NW Himalaya Research Articles

Evaluating landslide hazard, vulnerability, and risk using machine learning; A case study from the Alaknanda Valley, NW Himalaya

Evaluating landslide hazard, vulnerability, and risk using machine learning; A case study from the Alaknanda Valley, NW Himalaya

Heterogeneous Seasonal Deformation and Strain Budget in Himachal, NW Himalaya from new cGPS measurements: Hydrological, Covid-19(?) and Seismic Hazard Implications

Heterogeneous Seasonal Deformation and Strain Budget in Himachal, NW Himalaya from new cGPS measurements: Hydrological, Covid-19(?) and Seismic Hazard Implications

Locked Frontal and Lateral Ramps on the Main Himalayan Thrust Beneath NW Himalaya Illuminated by Precisely Located Seismicity

AbstractThe Kashmir “seismic gap” in NW Himalaya is marked by hinterland‐to‐foreland reduction in GPS‐geodetic arc‐normal convergence‐velocity and increase in horizontal strain‐rate, associated with occurrence of moderate‐to‐small earthquakes. We analyze continuous waveforms from Jammu and Kashmir seismological network (2015–2017) to detect and preliminarily locate 1064 events, followed by probabilistic non‐linear relocation of 360 well‐located local earthquakes, with magnitudes 0.6–4.7 and hypocentral depths 0–60 km. Hypocenters shallower than 20 km lie on or above the Main Himalayan Thrust (MHT), clustered beneath the Kishtwar Higher‐Himalaya. Hinterlandward dipping seismicity‐clusters coincide with a MHT mid‐crustal frontal ramp, marking a 50 km wide locked‐to‐creep transition. The frictionally‐locked up‐dip MHT segment is 100 km wide, capable of hosting a 8.4 earthquake, if ruptured completely. Clustered seismicity SW of the Kishtwar Window and to its east illuminate MHT lateral‐ramps, which may limit the rupture width and/or modulate the rupture propagation. Entirely seismogenic underthrust Indian‐crust poses additional hazard from large earthquakes within it.

Geochemical signatures of forearc serpentinites from oceanic to continental subduction

In subduction systems, the forearc (FA) serpentinized mantle plays a key role as a reservoir for fluid-mobile elements, especially those prone to early mobilisation from the slab. FA serpentinites therefore provide an indication of the fluid characteristics that have been steamed out of the slab, and allow better quantification of elemental recycling and fluid flow. FA serpentinites outcropping along the Indus Suture Zone are formed by hydration of mantle peridotites by fluids derived from the Indian slab, providing a geochemical record of fluid-rock interactions during the India-Eurasia convergence. Systematic trace and multi-isotope (Sr and Pb) analyses of serpentinites from three major sites, namely Shergol-Tingdo, Kargil and Tso Morari, along the Indus Suture Zone in Ladakh (NW Himalaya) show that these rocks record a major change in the origin of metasomatic agents, from oceanic to continental subduction. The Shergol-Tingdo and Kargil FA serpentinites, formed under low temperature and pressure conditions, are characterised by high B enrichment and As and Sb depletion, high alkali/U ratios and relatively unradiogenic Sr and Pb isotope ratios. These geochemical characteristics are identical to those reported for modern oceanic subduction zones (e.g., Mariana forearc) and are consistent with input by fluids derived from subducted oceanic crust. In contrast, FA serpentinites from the Tso Morari ultra-high pressure unit show enrichment in fluid mobile elements such as As, Sb and U, low alkali/U ratios and radiogenic Sr and Pb isotopic compositions. These features suggest a change in the metasomatizing agent with a strong influence from subducted continental material. Consistent with this scenario, the Sr-Pb isotopic composition of the Kargil FA serpentinites can be reproduced by mixing between an Indian MORB-depleted mantle source and fluids derived from dewatering of blueschist facies oceanic metasediments, whereas in the case of Tso Morari a fluid end-member derived from various eclogitic continental metasediments is required. We propose that the observed geochemical signature of the Indus Suture Zone FA serpentinites can be used to reconstruct the geochemical exchanges between the slab and the overlying mantle from intra-oceanic to continental subduction. This successful systematic approach could be applied to other collisional contexts

Geochemistry of Mafic Rocks From the Nagrota–Kathindi Section, Himachal Pradesh, Northwestern Himalaya: A Probable Example of Plume–Lithosphere Interaction

ABSTRACTThe Northwest Himalayan region has a record of several phases of mafic magmatic activity spanning from Precambrian to Cenozoic in a dynamic tectonic setting. Here, we studied detailed petrography and new whole‐rock geochemistry of mafic volcanic and dykes from the Nagrota–Kathindi Section (NKS), Himachal region of the NW Himalaya, to understand the petrogenesis and possible tectonic setting. Both rock types have comparable mineralogical compositions (clinopyroxene + plagioclase + actinolite‐tremolite + chlorite + iron oxides ± hornblende ± epidote ± quartz ± carbonates) overprinted by greenschist to lower amphibolite facies metamorphism. The mafic volcanic and dykes of NKS exhibit subalkaline basalts to basaltic andesites and a typical tholeiite compositional character. The chondrite‐normalized rare earth element pattern exhibits similar LREE‐enrichment and strong HREE‐fractionation, whereas primitive mantle‐normalized multi‐element patterns show pronounced LILE‐enrichment of Rb, Ba, Th, LREE, and HFSE depletion of Nb, K, P, and Ti. The Zr–Y–Nb–Th relationships indicate that both rock types were derived from the plume source, whereas low Nb/La (< 1), similar high large‐ion lithophile element concentrations, and pronounced negative Nb, Zr, P, and Ti anomalies suggest that components other than mantle plume must have been involved in the generation and evolution of both rock types, that is, most likely plume and subcontinental lithosphere mantle (SCLM) interaction. The genesis of parent magma for the NKS volcanic and dykes was derived by 4%–6% and 10%–20% partial melting from the spinel + garnet lherzolite stability field. The majority of the studied samples correspond to spinel + garnet peridotite melting on (Gd/Yb)N versus CaO/Al2O3 diagram, thereby corroborating residual garnet in the mantle restite. All the basalts and dykes from the NK section did erupt/intrude in an intracontinental rift setting based on geochemical discrimination. The key petro‐tectonic processes attributed to the formation of these rocks are as follows: (i) the melting of the ascending plume by adiabatic decompression; (ii) the partial melting of this plume–SCLM source in the melting regime, which produces basaltic magma with a tholeiitic composition; and (iii) the release of heat that provides the thermal condition for melting of SCLM and interaction between upwelling mantle plume and subduction metasomatized SCLM.

Formation of tributary junction fans of Spiti Valley cold desert, NW Himalaya: morphometric analysis of geomorphology and influencing factors

ABSTRACT Morphometric analysis of previously unresearched tributary junction fans (TJFs) of the Spiti valley cold desert, India, was conducted to understand the factors influencing their development. An integrated remote sensing and field approach was employed, including the development of multi-method morphometric indices viz. fan conicality (FCI), sweep angle (SA ), fan width-to-length ratio (W/L), feeder stream-order and valley floor width-to-height ratio (Vf ). Such TJFs, which are the most suitable cultivation and settlement sites in this region, were found to be largely polygenic and planimetrically confined, with many being multi-staged in terms of their development. The results of morphometric analyses reveal that the TJFs are relatively smaller but steeper than their counterparts in other settings, with high relative topographic confinement causing the construction of smaller and steeper fans. The competence of the feeder stream, along with associated processes, notably influences fan morphology using differential sediment transporting capacity. TJFs created by more competent streams are less steep, more influenced by topographic confinement and more vulnerable to truncation by the trunk stream. Furthermore, tectonically induced base-level fall and resultant downcutting in confined environments have caused the formation of truncated, multi-staged and entrenched fans and are primarily responsible for coupling between TJF catchments and trunk stream in the study area.

Land degradation vulnerability mapping using geospatial techniques: a case study of Nandakini River basin, NW Himalaya, India

ABSTRACT Land degradation is a significant global environmental issue, and its prevention has become a serious concern of the twenty-first century, particularly in the context of anthropogenic impact and climate change. It is crucial to map and assess the grade of land degradation to determine vulnerable areas. The Indian Himalayan region faces heightened risks with its steep terrain, active tectonics, heavy precipitation, and human interventions. This study focuses on the Nandakini Watershed. Employing AHP technique, the study calculates the Land Degradation Vulnerability Index (LDVI) using slope, terrain ruggedness, rainfall, temperature, LULC, soil depth, and organic carbon content. The results indicate that the upper region is highly vulnerable, and a higher slope influences the runoff in the area, followed by factors like NDVI and rainfall, collectively contributing to 62% of the overall index. In this context, the upstream regions of the watershed display a high LDVI, while most of the area falls within the low LDVI category. This indicates that approximately 2.10% of the study area is highly susceptible to soil erosion. RUSLE-based estimates have been used to further validate the LDVI result. The integrated LDVI offers a valuable tool for prioritising soil conservation and disaster mitigation.

South Tibetan Detachment System (STDS), NW Himalaya: A possible Cambro–Ordovician tectonic terrane boundary, and its Cenozoic remobilization

The South Tibetan Detachment System is an important extensional fault zone, separating the Greater Himalayan Sequence from the overlying Tethyan Himalayan Sequence, and is well exposed in the upper reaches of the Dhauliganga valley, NW Himalaya. This fault system is characterized by the occurrence of an extensive Cambro–Ordovician granite belt between Sutlej and Dhauliganga valleys, although only a few small granitoids intrude the high-grade mylonite gneiss of the Greater Himalayan Sequence in its immediate footwall. These bodies yielded U-Pb zircon crystallization ages between 498.92 ± 5.5 Ma and 486.54 ± 2.3 Ma. This work postulates that the South Tibetan Detachment System evolved as a major proto-tectonic marginal extensional terrane boundary during the Cambro–Ordovician Kurgiakh/Bhimphedian Orogeny, when it was the conduit for emplacement of the Cambro–Ordovician granite belt. Denudation of the Neoproterozoic Greater Himalayan Sequence and the Paleozoic granites on its footwall provided approximately ∼ 10 km thick sediments into the Tethyan Basin due to this fault system as a master growth fault. Reactivation of this fault system controlled further melting and emplacement of the Higher Himalayan Leucogranite belt during the Cenozoic. Zircon growth is observed in two distinct modes: pulsative from the Late Eocene to Early Oligocene, with peaks at 33.99 ± 1.07 Ma, 30.53 ± 0.32 Ma and 25.03 ± 0.54 Ma; and in the continuous mode from 23.68 ± 0.94 Ma to 13.30 ± 0.30 Ma, in the Miocene, for nearly 10.0 myr. These datasets reveal some of the oldest pulsative movements in the Late Eocene–Early Oligocene during crustal thickening, thrusting and associated metamorphism, followed by continuous extension during the Miocene. Data from the South Tibetan Detachment System are distinct in character, and do not support either its eastwards younging or diachronous movements along the Dhauliganga valley.

Earthquake-induced deformation structures along Trans-Yamuna active fault system: Doon Valley, NW Himalaya

Earthquake-induced deformation structures along Trans-Yamuna active fault system: Doon Valley, NW Himalaya

Application of Singular Spectrum Analysis to InSAR time-series for constraining the postseismic deformation due to moderate magnitude earthquakes: the case of 2019 Mw 6 Mirpur earthquake, NW Himalaya

Summary Detection and separation of the subtle postseismic deformation signals associated with moderate magnitude earthquakes from Interferometric Synthetic Aperture Radar (InSAR) time-series is often challenging. Singular Spectrum Analysis (SSA) is a statistical non-parametric technique used to decompose and reconstruct signals from complex time-series data. We show that the SSA analysis effectively distinguished the postseismic signal associated with the 2019 Mw 6 Mirpur earthquake from periodic and noise components. The SSA derived postseismic deformation signal is smoother and fits better to an exponential model with a decay time of 34 days. The postseismic deformation is confined to the southeast of the rupture area and lasted for ∼90 days following the mainshock. Inversion of the postseismic deformation suggests an afterslip mechanism with a maximum slip of ∼0.07 m on the shallow, up-dip portions of the Main Himalayan Thrust. The 2019 Mirpur earthquake and afterslip together released less than 12 per cent of the accumulated strain energy since the 1555 Kashmir earthquake and implies continued seismic hazard in the future.

Cathodoluminescence Petrography and Stable Isotope Geochemistry of Carbonate Rocks to Evaluate Diagenetic Evolution of the Middle Jurassic Samana Suk Formation (SSF), Kahi Section, Nizampur Basin, NW Himalayas, Pakistan

Cathodoluminescence Petrography and Stable Isotope Geochemistry of Carbonate Rocks to Evaluate Diagenetic Evolution of the Middle Jurassic Samana Suk Formation (SSF), Kahi Section, Nizampur Basin, NW Himalayas, Pakistan

Geomorphic assessment of sediment storage potential and mobilisation on the hillslopes of a mountain catchment: An example from Pranmati catchment, NW Himalaya

Sediment budgeting within a landscape is useful in understanding landscape evolution, and hazard prediction and assessment. It has been observed that only a fraction of the total volume of sediment produced within the system gets exported, implying that a part of the total volume of sediment is stored within the system. This sediment mass gets arrested and stored in compartments within the system and is mobilised during extreme stochastic events. These sediment storage compartments are poorly connected with the channel network and hence, do not supply sediment at steady rates. We have evaluated sediment connectivity and conducted field validation within a 93 km2 mountainous river basin (Pranmati catchment) in the NW Himalayas. This assessment relies on the Index of Connectivity (IC), computed through two methods: one employing the original framework and the C-factor from RUSLE, and the other utilizing a multiple flowpath model that incorporates Manning's roughness coefficient. We developed a storage potential index (SPI) by modifying the basic framework of index of connectivity; SPI indicates the potential of a point on the hillslope to arrest sediment flux and store it. Based on the difference of normalised IC and SPI, we have developed a sediment evacuation susceptibility index (ESIS) that indicates the susceptibility of various parts of the hillslope to get evacuated. Using ESIS, a sediment evacuation susceptibility zonation map was prepared that delineates areas on the basis of their stability.Our study indicates that sediment flux gets arrested at the (1) junction of land use and land cover units that have contrasting sediment transporting capacity, (2) grassland/barren land pockets surrounded by forests, (3) croplands, and (4) landslide debris deposits. The parts of the hillslope in the vicinity of the channel network and areas around steep surfaces are highly susceptible to sediment evacuation. Gentle sloped surfaces away from the channel network are relatively stable. Landslide debris are highly stable units of sediment storage.

Prediction of UCS and BTS under freeze-thaw conditions in the NW himalayan rock mass using petrographic analysis and laboratory testing

Repeated freeze-thaw (F&T) cycles substantially harm the durability of rocks, heightening the potential for landslides, rockslides, and avalanches. The current work investigates the effect of the F&T cycle on rock mass (biotite schist) samples. For this purpose, 32 rock samples were prepared and gathered from eight distinct locations in the northwest Himalayan region. For each sample, petrographical analysis and laboratory testing such as uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) are investigated at repeated (0th, 10th, 20th, and 30th) F&T cycles. Additionally, machine learning (ML) sequential models such as recurrent neural networks (RNN), gated recurrent units (GRU), and bi-directional long short-term memory (Bi-LSTM) are constructed to estimate the UCS and BTS under F&T conditions. Petrographical results show no change in the mineral indices, while there is a noticeable increase in aspect ratio but a significant decline in mean grain size with each successive 10th cycle, suggesting sample damage. The study also provides a comprehensive assessment of the ML models' performance, highlighting the Bi-LSTM model's superior accuracy among all models in terms of R2 (0.9850) and RMSLE (0.0100) during the TR stage and R2 (0.9020) and RMSLE (0.0170) during the TS stage for UCS prediction. Similarly, BTS prediction also shows superior precision, recording an R2 (0.7543) and RMSLE (0.0345) during TR and R2 (0.7404) and RMSLE (0.0213) during TS stages. The present study also explores the heatmap, line diagram, regression analysis, 2D kernel density plot, Taylor diagram, and DDR criterion for evaluating the model performance more clearly.

Unveiling the geoheritage, cultural geomorphology and geotourism potential of Zanskar region, NW Himalaya, India

The Zanskar region, nestled in the heart of the Tethyan Himalaya, represents a significant geological and cultural repository that has remained relatively unexplored by the global tourism industry. This study investigates Zanskar's geoheritage and cultural geomorphology, highlighting its importance for geotourism and advocating for the implementation of sustainable development to preserve its fragile ecosystem. Flowing northward from the Higher Himalayas, the Zanskar River, one of the largest northeast-flowing tributary of the Upper Indus River Basin (UIRB), traverses the complex, strongly folded, and thrusted Zanskar Range via a steep, narrow 60-kilometer-long gorge. Zanskar has consistently garnered attention from geoscientists and tourists owing to its unique geographic location and remoteness. Many areas and routes in Zanskar are challenging to reach, but it stands out as a prime location where glaciers can be accessed by road, making it an ideal destination for studying geoscience. Geologically, the study area is part of the Zanskar Range, with its boundaries defined by the Ladakh Range to the northeast and the Great Himalayan Range to the southwest. The Indus Tsangpo Suture Zone, the Tethyan Sedimentary Sequence, and the Higher Himalayan Crystalline Sequence are exposed from north to south. Zanskar serves as a pristine field museum for studying young Himalayan orogenic tectonics, featuring prominent exposures such as the Zanskar Shear Zone (ZSZ)/South Tibetan Detachment System (STDS) and the structural outcrop of Zangla, showcasing a variety of folding types. These folds signify different phases of deformation resulting from the Indo-Eurasian collision. Moreover, it serves as a prime sequence of Quaternary Glacial Periods (QGP), providing an ideal natural laboratory and an open, practical classroom for geoscientists and Earth science students. We propose ten geoheritage sites in Zanskar, which encompass cultural, geomorphological, and geological attractions with potential for geotourism in this region.

Detailed Investigation of Dolomites in the Middle Jurassic Samana Suk Formation, Kahi Section, Nizampur Basin, NW Himalayas, Pakistan

Detailed Investigation of Dolomites in the Middle Jurassic Samana Suk Formation, Kahi Section, Nizampur Basin, NW Himalayas, Pakistan

Fault system dynamics of the Kashmir, NW Himalaya, India using continuous GPS observations and geomorphic evidences

We collected data from the continuous Global Positioning System (cGPS) sites across the Kashmir Valley, situated at latitude 34◦N, spanning from 2008 to 2021. Inter-site velocities define a region of approximately 15,000 km2 with broadly distributed strain accumulation at −7.22×10−8 nano strain/year (compression component) and the maximum shear strain γmax of 1.9051×10−7 nano strain/year. The estimated site velocity in the ITRF14 ranges between 30.5±1–42.85±3 mm/yr. It was observed that the average deformation rate of the GPS sites in the Kashmir region ranges between 2.86±1–15.47±3 mm/yr relative to the India fixed reference frame, suggesting a predominant N-S directed compressional tectonic regime. The focal mechanism solutions of the earthquakes in and around the Kashmir Valley suggest dominant thrust faulting followed by normal faulting. Analysis of the vertical component of the GPS time series shows that the northwest segment of the valley subsides at the rate of −1.71± 0.70 mm/yr, while the southeast segment uplifts at the rate of 5.4 ± 0.5 mm/yr. In addition to vertical component, we observed differential movement of the sites relative to IISC site on the northwest and southeast segments. The rate of baseline change of the GPS sites indicates 7.30 ± 0.75 mm/yr extension in SE-NW direction and −5.32 ± 0.75 mm/yr NE-SW compression across and along the Kashmir Valley. Geodetic observations reveal a transition that aligns with the Magam lineament/fault previously identified by Ganju and Khar (1984) using gravity and magnetic data. The observation was supported by the field investigations and remote sensing techniques, confirming the existence of Magam Fault. During the field investigations, various geomorphic expressions of fault were observed, including fault ruptures, fault scarps, offset ridges, deflected drainages/rivers, linear alignment of springs, linear drainage lines, triangular facets and offset Recent sedimentary deposits (Karewas) were observed. The field evidence suggests exposure of normal faults at Kondabal, Nasrullapora, Biru and Radbugh. These exposed extensional structures, trends in NE-SW direction and dip in NW direction with varying offset and dip amount. GPS observations supplemented by geomorphic evidences infer the presence of normal fault ̴ 80 Km extending from northeast to southwest.

Comparative Structural Analysis of the Northern Potwar Deformed Zone and the Southern Potwar Platform Zone, NW‒Himalayas, Pakistan

Comparative Structural Analysis of the Northern Potwar Deformed Zone and the Southern Potwar Platform Zone, NW‒Himalayas, Pakistan

Geothermal resources and deep tectonic in Leh Ladakh (NW Himalaya), India: Inference from magnetotelluric studies

The geothermal resources and their connectivity with the deep tectonic are meaningful to understand through their structural geometry in the NW Himalayas. Therefore, over the NW-SE profiles, 23 audio Magnetotelluric (AMT) sites and over the SW-NE profile, 15 broadband Magnetotelluric (BBMT) sites were carefully chosen to provide the detailed structure. The electrical models were produced from a 2-D inversion algorithm based on the non-linear conjugate gradient method. The Chumathang-Mahe and Puga-Sumdo regions offer excellent geothermal potential as heat/fluid passes through the Mahe Fault (MF), Zildat Fault (ZF) and Kiagor Tso Fault (KTF). These faults are well revealed in the electrical models beneath the subsurface. The Puga Valley has an excellent geothermal resource at shallow depth. A ∼1000 m thick sulfide mineral body is defined with high conductivity (∼1 Ω-m). The crustal structure shows a highly conductive mid-crust beneath the Ladakh batholiths with no manifestation roots. The signs of the Indus-Tsangpo Suture Zone (ITSZ) and Shyok Suture Zone (SSZ) are well represented in the crustal model and are associated with the steep-dipping faults. The Chumathang-Mahe and Puga-Sumdo geothermal regions are connected with low resistivity body (C1) at shallow depths in the crustal model along the SW-NE profile and offer a path for deep fluid flow. The frictional heat generated in the process of the Indian plate subducting beneath the Tibetan plateau and the collision zone between India and Asia carried to melt. The high heat surface flow indicates the thermal origin of low resistivity. Thus, a ∼10 sq. km low resistivity reservoir is identified beneath the Tso Morari dome in the crustal model that overlies a resistivity feature. The high conductivity at mid-crust determined at active tectonic fabric may be potential geothermal resources yielding high well-productivity.

Geophysical delineation of the newly identified Gulmarg fault in the Kashmir Basin, NW Himalaya. Implications for active structural control

The Kashmir Basin, shaped by the collision of the Indian and Eurasian tectonic plates, features prominent faults, including the Balapur fault and other fault zones. This study focuses on the Gulmarg fault within the Northwestern Himalaya, using advanced geomagnetic techniques for delineation. Geomagnetic measurements reveal the characteristics of the newly identified Gulmarg fault. Ground magnetic surveys with Proton Precession Magnetometers along linear profiles and a magnetic grid highlight fault-related anomalies. The results indicate a fault running through the Gulmarg meadows, approximately 1.6 ​km from the Balapur fault, suggesting a potential coupling between the two. Three profiles across the fault exhibit distinctive magnetic variations, highlighting the intricate nature of the fault structure. Gridding methods also reveal anomalies associated with subsurface water and hydraulic activities, underscoring the importance of advanced geophysical techniques. This study emphasizes the significance of detailed investigations to unravel the complex geological processes shaping the Kashmir Basin. The study provides valuable insights into the tectonic activity in the Gulmarg region, underscoring the role of geophysical studies in enhancing our understanding of dynamic geological structures like the Gulmarg fault zone.

Sedimentological evidence of climate-tectonic interaction in the upper Satluj catchment of NW Himalaya

Sedimentological evidence of climate-tectonic interaction in the upper Satluj catchment of NW Himalaya