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We 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 M w 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.

The influence of inclined faults on the assessment of geodynamic hazard of oil and gas field infrastructure facilities and underground gas storage facilities is discussed. An overview of existing analytical models for the formation of anomalous vertical displacements of the Earth’s surface in the vicinity of inclined faults of the strike-slip and extension types is given. It is shown that, at certain tilt angles, the shape of the distribution curves of vertical displacements in the vicinity of faults of different genesis coincides, which significantly complicates the solution of inverse problems of recent geodynamics of fault zones and the construction of adequate geomechanical models of the formation of a local stress-strain state in the vicinity of these zones. A comparison of model displacement curves with the results of geodynamic monitoring at an underground gas storage facility shows the need for identifying and subsequently selecting displacement anomalies by the type of local displacements (shear or extension) in fault zones for an effective assessment of the geodynamic hazard of field infrastructure facilities located in the vicinity of activated faults.

The Colorado River extensional corridor in southwestern North America is one of Earth's most highly extended regions of continental crust. The central part of the belt includes three imbricate, regionally northeast-dipping extensional detachment faults. The Plomosa detachment fault in the northern Plomosa Mountains in western Arizona, the middle of the three faults, dips northeastward beneath the giant Harcuvar metamorphic core complex. Approximately 1 km of lower Miocene clastic sediments, lava flows, and rock-avalanche breccias were deposited in the northern Plomosa Mountains before initiation of the Plomosa detachment fault and division of the strata into two basins with different stratal accumulations following breakup. Both the detachment-fault lower plate and upper plate were then broken and tilted by normal faults. The upper plate was fragmented into numerous fault blocks and its extension-parallel width was approximately doubled. Application of critical-taper theory to delayed basin fragmentation suggests that southwestward tilting of the land surface and underlying normal faults led to normal-fault initiation and wedge breakup. A seismic-reflection profile northeast of the northern Plomosa Mountains reveals strong, southwest-dipping reflectors that project up dip to metasedimentary tectonites in the southern Buckskin Mountains in the Harcuvar core complex. Restoration of displacement on the Buckskin and Plomosa detachment faults aligns the reflectors and tectonites with a Mesozoic shear zone in the footwall of the Plomosa detachment fault. In this restoration the combined shear zone dips northeastward rather than southwestward and projects up dip to the folds and thrusts exposed to the south and west of the northern Plomosa Mountains. This zone is interpreted as a segment of the Mesozoic Maria fold-and-thrust belt that influenced the geometry of younger detachment faults. The southwest-tilted, mylonitic lower plate of the Plomosa detachment fault includes, at its northern end, Orocopia Schist, which is a Cretaceous subduction complex that is better known from locations farther southwest and closer to the continental margin. Restoration of tectonic extension suggests that Orocopia Schist extends under the Harcuvar core complex and that a buoyant crustal root inherited from Cretaceous thrusting could not have been the cause of core-complex uplift unless the schist was emplaced by a mechanism other than subduction underplating. We propose that the rolling-hinge detachment-fault model combined with a highly mobile deep crust could account for Harcuvar core-complex genesis without a buoyant crustal root.

We integrate previous work on the Hegenshan–Heihe suture with our interpretation of geomagnetic anomaly and seismic reflection data to investigate the role of the Hegenshan–Heihe suture in the evolution of late Mesozoic extensional structures in the Wunite depression of the Erlian Basin. Sags in the Wunite depression present as NE50° trending in the western sector, N0°–NE30° trending in the central sector and NE45° trending in the eastern sector. Our results highlight the importance of the pre-existing Hegenshan–Heihe suture in the evolution of the late Mesozoic rift system and reveal the following details. (1) The NE50° extent sags in the western sector are controlled by the c. NE50°-trending suture. Moreover, the extensional deformation of the reactivated suture during Early Cretaceous time resulted in a further vertical and horizontal extension of major border faults. (2) The N0°–NE30° extent sags in the central sector are influenced by the c. NE75°-trending suture. The sinistral strike-slip component of the reactivated suture during Early Cretaceous time resulted in a strike rotation of major border faults from NEE-trending (following the suture) to NNE-trending. (3) Because of strike-slip deformation, which resulted from the deformation of the reactivated suture accrued in major border faults, light dip-slip deformation led to less vertical offset. (4) The NE45°-trending sags in the eastern sector are controlled by the c. NE45°-trending suture. Moreover, the extensional deformation of the reactivated suture during Early Cretaceous time facilitated a further vertical and horizontal prolongation of major border faults.

The Kure ophiolite in the Sakarya terrane in northern Anatolia is a Penrose-type ophiolite, complete with a sheeted dike complex, and includes well-developed volcanogenic massive sulfide deposits. It is tectonically imbricated along south-directed thrust faults between the Paleozoic, continental basement rocks of the Devrekani Massif (Eurasia) to the north and the Late Triassic-Early Cretaceous subduction-accretion complexes (Tethys) to the south. The ∼5-km-thick crustal lithologies in the ophiolite are crosscut by west-northwest-east-southeast-oriented, extensional ductile-brittle shear zones and normal faults that display hydrothermal mineralization and seafloor alteration effects. The west-northwest-east-southeast-striking sheeted dikes and these extensional fault systems indicate a north-northeast-south-southwest seafloor spreading direction during the magmatic evolution of the ophiolite. The U-Pb zircon dating of a gabbroic rock has revealed a concordant age of 168.8 ± 2 Ma that represents the timing of the igneous construction of the ophiolite. Sandstone units in the ∼3-km-thick turbiditic sedimentary cover of the ophiolite contain Paleoarchean, Neoarchean, and Proterozoic detrital zircons, derived from the Ukrainian shield and the East European Platform, indicating a proximal position of the Kure basin to Eurasia during its development. The Kure ophiolite represents a Middle Jurassic continental backarc basin ophiolite with a Eurasian affinity.

Parwan Gravity Dam is under construction stage in the Jhalawar district of Rajasthan, India. A thin sub-vertical surficial fracture trending N 75°W to S 75°E has been observed in the foundation area of the dam. Geophysical techniques such as electrical resistivity tomography (ERT), seismic refraction tomography (SRT), and multichannel analysis of surface waves (MASW) are utilized extensively in the field of civil engineering, exploration geophysics for the assessment and construction of large-scale infrastructures such as dams. These methods provide critical information about the subsurface conditions without the need of extensive drilling and excavation. The combination of electrical resistivity tomography (ERT), seismic refraction (SR), and multichannel analysis of surface waves (MASW) techniques with the different acquisition parameters have been used to image the extent of shallow subsurface geological structures. Various geophysical Surveys have been carried out along several profiles in the longitudinal direction and along the transverse direction to the fault axis. A total of 13 refraction and resistivity profiles were conducted of which 9 were transverse profiles and 4 were longitudinal profiles. A total of nine MASW profiles were conducted of which 8 are transverse profiles and 1 is a longitudinal profile. In this paper, the subsurface distribution of seismic wave velocity and electrical resistivity have been studied to identify any possible anomalous zone in bedrock and to detect the downward extension of surface fracture of brittle fault using the afore mentioned methods. The vertical and lateral extent of the surface fracture of the fault has been investigated by the analysis of these survey results. The analysis of the results indicates that a very tight and narrow fracture is present in the shallow subsurface.

North-south-directed extension on the South Tibetan Fault System (STFS) played an important role in Himalayan tectonics of the Miocene Period, and it is generally assumed that orogen-perpendicular extension ceased in this orogenic system before the Pliocene. However, previous work in the Annapurna and Dhaulagiri Himalaya of central Nepal revealed evidence for local Pleistocene reactivation of the basal STFS structure in this area (the Annapurna Detachment). New structural mapping and (U-Th)/He apatite and zircon thermochronology in this region further document the significance of Pleistocene N-S extension in this sector of the Himalaya. Patterns of (U-Th)/He accessory-mineral ages are not disrupted across the reactivated segment of the STFS basal detachment, indicating that Pleistocene offset was limited. In contrast, the trace of a N-dipping, low-angle detachment in the hanging wall of the reactivated Annapurna Detachment—formerly linked to the STFS, but here named the Dhaulagiri Detachment—coincides with an abrupt break in the cooling-age pattern in two different drainages ∼20 km apart, juxtaposing Miocene hanging-wall dates against Pleistocene footwall dates. Our observations, combined with previous fission-track data from the region, provide direct evidence for significant N-S extension in the central Himalaya as recently as the Pleistocene.

The Podolsko Complex, Bohemian Massif, is a high-grade dome that is exposed along the suprastructure-infrastructure boundary of the Variscan Orogen and records snapshots of its protracted evolution. The dome is cored by leucocratic migmatites and anatectic granites that enclose relics of high- to ultrahigh-pressure rocks and is mantled by biotite migmatites and paragneisses whose degree of anatexis decreases outwards. Our new U-Pb zircon ages indicate that the leucocratic migmatites were derived from Early Ordovician (c. 480 Ma) felsic igneous crust; the same age is inferred for melting the proto-source of the metapelitic migmatites. The relics of high- to ultrahigh-pressure rocks suggest that at least some portions of the complex witnessed an early Variscan subduction to mantle depths, followed by high-temperature anatexis and syntectonic growth of the Podolsko Dome in the middle crust at c. 340-339 Ma. Subsequently, the dome exhumation was accommodated by crustal-scale extensional detachments. Similar c. 340 Ma ages have also been reported from other segments of the Variscan Belt, yet the significance of this tectonothermal event remains uncertain. Here we conclude that the 340 Ma age post-dates the high-pressure metamorphism; the high temperatures required to cause the observed isotopic resetting and new growth of zircon were probably caused by heat input from the underlying mantle and, finally, the extensional unroofing of the complex requires a minimum throw of about 8-10 km. We use this as an argument for significant Early Carboniferous paleotopography in the interior of the Variscan orogen.

The South Tibetan Detachment (STD) System comprises both ductile shear zones and brittle low-angle extensional faults bounding the upper (northern) margin of the high-grade metamorphic and anatectic rocks of the Greater Himalayan Sequence (GHS). Along the Himalayan chain from Zanskar in the west to Bhutan in the east, leucogranites are restricted to the footwall of the STD and rarely, if ever, intrude across the fault into unmetamorphosed sedimentary rocks of the Tethyan zone. The Manaslu leucogranite (24-19 Ma) was previously thought to be an exception, intruding up as far as the Triassic sediments. We have mapped a newly discovered 350-400-m-thick shear zone of high-strain mylonites along the upper Nar Valley and Pangre glacier (Phu Detachment = STD), west of the Manaslu-Himlung massif, which wraps around the northern (upper) margin of the Manaslu leucogranite. All rocks beneath the Manaslu leucogranite are metamorphosed, and no leucogranites intrude across this shear zone, in common with observations elsewhere along the Himalaya. The age of motion along the STD in the Manaslu region is constrained as being younger than 18 Ma, not older than 24 Ma as previously thought. The Chame Detachment (CD) is a ductile shear zone wholly within the GHS. Pressure-temperature conditions of diopside + K-feldspar + tremolite marbles and calc-silicates, and sillimanite ± kyanite meta-pelites above the CD are similar to conditions for calc-silicates, pelites, and augen gneisses below. We have used structural data and PT constraints in conjunction with stratigraphy to restore the entire GHS in the Annapurna-Manaslu region, prior to the Early Miocene formation of the Manaslu leucogranite and the STD System of normal faults. These Miocene faults and shear zones cut across the earlier Oligocene north-verging folds exposed in the Annapurna range. Ductile shearing along upper levels of the Main Central Thrust zone and along the CD occurred before 21 Ma, and brittle faulting along the STD occurred after 19-18 Ma. Rapid exhumation and cooling of the GHS and Manaslu granite between 18 and 15 Ma was followed by initiation of east-west extension in the Thakkhola Graben north of the STD and propagation of thrusting southward into the Lesser Himalaya.

A distinct spatial relationship between surface faulting, magmatic intrusions and volcanic activity exists in the Aegean continental crust. In this paper, we provide detailed structural observations from key onshore areas, as well as compilations of lineament maps and earthquake locations with focal plane solutions from offshore areas to support such a relationship. Although pluton emplacement was associated with low-angle extensional detachments, the NNE- to NE-trending strike-slip faults also played an important role in localizing the Middle Miocene plutonism, providing ready pathways to deeper magma batches, and controlling the late-stage emplacement and deformation of granites in the upper crust. Additionally, the linear arrangements of volcanic centres, from the Quaternary volcanoes along the active South Aegean Volcanic Arc, are controlled primarily by NE-trending faults and secondarily by NW-trending faults. These volcanic features are located at several extensional settings, which are associated with the main NE-trending faults, such as (i) in the extensional steps or relay zones between strike-slip and oblique-normal fault segments, (ii) at the overlap zones between oblique-normal faults associated with an extensional strike-slip duplex and (iii) at the tip zone of a NE-trending divergent dextral strike-slip zone. The NE trend of volcano-tectonic features, such as volcanic cone alignments, concentration of eruptive centres, hydrothermal activity and fractures, indicates the significant role of tectonics in controlling fluid and magma pathways in the Aegean upper crust. Furthermore, microseismicity and focal mechanisms of earthquakes in the area confirm the activity and present kinematics of these NE- trending faults.