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Main Himalayan Thrust

The Main Himalayan Thrust (MHT) is a major low-angle décollement thrust fault system that underlies the approximately 2,400 km-long Himalayan orogenic belt, serving as the primary basal interface where the Indian tectonic plate underthrusts beneath the Eurasian Plate.^[1] This convergence occurs at a rate of 15–21 mm per year, driving the formation and ongoing uplift of the world's highest mountain range.^[2] The MHT dips gently northward at angles typically ranging from 3° to 10°, extending from shallow depths of about 10 km near the southern Himalayan foothills to over 30 km beneath southern Tibet.^[3]^[4] Structurally, the MHT consists of alternating flat segments and steeper ramps, with its near-surface expression manifesting as the Main Frontal Thrust (MFT), the southernmost active fault of the system.^[3] These ramps, such as the prominent Lesser Himalayan ramp, control the propagation of seismic ruptures and contribute to the topographic relief of the range.^[5] The fault soles into the upper crust and is overlain by splay thrusts like the Main Boundary Thrust (MBT) and Main Central Thrust (MCT), which together form a wedge-shaped duplex structure accommodating much of the orogenic shortening.^[4] The MHT is seismically active, hosting locked zones up to 100–150 km wide that accumulate interseismic strain, leading to great earthquakes such as the 1934 Mw 8.1 Bihar-Nepal event and the 2015 Mw 7.8 Gorkha earthquake.^[4] Its geometry varies along strike, with segmentation influenced by lateral changes in dip and crustal structure, which may limit rupture lengths and affect seismic hazard assessment across the densely populated Himalayan arc.^[5] Ongoing geophysical studies, including seismic imaging and GPS monitoring, continue to refine models of its depth and coupling to mitigate risks from potential future megathrust events.^[2]

Geological Context

Tectonic Setting

The Main Himalayan Thrust (MHT) forms a critical component of the tectonic framework resulting from the ongoing collision between the Indian and Eurasian plates, which initiated approximately 50 million years ago during the early Eocene. This collision marked the closure of the Tethys Ocean and the onset of the Himalayan orogeny, a process that has led to the uplift of the Himalayan mountain range and the Tibetan Plateau through continental crust thickening and shortening.^[6] The convergence transformed the region into one of the most active orogenic belts on Earth, with the Indian plate's northward motion driving compressive deformation across a vast area spanning over 2,500 kilometers.^[7] Currently, the Indian plate converges with the Eurasian plate at a total rate of approximately 40–50 mm per year, of which about 15–21 mm per year is accommodated across the Himalayan arc, as measured by global positioning system (GPS) and geodetic data.^[8] This motion results in the underthrusting of the Indian continental crust beneath the Eurasian plate, with the bulk of the convergence across the arc accommodated at depth along the MHT, a basal décollement that extends from the surface frontal thrusts to mid-crustal levels. The underthrusting occurs at a shallow angle, typically 5-10 degrees initially, facilitating the transfer of stress and strain from the plate boundary into the overlying Himalayan wedge.^[9] Approximately half of the total convergence contributes to active shortening and uplift in the Himalaya, while the remainder is absorbed further north in Tibet through distributed deformation.^[10] The MHT serves as the primary décollement surface, a low-angle detachment horizon within the upper crust that accommodates about 20 mm per year of horizontal shortening through slip along its plane. This slip budget underscores the MHT's role in partitioning the plate convergence, with interseismic locking along portions of the fault leading to strain accumulation that is released in great earthquakes. At the surface, the MHT manifests through a series of splay faults, including the Main Frontal Thrust (MFT) to the south, which represents the active southern margin of the orogen and absorbs the majority of recent shortening, and the Main Central Thrust (MCT) further north, which marks a major shear zone separating the High Himalaya from the Lesser Himalaya and connects directly to the MHT at depth. These structures collectively illustrate the MHT's influence on the surface architecture of the Himalayan thrust belt.^[11]^[12]

Formation and Evolution

The formation of the Main Himalayan Thrust (MHT) began with the initial collision between the Indian and Eurasian plates around 50-55 million years ago (Ma) during the Eocene epoch, marking a pivotal shift from intra-oceanic subduction to continental collision.^[13] This event followed the closure of the Neo-Tethys Ocean, as the leading edge of the Indian plate, previously subducting beneath Eurasia, transitioned into a regime of continental convergence, initiating widespread deformation across the proto-Himalayan region.^[14] Evidence for this timing includes the appearance of arc-derived detritus in northern Himalayan sedimentary sections as early as ~51 Ma and southward-younging disconformities dated 68-56 Ma, reflecting the onset of flexural loading and forebulge migration.^[14] The MHT evolved as a basal décollement underlying the Himalayan thrust wedge, accommodating underthrusting of the Indian continental crust beneath the Eurasian margin and progressive wedge thickening over approximately 20-30 Ma, primarily from the late Eocene onward.^[13] This structure developed through episodic slip along a low-angle detachment within the weakened upper Indian crust, facilitating the southward propagation of deformation and the stacking of thrust sheets that built the orogenic wedge.^[14] Key evolutionary stages include the Eocene phase of initial collision and metamorphism (~50-45 Ma), which established the foundational décollement; Miocene thrusting initiation (~23-16 Ma), characterized by intensified activity along major faults like the Main Central Thrust and uplift of intermontane basins such as the Kailas by over 4 km; and Quaternary surface faulting, where deformation reached the foreland, emerging along the Main Frontal Thrust.^[13]^[14] Stratigraphic records provide critical evidence for this evolution, particularly the deposition of Siwalik Group sediments in the Himalayan foreland basin from the Middle Miocene to Pleistocene, which records the influx of synorogenic detritus derived from eroding thrust wedges and reflects the timing of wedge progradation and basin filling.^[13] Similarly, the uplift of the Tibetan Plateau, linked to underthrusting along the MHT, is evidenced by low-relief paleosurfaces around 45 Ma transitioning to high-elevation conditions by the Miocene, supported by sedimentary, geochronologic, and isotopic proxies indicating phased exhumation and crustal thickening.^[14] These records underscore the MHT's role in driving long-term orogenic growth without invoking speculative mechanisms beyond observed tectonic processes.^[13]

Structural Characteristics

Geometry and Extent

The Main Himalayan Thrust (MHT) extends approximately 2,400 km along the arcuate structure of the Himalayan range, spanning from Nanga Parbat in the northwestern syntaxis to Arunachal Pradesh in the eastern syntaxis.^[15] This vast reach accommodates the ongoing convergence between the Indian and Eurasian plates, forming the basal décollement that underlies the entire orogenic wedge. The fault strikes northwest-southeast, following the convex southward arc of the Himalaya, and dips gently northward at angles of 5–10° beneath the Tibetan Plateau.^[16] Seismic reflection profiles reveal a characteristic flat-ramp-flat geometry for the MHT, with shallow ramps emerging at depths of 10–20 km that connect to a deeper basal flat segment at 20–30 km.^[17] In cross-section, the upper portions feature north-dipping ramps of 20–30° that facilitate splay thrusts, including frontal ramps linking to the Main Frontal Thrust at the surface, while the lower flat maintains a low-angle detachment.^[2] Recent thermokinematic models (as of 2024) indicate 10–15 km of out-of-sequence thrusting on the Main Central Thrust system in central Nepal, refining the overall wedge structure.^[2] This configuration supports the southward propagation of deformation, with the ramps driving uplift and the flats enabling aseismic creep at greater depths. The MHT exhibits segmentation along its strike into western (Kashmir-Garhwal), central (Nepal), and eastern (Sikkim-Bhutan-Arunachal) portions, marked by lateral variations in geometry that influence rupture propagation.^[16] Dip angles show regional differences, with gentler inclinations in the Bhutan segment (e.g., ~3°) compared to profiles elsewhere.^[18] These segments are bounded by tear faults or abrupt changes in fault plane attitude, contributing to heterogeneous seismicity patterns.

Thrust Mechanics

The Main Himalayan Thrust (MHT) exhibits velocity-weakening frictional behavior within its seismogenic zone, typically at depths of 5–20 km, where increasing slip velocity leads to reduced friction and promotes unstable slip.^[19] This frictional instability facilitates stick-slip events, characterized by periods of interseismic locking where the fault accumulates elastic strain, followed by rapid coseismic release during earthquakes that can produce slips of 5–8 m or more.^[19] At greater depths, below approximately 20 km, the behavior transitions to velocity-strengthening due to elevated temperatures, enabling stable aseismic creep that limits rupture propagation.^[19] Compressional forces arising from the ongoing convergence between the Indian and Eurasian plates, at a rate of approximately 15–21 mm/year, drive the accumulation of shear stress along the MHT fault plane.^[2] This tectonic loading builds deviatoric stresses in the mid-crust, estimated at less than 35 MPa under low-friction conditions (coefficient <0.3), though models indicate potential accumulation up to 100–200 MPa in stronger crustal segments over seismic cycles.^[20]^[21] The resulting stress regime is dominantly thrust-faulting, with low effective friction facilitated by elevated pore pressures near lithostatic levels, allowing the MHT to accommodate much of the plate motion despite its locked state.^[20] The deformation cycle on the MHT involves interseismic strain buildup, coseismic rupture, and post-seismic relaxation, with the latter occurring primarily through viscoelastic flow in the lower crust at depths exceeding 20 km.^[22] This relaxation redistributes stress, promoting aseismic slip and contributing to strain release over the earthquake cycle, as inferred from postseismic deformation following events like the 2015 Gorkha earthquake.^[22] Viscoelastic processes, modeled with effective viscosities of 3×10^{16}–3×10^{17} Pa·s, extend deformation northward beyond the rupture zone, unloading stress in deeper sections while reloading shallower ones over decades.^[22] The ramp-flat geometry of the MHT significantly influences slip propagation, with flat segments facilitating aseismic creep and ramps acting as geometric asperities that enhance locking during interseismic periods.^[11] These ramps, often located in the mid-crust, accumulate stress more rapidly due to fault bends, arresting partial ruptures or nucleating seismicity, as observed in dynamic models of the 2015 Gorkha event.^[11] During coseismic slip, the geometry can channel propagation along flats but impede it across ramps, leading to heterogeneous rupture patterns and aftershocks concentrated at structural transitions.^[11]

Seismicity

Historical Earthquakes

The Main Himalayan Thrust (MHT) has been the source of several great pre-instrumental earthquakes, documented through historical accounts and paleoseismic investigations. These events highlight the thrust's capacity for large-magnitude ruptures, often exceeding magnitude 8, with surface displacements preserved in geomorphic features. Key examples include the 1505 Lo Mustang earthquake, estimated at magnitude ~8.2, which caused widespread devastation across western Nepal and Tibet, including landslides that blocked rivers and damaged monasteries.^[23] Paleoseismic trenching in far-western Nepal has identified potential surface rupture along the Main Frontal Thrust branch of the MHT, with offsets suggesting coseismic slip of several meters over a length of approximately 200-400 km.^[24] Subsequent major events include the 1803 Garhwal earthquake (magnitude 7.8), which struck the Kumaon-Garhwal region in northern India, producing intensities up to X on the Modified Mercalli scale and triggering numerous landslides.^[23] Paleoseismic evidence from trenches across the Kaladungi Fault, a splay of the MHT, confirms surface rupture for this event, with tightly bracketed radiocarbon ages and fault displacements indicating a rupture length of about 200 km.^[25] The 1833 Kathmandu earthquake (magnitude 8.0) devastated the Kathmandu Valley, destroying temples and palaces, with historical records noting ground fissuring and sand boils.^[26] Intensity distributions suggest a rupture centered northeast of Kathmandu, extending roughly 200-300 km along the MHT, consistent with subsurface slip patterns inferred from later analogs.^[23] The 1934 Bihar-Nepal earthquake (magnitude 8.1), though early instrumental, draws from historical eyewitness accounts of severe shaking; it ruptured approximately 200-400 km along the MHT, producing up to 6 m of surface offset at sites like Sir Khola.^[27] Paleoseismic studies, particularly trenching across the MHT's frontal strands, reveal a recurrence interval of 500-1,000 years for magnitude >8 events along central segments in Nepal and Bhutan.^[28] For instance, excavations at Patu and Bardibas thrusts indicate 5-7 great earthquakes over the late Holocene, with average intervals of 750 ± 140 years at one site and 870 ± 350 years at another, based on colluvial wedges and offset fluvial features.^[29] A 2,600-year record from western Bhutan identifies five events with slips ≥12 m, yielding an average recurrence of 550 ± 211 years for large ruptures.^[28] Historical accounts document intense shaking and structural damage in the Kathmandu Valley from earlier events, such as the AD 1255 earthquake, which killed one-third of the population including King Abhaya Malladeva, and the AD 1344 earthquake, which toppled the king and widespread buildings the following day.^[29] These intensity distributions, corroborated by paleoseismic offsets of ~6 m at Sir Khola, suggest ruptures propagating to the surface along the central MHT, affecting a broad area with coseismic uplift.^[23] Segmentation along the MHT influences recurrence patterns, with western segments (e.g., eastern Nepal) showing shorter intervals of 700-900 years based on fault scarps displacing alluvial fans by ~5.5 m, while eastern segments (Darjeeling-Sikkim Himalaya) exhibit longer intervals of 949-1,963 years, evidenced by higher scarps (15-18 m) truncating alluvial terraces.^[9] These differences arise from transverse structures like the Munger-Saharsa Ridge and Dhubri-Chungthang Fault Zone, which act as barriers limiting rupture propagation and creating distinct seismic behaviors.^[9]

Modern Seismicity Patterns

The instrumental seismic record along the Main Himalayan Thrust (MHT) since the early 20th century highlights several major thrust earthquakes that ruptured shallow portions of the fault at depths of 10-20 km. The 1905 Kangra earthquake (Mw 7.8) involved thrust faulting on the MHT beneath the northwest Himalaya, with a rupture area of approximately 280 km × 80 km that did not propagate to the surface. Similarly, the 1947 Assam earthquake (Mw 7.3) ruptured a segment of the MHT in the eastern Himalaya through oblique-thrust mechanisms at shallow depths.^[30]^[31] The 2015 Gorkha earthquake (Mw 7.8) in central Nepal exemplifies modern events, nucleating at ~15 km depth on a locked downdip portion of the MHT and propagating unilaterally eastward along a ~150 km × 70 km patch.^[32]^[31]^[33] Seismicity distribution along the MHT shows elevated activity concentrated in locked asperities, with prominent clusters in the Kashmir, Nepal, and Bhutan regions corresponding to historical rupture zones, while a notable low-seismicity gap spans ~650 km in the central Himalaya. These locked patches, identified through geodetic inversions and earthquake relocations, exhibit high interseismic coupling (up to 80-100%) that accumulates strain for future events, contrasting with creeping sections that release stress aseismically. Background microseismicity (M < 4) further delineates these segments, with denser swarms along the edges of locked zones indicating stress transfer.^[16]^[34] The seismic moment release rate along the MHT arc is estimated at approximately 10^{18} Nm/year, reflecting partial coupling where only a fraction of the geodetic convergence (~4 × 10^{19} Nm/year) is released seismically, with the remainder accommodated by aseismic slip in deeper, ductile portions below ~20 km. This deficit underscores the role of transient creep in modulating earthquake cycles. Aftershock sequences provide insights into MHT structure; for instance, the post-2015 Gorkha aftershocks (over 400 events > M 4) illuminated a duplex geometry with ramps and flats, activating mid-crustal segments and revealing how fault bends arrest ruptures. Swarm activity in these sequences often aligns with ramp structures, facilitating stress diffusion without major surface breaks.^[35]^[36]^[37]

Seismic Hazard

Earthquake Potential

The shallow portions of the Main Himalayan Thrust (MHT) exhibit high interseismic coupling ratios, typically ranging from 70% to 90% over widths of about 100 km downdip, resulting in significant elastic strain accumulation that supports the potential for magnitude 8–9 ruptures along segments 300–600 km in length. Geodetic observations from GPS networks reveal that these locked zones, extending from the Himalayan Frontal Thrust northward beneath the Lesser and High Himalaya, experience minimal creep and build moment deficit at rates tied to the 15–21 mm/yr India-Eurasia convergence. This persistent locking, with sharp transitions to deeper aseismic zones, underscores the MHT's capacity to store energy for great earthquakes without frequent partial releases.^[38]^[39]^[40] A prominent feature enhancing this potential is the central seismic gap, spanning approximately 650 km from Kashmir to Bhutan, which has remained unruptured by a major event since the 1505 earthquake (estimated at M >8.5). Paleoseismic trenching and historical records indicate a slip deficit of around 10 m in this gap since 1505, accumulating enough strain to fuel an earthquake exceeding M 8.5, given the ongoing convergence and lack of significant modern seismicity. This gap's locked state exemplifies how extended quiescence amplifies seismic hazard along the MHT.^[41]^[42]^[43] Estimates of the MHT's maximum earthquake magnitude reach up to M 9.0, informed by the fault's total locked length exceeding 2,000 km and the geodetically measured strain deficit, which requires such events to balance long-term slip rates. However, rupture propagation may be limited by structural barriers at the syntaxial terminations, such as the Nanga Parbat region in the western Himalayan syntaxis, where complex geometry and high exhumation rates create along-strike discontinuities that could segment great earthquakes. Historical ruptures, including the 1505 event spanning much of the central gap, demonstrate the thrust's capability for extensive but not always arc-wide failures.^[44]^[45]^[46] Topography further influences the MHT's earthquake potential by elevating deviatoric stresses in high-relief zones of the High Himalaya, where abrupt elevation changes concentrate Coulomb stress and enhance rupture likelihood through intensified north-south compression. In these areas, the range crest acts as a stress guide, correlating with heightened microseismicity and favoring thrust faulting that could propagate upward into larger events. This topographic modulation contributes to spatially variable strain buildup, with greater seismic risk in sectors of pronounced relief.^[40]

Risk Assessment Models

Risk assessment models for the Main Himalayan Thrust (MHT) primarily employ probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA) to quantify potential earthquake impacts in the Himalayan region, particularly in Nepal. PSHA integrates historical seismicity, fault slip rates, and segmentation models to estimate the likelihood of exceeding specific ground motion levels over defined time periods. These models often use logic trees to account for uncertainties in fault segmentation along the MHT, treating it as discrete asperities or a continuous locked zone, with recurrence intervals for great earthquakes (M>8) estimated at 500–1000 years based on paleoseismic and geodetic data. For instance, in central Nepal, PSHA indicates an annual probability of 0.5–1% for an M>8 event, reflecting the seismic gap's maturity since possible ruptures around 1344–1505 CE, with debates on the exact coverage of these events.^[47]^[48]^[49] Ground motion prediction equations (GMPEs) adapted for Himalayan thrust faults form a critical component of these models, capturing region-specific attenuation due to the MHT's shallow dip and thick sedimentary basins. Seminal GMPEs, such as those developed for the northwest Himalaya, predict peak ground accelerations (PGA) that amplify in foreland basins like the Kathmandu Valley, with values reaching up to 0.8 g for 2475-year return periods (2% probability of exceedance in 50 years). These equations incorporate epistemic uncertainties through weighted combinations in logic trees, often drawing from global subduction models adjusted for continental collision dynamics, to better represent near-fault effects and basin amplification.^[50]^[51]^[52] Deterministic scenarios complement PSHA by simulating worst-case ruptures along the MHT, focusing on the central seismic gap in Nepal where a full-length event could reach M 8.4–8.8. These models use finite-fault simulations to forecast ground motions and secondary hazards, such as widespread liquefaction in the Indo-Gangetic plains and Kathmandu Valley due to high water tables and soft sediments, potentially affecting millions in urban centers. For example, a modeled M 8.8 rupture in the central gap predicts PGA exceeding 0.5 g across much of Nepal, with slip deficits of 4–10 m inferred from geodetic locking models.^[53]^[54]^[55] Recent advancements in PSHA for Nepal, incorporating data from the 2015 Gorkha earthquake (Mw 7.8), have refined hazard estimates by updating source models with improved aftershock distributions and InSAR-derived slip patterns. Studies from 2023–2025 highlight elevated hazards in frontal thrust zones, with PGA values for 475-year return periods (10% probability in 50 years) increased by 20–30% in areas like the Sub-Himalaya compared to pre-2015 models, emphasizing the role of partial ruptures in modulating future risks. These updates utilize open-source tools like OpenQuake for consistent comparisons, prioritizing distributed seismicity alongside major faults. A M7.1 normal-faulting earthquake in southern Tibet on January 7, 2025, near the Nepal border, did not directly involve the MHT but underscores ongoing regional seismicity.^[56]^[57]^[52]^[58]

Research and Monitoring

Geodetic and Paleoseismic Studies

Geodetic studies of the Main Himalayan Thrust (MHT) primarily utilize Global Positioning System (GPS) networks to quantify interseismic deformation and convergence rates across the Himalayan arc. Measurements indicate that the convergence between the Indian and Eurasian plates occurs at rates of 15-20 mm/year, with much of this motion absorbed by elastic strain accumulation due to locking along the MHT.^[35]^[59] In central and eastern Nepal, the rate is approximately 17.8 ± 0.5 mm/year, while western Nepal experiences slightly higher rates of 20.5 ± 1 mm/year, highlighting regional variations in plate motion.^[35] Coupling models derived from GPS data between 2015 and 2025 reveal heterogeneous frictional properties along the MHT, with strong coupling extending up to about 100 km downdip from the Main Frontal Thrust in many segments, and variable locking that influences strain distribution.^[60]^[61] These models, often based on Bayesian inversions of velocity fields, demonstrate that the MHT is generally highly coupled along its length, storing elastic strain equivalent to potential magnitude 8+ earthquakes.^[62] Interferometric Synthetic Aperture Radar (InSAR) observations have provided detailed insights into postseismic deformation following the 2015 Mw 7.8 Gorkha earthquake in eastern Nepal. Data from satellites such as Sentinel-1 and ALOS-2 show coseismic uplift of about 1 m in the Kathmandu Basin and subsidence of up to 0.6 m in the higher Himalaya, with early postseismic patterns reversing this motion—uplift in the subsided areas and subsidence in the uplifted basin—indicating afterslip and viscoelastic relaxation on the MHT.^[63]^[64] These observations suggest partial release of accumulated stress in the central segment, with downdip afterslip extending beyond the coseismic rupture patch, contributing to the overall moment budget of the thrust.^[65] Paleoseismic investigations, particularly through trenching across the Main Frontal Thrust, have uncovered evidence of multiple great earthquakes along the MHT over the Holocene. Trenches in regions such as southwestern Bhutan and central Nepal reveal evidence of at least 5 surface-rupturing events over the past ~2,600 years in some segments, with other studies indicating 5-7 events over 3,600-4,500 years, and individual slips per event ranging from 10 to 20 m, consistent with magnitude 8+ ruptures.^[28]^[66] Radiocarbon dating of offset sediments and colluvial wedges in these exposures supports recurrence intervals of several centuries, underscoring the thrust's capacity for large, infrequent earthquakes that propagate to the surface.^[28] Recent studies from 2024 to 2025, focusing on the western Himalaya, have advanced understanding of interseismic strain buildup using integrated GPS and InSAR data. Analyses indicate ongoing strain accumulation at rates supporting a potential major rupture, with studies indicating that some locked segments, such as the central Himalayan seismic gap, have accumulated strain for 500-700 years since the last great earthquake (circa 1505 CE), suggesting they may be primed for a major event based on coupling ratios and historical slip deficits.^[36]^[67] These findings emphasize the role of variable coupling in modulating seismic potential along the arc.^[61]

Seismological Networks

The Nepal Seismological Network, managed by the National Earthquake Monitoring and Research Center under the Department of Mines and Geology, expanded significantly following the 2015 Gorkha earthquake, incorporating over 20 broadband and strong-motion stations by 2016 to improve real-time monitoring of seismicity along the Main Himalayan Thrust.^[68] This network, operational since 1994 with initial sparse coverage, now provides continuous data acquisition across central Nepal, enabling precise detection of moderate earthquakes and aftershocks within the locked zone of the thrust.^[69] In India, the National Centre for Seismology (NCS) operates a nationwide broadband seismic array as part of the National Seismological Network, which includes over 150 stations strategically placed to capture Himalayan tectonics, with dense deployments along the northwestern and central segments of the Main Himalayan Thrust.^[70] These stations, equipped with broadband seismometers, record teleseismic and regional events, contributing to hypocenter relocations that refine fault imaging in the underthrust Indian plate.^[71] Bhutan enhanced its seismic infrastructure post the 2011 Mw 6.9 earthquake, installing a national monitoring network with initial temporary arrays in 2013–2014, followed by permanent stations integrated into a system comprising approximately 13 seismic stations as of 2024.^[72]^[73] This setup, coordinated by the Department of Geology and Mines, focuses on the eastern Himalayan arc, detecting low-magnitude events that reveal segmentation along the thrust.^[74] Data from these networks are integrated via real-time telemetry systems, supporting earthquake early warning initiatives in the Himalayan region, such as the Uttarakhand State system, which processes P-wave arrivals to issue alerts seconds before destructive shaking.^[75] By 2025, upgrades incorporating artificial intelligence, including deep learning models like Earthquake Transformer (EQT) for phase picking and event detection, have improved automated processing in Bhutan and adjacent areas, reducing detection thresholds for microseismicity.^[76] International research programs, such as the Hi-CLIMB project, deployed a broadband seismic array across the Himalaya from 2001–2005, yielding high-resolution profiles of the Main Himalayan Thrust and influencing ongoing coupling studies through data sharing.^[77] Complementary paleoseismic campaigns target seismic gaps along the thrust, with trenching efforts in southwestern Bhutan revealing a 2600-year record of surface-rupturing events, informing recurrence intervals for hazard mapping.^[28] Advances in dense arrays, particularly in the Kashmir region from 2015 onward, have enabled detection of microseismicity (magnitudes <2.0) associated with the northwestern Himalayan thrust, achieving hypocenter accuracy below 5 km through multi-station relocations.^[78] These deployments address challenges like sparse coverage in rugged terrain, enhancing resolution of shallow fault structures while integrating with broader seismicity patterns observed regionally.^[79]

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[27]
A 2600-year-long paleoseismic record for the Himalayan Main ... - SE
Dec 8, 2020 · In this paper, we present geomorphologic and paleoseismic studies conducted over a large river-cut exposure along the Main Fontal Thrust in southwestern Bhutan.
[28]
[PDF] Estimating the return times of great Himalayan earthquakes in ...
The uplift rate (8.5 ± 1.5 mm/yr), thrust dip. (25° ± 5°N), and apparent characteristic behavior imply 12–17.5 m of slip per event. On the Bardibas thrust,.
[29]
New Constraints on the Mechanism and Rupture Area for the 1905
Sep 27, 2017 · The 1905 M w 7.8 Kangra earthquake is one of several major earthquakes in the past two centuries to have incompletely ruptured the Main Himalayan thrust.
[30]
The 29 July 1947 Mw ¼ 7.9 earthquake (Chen and Molnar, 1977
8 Gorkha earthquake nucleated at the downdip edge of the Main Himalayan Thrust (MHT) near the transition from interseismic locking to aseismic creep beneath the ...
[31]
The 2015 Gorkha earthquake: A large event illuminating the Main ...
Mar 7, 2016 · 2 Depth and Geometry of the Main Himalayan Thrust. As discussed above, the centroid depths of the 2015 Gorkha earthquake sequence are uncertain.
[32]
Seismogenic Potential of the Main Himalayan Thrust Constrained by ...
Jun 19, 2021 · The subscripts VS and VW stand for Velocity Strengthening and Weakening, respectively describing the frictional behavior of the barrier and ...
[33]
Convergence rate across the Nepal Himalaya and interseismic ...
Apr 13, 2012 · The moment deficit due to locking of the MHT in the interseismic period accrues at a rate of 6.6 ± 0.4 × 1019 Nm/yr on the MHT underneath Nepal.
[34]
Interseismic strain rate and fault coupling along the central ...
Jun 25, 2025 · The Himalayan seismicity is mostly concentrated at shallow depths (<30 km), while the deeper earthquakes (<80 km) are limited only to the ...
[35]
Duplex in the Main Himalayan Thrust illuminated by aftershocks of ...
Nov 11, 2019 · In April 2015, the lower locked portion of the Main Himalayan Thrust ruptured beneath Nepal, causing the disastrous Mw 7.8 Gorkha earthquake ...
[36]
[PDF] Interseismic coupling on the main Himalayan thrust - CalTech GPS
Jul 29, 2015 · We consider the total length of the arc, roughly 2000 km, from 73∘E to 96∘E. Due to the arcuate shape, we simplify the fault geometry ...
[37]
[PDF] Convergence rate across the Nepal Himalaya and interseismic ...
Apr 13, 2012 · Convergence rate across the Nepal Himalaya and interseismic coupling on the Main Himalayan Thrust: Implications for seismic hazard. Thomas ...
[38]
[PDF] Stress buildup in the Himalaya - Tectonics Observatory
Nov 20, 2004 · To test the topographic control on seismicity we have computed Coulomb stress variations due to interseismic strain that account for topographic.Missing: elevated likelihood
[39]
[PDF] Structural interpretation of the great earthquakes of the last ...
Even in the central seismic gap of the Himalaya, where the present-day slip deficit has reached ~10 m since 1505, the slip deficit over the last millennium is ...
[40]
Earthquake rupture variability along the central seismic gap ...
Jul 1, 2025 · This study aims to improve the understanding of rupture extents and behavior along the ~ 650 km Central Seismic Gap (CSG) segment by analyzing paleoseismic ...
[41]
Earthquakes in India - University of Colorado Boulder
Seismic gaps along two-thirds of the Himalaya that have developed in the past five centuries, when combined with geodetic convergence rates of approximately 1.8 ...
[42]
[PDF] 9.0 earthquakes required by geodetic strain in the Himalaya
Feb 13, 2016 · Mw >8.0, Mw > 8.5, and Mw >9.0 ... Stevens, V. L., and J. P. Avouac (2015), Interseismic coupling on the main Himalayan thrust, Geophys.
[43]
Can an earthquake of Mw 9 occur in the Himalayan region?
Aug 5, 2025 · The earthquakes in central Himalaya are inferred as occurring over the plate boundary fault, the Main Himalayan Thrust. The wedge thrust ...
[44]
Future Mw>8 earthquakes in the Himalaya: implications from the 26 ...
Dec 26, 2004 · Potentially the most dangerous of these is the so-called Central Himalayan Gap whose rupture in 1505 may have occurred as a 600-km-long rupture, ...
[45]
Probabilistic seismic hazard assessment of Nepal using multiple ...
This study uses three source models, ground motion equations, and long-term slip rates to assess seismic hazard in Nepal, finding high potential in the Lesser ...
[46]
Probabilistic Seismic Hazard Assessment of Nepal - GeoScienceWorld
Sep 11, 2018 · We carry out a new probabilistic seismic hazard analysis (PSHA) for Nepal. The 2015 M w 7.8 Gorkha, Nepal, earthquake (hereafter the Gorkha ...
[47]
[PDF] Probabilities of occurrence of great earthquakes in the Himalaya
The 100-year probability of such an earthquake occurring in the Kashmir seismic gap is about 0.27, in the central seismic gap about 0.52 and in the Assam gap ...
[48]
Ground motion prediction equation for NW Himalaya and its ...
An attenuation relationship, also known as a Ground Motion Prediction Equation (GMPE), has been developed for the Northwest Himalaya and its surrounding region.
[49]
Probabilistic seismic hazard assessment of Nepal using multiple ...
Aug 16, 2018 · The region of the Lesser Himalaya is found to have high seismic hazard potential. Along the Main Himalayan Thrust from east to west beneath the ...
[50]
State-of-the-art review of probabilistic seismic hazard analysis in ...
Apr 15, 2025 · This study systematically analyzes and compares multiple PSHA studies that have estimated seismic hazard either for the entire country or for specific urban ...
[51]
[PDF] Deterministic seismic hazard analysis of north and central ...
A comprehensive deterministic seismic hazard assessment (DSHA) of the north and central Himalayas. (NCH) is attempted in the current study using recently ...
[52]
Himalayan Seismic gaps
Geodetic measurements indicate that if an earthquake happened today in the Central Gap (western Nepal) it must slip by more than 4 m, and probably by more than ...
[53]
Scenario ensemble modelling of possible future earthquake impacts ...
Jun 30, 2020 · Known and inferred earthquakes with estimated magnitudes on the Main Himalayan Thrust (MHT) and surrounding faults in the last 1000 years ...
[54]
New Probabilistic Seismic Hazard Model for Nepal Himalayas by ...
The Himalayan chain in Nepal is characterized by a complex fault system of predominantly ~1000 km long sub-parallel major thrusts from the south to the north: ...2. Geodynamics And... · 3. Seismicity Database · 4. Seismic Source...<|control11|><|separator|>
[55]
Probabilistic seismic hazard analysis of Nepal considering validated ...
Jul 19, 2024 · This study aims to validate the best seismic source model to perform PSHA in Nepal. Earthquake data from earthquake catalogues for the period of 1900 to 2022 ...
[56]
GPS measurements of present-day convergence across the Nepal ...
Mar 6, 1997 · Here we report geodetic measurements, using the Global Positioning System (GPS), of the rate of contraction across the Himalaya, which we find to be 17.52 ± 2 ...
[57]
Geodetic plate coupling and seismic potential on the main ...
May 8, 2024 · It is characterized by down-dip variation of the dip-angle ... Segmentation of the main Himalayan thrust illuminated by Bayesian inference of ...
[58]
Overriding Plate Deformation Controls Inferences of Interseismic ...
Sep 21, 2024 · Global Navigation Satellite System data suggest the Main Himalayan Thrust is highly coupled along its entire length Previously inferred low ...
[59]
Segmentation of the Main Himalayan Thrust Illuminated by Bayesian ...
Our probabilistic estimate of interseismic coupling highlights four large, highly coupled patches separated by three potential barriers of low coupling. Locked ...
[60]
Coseismic and early postseismic deformation due to the 25 April ...
Mar 18, 2016 · The pattern of early postseismic surface uplift and subsidence is found to be opposite to that of the coseismic motion. InSAR and GPS data were ...3 Slip Models · 3.1 Coseismic Slip Model · 4.2 Coseismic And...
[61]
Subsidence in the Kathmandu Basin, before and after the 2015 Mw ...
Based on geodetic measurements, the Gorkha earthquake caused about 1 m uplift in the Kathmandu Basin and 0.6 m subsidence in the higher Himalaya (Elliott et al.Sbas-Dinsar Processing · Sbas-Dinsar Time Series · Subsidence Related To...
[62]
InSAR Constrained Downdip and Updip Afterslip Following the 2015 ...
We use ALOS-2 and Sentinel-1 data spanning 2015–2020 to obtain the post-seismic deformation of the 2015 Mw 7.8 Nepal earthquake.
[63]
Estimating the return times of great Himalayan earthquakes in ...
Aug 7, 2014 · We present here a refined, longer slip history of the MFT's two overlapping strands (Patu and Bardibas Thrusts) in that region, based on updated ...
[64]
Geodetic Insights to the Himalayan Megathrust Kinematics Unravel ...
Oct 22, 2025 · Recent ... Convergence rate across the Nepal Himalaya and interseismic coupling on the main Himalayan thrust: Implications for seismic hazard.
[65]
Source modeling of the 2015 Mw 7.8 Nepal (Gorkha) earthquake ...
Sep 13, 2017 · Hypocenters of 360 earthquakes were classified as quality C from 25 April to 07 June 2016 and were relocated with only Nepal DMG NSN station ...
[66]
[PDF] Seismically active structures of the Main Himalayan Thrust ... - HAL
Oct 14, 2022 · Seismicity in far western Nepal reveals flats and ramps along the Main Himalayan Thrust, Geophys. J. Int., 226(3), 1747–. 1763. Lay, T., Ye ...
[67]
[PDF] Earthquake monitoring over Indian domain
National Centre for Seismology (NCM) under. Ministry of Earth Sciences (MoES) has 152 stations of National Seismological Network spread all over the country ...
[68]
[PDF] Source characteristics of the NW Himalaya and its adjoining region
Jul 3, 2019 · The Main. Frontal thrust (MFT) separates the Sub Himalaya from the Indo-Genetic. Plains. Its surface manifestations are visible at a few places ...
[69]
(PDF) Seismotectonics of Bhutan: Evidence for segmentation of the ...
To understand this low activity and its impact on the seismic hazard, a seismic network was installed in Bhutan for 22 months between 2013 and 2014. Recorded ...
[70]
[PDF] Bhutan - JICA
Aug 2, 2017 · • National seismic monitoring network in Bhutan. •. - Micro earthquake monitoring. - Seismic intensity & strong motion monitoring. Data ...Missing: post- | Show results with:post-
[71]
Uttarakhand State Earthquake Early Warning System: A Case Study ...
May 21, 2024 · The EEW system is a live earthquake monitoring system capable of detecting the onset of an earthquake, estimating its probable magnitude, and ...Missing: telemetry | Show results with:telemetry
[72]
Comprehensive Analysis of Local Earthquakes in the Eastern ...
Mar 10, 2025 · The primary objective of this study is to enhance earthquake detection and gain new insights into fault activity in Bhutan by reprocessing data ...Missing: post- | Show results with:post-
[73]
Project Hi-CLIMB: A Synoptic View of the Himalayan Collision Zone ...
Project Hi-CLIMB is a broadband seismic experiment whose goal is to produce a high-resolution continuous profile across the Himalaya and southern Tibet.Missing: GNSS coupling mapping
[74]
(PDF) Crustal Structure and Quantified Earthquake Hazard in the ...
... Indian National Centre for Seismology. The region studied lies between the Main Boundary Thrust and the Zanskar thrust bordering on the Tethys Himalaya ...
[75]
Stochastic Simulation of Strong Ground Motions From Two M > 5 ...
Nov 22, 2021 · These earthquakes were well recorded at five stations, namely, Almorah (ALM), Haridwar (HDR), Rudraprayag (RPG), Thakurdwar (TDR), and Tarikhet ...