Variations In Tectonic Activity Research Articles

Fault Geometry and Late Quaternary Kinematics Along the Tieluzi Fault: Implications for Tectonic Deformation and Eastward Expansion of the Tibetan Plateau, China

AbstractThe Tieluzi Fault is the largest structure in the East Qinling Mountains, and is considered to be the easternmost continuation of the Altyn Tagh‐Haiyuan‐Qinling Fault System (AHQFS) that allows the eastward extrusion of the Tibetan Plateau and South China Block. We studied the fault geometry and kinematics of the Tieluzi Fault using field investigations, detailed interpretations of high‐resolution satellite imagery and digital elevation models, and late Quaternary dating methods. Paleoseismic investigations indicate that the most recent earthquake along the Tieluzi Fault occurred before 1,500–1,300 cal. BP. Geological and geomorphological observations show that segments west of Lushi County are more active than those to the east. The spatial variations in tectonic activity along the Tieluzi Fault are interpreted to be related to four possible mechanisms: strike change, discontinuity, intersection, and branch. The late Quaternary left‐lateral slip rate is determined to be 0.9 ± 0.1 mm/yr on the Tieluzi Fault. The prominent left‐lateral faulting along the Tieluzi Fault suggests that most of the left‐lateral displacement along the eastern AHQFS has been accommodated by the Tieluzi Fault, which forms the most frontier of the eastward expansion of the Tibetan Plateau. Furthermore, we suggest that the left‐lateral faulting in the East Qinling Mountains is a response to relative eastward motion of the South China block pushed by the Tibetan Plateau with respect to the North China Plain Block. Also, our results indicate that the Tibetan Plateau has undergone a stepwise eastward expansion.

Assessment of relative tectonic activity in the Lar region, Zagros Fold‐Thrust Belt, SW Iran: Insights from geomorphometric analysis

AbstractThe Zagros Fold‐Thrust Belt is a tectonically active region within the Alpine‐Himalayan orogenic system resulting from ongoing convergence between Afro‐Arabian and Central Iranian plates. The presence of various geomorphic features in this region provides an ideal natural case for identifying deformed landforms resulting from active tectonics. The relative tectonic activity along the Lar and Didehban faults within the Zagros Fold‐Thrust Belt, SW Iran was evaluated using six DEM‐derived geomorphic indices: the stream‐gradient index (SL), drainage basin asymmetry (AF), hypsometric integral (HI), valley floor width‐valley height ratio (Vf), drainage basin shape (Bs), and mountain‐front sinuosity (Smf). These indices were combined to yield the relative active tectonics index (Iat) that allows the variation of tectonic activity along the Lar and Didehban faults to be related to variations in rates of incision, tectonic tilting and uplift. This variable tectonic activity was characterized by different Iat values along the faults. The low to high relative tectonic activity (class 1: 1 < Iat < 1.5, class 2: 1.5 < Iat < 2, class 3: 2 < Iat < 2.5, class 4: 2.5 < Iat) correlates with variable geomorphic features along the faults. The results of this study present an approach for assessing the effects of active tectonics and also for sustainable land use planning over a large area.

Geospatial assessment of active tectonics using SRTM DEM-based morphometric approach for Meghalaya, India

Meghalaya, situated over the Shillong Plateau in the northeastern region of India, is considered a seismo-tectonically active region because of the Indian-Eurasian convergence and rising since the Cenozoic era. The present study aims to identify active deformation zones due to tectonic activity following a morphometric approach. Based on DEM data and GIS techniques, morphometry parameters along with geomorphic indices are obtained which allows the analysis of geomorphic processes responsible for the region’s landscape evolution, and indices of relative active tectonics (IRAT) are calculated by combining them. High drainage density, larger ruggedness number, intermediate to high hypsometric integral values with S/convex-type hypsometric curve, lower valley floor width-to-height ratio and stream sinuosity index values suggesting the region is tectonically active and according to IRAT, the Khasi and Jaintia Hills region (the central and eastern part) of the Meghalaya possesses relatively higher tectonic levels. The variation of tectonic activity is not uniform in the same structural feature and is found to be lower in the western portion and higher towards the east along the same Dauki Fault.

Active tectonics in the Moulay Idriss Massif (South Rifian Ridges, NW Morocco): New insights from geomorphic indices and drainage pattern analysis

The Moulay Idriss Ramp anticlines of the South Rifian Ridges are located in the front of the Moroccan Rif Belt (southern branch of the Arc of Gibraltar) and have accommodated the tectonic escape of this Alpine chain as an active edge, in response to the converging Eurasian and African plates. Nevertheless, recent evidences of this landscape tectonic activity remain poorly defined. We investigated the variations in tectonic activity and evaluated its influence on the landscape evolution, through the application of geomorphic indices including: the mountain front sinuosity, valley floor width-to-height ratio, drainage basin asymmetry factor, hypsometric curves, normalized steepness index, longitudinal river profile, and χ as an indicator of drainage network disequilibrium. Morphotectonic study shows that fault related folds, in the area, produce differential uplift with a relatively high degree of tectonic activity along the eastern part of the massif. The doming process accounts for the elevation of the area, in the Dehar en Nsour salt dome, and this in turn, could be explained as being promoted by the Nzala des Oudayas fault system. On the other hand, the Moulay Idriss fault exerts a strong influence on the morphology of the Fert El Bir anticline inducing the Khoumane river deflection, while other streams exhibit rejuvenation and water divide migration. These new data elucidate the recent tectonic evolution of folds and strike-slip fault systems in the southern front of the Gibraltar-Rif southern edge, which contributes to the movement of the Rif belt with respect of the stable Africa, and sheds new light on the ‘‘Meknes’’ earthquake, confused with the contemporaneous 1755 Lisbon earthquake.

Hypsometric Analysis Using Microwave Satellite Data and GIS of Naina–Gorma River Basin (Rewa district, Madhya Pradesh, India)

Understanding about the stages of geomorphic evolution and geological development of any river catchment and its proneness to erosional process is important for managing the water resources and loss of sediment. Hence, this work is focused on identification of the growth stage of Naina–Gorma river basin and its sub-basins. Hypsometric curve (HC) and hypsometric integral (HI) have been estimated using microwave satellite data in the geographical information system (GIS) environment. The result shows that the HI value ranges from 0.36 to 0.89, indicating youth to mature stage of geomorphic development for river basin and its 15 sub-basins. Therefore, the sub-basins which are at youth age stage of geomorphic development are of high susceptibility to medium to complex denudational processes, erosion, channel erosion, and mass movement activity. This mass movement is due to variation in tectonic activity, rejuvenation processes, and lithology of the area. It helps to measure watershed health, represent the form, its evolution, and morphology of river basin. The results of the statistical analysis suggest that positive statistical relationship exists between the area and the hypsometric integral groups of the 15 sub-basins. It also plays an important role in explaining the dynamics of surface and subsurface water runoff generation. The results of the study have been validated through field visits and surveys. The findings of the work would help in construction and adoption of appropriate soil and water conservation measures in the rain-fed river system to retard the soil erosion and conservation of water.

Morphotectonic analysis of the East Anatolian Fault, Turkey

The East Anatolian Fault (EAF) is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~400 km and forms the Arabian/Anatolian plate boundary in southeastern Turkey. The EAF together with its conjugate fault, the North Anatolian Fault, help accommodate the westward escape of the Anatolian plate from the Arabian/Eurasian collision zone. Morphotectonic features along the EAF provide insights into the nature of landscape development and aid in understanding variations in tectonic activity and fault evolution. Several geomorphic indices, namely stream length-gradient index, mountain-front sinuosity, valley width to valley height ratio, basin asymmetry factor, and drainage density, and hypsometric analysis were examined using digital elevation models. The EAF can be divided into five segments based on its tectonic geomorphology. The stream length-gradient index values are between 50 and 350 along the five segments. Mountain-front sinuosity varies from 1.01 to 1.46 on the five segments. The mean ratio of valley floor width to valley height along the studied segments ranges from 0.11 to 1.32, which is well correlated with the mountain-front sinuosity values. Basin asymmetry factors for 18 catchments range from 1.88 to 26.25 along the study fault zone. Drainage density values for the studied catchments range from 3.5 to 5.6. Finally, the hypsometric analysis index of the 18 catchments indicates high, intermediate, and low relative tectonic activity. The results show that all geomorphic indices are remarkably uniform along the entire length of the fault, thus indicating that fault development was essentially coeval along its length, which supports the view that the present-day Arabian/Anatolian plate boundary (delimited by the EAF) jumped eastwards from the Malatya-Ovacık Fault at ~3 Ma. This is in good agreement with the nearly uniform geological offsets and the GPS-determined present-day slip rate of ~10 mm/year along the entire fault.

Neotectonic evolution of the Tarim Basin Craton from Neogene to quaternary

ABSTRACTThe Tarim Basin Craton is located in the center of the Tarim Basin. Since the beginning of the Miocene, the tectonic activity has been weaker in the Tarim Basin Craton than in the marginal depression and the peripheral orogenic belts. This study investigates the tectonic movements in the Tarim Basin Craton by calculating the sedimentation rates and constructing balanced cross-sections based on well, seismic and geologic data. The tectonic movements in the Tarim Basin Craton have mainly been revealed by geological processes such as sedimentation and subsidence, structural inversion, changes in the structural feature, migration of the structural highs, and faulting. The Neogene sedimentary strata were mainly deposited in two sedimentation centers, the southern and northern sedimentation centers, and the strata in the Central Uplift Zone are relatively thin. The different depressions in different geological periods experienced wide variations in tectonic activity. Tectonic subsidence was significant and the sedimentation rates were high in the Tarim Basin Craton during the Pliocene Period (phase II). During the Neotectonic period, the stresses in the South-North direction converged in the Central Uplift Zone (the Bachu uplift–Central Tarim uplift), and the tectonic activity in this region was more intense than that in the Northern Depression and the Maigaiti Slope in the southwest. In addition, the scale of the paleo-uplift, including paleo-North Tarim Uplift and paleo-Central Uplift Zone, gradually decreased. The faults and fault systems developed zonationally in Neotectonic formations in different structural units, and always distributed discontinuously in vertical direction in sections.

Paleogene tectonic evolution controls on sequence stratigraphic patterns in the Fushan sag, northern South China Sea

Tectonism is of extreme importance to sequence stratigraphic patterns in continental sedimentary basins, affecting both the architectures and internal makeup of sequences. Sequence stratigraphic framework of the Paleogene system in the Fushan sag, northern South China Sea, was built using 3D and 2D seismic data, complemented by drilling cores and well logs data. One first-order, three second-order and seven third-order sequences were identified. Analysis of paleotectonic stress field, unconformities and subsidence history showed that the Paleogene tectonic evolution presented significant characteristics of multistage and episode, and can be divided into three stages: rifting stage I (initial rifting period), rifting stage II (rapid subsidence period), rifting stage III (fault-depressed diversionary period). Partition of the west and east in tectonic activity was obvious. The west area showed relatively stronger tectonic activity than the east area, especially during the rifting stage II. Episodic rifting and lateral variations in tectonic activity resulted in a wide variety of structural slope break belts, which controlled both the sequence architectures and interval makeup, and strongly constrained the development of special facies zones or sand bodies that tended to form hydrocarbon accumulation. This paper classifies the genetic types of slope break belts and their relevant sequence stratigraphic patterns within the Fushan sag, and further discusses the tectonic evolution controls on sequence stratigraphic patterns, which suggests that vertical evolution paths of structural slope break belts and relevant sequence stratigraphic patterns as a response to the Paleogene tectonic evolution were strongly controlled by sag margin types and lateral variations of tectonic activity.

Spatial variations in tectonic activity along the Kachchh Mainland Fault, Kachchh, western India: implications in seismic hazard assessment

The landscape of Kachchh is a unique example of active intraplate region in the world. Various structural features such as domes, faults, folds and associated intrusive suggest early tertiary tectonic history, while youthful topography like youthful nature of the fault scarps and gorges suggests Quaternary tectonic history. Kachchh Mainland Fault (KMF) is a 170-km-long E–W-oriented south-dipping reverse fault situated in pericratonic Mesozoic rift basin in western India. The KMF is a neotectonically active fault substantiated by distinct tectonic geomorphology and seismotectonic history. As Kachchh region experiences an arid climate, it lacks vegetation and provides favorable conditions for assessing the morphology of mountain fronts and gradient of channels using remote sensing to evaluate the relative tectonic activity. We employed the means of quantitative geomorphic analysis extracted from a DEM to access the spatial variation in tectonic activity. The assessment of geomorphic indicators of active tectonics was carried out using tectono-geomorphic parameters such as stream length-gradient index (SL index), mountain front sinuosity (S mf) and valley floor width–height ratio (V f). These parameters were combined to generate the relative index of active tectonics (RIAT) which was further divided into four classes as per degree of tectonic activity. The RIAT classes show segmented nature of KMF, with four segments having decrease in degree of tectonic activity from east toward west. The central and the eastern segments of KMF fall in class 1 and class 2 of RIAT, indicating a relatively higher degree of recent tectonic activity undergone by them. The results of geomorphic analysis are consistent with the landforms present, geological setup and seismicity in the study area. The study would be helpful in accessing the regional seismic hazard from KMF for the entire western India.

Irregular western margin of the Yangtze block as a cause of variation in tectonic activity along the Longmen Shan fault zone, eastern Tibet

On 12 May 2008 and 20 April 2013, respectively, the devastating magnitude 7.9 (Wenchuan) and magnitude 7.0 (Ya’an) earthquakes struck the southwestern Longmen Shan fault zone (LMSFZ), the eastern margin of the Tibetan Plateau. These events were notable because they occurred in a heavily populated area and resulted in severe damage and loss of life. Here we present an integrated analysis of potential field anomalies and a crustal-scale seismic reflection image to investigate the crustal structure and some tectonic relationships associated with these devastating events. Our results show that the western margin of the Yangtze crustal block possesses an irregular margin that extends westward beyond the LMSFZ to the northeast and merges gradually with the LMSFZ to the southwest. We interpret this variation in deep structure to create a lateral heterogeneity in the local stress regime that explains the observed variations in fault geometry and slip distribution, as well as seismicity, of the LMSFZ. This structural complexity results in a differential build-up of stress as the Tibetan Plateau is being extruded eastward. Thus, the results of this research can help identify potential natural hazard zones and focus efforts on hazard mitigation.

Tectonic geomorphology of the Spildağı High Ranges, western Anatolia

The Spildağı High Ranges represent the footwall block of the Manisa Fault Zone (MFZ), which is one of the NW–SE to E–W-trending active dip-slip normal fault systems in western Anatolia. The Spildağı High Ranges were uplifted by approximately 1500m with respect to the lowland Manisa Basin following the Late Miocene. The Plio-Quaternary active tectonics was interpreted through a detailed geomorphic study of the fault-generated mountain fronts and drainage pattern of the Spildağı High Ranges. The combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity along the MFZ. Morphometric measures such as axial river profiles, drainage basin geometry, triangular facets, and mountain‐front lineament patterns document the impact of active tectonics on the landscape evolution of the MFZ, which resulted in the subdivision of western, central, and eastern sectors. An axial river, flowing in the Manisa Basin, is represented by the Gediz River that exhibits a meandering-braided transition pattern. The relative positions of the palaeochannels and oxbows evidence the south-westward migration of the Gediz River towards the MFZ. We infer that the source of axial river migration is tilting of the Manisa plain due the listric nature of the MFZ. Quantitative measurement of geomorphic indices such as mountain-front sinuosity (Smf; 1.11–1.14), valley floor width-to-height ratios (Vf; 0.033‒0.947), facet heights (25–1060m), and facet slopes (5.77°–40.21°) suggest a relatively high degree of tectonic activity along the MFZ. Hypsometric curves for all sector slopes mostly exhibit straight or concave shapes, indicating the presence of the young and weakly eroded mountain front of the Spildağı High Ranges. The combined geomorphic indices and field data suggest that the analysed dip-slip normal fault segments are linear and highly active.

Geomorphic assessment of active tectonics in the Acambay graben, Mexican Volcanic Belt

Spatial variations of Quaternary deformation and tectonic activity of faults along the Acambay graben are assessed using geomorphic and morphometric approaches. The Acambay graben is an east–west trending structure of apparent Quaternary age, located in the central part of the Mexican Volcanic Belt, which gives rise to pronounced scarps over a distance of about 80 km. Continuing tectonic activity in the Acambay graben is confirmed by recent well documented seismic episodes. The intensity of active tectonics has been interpreted through a detailed geomorphic study of the fault-generated mountain fronts and fluvial systems. The combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity among the Acambay graben faults. Geomorphic indices suggest a relatively high degree of tectonic activity along the Venta de Bravo and the Acambay–Tixmadeje faults, followed, in order of decreasing activity, by the Pastores, Temascalcingo and Tepuxtepec faults. Spatial variations within faults have also been identified, suggesting a higher level of tectonic activity at the tips of the faults. This pattern of variation in the relative degree of tectonic activity is consistent with field evidence and seismic data for the Acambay graben. Geomorphic evaluation of the Acambay graben faults suggests that the Acambay–Tixmadeje and Venta de Bravo faults, and specifically the tips of these faults and a central segment near the town of Venta de Bravo, should be considered as areas of potentially high earthquake risk. © 1998 John Wiley & Sons, Ltd.

Geomorphic assessment of active tectonics in the Acambay graben, Mexican Volcanic Belt

Spatial variations of Quaternary deformation and tectonic activity of faults along the Acambay graben are assessed using geomorphic and morphometric approaches. The Acambay graben is an east–west trending structure of apparent Quaternary age, located in the central part of the Mexican Volcanic Belt, which gives rise to pronounced scarps over a distance of about 80 km. Continuing tectonic activity in the Acambay graben is confirmed by recent well documented seismic episodes. The intensity of active tectonics has been interpreted through a detailed geomorphic study of the fault-generated mountain fronts and fluvial systems. The combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity among the Acambay graben faults. Geomorphic indices suggest a relatively high degree of tectonic activity along the Venta de Bravo and the Acambay–Tixmadeje faults, followed, in order of decreasing activity, by the Pastores, Temascalcingo and Tepuxtepec faults. Spatial variations within faults have also been identified, suggesting a higher level of tectonic activity at the tips of the faults. This pattern of variation in the relative degree of tectonic activity is consistent with field evidence and seismic data for the Acambay graben. Geomorphic evaluation of the Acambay graben faults suggests that the Acambay–Tixmadeje and Venta de Bravo faults, and specifically the tips of these faults and a central segment near the town of Venta de Bravo, should be considered as areas of potentially high earthquake risk. © 1998 John Wiley & Sons, Ltd.

Tectonic, climatic and lithologic influences on landscape fractal dimension and hypsometry: implications for landscape evolution in the San Gabriel Mountains, California

East-west variation in tectonic activity and strong north-south climatic gradients provide a unique opportunity to study tectonic, climatic and lithologic influences on landscape evolution in the San Gabriel Mountains, California. The competing tendencies of constructive tectonic and degradational climatic effects act against lithologic resistance to influence fluvial systems, and thus the nature of adjacent and nested drainage basins. Landscape fractal dimension ( D), a measure of surface roughness over a variety of scales, and the hypsometric integral ( I), a measure of the distribution of landmass volume above a reference plane are useful measures of altitudinal variation with scale. As such, they may provide clues as to the relative influences of tectonism, climate and rock type. Topographic analyses of the San Gabriel Mountains clearly indicate that tectonism strongly influences D at range-wavelength scales, while rock-type variation apparently influences D and I at smaller scales. Tectonism is also shown to influence I across the mountain-piedmont junction at all scales investigated. Tectonic activity shows strong negative correlation with both I and D because tectonically active portions of the mountain front do not allow time for much landscape dissection by lower-order streams. Three-dimensional topographic modeling suggests climatic parameters exert a stronger influence on D than does tectonism. This modeling also suggests an inverse correlation between range-scale D and I with varying climate and uplift rate; a positive correlation is observed in the San Gabriel Mountains. We suggest this difference results from (1) differences in uplift style between the San Gabriel Mountains and the models, and/or (2) variation in rock-type erodibility present in the San Gabriel Mountains but which was not modeled. We postulate that the interaction of tectonic, climatic and lithologic parameters influences the stable I and D to which a landscape evolves. Key questions remaining include: (1) the time required to reach a stable I or D after a climatic or tectonic change; (2) what does the fractal nature of topography tell us about the scaling characteristics of major landforming processes; (3) how does climate influence range-scale I and both range- and small-scale D; and (4) what are the effects on I and D of range-scale lithologic variation, both in the models and in real landscapes?

The alluvial fan, fan-delta and sublacustrine fan of Paleogene age within Liaohe Rift, Liaoning Province, China

Liaohe Rift is the Liaoning section of the Tan-Lu fault system, which passes through Bohai Sea and is elongated toward the north. Two main subparallel faults moved violently during the Paleogene in the area, and two columns of asymmetrical depressions stretching in NE-SW direction were formed. The oil reservoirs in the basin of Paleogene age can be classified mainly into three types: (1) alluvial fan, (2) fan-delta, and (3) sublacustrine fan based on the studies of the colour and composition of mudstones, sedimentary structure of sandstones and rhythm of sequences. Variation in tectonic activity caused differences in provenance; the sandbodies therefore have their own characteristics. Based on the above, a sedimentary model for the Liaohe Rift can be established: from the margin toward the centre of the basin, the types of sedimentary facies were respectively alluvial fan, floodplain, fan-delta, subaqueous canyon and sublacustrine fan, fan-delta and sublacustrine fan formed the main facies, and were located on the downfaulted side of the faults, while the floodplain and subaqueous canyon were the transition facies. The greater the concentration of faults, the more intense was their tectonic activity, the greater the sediment supply from the upfaulted blocks and the lower sediment maturity and less well developed are the transition facies. Generally, during lake flooding, the greatest tectonic activity took place at the steep side of the basin. During subaerial sedimentation, the least activity happened along the strike direction of the basin. By using this model, the sedimentary bodies formed in different structural episodes and portion of the basin can be interpreted.

Gravity anomalies, seismicity, subducting slab folding and surface deformations in the orogenic belts—an example from the Andaman-Nicobar region

Geophysical data in relation to the geometry associated with the Andaman-Nicobar arc are less strongly constrained. The lithosphere, after buckling, becomes convex downwards in a series of plunging ridges (anticlines) and depressions (synclines). The variation of tectonic activity is greater in front of the subducting folded oceanic lithosphere whereas volcanoes are confined to the shear zones present over the common limbs of plunging ridges and depressions. The representation of the subducting slab geometry over the surface leads to tectonic variations in the orogenic belts.

Sedimentary stratigraphy of Eocene sheetflood deposits, Southern Pyrenees, Spain

AbstractThe Eocene Monllobat Formation of the southern Pyrenees accumulated under continental (non-marine) conditions. The total thickness of 180 m consists of seven cycles, defined by coarse member concentrations (often sheets) at the bases. The lateral extent of the sheets defines the fixed positions of eight parallel-trending alluvial systems, separated by narrow zones of fine sediment.Sheetflooding dominated the sedimentation of these eight contemporaneous alluvial systems. The sediment was supplied from the rising axial zone of the Pyrenees. The cycles were caused by variations in tectonic activity. The positions and forms of coarse members were locally determined by contemporaneous faulting and folding of the alluvium.

Factors Influencing Sedimentation in the Shallow Neritic Environment: ABSTRACT

Sedimentation in the shallow neritic environment is influenced by the interplay of numerous factors. Both type and thickness of the sediment differ depending upon the relative significance of these factors. The chief factors to be considered are tectonics, physiography, climate, biological activity, and associated energy relationships. The tectonic intensity of the source area and depositional site of the sediments, although primary factors, may be surpassed in significance by the factors of climate and biological activity. Variation of intensity of uplift and deformation of the source area provide primary control on the composition of the source area and the sediment derived therefrom. Sediments range from mature to immature, and from fine to coarse terrigenous clastics. The same variation of tectonic activity provides variations in physiography of the source area and accompanying energy relationships. Physiographic variations may produce both local and regional climatic variations as a third order factor. Climate and its influence on and control of vegetation will control weathering, resulting soils, and erosion. Thus climate may be the primary factor in the type and amount of sediment derived from the source area. Tectonic intensity of the depositional site controls the thickness of the sedimentary sequence, with climate and biological activity providing the influence modifying the type and character of the sediment deposited. Wave and current energy related to storms modify the sediment type and distribution. End_of_Article - Last_Page 340------------