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1
Forouzesh, Alireza, Mohammad S. Golsorkhi, Mehdi Savaghebi, and Mehdi Baharizadeh. "Support Vector Machine Based Fault Location Identification in Microgrids Using Interharmonic Injection." Energies 14, no. 8 (2021): 2317. http://dx.doi.org/10.3390/en14082317.
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This paper proposes an algorithm for detection and identification of the location of short circuit faults in islanded AC microgrids (MGs) with meshed topology. Considering the low level of fault current and dependency of the current angle on the control strategies, the legacy overcurrent protection schemes are not effective in in islanded MGs. To overcome this issue, the proposed algorithm detects faults based on the rms voltages of the distributed energy resources (DERs) by means of support vector machine classifiers. Upon detection of a fault, the DER which is electrically closest to the fault injects three interharmonic currents. The faulty zone is identified by comparing the magnitude of the interharmonic currents flowing through each zone. Then, the second DER connected to the faulty zone injects distinctive interharmonic currents and the resulting interharmonic voltages are measured at the terminal of each of these DERs. Using the interharmonic voltages as its features, a multi-class support vector machine identifies the fault location within the faulty zone. Simulations are conducted on a test MG to obtain a dataset comprising scenarios with different fault locations, varying fault impedances, and changing loads. The test results show that the proposed algorithm reliably detects the faults and the precision of fault location identification is above 90%.
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KOTHYARI, G. C., R. K. DUMKA, A. P. SINGH, G. CHAUHAN, M. G. THAKKAR, and S. K. BISWAS. "Tectonic evolution and stress pattern of South Wagad Fault at the Kachchh Rift Basin in western India." Geological Magazine 154, no. 4 (2016): 875–87. http://dx.doi.org/10.1017/s0016756816000509.
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AbstractWe describe a study of the E–W-trending South Wagad Fault (SWF) complex at the eastern part of the Kachchh Rift Basin (KRB) in Western India. This basin was filled during Late Cretaceous time, and is presently undergoing tectonic inversion. During the late stage of the inversion cycle, all the principal rift faults were reactivated as transpressional strike-slip faults. The SWF complex shows wrench geometry of an anastomosing en échelon fault, where contractional and extensional segments and offsets alternate along the Principal Deformation Zone (PDZ). Geometric analysis of different segments of the SWF shows that several conjugate faults, which are a combination of R synthetic and R’ antithetic, propagate at a short distance along the PDZ and interact, generating significant fault slip partitioning. Surface morphology of the fault zone revealed three deformation zones: a 500 m to 1 km wide single fault zone; a 5–6 km wide double fault zone; and a c. 500 m wide diffuse fault zone. The single fault zone is represented by a higher stress accumulation which is located close to the epicentre of the 2001 Bhuj earthquake of Mw 7.7. The double fault zone represents moderate stress at releasing bends bounded by two fault branches. The diffuse fault zone represents a low-stress zone where several fault branches join together. Our findings are well corroborated with the available geological and seismological data.
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Sexton, John L., and Harvey Henson Jr. "Interpretation of seismic reflection and gravity profile data in western Lake Superior." Canadian Journal of Earth Sciences 31, no. 4 (1994): 652–60. http://dx.doi.org/10.1139/e94-058.
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The interpretation of 1047 km of seismic reflection data collected in western Lake Superior is presented along with reflection traveltime contour maps and gravity models to understand the overall geometry of the Midcontinent Rift System beneath the lake. The Douglas, Isle Royale, and Keweenaw fault zones, clearly imaged on the seismic profiles, are interpreted to be large offset detachment faults associated with initial rifting. These faults have been reactivated as reverse faults with 3–5 km of throw. The Douglas Fault Zone is not directly connected with the Isle Royale Fault Zone. The seismic data has imaged two large basins filled with more than 22 km of middle Keweenawan pre-Portage Lake and Portage Lake volcanic rocks and up to 8 km of upper Keweenawan Oronto and Bayfield sedimentary rocks. These basins persisted throughout Keweenawan time and are separated by a ridge of Archean rocks and a narrow trough bounded by the Keweenaw Fault Zone to the south. Another fault zone, herein named the Ojibwa fault zone, previously interpreted as the northeastern extension of the Douglas Fault Zone, has been reinterpreted as a reverse fault that closely follows the ridge of Archean rocks. Previous researchers have stated that neighboring segments of the rift display alternating polarity of basins associated with large detachment faults. Accommodation zones have been previously interpreted to exist between rift segments; however, the seismic data do not image a clearly identifiable accommodation zone separating the two basins in western Lake Superior. Thus, the seismic profile may lie directly above the pivot of a scissors-type accommodation fault zone, there is no vertical offset associated with the zone, or the zone does not exist. Seismic data interpretations indicate that application of a simple alternating polarity basin – accommodation zone model is an oversimplification of the complex geological structures associated with the Midcontinent Rift System.
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Onwuka, I. K., O. Oputa, G. C. Diyoke, C. S. Ezeonye, and P. I. Obi. "EFFECTS OF VARYING FAULT IMPEDANCE ON DISTANCE PROTECTION SCHEMES OF 11 KV DISTRIBUTION SYSTEMS." BAYERO JOURNAL OF ENGINEERING AND TECHNOLOGY 18, no. 2 (2023): 71–83. https://doi.org/10.5281/zenodo.14520847.
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Distance protection schemes are used in the protection of transmission and distribution lines and they use distance relay in their operations. The protection scheme is always partitioned into two or more zones and each zone is a certain percentage of the entire length of the line (which may also include the next line). With all things being equal, the tripping of the relays is solely a function of the zones where the fault occurred, that is, the location of the occurrence of the fault. However, it has been shown in this paper through simulations in Power System Computer-Aided Design (PSCAD) that for a LLG fault on the line (in Zone 1), the distance relay/protection system tripped inaccurately in Zone 2 for a fault impedance of 0.1Ω, 0.5Ω and 5Ω and trips accurately in Zone 1 for fault impedance of 1Ω, and 10Ω for the same type of fault and same location. Also, for a fault impedance of 0.1Ω, the system tripped at Zone 1 for LL and 3 phase faults and tripped in Zone 2 for LG and LLG faults for the same fault impedance and at the same location. This indicates that tripping zone in distance protection schemes are not solely dependent on fault locations but also slightly dependent on the fault impedance and type of fault.
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Wang, You Xi, and Guang Zhe Deng. "Numerical Simulation of Vertical Ground Stress Distribution along Fault Trend Direction in a Metal Mine." Applied Mechanics and Materials 204-208 (October 2012): 119–22. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.119.
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The fault breaks continuous ground stress distribution. The rock mass in fault zone is weak and broken, it becomes stress decreasing zone. The paper, which is combined with engineering practice and rock mechanics test, numerically simulates geological environment of fault zones and analyzes faults trend direction influence on ground stress distribution in the metal mine. The results demonstrates that deep faults breaks down the continuity of ground stress distribution, principle stresses in lower wall of faults are smaller than it in hanging wall while high deep ground stresses are in cross district of hanging-wall of fault-zone and ore bed
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Kirkwood, Donna, and Michel Malo. "Across-strike geometry of the Grand Pabos fault zone: evidence for Devonian dextral transpression in the Quebec Appalachians." Canadian Journal of Earth Sciences 30, no. 7 (1993): 1363–73. http://dx.doi.org/10.1139/e93-117.
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The principal faults of southeastern Gaspé Peninsula in Quebec consist of a central high-strain zone that is characterized by mainly ductile deformation structures and bordered by low-strain zones each dominated by brittle deformation structures. The overall geometry of shear fractures within the low-strain zones is quite similar to the expected geometry of Riedel shear fractures. The brittle structures overprint the dominant C–S-type fabric of the high-strain zone, which implies that brittle deformation outlasted ductile deformation. The asymmetry of local micro- to meso-scale deformation features along the fault zones reflects the non-coaxiality of the shear. Other features described within the fault zone (stylolitic cleavage, shear bands, and reverse faults) are evidence for a component of shortening perpendicular or oblique to the fault zone. The geometry of the Grand Pabos fault zone (GPFZ), a major fault of southern Gaspé, indicates that deeper seated fault rocks (high-strain zone) have been brought up to higher crustal levels and are presently in contact with brittlely deformed fault rocks (low-strain zone). The proposed model for the evolution of the GPFZ involves Early to Late Devonian, dextral, transcurrent movement accompanied by relatively minor amounts of vertical slip within a dextral transpressive regime. The main pulse of the Acadian orogeny in Gaspé is restricted to the Devonian and therefore occurred later than elsewhere in the Canadian Appalachians.
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Ichinose, Gene A., Kenneth D. Smith, and John G. Anderson. "Moment tensor solutions of the 1994 to 1996 Double Spring Flat, Nevada, earthquake sequence and implications for local tectonic models." Bulletin of the Seismological Society of America 88, no. 6 (1998): 1363–78. http://dx.doi.org/10.1785/bssa0880061363.
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Abstract The 12 September 1994 Mw 5.8 Double Spring Flat, Nevada, earthquake initiated at the intersection of a northeast- and northwest-striking set of conjugate faults within an overlapping zone between the Genoa and Antelope Valley fault zones, of the eastern Sierra Nevadan range frontal fault system. The mainshock ruptured on the northeast-striking fault plane. Eight days after the mainshock, the aftershock activity migrated from the mainshock fault plane to the northwest-striking conjugate fault. Over the next 2 years, aftershocks migrated southward onto another set of conjugate faults and then onto the Antelope Valley fault zone. The focal mechanisms of 17 M > 4 aftershocks were estimated from a time-domain moment tensor inversion using regional broadband data. The T axis (minimum stress direction) is oriented east-west (N80°E to N100°E) for the (M > 4) events as is, commonly observed along the eastern Sierra Nevadan range front in northwestern Nevada. From these results, we make some general points that can be considered in seismic hazard assessment. The maximum magnitude in overlapping normal fault zone is limited to the size of the overlapping zone. This makes small- to moderate-size (M < 6) strike-slip earthquakes more likely than large range-front (M > 7) earthquakes. The seismicity within this overlapping zone may indicate interseismic strain accumulation from east-west extension mainly through strike-slip deformation. The apparent scarcity of modern normal-faulting earthquakes along the Sierran range-front faults suggests a characteristic model, while a Gutenberg and Richter model for the recurrence behavior of earthquakes applies to the overlap zones between the normal faults. The pattern of seismicity and principle stress directions from the aftershock fault-plane solutions suggest a tectonic model of changing fault geometry for the overlapping zone between the Genoa and Antelope Valley fault zones. Two plausible long-term tectonic outcomes may develop with this model: a normal fault growth model where the overlapping segments of the Genoa and Antelope Valley faults eventually become “hard linked” (form a throughgoing fault) or a normal fault growth model where the overlapping segment of the Genoa fault system grows southward while the Antelope Valley fault is isolated in the formation of new basins and ranges.
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Özsayin, Erman, and Kadir Dirik. "The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extension." Geologica Carpathica 62, no. 4 (2011): 345–59. http://dx.doi.org/10.2478/v10096-011-0026-7.
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The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extensionThe NW-SE striking extensional Inönü-Eskişehir Fault System is one of the most important active shear zones in Central Anatolia. This shear zone is comprised of semi-independent fault segments that constitute an integral array of crustal-scale faults that transverse the interior of the Anatolian plateau region. The WNW striking Eskişehir Fault Zone constitutes the western to central part of the system. Toward the southeast, this system splays into three fault zones. The NW striking Ilıca Fault Zone defines the northern branch of this splay. The middle and southern branches are the Yeniceoba and Cihanbeyli Fault Zones, which also constitute the western boundary of the tectonically active extensional Tuzgölü Basin. The Sultanhanı Fault Zone is the southeastern part of the system and also controls the southewestern margin of the Tuzgölü Basin. Structural observations and kinematic analysis of mesoscale faults in the Yeniceoba and Cihanbeyli Fault Zones clearly indicate a two-stage deformation history and kinematic changeover from contraction to extension. N-S compression was responsible for the development of the dextral Yeniceoba Fault Zone. Activity along this structure was superseded by normal faulting driven by NNE-SSW oriented tension that was accompanied by the reactivation of the Yeniceoba Fault Zone and the formation of the Cihanbeyli Fault Zone. The branching of the Inönü-Eskişehir Fault System into three fault zones (aligned with the apex of the Isparta Angle) and the formation of graben and halfgraben in the southeastern part of this system suggest ongoing asymmetric extension in the Anatolian Plateau. This extension is compatible with a clockwise rotation of the area, which may be associated with the eastern sector of the Isparta Angle, an oroclinal structure in the western central part of the plateau. As the initiation of extension in the central to southeastern part of the Inönü-Eskişehir Fault System has similarities with structures associated with the Isparta Angle, there may be a possible relationship between the active deformation and bending of the orocline and adjacent areas.
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Ma, Bingshan, Jiafu Qi, and Jiawang Ge. "Development of two-phase transfer zones during multiphase rifting and their influence on sedimentation in the Baxian Sag, Bohai Bay Basin, northern China." Geological Magazine 156, no. 11 (2019): 1821–38. http://dx.doi.org/10.1017/s0016756819000190.
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AbstractWe investigate the formation and deformation of transfer zones and their impact on sedimentation during multiphase rifting using a three-dimensional seismic dataset in the Baxian Sag, the onshore part of the Bohai Bay Basin, northern China. The fault system in the study area is dominated by two arcuate, opposing boundary faults, that is, the Niudong and Maxi faults, which form an S-type fault system which does not link together. The fault system and structural-stratigraphic features between the Eocene and Oligocene syn-rift sequences were distinctly different during the Palaeogene rifting. These differences allow us to identify the two-phase transfer zones: (1) a NW–SE-trending Eocene transfer zone linking the NW-tilted Baxian Block and the SE-tilted Raoyang Block , and (2) the N–S-trending Oligocene transfer zone forming along the central part of the S-type fault system between the two inward kinks, and linking S-tilted and N-tilted fault blocks. The two-phase transfer zones comprise transverse boundary fault segments and fault styles which are related to strike-slip motion. The strike-slip faults occurred in the sequence where the transfer zone formed. The transfer zones significantly influenced the syn-rift sediments, drainage catchments and reservoir properties during the periods when they formed, and the two-phase transfer zones represent favourable positions for hydrocarbon accumulation in the Eocene and Oligocene sequences, respectively.
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Fletcher, John M., Orlando J. Teran, Thomas K. Rockwell, et al. "An analysis of the factors that control fault zone architecture and the importance of fault orientation relative to regional stress." GSA Bulletin 132, no. 9-10 (2020): 2084–104. http://dx.doi.org/10.1130/b35308.1.
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Abstract The moment magnitude 7.2 El Mayor–Cucapah (EMC) earthquake of 2010 in northern Baja California, Mexico produced a cascading rupture that propagated through a geometrically diverse network of intersecting faults. These faults have been exhumed from depths of 6–10 km since the late Miocene based on low-temperature thermochronology, synkinematic alteration, and deformational fabrics. Coseismic slip of 1–6 m of the EMC event was accommodated by fault zones that displayed the full spectrum of architectural styles, from simple narrow fault zones (< 100 m in width) that have a single high-strain core, to complex wide fault zones (> 100 m in width) that have multiple anastomosing high-strain cores. As fault zone complexity and width increase the full spectrum of observed widths (20–200 m), coseismic slip becomes more broadly distributed on a greater number of scarps that form wider arrays. Thus, the infinitesimal slip of the surface rupture of a single earthquake strongly replicates many of the fabric elements that were developed during the long-term history of slip on the faults at deeper levels of the seismogenic crust. We find that factors such as protolith, normal stress, and displacement, which control gouge production in laboratory experiments, also affect the architectural complexity of natural faults. Fault zones developed in phyllosilicate-rich metasedimentary gneiss are generally wider and more complex than those developed in quartzo-feldspathic granitoid rocks. We hypothesize that the overall weakness and low strength contrast of faults developed in phyllosilicate rich host rocks leads to strain hardening and formation of broad, multi-stranded fault zones. Fault orientation also strongly affects fault zone complexity, which we find to increase with decreasing fault dip. We attribute this to the higher resolved normal stresses on gently dipping faults assuming a uniform stress field compatible with this extensional tectonic setting. The conditions that permit slip on misoriented surfaces with high normal stress should also produce failure of more optimally oriented slip systems in the fault zone, promoting complex branching and development of multiple high-strain cores. Overall, we find that fault zone architecture need not be strongly affected by differences in the amount of cumulative slip and instead is more strongly controlled by protolith and relative normal stress.
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Damayanti, Cahya, Sismanto Sismanto, Ari Setiawan, and Lina Handayani. "IDENTIFYING THE BASEMENT STRUCTURE OF THE SULA FAULT ZONE IN THE BANGGAI-SULA MICROCONTINENT REGION, MOLUCCA SEA, BASED ON 2D GRAVITY INVERSION MODELLING USING PARTICLE SWARM OPTIMISATION AND 3D MODELLING USING GRABLOX." Rudarsko-geološko-naftni zbornik 40, no. 2 (2025): 137–54. https://doi.org/10.17794/rgn.2025.2.10.
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This study aims to delineate the basement structure of Sula fault zones within the Banggai-Sula Microcontinent Region through the implementation of 2D and 3D gravity inversion modelling. The Sula fault is a consequence of the convergence between the Banggai-Sula Microcontinent and northern regions, or the compression caused by the extrusion of material from the Molucca Sea collision zone to the south. This is an active fault, with a few earthquakes in the last two decades. As a complex active fault, this presents several questions, particularly about the fault’s structure. Residual anomaly data was modelled in two dimensions using Particle Swarm Optimisation method and in three dimensions with Grablox software. The gravity inversion results indicate that the basement depth in the nine profile incision zones, which are perpendicular to the fault zone, range from 120 m to 9308 m. This research region can be separated into two fault zones based on the low-value residual anomalies. Fault zone 1 exhibits a basement depth range of 2843.3 m to 6526.9 m. This region has rock components with a low density ranging from 1.68 g/cm³ to 2.20 g/cm³. Fault zone 2 exhibits a basement depth range of 3716.3 m to 9308.4 m. The geological layer comprises constituent rocks with a low density of 1.24 g/cm³, in contrast to the northern rocks averaging 2.4 g/cm³ and the southern rocks averaging between 2.5 g/cm³ and 2.7 g/cm³. The average depth of faults in fault zones 1 and 2 is 5200 m. The inversion method using PSO can yield estimates for the basement depth of the fault zone. Derivative analysis indicates that the east-west-trending fault structure in fault zone 1 and fault zone 2 aligns with the tectonic characteristics of the Banggai-Sula microcontinent, hence affirming the presence of an east-west fault in the area.
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Arsdale, Roy Van, Jodi Purser, William Stephenson, and Jack Odum. "Faulting along the southern margin of Reelfoot Lake, Tennessee." Bulletin of the Seismological Society of America 88, no. 1 (1998): 131–39. http://dx.doi.org/10.1785/bssa0880010131.
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Abstract The Reelfoot Lake basin, Tennessee, is structurally complex and of great interest seismologically because it is located at the junction of two seismicity trends of the New Madrid seismic zone. To better understand the structure at this location, a 7.5-km-long seismic reflection profile was acquired on roads along the southern margin of Reelfoot Lake. The seismic line reveals a westerly dipping basin bounded on the west by the Reelfoot reverse fault zone, the Ridgely right-lateral transpressive fault zone on the east, and the Cottonwood Grove right-lateral strike-slip fault in the middle of the basin. The displacement history of the Reelfoot fault zone appears to be the same as the Ridgely fault zone, thus suggesting that movement on these fault zones has been synchronous, perhaps since the Cretaceous. Since the Reelfoot and Ridgely fault systems are believed responsible for two of the main-shocks of 1811-1812, the fault history revealed in the Reelfoot Lake profile suggests that multiple mainshocks may be typical of the New Madrid seismic zone. The Ridgely fault zone consists of two northeast-striking faults that lie at the base of and within the Mississippi Valley bluff line. This fault zone has 15 m of post-Eocene, up-to-the-east displacement and appears to locally control the eastern limit of Mississippi River migration. The Cottonwood Grove fault zone passes through the center of the seismic line and has approximately 5 m of up-to-the-east displacement. Correlation of the Cottonwood Grove fault with a possible fault scarp on the floor of Reelfoot Lake and the New Markham fault north of the lake suggests the Cottonwood Grove fault may change to a northerly strike at Reelfoot Lake, thereby linking the northeast-trending zones of seismicity in the New Madrid seismic zone.
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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 (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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Kolyukhin, Dmitriy R., Vadim V. Lisitsa, Maxim I. Protasov, et al. "Seismic imaging and statistical analysis of fault facies models." Interpretation 5, no. 4 (2017): SP71—SP82. http://dx.doi.org/10.1190/int-2016-0202.1.
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Interpretation of seismic responses from subsurface fault zones is hampered by the fact that the geologic structure and property distributions of fault zones can generally not be directly observed. This shortcoming curtails the use of seismic data for characterizing internal structure and properties of fault zones, and it has instead promoted the use of interpretation techniques that tend to simplify actual structural complexity by rendering faults as lines and planes rather than volumes of deformed rock. Facilitating the correlation of rock properties and seismic images of fault zones would enable active use of these images for interpreting fault zones, which in turn would improve our ability to assess the impact of fault zones on subsurface fluid flow. We use a combination of 3D fault zone models, based on empirical data and 2D forward seismic modeling to investigate the link between fault zone properties and seismic response. A comparison of spatial statistics from the geologic models and the seismic images was carried out to study how well seismic images render the modeled geologic features. Our results indicate the feasibility of extracting information about fault zone structure from seismic data by the methods used.
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Tian, Fei, Jianting Yang, Ming Cheng, et al. "Geometry, kinematics and dynamic characteristics of a compound transfer zone: the Dongying anticline, Bohai Bay Basin, eastern China." Open Geosciences 8, no. 1 (2016): 612–29. http://dx.doi.org/10.1515/geo-2016-0053.
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AbstractThe Dongying anticline is an E-W striking complex fault-bounded block unit which located in the central Dongying Depression, Bohai Bay Basin. The anticline covers an area of approximately 12 km2. The overlying succession, which is mainly composed of Tertiary strata, is cut by normal faults with opposing dips. In terms of the general structure, the study area is located in a compound transfer zone with major bounding faults to the west (Ying 1 fault) and east (Ying -8 and -31 faults). Using three-dimensional seismic data, wireline log and checkshot data, the geometries and kinematics of faults in the transfer zone were studied, and fault displacements were calculated. The results show that when activity on the Ying 1 fault diminished, displacement was transferred to the Ying -8, Ying -31 and secondary faults so that total displacement increased. Dynamic analysis shows that the stress fields in the transfer zone were complex: the northern portion was a left-lateral extensional shear zone, and the southern portion was a right-lateral extensional shear zone. A model of potential hydrocarbon traps in the Dongying transfer zone was constructed based on the above data combined with the observed reservoir rock distribution and the sealing characteristics of the faults. The hydrocarbons were mainly expulsed from Minfeng Sag during deposition periods of Neogene Guantao and Minghuazhen Formations, and migrated along major faults from source kitchens to reservoirs. The secondary faults acted as barriers, resulting in the formation of fault-bound compartments. The high points of the anticline and well-sealed traps near secondary faults are potential targets. This paper provides a reservoir formation model of the low-order transfer zone and can be applied to the hydrocarbon exploration in transfer zones, especially the complex fault block oilfields in eastern China.
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Putra, Ahmad Dedi, Norasiah Sulaiman, Norsyafina Roslan, Habibah Jamil, and Khairunnisa Alias. "Fault Zone Identification for Groundwater Flow Assessment Based On Seismic Reflection Survey Data at the Area of Felda Lepar Utara, Pahang, Malaysia." Journal of Physics: Conference Series 2309, no. 1 (2022): 012037. http://dx.doi.org/10.1088/1742-6596/2309/1/012037.
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Abstract Geological structures such as faults and fractures have an important influence in the process of fluid movement below the surface. The hydraulic behavior in aquifers can be determined by proper characterization of fractures, fault zones and their connectivity. In this study, we concern on detection and identification of fault zones in the groundwater basin to verify whether faults in the basin area connect to the surface, and whether the fault zones occurring serve as conduits or barriers for groundwater to flow. The seismic reflection method with Common Depth Point (CDP) profiling technique has been applied in this study. Through this study, we have identified that several large and small-scale faults were found in the study area. Generally, these large-scale faults cut the bedrock (granodiorite) up to impermeable layer. This large-scale fault group can be a barrier that block the groundwater flow. The fault zone is connected to the surface as evidenced by the presence of normal fault that is clearly observed at the surface. This seismic method is good to apply in this study because it can be used to record deeper subsurface conditions, especially for fault zone detection purposes.
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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 (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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Boncio, Paolo, Francesca Liberi, Martina Caldarella, and Fiia-Charlotta Nurminen. "Width of surface rupture zone for thrust earthquakes: implications for earthquake fault zoning." Natural Hazards and Earth System Sciences 18, no. 1 (2018): 241–56. http://dx.doi.org/10.5194/nhess-18-241-2018.
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Abstract. The criteria for zoning the surface fault rupture hazard (SFRH) along thrust faults are defined by analysing the characteristics of the areas of coseismic surface faulting in thrust earthquakes. Normal and strike–slip faults have been deeply studied by other authors concerning the SFRH, while thrust faults have not been studied with comparable attention. Surface faulting data were compiled for 11 well-studied historic thrust earthquakes occurred globally (5.4 ≤ M ≤ 7.9). Several different types of coseismic fault scarps characterize the analysed earthquakes, depending on the topography, fault geometry and near-surface materials (simple and hanging wall collapse scarps, pressure ridges, fold scarps and thrust or pressure ridges with bending-moment or flexural-slip fault ruptures due to large-scale folding). For all the earthquakes, the distance of distributed ruptures from the principal fault rupture (r) and the width of the rupture zone (WRZ) were compiled directly from the literature or measured systematically in GIS-georeferenced published maps. Overall, surface ruptures can occur up to large distances from the main fault ( ∼ 2150 m on the footwall and ∼ 3100 m on the hanging wall). Most of the ruptures occur on the hanging wall, preferentially in the vicinity of the principal fault trace ( > ∼ 50 % at distances < ∼ 250 m). The widest WRZ are recorded where sympathetic slip (Sy) on distant faults occurs, and/or where bending-moment (B-M) or flexural-slip (F-S) fault ruptures, associated with large-scale folds (hundreds of metres to kilometres in wavelength), are present. A positive relation between the earthquake magnitude and the total WRZ is evident, while a clear correlation between the vertical displacement on the principal fault and the total WRZ is not found. The distribution of surface ruptures is fitted with probability density functions, in order to define a criterion to remove outliers (e.g. 90 % probability of the cumulative distribution function) and define the zone where the likelihood of having surface ruptures is the highest. This might help in sizing the zones of SFRH during seismic microzonation (SM) mapping. In order to shape zones of SFRH, a very detailed earthquake geologic study of the fault is necessary (the highest level of SM, i.e. Level 3 SM according to Italian guidelines). In the absence of such a very detailed study (basic SM, i.e. Level 1 SM of Italian guidelines) a width of ∼ 840 m (90 % probability from "simple thrust" database of distributed ruptures, excluding B-M, F-S and Sy fault ruptures) is suggested to be sufficiently precautionary. For more detailed SM, where the fault is carefully mapped, one must consider that the highest SFRH is concentrated in a narrow zone, ∼ 60 m in width, that should be considered as a fault avoidance zone (more than one-third of the distributed ruptures are expected to occur within this zone). The fault rupture hazard zones should be asymmetric compared to the trace of the principal fault. The average footwall to hanging wall ratio (FW : HW) is close to 1 : 2 in all analysed cases. These criteria are applicable to "simple thrust" faults, without considering possible B-M or F-S fault ruptures due to large-scale folding, and without considering sympathetic slip on distant faults. Areas potentially susceptible to B-M or F-S fault ruptures should have their own zones of fault rupture hazard that can be defined by detailed knowledge of the structural setting of the area (shape, wavelength, tightness and lithology of the thrust-related large-scale folds) and by geomorphic evidence of past secondary faulting. Distant active faults, potentially susceptible to sympathetic triggering, should be zoned as separate principal faults. The entire database of distributed ruptures (including B-M, F-S and Sy fault ruptures) can be useful in poorly known areas, in order to assess the extent of the area within which potential sources of fault displacement hazard can be present. The results from this study and the database made available in the Supplement can be used for improving the attenuation relationships for distributed faulting, with possible applications in probabilistic studies of fault displacement hazard.
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Seminsky, К. Zh, A. S. Cheremnykh, O. M. Khlystov, and G. G. Akhmanov. "Fault Zones and Stress Fields in the Sedimentary Fill of Lake Baikal: Tectonophysical Approach for Seismic and Hydroacoustic Data Interpretation." Russian Geology and Geophysics 63, no. 7 (2022): 840–55. http://dx.doi.org/10.2113/rgg20204293.
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Abstract —This paper presents a schematic summary of comprehensive analysis of seismic, reflection profiling, and hydroacoustic data on faults which caused sediment deformation in the central segment of the Central Baikal basin. According to the tectonophysical analysis results, the fault pattern within sediment fill has been recognized as zone-block, i.e., it represents a network of high-density fracture zones limiting weakly deformed blocks. The structure of large NE-trending fault zones (Olkhon, Beregovoy, Gydratny, and Svyatoy Nos) is controlled by main fault planes (or their segments) bounded by subsidiary faults. Geomorphic expression of NW cross faults in the sedimentary cover as broad zones of smaller-scale fractures accounts for early stages of the evolution of basement faults. In a longitudinal direction, they divide the basin into large fragments. The zone–block structure of the sedimentary strata was developed in different stress regimes: strike-slip and extension at the early and late orogenic rifting stages, respectively. At the modern stage of tectogenesis, the established network of fault zones controls the gaseous (including hydrate formation) and seismic activity expression in the subsurface. Hydrate-bearing mud volcanoes and seeps are confined to major faults, while earthquake epicenters are confined to fault zones and form clusters at junctions of large NE-trending faults with NW-oriented extension zones and E–W left-lateral strike-slip faults.
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Erickson, S. Gregg. "Deformation of shale and dolomite in the Lewis thrust fault zone, northwest Montana, U.S.A." Canadian Journal of Earth Sciences 31, no. 9 (1994): 1440–48. http://dx.doi.org/10.1139/e94-127.
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The Lewis thrust fault zone at Marias Pass, northwest Montana, is an example of a fault zone in which hanging-wall dolomite and footwall shale deformed at relatively shallow levels (~7 km). Fabric in the fault zone depends on the rock type. Deformation of dolomite involved coalescence and widening by cataclasis of fractures, formation of anastomosing cataclasite zones that isolate less deformed clasts, and rounding and reduction in size of clasts to produce random-fabric cataclasite. Whereas dolomite deformed by progressive widening of cataclasite zones, shale deformation localized along ultracataclasite zones and slip surfaces that bound shale duplexes. Fault rocks that include both footwall shale and hanging-wall carbonate are characterized by isoclinal, intrafolial folds and a foliation that is defined by alternating shale- and carbonate-rich bands, elongate lenses of carbonate, and preferred orientation of phyllosilicates. Calcitization and subsequent solution of hanging wall rocks incorporated in the shale contributed to the development of this planar fabric. Lenses of hanging-wall carbonate were isolated in footwall shale by the emplacement of shale tongues into the hanging wall along mesoscopic faults. Displacement on the Lewis fault was accommodated by deformation of both dolomite and shale. Grain-size reduction of dolomite, mixing of dolomite and shale, and calcitization of dolomite in the fault zone may have enhanced diffusional processes in the carbonate and thereby weakened the fault zone.
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Sibson, Richard H. "Dual-Driven Fault Failure in the Lower Seismogenic Zone." Bulletin of the Seismological Society of America 110, no. 2 (2020): 850–62. http://dx.doi.org/10.1785/0120190190.
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ABSTRACT Frictional instability leading to fault rupture may be driven by increasing differential stress or by increases in pore-fluid pressure within the rock mass. Geological evidence (from hydrothermal vein systems in exhumed faults) together with geophysical information around active faults support the localized invasion of near lithostatically overpressured hydrothermal fluids, derived from prograde metamorphism at greater depths, into lower portions of the crustal seismogenic zone at depths of about 10–15 km (250°C&lt;T&lt;350°C). This is especially true of compressional–transpressional tectonic regimes that lead to crustal thickening and dewatering and are better at containing overpressure. Extreme examples are associated with areas undergoing active compressional inversion where existing faults, originally formed as normal faults during crustal extension, undergo reverse-slip reactivation during subsequent shortening though poorly oriented for reactivation. Extreme fault-valve action is likely widespread in such settings with failure driven by a combination of rising fluid pressure in the lower seismogenic zone lowering fault frictional strength, as well as by rising tectonic shear stress—dual-driven fault failure. Localized overpressure affects rupture nucleation sites, but dynamic rupturing may extend well beyond the regions of intense overpressuring. Postfailure, enhanced fracture permeability along fault rupture zones promotes fault-valve discharge throughout the aftershock period, increasing fault frictional strength before hydrothermal sealing occurs and overpressures begin to reaccumulate. The association of rupture nucleation sites with concentrated fluid overpressure is consistent with selective invasion of overpressured fluid into the roots of major fault zones and with nonuniform spacing of major vein systems along exhumed brittle–ductile shear zones.
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Mishra, Chandra Sekhar, Ranjan Kumar Jena, Pampa Sinha, et al. "Optimized Fault Detector Based Pattern Recognition Technique to Classify and Localize Electrical Faults in Modern Distribution Systems." International Journal of Robotics and Control Systems 4, no. 3 (2024): 1135–57. http://dx.doi.org/10.31763/ijrcs.v4i3.1474.
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This research presents a method that integrates artificial neural networks (ANN) and discrete wavelet transform (DWT) to identify and classify faults in large power networks, as well as to pinpoint the zones where these faults occur. The objective is to enhance reliability and safety by accurately detecting and categorizing electrical faults. To manage the computational demands of processing the extensive and complex data from the power system, the network is divided into optimal zones, each made visible for fault detection. Niche Binary particle swarm optimization (NBPSO) is employed to place the fault detectors (FD) in each zone. This allows for precise measurement of fault voltage and current phasors without significant cost. The ANN module is tasked with identifying the fault area and locating the exact fault within that zone, as well as classifying the specific type of fault. Discrete Wavelet Transform is used for feature extraction, and a phase locked loop (PLL) is used for load angle computation. The proposed method's validity has been tested on the IEEE-33 bus distribution network.
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Madabhushi, Sriram, and Pradeep Talwani. "Fault plane solutions and relocations of recent earthquakes in Middleton Place Summerville Seismic Zone near Charleston, South Carolina." Bulletin of the Seismological Society of America 83, no. 5 (1993): 1442–66. http://dx.doi.org/10.1785/bssa0830051442.
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Abstract The Middleton Place Summerville Seismic Zone (MPSSZ), located about 20 km northwest of Charleston is the most active seismic zone in South Carolina. Between 1980 and 1991, 58 events with Md 0.8 to 3.3 were recorded in MPSSZ. They lie in a diffuse area of 11 km by 14 km of which over two-thirds are located in a narrow 5 km by 6-km zone. The hypocentral depths range from 2 to 11 km with over 90% deeper than 4 km. Single fault plane solutions were obtained for 35 events. Based on the focal mechanisms the earthquakes were grouped into five subsets. The mean P-axis of all fault plane solutions is oriented N63°E, in general agreement with the direction of SHmax obtained from in situ stress measurements. Of the 35 events, 18 are associated with reverse faulting on NW - SE striking and SW dipping fault planes. These events were inferred to be associated with the Ashley River fault zone, which is not a planar feature, but is composed of short segments of varying strikes (N20°W to N70°W) and dips (40° to 70°SW). Eleven events were associated with strike-slip motion on NNE - SSW striking vertical faults and with thrust faulting on N - S oriented faults dipping to the west, respectively. These two sets are identified as being parts of the Woodstock fault zone. The concentrated zone of seismicity included events associated with both the ARF and WF zones suggesting that it is at the intersection of these two fault zones.
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Xu, Cao, Cao Xiaoshan, Han Tielin, and Ru Yan. "Analysis of the Influence of Fault Fracture Zone on Mining Response Based on FDM-DEM Coupling." Geofluids 2022 (June 21, 2022): 1–16. http://dx.doi.org/10.1155/2022/2648144.
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Fault slip will cause a change in mining stress at the longwall face, which will cause adverse effects. In this study, on the basis of Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) and Particle Flow Code in 3 Dimensions (PFC3D), the sliding of the fault fracture zone and its impact on the longwall working face were analyzed. The rock mass of the fault fracture zone with a certain thickness was constructed using rigid random model particles. The coupling between the wall element of PFC3D and the zone element of the continuous medium in the software was used to realize the transmission of force and displacement, and the interaction between the fault fracture zone and the working face was studied. The influence of the slip of different fault zone positions on the fault and working face was also explored using the method of externally disturbing the fracture zone of the fault. The numerical results showed that as the distance between the fault and the working face continued to decrease, the peak stress concentration in front of the longwall face first increased, then decreased, and gradually shifted to the vicinity of the fault zone. The stress mutation and fault slip occurred within a certain distance of the longwall face from the fault. When fault slip activation begins, the stress near the fault zone showed a sudden change of varying degrees with the advancement of the longwall face. This sudden change was caused by the influence of mining activities from the activation distance of the rock in the fault fracture zone and the rolling extrusion of the rock mass in the fracture zone. When the fault zone closer to the working face was disturbed, the influence on the fault zone and longwall face was greater. When the fault zone near the coal seam was disturbed, the rock mass and working face near the fault zone brought different degrees of dynamic responses, which were mostly instantaneous and had high frequency and amplitude. The results of this research could help in the mining of longwall mining affected by fault zones and have a certain guiding role in coal mining before crossing faults.
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Rivas-Medina, Alicia, Belen Benito, and Jorge Miguel Gaspar-Escribano. "Approach for combining fault and area sources in seismic hazard assessment: application in south-eastern Spain." Natural Hazards and Earth System Sciences 18, no. 11 (2018): 2809–23. http://dx.doi.org/10.5194/nhess-18-2809-2018.
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Abstract. This paper presents a methodological approach to seismic hazard assessment based on a hybrid source model composed of faults as independent entities and zones containing residual seismicity. The seismic potential of both types of sources is derived from different data: for the zones, the recurrence model is estimated from the seismic catalogue. For fault sources, it is inferred from slip rates derived from palaeoseismicity and GNSS (Global Navigation Satellite System) measurements. Distributing the seismic potential associated with each source is a key question when considering hybrid zone and fault models, and this is normally resolved using one of two possible alternatives: (1) considering a characteristic earthquake model for the fault and assigning the remaining magnitudes to the zone, or (2) establishing a cut-off magnitude, Mc, above which the seisms are assigned to the fault and below which they are considered to have occurred in the zone. This paper presents an approach to distributing seismic potential between zones and faults without restricting the magnitudes for each type of source, precluding the need to establish cut-off Mc values beforehand. This is the essential difference between our approach and other approaches that have been applied previously. The proposed approach is applied in southern Spain, a region of low-to-moderate seismicity where faults move slowly. The results obtained are contrasted with the results of a seismic hazard method based exclusively on the zone model. Using the hybrid approach, acceleration values show a concentration of expected accelerations around fault traces, which is not appreciated in the classic approach using only 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 (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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Reitherman, Robert. "The Effectiveness of Fault Zone Regulations in California." Earthquake Spectra 8, no. 1 (1992): 57–77. http://dx.doi.org/10.1193/1.1585670.
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In 1990 a study was completed for the California Division of Mines and Geology on the effectiveness of California's fault zone regulations (the Alquist-Priolo Special Studies Zones Act and associated policies and activities). The Act, passed in 1972, instituted the following elements of a statewide mandatory approach to dealing with the hazard of surface fault rupture: state mapping of fault zones (Special Study Zones) where active faults are suspected; local government imposition of the requirement of a geologic study on new building projects within these Zones (with some single family dwellings and low-occupancy structures exempt); review procedures for the studies submitted by an applicant's geologist; prohibition of the siting of projects on active faults; notification of real estate purchasers that a property is located within a Zone. This paper presents the results of that evaluation and comments more broadly on applying the Alquist-Priolo model to other regions and to other geologic hazards.
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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 (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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Tariq, Rizwan, Ibrahim Alhamrouni, Ateeq Ur Rehman, et al. "An Optimized Solution for Fault Detection and Location in Underground Cables Based on Traveling Waves." Energies 15, no. 17 (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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Kamble, Vijaykumar S., Prabodh Khampariya, and Amol A. Kalage. "A Survey on the Development of Real-Time Overcurrent Relay Coordination Using an Optimization Algorithm." NeuroQuantology 20, no. 5 (2022): 74–85. http://dx.doi.org/10.14704/nq.2022.20.5.nq22150.
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The current work is a survey on the development of real-time overcurrent relay coordination utilizing an optimization approach. Overcurrent relays are a safeguard commonly used in transmission and distribution networks owing to their low cost. Depending on the operating conditions and the location of the faults, load or fault currents in a mesh system may loop in or out of the protective zone of the overcurrent relay. As a result, directional overcurrent relays are employed to determine whether the fault is inside or outside the protective zone. The goal of overcurrent relay coordination is to find settings that minimize operating time for failures within the protective zone. In addition to this it provides scheduled backup for relays in neighbouring zones that has been pre-specified. As an outcome, the highest possible fault current observed by the relay must be greater than maximum fault currents in its protective zone detected in zones close by.
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Tang, Qingsong, Shuhang Tang, Bing Luo, et al. "Seismic Description of Deep Strike-slip Fault Damage Zone by Steerable Pyramid Method in the Sichuan Basin, China." Energies 15, no. 21 (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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Johnson, Jeffrey A. "Off-fault Deformation Associated with Strike-slip Faults." Environmental and Engineering Geoscience 24, no. 4 (2018): 375–84. http://dx.doi.org/10.2113/eeg-2030.
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Abstract Habitable buildings can be protected from surface fault rupture by establishing structure “setback zones” similar in purpose to legally mandated zones in California and Utah. But post-earthquake surveys of offset and warped linear cultural features, believed to have been straight prior to the event, demonstrate that potentially damaging inelastic strains or off-fault deformation can extend tens of meters beyond the principal slip zone of strike-slip surface fault ruptures. Setback zones designed to also mitigate off-fault deformation are likely to be prohibitively wide, indicating the need for structural and geotechnical engineering solutions to accommodate the potentially damaging strains within adequate design buffers. This study analyzes nine strike-slip surface fault ruptures between 1906 and 2014 and develops a simplified procedure to quantify off-fault deformation based on earthquake magnitude and distance from the principal slip zone of strike-slip faults.
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LIU, Jiawei, Guanghui WU, Qingsong TANG, Yonghong WU, Wenjin ZHANG, and Zhongyu ZHAO. "Effects of Intracratonic Strike‐slip Fault on the Differentiation of Carbonate Microfacies: A Case Study of a Permian Platform Margin in the Sichuan Basin (SW China)." Acta Geologica Sinica - English Edition 98, no. 4 (2024): 936–54. http://dx.doi.org/10.1111/1755-6724.15203.
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AbstractIn intracratnoic basins, the effect of strike‐slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three‐dimensional seismic data, this study presents a comprehensive analysis of the Permian carbonate platform and strike‐slip faults in the southwestern Kaijiang‐Liangping trough of the Sichuan Basin. The relationship between strike‐slip faults and Permian carbonate microfacies is investigated. The results reveals the existence of a NW‐trending strike‐slip fault zone along the platform margin, exhibiting clear segmentation. The western side of the study area exhibits a rimmed platform margin characterized by type I reefs, which corresponds to the presence of a large‐scale strike‐slip fault zone. In contrast, the eastern side is characterized by a no‐rimmed and weak rimmed platform margin, accompanied by type II reefs, which align with smaller strike‐slip fault zones. It was found that the strike‐slip fault had some effects on the platform and reef‐shoal complex of the Permain Changxing Formation. First, the platform was divided by strike‐slip fault into three segments to show rimmed, week rimmed and no‐rimmed platform. Second, reef‐shoal complex devolped along the faulted high position in the strike‐slip fault zone, and separated by faulted depression. Third, strike‐slip faults can offset or migrated the reef‐shoal complex and platform margin. Additionally, the thickness of the platform margin varies across strike‐slip fault zone, which is related to the activity of strike‐slip faults. The strike‐slip faults affect the microfacies by controlling the pre‐depositional paleotopography. This case suggests that the strike‐slip faults play a crucial role in the diversity and distribution of carbonate microfacies in the intracratonic 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 (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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Khavari, Saeid, Rahman Dashti, Hamid Reza Shaker, and Athila Santos. "High Impedance Fault Detection and Location in Combined Overhead Line and Underground Cable Distribution Networks Equipped with Data Loggers." Energies 13, no. 9 (2020): 2331. http://dx.doi.org/10.3390/en13092331.
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Power distribution networks are vulnerable to different faults, which compromise the grid performance and need to be managed effectively. Automatic and accurate fault detection and location are key components of effective fault management. This paper proposes a new framework for fault detection and location for smart distribution networks that are equipped with data loggers. The framework supports networks with mixed overhead lines and underground cables. The proposed framework consists of area detection, faulty section identification, and high impedance fault location. Firstly, the faulty zone and section are detected based on the operation of over-current relays and digital fault recorders. Then, by comparing the recorded traveling times at both ends of lines, which are related to the protection zone, the faulty line is identified. In the last step, the location of the fault is estimated based on discrete wavelet transform. The proposed method is tested on a 20 kV 13 node network, which is composed of overhead lines and underground cables. The method is tested in both balanced and unbalanced configurations. The obtained results confirm the advantages of the proposed method compared with the current state-of-the art.
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Baars, D. L. "Basement Tectonic Configuration in Kansas." Bulletin (Kansas Geological Survey), no. 237 (April 16, 2024): 7–9. https://doi.org/10.17161/kgsbulletin.no.237.20414.
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The structure of the Precambrian basement of Kansas, midcontinent USA, is dominated by conjugate north-northeast- and northwest-trending wrench fault zones. North-northeast-trending faults of the Midcontinent Rift System (MRS) extend from Lake Superior across Kansas and into north-central Oklahoma. The fault zone widens from about 100 km (60 mi) in northeast Kansas to more than 160 km (96 mi) in south-central Kansas in a series of horsetail splays. North-northeast-trending structures of the MRS are displaced by about 80 km (48 mi) of dextral offset by the northwest-trending strike-slip fault zone. Apparently penecontemporaneous northwest-trending wrench faults of the Bourbon ArchCentral Kansas uplift cross the state from southeast to northwest, offsetting MRS structures. The two conjugate wrench fault zones are complexly interrelated in central Kansas, where internal synthetic shears complicate axial horsts and grabens of the MRS. The Bourbon Arch is offset approximately 100 km (60 mi) by sinistral slip from the Central Kansas uplift along the MRS. The Humboldt fault zone at the eastern margin of the MRS was not offset significantly by northwest-trending faults, suggesting that the present-day expression of the southward-weakening fault zone was created during Pennsylvanian (Upper Carboniferous) rejuvenation of the basement fabric. Stratigraphic relationships record a history of repeated reactivation in Paleozoic time that strongly affected petroleum entrapment, with an especially strong pulse of uplift during Pennsylvanian time. These rift zones are segments of continental-scale basement lineaments that are fundamental to the structural fabric of the North American basement. The Bourbon Arch-Central Kansas structural lane lies sub-parallel to the Olympic-Wichita lane that extends from southern Oklahoma to the northwest through the Paradox basin of eastern Utah, and the MRS lies sub-parallel to the Colorado Lineament which extends from the Grand Canyon in Arizona to the Lake Superior region. Thus, the basement of the western midcontinent and southern Rocky Mountains consists of large-scale fault zones that delineate suborthogonal basement blocks.
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Wang, Shenglei, Lixin Chen, Zhou Su, et al. "Differential Characteristics of Conjugate Strike-Slip Faults and Their Controls on Fracture-Cave Reservoirs in the Halahatang Area of the Northern Tarim Basin, NW China." Minerals 14, no. 7 (2024): 688. http://dx.doi.org/10.3390/min14070688.
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The X-type strike-slip fault system and weathering crust karst fracture-cave and channel reservoirs were developed in the Halahatang area of the northern Tarim Basin. However, the relationship between the reservoir and the strike-slip fault remains controversial. Based on the core data, and taking an NE-striking strike-slip fault as an example, this paper dissects the karst reservoir from wells along the strike-slip fault damage zone and analyzes the control of scales, properties, and segmentation styles of strike-slip faults on karst reservoirs. The results show that (1) the scale of the strike-slip fault controls the distribution of the reservoir—the wider the fault damage zone, the wider the fracture-cave reservoirs; (2) the transtensional segments of the strike-slip fault are more likely to produce karstification, and the buried-hill area and the interbedded area are controlled by different hydrodynamic conditions to form different types of karst reservoirs; (3) six different parts of the strike-slip fault are conducive to the formation scale of fault fracture zones. This research provides new insight into recognizing karst reservoirs within strike-slip fault damage zones, which can be further applied to predict karst reservoirs controlled by strike-slip faults.
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Marlow, Christopher, Christine Powell, and Randel Cox. "Aeromagnetic Interpretations of the Crittenden County Fault Zone." Seismological Research Letters 92, no. 1 (2020): 494–507. http://dx.doi.org/10.1785/0220200209.
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Abstract The Crittenden County fault zone (CCFZ) is a potentially active fault zone located within 25 km of Memphis, Tennessee, and poses a significant seismic hazard to the region. Previous research has associated the fault zone with basement faults of the eastern Reelfoot rift margin (ERRM) and described it as a northeast-striking, northwest-dipping reverse fault. However, we suggest that there is an incomplete understanding of the fault geometry of the CCFZ and the ERRM in this region due to significant gaps in seismic reflection profiles used to interpret the fault systems. To improve our understanding of the structure of both fault systems in this region, we apply two processing techniques to gridded aeromagnetic data. We use the horizontal gradient method on reduction-to-pole magnetic data to detect magnetic contacts associated with faults as this technique produces shaper gradients at magnetic contacts than other edge detection methods. For depth to basement estimations, we use the analytic signal as the method does not require knowledge of the remnant magnetization of the source body. We suggest that the CCFZ extends approximately 16 km farther to the southwest than previously mapped and may be composed of three independent faults as opposed to a continuous structure. To the northeast, we interpreted two possible faults associated with the ERRM that intersect the CCFZ, one of which has been previously mapped as the Meeman–Shelby fault. If the CCFZ and the eastern rift margin are composed of isolated fault segments, the maximum magnitude earthquake that each fault segment may generate is reduced, thereby, lowering the existing seismic hazard both fault systems pose to Memphis, Tennessee.
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Weidman, Luke, Jillian M. Maloney, and Thomas K. Rockwell. "Geotechnical data synthesis for GIS-based analysis of fault zone geometry and hazard in an urban environment." Geosphere 15, no. 6 (2019): 1999–2017. http://dx.doi.org/10.1130/ges02098.1.
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Abstract Many fault zones trend through developed urban areas where their geomorphic expression is unclear, making it difficult to study fault zone details and assess seismic hazard. One example is the Holocene-active Rose Canyon fault zone, a strike-slip fault with potential to produce a M6.9 earthquake, which traverses the city of San Diego, California (USA). Several strands trend through densely populated areas, including downtown. Much of the developed environment in San Diego predates aerial imagery, making assessment of the natural landscape difficult. To comply with regulations on development in a seismically active area, geotechnical firms have conducted many private, small-scale fault studies in downtown San Diego since the 1980s. However, each report is site specific with minimal integration between neighboring sites, and there exists no resource where all data can be viewed simultaneously on a regional scale. Here, geotechnical data were mined from 268 individual reports and synthesized into an interactive geodatabase to elucidate fault geometry through downtown San Diego. In the geodatabase, fault segments were assigned a hazard classification, and their strike and dip characterized. Results show an active zone of discontinuous fault segments trending north-south in eastern downtown, including active faults outside the mapped regulatory Earthquake Fault Zone. Analysis of fault geometry shows high variability along strike that may be associated with a stepover into San Diego Bay. This type of geodatabase offers a method for compiling and analyzing a high volume of small-scale fault investigations for a more comprehensive understanding of fault zones located in developed regions.
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Fagereng, Å., and A. Beall. "Is complex fault zone behaviour a reflection of rheological heterogeneity?" Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2193 (2021): 20190421. http://dx.doi.org/10.1098/rsta.2019.0421.
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Fault slip speeds range from steady plate boundary creep through to earthquake slip. Geological descriptions of faults range from localized displacement on one or more discrete planes, through to distributed shearing flow in tabular zones of finite thickness, indicating a large range of possible strain rates in natural faults. We review geological observations and analyse numerical models of two-phase shear zones to discuss the degree and distribution of fault zone heterogeneity and effects on active fault slip style. There must be certain conditions that produce earthquakes, creep and slip at intermediate velocities. Because intermediate slip styles occur over large ranges in temperature, the controlling conditions must be effects of fault properties and/or other dynamic variables. We suggest that the ratio of bulk driving stress to frictional yield strength, and viscosity contrasts within the fault zone, are critical factors. While earthquake nucleation requires the frictional yield to be reached, steady viscous flow requires conditions far from the frictional yield. Intermediate slip speeds may arise when driving stress is sufficient to nucleate local frictional failure by stress amplification, or local frictional yield is lowered by fluid pressure, but such failure is spatially limited by surrounding shear zone stress heterogeneity. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.
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Brinkerhoff, Riley, John McBride, Sam Hudson, et al. "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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Cox, Randel Tom, Robert D. Hatcher, Steven L. Forman, et al. "Synthesis of Recent Paleoseismic Research on Quaternary Faulting in the Eastern Tennessee Seismic Zone, Eastern North America: Implications for Seismic Hazard and Intraplate Seismicity." Bulletin of the Seismological Society of America 112, no. 2 (2022): 1161–89. http://dx.doi.org/10.1785/0120210209.
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ABSTRACT Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary seismicity. Modern seismicity records frequent seismic activity in plate-boundary seismic zones, but in fault zones where seismic activity is not frequent, plate boundary or intraplate, resolution of prehistoric earthquake activity is critical for estimating earthquake recurrence interval and maximum expected magnitude. Thus, documenting prehistoric earthquakes is crucial for assessing earthquake hazard posed to infrastructure, including nuclear reactors and large dams. The ∼400 km long eastern Tennessee seismic zone (ETSZ), United States, is the third most active seismic zone east of the Rocky Mountains in North America, although the largest recorded ETSZ earthquake is only Mw 4.8. Ironically, it is the least studied major eastern U.S. seismic zone. Recent ETSZ field surveys revealed an 80 km long, 060°-trending corridor containing northeast-striking Quaternary thrust, strike slip, and normal faults with displacements ≥1 m. It partially overlaps a parallel trend of seismicity that extends 30 km farther southwest, suggesting this active faulting zone may extend ∼110 km within part of the ETSZ. Near Dandridge, Tennessee, a thrust fault in French Broad River alluvium records two earthquakes in the last 40,000 yr. About 50 km southwest near Alcoa, Tennessee, a thrust fault cuts Little River alluvium and records two earthquakes between 15,000 and 10,000 yr ago. About 30 km farther southwest at Vonore, Tennessee, a thrust fault displaces bedrock ≥2 m over colluvium, and alluvium is normal faulted &gt;2 m. This corridor, just west of the Blue Ridge escarpment, overlies a steep gradient in midcrustal S-wave velocities, consistent with a basement fault at hypocentral depths. The corridor faults may be connected to a basement fault or localized coseismic faults above a blind basement fault. Our current data suggest at least two Mw≥6.5 surface rupturing events in the last 40,000 yr.
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Sun, Kai, Chuanyou Li, Mingjian Liang, et al. "Spatial Variations of Late Quaternary Slip Rates along the Ganzi–Xianshuihe Fault Zone in the Eastern Tibet." Remote Sensing 16, no. 14 (2024): 2612. http://dx.doi.org/10.3390/rs16142612.
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The Ganzi–Xianshuihe Fault Zone is a large-scale sinistral strike-slip fault zone on the eastern Tibet. As the boundary fault zone of the Bayankala Block and the Chuandian Block, it controls the clockwise rotation of the southeastern Tibet. However, there is still controversy regarding the activity changes between fault zones. Therefore, accurately determining the slip rates of faults in the area is crucial for characterizing regional plate motions and assessing associated seismic hazards. We focused on studying four fault segments near the Ganzi–Xianshuihe Fault Zone, including the Manigango, Ganzi, Luhuo, and Daofu segments. In each segment, we selected typical sinistral piercing points and carried out Unmanned Aerial Vehicle (UAV) photogrammetry to obtain high-resolution terrain data. We utilized LaDiCaoz_V2.2 and GlobalMapper software (LaDiCaoz_V2.2 and Global Mapper v17.0) to measure the offsets, together with optically stimulated luminescence (OSL) dating, to constrain the timing of fault activity. The estimated slip rates for the Manigango, Ganzi, Luhuo, and Daofu segments are as follows: 9.2 ± 0.75 mm/yr, 9.59 ± 1.7 mm/yr, 4.23 ± 0.66 mm/yr, and 7.69 ± 0.76 mm/yr, respectively. Integrating previous results with slip rates estimated in this study, our analysis suggests the slip rate of the Ganzi–Xianshuihe Fault Zone is around 8–10 mm/year, exhibiting a consistent slip rate from northwest to southeast. This reflects the overall coordination of the movement on the eastern Tibet, with the strike-slip fault zone only controlling the direction of movement.
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Li, Jinxuan, Songfeng Guo, Shengwen Qi, et al. "Spatial Variations of Deformation along a Strike-Slip Fault: A Case Study of Xianshuihe Fault Zone, Southwest China." Applied Sciences 14, no. 6 (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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Treffeisen, Torben, and Andreas Henk. "Elastic and Frictional Properties of Fault Zones in Reservoir-Scale Hydro-Mechanical Models—A Sensitivity Study." Energies 13, no. 18 (2020): 4606. http://dx.doi.org/10.3390/en13184606.
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The proper representation of faults in coupled hydro-mechanical reservoir models is challenged, among others, by the difference between the small-scale heterogeneity of fault zones observed in nature and the large size of the calculation cells in numerical simulations. In the present study we use a generic finite element (FE) model with a volumetric fault zone description to examine what effect the corresponding upscaled material parameters have on pore pressures, stresses, and deformation within and surrounding the fault zone. Such a sensitivity study is important as the usually poor data base regarding specific hydro-mechanical fault properties as well as the upscaling process introduces uncertainties, whose impact on the modelling results is otherwise difficult to assess. Altogether, 87 scenarios with different elastic and plastic parameter combinations were studied. Numerical modelling results indicate that Young’s modulus and cohesion assigned to the fault zone have the strongest influence on the stress and strain perturbations, both in absolute numbers as well as regarding the spatial extent. Angle of internal friction has only a minor and Poisson’s ratio of the fault zone a negligible impact. Finally, some general recommendations concerning the choice of mechanical fault zone properties for reservoir-scale hydro-mechanical models are given.
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Sharp, R. V., K. E. Budding, J. Boatwright, et al. "Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987." Bulletin of the Seismological Society of America 79, no. 2 (1989): 252–81. http://dx.doi.org/10.1785/bssa0790020252.
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Abstract The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9 km; the maximum observed surface slip, 12.5 cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M 6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. Surface rupture associated with the second event occurred along three strands of the zone, here named North and South strands of the Superstition Hills fault and the Wienert fault, for 27 km southeastward from the epicenter. In contrast to the left-lateral faulting, which remained unchanged throughout the period of investigation, the right-lateral movement on the Superstition hills fault zone continued to increase with time, a behavior that was similar to other recent historical surface ruptures on northwest-trending faults in the Imperial Valley region. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. Data for each of the 49 sites were used to compute longitudinal displacement profiles for 1 day and to estimate the final displacement that measured slips will approach asymptotically several years after the earthquakes. The maximum right-lateral slip at 1 day was about 50 cm near the south-central part of the North strand of Superstition Hills fault, and the predicted maximum final displacement is probably about 112 cm at Imler Road near the center of the South strand of the Superstition Hills fault. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is about 54 cm. The average left-lateral slip for the conjugate faults trending northeastward is about 23 cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4 km. The southern half of this fault, south of New River, expressed only vertical displacement on a sinuous trace. The maximum vertical slip by the end of the observation period there was about 25 cm, but its growth had not ceased. Photolineaments southeast of the end of new surface rupture suggest continuation of the Superstition Hills fault zone in farmland toward Mexico.
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Frery, Emanuelle, Laurent Langhi, Julian Strand, and Jeffrey Shragge. "Seismic modelling of fault zones." APPEA Journal 56, no. 2 (2016): 599. http://dx.doi.org/10.1071/aj15105.
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While faults have long been known as primary pathways for fluid migration in sedimentary basins, recent work highlights the importance of fault zone internal architecture, lateral variation, transmissivity, and impact on migration and trapping. The impacts of fault zone architecture and properties on seismic images are investigated to facilitate accurately mapped fault zones, and to predict subseismic flow properties and sealing potential. A wedge-type fault model with a main fault and a synthetic fault displacing a typical North West Shelf siliciclastic succession is used to replicate the geometrical components of a seismic-scale fault. Elastic properties are derived from rock physics models, which are used in a 2D elastic modelling algorithm to produce realistic marine seismic acquisition geometry. These data were subsequently input into a 2D prestack (one-way wave-equation) migration code to produce an interpretable seismic image. Base-case elastic properties are systematically varied; modelling focuses on gouge properties, fractured fault zone material, the sandstone Vp/Vs relationship, and shale-sand velocity contrast. The workflow from geological model building to elastic property substitution and forward seismic modelling is extremely quick and versatile, allowing testing of a wide range of scenarios. So far this approach has yielded valuable insights into internal fault property prediction and interpretation of the fault zone in traditional post-stack seismic datasets. Implications for processing workflow and attenuation of fault shadows are also expected.
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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 (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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Snyder, David B., Brian J. Roberts, and Steven P. Gordey. "Contrasting seismic characteristics of three major faults in northwestern Canada." Canadian Journal of Earth Sciences 42, no. 6 (2005): 1223–37. http://dx.doi.org/10.1139/e05-027.
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The Lithoprobe Slave Northern Cordillera Lithospheric Evolution (SNORCLE) profiles crossed three major tectonic zones of the northwestern Canadian Shield and northern Canadian Cordillera that are diverse in age and in depth of penetration. The oldest (26302590 Ma), the Yellowknife River fault zone, formed as a strike-slip fault in a tensional strain regime. Reflector attenuation or truncations align vertically beneath the fault trace through much of the crust, implying a near-vertical fault plane. The youngest (6010 Ma), the Tintina fault zone, produced cumulative dextral strike-slip displacements of 425 km, perhaps 800 km. Tomographic velocity and ray-trace models of reflection data indicate that several fault splays form a tectonic zone 30 km wide at the surface, but truncations of deeper crustal reflections suggest that the zone thins in the mid-crust and widens near the Moho. This apparent variable width versus depth of the Tintina fault is atypical of major strike-slip faults worldwide. The Teslin fault was an active terrane boundary during accretion of terranes onto North America. Observed reflection geometries indicate that the juxtapositions of highly contrasting metamorphic grades across the Teslin fault are confined to the upper crust along SNORCLE line 3, implying that the fault soles eastward into a mid-crustal detachment at the interpreted top of North American crust. The limited depth extent of the Teslin fault zone is similar to some models of the San Andreas fault and may result from their similar histories as convergent margin structures.
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Zhou, Wei Wei, Wei Feng Wang, and Zhou Jie. "Characteristics of Subtle Fault Zone in Jinhu Sag." Advanced Materials Research 1010-1012 (August 2014): 1399–403. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.1399.
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Subtle fault zones are caused by the weak deformation generated in the sedimentary cover of a sag due to the influence of regional or local stress fields or basement faults. They are too subtle to be easily identified by conventional exploration methods and technologies and are thus usually ignored. Research results prove that there are two basement faults in the Jinhu sag referred to as the NE-and NW-trending basement faults. Parts of the NE-trending basement fault are intense enough to control sag formation and evolution (such as the faults in Yangcun and Shigang, etc.). However, the NW-trending and the rest of the NE-trending basement faults show weak activity and exert little influence on sedimentary cover deformation. These faults merely yield some weakly-deformed trend zones in the sedimentary cover, such as small en-echelon faults, small faults intermittently distributed along fixed directions, buried alluvial fans, zonal or stringy oil-gas traps, or linear structures (such as local folds, narrow and deep half-grabens, etc.). Apart from the two aforementioned types of subtle fault zones, intermittent and stringy NS-trending subtle fault zones are also induced by the EW-trending extrusion stress component in the sag generated by the regional dextral stress field. Keywords: Jinhu sag; basement faults; subtle fault zones; tectonic evolution; en-echelon; trap distribution