Late Quaternary paleoseismic evidence on the Munébrega half-graben fault (Iberian Range,Spain)

The Munébrega Plio-Quaternary half-graben is a NW-SE trending neotectonic depression located in the central sector of the intraplate Iberian Range (NE Spain). The master fault of the half-graben offsets an Upper Pleistocene pediment deposit, forming an upslope-facing scarp. A trench dug across the fault scarp exposed a 25-m wide deformation zone consisting of graben and horst fault blocks with fissures in the upper part of the scarp, and a monoclinal flexure affected by normal and reverse faults in the lower part of the scarp. We infer a minimum of three faulting events over the past 72 ka, yielding an average (maximum) recurrence interval of 24 ka. The oldest event (72–41 ka) produced an antislope scarp on the relict pediment surface, confining deposition to the downthrown block. Cross-cutting faults affecting sedimentary units deposited in the sediment trap produced by the first event provide evidence for at least two younger events (33–19? ka). The measured cumulative vertical displacement (7.4 m) yield a minimum vertical slip rate of 0.10 ± 0.01 mm/year (2σ error) for the past 72 ka. If the paleoearthquakes ruptured the whole mappable length of the fault (ca. 20 km), they probably had moment magnitudes ca. 6.9 (Stirling et al. Bull Seismol Soc Am, 2002). Such earthquakes would have been more than a magnitude unit larger than the largest ones recorded historically in the Iberian Range. These results suggest that the official seismic hazard assessments, based solely on the historic and instrumental record, may underestimate the seismic hazard in the area.     

Active tectonics of Himalayan Frontal Fault system

In the Sub-Himalayan zone, the frontal Siwalik range abuts against the alluvial plain with an abrupt physiographic break along the Himalayan Frontal Thrust (HFT), defining the present-day tectonic boundary between the Indian plate and the Himalayan orogenic prism. The frontal Siwalik range is characterized by large active anticline structures, which were developed as fault propagation and fault-bend folds in the hanging wall of the HFT. Fault scarps showing surface ruptures and offsets observed in excavated trenches indicate that the HFT is active. South of the HFT, the piedmont zone shows incipient growth of structures, drainage modification, and 2–3 geomorphic depositional surfaces. In the hinterland between the HFT and the MBT, reactivation and out-of-sequence faulting displace Late Quaternary–Holocene sediments. Geodetic measurements across the Himalaya indicate a ~100-km-wide zone, underlain by the Main Himalayan Thrust (MHT), between the HFT and the main microseismicity belt to north is locked. The bulk of shortening, 15–20 mm/year, is consumed aseismically at mid-crustal depth through ductile by creep. Assuming the wedge model, reactivation of the hinterland faults may represent deformation prior to wedge attaining critical taper. The earthquake surface ruptures, ≥240 km in length, interpreted on the Himalayan mountain front through paleoseismology imply reactivation of the HFT and may suggest foreland propagation of the thrust belt.     

Unknown large ancient earthquakes along the Kurai fault zone (Gorny Altai): new results of palaeoseismological and archaeoseismological studies

Palaeoseismological and archaeoseismological studies in the Kurai fault zone, along which the Kurai Range is thrust onto Cenozoic deposits of the Chuya intramontane basin, led to the identification of a long reverse fault scarp 8.0 m high. The scarp segments are primary seismic deformations of large ancient earthquakes. The scarp’s morphology, results of trenching investigations, and deformations of Neogene deposits indicate a thrusting of the piedmont plain onto the Kurai Range, which is unique for the Gorny Altai. Similarly for Northern Tien Shan, we explain this by the formation of both a thrust transporting the mountain range onto the depression and a branching thrust dislocation that forms the detected fault scarp. In a trench made in one of the scarp segments, we identified the parameters of the seismogenic fault – a thrust with a 30° dipping plane. The reconstructed displacement along the fault plane is 4.8 m and the vertical displacement is 2.4 m, which indicates a 7.2–7.6 magnitude of the ancient earthquake. The ¹⁴C age of the humus-rich loamy sand from the lower part of the colluvial wedge constrains the age of the earthquake at 3403–3059 years BP. Younger than 2500 years seismogenic displacements along the fault scarp are indicated by deformations of cairn structures of the Turalu–Dzhyurt-III burial mound, which was previously dated as iron age between the second half of I BC and I AD.     

Gravity anomalies,flexure, and deformation of the converging Indian lithosphere in Nepal and Sikkim–Darjeeling Himalayas

Researchers ubiquitously noted that the common processes of partitioning oblique convergence in response to drag from the trench-hanging plate simultaneously produce radial slips, along-strike translation, and extension parallel to the deformation front. Here, we focus on the area between Nepal and Sikkim–Darjeeling Himalayas, and carry out gravity and finite-element stress modeling of the strike-orthogonal converging Indian lithosphere. We delineate the geometries of different layers and their interfaces through gravity modeling. The optimum model parameters along with rheological parameters of different layers are used for finite-element modeling. Finite-element modeling is done with boundary conditions of keeping the upper surface free and rigidly fixing the section of the northern boundary below the Main Himalayan Thrust. We impart on its frontal section an amount of 6 × 10¹² N/m force, equivalent to resistive force of the Himalayan–Tibet system, and analyze the maximum and minimum compressive stress fields evolved in the lithosphere. We testify our observations with earthquake database and other geophysical and geological studies. We note that an increasing flexing of the Indian lithosphere beyond the Main Boundary Thrust becomes maxima between the Main Central Thrust and South Tibetan Detachment in both the areas; however, more steepening of the Moho boundary is identified in the Sikkim–Darjeeling Himalaya. This abrupt change in lithospheric geometry beneath the Greater Himalaya is likely correlated with the sharp elevation changes in the topography. Although the highest seismicity concentration is dominant in this zone, the Lesser and the Tethys Himalayas in Sikkim–Darjeeling area also record relatively fair seismic activity. More compressive stress field in different layers right within the sharp bending zone supports this observation. We thus propose that the sharp bending zone beneath the Greater Himalaya is suffering maximum deformation, and the deformation is continued in the mantle too. We also identify both right-lateral shear and radial vergence slip, which are presumably associated with the general dynamics and kinematics of the Himalaya.     

Middle Miocene pedological record of monsoonal climate from NW Himalaya (Jammu & Kashmir State), India

The Lower Siwalik Subgroup represented by the Dodenal (Kamlial Formation) and Ramnagar Members (Chinji Formation) is well exposed at Ramnagar, District Udhampur, Jammu & Kashmir State. The Ramnagar Member consists of an alternating sequence of silt and mudstone formed under crevasse-splay and flood-plain environments of deposition. Argillisol and gleysol soils are developed on the Ramnagar Member deposits. Argillisols formed under well-drained conditions at high levels, whereas gleysols formed under poorly drained conditions at low levels of the palaeo-landscape. Geochemical and micromorphological studies of the Ramnagar Member palaeosols suggest formation under wet and humid climatic conditions. Early uplift of the Tibetan Plateau/Himalaya resulted in a contemporaneous change in precipitation and monsoonal climate conditions within the Indian region beginning in Middle Miocene.     

Partitioning of convergence in Northwest Sub-Himalaya: estimation of late Quaternary uplift and convergence rates across the Kangra reentrant,North India

The Kangra reentrant constitutes a ~ 80-km-wide zone of fold-thrust belt made of Cenozoic strata of the foreland basin in NW Sub-Himalaya. Earlier workers estimated the total long-term shortening rate of 14 ± 2 mm/year by balanced cross-section between the Main Boundary Thrust and the Himalayan Frontal Thrust. Geologically estimated rate is nearly consistent with the GPS-derived slip rate of 14 ± 1 mm/year. There are active faults developed within 4–8 km depth of the Sub-Himalayan fold-thrust belt of the reentrant. Dating the strath surfaces of the abandoned fluvial terraces and fans above the thrust faults, the uplift (bedrock incision) rates are computed. The dips of thrust faults are measured in field and from available seismic (depth) profiles. From the acquired data, late Quaternary shortening rates on the Jawalamukhi Thrust (JT), the Soan Thrust (ST) and the Himalayan Frontal Thrust (HFT) are estimated. The shortening rates on the JT are 3.5–4.2 mm/year over a period 32–30 ka. The ST yields a shortening rate of 3.0 mm/year for 29 ka. The corresponding shortening and slip rates estimated on the HFT are 6.0 and 6.9 mm/year during a period 42 ka. On the back thrust of Janauri Anticline, the shortening and slip rates are 2.0 and 2.2 mm/year, respectively, for the same period. The results constrained the shortening to be distributed largely across a 50-km-wide zone between the JT and the HFT. The emergence of surface rupture of a great and mega earthquakes recorded on the reactivated HFT implies ≥100 km width of the rupture. The ruptures of large earthquakes, like the 1905 Kangra and 2005 Kashmir, remained restricted to the hinterland. The present study indicates that the high magnitude earthquakes can occur between the locking line and the active thrusts.     

Crustal density structure from 3D gravity modeling beneath Himalaya and Lhasa blocks,Tibet

The Himalaya and Lhasa blocks act as the main belt of convergence and collision between the Indian and Eurasian plates. Their crustal structures can be used to understand the dynamic process of continent–continent collision. Herein, we present a 3D crustal density model beneath these two tectonic blocks constrained by a review of all available active seismic and passive seismological results on the velocity structure of crust and lower lithosphere. From our final crustal density model, we infer that the present subduction-angle of the Indian plate is small, but presents some variations along the west–east extension of the orogenic belt: The dip angle of the Moho interface is about 8–9° in the eastern and western part of the orogenic belt, and about 16° in the central part. Integrating crustal P-wave velocity distribution from wide-angle seismic profiling, geothermal data and our crustal density model, we infer a crustal composition model, which is composed of an upper crust with granite–granodiorite and granite gneiss beneath the Lhasa block; biotite gneiss and phyllite beneath the Himalaya, a middle crust with granulite facies and possible pelitic gneisses, and a lower crust with gabbro–norite–troctolite and mafic granulite beneath the Lhasa block. Our density structure (<3.2 g/cm³) and composition (no fitting to eclogite) in the lower crust do not be favor to the speculation of ecologitized lower crust beneath Himalaya and the southern of Lhasa block.     

The Manyas fault zone (southern Marmara region,NW Turkey): active tectonics and paleoseismology

The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.     

Active tectonic and palaeoseismological features of the western section of Mustafakemalpaşa Fault; Bursa,NW Anatolia

The Mustafakemalpa?a Fault (MF), located among Manyas, Ulubat and Orhaneli faults, is a right lateral strike-slip and 47 km in length. The MF begins with a pressure ridge at the west and exhibits complex jog terminations at east ends in restraining left stepovers. The western section of the fault bounds Miocene and Quaternary units and continues towards ?lyasç?lar. The central segment of the fault, starts with approximately 750-m leftward stepover, exhibits a sinusoidal geometry between Kapakl?oluk and Kabulbaba. In this section, MF traverses mountainous terrain and cuts Ophiolite, Jurassic limestones and Miocene detritals, forming dextral faulting features and gaining reverse component. The eastern section exhibits left stepping en-echelon pattern and consists 2.5-km offset on the Orhaneli River. In this study, palaeoseismological findings related to the Holocene activity and active tectonic properties of the MF are presented. The trenches exposed mismatched stratigraphy, demonstrating evidence of events across the fault. We identified three events (before BC 2190, later AD 1425 and 1850) that have occurred during the past 4000 years. We suggest a long non-characteristic recurrence interval and ~0.7 mm/y slip-rate for MF, based on trench data and offset of the Late Pliocene drainage of Orhaneli River.     

Reply to the discussion by F. Gutiérrez,P. Lucha,J. Guerrero,M. Gutiérrez and D. Carbonel on the article ‘Paleoseismological analysis of an intraplate extensional structure: the Concud fault (Iberian Chain,eastern Spain)’

This reply tackles the three main points of discussion of the comment, carefully distinguishing those constructive contributions from the potentially confusing ones. (1) We accept that we should have utilised previously published datings of the middle terrace, even if we consider them to be less reliable than the used ones, so broadening the slip-rate range from 0.23–0.33 mm/y to 0.16–0.33 mm/y. Nevertheless, their revision of the post-middle terrace slip rate charges us two contradictory imputations: that we underestimate the throw in a 25% (36 m vs. 47 m) and that this results in ‘anomalously high slip rates’. We analyse the adduced error, and we confirm our initial estimate based on our more reliable stratigraphic marker, so rejecting both criticisms. (2) About the paleoseismological interpretation at Los Baños trench, we appreciate the hint about displacement partitioning on the master fault and in our hypothetical blind normal fault during the last three events; however, such partitioning was already considered in our retrodeformation analysis. We believe that there is enough evidence for the two events questioned by the commenters, as well as for the interpretation of the colluvial wedge that evidences one of them. (3) With respect to the fault affecting the youngest terrace: (a) both traces exposed on orthogonal road-cut slopes belong to the same normal fault, and we prove it by means of basic structural constructions, and (b) it does not exhibit any feature suggesting a non-tectonic origin, as the commenters state.     

Late Quaternary activity of the Pajarito fault, Rio Grande rift of northern New Mexico, USA

The Pajarito fault forms the western margin of the Rio Grande rift in north-central New Mexico, and lies adjacent to Los Alamos National Laboratory, a major Federal research facility. Vertical displacement on this normal fault over the past 1.2 Ma has created a 50- to 120-m-high fault scarp on Bandelier Tuff (1.2 Ma), yielding a long-term average slip rate of ca. 0.1 mm/yr. In support of a Laboratory-wide seismic hazards assessment, we excavated 14 trenches in the Pajarito fault zone to determine the age of the most recent displacement event, the recurrence interval between events, the displacement per event, and the variability in slip rate and recurrence through time. The large number of trenches was required by the large height of the fault scarp and the complexity of the fault zone. Only about half the trenches contained significant thicknesses of Holocene deposits, but in those trenches there was clear evidence for an early-to-mid-Holocene displacement event. The previous event was at least 20–40 ka, and the average recurrence interval over the past ca. 300 ka was about 20–40 kyr. We infer that much of the structural relief across this fault developed soon after eruption of the Bandelier Tuff between 1.0 and 1.2 Ma, and that slip rate slowed considerably after that time.     

Seismic ray direction anomalies and relative residuals of earthquakes recorded at Gauribidanur array

Slowness and azimuthal anomalies provide valuable information about lateral inhomogeneities within the crust and mantle of the earth. Over 300 earthquakes (distance range 14°–36° and azimuth 0°–360°) recorded at Gauribidanur seismic array (GBA) in southern India, were analysed using adaptive processing techniques. Slowness anomalies upto 1·3 sec/deg and azimuthal anomalies upto 8° have been observed in the present analysis. Slowness anomaly patterns for Java trench, Mid-Indian oceanic ridge earthquakes are more consistent as compared to the events originating in the Himalayan and Hindukush regions. A significant feature of the azimuthal anomaly pattern was the distinct absence of any positive anomalies from earthquakes occurring in mid-oceanic ridge. These anomalies have also been analysed as a function of epicentral distance and are mainly attributed to the transition zones occurring between 400–700 km depth ranges in the Indian upper mantle regions. Relative residuals between the stations of GBA have very little dependence on azimuth and distance. An anomalous structure beneath the array in the direction of the Java trench region (azimuth 116–126°) has been postulated on the basis of large systematic slowness vectors observed.     

The Red River sediment budget in the Yinggehai and Qiongdongnan basins,northwestern South China Sea,and its tectonic implications

ABSTRACT

The rapid uplift of the Tibetan plateau, the intense movement of the Ailao Shan-Red River Shear Zone (ARSZ), and the related climate change during the Cenozoic Indo-Asian collision have been widely studied; however, their timings varied considerably due to different data and methods used. As these events have been documented in the Red River sediment that came from the eastern Tibetan plateau and the Red River region and eventually deposited in the offshore Yinggehai and Qiongdongnan basins, here these events can be explored by calculating and analysing the Red River sediment budget, especially in the Qiongdongnan basin based on dense seismic profiles and wells. Results show that the Red River sediment mainly accumulated in the Yinggehai basin and the west part of the Qiongdongnan basin, and there are three sedimentary accumulation peaks in the Red River sediment budget during ~29.5–21, ~15.5–10.5, and ~5.5–0 Ma. By further comparing with previous studies on the timings of these events, it is inferred that the first sedimentary peak, prior to the onset of the monsoon intensification (~22 Ma), was probably driven by an intense left-lateral movement of the ARSZ in ~29.5–21 Ma. The second peak (~15.5–10.5 Ma), however, reflects a rapid uplift of the Tibetan plateau after the cessation of the left-lateral strike slip of the ARSZ. The third peak (~5.5–0 Ma) is most likely linked with a right-lateral movement of the ARSZ and the related climate change. Overall, the Red River sediment budget from the offshore Yinggehai and Qiongdongnan basins provides an important constraint on the timings of these tectonic events as well as the related climate change during the Cenozoic Indo-Asian collision.     

Reconstruction of specific mass balance for glaciers in Western Himalaya using seasonal sensitivity characteristic(s)

Seasonal sensitivity characteristics (SSCs) were developed for Naradu, Shaune Garang, Gor Garang and Gara glaciers, Western Himalaya to quantify the changes in mean specific mass balance using monthly temperature and precipitation perturbations. The temperature sensitivities were observed high during summer (April–October) and precipitation sensitivities during winter months (November–March), respectively. The reconstructed mass balance correlates well with the field and remote sensing measurements, available between 1980 and 2014. Further, SSCs were used with the monthly mean temperatures and precipitation estimates of ERA 20CM ensemble climate reanalysis datasets to reconstruct the specific mass balance for a period of 110 years, between 1900 and 2010. Mass balance estimates suggest that the Shaune Garang, Gor-Garang and Gara glaciers have experienced both positive and negative mass balance, whereas the Naradu glacier has experienced only negative mass balance since 1900 AD. Further, a cumulative loss of \(-133 \pm 21.5\) m.w.e was estimated for four glaciers during the observation period. This study is the first record from Indian Himalaya in evaluating the mass balance characteristics over a century scale.     

Late Quaternary episodic displacement on a sackung scarp in the central Spanish Pyrenees. Secondary paleoseismic evidence?

A sackung scarp has been investigated by trenching in the central Spanish Pyrenees. This feature is located 18 km to the SW of the North Maladeta Fault, which is the most probable source of the M_w 5.3 Vielha earthquake of 1923. Three displacement events have been inferred for the trenched sackung based on colluvial wedge stratigraphy and fault truncation. The increasing amount of deformation in each successive faulting event may be related to the progressive weakening of the slope through time. A minimum vertical slip rate of 0.19 mm/yr has been calculated for the sackung scarp. Several arguments suggest that the episodic displacement of the analysed sackung is controlled by strong seismic shaking: (a) Spatial association of the sackung features with the North Maladeta Fault; (b) Episodic displacement with a millennial recurrence (5.6 kyr) consistent with the expectable earthquake recurrence interval for a low slip rate fault, like the neighbouring North Maladeta Fault. Demonstrating in future investigations that the sackung features in the area constitute archives of large paleoearthquakes would be of great interest for seismic hazard assessments. They might help to improve the catalogue of paleoearthquakes and might provide information on earthquake recurrence intervals and the age of the most recent event (MRE).     

Petrography and provenance of Upper Cretaceous – Palaeogene sandstones in the foreland basin system of Central Nepal

Sedimentary deposits of the Cretaceous to Miocene Tansen Group of Lesser Himalayan association in central Nepal record passive-margin sedimentation of the Indian Continent with direct deposition onto eroded Precambrian rocks (Sisne Formation onto Kaligandaki Supergroup rocks), succeeded by the appearance of orogenic detritus as the Indian continent collided with Asia on a N-dipping subduction zone. Rock samples from two field traverses were examined petrographically and through detrital zircon U–Pb dating, one traverse being across the Tansen Group and another across the Higher and Tethyan Himalaya (TH). The Tansen Group depositional ages are well known through fossil assemblages. We examined samples from three units of the Tansen Group (Amile, Bhainskati, and Dumri Formations). The Sedimentary petrographic data and Qt F L and Qm F Lt plots indicate their ‘Quartzose recycled’ nature and classify Tansen sedimentary rocks as ‘recycled orogenic’, suggesting Indian cratonic and Lower Lesser Himalayan (LLH) sediments as the likely source of sediments for the Amile Formation (Am), the TH and the Upper Lesser Himalaya (ULH) as the source for the Bhainskati Formation (Bk), and both the Tethyan and Higher Himalaya (HH) as the major sources for the Dumri Formation (Dm). The Cretaceous–Palaeocene pre-collisional Am is dominated by a broad detrital zircon U–Pb ~1830 Ma age peak with neither Palaeozoic nor Neoproterozoic zircons grains, but hosts a significant proportion (23%) of syndepositional Cretaceous zircons (121–105 Ma) would be contributions from the LLH volcanosedimentary arc, Gangdese batholith (including the Xigaze forearc). The other formations of the Tansen Group are more similar to Tethyan units than to Higher Himalaya Crystalline (HHC). From the analysed samples, there is a lack of distinctive evidence or HH detritus in the Tansen basin. Furthermore, the presence of ~23±1 Ma zircons from the HH unit suggests that they could not have been exposed until the earliest Miocene time.     

Surface displacement estimation using multi-temporal SAR Interferometry in a seismically active region of the Himalaya

The Indian subcontinent is one of the most earthquake-prone regions of the world. The Himalayas are well known for high seismic activity, and the ongoing northwards drift of the Indian plate makes the Himalaya geodynamically active. During the last three decades, several major earthquakes occurred at the plate interiors and boundaries in this subcontinent causing massive losses. Therefore, one of the major challenges in seismology has been to estimate long recurrence period of large earthquakes where most of the classical Probabilistic Seismic Hazard Approaches fail due to short catalogues used in the prediction models. Therefore, during the past few decades, the Himalayan region has been studied extensively in terms of the present ongoing displacements. In this context the present study has been carried out to estimate the surface displacement in a seismically active region of the Himalaya, in between Ganga and Yamuna Tear, using multi-temporal Synthetic Aperture Radar (SAR) Interferometry. A displacement rate of 6.2–8.2 mm/yr in N14°E direction of the Indian plate towards the Tibetan plate has been obtained. It has been noted that the estimated convergence rate using Differential SAR Interferometry technique is relatively low in comparison with those obtained from previous classical studies. The reported low convergence rate may be due to the occurrence of silent/quite earthquakes, aseismic slip, differential movement of Delhi Hardwar ridge, etc. Therefore, in view of the contemporary seismicity and conspicuous displacements, a study of long-term observations of this surface movement has been recommended in future through a time-series SAR Interferometry analysis.     

The Pelona–Orocopia–Rand and related schists of southern California: a review of the best-known archive of shallow subduction on the planet

ABSTRACT

The Pelona–Orocopia–Rand and related schists of southern California are an archetypal example of an exhumed shallow subduction complex. ‘The schist’ comprises mainly trench materials underthust beneath continental arc rocks during Late Cretaceous–early Cenozoic collision of one or more oceanic plateaux with southern California. The arc-on-trench relationship, without intervening mantle or lowermost crust, implies that significant subduction erosion accompanied shallow subduction. Upsection increases in metamorphic grade (~150 ± 100°C/km) and spatial variations in age and peak temperature provide an ~50 million year long record of tectonic underplating within a cooling system. Evidence for palaeoseismic events in earliest formed and hottest (locally transitional granulite grade) schists provides a possible field-based record of episodic tremor and slow slip events such as detected in several modern shallow subduction zones. Structural ascent of the schist was achieved in distinct Late Cretaceous–early Eocene and late Oligocene–early Miocene extensional pulses, the first during collapse of gravitationally unstable upper plate assemblages and accompanied by trench-directed (top-NE) lower plate extrusion and the second corresponding temporally, spatially, and in character with core complex formation in the SW United States. The line between schist and core complex belts is blurred by the recent discovery of schist within 40 km of the nearest core complex and containing synkinematic Miocene intrusions, a hallmark of SW U.S. core complexes. The history of schist assembly, metamorphism, and exhumation provides the most complete field-based record of thermo-mechanical processes, subduction erosion and tectonic underplating in particular, that operated during a shallow subduction event. Future cross-disciplinary investigations of, and comparisons between, the schist and other possible ancient (e.g. Swakane gneiss, Sanbagawa belt, Qiangtang terrane) and modern (e.g. Cascadia, SW Japan, central Mexico, Chile) shallow subduction zones will yield new insights into the tectonic and petrologic processes that operate within such systems.     

Mapping crustal structure beneath southern Tibet: Seismic evidence for continental crustal underthrusting

Receiver function imaging along a temporary seismic array (ANTILOPE-2) reveals detailed information of the underthrusting of the Indian crust in southern Tibet. The Moho dips northward from ~ 50 km to 80 km beneath the Himalaya terrane, and locally reaches ~ 85 km beneath the Indus–Yalung suture. It remains at ~ 80 km depth across the Lhasa terrane, and shallows to ~ 70 km depth under the Qiangtang terrane. An intra-crustal interface at ~ 60 km beneath the Lhasa terrane can be clearly followed southward through the Main Himalaya Thrust and connects the Main Boundary Thrust at the surface, which represents the border of the Indian crust that is underthrusting until south of the Bangong–Nujiang Suture. A mid-crustal low velocity zone is observed at depths of 14–30 km beneath the Lhasa and Himalaya terranes probably formed by partial melt and/or aqueous fluids.     

Environmental geoinformaicts of fast growing Himalaya’s foothill towns and surrounding: concept and implementation

Himalaya foothill zone have fragile geo-environment due to active tectonics and dynamic hydrological process and its associated reshaped geomorphology. Rapid urbanization and development of new colonies leads to high rate of land use change and natural resource degradation since last three decades which has been accumulating the fragility of the area. Consequently entire Himalaya foothill zone requires a comprehensive local level geo-environmental appraisal for effective sustainable development planning of the region. Keep in view this; the Ramnagar Himalayan Foothill area (RHFA) in district Nainital, Uttarakhand (India) has been selected for the case illustration. The main objective of the study was to develop a GIS database on Ramnagar environmental geo-informatics (REGI) to facilitate all the concern line departments to implement their socioeconomic developmental activities in the most suitable and safe places throughout the study area. REGI suggests, although landscape of the study area have few favorable conditions for the inhabitant (i.e. maximum proportion (92 %) of the study area enjoys sub-tropical to sub-temperate climatic conditions, easy approachable, thick vegetation cover, rich water resources) but the active tectonics and dynamic hydrological process and its associated reshaped geomorphology poses a stressed geo-environment which need to be consider to formulate a decision support system (DSS) for sustainable development planning.