Himalayan Arc Research Articles

Retreat of Machoi Glacier, Kashmir Himalaya between 1972 and 2019 using remote sensing methods and field observations

Glaciers in the northwestern Himalayan region of Jammu and Kashmir have been reported to be retreating at higher rates as compared to other parts of the Himalayan arc. This study assessed area changes, frontal retreat, and geodetic mass balance of Machoi Glacier interspersed between the Greater Himalayan mountain range of Kashmir and Zanskar from 1972 to 2019. Further, the cryoconite, albedo, aerosol variability, and sediments in glacier ice were studied to correlate them with glacier recession. The glacier has lost an area of ~1.88 km2 (~29%) from 1972 to 2019 with a frontal retreat of 500 m at a rate of 10.6 m a−1. The geodetic mass balance analysis shows that the glacier surface lowered by 43.7 m losing 0.215 Gt from 2000 to 2011. The cryoconite holes on the glacier are mostly present in the ablation part having an average diameter of 5–7 cm. Both cryoconite holes and light-absorbing impurities in glacier ice show an inverse relation with altitude. Analysis of albedo data indicated no trend for the glacier, however, an insignificant decreasing trend was observed for the ablation zone of the glacier. The seasonal trends of albedo indicated a decrease during winter. The reanalysis data about aerosols indicated a significantly increasing trend from 1980 to 2018 and a decreased concentration in 2019 and 2020 owing to the prevailing COVID19 scenario. The receding glaciers in the region can severely impact the streamflow regimes, hydropower generation, and agriculture production in the region. However, more detailed in-situ data about glacier albedo, lithology, biophysical and chemical characterization of cryoconite holes, anthropogenic footprint and associated aerosol deposition needs to be generated to precisely ascertain their influence on glacier dynamics.

Ground Motion Prediction Equation For Earthquakes Along The Western Himalayan Arc

A critical element in seismic hazard estimation is the ground motion prediction equation (GMPE) which relates expected seismic intensity at a point from an earthquake of a given magnitude and location. Presently available GMPEs for plate interface thrust earthquakes along the Himalayan arc suffer from limited number of strong motion recordings used in their derivation. In this study we use a larger dataset, including recordings from the 2015 Gorhka, Nepal earthquake (M w 7.9) and some of its larger aftershocks, to derive GMPE for earthquakes along the Western Himalayan arc. The proposed GMPE should give more reliable estimation of ground motion parameters at hard sites along the arc and in Peninsular India, and at soft sites in the Indo-Gangetic Plains.

Joint inversion of ground gravity data and satellite gravity gradients between Nepal and Bhutan: New insights on structural and seismic segmentation of the Himalayan arc

Along-strike variation in the geometry of lithospheric structures is a key control parameter for the occurrence and propagation of major interplate earthquakes in subduction and collision zones. The lateral segmentation of the Himalayan arc is now well-established from various observations, including topography, gravity anomalies, exhumation rates, and present-day seismic activity. Good knowledge of the main geometric features of these segments and their boundaries is thus the next step to improve seismic hazard assessment in this area. Following recent studies, we focus our approach on the transition zone between Nepal and Bhutan where both M > 8 earthquakes and changes in the geometry of the Indian plate have been documented. Ground gravity data sets are combined with satellite gravity gradients provided by the GOCE mission (Gravity Field and Steady-State Ocean Circulation Explorer) in a joint inversion to assess the location and the geometry of this transition. We obtain a ca. 10 km wide transition zone located at the western border of Bhutan that is aligned with the Madhupur fault in the foreland and coincides with the Dhubri–Chungthang fault zone and the Yadong-Gulu rift in Himalaya and southern Tibet, respectively. This sharp segment boundary at depth can act as a barrier to earthquake rupture propagation. It can possibly restrict the size of large earthquakes and thus reduce the occurrence probability of M > 9 earthquakes along the Main Himalayan Thrust.

Föhn, fire and grazing in Southern Tibet? A 20,000-year multi-proxy record in an alpine ecotonal ecosystem

The lithology, ostracods, palynomorphs and black carbon of a sediment core from a saline wetland in the southern Tibetan highlands (29°14′33.40″N/87°13′09.10″E, 4480 m a.s.l., A.R. Xizang, China) is analyzed and climate modelling applied with respect to core questions in Quaternary research: (1) Do meso-climatic effects of regional landscape structures like high mountains overrule the effects of global climates? (2) Did life persist during the LGM? (3) Which shifts in ecosystems can be detected? (4) Does the fire-record testify for the presence of humans and their environmental impact? (5) How old is Neolithisation in the world’s largest highlands?The results of this integrated multi-disciplinary investigation revealed (1) the meso-climatic effect of the Himalayan arc’s relief channeled westerlies with West-Himalayan forest-pollen types into the southern Tibetan highlands, with (2) higher winter-precipitation, slightly lower summer precipitation, and the persistence of life for plants, and herbivores and therefore probably hunters. (3) The most arid period occurred between 17.8 and 15 cal kyr B.P., possibly synchronous with the Heinrich 1 event. Around 14.8 cal kyr B.P. humidity increased with torrential rains of high erosive power on sparsely plant-covered slopes and lasted until 4 cal kyr B.P. (4) The continuous fire-record proved the availability of combustible matter and a constant fire source which is believed to be human-attributed. Charcoal peaks around 17, 16 and 13 cal kyr B.P. remained sporadic until 11.5 cal kyr B.P. and attained the highest values since 8.7 cal kyr B.P. Black carbon increased steadily until 11 cal kyr B.P. and sharply peaked with high fluctuations around 10 cal kyr B.P., indicating high frequency intensive fires at the beginning of the Holocene. Between 10 and 6 cal kyr B.P. fire frequency decreases, with a slight peak around 4 cal kyr B.P. (5) The dawn of pastoralism in the early Mid Holocene Climatic Optimum dated back to 8.7 cal kyr B.P. with a decline of grass-pollen and the synchronous emergence of grazing weeds, leaving a perception gap of 5000 years between the palaeo-ecological and the archaeological state of the art.

Crustal structure of the Indian plate underneath the alluvial plains of the central Ganga basin by broadband magnetotellurics

The Ganga basin consists of thick Cenozoic sediments that mask the tectonic fabric of the underlying Indian plate. Despite the availability of fairly good information on the intra-basin structure, especially at the foothills of the Himalaya due to hydrocarbon exploration activities, very little is known about the basement and the crustal/lithospheric structure although composition and thermomechanical properties of the underthrusting Indian plate are expected to have a significant role in controlling the deformation and seismicity along the Himalayan arc. Here, we present a two-dimensional geoelectric model of the crustal structure along a 285-km-long profile across the central Ganga basin. The results were obtained by inversion of decomposed TE- and TM-mode impedance tensors derived from broadband magnetotelluric data recorded at 45 sites along the profile. The results reveal three main features: (i) the highly resistive Bundelkhand massif (BKC) extends northward beneath the sediments up to Lucknow; (ii) the massif is constituted of two blocks separated by a 10-km-wide moderately resistive nearly vertical zone; and (iii) a super-deep sedimentary basin constituted of highly conductive sedimentary succession exists in the northern segment of the profile. We report the presence of an electrical Moho at 40–45 km depth for the buried BKC and a crustal shear zone within the craton masked by the alluvial sediments. These results shall facilitate in furthering our understanding of the evolution of the BKC as well as the lithospheric/flexural deformation of the Indian continental lithosphere.

Reverse migratory behaviour of the earthquakes aftershock sequences along Himalayan Seismic Belt, Northwest Himalaya

The Anderson's theory (Anderson, 1951) can be utilized to understand the allocation of principal stresses. For various tectonic regimes, the global seismicity trend for crustal earthquakes of less than 20 km depth suggests that the source fault inclination also plays a critical part in the propagation of the aftershocks in the subsurface rupture with respect to the mainshock earthquake. It has also been observed that majority of the compression earthquakes that display upward seismicity migration typically occur along steep faults. However, in the context of Himalaya seismicity, the opposite migratory behaviour of the aftershock sequence is observed even along the gentle dipping source faulting. The failure envelope Mohr's diagram is used to understand the alteration in the dynamics of the subsurface locked zone of Himalayan Seismic Belt (HSB). This study discusses the alteration in the effective strength of the rock mass which imply the variation in the crustal hydrostatic fluid pressure at shallow depth (0–15 km). Different earthquakes and their aftershocks sequence of Himalayan terrain have been incorporated to corroborate the role of orientation of tectonic principal stresses, subsurface morphology and fluids/partial melts if present. In addition, topography contributes to the vertical loads and development of the subsurface geometry, therefore its role and its influence on seismicity has been discussed. This study highlights the controlling factors and the trend of the principal applied stresses and subsurface fluids in the distribution of aftershock sequences along tectonic regime of the Himalayan arc.

Distribution modelling and climate change risk assessment strategy for rare Himalayan Galliformes species using archetypal data abundant cohorts for adaptation planning

In a macroecological approach, we have used the data abundant species or archetypal cohorts as proxies for the data deficient species, to model their distributions. Upon successful modelling, we assessed climate change impacts on their distribution in the Himalayan arc extending from the Indian borders in the west to the hills in Myanmar. Out of 34 Galliformes species occurring in the Himalayan arc, 21 species were retained in this study, rest were dropped due to very low occurrences. Best performing variables from the set of environmental variables (n = 36) consisting of topography, vegetation, soil, anthropogenic indices and bioclimatic factors were tested for collinearity. Ordination (PCA and NMDS) and clustering (hierarchical clustering, agnes, partitioning around medoids and k–means clustering) and Species Archetype Modelling (SAM) methods were performed for finding the archetypal cohorts among the species. The clusters were used for two different modelling frameworks- Species Distribution Models (SDMs) with a combination of biophysical and topographical parameters; and Bioclimatic Envelope Models (BEMs) with only bioclimatic variables. Predicted climate-driven changes in species ranges (year 2070, RCP 4.5 and 8.5) were assessed. The 21 species were clustered in four groups. Precipitation emerged as the overall significant driving factor for all the three clusters. Random Forest was the highest performing model across the clusters. Two cluster restricted to the eastern Himalayas were found to be the most affected in a climate change scenario. Cluster belonging to the western Himalayas was predicted to lose about 70% of its bioclimatic habitats in both the scenarios. In a first attempt, this study presents a novel approach towards distribution and climate change modelling for the rare Galliformes, using abundant Galliformes over a pan Himalayan scale.

A 2600-year-long paleoseismic record for the Himalayan Main Frontal Thrust (western Bhutan)

Abstract. In spite of an increasing number of paleoseismic studies carried out over the last decade along the Himalayan Arc, the chronology of historical and prehistorical earthquakes is still poorly constrained. In this paper, we present geomorphologic and paleoseismic studies conducted over a large river-cut exposure along the Main Fontal Thrust in southwestern Bhutan. The Piping site reveals a 30 m high fault-propagation fold deforming late Holocene alluvial deposits. There, we carried out detailed paleoseismic investigations and built a chronological framework on the basis of 22 detrital charcoal samples submitted to radiocarbon dating. Our analysis reveals the occurrence of at least five large and great earthquakes between 485±125 BCE and 1714 CE with an average recurrence interval of 550±211 years. Coseismic slip values for most events reach at least 12 m and suggest associated magnitudes are in the range of Mw 8.5–9. The cumulative deformation yields an average slip rate of 24.9±10.4 mm yr−1 along the Main Frontal Thrust over the last 2600 years, in agreement with geodetic and geomorphological results obtained nearby.

Impacts of Topographic Relief and Crustal Heterogeneity on Coseismic Deformation and Inversions for Fault Geometry and Slip: A Case Study of the 2015 Gorkha Earthquake in the Central Himalayan Arc

AbstractFault source models inverted from surface displacement measurements are a common tool to contextualize the seismotectonic significance of earthquakes. However, these models commonly invoke a simplified homogeneous elastic half‐space (flat Earth) description of Earth, which may bias the resulting fault geometries and slip distributions in the presence of spatially varying Earth's elastic structure and topography. Here, we developed both forward and inverse three‐dimensional finite‐element models with planar faults to systematically assess the impacts of topography, crustal elastic structure, and fault geometry on surface deformation and earthquake source inversions, with a focus on the 2015 Gorkha, Nepal earthquake. Our forward models with fixed fault slip confirm the impacts of topography and crustal heterogeneity on surface deformation. These impacts, however, contribute only maximally ∼10% of the total surface displacement, and the fault depth and dip dominantly control the coseismic deformation for the Gorkha case. When using homogeneous half‐space models to invert the synthetic displacement fields generated by forward finite‐element models, we find that ignoring crustal heterogeneity primarily biases inferred dip angle, while ignoring relief primarily biases inferred fault depth. Our inversions based on finite‐element models suggest that topography and crustal heterogeneity introduce negligible bias on recovering the Gorkha line of sight observations. Fault dip angle and depth can systematically trade off with slip area and slip magnitude, regardless of the presence of relief and crustal heterogeneities. Taken together, our findings highlight the importance of fault geometry on inverted fault kinematics with geodetic observations in the central Himalayan arc.

Probing time-dependent afterslip and viscoelastic relaxation following the 2015 Mw7.8 Gorkha earthquake based on the 3-D finite-element model

We analyzed daily displacement time series from 34 continuous GPS stations in Nepal and 5 continuous GPS stations in South Tibet, China, and extracted the first 4.8 years of postseismic motion after the 2015 Mw7.8 Gorkha earthquake. With the longer duration GPS observations, we find that postseismic displacements mainly exhibit southward and uplift motion. To study the postseismic afterslip and viscoelastic relaxation, we built a 3-D spherical finite-element model (FEM) with heterogeneous material properties and surface topography across the Himalayan range, accounting for the strong variations in material properties and surface elevation along the central Himalayan arc. On the basis of the FEM, we reveal that the predicted viscoelastic relaxation of cm level moves southward to the north of the Gorkha earthquake rupture, but in an opposite direction to the observed postseismic deformation in the south; the postseismic deformation excluding viscoelastic relaxation is well explained by afterslip downdip of the coseismic rupture. The afterslip is dominant during 4.8 years after the 2015 Mw7.8 Gorkha earthquake; the contribution by the viscoelastic relaxation gradually increases slightly. The lack of slip on a shallow portion and western segment of the MHT during and after the 2015 Gorkha earthquake implies continued seismic hazard in the future.

Crustal deformation rates in Kashmir valley and adjoining regions from continuous GPS measurements from 2008 to 2019

We present GPS velocities in Kashmir valley and adjoining regions from continuous Global Positioning System (cGPS) network during 2008 to 2019. Results indicate total arc normal shortening rates of ~ 14 mm/year across this transect of Himalaya that is comparable to the rates of ~ 10 to 20 mm/year reported else-where in the 2500 km Himalaya Arc. For the first time in Himalayas, arc-parallel extension rate of ~ 7 mm/year was recorded in the Kashmir valley, pointing to oblique deformation. Inverse modeling of the contemporary deformation rates in Kashmir valley indicate oblique slip of ~ 16 mm/year along the decollement with locking depth of ~ 15 km and width of ~ 145 km. This result is consistent with the recorded micro-seismicity and low velocity layer at a depth of 12 to 16 km beneath the Kashmir valley obtained from collocated broadband seismic network. Geodetic strain rates are consistent with the dislocation model and micro-seismic activity, with high strain accumulation (~ 7e−08 maximum compression) to the north of Kashmir valley and south of Zanskar ranges. Assuming the stored energy was fully released during 1555 earthquake, high geodetic strain rate since then and observed micro-seismicity point to probable future large earthquakes of Mw ~ 7.7 in Kashmir seismic gap.

Great Pending Himalaya Earthquakes

Abstract Geological, historical, and geophysical observations show that the entire Himalayan arc is poised to produce a sequence of great earthquakes, possibly similar to that which occurred in the twentieth century along the Aleutian subduction zone. The human catastrophe in the densely populated countries astride the arc is likely to be unprecedented when these earthquakes occur.

How many tree species are in the Himalayan treelines and how are they distributed?

Increase in endemism with elevation is a common feature in Himalayas because of increased isolation of higher areas like treelines. To protect species of treeline, we at least need to record their numbers and distribution. We estimated that the total number of tree species in Himalayan treeline is 58, and they belong to 14 genera and 8 families. It is impressive, given that globally alpine treeline species richness is unlikely to be considerably higher than 100. While estimating the species number, we confronted uncertainties in some cases concerning synonyms of species, weak demarcation between species and incorrect identification. Because of a high species differentiation in the Hengduan Mountains and Western Sichuan Province in Tibet, the eastern part of the Himalayan arc (88°E and more) has much higher species richness than the western part (less than 88°E), despite similar number of genera. These areas of high species differentiation accounted for nearly half of the total species. The dominant genera in terms of geographical distribution are Juniperus, Abies, Rhododendron, and Betula. Among the families, Pinaceae, Cupressaceae, Ericaceae, Betulaceae, and Rosaceae were prominent. Because of global climatic change, species shifts are predicted to occur along an altitudinal gradient (representing temperature gradient) as well as along the 31o longitudinal range, representing a moisture gradient. The Himalayan treelines are relatively species-rich, largely because of variations in precipitation, topography, continentality, and cultural factors, among others along the east-to-west arc. There is a need to undertake additional taxonomic studies, using tools such as molecular techniques to provide solution to confusion relating to incorrect identification of some species.

Spatial distribution of earthquake potential along the Himalayan arc

To determine the spatial distribution of earthquake potential along the active Himalayan arc, we utilize GPS measurements and earthquake data. We derive horizontal velocity field and 2-D strain rates from a new set of 41 regional GPS stations along with 446 published velocities. We convert these strain rate tensors to geodetic moment rate build-up within 24 contiguous segments and compare to the seismic moment rate release derived from a reassessed earthquake catalog of 900 years. The geodetic to seismic moment rate ratio, an indicator of stored strain energy, varies from below unity to more than 50 in different segments. The estimated geodetic moment rate ranges from 1.7 × 1018 Nm/yr to 10.2 × 1018 Nm/yr, whereas the seismic moment rate ranges from 3.7 × 1016 Nm/yr to 5.1 × 1019 Nm/yr. This variation between the geodetic and seismic moment rate corresponds to a moment deficit rate of ~1.15×1017 Nm/yr to 7.97 × 1018 Nm/yr along various segments of the study region. The above moment deficit rate provides an equivalent earthquake potential of magnitude 5.7 − 8.2 in different segments. Specifically, the higher earthquake potential (Mw≥8.0) corresponds to the segments in the central seismic gap and the northeast part of Himalaya, whereas the lower earthquake potential (Mw<7.0) corresponds to the segments encompassing the rupture areas of recent large events. The present findings not only provide input constraints on the contemporary crustal deformation but also contributes to the time-dependent seismic hazard analysis along the Himalaya.

GPS derived crustal velocity, tectonic deformation and strain in the Indian Himalayan arc

The present study elucidates velocity of the Indian plate from 2013 to 2016 with the help of six continuously operating permanent Global Positioning System (GPS) stations and tracks the crustal motion and direction directly by means of space-based geodetic measurements. The GPS derived velocity estimates were computed with respect to 2008 International Terrestrial Reference Frame (ITRF 08) and carried out almost all along the arc in the Indian Himalayan Region (IHR). The velocity vectors indicate that the Indian plate is moving towards the NE direction (average velocity of 46.95 ± 0.23 mm/yr) with higher movement towards the eastward direction (36.11 ± 0.17 mm/yr) compared to the northward direction (29.02 ± 0.16 mm/yr). Variations in the plate motion between IISC and permanent GPS stations suggest that presently, the convergence rate is about 8.06 ± 0.28 mm/yr and 5.71 ± 0.17 mm/yr for Higher Himalaya and Lesser Himalaya respectively. In addition, the deformation rate was also calculated on the basis of baseline shortening between IGS stations (IISC and LHAZ) and permanent GPS stations. The results suggest that the deformation is about 11.68 ± 1.32 mm/yr above the Main Central Thrust (MCT) and 6.74 ± 1.20 mm/yr above the Main Boundary Thrust (MBT) with respect to the Indian plate (IISC), while it is 20.60 ± 1.76 mm/yr above the MCT and 11.42 ± 1.21 mm/yr above the MBT with respect to Eurasian plate (LHAZ). The strain rate through GPS measurement reveals that the maximum strain is accumulated in the central part of the Himalaya between the MBT and MCT, indicating vulnerability of the central Indian Himalaya for future earthquakes.

Late Pliocene onset of the Cona rift, eastern Himalaya, confirms eastward propagation of extension in Himalayan-Tibetan orogen

Several competing hypotheses have been proposed to explain east-west extension observed across the Himalayan orogen, based primarily on observations from the western and central Himalaya. They make predictions for the temporal and spatial patterns of deformation in the eastern Himalaya. These tectonic models include radial spreading or oroclinal bending of the Himalayan arc, oblique convergence of the Indian continent, tearing or lateral detachment of the Indian slab and eastward flow of lithosphere. Here, for the first time we constrain the activity history of the Cona rift, the only north-trending rift currently recognized in the eastern Himalaya, based on biotite and K-feldspar 40Ar/39Ar and zircon and apatite (U–Th)/He thermochronology, to evaluate these proposed rifting mechanisms. Low-temperature thermochronological results suggest that the Cona rift is the youngest rift system in the Himalayas: after a slow phase of exhumation since ∼14 Ma (∼0.2–0.13 mm/yr), normal faulting initiated here at ∼3.0–2.3 Ma with a fault slip rate of ∼3.8–1.6 mm/yr and a horizontal extension magnitude of ∼2–5 km. Analysis of rifting across the Himalayas shows that rift initiation ages young eastward, which is matched by eastward decreasing rift-extension magnitudes. Monotonically eastward younging rift development is consistent with the tectonic model involving eastward lithospheric flow driven by Indian slab dynamics and coupled asynchronous gravitational potential energy gradients.

Himalayan cross faults affect thrust sheet geometry: An example from the Munsiari thrust sheet near the Gish Transverse fault zone, frontal Darjiling Himalaya, India

The Munsiari thrust (MT) sheet is a dominant thrust sheet in the Himalaya and forms the frontal ridge in the Gorubathan recess of the Darjiling Himalaya. The geometry of the MT sheet in the recess was poorly constrained thereby inhibiting the understanding of how the geometry and kinematics of the sheet varied from the Nepal to the Bhutan Himalaya. We present new structural data and infer the deformation mechanisms and the geometry of the MT sheet in the Gorubathan recess in the Darjiling Himalaya to fill this knowledge gap. The MT sheet was dominated by large-scale, overturned antiforms and synforms. The entire MT sheet was later folded to a north-easterly plunging synformal fold with NE-SW axial trend due to the effect of a Himalayan cross fault in the region named the Gish Transverse fault. A new brittle, out-of-sequence and neotectonically active, Phaparkheti thrust, was recognized in the MT sheet. Deformation microstructures indicate that the temperature of deformation in the MT fault zone and the sheet was ~500 °C to 700 °C and ~400 °C, respectively. Our approach of first mapping major and minor structures and then integrating these studies with deformation microstructure and tectonic geomorphology data resulted in an improved understanding of the structural characteristics of the MT sheet in the Darjiling Himalaya. Our study also suggests that there is considerable variation in the geometry and kinematics of frontal thrust sheets along the Himalayan arc that must be studied systematically in the context of Himalayan salients and recesses.

Understanding and managing earthquake hazard visa viz disaster mitigation strategies in Kashmir valley, NW Himalaya

Kashmir valley lies in the Northwest part of the seismically active Himalayan arc, is vulnerable to earthquakes both from near and far seismogenic sources owing to its unique geological, geographical and seismotectonic setting. The area has witnessed numerous colossal earthquakes throughout its prolific geological past causing severe damage to natural and built environment with intensity levels ranges between VIII–X. Recent data of instrumental seismicity shows that very high peak ground accelerations can be generated by relatively moderate (Mw 6.5–7) earthquakes in this region due to geological/geotechnical aspects of the subsurface stratum. With unplanned and unscientific constructional patterns and tremendous increase in population since last major earthquake combined with warning level of seismic hazard and high liquefaction potential index leads to the insecure future of the region. In this context, a critical review of the historical damaging earthquakes as well as overview of future potential earthquake scenario is presented to review and update the current disaster management scenario of the region. This paper highlights the effective disaster risk reduction and management systems on sound institutional capacities by key actors at different levels (State, Division, District, Municipal, Community and Block levels) to adverse the impacts of earthquake hazards within the broad context of sustainable development of the region.

Disparate behaviour of deformation patterns beneath northeast Indian lithosphere inferred from shear wave splitting analysis

New shear wave splitting measurements are obtained from the North East Indian region utilizing the core refracted PKS/SKS/SKKS phases, suggesting the region as more complex and anisotropic in nature. The splitting parameters namely time delays (δt) and fast polarization directions (ϕ) are computed at nine stations and the results are found to be more consistent with the geologic/tectonic structures and present mantle deformation patterns under this particular region. The result streamlines the deformation patterns strictly into three categories. Significant anisotropy in the western fringe of Shillong plateau and surrounding regions implies an asthenospheric flow related strain dominating the splitting direction inline the direction of absolute plate motion (APM) of the Indian plate in a no net reference frame and discards the effects from lithospheric strain. The stations in Himalayan collision zone redefines an actual deformation pattern in ENE-WSW direction in line with the maximum shear plane construing the Himalayan arc at the northeast corner as a consequence of N-S Indo-Eurasian collisional derived lithospheric strain. The anisotropic effect at the Himalayan foredeep section signifies the lithospheric strain induced E-W deformation from N-S continental collision. Mapping the anisotropic layer depth under these stations also strengthens our anisotropic observations and geodynamics understanding of this region with a similar thought of ideas where the deformation patterns are supposed to be dominated by huge forces like APM and lithospheric strains with negligible effects from the local geological structures.

Cryosphere-Fed Irrigation Networks in the Northwestern Himalaya: Precarious Livelihoods and Adaptation Strategies Under the Impact of Climate Change

Irrigated agriculture is crucial for the livelihood security of mountain communities in the northwestern part of the Himalayan arc and adjoining regions of the Karakoram Hindu Kush and Trans-Himalaya. Using meltwater from glaciers, snow, and permafrost, mountain dwellers have developed sophisticated techniques to cope with recurrent water scarcity caused by glacier retreat, glacier thinning, and seasonal snow-cover dynamics. Based on case studies from the Nanga Parbat region, Hunza-Karakoram, and Ladakh, this paper seeks to identify general patterns and site-specific characteristics of agrarian practices and adaptation strategies in the face of climate change. The comparative case study approach reveals differing responses to water scarcity, which depend on local conditions and include the construction of new irrigation channels, installation of pipes, and building of artificial ice reservoirs. The biophysical investigation is supplemented by an exploration of socioeconomic factors and is based on long-term research in the 3 study areas. The methods used include multitemporal remote sensing analysis, mapping of natural water storage components and irrigation infrastructure, and interviews. Taking into consideration social factors such as the expansion of off-farm income opportunities and market integration, we identify key variables that affect the sustainability and resilience of land use systems. Outcomes are diverse, ranging from the intensification and extension of irrigated mountain agriculture to the abandonment of irrigated areas, depending on local sociohydrological settings.