault damage zones recorded transient water level changes. The phase shift and tidal factor calculated from water level, a proxy of permeability and storage coefficient, revealed that both the permeability and storage coefficient changed in the two wells penetrating the fault damage zones, while the other two wells not penetrating the fault damage zone did not show any change in permeability and storage coefficient. Thus, we tentatively suggest that faults may play an important controlling role on earthquake-induced hydrologic changes because the detrital or clogging components in the fractures may be more easily removed by seismic waves.
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Naito, Shohei, Ken Xiansheng Hao, Shigeki Senna, Takuma Saeki, Hiromitsu Nakamura, Hiroyuki Fujiwara, and Takashi Azuma. "Investigation of Damages in Immediate Vicinity of Co-Seismic Faults During the 2016 Kumamoto Earthquake." Journal of Disaster Research 12, no. 5 (September 27, 2017): 899–915. http://dx.doi.org/10.20965/jdr.2017.p0899.
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In the 2016 Kumamoto earthquake, the Futagawa fault zone and the Hinagu fault zone were active in some sections, causing severe damage in neighboring areas along the faults. We conducted a detailed investigation of the surface earthquake fault, building damage, and site amplification of shallow ground within about 1 km of the neighboring areas of the fault. The focus was mainly on Kawayou district, Minamiaso village and Miyazono district, Mashiki town, and locations that suffered particularly severe building damage. We explored the relationship between local strong motion and building damage caused in areas that were in the immediate vicinity of the active fault.
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Qu, Dongfang, Jan Tveranger, and Muhammad Fachri. "Influence of deformation-band fault damage zone on reservoir performance." Interpretation 5, no. 4 (November 30, 2017): SP41—SP56. http://dx.doi.org/10.1190/int-2016-0229.1.
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Access to 3D descriptions of fault zone architectures and recent development of modeling techniques allowing explicit rendering of these features in reservoir models, provide a new tool for detailed implementation of fault zone properties. Our aim is to assess how explicit rendering of fault zone architecture and properties affects performance of fluid flow simulation models. The test models use a fault with a maximum 100 m displacement and a fault damage zone with petrophysical heterogeneity caused by the presence of deformation bands. The distribution pattern of deformation bands in fault damage zones is well-documented, which allows generation of realistic models. A multiscale modeling workflow is applied to incorporate these features into reservoir models. Model input parameters were modulated to provide a range of property distributions, and the interplay between the modeling parameters and reservoir performance was analyzed. The influence of deformation-band damage zone on reservoir performance in the presence of different fault core transmissibility-multipliers was investigated. Two configurations are considered: one in which the fault terminates inside the model domain, representing a case in which the fluid can flow around the fault, and one in which the fault dissects the entire model domain, representing a case in which the fluid is forced to cross the fault. We observed that the impact of deformation-band fault damage zone on reservoir performance changes when the fault core transmissibility multiplier is changed. Reservoir performance is insensitive to changing damage zone heterogeneity in a configuration in which flow can move around the fault. Where flow cannot bypass the fault, the influence of fault damage zone heterogeneity on reservoir performance is significant even when the fault core transmissibility multiplier is low.
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Paul, Pijush K., Mark D. Zoback, and Peter H. Hennings. "Fluid Flow in a Fractured Reservoir Using a Geomechanically Constrained Fault-Zone-Damage Model for Reservoir Simulation." SPE Reservoir Evaluation & Engineering 12, no. 04 (July 6, 2009): 562–75. http://dx.doi.org/10.2118/110542-pa.
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Summary Secondary fractures and faults associated with reservoir-scale faults affect both permeability and permeability anisotropy and hence play an important role in controlling the production behavior of a faulted reservoir. It is well known from geologic studies that there is a concentration of secondary fractures and faults in damage zones adjacent to large faults. Because there are usually inadequate data to fully incorporate damage-zone fractures and faults into reservoir-simulation models, this study uses the principles of dynamic rupture propagation from earthquake seismology to predict the nature of fractured/damage zones associated with reservoir-scale faults. We include geomechanical constraints in our reservoir model and propose a generalized workflow to incorporate damage zones into reservoir-simulation models more routinely. The model we propose calculates the extent of the damage zone along the fault plane by estimating the volume of rock brought to failure by the stress perturbation associated with dynamic-rupture propagation. We apply this method to a real reservoir using both field- and well-scale observations. At the rupture front, damage intensity gradually decreases as we move away from the rupture front or fault plane. In the studied reservoir, the secondary-failure planes in the damage zone are high-angle normal faults striking subparallel to the parent fault, which may affect the permeability of the reservoir in both horizontal and vertical directions. We calibrate our modeling with both outcrop and well observations from a number of studies. We show that dynamic-rupture propagation gives a reasonable first-order approximation of damage zones in terms of permeability and permeability anisotropy in order to be incorporated into reservoir simulators. Introduction Fractures and faults in reservoirs present both problems and opportunities for exploration and production. The heterogeneity and complexity of fluid-flow paths in fractured rocks make it difficult to predict how to produce a fractured reservoir optimally. It is usually not possible to fully define the geometry of the fractures and faults controlling flow, and it is difficult to integrate data from markedly different scales (i.e., seismic, well log, core) into reservoir-simulation models. A number of studies in hydrogeology and the petroleum industry have dealt with modeling fractured reservoirs (Martel and Peterson 1991; Lee et al. 2001; Long and Billaux 1987; Gringarten 1996; Matthäi et al. 2007). Various methodologies, both deterministic and stochastic, have been developed to model the effects of reservoir heterogeneity on hydrocarbon flow and recovery. The work by Smart et al. (2001), Oda (1985, 1986), Maerten et al. (2002), Bourne and Willemse (2001), and Brown and Bruhn (1998) quantifies the stress sensitivity of fractured reservoirs. Several studies (Barton et al. 1995; Townend and Zoback 2000; Wiprut and Zoback 2000) that include fracture characterizations from wellbore images and fluid conductivity from the temperature and the production logs indicate fluid flow from critically stressed fractures. Additional studies emphasize the importance and challenges of coupling geomechanics in reservoir fluid flow (Chen and Teufel 2000; Couples et al. 2003; Bourne et al. 2000). These studies found that a variety of geomechanical factors may be very significant in some of the fractured reservoirs. Secondary fractures and faults associated with large-scale faults also appear to be quite important in controlling the permeability of some reservoirs. Densely concentrated secondary fractures and faults near large faults are often referred to as damage zones, which are created at various stages of fault evolution: before faulting (Aydin and Johnson 1978; Lyakhovsky et al. 1997; Nanjo et al. 2005), during fault growth (Chinnery 1966; Cowie and Scholz 1992; Anders and Wiltschko 1994; Vermily and Scholz 1998; Pollard and Segall 1987; Reches and Lockner 1994), and during the earthquake slip events (Freund 1974; Suppe 1984; Chester and Logan 1986) along the existing faults. Lockner et al. (1992) and Vermilye and Scholz (1998) show that the damage zones from the prefaulting stage are very narrow and can be ignored for reservoir-scale faults. The damage zone formed during fault growth can be modeled using dynamic rupture propagation along a fault plane (Madariaga 1976; Kostov 1964; Virieux and Madariaga 1982; Harris and Day 1997). Damage zones caused by slip on existing faults are important, especially when faults are active in present-day stress conditions because slip creates splay fractures at the tips of the fault and extends the damage zone created during the fault-growth stage (Collettini and Sibson 2001; Faulkner et al. 2006; Lockner and Byerlee 1993; Davatzes and Aydin 2003; Myers and Aydin 2004). In this paper, we first introduce a reservoir in which there appears to be significant permeability anisotropy associated with flow parallel to large reservoir-scale faults. Next, we build a geomechanical model of the field and then discuss the relationship between fluid flow and geomechanics at well-scale fracture and fault systems. To consider what happens in the reservoir at larger scale, we use dynamic rupture modeling to theoretically predict the size and extent of damage zones associated with the reservoir-scale faults.
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Williams, Jack N., Virginia G. Toy, Cécile Massiot, David D. McNamara, Steven A. F. Smith, and Steven Mills. "Controls on fault zone structure and brittle fracturing in the foliated hanging wall of the Alpine Fault." Solid Earth 9, no. 2 (April 23, 2018): 469–89. http://dx.doi.org/10.5194/se-9-469-2018.
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Abstract. Three datasets are used to quantify fracture density, orientation, and fill in the foliated hanging wall of the Alpine Fault: (1) X-ray computed tomography (CT) images of drill core collected within 25 m of its principal slip zones (PSZs) during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer images, (2) field measurements from creek sections up to 500 m from the PSZs, and (3) CT images of oriented drill core collected during the Amethyst Hydro Project at distances of ∼ 0.7–2 km from the PSZs. Results show that within 160 m of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to have formed at relatively high confining pressures and/or in rocks that had a weak mechanical anisotropy. Conversely, at distances greater than 160 m from the PSZs, fractures are typically open and subparallel to the mylonitic or schistose foliation, implying that fracturing occurred at low confining pressures and/or in rocks that were mechanically anisotropic. Fracture density is similar across the ∼ 500 m width of the field transects. By combining our datasets with measurements of permeability and seismic velocity around the Alpine Fault, we further develop the hierarchical model for hanging-wall damage structure that was proposed by Townend et al. (2017). The wider zone of foliation-parallel fractures represents an outer damage zone that forms at shallow depths. The distinct < 160 m wide interval of widely oriented gouge-filled fractures constitutes an inner damage zone. This zone is interpreted to extend towards the base of the seismogenic crust given that its width is comparable to (1) the Alpine Fault low-velocity zone detected by fault zone guided waves and (2) damage zones reported from other exhumed large-displacement faults. In summary, a narrow zone of fracturing at the base of the Alpine Fault's hanging-wall seismogenic crust is anticipated to widen at shallow depths, which is consistent with fault zone flower structure models.
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Riegel, Hannah, Miller Zambrano, Fabrizio Balsamo, Luca Mattioni, and Emanuele Tondi. "Petrophysical Properties and Microstructural Analysis of Faulted Heterolithic Packages: A Case Study from Miocene Turbidite Successions, Italy." Geofluids 2019 (June 2, 2019): 1–23. http://dx.doi.org/10.1155/2019/9582359.
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Geofluid reservoirs located in heterolithic successions (e.g., turbidites) can be affected by vertical and lateral compartmentalization due to interbedded fine-grained facies (i.e., shale, siltstones) and the presence of faults, respectively. A fault can behave as a conduit or barrier to fluid flow depending on its architecture and the individual hydraulic behavior of its components (i.e., fault core, damage zone). The fault core, normally composed by fault rock or smeared clay material, commonly acts as a flow inhibitor across the fault. Fault-related fractures (macro- and microscopic) in the damage zone generally increase the permeability parallel to the fault, except when they are cemented or filled with gouge material. Although macrofractures (which define the fracture porosity) dominate fluid flow, the matrix porosity (including microfractures) begins to have a more important role in fluid flow as the aperture of macrofractures is occluded, particularly at greater depth. This study investigates the variation in matrix permeability in fault zones hosted in heterolithic successions due to fault architecture and stratigraphy of host rock (i.e., sand-rich turbidites). Two key areas of well-exposed, faulted Miocene turbidites located in central and southern Italy were selected. For this study, six separate fault zones of varying offset were chosen. Each impacts heterolithic successions that formed under similar tectonic conditions and burial depths. Across the selected fault zones, an extensive petrophysical analysis was done in the field and laboratory, through air permeameter measurements, thin section, and synchrotron analysis in both host rock, damage zone, and fault core. Results suggest that the amount and distribution of clay layers in a heterolithic sequence affects fluid flow across the fault, regardless of fault offset.
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Papoulis, D., D. Romiou, S. Kokkalas, and P. Lampropoulou. "Clay minerals from the Arkitsa fault gouge zone, in Central Greece, and implications for fluid flow." Bulletin of the Geological Society of Greece 47, no. 2 (January 24, 2017): 616. http://dx.doi.org/10.12681/bgsg.11095.
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Clay minerals in shallow fault rocks are increasingly recognized as key to the mechanical and seismogenic behavior of faults and fluid flow circulation within the fault core and the surrounding damage zone. We therefore studied faultgouge mineralogy from samples derived from the ENE-trending Arkitsa fault zone, in east-central Greece, in order to testify if the fault is acting as a channel for fluid flow and whether the conditions that characterize the flow can be identified. Clay-gouge samples were collected within the fault core zone, as well as in the broader fault damage area. Consequently, the samples were analyzed by X-Ray Diffraction, SEM and Electron microprobe analyses. The minerals that were identified within the centre of the fault zone are: Montmorillonite, corrensite, illite, micro-calcite, dolomite, quartz, plagioclase and K-feldspars. The absence of corrensite, a clay mineral usually formed in hydrothermal conditions, in the samples from the broader fault damage area indicates that the circulation of hydrothermal fluids is mostly confined within and around the fault core zone. The assemblages within the fault gouge zone and especially the presence of corrensite, combined with the absence of laumontite, indicate hydrothermal alteration at neutral to alkaline conditions and a temperature range at about 100-150 oC.
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Botter, Charlotte, Nestor Cardozo, Dongfang Qu, Jan Tveranger, and Dmitriy Kolyukhin. "Seismic characterization of fault facies models." Interpretation 5, no. 4 (November 30, 2017): SP9—SP26. http://dx.doi.org/10.1190/int-2016-0226.1.
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Faults play a key role in reservoirs by enhancing or restricting fluid flow. A fault zone can be divided into a fault core that accommodates most of the displacement and a surrounding damage zone. Interpretation of seismic data is a key method for studying subsurface features, but the internal structure and properties of fault zones are often at the limit of seismic resolution. We have investigated the seismic response of a vertical fault zone model in sandstone, populated with fault facies based on deformation band distributions. Deformation bands reduce the porosity of the sandstone, and they condition its elastic properties. We generate synthetic seismic cubes of the fault facies model for several wave frequencies and under realistic conditions of reservoir burial and seismic acquisition. Seismic image quality and fault zone definition are highly dependent on wave frequency. At a low wave frequency (e.g., 10 Hz), the fault zone is broader and no information about its fault facies distribution can be extracted. At higher wave frequencies (e.g., 30 and 60 Hz), seismic attributes, such as tensor and envelope, can be used to characterize the fault volume and its internal structure. Based on these attributes, we can subdivide the fault zone into several seismic facies from the core to the damage zone. Statistical analyses indicate a correlation between the seismic attributes and the fault internal structure, although seismic facies, due to their coarser resolution, cannot be matched to individual fault facies. The seismic facies can be used as input for reservoir models as spatial conditioning parameters for fault facies distributions inside the fault zone. However, relying only on the information provided by seismic analyses might not be enough to create high-resolution fault reservoir models.
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Cheng, Zhiyuan, Yunhua Su, and Chenhan Xu. "Seismic Response of Mountain Tunnels by Comprehensive Analysis Methods and Feasible Aseismic Measures." Highlights in Science, Engineering and Technology 28 (December 31, 2022): 31–44. http://dx.doi.org/10.54097/hset.v28i.4054.
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In mountainous area, earthquake is an inevitable factor during the construction of tunnel. Earthquake can cause great damage to faults and mountain slopes, and at the same time, the deformation and failure of mountain tunnels are closely related to faults and landslides. This study analyzes the impacts of faults and landslides on the mountain tunnel by numerical modelling, model test and field investigation, and discusses the corresponding engineering countermeasures. Mountain tunnel through fault tends to be damaged severely because it may be shorn by fault dislocation. However, the fractured tunnel may undergo even severer damage due to earthquake wave. Various factors, including earthquake wave, condition of surrounding rock, width of fault, relative position of fault and tunnel, fault friction velocity, fault activity and lining section type, affect the seismic performance of tunnel through fault. In addition, buffer layer, grouting, shock absorption gap, sectional tunnel lining with flexible joints, fiber reinforced concrete lining, and ultra-excavating are all available aseismic or anti-dislocation measures. The damage mode and degree of landslide to tunnel are related to the type of tunnel, and the different relative positions of the tunnel and the sliding surface controls damages. Landslide prevention and control engineering measures mainly include weight loss, drainage, construction of retaining works, improvement and reinforcement of soil and rock properties of sliding zone, etc.
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Pizzati, Mattia, Fabrizio Balsamo, Fabrizio Storti, and Paola Iacumin. "Physical and chemical strain-hardening during faulting in poorly lithified sandstone: The role of kinematic stress field and selective cementation." GSA Bulletin 132, no. 5-6 (October 25, 2019): 1183–200. http://dx.doi.org/10.1130/b35296.1.
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Abstract In this work, we report the results of a multidisciplinary study describing the structural architecture and diagenetic evolution of the Rocca di Neto extensional fault zone developed in poorly lithified sandstones of the Crotone Basin, Southern Italy. The studied fault zone has an estimated displacement of ∼90 m and consists of: (1) a low-deformation zone with subsidiary faults and widely spaced deformation bands; (2) an ∼10-m-wide damage zone, characterized by a dense network of conjugate deformation bands; (3) an ∼3-m-wide mixed zone produced by tectonic mixing of sediments with different grain size; (4) an ∼1-m-wide fault core with bedding transposed into foliation and ultra-comminute black gouge layers. Microstructural investigations indicate that particulate flow was the dominant early-stage deformation mechanism, while cataclasis became predominant after porosity loss, shallow burial, and selective calcite cementation. The combination of tectonic compaction and preferential cementation led to a strain-hardening behavior inducing the formation of “inclined conjugate deformation band sets” inside the damage zone, caused by the kinematic stress field associated with fault activity. Conversely, conjugate deformation band sets with a vertical bisector formed outside the damage zone in response to the regional extensional stress field. Stable isotope analysis helped in constraining the diagenetic environment of deformation, which is characterized by mixed marine-meteoric signature for cements hosted inside the damage zone, while it progressively becomes more meteoric moving outside the fault zone. This evidence supports the outward propagation of fault-related deformation structures in the footwall damage zone.
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Xin, Guoxu, Bo Wang, Haozhang Zheng, Linfeng Zeng, and Xinxin Yang. "Study on Water Inrush Characteristics of Hard Rock Tunnel Crossing Heterogeneous Faults." Applied Sciences 14, no. 6 (March 17, 2024): 2536. http://dx.doi.org/10.3390/app14062536.
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Fault water inflow is one of the most severe disasters that can occur during the construction of hard and brittle rock tunnels. These tunnels traverse brittle fault breccia zones comprising two key components: a damage zone dominated by low-strain fractures and an internally nested high-strain zone known as the fault core. Structural heterogeneity influences the mechanical and hydraulic properties within fault breccia zones, thereby affecting the evolving characteristics of water inflow in hard rock faulting. Based on the hydraulic characteristics within hard rock fault zones, this paper presents a generalized dual-porosity fluid-solid coupling water inflow model. The model is utilized to investigate the spatiotemporal evolution patterns of water pressure, inflow velocity, and water volume during tunneling through heterogeneous fault zones in hard rock. Research findings indicate that when tunnels pass through the damage zones, water inrush velocity is high, yet the water volume is low, and both decrease rapidly over time. Conversely, within the core regions of faults, water inflow velocity is low, yet the water volume is high, and both remain relatively stable over time. Simulation results closely align with the water inflow data from China’s largest cross-section tunnel, the Tiantai Mountain Tunnel, thus validating the accuracy of the evolutionary model proposed in this paper. These findings offer a new perspective for devising effective prevention strategies for water inflow from heterogeneous faults.
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Fan, Zhen Li. "Research on the Influence by Different Dip Angles Faults of the Damage Height of Superincumbent Stratum." Applied Mechanics and Materials 675-677 (October 2014): 1421–24. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.1421.
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For the issue of fault impact on the height of water-flowing fractured zone, the study worked out several damage heights of superincumbent stratum under the influence of different dip angles faults. The research shows that small angle fault influence area is apt to develop a wide range of the plastic zone,and the water-flowing fractured zone of high-angle fault influence area is apt to increase along the fault surface and breakover the aquifers of coal seam roof and floor.
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Gudmundsson, Agust. "Transport of Geothermal Fluids along Dikes and Fault Zones." Energies 15, no. 19 (September 27, 2022): 7106. http://dx.doi.org/10.3390/en15197106.
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Field observations of active and fossil natural geothermal fields indicate that geothermal fluids are primarily transported along dikes and fault zones. Fluid transport along dikes (commonly through fractures at their margins) is controlled by the cubic law where the volumetric flow rate depends on the aperture of the fracture in the 3rd power. Dikes (and inclined sheets) also act as heat sources for geothermal fields. In high-temperature fields in volcanoes in Iceland dikes and inclined sheets constitute 80–100% of the rock at crustal depths of 1.5–2 km. Holocene feeder-dikes are known to have increased the activity of associated geothermal fields. Fault zones transport geothermal fluids along their two main hydromechanical units, the core and the damage zone. The core is comparatively thin and primarily composed of breccia, gouge, and clay and related low-permeability porous materials. By contrast, the fault damage zone is characterised by fractures whose frequency is normally highest at the contact between the core and the damage zone. Fluid transport in the damage zone, and in the core following fault slip, is controlled by the cubic law. During non-slip periods fluid transport in the core is primarily controlled by Darcy’s law. Secondary mineralisation (forming mineral veins and amygdales) tends to reduce the fault-zone permeability. Repeated earthquake activity is thus needed to maintain the permeability of fault zones in active natural geothermal fields.
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Li, Ting Chun, Yun Teng Yin, and Jian Zhang Liu. "Analysis on Seismic Damage Mechanism and Anti-Seismic Measures of Tunnels in Fault Fracture Zone." Advanced Materials Research 446-449 (January 2012): 2110–17. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2110.
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Fault fracture zone is an important factor that leads to tunnel seismic damage. In order to research failure mechanism and anti-seismic measures of tunnels across large fault fracture zone, theoretical analysis and numerical simulation has been done to Jiaozhou Bay submarine tunnel in Qingdao. The research results indicate that: in fault fracture zones, surrounding rocks instability resulting from ground motion, the huge earthquake inertial force, and the deformation energy by bedrock surface wave with macro energy all can cause damage to tunnel lining, yet the latter is the primary reason; when the differences of mass density and stiffness between tunnel lining and wall rocks become big, ductile tunnels with light weight will aggravate damage to tunnels rather than improve their anti-seismic capability; keeping stability of surrounding rocks and guaranteeing mass density and stiffness of tunnel lining to be the same as or similar to that of surrounding rocks could prevent tunnel damages in fault fracture zone, yet the latter is the most effective way. This research achievement can set particular examples for research on seismic damage mechanism and for anti-seismic design of tunnel structure in highly seismic regions.
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Yang, Guotao, Sujian Ma, Liang Zhang, Xinrong Tan, Rui Tang, and Yang Liu. "Analysis of Damage Mechanism of Tunnel Lining Structure under the Coupling Action of Active Fault." Advances in Civil Engineering 2021 (May 19, 2021): 1–10. http://dx.doi.org/10.1155/2021/9997924.
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To reveal the failure mechanism of tunnel structure under active fault movement, based on the pseudostatic elastoplastic finite element method, the failure modes of the tunnel lining are studied under different movement ratios of strike-slip faults and thrust faults with 45° dip angle by using numerical simulation. The results show that the range of significant lining failure section can be determined according to any direction of the coupling fault movement decomposition direction, and the damage effect is determined by the overall movement amount of the coupling fault. The significant damage area of the lining under the action of the coupling fault is the same as the area of deformation, which mainly manifests as tensile failure. Compressive failure occurs in the boundary area between the fracture zone and the hanging wall and foot wall. The plastic strain is the largest in the area where the arch waist and the arch bottom intersect. The development of tunnel lining plastic zone under coupling fault is from arch top and arch bottom to both sides of the arch waist. The development of the plastic zone under active fault is mainly determined by the form of fault with a large ratio. The research results can provide a reference for the design and safety evaluation of tunnel crossing active faults.
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McGrath, Annette G., and Ian Davison. "Damage zone geometry around fault tips." Journal of Structural Geology 17, no. 7 (July 1995): 1011–24. http://dx.doi.org/10.1016/0191-8141(94)00116-h.
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Srivastava, Deepak C., Ajanta Goswami, and Amit Sahay. "Strain-partitioned dextral transpression in the Great Boundary Fault Zone around Chittaurgarh, NW Indian Shield." Geological Magazine 158, no. 9 (March 22, 2021): 1585–99. http://dx.doi.org/10.1017/s0016756821000157.
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AbstractDelimiting the Aravalli mountain range in the east, the Great Boundary Fault (GBF) occurs as a crustal-scale tectonic lineament in the NW Indian Shield. The structural and tectonic characteristics of the GBF are, as yet, not well-understood. We attempt to fill this gap by using a combination of satellite image processing, high-resolution outcrop mapping and structural analysis around Chittaurgarh. The study area exposes the core and damage zone of the GBF. Three successive phases of folding, F1, F2 and F3, are associated with deformation in the GBF. The large-scale structural characteristics of the GBF core are: (i) a non-coaxial refolding of F1 folds by F2 folds; and (ii) the parallelism between the GBF and F2 axial traces. In addition, numerous metre-scale ductile shear zones cut through the rocks in the GBF core. The damage zone is characterized by the large-scale F1 folds and the mesoscopic-scale strike-slip faults, thrusts and brittle-ductile shear zones. Several lines of evidence, such as the inconsistent overprinting relationship between the strike-slip faults and thrusts, the occurrence of en échelon folds and the palaeostress directions suggest that the GBF is a dextral transpression fault zone. Structural geometry and kinematic indicators imply a wrench- and contraction-dominated deformation in the core and damage zone, respectively. We infer that the GBF is a strain-partitioned dextral transpression zone.
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Xue, Lian, Hai-Bing Li, Emily E. Brodsky, Zhi-Qing Xu, Yasuyuki Kano, Huan Wang, James J. Mori, et al. "Continuous Permeability Measurements Record Healing Inside the Wenchuan Earthquake Fault Zone." Science 340, no. 6140 (June 27, 2013): 1555–59. http://dx.doi.org/10.1126/science.1237237.
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Permeability controls fluid flow in fault zones and is a proxy for rock damage after an earthquake. We used the tidal response of water level in a deep borehole to track permeability for 18 months in the damage zone of the causative fault of the 2008 moment magnitude 7.9 Wenchuan earthquake. The unusually high measured hydraulic diffusivity of 2.4 × 10−2square meters per second implies a major role for water circulation in the fault zone. For most of the observation period, the permeability decreased rapidly as the fault healed. The trend was interrupted by abrupt permeability increases attributable to shaking from remote earthquakes. These direct measurements of the fault zone reveal a process of punctuated recovery as healing and damage interact in the aftermath of a major earthquake.
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Doğangün, Adem, Burak Yön, Onur Onat, Mehmet Emin Öncü, and Serkan Sağıroğlu. "Seismicity of East Anatolian of Turkey and Failures of Infill Walls Induced by Major Earthquakes." Journal of Earthquake and Tsunami 15, no. 04 (March 13, 2021): 2150017. http://dx.doi.org/10.1142/s1793431121500172.
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There are three major fault zones in Turkey scattered around the country known as East Anatolian Fault (EAF), North Anatolian Fault (NAF) and Anatolian-Aegean Subduction Zone (AASZ). Last two decades, EAF has been rather quiescent compared with NAF. However, this quiescence was broken in the beginning of the millennium. The strong shaking was started in 2003 with Bingöl earthquake (Mw = 6.3) and the last earthquake on the EAF is the Sivrice-Elazığ (Mw = 6.8) on January 24, 2020. Strong seismicity of these faults damaged the structures severely and caused death of the habitants. This study aims to present, seismotectonic of the region, general characteristics of the earthquakes and more specifically to report structural damage of infill walls of the structure’s damages caused by these earthquakes. Damage evaluation and identification of the observed infill wall damages due to 2003 Bingöl, 2011 Van earthquakes and January 24, 2020 Sivrice-Elazığ earthquake occurred Turkey’s Eastern region, were presented, and possible solutions were suggested. Moreover, the effects of the infill walls on the behavior of structures under static and dynamic load cases are discussed that experienced in these earthquakes. Damages are classified according to formations such as in-plane or out-of-plane, evaluations and the results obtained from the discussions are presented for each category.
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Jian, Shikai, Li-Yun Fu, Zonghu Liao, Wubing Deng, and Qizhen Du. "Elastic characteristics of fault damage zones within superdeep carbonates in Tarim Basin, Northwest China." Journal of Geophysics and Engineering 19, no. 4 (July 9, 2022): 650–62. http://dx.doi.org/10.1093/jge/gxac040.
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Abstract Superdeep fault-karst carbonate reservoirs discovered over 7 km deep are controlled by strike-slip fault zones and karst collapses in Tarim Basin, Northwest China. The resulting fracture-cave system provides favorable migration channels and reservoir spaces for hydrocarbon, while the characterization of the internal fault structures remains enigmatic. Based on seismic imaging data, we conducted an integrated study on fault damage zones by seismic curvature attributes, velocity anisotropies, and seismic attenuations. The results show that three typical fault-zone patterns can be identified in the study area, including paratactic multiple fault cores, interactive fault cores and one primary-several subsidiary fault cores. These typical patterns can be clearly characterized via curvature attributes. The elastic characteristics of fault damage zones are significantly affected by seismic frequencies, which are manifested from velocity anisotropies and seismic attenuations. The maximum seismic attenuation occurs along with the orientation of fault cores. There is a strong anisotropic characteristic of P-wave phase velocity with incident angle of three fault-zone models. It appears that seismic attributes associated with geological steering are an effective tool for the subsurface characterization of fault damage zones.
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Pei, Yangwen, Douglas A. Paton, Rob J. Knipe, W. Henry Lickorish, Anren Li, and Kongyou Wu. "Field-based investigation of fault architecture: A case study from the Lenghu fold-and-thrust belt, Qaidam Basin, NE Tibetan Plateau." GSA Bulletin 132, no. 1-2 (June 19, 2019): 389–408. http://dx.doi.org/10.1130/b35140.1.
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AbstractThe fault zone architecture of a thrust fault zone is critical for understanding the strain accommodation and structural evolution in contractional systems. The fault architecture is also important for understanding fluid-flow behavior both along and/or across thrust fault zones and for evaluating potential fault-related compartmentalization. Because mesoscale (1–100 m) structural features are normally beyond seismic resolution, high-resolution outcrop in situ mapping (5–10 cm resolution) was employed to study the deformation features of a thrust fault zone located in the Qaidam Basin, northeastern Tibetan Plateau. The excellent exposure of outcrops enables the detailed investigation of the Lenghu thrust fault zone and its architecture. The Lenghu thrust fault, a seismically resolvable fault with up to ∼800 m of throw, exhibits a large variation of fault architecture and strain distribution along the fault zone. Multiple structural domains with different levels of strain were observed and are associated with the fault throw distribution across the fault. Based on previously proposed models and high-resolution outcrop mapping, an updated fault zone model was constructed to characterize the structural features and evolution of the Lenghu thrust. The possible parameters that impact fault architecture and strain distribution, including fault throw, bed thickness, lithology, and mechanical heterogeneity, were evaluated. Fault throw distributions and linkages control the strain distribution across a thrust fault zone, with local folding processes contributing important elements in Lenghu, especially where more incompetent beds dominate the stratigraphy. Mechanical heterogeneity, induced by different layer stacking patterns, controls the details of the fault architecture in the thrust zone. The variations in bed thicknesses and mechanical property contrasts are likely to control the initial fault dips and fault/fracture density. Large fault throws are associated with wide strain accommodation and damage zones, although the relationship between the development and width of the fault zone and the throw accumulation remains to be assessed. By presenting the high-resolution mapping of fault architecture, this study provides an insight into the subseismic fault zone geometry and strain distributions possible in thrust faults and reviews their application to assessments of fault zone behavior.
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Li, Lin, Liping Xian, Chaofan Yao, Deping Guo, and Chengliang Liu. "Numerical Modeling of Seismic Responses and Seismic Measures of Tunnel Crossing a Fault Zone: A Case Study." Advances in Materials Science and Engineering 2020 (April 8, 2020): 1–12. http://dx.doi.org/10.1155/2020/5640561.
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The investigation shows that Longxi Tunnel, across a fault zone, was severely damaged during the 2008 Wenchuan earthquake, China. In this paper, the dynamic time history analysis method is used to study the seismic response characteristics of Longxi Tunnel and the aseismic effect of seismic measures. The interfaces of the fault are simulated by bonded interfaces. The results show that high earthquake intensity, high in situ stress, and fault zone are the main reasons for damage of Longxi Tunnel. The inconsistent motion response between the normal surrounding rocks and surrounding rocks within the fault zone resulted in the damage of Longxi Tunnel, and the maximum displacement difference reaches 50 cm. With the seismic measure by setting shake absorb layer and seismic joints, the tunnel has better performance: the maximum peak internal force of the tunnel structure is reduced by about 26% and the acceleration is reduced by 30%. Seismic measures should not only be considered within fault zones but also extend to adjacent surrounding rocks. In this study, the fault seismic measures of Longxi Tunnel should be no less than 4.0 times the tunnel diameter.
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Tariq, Rizwan, Ibrahim Alhamrouni, Ateeq Ur Rehman, Elsayed Tag Eldin, Muhammad Shafiq, Nivin A. Ghamry, and Habib Hamam. "An Optimized Solution for Fault Detection and Location in Underground Cables Based on Traveling Waves." Energies 15, no. 17 (September 5, 2022): 6468. http://dx.doi.org/10.3390/en15176468.
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Faults in the power system affect the reliability, safety, and stability. Power-distribution systems are familiar with the different faults that can damage the overall performance of the entire system, from which they need to be effectively cleared. Underground power systems are more complex and require extra accuracy in fault detection and location for optimum fault management. Slow processing and the unavailability of a protection zone for relay coordination are concerns in fault detection and location, as these reduce the performance of power-protection systems. In this regard, this article proposes an optimized solution for a fault detection and location framework for underground cables based on a discrete wavelet transform (DWT). The proposed model supports area detection, the identification of faulty sections, and fault location. To overcome the abovementioned facts, we optimize the relay coordination for the overcurrent and timing relays. The proposed protection zone has two sequential stages for the current and time at which it optimizes the current and time settings of the connected relays through Newton–Raphson analysis (NRA). Moreover, the traveling times for the DWT are modeled, which relate to the protection zone provided by the relay coordination, and the faulty line that is identified as the relay protection is not overlapped. The model was tested for 132 kV/11 kV and 16-node networks for underground cables, and the obtained results show that the proposed model can detect and locate the cable’s faults speedily, as it detects the fault in 0.01 s, and at the accurate location. MATLAB/Simulink (DigSILENT Toolbox) is used to establish the underground network for fault location and detection.
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Botter, Charlotte, and Alex Champion. "Seismic attribute analysis of a fault zone in the Thebe field, Northwest shelf, Australia." Interpretation 10, no. 2 (March 14, 2022): T325—T340. http://dx.doi.org/10.1190/int-2021-0145.1.
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Seismic data are one of the main ways to characterize faults in the subsurface. Faults are 3D entities and their internal structure plays a key role in controlling fluid flow in the subsurface. We have aimed to characterize a geologically sound fault volume that could be used for subsurface model conditioning. We introduce an attribute analysis of a normal fault from a high-resolution seismic data set of the Thebe field, offshore northwest Australia. We merge together a series of common attributes for fault characterization: dip, semblance, and tensor (DST), and we also introduce a new total horizontal derivative (THD) attribute to define the edges of the fault zone. We apply a robust statistical analysis of the attributes and fault damage definition through the analysis of 2D profiles along interpreted horizons. Using the THD attribute, we interpret a smaller width of the fault zone and a more straightforward definition of the boundaries than from the DST cube. Following the extraction of this fault volume, we define two seismic facies that are correlated with lithologies extracted from our conceptual model. We observe a wider fault zone at larger throws, which also corresponds to synrift sequence; hence, more complex internal fault damage. Our method provides volumes at adequate scale for reservoir modeling, and therefore could be used as a proxy for property conditioning.
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Chen, Yangpu, Zonghu Liao, Li-Yun Fu, Gang Zhou, Liang Xu, Kurt J. Marfurt, Xinru Mu, and Huayao Zou. "Effect of main frequencies on characterizing fault damage zones using forward modeling and attribute of variance." Interpretation 8, no. 4 (October 12, 2020): SP157—SP165. http://dx.doi.org/10.1190/int-2020-0017.1.
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Faulting processes have created large damage zones with complex structures in the field; however, estimating the width and geometry of such fault structures in the subsurface is challenging due to a lack of data. Seismic attributes (e.g., coherence and variance) from seismic surveys have been used for the characterization of faults, but most cases do not detail the effectiveness of this approach. By using forward modeling and the associated seismic attributes of variance, four fault models of idealized damage zones are characterized and the frequency effect is evaluated on the width estimation of fault damage zones in the subsurface. The main results indicate that (1) the general geometric pattern of damage zones could be identified by using simulated amplitude and seismic variance with main frequencies of 10, 25, and 40 Hz; (2) the estimated widths of damage zones at a low frequency of 10 Hz are larger (up to twofold) than those at frequencies of 25 and 40 Hz; for large damage zones (>400 m), the width is best estimated by a frequency of 25 Hz; and (3) scattering noise and diffraction around the fault are found in data at a high frequency of 40 Hz, which results in width overestimation of the damage zones by approximately 17%. The internal structures are difficult to distinguish as scattering noise and chaotic reflections dominate seismic signals. More factors that may influence the accuracy of damage zone width estimation via seismic attributes, include the bedding thickness, fracture density, and velocity. An in-depth understanding of this approach is useful in the application of seismic variance to characterize fault damage zones that may significantly control the fluid migration in the subsurface.
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Zhao, Yawen, Guanghui Wu, Yintao Zhang, Nicola Scarselli, Wei Yan, Chong Sun, and Jianfa Han. "The Strike-Slip Fault Effects on Tight Ordovician Reef-Shoal Reservoirs in the Central Tarim Basin (NW China)." Energies 16, no. 6 (March 9, 2023): 2575. http://dx.doi.org/10.3390/en16062575.
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The largest carbonate condensate field in China has been found in the central Tarim Basin. Ordovician carbonate reservoirs are generally attributed to reef-shoal microfacies along a platform margin. However, recent production success has been achieved along the NE-trending strike-slip fault zones that intersect at the platform margin. For this contribution, we analyzed the strike-slip fault effects on the reef-shoal reservoirs by using new geological, geophysical, and production data. Seismic data shows that some NE-trending strike-slip faults intersected the NW-trending platform margin in multiple segments. The research indicated that the development of strike-slip faults has affected prepositional landforms and the subsequent segmentation of varied microfacies along the platform margin. In addition, the strike-slip fault compartmentalized the reef-shoal reservoirs into multiple segments along the extent of the platform margin. We show that fractured reef-shoal complexes are favorable for the development of dissolution porosity along strike-slip fault damage zones. In the tight matrix reservoirs (porosity < 6%, permeability < 0.5 mD), the porosity and permeability could be increased by more than 2–5 times and to 1–2 orders of magnitude in the fault damage zone, respectively. This suggests that high production wells are correlated with “sweet spots” of fractured reservoirs along the strike-slip fault damage zones, and that the fractured reservoirs in the proximity of strike-slip fault activity might be a major target for commercial exploitation of the deep Ordovician tight carbonates.
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Ma, Jianke, Jianyi Zhang, Haonan Zhang, and Jing Tian. "Analysis of Bridge Tests on Sandy Overburden Site with Fault Dislocating." Applied Sciences 14, no. 2 (January 19, 2024): 852. http://dx.doi.org/10.3390/app14020852.
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Performance-based seismic design methods for bridges are advancing, yet limited research has explored the damage mechanisms of bridges subjected to extreme seismic effects, such as those near or across faults. To investigate the damage mechanisms under bedrock dislocation and bridge rupture resistance, providing essential insights for the standardized design and construction of bridges in close proximity to seismic rupture sites, we developed a large-scale device to model bridges in the immediate vicinity of tilted-slip strong seismic rupture sites. This included a synchronous bedrock dislocation loading system. Four sets of typical sandy soil modeling tests were concurrently conducted. The results indicate: (1) The overall shear deformation zone of the foundation and surface uneven deformation primarily concentrate the overburdened soil body along the fault dip. The damaged area under the low-dip reverse fault is lighter on the surface and inside the soil body compared to the high-dip-positive fault. (2) The presence of bridges reduces the width of the main rupture zone and avoidance distance to some extent. However, this reduction is not as significant as anticipated. The damage to the bridge pile foundation along the fault dislocation tendency notably leads to the bending damage of the bridge deck. (3) Input parameters for fracture-resistant bridge design (surface rupture zone location, extent, maximum deformation, etc.) can be deduced from the free site. Within the rupture zone, a “fuse” design can be implemented using simply supported girders. Additionally, combining the “fuse” design with simple supported girders on both sides and utilizing simple support beams for “fuse” design within the rupture zone, along with structural “disconnection”, allows for reinforcing measures on the bridge structure’s foundation platform and pile in the soil body.
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He, Xiao, Guian Guo, Qingsong Tang, Guanghui Wu, Wei Xu, Bingshan Ma, Tianjun Huang, and Weizhen Tian. "The Advances and Challenges of the Ediacaran Fractured Reservoir Development in the Central Sichuan Basin, China." Energies 15, no. 21 (November 1, 2022): 8137. http://dx.doi.org/10.3390/en15218137.
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The largest Precambrian gasfield in China has been found in the central Sichuan Basin. It has been assumed as an Ediacaran (Sinian) mound–shoal, microfacies-controlled, dolomite reservoir. However, the extremely low porosity–permeability and heterogeneous reservoir cannot establish high production by conventional development technology in the deep subsurface. For this contribution, we carried out development tests on the fractured reservoir by seismic reservoir description and horizontal well drilling. New advances have been made in recent years: (1) the prestack time and depth migration processing provides better seismic data for strike-slip fault identification; (2) seismic planar strike-slip structures (e.g., en échelon/oblique faults) and lithofacies offset together with sectional vertical fault reflection and flower structure are favorable for strike–slip fault identification; (3) in addition to coherence, maximum likelihood and steerable pyramid attributes can be used to identify small strike-slip faults and for fault mapping; (4) fusion attributes of seismic illumination and structural tensor were used to find fractured reservoir along fault damage zone; (5) horizontal wells were carried out across the strike-slip fault damage zone and penetrated fractured reservoir with high production. Subsequently, a large strike-slip fault system has been found throughout the central intracratonic basin, and the “sweet spot” of the fractured reservoir along the strike-slip fault damage zone is widely developed to be a new favorable domain for high-production development. There is still a big challenge in seismic and horizontal well technology for the economical exploitation of the deep fractured reservoirs. This practice provides new insight in the deep tight matrix reservoir development.
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Boullier, Anne-Marie, Odile Robach, Benoît Ildefonse, Fabrice Barou, David Mainprice, Tomoyuki Ohtani, and Koichiro Fujimoto. "High stresses stored in fault zones: example of the Nojima fault (Japan)." Solid Earth 9, no. 2 (April 26, 2018): 505–29. http://dx.doi.org/10.5194/se-9-505-2018.
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Abstract. During the last decade pulverized rocks have been described on outcrops along large active faults and attributed to damage related to a propagating seismic rupture front. Questions remain concerning the maximal lateral distance from the fault plane and maximal depth for dynamic damage to be imprinted in rocks. In order to document these questions, a representative core sample of granodiorite located 51.3 m from the Nojima fault (Japan) that was drilled after the Hyogo-ken Nanbu (Kobe) earthquake is studied by using electron backscattered diffraction (EBSD) and high-resolution X-ray Laue microdiffraction. Although located outside of the Nojima damage fault zone and macroscopically undeformed, the sample shows pervasive microfractures and local fragmentation. These features are attributed to the first stage of seismic activity along the Nojima fault characterized by laumontite as the main sealing mineral. EBSD mapping was used in order to characterize the crystallographic orientation and deformation microstructures in the sample, and X-ray microdiffraction was used to measure elastic strain and residual stresses on each point of the mapped quartz grain. Both methods give consistent results on the crystallographic orientation and show small and short wavelength misorientations associated with laumontite-sealed microfractures and alignments of tiny fluid inclusions. Deformation microstructures in quartz are symptomatic of the semi-brittle faulting regime, in which low-temperature brittle plastic deformation and stress-driven dissolution-deposition processes occur conjointly. This deformation occurred at a 3.7–11.1 km depth interval as indicated by the laumontite stability domain. Residual stresses are calculated from deviatoric elastic strain tensor measured using X-ray Laue microdiffraction using the Hooke's law. The modal value of the von Mises stress distribution is at 100 MPa and the mean at 141 MPa. Such stress values are comparable to the peak strength of a deformed granodiorite from the damage zone of the Nojima fault. This indicates that, although apparently and macroscopically undeformed, the sample is actually damaged. The homogeneously distributed microfracturing of quartz is the microscopically visible imprint of this damage and suggests that high stresses were stored in the whole sample and not only concentrated on some crystal defects. It is proposed that the high residual stresses are the sum of the stress fields associated with individual dislocations and dislocation microstructures. These stresses are interpreted to be originated from the dynamic damage related to the propagation of rupture fronts or seismic waves at a depth where confining pressure prevented pulverization. Actually, M6 to M7 earthquakes occurred during the Paleocene on the Nojima fault and are good candidates for inducing this dynamic damage. The high residual stresses and the deformation microstructures would have contributed to the widening of the damaged fault zone with additional large earthquakes occurring on the Nojima fault.
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Torabi, Anita, Juan Jiménez-Millán, Rosario Jiménez-Espinosa, Francisco Juan García-Tortosa, Isabel Abad, and Tor S. S. Ellingsen. "Effect of Mineral Processes and Deformation on the Petrophysical Properties of Soft Rocks during Active Faulting." Minerals 10, no. 5 (May 15, 2020): 444. http://dx.doi.org/10.3390/min10050444.
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We have studied damage zones of two active faults, Baza and Padul faults in Guadix-Baza and Granada basins, respectively, in South Spain. Mineral and microstructural characterization by X-ray diffraction and field emission electron microscopy studies have been combined with structural fieldwork and in situ measurements of rock properties (permeability and Young’s modulus) to find out the relation between deformation behavior, mineral processes, and changes in the soft rock and sediment properties produced by fluid flow during seismic cycles. Our results show that microsealing produced by precipitation of dolomite and aragonite along fractures in the damage zone of Baza Fault reduces the permeability and increases the Young’s modulus. In addition, deformation bands formed in sediments richer in detrital silicates involved cataclasis as deformation mechanism, which hamper permeability of the sediments. In the Granada Basin, the calcarenitic rocks rich in calcite and clays in the damage zone of faults associated to the Padul Fault are characterized by the presence of stylolites without any carbonate cement. On the other hand, marly lithofacies affected by faults are characterized by the presence of disaggregation bands that involve cracking and granular flow, as well as clay smear. The presence of stylolites and deformation bands in these rocks reduces permeability.
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Ma, Sujian, Liang Zhang, Dong Wang, XinRong Tan, Sifeng Li, and Yang Liu. "Analysis of Tunnel Lining Failure Mechanism under the Action of Active Fault." Shock and Vibration 2021 (July 20, 2021): 1–11. http://dx.doi.org/10.1155/2021/9918021.
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The underground structure that crosses the active fault will cause more serious damage under the dislocation of the active fault. Relying on an actual tunnel in the southwest mountainous area to establish a three-dimensional finite element model, the failure mechanism of the tunnel under strike-slip and thrust fault dislocation is revealed from the lining deformation, stress distribution, and plastic zone distribution, and the results show that the damage range of the lining distributes in the area of the fracture and the damage effect is greatly affected by the movement amount of the active fault. The lining damage under the active fault dislocation is mainly tensile damage, while the lining under the thrust fault dislocation shows compression damage on both sides of the fracture when there is a fracture with a large dip angle. The development range of plastic zone is positively correlated with the dip angle of the fracture and the amount of movement, and the development range is negatively correlated with the dip angle of the fracture and positively correlated with the amount of dislocation. The plastic zone range can be predicted, and the key monitoring range can be set according to the movement form of the active fault, the dip angle of the fracture zone, and the amount of fault movement.
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Al Kazzaz, Sa’ad Ahmed S., Ibrahim Ismaeel, and Karam Khairullah Mohammed. "Fault detection and location of power transmission lines using intelligent distance relay." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 2 (June 1, 2020): 726. http://dx.doi.org/10.11591/ijpeds.v11.i2.pp726-734.
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The aim of this paper is to design a three-phase distance relay using an adaptive neuro-fuzzy inference system algorithm (ANFIS). The proposed relay is used to protect the power transmission lines where they are subjected to faults continuously. These faults may produce a high electric current which leads to high damage in power system equipment. The relay is used to detect the transmission line faults by measuring the voltage and current values for each phase. The line impedance is then calculated to detect the faults and issue instantaneous trip signal to circuit breaker, to separate the fault zone of the transmission line without affecting the work of other relays. To isolate the faulty line without affecting the other lines within the network the relays were trained using adaptive neuro-fuzzy inference system (ANFIS). The obtained results through this work show that the designated distance relay with (ANFIS) algorithm has the ability to detect the faults occurrence, recognize it from the cases of the disturbance and to isolate only the fault zone without affecting the work of other relays in system.
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Taillefer, Audrey, Roger Soliva, Laurent Guillou-Frottier, Elisabeth Le Goff, Guillaume Martin, and Michel Seranne. "Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France)." Geofluids 2017 (2017): 1–19. http://dx.doi.org/10.1155/2017/8190109.
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The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29°C to 73°C), along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro- and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1) in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2) in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.
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Liberty, Lee M., James St. Clair, and Adam P. McKean. "A Broad, Distributed Active Fault Zone Lies beneath Salt Lake City, Utah." Seismic Record 1, no. 1 (April 1, 2021): 35–45. http://dx.doi.org/10.1785/0320210009.
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Abstract Although the Wasatch fault is currently known to have a high-seismic hazard from motion along range-bounding faults, new seismic data reveal faulted and folded 13,000–30,000-yr-old Lake Bonneville strata beneath Salt Lake City (SLC). Coupled with previous excavation trench, borehole, and other geologic and geophysical observations, we conclude that a zone of latest Pleistocene and/or Holocene faulting and folding kinematically links the East Bench and Warm Springs faults through a 3 km wide relay structure and transfer zone. We characterize faults beneath downtown SLC as active, and these faults may displace or deform the ground surface during an earthquake. Through offset but linked faults, our observations support throughgoing ruptures across faults of the Wasatch fault zone (WFZ) and an elevated risk of earthquake-induced building damage.
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Xu, Shiqing. "Recognizing fracture pattern signatures contributed by seismic loadings." Interpretation 8, no. 4 (July 23, 2020): SP95—SP108. http://dx.doi.org/10.1190/int-2020-0033.1.
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The impacts of seismic loadings to fault zone rocks still are not well understood. Although field and experimental studies have suggested several markers, such as pseudotachylytes and pulverized rocks, for indicating seismic loadings, the corresponding markers of other types or at larger scales still are lacking. Drawing from the results of dynamic ruptures with off-fault damage, we have recognized several additional fracture features that may be used to reflect the involvement of seismic loadings. For strike-slip faults stressed at moderate to high angles, synthetic R shear is more favored during rupture propagation, but pronounced antithetic R′ shear can be generated around the termination end of the rupture. In addition, suitably oriented weak structures off the main fault can further facilitate the activation of R′ shear. For low-angle thrust faults such as subduction zones, splay faults in the form of forethrusts and backthrusts still can be generated above the coseismic rupture zone. These faults show an increased spatial extent toward the updip direction, effectively defining an outer wedge susceptible to pervasive compressional failure over its entire depth range. Moreover, a deeply nucleated megathrust rupture that eventually reaches the trench can sequentially load the frontal wedge in compression and then in extension, with the potential to leave a mixture of triggered reverse and normal faults at the final stage. Because the above results also are supported by many observations, they raise a caution that existing fault models ignoring dynamic effects should be used with care and that seismic loadings must be considered more seriously by future fault zone studies.
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Brinkerhoff, Riley, John McBride, Sam Hudson, Douglas Sprinkel, Ron Harris, Kevin Rey, and Eric Tingey. "Strain partitioning between ductile and brittle stratigraphy." Geosites 50 (September 1, 2022): 1–39. http://dx.doi.org/10.31711/ugap.v50i.109.
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The Sand Wash fault zone is a segmented and discontinuous fault system that strikes northwest to south east in the central part of the Uinta Basin. It is approximately 34 kilometers long with an uncommonly wide damage zone, typically 100 to 200 meters wide. Due to recent, rapid, and large-scale incision by the Green River and its tributaries, the Sand-Wash fault zone is well exposed in several closely spaced canyons. These canyon exposures allow mapping of the lateral relationships through panoramic photographs and surface kinematic descriptions. Most movement on the Sand Wash fault zone occurred in the late Eocene, but minor, more recent movement likely occurred. Evidence for fault timing includes strata-bound, syndepositional movement which occurred during Lake Uinta time (55 to 43 Ma BP) resulting in debris flows, slump blocks, and small (>150 meters diameter) sag basins filled with poorly organized sediments. After lithification, elongate grabens formed with up to 33.5 meters of horizontal extension. Two styles of deformation are present. Brittle rocks, such as sandstone and limestone beds, are intensely fractured and faulted, whereas clay and organic-rich rocks are largely unfractured and unfaulted, with variably folded beds that have experienced some layer-parallel slip. Laterally, deformation is distributed up to 100 meters from the fault core, which is uncommonly large for faults with short lengths and little displacement. Vertically, displacement is concentrated in brittle sandstone and carbonate beds and rare in clay and hydrocarbon-rich units, such as the Mahogany oil-shale zone of the Eocene Green River Formation. The Mahogany oil-shale zone mostly displays ductile flow (granular flow) commonly forming small décollements between overlying and underlying units. Vertical displacement on separate fault segments is generally less than 5 meters and decreases down section, dying out completely around the top of the Mahogany oil-shale zone. In this paper we show evidence for syndepositional deformation along the Sand Wash fault zone, strain partitioning along décollement surfaces, fault surfaces that experience multiple deformational phases, pop-up blocks, and graben development. We also show that deformation on the fault zone is related to extension above a neutral surface of a larger fold. This larger fold is associated with a basement-rooted fault zone that moved during Laramide tectonism as the Uncompahgre uplift developed. The Sand Wash fault zone appears to have many similarities to the larger, and more deeply buried, Duchesne fault zone 25 kilometers to the north, and the more deeply eroded Cedar Ridge fault zone located 30 kilometers to the south. The high-resolution fault model, developed herein, is thus a good proxy for other complex fault zones in the Uinta Basin. Our model will be useful to oil and gas operators as they develop horizontal wells across this and other complex fault zones in the basin.
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Langer, M., E. Tillner, T. Kempka, and M. Kühn. "Effective damage zone volume of fault zones and initial salinity distribution determine intensity of shallow aquifer salinization in geological underground utilization." Hydrology and Earth System Sciences Discussions 12, no. 6 (June 16, 2015): 5703–48. http://dx.doi.org/10.5194/hessd-12-5703-2015.
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Abstract. Injection of fluids into deep saline aquifers causes a pore pressure increase in the storage formation, and thus displacement of resident brines. Via hydraulically conductive faults, brine may migrate upwards into shallower aquifers, and lead to unwanted salinization of potable groundwater resources. In the present study, we investigated different scenarios for a prospective storage site close to the city of Beeskow in the Northeast German Basin by using a 3-D regional scale model (100 km × 100 km × 1.34 km) that includes four ambient fault zones. The focus was on assessing the impact of fault length and the effect of an overlying secondary reservoir as well as model boundary conditions on the potential salinization of shallow groundwater resources. We employed numerical simulations of brine injection as a representative fluid using the simulator TOUGH2-MP. Our simulation results demonstrate that pressure build-up within the reservoir determines the intensity and duration of fluid flow through the faults, and hence salinization of shallower aquifers. Application of different boundary conditions proved that these have a crucial impact on reservoir fluid displacement. If reservoir boundaries are closed, the fluid migrated upwards into the shallow aquifer, corresponds to the overall injected fluid mass. In that case, a short hydraulically conductive fault length and the presence of an overlying secondary reservoir leads only to retardation in brine displacement up to a factor of five and three, respectively. If the reservoir boundaries are open, salinization is considerably reduced: in the presence of a secondary reservoir, 33% of equivalent brine mass migrates into the shallow aquifer, if all four faults are hydraulically open over their entire length, whereas the displaced equivalent brine mass is only 12% for a single fault of two kilometres length. Taking into account the considered geological boundary conditions, the brine originates in maximum from the upper 4 to 298 m of the investigated faults. Hence, the initial salt–freshwater interface present in the fault is of high relevance for the resulting shallow aquifer salinization. The present study demonstrates that the existence of hydraulically conductive faults is not necessarily an exclusion criterion for potential injection sites, because salinization of shallower aquifers strongly depends on initial salinity distribution, location of hydraulically conductive faults and their length as well as geological boundary conditions. These constraints are location specific, and need to be explored thoroughly in advance of any field activity. They provide the basis for scenario analyses and a reliable risk assessment.
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Shi, Xinwei, and Xin Feng. "Numerical Assessment of the Structural Damage of a Composite Lining Water Conveyance Tunnel Subjected to Reverse Fault Conditions." Buildings 12, no. 10 (October 10, 2022): 1647. http://dx.doi.org/10.3390/buildings12101647.
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In this paper, the structural responses and failure characteristics of a new type of water conveyance tunnel lining structure subjected to reverse fault conditions were numerically investigated by considering multiple loads and interaction separation modes between different structural layers. This study proposes a new evaluation standard for the safety level of the damage state of the composite lining water conveyance tunnel. It also discusses the influences of fault dislocation displacement (Δf), dip angle (β), and the mechanical properties of the surrounding rock in the fault fracture zone on the water conveyance tunnel response and damage. The results indicate that the buckling failure of the steel tube under axial compression is the dominant failure mode of the composite lining structure. With increasing fault dislocation displacement, the axial compressive strain and circumferential shear strain of the composite lining are most severely damaged on the sliding plane. With decreasing fault dip angle, the axial compressive strain of the composite lining weakens, while the bending and shear strains increase. The increase in rock stiffness in the fault fracture zone reduces the damage scope but increases the composite lining structural damage severity. Overall, the numerical results of this study provide a better understanding of the failure mode and damage process of composite lining water conveyance tunnels under reverse fault conditions; therefore, this study can serve as a reference for composite lining structure disaster assessments.
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Wu, Jing, Yani Lu, Li Wu, Yanhua Han, and Miao Sun. "Numerical Investigation of Water Inflow Characteristics in a Deep-Buried Tunnel Crossing Two Overlapped Intersecting Faults." Water 15, no. 3 (January 25, 2023): 479. http://dx.doi.org/10.3390/w15030479.
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Because fault core zones and damage zones overlap, when a tunnel crosses the intersecting faults the groundwater flow characteristics of the tunnel-surrounding rock will be different compared to that from a single fault. By using the theory of “Three-district zoning of faults”, an improved Darcy–Brinkman numerical model for a tunnel crossing the intersecting faults was established in this work. Based on the relative vertical positions between the tunnel axis and the intersection center of faults, the underground water seepage field was analyzed at steady-state by solving the improved Darcy–Brinkman equation for the host rock zone and the fault zone. The simulation results show that the flow field around the tunnel is almost unaffected by the relative positions but is mainly dependent on the relative heights. Specifically, the relative position variation of the fault intersection to the tunnel axis has little effect on the pore pressure. In terms of flow velocity, regardless of the relative positions of the fault intersection and the tunnel, the maximum value of flow velocity almost occurs near the bottom of the tunnel excavation face and consistently displays high values within a small distance ahead of the excavation face, and then decreases quickly as the distance increases. Furthermore, the flow velocity changes minimally in the host rock. It will likely encounter the maximum water inflow rate when the tunnel excavation face passes through the intersection. The numerical simulation results can provide a practical reference for predicting water inflow into deep-buried tunnels passing through overlapped intersecting faults.