Basin Asymmetry Research Articles

From Symmetric Rifting to Asymmetric Spreading—Insights Into Back‐Arc Formation in the Central Mariana Trough

AbstractThe Mariana Trough is the youngest back‐arc basin in a series of basins and arcs that developed behind the Mariana subduction zone in the western Pacific. Active seafloor spreading is ongoing at a spreading axis close to the Mariana Arc, resulting in a pronounced asymmetric configuration (double rate to the west 2:1) at 17°N. The formation of back‐arc basins is controlled by the subducting slab, which regulates the temporal development of mantle flow, entrainment of fluids, and hydrous melts together with the magma generation. To better understand the formation process of back‐arc basin asymmetry in the central Mariana Trough, we combined 2‐D P‐wave traveltime tomography results with high‐resolution bathymetric data. Here, we show that the crust in the central Mariana Trough is 6.5–9.5 km thick, which is unusually thick for oceanic crust. While the lower crust exhibits average seismic velocities of 6.5–7.2 km/s, high‐velocity anomalies occur at the margins of the Mariana Trough, indicating that magmatic accretion was affected by hydrous melting during rifting. While the Mariana Trough developed from a rather symmetric rifting (0.89:1) to a strongly asymmetric seafloor spreading stage (5.33:1), the contribution of hydrous melts declined and the opening direction changed at ∼5 Ma. Asymmetric basin opening is potentially driven by the far‐field stress effect of the subduction zones on the western boundary of the Philippine Sea Plate.

Tectonic evolution of Bursa Yenişehir Basin, Turkey from the Neogene to the Quaternary using a morphotectonic approach

In this study, the morphotectonic features of the Yenişehir pull‐apart basin in Bursa in northwestern Turkey were analysed. The faults in the region are the most important structural elements that characterize the morphology of the Yenişehir pull‐apart basin. The aim of this study is to show the deformation effects of these active faults on the geomorphology with some basic morphometric indices. The morphotectonic features were evaluated using the hypsometric curve and hypsometric integral (Hi), drainage basin asymmetry (the asymmetry factor (AF) and the transverse topographic symmetry factor (T)), river length gradient index, mountain front sinuosity, and valley floor ratio. The morphometric indices that play an important role in the analysis of catchment areas are the Hi, AF, and T indices, which indicate tilting and erosion activities. According to the results of the hypsometric curve and hypsometric integral, the Yenişehir Basin is a young basin with a uniform topography as expected in an active pull‐apart basin formed by faulting in the Quaternary. The relative tectonic activity index (Iat) of the study area was calculated using the values of hypsometric integral, transverse topographic symmetry factor, asymmetry factor, mountain front sinuosity, valley floor ratio and stream length gradient index. The Iat values indicate the tectonic activity of the basin from Pliocene to Recent. Three different tectonic classes were identified in the study area. These are class 1 (high relative tectonic activity), class 2 (moderate relative tectonic activity), and class 3 (low relative tectonic activity). The Iat classification data show that the impact of tectonic activity on the geomorphology is lower in the Iat class 3 indices than in the others. The Iat data show high tectonic activity in the region where active faults of the North Anatolian Fault Zone southern branch are located.

Morphotectonic Study of Iring Watershed, Tamenglong District, Manipur, India

The primary focus of study is on the morphotectonic investigation of the Iring watershed in the Manipur district of Tamenglong. Various morphotectonic factors were studied using data from Aster-DEM, SENTINEL-2 satellite, Survey of India Topographical Maps, and field verification. Drainage Basin Asymmetry (AF), Transverse Topographic Symmetry (T), Basin Elongation Ratio (Eb), and Valley Floor Width to Valley Height ratio (Vf) are a few examples of geomorphic indices that were examined. It was found that the 118.67 km2 basin is tectonically active, as evidenced by structural characteristics and geomorphic parameter values. River stress knick sites are indicated by regions with an SLK index greater than 10. The watershed exhibits asymmetry, as indicated by the average T value of 0.195. Actively incising V-shaped valleys linked to uplift are indicated by Vf values between 0.192 and 0.263. The river is migrating to the western side due to elevation on the eastern side, as shown by the AF result of 47.72%. A basin that is extended and experiencing tectonic activity has a basin elongation ratio of 0.66. The hypsometric curve and hypsometric integral (~50%) indicate that the erosion process in the basin is at its early mature stage. Keywords: Morphotectonic Indices, Active Tectonics, Geology, Morphometry, Drainage Basin, Hypsometry

Morphometric Evaluation of the Relative Uplift Rates along the Vigan–Aggao Fault in Ilocos Norte, Philippines

The Vigan–Aggao Fault (VAF) in northern Luzon Island is a NNE-trending sinistral fault divided by fault bends, which are associated with local variations in the fault’s kinematics. In this study, we examined the relative uplift rates across the fault bend in the San Juan–Vintar segment of the VAF using morphometric indices. Basin-based indices, namely hypsometric integral, basin shape, basin elongation ratio, and basin asymmetry factor, and non-basin-based indices, namely stream length-gradient index, normalized stream length-gradient index, and mountain front sinuosity were calculated to isolate and examine the surface processes that influence landscape development. We then integrated the basin-based results with geological data to create a relative tectonic activity index (RTAI). Clustering analysis of the results revealed hotspots along the bent section of the fault indicating more values that suggest higher relative uplift rates during the development of the landscape. The morphometric indices showed that the highest uplift rates are along the central VAF strands. This study described and evaluated the relative uplift rates of a known active fault system in Ilocos Norte, in the absence of detailed field structural data. This study also reinforces the utility of morphometry in identifying priority sites for detailed paleoseismic and seismic hazard analyses.

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.

Tectonic geomorphology of Türkiye and its insights into the neotectonic deformation of the Anatolian Plate

Quantitative geomorphic analyses are usually powerful in identifying active tectonics across global orogenic belts. Our present study will focus on the Anatolian Plate which hosts a lot of recent catastrophic earthquakes in Türkiye. Six geomorphic indices for 100 sub-basins around Türkiye have been computed including local relief, slope, normalized steepness index (kSn)), hypsometric curve and integral (HI), transverse topographic symmetry factor (Tf), and the basin asymmetry factor (Af). The averaged kSn and Af values have shown four high-value anomalous zones, suggesting relatively high uplift rates featured by high river incision and regional tilting. The values of 0.35 ​≤ ​HI ​< ​0.6 for basins with S-shaped curves imply intensive tectonic activities along the eastern part of the North Anatolian Fault Zone (NAFZ), the Northeast Anatolian Fault Zone (NEAFZ), the East Anatolian Fault Zone (EAFZ), and the Central Anatolian Fault Zone(CAFZ). All results of the geomorphic indices analysis suggest a relatively high degree of tectonic activity in the following four areas, the Isparta Angle, the Eastern Black Sea Mountains, the South-eastern Anatolia Region, and the Central Anatolian fault zone. We further suggest that the eastern part of the NAFZ, NEAFZ, EAFZ, and CAFZ will be more active in tectonic activities, with a greater potential for strong earthquake occurrence.

Tectono-geomorphic and active deformation studies in the Ujh basin of Northwestern Himalaya

This study focuses on the morphotectonic analysis of the Ujh River basin, examining various aspects related to geometrical changes in the drainage basin caused by tectonic and erosional processes. The topographic development of the Ujh River basin is a response to enhanced tectonic deformation caused by Main Central Thrust (MCT) and Main Boundary Thrust (MBT). We assume that the basin asymmetry, tilting, incision, and migration of the river basin are regulated by the compressive force generated between MBT and MCT. The results were characterized by a high Asymmetry Factor (Af) indicating greater asymmetry suggesting a rightward tilting with low Valley Floor to Valley Width (Vf) values which indicate differential uplift and incision owing to ongoing tectonic processes. The high Stream Length Gradient (SL) Index values in the MCT zone, indicate sudden topographic breaks caused by the vertical tectonic uplift with active erosion processes. The Ujh River basin is in a disequilibrium state, with convex portions indicating uplift and concave portions indicating subsidence on the slope-area plot. The χ analysis, plotting χ values against elevation, highlights upliftment and erosion zones along the trunk stream, with major slope breaks and high χ values observed in the upstream region, particularly along the MCT. Overall, the Ujh River basin exhibits morphotectonic characteristics indicating ongoing tectonic activity and a state of disequilibrium.

Morphotectonics and paleostress analyses of Kutch area, Gujarat, India

The Kutch Rift Basin (KRB) is of great attention for its possible hydrocarbon reserve. In this context, geomorphologic and structural geologic studies of the onland basin area are crucial. Application of geomorphic indicators viz., compactness coefficient (Cc), lemniscate coefficient (k), form ratio (Rf), basin shape index (Bs), basin asymmetry factor (AF), hypsometric integral (HI), elongation ratio (Re) and circularity ratio (Rc) have been utilized to calculate the Index of Active Tectonics (IAT) for a part of KRB. Watersheds 5 (the Bhuj area), 9, 10, 11, 17, 18 and 20 belong to class 1 as per the IAT. This indicates that these watersheds are very highly tectonically active at present. Calculated valley floor width height ratio (Vf) and mountain front sinuosity (Smf) quantify the active valley incision in the Quaternary that uplifted the Bhuj area. This uplift was accompanied by a high-degree of drainage rejuvenation due to neotectonics and formation of a canyon in the Khari river. Paleostress analyses revealed NNE and NW-oriented extensions around Bhuj that can correspond to NW and NNE-trending normal fault planes, respectively.

Geospatial Analysis for Relative Seismic Activity Assessment: A Case Study of Fatima Suture Zone in Western Saudi Arabia

In this paper, we state the usefulness of geomorphic analysis, typically applied to highly deformed landforms, to investigate the tectonic geomorphology of an intercontinental structure: the Fatima suture zone. The Fatima suture zone (FSZ) landscape is a tectonically distinct deformation zone along the eastern coast of the Red Sea in western Saudi Arabia providing a complex zone in terms of geology, tectonics, and geomorphology. This zone presents many deformations and fault reactivations that were produced from the effect of horizontal, vertical, and thrust motions as well as deposition and erosion processes. Through several morphometric analyses, remotely sensed data, and geospatial techniques, we recognized the detailed geomorphic surface features of the Fatima suture zone region. Morphometric indices applied in this paper include the stream length gradient index (SL), basin asymmetry factor index (Af), hypsometric integral index (Hi), valley floor width to valley floor height ratio index (Vf), basin shape index (Bs), and mountain front sinuosity index (Smf). Every single morphometric index provides three different relative tectonic classes based on the assigned value ranges. The overall results obtained from the analysis were averaged and presented as an indicator index namely the relative seismic activity (RSA) index, which was classified into four distinct classes from relatively very high to low seismic activity: class 1 is very high seismic activity (CA ≤ 1.5); class 2 is high seismic activity (1.5 &lt; CA ≤ 2); class 3 is moderate seismic activity (2 &lt; CA ≤ 2.5); and class 4 is low seismic activity (CA &gt; 2.5). Additionally, a combination of the two indices (Smf and Vf) was presented as a quantitative model of the relative seismic activity of the examined mountain fronts. The results of the RSA index provided signatures of all four classes of the study region. Two-thirds of the total area of the study region were recorded as high to very high classes in terms of seismic activity. The paper finally concludes that this integration method allows assessment and evaluation of the highly deformed landscapes related to active tectonism. Despite the impact of the Fatima suture zone providing low to medium activities in some parts, it has a signature control on the recent landscape evolution.

Geomorphological significance of the morphometric characteristics of first-order basins in the Siwalik Hills in the Himalayas, Nepal

ABSTRACT First-order basin morphology is important for the functioning of the whole hydrologic system. This study examines the geomorphology of three areas in the tectonically active Siwalik Hills, Nepal, using morphometric variables. Twenty variables for 11,200 first-order basins were obtained from maps and Digital Elevation Models (DEMs) of three areas (the Machheli, Banganga and Binai river basins). Principal component analysis of each area condensed these into 6 major components, which accounted for 78–82% of the total variance in each data set. Rotated principal components were remarkably consistent between the three areas. The average slope, area, elevation range, valley angle, shape index, hypsometric integral, basin asymmetry factor and drainage density were identified as the eight most important morphometric variables defining these components. Ordinal grouping and k-means clustering led to recognition of eight basin types, distinguished predominantly by elevation range, average slope, area and valley angle. Shallow and steep basins are predominant in all three areas. The spatial distribution of first-order basin types exhibits a distinct pattern of geomorphic regions. The study demonstrated that a first-order basin is a suitable unit to demonstrate the morphological characteristics of a geologically complex area, and the study approach can be applied more broadly.

Spatial variation in landscape evolution of the Xiaojiang Region, SE Tibetan Plateau

Both tectonism and erosion are presumed to have influenced the landscape evolution of the Xiaojiang Region, SE Tibetan Plateau. However, it remains unclear which of these broad processes has played the dominant role in determining landscape form and evolution. To establish the relative importance of these two processes, we measured river longitudinal profiles and spatial variation in selected geomorphic indices within the region. We measured longitudinal profiles along four large rivers from north to south through the region and also measured drainage basin asymmetry, basin shape index, hypsometric integral, normalized stream-length gradient index, and the ratio of valley-floor width to valley height of 77 drainage basins in this region. The four longitudinal profiles reveal that tectonic activity decreases from north to south. Spatial variation in geomorphic indices reflects that the topography in the Xiaojiang Region may be primarily influenced by three major faults: the Xiaojiang fault, the Shiping fault, and the Qujiang fault, rather than influenced by precipitation, lithology, and drainage reorganization. The tectonic activity in different parts of the region shows that the northern part is the most active, the central part is the least active, and the southern part is moderately active. It is concluded that the spatial variation in landscape form and evolution of the Xiaojiang Region has been influenced more strongly by tectonics than by erosion.

Evaluation of relative active tectonics by using geomorphic indices of the Bamo anticline, Zagros Fold-Thrust Belt, Kurdistan Region of Iraq

The Mountain Front Flexure forms a prominent morphotectonic structures along the Zagros Fold-Thrust Belt (ZFTB). It consists of several segments that defines tectonic salients and recessions within the belt. These segments are separated by strike-slip faults, including Khanaqin fault, which forms the boundary between the Kirkuk embayment and Lurestan Arc. The Bamo anticline is a complex N–S trending structure located above the Khanaqin fault zone, and it is thought to manifest active deformation in the Zagros Fold-Thrust Belt and along the fault. This study examines the state of active tectonics along the Bamo anticline through quantitative analyses of the evolved landscape using geomorphic indices. For that reason, six indices have been chosen for the analysis, such as stream length-gradient index (SL), drainage basin asymmetry (AF), hypsometric integral and hypsometric curve (HI & HC), ratio of valley-floor width to valley height (VF), basin shape (BS), and mountain front sinuosity (Smf). Each index's results were categorized into three classes, and the results from the first five indices, excluding Smf, were integrated to get the index of relative active tectonics (IRAT). This index was then compared with the results of Smf to assess the relative active tectonics (RAT) along the anticline. The results of the IRAT, classified into four classes from very high to low tectonic activity, reveal that no area is classified as class 1 (very high activity). However, 38% and 56% of the region are categorized as classes 2 (high activity) and 3 (moderate activity), respectively. Furthermore, the remaining 6% of the research area exhibits class 4 (low activity). The Smf values for the Northern, Middle, and Southern segments of the anticline are 1.12, 1.18, and 1.27, respectively. Consequently, based on the Smf data, all mountain fronts are classified as class 2 (moderate tectonic activity.

Evolution of the Limpopo River Basin in Botswana based on morphometric and morphotectonic features from selected rivers using GIS techniques

ABSTRACT This study used morphometric techniques to generate new information describing the evolution and hydrogeological behaviour of the Limpopo River Basin in Botswana, based on the analysis of drainage surface features, form, and size. Drainage basins provide basic information on their evolution, which, when quantified, yield information on the interaction between tectonics, climatic, and surface processes. Drainage networks were extracted from the Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) (90 m × 90 m), and subsequently, morphometry indices were computed using ArcGIS 10.5. Drainage network extraction was performed using the Arc Hydro extension in ArcGIS 10.5. ArcGIS 10.5 image processing technique was used to extract lineaments and create rose diagrams. The results showed that the Limpopo sub-basins in Botswana were drained by fourth- and fifth-order streams, with a total drainage area of 107, 871 km2. Additionally, the basin asymmetry and mean bifurcation ratios showed tilting in the sub-basins, suggesting tectonic instability and structural control in a low – to-moderate active tectonic zone. The sub-basins also had a coarse texture, indicating a high infiltration capacity. These results are essential for planning and managing watershed systems, flood risk assessment, and potential groundwater assessment for the different sub-basins of the Limpopo River Basin in Botswana.

Index active tectonic relative of Karangsambung geopark area, Central Java, Indonesia: assessment for developing geological disaster-based areas

Karangsambung as a “subduction fossil” of the Cretaceous-Paleocene on the island of Java, has a complex geological structure. The current subduction process in the south of Java with a north-south compression force has contributed to the reactivation of the geological structure in Karangsambung. The index active tectonic relative (IAT) of the Karangsambung area reflects the current level of tectonic activity. IAT is obtained from quantitative calculations of geomorphic indices, including streams length - gradients index (Sl), the ratio of valley floor width to valley height (Vf), basin asymmetry (Af), basin shape (Bs). mountain front sinuosity (Smf), the hypsometric integral (HI), and drainage density (Dd). The index active tectonic relative (IAT) calculation with an average IAT value of 2.37 indicates that tectonic activity is in the medium/moderate category. In addition, an attempt was made to compare the regional neotectonic activity with the relative tectonic activity of the study area. Based on this geomorphic analysis, the study area may have a lower seismic risk but needs to be evaluated more carefully for regional seismic hazards. The IAT value can be used as an initial reference for geological disaster assessment, especially earthquakes hazard in the development of the Karangsambung National Geopark Area.

Morphotectonic Study of the Ijai Watershed, in Parts of Kangpokpi, Tamenglong and Noney Districts Manipur, India

The present study aims to describe and bring out the tectonic nature of Ijai watershed in parts of Kangpokpi, Tamenglong and Noney districts of Manipur. Ijai watershed has an area of 184.0 Km2which is also tectonically active as depicted by the analysed values of different geomorphic indices like SLK index, Valley Floor Width to Valley Height ratio (Vf),Transverse Topographic Symmetry (T), Drainage Basin Asymmetry (AF), Basin Elongation Ratio (Eb), hypsometric curve and its integral. The data for the analysis of the geomorphic indices are extracted from the DEM and SENTINEL-2 satellite data and SOI-toposheets. Along the stresses of the rivers there are numbers of regions having SLK index greater than 2 depicting presence of knick points.Vf values ranges from 0.053 to 0.144 showing V-shaped valleys with streams that are actively incising and are commonly associated with uplift. Average value of T of Ijaiis found to be 0.4182, which reflects asymmetric in nature. The results of AF is 36.47 %, signifies the upliftment of the eastern side of the basin resulting the shifting of the river to western side in general. The result of Basin Elongation ratio (Eb) is 0.59 which signifies elongated basin undergoing tectonically activities. The result of hypsometric curve and hypsometric integral (Hi) 49 % reveals that basin is passing through early mature stage under the cycle of erosion.

Tectonic geomorphology of Bozdoğan and Karacasu grabens, western Anatolia

Western Anatolia is one of the most rapidly extending and seismically active regions in the world. The circa N-S extension since the Early Miocene caused the formation of E-W trending major grabens and intervening horsts, having earthquake potentials with magnitude ≥5. The E-W oriented Büyük Menderes graben cross-cuts the broadly N-S oriented Bozdoğan and Karacasu grabens, of which the boundary faults of the latter are the source of seismic activity. Geomorphic indices, including drainage basin asymmetry, mountain front sinuosity, valley-floor width to valley height ratio, stream length-gradient index and normalized channel steepness index, were used to evaluate the boundary fault segments of the Bozdoğan and Karacasu grabens. The results indicate that both grabens are tectonically active and therefore regions of earthquake potential, consistent with the epicenters of earthquakes. Thus, it can be inferred that fault segments of second-order grabens, which are crosscut by the boundary faults of seismically active main depressions, are apparently reactivated by ongoing tectonism and may represent seismic activity. This suggestion applies also for similar basins located in the western Anatolia.

Morphometric analysis of Chapecó river basin: Searching for vestigial trace of neotectonic on a basaltic landscape at southern Brazil

The Chapecó River Basin (CRB) is located in the west of Santa Catarina State (South Brazil) and has a relief modelled by a large basalt lava outpouring that occurred in the Paraná Sedimentary Basin. The CRB is characterised by two plateau compartments resulting from regional denudation and associated with a river network that was formed after the basaltic lava completed its flow phase in the Lower Cretaceous. Elements of structural geology together with weathering of rocks and its products, such as regolith, have been commonly used to analyse and interpret the landforms in CRB, whose fluvial landscape is shaped by bedrock channels and incision valleys. Nevertheless, there is a lack of detailed studies about such structural factors in terms of type and origin, and to what extent they may be proxies of tectonic tensions of an intra-plate character. In the lack of guide levels and deposits that allow a better interpretation of recent tectonic deformations, in this work we aimed to evaluate tectonic-structural factors involved in the landscape evolution of the CRB through measurement and analysis of morphometric indices derived from the ALOS PALSAR DEM. We analysed the following morphometric parameters for 43 sub-basins: the basin asymmetry (FA), hypsometric integral (HI), elongation, local relief, slopes distribution, Hack index for the two main river channels (Chapecó and Chapecozinho), and concavity index of the main channels of sub-basins. The results obtained from the morphometric analysis of the river network indicate the existence of a geomorphological disequilibrium of its relief. This result was observed in the transition from the medium to the low basin and in the base levels of the Chapecó and Chapecozinho rivers. Such disequilibrium is shown by convex and irregular longitudinal profiles, knickpoints, sub-basins with high values of asymmetry and hypsometric integral (HI), as well as a low correlation between slope and channel gradients for the sub-basins analysed. This context is consistent with the neotectonic hypothesis of a regional uplift that provide energy to the system to reactivate faults, tilt blocks, and deepened the incision of the river network, leading to the creation of new knickpoints and a transient river network. From the results and analysis, we can conclude that the largest knickzones and waterfalls in the study area can be considered markers associated with quaternary tectonic forcings, although many of these geomorphological features may have originated simply by joints and fractures in the rocks.

The influence of cenozoic magmatism on drainage rearrangement processes of the northeast sector of the Borborema Highlands, northeastern Brazil

The diversity of structures and tectonic regimes in the Borborema Province caused the various morphostructural compartments to follow different evolutionary pathways throughout and after the fragmentation of Gondwana. In the northern Borborema Highlands, post-rift evolution occurred in a differentiated way, and the present study aims to understand how this occurred. For this, a set of morphological (geomorphological mapping, mapping of drainage anomalies, and extraction of relief lineaments) and morphometrics indexes (hypsometric curves, Basin Asymmetry Factor, Hack Index, Concavity Index, and χ Index) have been applied to drainage watersheds and low-order channels. The results obtained allowed us to propose a post-rift evolutionary model. To the north, the Highlands presents a recent divide resulting from a series of Cenozoic tectonomagmatic reactivations that promoted river rearrangement processes, such as drainage direction reversal and relief inversion—the current conditions of semiaridity and the absence of epigeny cause this drainage divide to remain stationary. The results diverge from the idea that only high relief margins were subject to greater tectonic control. Despite its modest altitudes, the transforming equatorial margin of Northeastern Brazil exhibits a significant recurrence of morphotectonic reactivation events, operating at different space-time scales. The area is also one of the sectors of the Brazilian passive margin with the highest record of modern seismicity.

Active tectonics of the Thoubal‐Chandel Thrust, Manipur Hills, Indo‐Myanmar Range, northeast India: Insights into deformation pattern of adjacent thrust sheets in a growing orogen

The NE–SW trending and SE dipping Thoubal‐Chandel Thrust (TCT) in eastern Manipur Hills of the Indo‐Myanmar Range (IMR) places the Thoubal‐Chandel thrust sheet over the Churachandpur‐Mao thrust sheet. Despite being seismically active, the active tectonic aspects of the major structural discontinuities within the IMR, including TCT, are not yet studied in detail. The present study aims to examine the active tectonics of the TCT and other associated faults, with particular focus on deformation of the Churachandpur‐Mao, and Thoubal‐Chandel thrust sheets. Association and disposition of landforms, and statistical analyses of Mountain‐front Sinuosity Index (Smf), Stream Length‐Gradient Index (SL), Hypsometric Integral (HI), Drainage Basin Asymmetry Factor, and Transverse Topography Symmetry Factor (T) reveal that both of these adjacently lying thrust sheets are actively uplifting due to oblique‐slip movement on their basal thrusts, but with spatially variable rates. In general, higher SL (mode = 219) and HI (mode = 0.527) in large parts suggest faster uplift of the Thoubal‐Chandel thrust sheet than the Churachandpur‐Moa thrust sheet, which has comparatively lower SL (Mode = 140) and HI (mode = 0.416). However, differential along‐strike uplift rates have caused tilting of both the thrust sheets. Faster uplift of the northern part of Thoubal‐Chandel thrust sheet has caused its overall southward down‐tilting, whereas faster uplift of the southern part of Churachandpur‐Mao thrust sheet has caused its overall northward down‐tilting. The study brings out that the deformation pattern of even the adjacent thrust sheets of growing orogens could be at stark variance albeit the same stress regime.

Calculated the Tectonic Activity of Catchments in the SAQEZ Geomorphology Unit (Iran and Kurdistan) Using Morphometric Indices

Landslides are tectonic and morphological indicators. The Morphotectonics Index is a suitable tool for probability estimation and earthquake planning in the region. Landslides are the most common natural threat in Iran. A sustainable management plan requires landslide hazard zoning planning. Therefore, the estimation of landslide risk in selected areas using the morphological index is the purpose of this study. Rivers are very sensitive to tectonic movements, and river landforms are closely radiated to tectonic movements. The Deformation Tectonic Index was used as a tool to identify new and active structures for these movements. The SAQEZ River Basin is located in the northwest of the country according to its characteristics. Its landform has a high flood capacity and a moderate slope of about 33.01%, resulting in severe erosion and flooding in the area. The purpose of this study was to analyze tectonic activity in the SAQEZ River Basin using remote sensing software and topographic maps and digital elevation models in a GIS environment. In this study, four morphological and structural indices, including river length gradient index (SL), basin shape index (BS), river tortuosity index (Sr), and basin asymmetry factor (Af), were used, and their results were analyzed. An analysis is expressed as the Active Tectonic Index (IAT). According to the survey results, the values of the SL, BS, Sr, and Af indices were 207, 1.09, 1.27, and 66, respectively. The Active Tectonic Index (IAT) shows moderate tectonic activity in the area.