Main Thrust Fault Research Articles

DSHA Based Estimation of Peak Ground Acceleration for Madhubani and Supaul Districts Near Bihar–Nepal Region

The districts of Madhubani and Supaul lie near Bihar–Nepal border along foothills of Himalaya. Different attenuation relationships applicable for the Himalayan region have been used to estimate the site-specific Peak Ground Acceleration (PGA) for the Madhubani and Supaul region on the basis of Deterministic Seismic Hazard Assessment (DSHA) study. Seismicity data have been collected from IMD, New Delhi and forty seismotectonic sources were recognized in the region from Seismotectonic Atlas of India (GSI in Seismotectonic atlas of India and its environs, Geological Survey of India, Kolkata, 2000). Hypocentral distances have been measured using ArcGIS software. Maximum Peak ground acceleration value is found to occur for Main Central Thrust fault for both these districts.

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.

The three-dimensional electrical structure and metallogenic prospect of the Ning (Nanjing)-Wu (Wuhu) basin and the southern adjacent area in eastern China

The Ning (Nanjing city)-Wu (Wuhu City) volcanic basin, which is famous for its large-scale, high-grade ore deposits, is a typical iron ore district in the middle-lower reaches of the Yangtze River Metallogenic Belt (MLRYMB). The southern part of the basin is primarily covered by Quaternary strata. Few in depth studies have been conducted on this area. Due to the increasing demand for mineral resources and the controversy over regional tectonic models, some fundamental geological issues still need to be addressed. These questions include defining the characteristics of the geological structures and the mineralization prospects. Therefore, a three-dimensional (3D) magnetotelluric survey was conducted in this area to obtain a deep 3D electrical model. It was found that the Yangtze fault (CJF) and the main thrust fault (MTF) in the upper crust have the same deep (middle crust to upper mantle) setting and part of the thrust tectonics of the metallogenic belt. The southern boundary of the Ning-Wu Basin is located on a fault belt (boundary fault, BF) with a northeast-east (or east-west) strike influenced by the MTF in the southern part of the study area. Bounded by the BF and MTF, the southeastern part of the study area exhibits signs of uplift. With the recent discovery of a large porphyry copper deposit to the southeastern part of the study area, which is located in an uplift structure similar to the one south of the Ning-Wu Basin, this local uplift could have potential mineralization prospects based on a previous mineralization theory developed for this belt.

A constant slip rate for the western Qilian Shan frontal thrust during the last 200 ka consistent with GPS-derived and geological shortening rates

Active thrust faulting at the front of the Qilian Shan accommodates the northeastward growth of the Tibetan Plateau, however, the lifespan of individual faults and their slip history on different timescales remain largely unknown. Here, we show that the main range-bounding thrust fault of the western Qilian Shan has accrued tectonic slip at an almost constant rate during the last ∼200 ka, and possibly since fault initiation in the mid-Miocene. Our finding is based on 10Be ages from a flight of five deformed fluvial terraces along the Hongshuiba river, which constrain the vertical slip rate of the Qilian Shan frontal thrust to be 1.2±0.1 m/ka during the last 200 ka. With a fault dip of 30±5° constrained by seismic reflection data, we obtain a horizontal shortening rate of 2.0±0.3 m/ka. This value is consistent with both the short-term shortening rate of 1.7±0.3 mm/a derived from GPS data and the long-term shortening rate of 2.1±0.4 m/ka, which is based on a balanced geological cross-section. The latter provides a total shortening estimate of 25±3 km since the thrust fault initiated 12±2 Ma ago. The agreement between the shortening rates on the range of timescales between 100 and 107 years suggests that the western Qilian Shan frontal thrust has slipped at a steady rate since its initiation and implies that this fault is the main structure responsible for the growth of the western Qilian Shan.

Development of local magnitude scale for the Northern Punjab, Pakistan

We developed a local magnitude scale for the Northern Punjab (Potwar Plateau and Salt Range), using seismic data of CES (Centre for Earthquake Studies). The region is tectonically stable, but surrounded by active geological structures (i.e., Main Boundary Thrust, Sulaiman Range, and Jhelum Fault). The imparted stresses adjust both seismically (moderate to small magnitude earthquakes) and aseismically in decollement. Previously, Southern California magnitude scale was being used to determine local magnitude for compilation of seismic catalog. Difference in geology and tectonics between Southern California and Northern Punjab may lead to systematic errors in hazard assessment based on this catalog. To address this problem, we selected 231 seismic events for a period of 07 years with ML 2.0 and above, that correspond to 2800 records on 21 seismic stations. We chose data of seismic events with hypocentral distance less than 600 km and recorded on five stations at least. We then inverted the synthetic Wood-Anderson amplitudes of selected data for station and distance corrections. Accordingly, the new magnitude scale for Northern Punjab is given by the following: ML = logA + 0.869log(r) + 0.00115(r) − 1.53, where A is the amplitude in nanometers on synthetic Wood-Anderson seismograph and r is the hypocentral distance in kilometers. We observed lower attenuation of seismic waves in our study area as compared to Southern California. Lower standard deviation (i.e., reduction in variance to 45.4% ) in magnitude residuals shows that there is less deviation for newly developed scale as compared to that of Southern California scale. Values of station correction factors for different stations of local network vary between − 0.5 to + 0.5, which suggest variation in station site effects.

Segmentation of the Main Himalayan Thrust Revealed by Low‐Temperature Thermochronometry in the Western Indian Himalaya

AbstractDespite remarkable tectonostratigraphic similarities along the Himalayan arc, pronounced topographic and exhumational variability exists in different morphotectonic segments. The processes responsible for this segmentation are debated. Of particular interest is a 30‐ to 40‐km‐wide orogen‐parallel belt of rapid exhumation that extends from central Nepal to the western Himalaya and its possible linkage to a midcrustal ramp in the basal décollement, and the related growth of Lesser Himalayan duplex structures. Here we present 26 new apatite fission track cooling ages from the Beas‐Lahul region, at the transition from the Central to the Western Himalaya (~77°–78°E) to investigate segmentation in the Himalayan arc from a thermochronologic perspective. Together with previously published data from this part of the orogen, we document significant lateral changes in exhumation between the Dhauladar Range to the west, the Beas‐Lahul region, and the Sutlej area to the east of the study area. In contrast to the Himalayan front farther east, exhumation in the far western sectors is focused at the frontal parts of the mountain range and associated with the hanging wall of the Main Boundary Thrust fault ramp. Our results allow us to spatially correlate the termination of the rapid exhumation belt with a midcrustal ramp to the west. We suggest that a plunging anticline at the northwestern edge of the Larji‐Kullu‐Rampur window represents the termination of the Central Himalayan segment, which is related to the evolution of the Lesser Himalayan duplex.

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.

A low-angle normal fault and basement structures within the Enping Sag, Pearl River Mouth Basin: Insights into late Mesozoic to early Cenozoic tectonic evolution of the South China Sea area

The basement structure of the Cenozoic Enping Sag, within the Pearl River Mouth Basin on the northern margin of South China Sea, is revealed by borehole-constrained high-quality 3D seismic reflection data. Such data suggest that the Enping Sag is bounded in the north by a low-angle normal fault. We interpret this low-angle normal fault to have developed as the result of the reactivation of a pre-existing thrust fault part of a pre-Cenozoic thrust system. This is demonstrated by the selective reactivation of the pre-existing thrust and by diffuse contractional deformation recognized from the accurate analysis of basement reflections. Another significant result of this study is the finding of some residual rift basins within the basement of the Enping Sag. Both the thrust system and the residual basins are interpreted to have developed after the emplacement of continental margin arc-related granitoids (J3–K1) that define the basement within the study area. Furthermore, seismic sections show that the pre-existing residual rift basins are offset by the main thrust fault and they are both truncated by the Tg unconformity. These structural relationships, interpreted in the frame of previous studies, help us to reconstruct a six-event structural evolution model for the Enping Sag from the late Mesozoic to the early Cenozoic. In particular, we interpret the residual rift basins to have formed as the result of back-arc extension due to the slab roll-back of the Paleo-Pacific Plate subduction in the early K2. The thrust system has recorded a compressional event in the late K2 that followed the back-arc extension in the SCS area. The mechanism of this compressional event is still to be clarified, and might be related to continuous subduction of the Paleo-Pacific Plate or to the continent-continent collision between a micro-continental block and the South China margin.

Effect of basement structure and salt tectonics on deformation styles along strike: An example from the Kuqa fold–thrust belt, West China

The Kuqa fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, décollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core detachment fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal décollement, whereas the supra-salt layer shows overlapping, discontinuous faults and folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.

Structure and Stratigraphy of Rumbli and Panjar Areas of Kashmir and Pakistan with the Aid of GIS

ABSTRACT The project area lies in the southern part of the Hazara Kashmir syntaxis. The Hazara Kashmir syntaxis is an antiformal structure. The project area includes Rumbli, Namb, Chatrora, Chachan, Panjar, Barathian and Utrinna areas of Rawalpindi and Sudhnoti districts. The southeastern limb of the Hazara Kashmir syntaxis is imbricated along Punjal thrust, Main Boundary thrust and Riasi fault. The Jhelum fault truncates the western limb of Hazara Kashmir syntaxis. The core of syntaxis comprises of Himalayan molasse deposits. These molasse deposits represent the part of cover sequence of Indian plate. These Himalayan molasse deposits include the Early to Middle Miocene Kamlial Formation, Middle to Late Miocene Chinji Formation, Late Miocene Nagri Formation and Late Miocene Dhok Pathan Formation. The area is highly deformed resulting folds and faults. The major folds in the project area are the Panjar anticline, Barathian syncline, Barathian anticline, Rumbli anticline, Chatrora antiformal syncline and Namb syncline. The folds are either northwest-southeast trending or southwest-northeast trending. The folds are asymmetric, open, and gentle and close in nature. The folds are southwest, northeast or southeast vergent. The Jhelum fault truncates the northeast and northwest trending structures. The folds and faults are the result of northeast-southwest or northwest-southeast Himalayan compression.

Dual-vergence structure from multiple migration of widely spaced OBSs

The detailed structure of the northern Cascadia basin and frontal ridge region was obtained using data from several widely spaced ocean bottom seismometers (OBSs). Mirror imaging was used in which the downgoing multiples (mirror signal) are migrated as they provide information about a much larger area than imaging with primary signal alone. Specifically, Kirchhoff time migration was applied to hydrophone and vertical geophone data. Our results indicate remarkable structures that were not observed on the northern Cascadia margin in previous single-channel or multi-channel seismic (MCS) data. Results show that, in these water depths (2.0–2.5km), an OBS can image up to 5km on either side of its position on the seafloor and hence an OBS spacing of 5km is sufficient to provide a two-fold migration stack. Results also show the top of the igneous oceanic crust at 5–6km beneath the seafloor using only a small airgun source (120in.3). Specifically, OBS migration results clearly show the continuity of reflectors which enabled the identification of frontal thrusts and a main thrust fault. These faults indicate, for the first time on this margin, the presence of a dual-vergence structure. These kinds of structures have so far been observed in <0.5% of modern convergent margins and could be related to horizontal compression associated with subduction and low basal shear stress resulting from over-pressure. Reanalysis of previous MCS data from this region augmented the OBS migration results and further suggests that the vergence switches from seaward to landward around central Vancouver Island. Furthermore, fault geometry analyses indicate that the total amount of shortening accommodated due to faulting and folding is about 3km, which suggest that thrusting would have started at least ∼ 65ky ago.

Stress change from the 2015 Mw 7.8 Gorkha earthquake and increased hazard in the southern Tibetan Plateau

We examine the co-seismic Coulomb stress change induced by the 2015 Mw 7.8 Gorkha, Nepal earthquake and investigate its influence on the seismic hazard in the southern Tibetan Plateau. We find that the location of the aftershocks coincides with areas where stress was enhanced. This stress enhanced area also covers the west and the shallow fault section updip of the 2015 Gorkha earthquake rupture in the Main Himalayan Thrust fault (MHT), signaling the raising hazard of the seismic gaps in the west and south to Kathmandu. The 2015 Gorkha earthquake strongly interacted particularly with the normal and thrust faults in the distance of around 100–250km from the rupture zone by bringing stress closer to the Coulomb failure. This fault interaction process increased stress by 12kPa and 100kPa at the southern end of the Tingkye and the Nyalam normal faults, respectively, triggering the Ms 5.9 Tingri earhquake on 25 May 2015 and the Ms 5.3 Nyalam earthquake on 26 May 2015. Stress in the Main Frontal Himalaya Thrust fault (MFT), the Main Boundary Thrust fault (MBT) in the Lalitpur area of Nepal was promoted by 40–100kPa. Such stress transfer should facilitate the future rupture on these active faults and raise seismic hazard in the southern Tibetan Plateau.

Deterministic strong ground motion study for the Sitamarhi area near Bihar–Nepal region

Deterministic seismic hazard assessment based study using various attenuation relationships has been taken up to find out the peak ground acceleration (PGA) for Sitamarhi region situated near the Bihar Nepal border. Seismicity data were collected from Indian Meteorological Department, New Delhi and Seismotectonic Atlas of India (GSI 2000) and 38 seismotectonic sources were identified in the region. The results show that the Main Central Thrust and West Patna subsurface fault are the two main faults, which contribute to maximum PGA values for Sitamarhi region. The calculated PGA values are in confirmation with the observed values from other sources.

Using geodetic data to calculate stress changes on faults in the Tibetan Plateau caused by the 2015 Mw7.8 Nepal earthquake

The 2015 Mw7.8 Nepal earthquake occurred on the segment of the main Himalayan thrust fault between the Indian and Eurasian plates, and caused serious casualties. This earthquake may produce a profound impact on the evolution of the Tibetan Plateau and have brought a stress loading to faults within the plateau. In this paper, a high-resolution slip distribution of the 2015 Nepal earthquake is inverted from the InSAR and GPS data in the near field, and is used to compute the evolution of the cumulative Coulomb stress changes on faults in the earthquake-prone zone in the Tibetan Plateau. In the given reasonable parameters, the calculated co- and post-seismic stress changes on faults do not exceed 1.0kPa at the north of latitude 32° in the Tibetan Plateau. The largest positive stress changes occur on the South Tibet Detachment fault, and the magnitudes are much less than 100kPa. The estimated seismicity rate change on the segment of the South Tibet Detachment fault can be up to a level of two hundred thousandths. This indicates that there is a high hazard of earthquake triggering in the South Tibet Detachment fault and its adjacent regions. In the northern and eastern Tibetan Plateau, the estimated seismicity rate changes are lower than a level of one thousandth. However, some faults with a relative high background seismicity rate, such as the Xianshuihe and Longmenshan faults, may have a high hazard of earthquake triggering in the future.

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).

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.

Knowledge based landslide susceptibility mapping in the Himalayas

Landslides are common geological hazard occurring in the mountainous region. The Himalayan belt is prone to landslide disasters, which is directly linked to the prosperity and development of the area. The present study was carried out around the Chamoli-Joshimath area, which is situated in the Northernmost-belt of the Garhwal Himalaya, India. A strategic road connecting Tibet which also links the famous Hindu temples Badrinath and Kedarnath traverses the area. The main purposes of the present study is to delineate the landslide susceptible zones in the area so that it could be helpful towards landslide disaster risk reduction and to highlight the applicability of knowledge based susceptibility mapping method in the Himalayas. The area comprises low-to-high grade metamorphic rocks as well as carbonate rocks such as limestone and dolomite. In the study area, most of the landslides occur along the road and river sections, and in the thrust or fault zones. The landslide zones are strongly controlled by the Main Central Thrust and other faults and the resulting geomorphic condition. Most of the unstable slopes are prone to plane and wedge failures. There are many active and dormant landslides (covered by vegetation) in the area. The active landslides are due to reactivation of pre-existing ones. The predicted landslide susceptible zones are in good agreement with the historical landslide locations, which is good indication that knowledge based landslide susceptibility mapping can be successfully applied in the Himalayas provided the causative factors are thoroughly understood.

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.

Aftershock activity of the 2015 Gorkha, Nepal, earthquake determined using the Kathmandu strong motion seismographic array

The characteristics of aftershock activity of the 2015 Gorkha, Nepal, earthquake (Mw 7.8) were evaluated. The mainshock and aftershocks were recorded continuously by the international Kathmandu strong motion seismographic array operated by Hokkaido University and Tribhuvan University. Full waveform data without saturation for all events enabled us to clarify aftershock locations and decay characteristics. The aftershock distribution was determined using the estimated local velocity structure. The hypocenter distribution in the Kathmandu metropolitan region was well determined and indicated earthquakes located shallower than 12 km depth, suggesting that aftershocks occurred at depths shallower than the Himalayan main thrust fault. Although numerical investigation suggested less resolution for the depth component, the regional aftershock epicentral distribution of the entire focal region clearly indicated earthquakes concentrated in the eastern margin of the major slip region of the mainshock. The calculated modified Omori law’s p value of 1.35 suggests rapid aftershock decay and a possible high temperature structure in the aftershock region.

Triggered slip on a back reverse fault in the Mw6.8 2013 Lushan, China earthquake revealed by joint inversion of local strong motion accelerograms and geodetic measurements

The 2013 Mw6.8 Lushan, China earthquake occurred in the southwestern end of the Longmenshan fault zone. We jointly invert local strong motion data and geodetic measurements of coseismic surface deformation, including GPS and InSAR, to obtain a robust model of the rupture process of the 2013 Lushan earthquake. Our joint inversion best model involves the rupture of two opposing faults during the Lushan earthquake, a main fault and a secondary fault. It is only when the secondary fault is included that both the GPS and InSAR measurements are fit along with the near-field strong motion. Over 75% of the computed moment was released in slip on the main fault segment, a northwest dipping, listric thrust fault, with buried thrust and dextral strike-slip at hypocenter depths, and with only minor slip closer to the surface. The secondary fault mainly involved oblique thrust slip or pure dextral strike-slip at shallower depths, and accounts for just under 24% of the moment released in the Lushan earthquake. Coulomb stress changes of about 0.5MPa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault. Our coseismic slip model is consistent with a sub-horizontal and east–west to southeast–northwest trending most compressive stress. Our inferred coseismic slip model is also consistent with previous GPS derived models of strain accumulation on the Longmenshan fault system.