Frontal Thrust Fault Research Articles

Late Medieval seismicity on the Himalayan Frontal Thrust Fault at Lal Dhang, Uttarakhand, India

The Himalayan Frontal Thrust Fault (HFT) lies at the active tectonic boundary between Eurasia and the Indian subcontinent. Past earthquakes on the HFT have resulted in significant ground displacement that is evidenced by sizable scarps along the fault. Here we present findings from an ~28-m-long x 5-m-wide x 8-m-deep paleoseismic trench excavated across an ~10-m-high fault scarp at the site of Lal Dhang in the Central Seismic Gap. Excavation exposed three recumbent fault-propagation folds that support occurrence of at least two earthquakes with >25 m of cumulative coseismic slip. Findings suggest that two great (Mw ≥ 8.0) earthquakes may have occurred in rapid succession at the site during the Late Medieval period. Radiocarbon dating of stratigraphic units that are modeled using the OxCal software program constrain timing of the events to 1317–1391 CE and 1447–1572 CE, which is coincident with historical earthquakes in 1344 CE and 1505 CE. With over 500 years of quiescence since the last great earthquake in the Central Seismic Gap, it is possible that another devastating rupture could be imminent.

Damage stratigraphy as a controlling mechanism of earthquakes distribution and fault patterns

Decollement zones are sub-horizontal weak zones in the earth's crust that strongly affect tectonic deformation. The weakness of a decollement zone is commonly attributed to thermal and composition layering that is relatively static in time. Here, we present evidence for damage stratigraphy in which a stratigraphic unit evolves dynamically into a weak decollement zone. The analysis is focused on the internal structure of a deep, tectonically active, decollement zone in the Sichuan Basin, China. The analyzed zone is about a 1 km thick sequence of Triassic rocks that extends across most of the Sichuan Basin at a depth range of 5.8–6.8 km. This sequence is composed of evaporites (mostly anhydrite) and carbonates (dolomite and limestone). We used three-dimensional seismic surveys, borehole observations, and rock-mechanics experiments to document pervasive internal damage revealed by fractures and flow features within this unit. As this damaged unit is defined by its stratigraphic position, we term it a Damaged Stratigraphic Unit (DSU). The damage-induced weakness of the DSU controls two active tectonic features in the western Sichuan Basin. First, large, intra-basin, frontal thrust faults terminate against the DSU from above and from below. Second, regional earthquakes display a profound decrease in frequency and seismic moment at the depth interval of 5.8–6.8 km that coincides with the DSU. We argue that this earthquake distribution may pose an increased geohazard to the Chengdu area by shallow, moderate earthquakes.

The Pamir Frontal Thrust Fault: Holocene Full‐Segment Ruptures and Implications for Complex Segment Interactions in a Continental Collision Zone

AbstractThe Pamir Frontal Thrust (PFT) of the Trans‐Alai Range in Central Asia is the principal active fault of the intracontinental convergence zone between the Pamir and Tien Shan. Its northward propagation is reflected by frequent seismic activity and ongoing crustal shortening. Recent and historic earthquakes exhibit complex rupture patterns within and across seismotectonic segments bounding the Trans Alai, challenging our understanding of fault interaction and seismogenic potential. We provide paleoseismic data from five trenches along the central PFT segment (cPFT) and interpret five and possibly six paleoearthquakes that have ruptured since ∼7 ka and 16 ka, respectively. Our results indicate that at least three major earthquakes ruptured the full‐segment length and possibly crossed segment boundaries with a recurrence interval of ∼1.9 kyr and potential magnitudes of up to Mw 7.4. We did not find evidence for great (i.e., Mw ≥8) earthquakes. However, discrepancies between slip and rupture extent during apparent partial segment ruptures in the western half of the cPFT, combined with significantly higher scarp offsets, indicate a more mature fault section with potential for future fault linkage. We estimate an average rate of horizontal motion for the cPFT of 4.1 ± 1.5 mm/yr during the past ∼5 kyr, which does not fully match the GNSS‐derived present‐day shortening rate of ∼10 mm/yr. This suggests a complex distribution of strain accumulation and potential slip partitioning between the cPFT and additional faults and folds within the Pamir that may be associated with a partially locked regional décollement.

Assessment of the tectonically induced Quaternary landforms and active deformation in the area between Main Boundary Thrust and Himalayan Frontal Thrust, south of the Siang Antiform, Arunachal Himalaya, India

The present study area represents one of the active segments of the frontal part of the Arunachal Himalaya. The major structural boundaries traversing the area are the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT) and other local faults are tectonically active, as evident from the landforms that evolved in the fault zones. Strath terraces and uplift fluvial terraces are observed in the hanging‐wall block of the HFT and MBT, and along the HFT straight to curvilinear mountain fronts are observed. Normal faults both transverse and parallel to the strike of HFT are observed in the hanging‐wall block of the HFT. West of Pasighat the sub‐Himalaya terrain resembles a duplex, where there is gradual rise in elevation from the Brahmaputra Plain to the low‐lying hills of the sub‐Himalayan and sudden rise in elevation across the MBT. Drainage aligning to the bedrock structures and stream migrations are observed in the fault zones. Along the MBT, the sub‐Himalayan rocks are thrusted over either by quartzite or black carbonaceous shales, in some sections the MBT is behaving as a back‐thrust that dips towards the south. The MBT has also been displaced by almost N–S‐trending transverse faults where highly sheared bedrocks are also observed. Tilting of Quaternary fluvial deposits are observed in the hanging‐wall blocks of intraformational thrusts at two locations. Signatures of paleoseismic activities in the form of various soft‐sediment deformational structures are observed in Quaternary deposits in the HFT zone and also in the hanging‐wall block of the MBT. To determine the deformation and strain rate accumulation, we have re‐analysed the available GNSS results of the area, which indicate a deformation rate of up to 16 mm/year in the vicinity of the Pasighat region. The GPS‐derived deformation rates are well corroborated with the existing results of peak ground acceleration (PGA) anomalies. The component–wise motion indicates higher fault perpendicular motion in this part, which reveals an accumulation of more strain along the major Himalayan faults.

Native H2 Exploration in the Western Pyrenean Foothills

AbstractNative hydrogen (H2) may represent a new carbon free‐energy resource, but to date there is no specific exploration guide to target H2‐fertile geological settings. Here, we present the first soil gas survey specifically designed to explore H2 migration in a region where no surface seepage has been documented so far. We choose the Pyrenean orogenic belt and its northern foreland basin (Aquitaine, France) as a test site for our strategy. The presence of mantle rocks at shallow depth (<10 km depth) under the Mauléon Basin connected to the surface by major faults is considered as preliminary requisites for H2 generation and drainage. On this basis, more than 1,100 in situ soil gas analysis (H2, CO, CO2, CH4, H2S, and 222Rn) were performed at ∼1 m depth at the regional scale along a 10 × 10 km grid spanning over 7,500 km2. The analysis campaign reveals several areas of high occurrence to the north of the Mauléon Basin where H2, CO2, and 222Rn concentrations exceed 1,000 ppmv, 10 vol%, and 50 kBq m−3, respectively. Most of these hot spots are located along the North Pyrenean Frontal Thrust and other related faults rooted in the mantle body. These results, together with evidence from the literature of fluid migration at depth, suggest that H2 may be sourced from mantle rocks serpentinization and carried to the surface along major thrusting faults. Traps containing hydrogen remain unidentified up to now but the presence of salt‐related structures (diapirs) near these hot spots is considered encouraging.

Active tectonics, landscape evolution and sediment dynamics in Dehra Dun, Northwest Himalaya inferred from geomorphic indices and GIS tools

Geomorphic evolution of the frontal parts of active mountain belts is strongly influenced by tectonic processes, usually manifested in fluvial, structural and morphotectonic parameters of the landscape. Geomorphic indices have long been used for understanding the tectonic imprints in river basins. However, their applicability and validation from field observations in the Himalayan basins have often been debated. Here we test the applicability of several geomorphic indices in the western Dehra Dun (intermontane valley) that includes well-known tectonic elements such as Main Boundary thrust (MBT), Main Frontal Thrust (MFT), Santaurgarh Thrust (ST), and other smaller faults. Based on the spatial distribution of the values of different geomorphic indices, we map four different tectonic zones to represent the relative tectonic activity from low to very high. We conclude from morphometric analysis that the MBT and the ST are active faults. However, we do not find any geomorphic evidence of recent activity along several other faults mapped in this region or any deformation in the major fan units. We argue that active tectonics has not played a significant role in shaping the landforms in this region except for providing accommodation space and sediment supply for the deposition of fan units. We have further employed DEM and limited borehole data to understand the sediment storage and excavation at Late Late Quaternary time scale. We compute the average stored volume of sediments since ~50 ka as 8.03 × 1010 m3 (using borehole data) and 12.24 × 1010 m3 (GIS approach). Total eroded volume has been computed as 0.47 × 1010 m3 (using borehole data) and 0.64 × 1010 m3 (GIS approach). These volumes give a time-averaged sediment discharge leaving the dun as 0.21–0.39 × 106 m3/yr over Late Quaternary period. We note that the estimated average eroded material during the incision phase is only 5–6% of the total accumulated sediment volume. Further, the average estimated volume (8.03–12.24 × 1010 m3) in the valley is nearly half of the volume of the sediment that can be accommodated (27.2 × 1010 m3) in the valley. Also, the present-day sediment supply to the Dun (~0.14 × 106 m3/yr) is low in comparison to estimated average erosion rate. Our results therefore suggest that the valley is only half filled, and is in excavation phase since Late Quaternary mostly driven by climatic perturbations.

Multiphase, decoupled faulting in the southern German Molasse Basin – evidence from 3-D seismic data

Abstract. We use three-dimensional seismic reflection data from the southern German Molasse Basin to investigate the structural style and evolution of a geometrically decoupled fault network in close proximity to the Alpine deformation front. We recognise two fault arrays that are vertically separated by a clay-rich layer – lower normal faults and upper normal and reverse faults. A frontal thrust fault partially overprints the upper fault array. Analysis of seismic stratigraphy, syn-kinematic strata, throw distribution, and spatial relationships between faults suggest a multiphase fault evolution: (1) initiation of the lower normal faults in the Upper Jurassic carbonate platform during the early Oligocene, (2) development of the upper normal faults in the Cenozoic sediments during the late Oligocene, and (3) reverse reactivation of the upper normal faults and thrusting during the mid-Miocene. These distinct phases document the evolution of the stress field as the Alpine orogen propagated across the foreland. We postulate that interplay between the horizontal compression and vertical stresses due to the syn-sedimentary loading resulted in the intermittent normal faulting. The vertical stress gradients within the flexed foredeep defined the independent development of the upper faults above the lower faults, whereas mechanical behaviour of the clay-rich layer precluded the subsequent linkage of the fault arrays. The thrust fault must have been facilitated by the reverse reactivation of the upper normal faults, as its maximum displacement and extent correlate with the occurrence of these faults. We conclude that the evolving tectonic stresses were the primary mechanism of fault activation, whereas the mechanical stratigraphy and pre-existing structures locally governed the structural style.

Active Tectonics of the Frontal Himalayas: An Example from the Manzai Ranges in the Recess Setting, Western Pakistan

The Himalayan main frontal thrust (MFT) accommodates most of the present-day Indo–Asia convergence with related periodic earthquakes. The seismicity and deformation mechanism varies considerably across the frontal Himalayas. We mapped a segment (Manzai Ranges) of the MFT at the western margin of the Himalayas and analyzed its deformation mechanism and active tectonics using geomorphic indices and the Interferometric Synthetic Aperture Radar (InSAR) Small Baseline Subset (SBAS) technique. Two frontal thrust faults (Khirgi and Jandola) were mapped using Sentinel-2B band ratios in the study area. Water gaps were present in the form of deflected streams at the tip of the growing anticlines. The C-band RADAR interferometry (Sentinel-1A) showed an average uplift of 5–9 mm/year in the satellite line of sight (LOS) from May 2018 to October 2019. The velocity profiles show an uplift variation across the anticlines and may be related to the displacement transfer from the zone of compression in the Manzai Ranges to the zone of transpression in the Pezu–Bhittani Ranges. Four types of morphometric analyses were carried out to assess the relative tectonic activity, namely mountain front sinuosity index (Smf), valley floor width to height ratio (Vf), normalized longitudinal river profile, and normalized channel steepness index (Ksn). The landscape response to active tectonics in the study area was recorded as a deep fluvial incision in V-shaped valleys, convex river profiles, topographic breaks as knickpoints, and a high Ksn index. The geomorphic parameters show a relative increase in tectonic uplift and deformation from the Kundi anticline to the Khirgi and Manzai anticline. We concluded that the frontal structures in the western Himalayas are still going through an active phase of deformation and landscape development with both seismic and aseismic creep.

Afterslip evolution on the crustal ramp of the Main Himalayan Thrust fault following the 2015 Mw 7.8 Gorkha (Nepal) earthquake

Current afterslip models of the Mw 7.8 Gorkha earthquake contradict with the depth ranges of relocated aftershock distribution and inter-seismic locked-creeping transition zone. We use both GPS and interferometric synthetic aperture radar (InSAR) data to image the afterslip evolution in the first 189 post-seismic days, i.e., from 25 April to 1 November 2015. In the study region, 51 GPS stations are divided into three categories based on their observation time: (1) 25 stations with both pre- and post-seismic observations, (2) 16 stations with only post-seismic observations, and (3) 10 stations with only pre-seismic observations. The secular tectonic motion and seasonal variations are corrected carefully and directly using the fitted functions from the pre-seismic position time series. During the inversions, we adopt the widely accepted flat–ramp–flat geometrical model of the Main Frontal Thrust fault (MFT)–Main Himalayan Thrust fault (MHT). The preferred weight ratios between GPS and InSAR observations are elaborately determined through comprehensive analysis of model resolution and fitting residuals. In contrast to previous afterslip models, our preferred afterslip distributes on the crustal ramp of the MHT from depths of 11 to 29 km, which is verified by further inversions using only GPS data and checkerboard resolution tests. The seismic moment released by the afterslip in the first six months is 3.42 × 1019 N m, only approximately 4% of the mainshock moment. The rupture gap between the mainshock and the 12 May aftershock is filled up with post-seismic aseismic slip.

Detecting rock uplift across southern Taiwan mountain belt by integrated GPS and leveling data

Rock uplift on the Earth surface is a key observation for studies of tectonics and geodynamic processes. Geodetic measurements from Global Positioning System (GPS) and leveling are able to track vertical deformation over a wide range of spatial and temporal scale. Taiwan mountain belt is subject to a rapid uplift rate of 20 mm/yr as revealed by GPS and leveling measurements in previous studies. The extremely high rates motivate us to analyze a set of newly processed GPS and leveling data along a NW-SE transect across southern Taiwan by considering the effects of the earthquake-related deformation as well as hydrological and surface processes. Our estimates of rock uplift rates from GPS and leveling are from −12 to +14 mm/yr across the southern Central Range of Taiwan. Vertical velocity changes on the small spatial scale are primary related to fault locking in the seismic cycle. The large spatial feature showing the mean uplift rate of 6 mm/yr between the eastern Central Range and the frontal thrust faults can be explained by a large-scale pop-up structure assuming the depth of 15–20 km in the orogenic wedge and the horizontal shortening of 30 mm/yr. Our results draw attention to carefully study geodetic vertical deformation in the mountain belts and seek relevant causes.

Source model and Coulomb stress change of the 2015 Mw 7.8 Gorkha earthquake determined from improved inversion of geodetic surface deformation observations

The 2015 Mw 7.8 Gorkha, Nepal, earthquake produced a $$\sim $$ 140 km rupture on the Main Himalaya Thrust (MHT) fault at the convergence zone of the Indian and Eurasian plates. The coseismic surface deformation, fault slip model and induced stress change are comprehensively investigated with the geodetic observations in this study. The surface deformation is mapped by the combination of the GPS observations with the descending and ascending track ALOS-2/PALSAR-2 SAR images. An improved forward modeling of the surface displacement considering the effect of topographic variation on the geodetic data inversion is developed, and applied to determine the fault geometry and slip distribution associated with the event. The derived faulting model shows that the thrusting motion occurs on a fault plane with a low dip of $$\sim \,6.2^{\circ }$$ , and the significant slip concentrates at depths of 5–13 km. More than 90% of the seismic moment is released on the middle fault segment with a maximum slip of $$\sim $$ 6.7 m. Two significant slip deficit zones located on the northwest and southeast of the fault are recognized from the source model. The shallow portion of the Main Frontal Thrust fault with little slip during the event is considered as the lower edge of the locked zone, which plays an important role in accommodating the convergence between the Eurasia and India plates. The change in Coulomb failure stress shows a significant increase for the slip deficits and the locked zone on the Himalayan front, which indicates that the accumulated strain on the MHT fault has been partially alleviated by the major quake and the aftershock sequence, but will continue to balance the slip deficit and high stress regimes, and drive the seismicity in the Himalayan front.

Conceptual model of regional groundwater flow based on hydrogeochemistry (Montérégie Est, Québec, Canada)

The groundwater geochemistry of the fractured rock aquifer system in the Montérégie Est region, southern Quebec, Canada, was studied as part of a regional groundwater resources assessment. The 9218 km² study area included three major watersheds that were divided into five hydrogeological contexts: Northern St. Lawrence Lowlands, Southern St. Lawrence Lowlands, Appalachian Uplands, Appalachian Piedmont and Monteregian Hills. A large part of this study area was invaded by the Champlain Sea from 13,000 to 11,000 years ago. Study objectives were to identify the mechanisms controlling groundwater composition and to support the understanding of the aquifer hydrodynamics. Groundwater from 206 wells drilled into the rock aquifer was sampled and analyzed for conventional parameters and isotopic analyses were also done on selected samples (δ2H, δ18O and 3H of water; δ13C and 14C of dissolved inorganic carbon). The interpretation of geochemical results was based on a multivariate statistical analysis, which led to the definition of eight water groups. The study allowed the delineation of a 2200-km² zone containing brackish groundwater of marine origin in the northwestern part of the study area. This zone is surrounded by sodic and alkaline groundwater originating from Na+-Ca2+ ionic exchange. Young groundwater and therefore recharge zones were only encountered in the southern part of the Lowlands, in the northern part of the Piedmont and in the Appalachian Uplands. In the southern part of Lowlands, recharge is presumed to be slow and water composition shows the influence of the former presence of the Champlain Sea. Relatively deep groundwater circulation was also inferred to occur from the Appalachian Uplands toward mixing zones mainly located to the west at the Appalachian frontal thrust faults and around the Monteregian Hills. The geochemical interpretation provided indications on regional recharge and discharge zones as well as groundwater flow, which could not have been determined otherwise.

The Story of a Yakima Fold and How It Informs Late Neogene and Quaternary Backarc Deformation in the Cascadia Subduction Zone, Manastash Anticline, Washington, USA

AbstractThe Yakima folds of central Washington, USA, are prominent anticlines that are the primary tectonic features of the backarc of the northern Cascadia subduction zone. What accounts for their topographic expression and how much strain do they accommodate and over what time period? We investigate Manastash anticline, a north vergent fault propagation fold typical of structures in the fold province. From retrodeformation of line‐ and area‐balanced cross sections, the crust has horizontally shortened by 11% (0.8–0.9 km). The fold, and by inference all other folds in the fold province, formed no earlier than 15.6 Ma as they developed on a landscape that was reset to negligible relief following voluminous outpouring of Grande Ronde Basalt. Deformation is accommodated on two fault sets including west‐northwest striking frontal thrust faults and shorter north to northeast striking faults. The frontal thrust fault system is active with late Quaternary scarps at the base of the range front. The fault‐cored Manastash anticline terminates to the east at the Naneum anticline and fault; activity on the north trending Naneum structures predates emplacement of the Grande Ronde Basalt. The west trending Yakima folds and west striking thrust faults, the shorter north to northeast striking faults, and the Naneum fault together constitute the tectonic structures that accommodate deformation in the low strain rate environment in the backarc of the Cascadia Subduction Zone.

Fracture Alignments in Marine Sediments Off Vancouver Island fromPsSplitting Analysis

Alignments of fractures and cracks in marine sediments may be controlled by various mechanisms such as horizontal compaction and extension and basement faulting. The orientation of these alignments can be estimated through analyses of S‐wave splitting. If sensors in ocean‐bottom observations are deployed through free fall, sensor orientation needs to be determined in order for the recorded data to be used for such analyses. Here, we estimate the sensor orientation from the linear particle motions of P‐to‐s (Ps) phases converted at the sediment–basement interface and also from T waves that are excited by earthquakes and propagate in the seawater. We examine waveforms of local earthquakes recorded by 32 ocean‐bottom seismometers (OBSs) that were deployed through free fall for three months in 2010 off Vancouver Island where the strike‐slip Nootka fault zone (NFZ) intersects the deformation front of the Cascadia subduction zone. Because the particle motion of the Ps wave was corrected by estimating splitting parameters, the fast polarization direction, which reflects S‐wave anisotropic structure within the sediment, can also be evaluated. Consequently, we could estimate the fast polarization direction at OBSs deployed near the NFZ and west of the deformation front. The obtained fast directions appeared to correspond to alignments of shear fractures in the marine sediments associated with the left‐lateral motion of the fault in the basement along the NFZ, margin‐normal cracks due to horizontal compression west of and slightly away from the deformation front, and frontal thrust faults within the accretionary prism near the deformation front.

Study of seismicity in the NW Himalaya and adjoining regions using IMS network

The Reviewed Event Bulletin (REB) of the International Data Center (IDC) has been used in order to investigate the seismicity of the Northwest Himalaya and its neighboring region for the time period June 1999 to March 2015 within the geographical coordinates 25–40° N latitude and 65–85° E longitude. We have used a very precisely located earthquake dataset recorded by the International Monitoring System (IMS) Network containing 7,583 events with body wave magnitudes from 2.5 to 6.3. The study area has been subdivided into six regions based on the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme, which was used as the region classifications of the International Data Center catalog. The examined region includes NW India, Pakistan, Nepal, Xizang, Kashmir, and Hindukush. For each region, Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters (a and b values) have been estimated. The Gutenberg-Richter analysis is preceded by an overview of the seismotectonics of the study area. The obtained Mc values vary from 3.5 to 3.9. The lower value of Mc was found mainly in Xizang region whereas the higher Mc threshold is evident in Pakistan region. However, the b values vary from 1.19 to 1.48. The lowest b value is recorded in Xizang region, which is mostly related to the Main Karakoram Thrust (MKT) fault, whereas the highest b values are recorded in NW India and Kashmir regions, which are mostly related to the Main Frontal Thrust (MFT) fault. The REB for the selected period has been compared to the most renowned bulletin of global seismicity, namely that issued by the National Earthquake Information Center (NEIC) of the United States Geological Survey (USGS). A study of 4,821 events recorded by USGS in the study region indicates that about 36 % of seismic events were missed and the catalog is considered as complete for events with magnitudes ≥4.0. However, both a and b values are obviously higher than those of IMS catalog. The a and b parameters in the Gutenberg-Richter magnitude–frequency relationship have been utilized to forecast the probability of future earthquakes of different magnitudes and returned periods (recurrence intervals).

Increasing seismicity in Southern Tibet following the 2015 Mw 7.8 Gorkha, Nepal earthquake

We conducted a systematic detection of micro-seismicity in Southern Tibet 1.6days before and 4.4days after the 2015 Mw7.8 Gorkha, Nepal earthquake. Our study employs 368 template events listed in the China Earthquake Networks Center (CENC) catalog. With the waveform-based matched filter technique, we detected five times more earthquakes than listed in the CENC catalog during our study period. The seismicity in Southern Tibet shows a significant increase immediately following the Gorkha, Nepal earthquake, including two normal-faulting events (the Mw5.8 Tingri and Mw5.3 Nyalam earthquakes) about 3 and 11h after the mainshock, respectively. Although the static stress changes ΔCFS showed a slightly better correlation with the seismicity rate changes than the peak dynamic stress changes ΔCFS(t), the absolute value of the static stress change at the epicenter region of the Mw5.8 Tingri earthquake is ~10kPa, roughly two orders smaller than the peak dynamic stress change of 2.2MPa. Although we are unable to identify the primary triggering mechanism, it is evident that the 2015 Nepal earthquake triggered widespread seismicity in Southern Tibet. Our results highlight the potential increase of seismic hazard in Southern Tibet due to the occurrence of major thrust earthquakes along the Himalaya frontal thrust faults.

Three-Dimensional Surface Displacement Field Associated with the 25 April 2015 Gorkha, Nepal, Earthquake: Solution from Integrated InSAR and GPS Measurements with an Extended SISTEM Approach

Three-dimensional surface displacement field associated with the 25 April 2015 Gorkha, Nepal earthquake is derived from an integration of Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) measurements, with an extended SISTEM (Simultaneous and Integrated Strain Tensor Estimation From Geodetic and Satellite Deformation Measurements) approach (ESISTEM) proposed in this study. In ESISTEM approach, both surrounding InSAR and GPS measurements can be used as constraints in deriving surface displacements; while only surrounding GPS measurements are used in SISTEM approach. Besides the constraints from surrounding GPS measurements, the ESISTEM approach makes surrounding InSAR measurements available for constraining the derived deformations based on surface elastic theory for the first time. From the north to the south, derived surface displacement field shows prevailing southward horizontal deformations, and gradually varied vertical deformations ranging from −0.95 to 1.40 m within 120 km to the north of Kathmandu. This reveals that ruptures of Main Himalayan thrust (MHT) system were confined in subsurface and did not propagate to the Main Frontal Thrust (MFT) fault, in accordance with field investigation as well as geodetic and seismic studies. Relation between vertical deformations and earthquake-induced landslides is briefly discussed.

Publisher’s note

This article presents a rebuttal to the entirely ambiguous and unwanted commentary made by Shah (JAES-D-15-00980) on Dar et al. (2014) . The original article was aimed to evaluate the tectono-geomorphic evolution of the Kashmir Valley using geomorphic indices obtained from satellite images and detailed fieldwork. However, Shah while deviating from the core of the article has attempted to build an inexplicable tale about the structural configuration of the region. The comment is primarily based on the misinterpretation regarding the dip direction of a thrust fault. Pertinently, no major ∼SW dipping frontal fault bounding the Pir Panjal Range near Kashmir Valley is shown in the paper by Dar et al. (2014) . The commentator has just recycled already documented text pertaining to general tectonic character of a few ∼NE dipping thrusts i.e., the Main Frontal thrust (MFT) and Raisi Fault (RF). Moreover, some unknown structure named as Kashmir Basin Fault (KBF) by the commentator has been discussed, which does not even exist in the region. The commentary on the whole actually does not relate with the investigation reported by Dar et al. (2014) , hence merits no consideration for publication.

Range Front Structural Geometries and Décollement related Tectonics: An example from Sothern Surghar Range, Trans-Indus Ranges, NW Pakistan

Structural reassessment is described for the eastern and southeastern flank of the north-south oriented segment of Surghar Range, representing the sub-Himalayan frontal structural signatures of northwest Pakistan. Acquisition of outcrop data and structural mapping in the area revealed that the Surghar Range is delimited by a prominent frontal thrust fault which is laterally extended from Kurrum River of Dera Tang in the south to KaIabagh Fault System in the east. Structural geometries describe the presence of an east to southeast vergent thin-skinned fold-and-thrust system developed in the Paleozoic-Mesozoic sequence overlying by a thick overstrain of the Cenozoic rocks. The north-south oriented segment of the range displays tectonics structures developed in response to the coordination of fold-andthrust system. These variant tectonic structures, probably controlled by the east-west directed compressional regime. The study area has been mapped right of Dera Tang in the south to Malla Khel in the north. This segment is comprised of approximately NW-SE oriented thrust fault laterally extended along the range front exploiting different horizons for exhumation at surface. Three different kinds of structures have been developed from south to north as force folding including fault propagation and fault bend folds and transverse strike-slip faults to frontal thrust in the vicinity of Sirkai. A number of anticlinal structures have been mapped in this segment where Siwalik rocks are well exposed at both limbs but the same rocks observed omitted from the fore limbs of some other anticlines. Low to moderate uplifting and strikeslip tectonics are the significant structural style of the southern north-south segment while high uplifting, concentric overturned folding and thrust faulting are the dominant structural mechanism of the northern terminus of this segment. The strike-slip faults observed terminated against the Surghar Thrust in the vicinity of Sirkia. Maturity in tectonic progression, structural growth, maximum crustal telescoping and unearthing of older rock sequences observed from south to north in the mapped area. Chronologically the tectonic phase of transpressional regime observed younger or concurrent as proportional to compressional regime in the region. In general the faulting phase of both regimes is not older than Plio-Pleistocene to sub-Holocene.

Latest Miocene to Quaternary deformation in the southern Chaiwopu Basin, northern Chinese Tian Shan foreland

AbstractBasinward propagation of fold and thrust belts is a crucial geological process accommodating Cenozoic crustal shortening within the India‐Eurasia collision zone. Anticlinal growth strata in the southern Chaiwopu Basin (a piggyback basin) of the northern Chinese Tian Shan foreland record basinward encroachment of the Tian Shan along the Junggar Frontal Thrust Fault. A new magnetostratigraphic section constrains the onset of syntectonic growth strata at circa 6.4 Ma and suggests synchronous basinward thrusting and propagation of the Tian Shan. The intense alluviation in the southern Chaiwopu Basin ceased at circa 0.55 Ma due to significant anticlinal growth and its resultant river incision. More recent anticlinal growth and deformation during the late Quaternary are revealed by folded river terraces developing across the anticline. The terrace height profile indicates that terrace T1Hhas been vertically offset about 0.6 m by thrust faulting since its formation at about 7 Ka. The stratigraphic and geomorphic data presented in this work are helpful to understand the initiation of thrust‐related folding, as well as aggradation and subsequent incision, in foreland basins of the Tian Shan in relation to the India‐Asia collision.