challenges to global mineral resource security and options for future supply minerals are vital to support economic growth and the functioning of modern society demand for minerals is increasing as global population expands and minerals are used in a greater rangeof applications particularlyassociated with the deployment of new technologies while con cerns about future mineral scarcity have been expressed these are generally unfounded and based on over simplistic analysis this paper considers recent debate around security of mineral supply and technical geosciences based options to improve utilization of the resource base and contribute to replenishing reserves history suggests that increasing demand for minerals and higher prices will generally lead to technological and scientific innovation that results in new or alternative sources of supply recent assessments of global mineral endowment suggest that society should be optimistic about its ability to meet future demand for minerals provided that there is continued innovation and investment in science and technology reducing energy consumption and breaking the current link between metal production and greenhouse gas emissions are among the greatest challenges to secure a sustainable mineral supply however widespread adoption of low carbon mineral extraction technologies underpinned by multidisciplinary research and increased global utilization of low carbon energy sources will allow these challenges to be met gold open access this article is published under the terms of the cc by 3 0 license

crustal balance and crustal flux from shortening estimates in the central andes abstract the central andes of south america form the second largest high elevation plateau on earth extreme elevations have formed on a noncollisional margin with abundant associated arc magmatism it has long been thought that the crustal thickness necessary to support andean topography was not accounted for by known crustal shortening alone we show that this may in part be due to a two dimensional treatment of the problem a three dimensional analysis of crustal shortening and crustal thickness shows that displacement of material towards the axis of the bend in the central andes has added a significant volume of crust not accounted for in previous comparisons we find that present day crustal thickness between 12 s and 25 s is accounted for 10 to 3 with the same shortening estimates and the same assumed initial crustal thickness as had previously led to the conclusion of a 25 35 deficit in shortening relative to volume of crustal material we suggest that the present day measured crustal thickness distribution may not match that predicted due to shortening and substantial redistribution of crust may have occurred by both erosion and deposition at the surface and lower crustal flow in regions of the thermally weakened middle and lower crust

assessment of teleseismically determined source parameters for the april 25 2015 mw 7 9 gorkha nepal earthquake and the may 12 2015 mw 7 2 aftershock on april 25 2015 a major m w 7 9 thrust earthquake ruptured the deeper portion of the seismogenic plate boundary beneath nepal along which india is underthrusting eurasia an m w 7 2 aftershock on may 12 2015 extended the eastern down dip edge of the rupture these destructive events caused about 9000 fatalities and 23 000 injuries the overall rupture zone is about 170 km long and 40 80 km wide this region of the plate boundary previously experienced a large earthquake in 1833 and in 1934 a larger m s 8 0 event located to the east ruptured all the way to the surface the main himalayan thrust mht on which slip occurred in 2015 has a very low dip angle of 6 and the depth of the mainshock slip distribution is very shallow extending from 7 to 18 km the shallow dip and depth present challenges for resolving faulting characteristics using teleseismic data we analyze global teleseismic signals for the mainshock and aftershock to estimate source parameters evaluating the stability of various procedures used for remotely characterizing kinematics of such shallow faulting back projection and finite fault slip inversion are used to assess the spatio temporal rupture history and evidence for frequency dependent radiation along dip slip zone width constraints from near field geodetic observations are imposed on the preferred models to overcome some limitations of purely teleseismic methods radiated energy stress drop and moment rate functions are determined for both events

tectonic diffusion estimate of orogenic gold resources age frequency data are used to determine amounts of vertical tectonic displacement experienced by the global population of orogenic gold deposits following their emplacement at a crustal depth of 10 1 km knowledge of this tectonic dispersion allows for an estimate of the total crustal endowment of gold in orogenic gold deposits this estimate is based on a compilation of data on 365 orogenic gold deposits of which gold contents are available for 314 deposits and good age control is available for 126 deposits ages of well dated deposits form three clusters that range in age from 47 to 850 ma primarily phanerozoic 69 deposits 1730 to 2090 ma proterozoic 13 deposits and 2540 to 3107 ma archean 44 deposits gold endowments do not vary significantly among the three age groups and average 155 tonnes t per deposit for the entire population for which data on gold tonnages are available owing to the distinct tripartite nature of the age frequency distribution it is not possible that orogenic gold deposits represent largely invariant rates of ore formation and destruction uninterrupted tectonic dispersion would have resulted in the destruction of essentially all proterozoic and archean deposits separate tectonic diffusion calculations for each of the three deposit age populations were carried out while constraining biases to tectonic diffusion i e the most suitable ratios of uplift and erosion versus subsidence and burial with continental crustal thicknesses on the order of several tens of kilometers the results of these calculations indicated that a total of 25 236 orogenic gold deposits formed over the full span of geologic time that 23 664 of these 94 were destroyed during subsequent uplift and erosion and that 1 572 deposits remain at depth in earth s crust if all 365 known orogenic gold deposits have the same mean gold content as the deposits for which gold contents are available then 706 439 t of gold remain at depth in earth s crust gold in orogenic deposits constitutes about 0 0022 percent of the total gold content of the crust using estimates of gold released by prograde metamorphism of the otago schist gold in the deposits that remain in the crust could have been released from about 1 413 000 km3 of amphibolite facies rocks which constitute only about 12 percent of currently exposed metamorphic rocks if we assume a maximum depth of 3 km for future mining of these deposits the model results indicate that deposits containing almost 113 000 t of gold exist within crustal rocks above this depth discovered deposits make up about 8 percent of this endowment in the context of spatial density the areal concentration of orogenic gold deposits along phanerozoic metamorphic belts is about ten times that in proterozoic terranes and about three times higher than in archean belts this suggests that exploration for the next generation of orogenic gold deposits should be focused on phanerozoic terranes

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

duplex in the main himalayan thrust illuminated by aftershocks of the 2015 m w 7 8 gorkha earthquake in april 2015 the lower locked portion of the main himalayan thrust ruptured beneath nepal causing the disastrous mw 7 8 gorkha earthquake elucidating the enigmatic geometry of this plate boundary fault is important for understanding the nucleation and arrest of large earthquake ruptures as well as the seismic hazard topography and tectonics of the himalaya here we interpret the geometry of the main himalayan thrust from the spatial distribution and rupture patterns of a dynamic sequence of aftershocks following the gorkha earthquake which were recorded by a rapidly deployed dense seismic network we find that the thrust comprises two north dipping subhorizontal planes that are connected by a system of bounded imbricate thrust faults this structure is known as a duplex we propose that this duplex acts as an impediment to plate convergence and accommodates tectonic stress along its complex system of faults such a prominent structure to the main himalayan thrust is consistent with surface geological studies but challenges geophysically derived conventional models with simpler geometries the main himalayan thrust comprises two fault planes connected by imbricated faults a structure that impedes convergence according to an analysis of the distribution and orientation of aftershocks of the 2015 gorkha earthquake in nepal

uplift and convergence along the himalayan frontal thrust of india along the himalayan thrust front in northwestern india terrace deposits exposed 20 to 30 m above modern stream level are interpreted to have been uplifted by displacement on the underlying himalayan frontal thrust a radiocarbon age limits the age of the terrace to 1665 215 calendar bc 3663 215 radiocarbon years before present yielding a vertical uplift rate of 6 9 1 8 mm yr in combination with published studies constraining the dip of the himalayan frontal thrust fault to about 30 in the study area the observed uplift rate equates to horizontal shortening across the himalayan frontal thrust of 11 9 3 1 mm yr and the slip rate of the himalayan frontal thrust of 13 8 3 6 mm yr this is similar to previously reported rate estimates along the himalayan arc based on displacement of older plio miocene age rocks or the much shorter records of geodesy and historical seismicity the similarity is consistent with the idea that convergence across the himalayan front has occurred at a relatively steady rate through time the seismic expression of this deformation includes several great m 8 historical earthquakes which due to lack of surface rupture during those events have been attributed to their occurrence on blind thrusts yet the occurrence of a possible fault scarp in the field area indicates that past earthquakes have been sufficiently large to rupture to the surface and produce coseismic scarps these observations suggest a potential for earthquakes along the himalayan frontal thrust larger than those observed historically

observations on late pleistocene cooling and precipitation in the lowland neotropics although accurate reconstructions of amazonian palaeoclimates are central to under standing the distribution and history of neotropical biodiversity current reconstructions based on proxy data are discordant and subject to intense debate we review some current thinking in amazonian climatology and incorporate some new ideas in an attempt to explain the apparently con tradictory records of palaeoprecipitation from across the amazon basin we suggest that palaeoecol ogists need to recognise that organised convective radiation the process that induces most wet season rainfall in amazonia should be treated as a phenomenon related to but separate from the passage of the inter tropical convergence zone itcz decoupling itcz migration from larger con vective activity provides a mechanism to account for observed palaeoclimatic heterogeneity patterns of observed precipitation change are consistent with the long term persistence of closed forest across much of amazonia indicating that the greatest changes in precipitation during the last glacial max imum came during the wet season which would have little negative impact on forest extent neo tropical cooling at the last glacial maximum lgm is widely accepted although the estimates of that cooling range between 1 c and 5 c in answering the basic question what is meant by cooling we observe that interhemispheric ice mass asymmetry may have caused cooling to be manifested differently according to location a terrestrial cooling of ca 5 c as well as radiative cooling and event based cooling combined to induce vegetation change probably both absolute temperature and mean monthly minima were reduced by polar air incursions in the northern neotropics how ever in the southern neotropics mean monthly minima were reduced by more frequent incursions of patagonian air masses but absolute minima may have been largely unchanged copyright 2004 john wiley sons ltd

faulting structure above the main himalayan thrust as shown by relocated aftershocks of the 2015 mw7 8 gorkha nepal earthquake the 25 april 2015 m w 7 8 gorkha nepal earthquake ruptured a shallow section of the indian eurasian plate boundary by reverse faulting with nne ssw compression consistent with the direction of current indian eurasian continental collision the gorkha main shock and aftershocks were recorded by permanent global and regional arrays and by a temporary local broadband array near the china nepal border deployed prior to the gorkha main shock we relocate 272 earthquakes with m w 3 5 by applying a multiscale double difference earthquake relocation technique to arrival times of direct and depth phases recorded globally and locally we determine a well constrained depth of 18 5 km for the main shock hypocenter which places it on the main himalayan thrust mht many of the aftershocks at shallower depths illuminate faulting structure in the hanging wall with dip angles that are steeper than the mht this system of thrust faults of the lesser himalaya may accommodate most of the elastic strain of the himalayan orogeny

tilting history of the san manuel kalamazoo porphyry system southeastern arizona the laramide san manuel kalamazoo porphyry system of arizona has been pivotal in concepts of both extensional tectonics and alteration mineralization zoning this paper reexamines the tilting history in light of new work in the region and reinterprets the geometry of the deposit the porphyry mineralization occurs in and near an intrusion of laramide san manuel porphyry in precambrian oracle granite the area has an extremely complicated history of tertiary crustal extension and fanglomerate deposition but the blocks containing the two main fragments of the original orebody separated by the san manuel fault were involved in only the later parts of this history and are less tilted than other nearby blocks originally horizontal features of mid tertiary age are tilted about 30 degrees those of laramide age about 35 degrees and those of pre laramide age about 45 degrees to the northeast paleomagnetism of the porphyry intrusion itself suggests tilting of about 33 degrees the data thus suggest that postemplacement tilt of the laramide porphyry system was 30 degrees to 35 degrees and that virtually all of it was mid tertiary in age an earlier interpretation of greater tilt magnitude was apparently based in part on correlation with adjacent areas showing greater tilt magnitude as in the tar wash allochthon and in part on a choice of cross section that gives the impression of a nearly recumbent attitude however lowell9s sections are oriented along the strike of both the orebodies and the productive porphyry intrusion which are dipping tablo cylindroidal bodies ore forms a hollow envelope whose inner margin has an aspect ratio of about 4 3 length 2 5 downdip height l limb separation the productive intrusion around which ore is wrapped has a similar aspect ratio in the same plane strike n 58 degrees e dip 47 degrees se reconstruction of the original attitudes of intrusion and ore yields a common strike near n 759 e and a steep dip to the south this is a common attitude for undisturbed productive porphyry dikes of laramide age

crustal structure of mainland china from deep seismic sounding data abstract since 1958 about ninety seismic refraction wide angle reflection profiles with a cumulative length of more than sixty thousand kilometers have been completed in mainland china we summarize the results in the form of 1 a new contour map of crustal thickness 2 fourteen representative crustal seismic velocity depth columns for various tectonic units and 3 a pn velocity map we found a north south trending belt with a strong lateral gradient in crustal thickness in central china this belt divides china into an eastern region with a crustal thickness of 30 45 km and a western region with a thickness of 45 75 km the crust in these two regions has experienced different evolutionary processes and currently lies within distinct tectonic stress fields our compilation finds that there is a high velocity 7 1 7 4 km s layer in the lower crust of the stable tarim basin and ordos plateau however in young orogenic belts including parts of eastern china the tianshan and the tibetan plateau this layer is often absent one exception is southern tibet where the presence of a high velocity layer is related to the northward injection of the cold indian plate this high velocity layer is absent in northern tibet in orogenic belts there usually is a low velocity layer lvl in the crust but in stable regions this layer seldom exists the pn velocities in eastern china generally range from 7 9 to 8 1 km s and tend to be isotropic pn velocities in western china are more variable ranging from 7 7 to 8 2 km s and may display azimuthal anisotropy

extending resolution of fault slip with geodetic networks through optimal network design geodetic networks consisting of high precision and high rate global navigation satellite systems gnss stations continuously monitor seismically active regions of the world these networks measure surface displacements and the amount of geodetic strain accumulated in the region and give insight into the seismic potential sugar sumatra gps array in sumatra geonet gnss earth observation network system in japan and pbo plate boundary observatory in california are some examples of established networks around the world that are constantly expanding with the addition of new stations to improve the quality of measurements however installing new stations to existing networks is tedious and expensive therefore it is important to choose suitable locations for new stations to increase the precision obtained in measuring the geophysical parameters of interest here we describe a methodology to design optimal geodetic networks that augment the existing system and use it to investigate seismo tectonics at convergent and transform boundaries considering land based and seafloor geodesy the proposed network design optimization would be pivotal to better understand seismic and tsunami hazards around the world land based and seafloor networks can monitor fault slip around subduction zones with significant resolution but transform faults are more challenging to monitor due to their near vertical geometry

tropical rain forest and climate dynamics of the atlantic lowland southern brazil during the late quaternary palynological analysis of a core from the atlantic rain forest region in brazil provides unprecedented insight into late quaternary vegetational and climate dynamics within this southern tropical lowland the 576 cm long sediment core is from a former beach ridge valley located 3 km inland from the atlantic ocean radio carbon dates suggest that sediment deposition began prior to 35 000 14c yr b p between ca 37 500 and ca 27 500 14c yr b p and during the last glacial maximum lgm ca 27 500 to ca 14 500 14c yr b p the coastal rain forest was replaced by grassland and patches of cold adapted forest tropical trees such as alchornea moraceae urticaceae and arecaceae were almost completely absent during the lgm furthermore their distributions were shifted at least 750 km further north suggesting a cooling between 3 c and 7 c and a strengthening of antarctic cold fronts during full glacial times a depauperate tropical rain forest developed as part of a successional sequence after ca 12 300 14c yr b p there is no evidence that araucaria trees occurred in the atlantic lowland during glacial times the rain forest was disturbed by marine incursions during the early holocene period until ca 6100 14c yr b p as indicated by the presence of microforaminifera a closed atlantic rain forest then developed at the study site

the mechanism of partial rupture of a locked megathrust the role of fault morphology assessment of seismic hazard relies on estimates of how large an area of a tectonic fault could potentially rupture in a single earthquake vital information for these forecasts includes which areas of a fault are locked and how the fault is segmented much research has focused on exploring downdip limits to fault rupture from chemical and thermal boundaries and along strike barriers from subducted structural features yet we regularly see only partial rupture of fully locked fault patches that could have ruptured as a whole in a larger earthquake here we draw insight into this conundrum from the 25 april 2015 m w 7 8 gorkha nepal earthquake we invert geodetic data with a structural model of the main himalayan thrust in the region of kathmandu nepal showing that this event was generated by rupture of a decollement bounded on all sides by more steeply dipping ramps the morphological bounds explain why the event ruptured only a small piece of a large fully locked seismic gap we then use dynamic earthquake cycle modeling on the same fault geometry to reveal that such events are predicted by the physics depending on the earthquake history and the details of rupture dynamics however great earthquakes that rupture the entire seismogenic zone are also possible these insights from nepal should be applicable to understanding bounds on earthquake size on megathrusts worldwide

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

structure and shortening of the kangra and dehra dun reentrants sub himalaya india surface geology oil well seismic reflection and magnetostratigraphic data are integrated to evaluate the structural style and the shortening rate at the himalayan front sub himalaya of northwest india the sub himalaya between the main boundary thrust and the himalayan frontal fault is the primary surface expression of shortening between the himalaya and the indian plate at certain locations the himalayan frontal fault is a blind thrust beneath anticlines of siwalik tertiary molasse parallel to the himalayan orogen the main boundary thrust is sinuous so the width of the sub himalaya ranges from 30 to 80 km where the sub himalaya is narrow nahan salient tertiary rocks are exposed in imbricate thrust sheets where the sub himalaya is broad kangra and dehra dun reentrants alluvium fills wide synclinal valleys duns seismic reflection data reveal that surface anticlines form in association with south vergent thrusts that root in a decollement at the base of the tertiary section reflection profiles and well data also indicate that the basement lithology changes northward from precambrian crystalline rocks beneath the indo gangetic plains to precambrian and cambrian metasedimentary rocks beneath the sub himalaya the sub himalayan decollement dips 2 5 northward beneath the kangra reentrant but it is steeper 6 beneath the dehra dun reentrant the kangra and dehra dun reentrants display fault propagation folds having steep limbs in the north and fault propagation and fault bend folds that have gently north dipping limbs in the south a balanced cross section of the kangra reentrant shows that a minimum of 23 km shortening has occurred since 1 9 1 5 ma yielding a shortening rate of 14 2 mm yr shortening has occurred at a rate of 6 16 mm yr across the dehra dun reentrant these data are similar to other published shortening rates and indicate that approximately 25 of the total india eurasia convergence at this longitude is accommodated within the sub himalaya given continued convergence and the presence of overpressured wells in the kangra reentrant the region is likely at risk from moderate and or great earthquakes in the future

identifying active structures in the chitwan dun central nepal using longitudinal river profiles and sl index analysis abstract previous studies have identified a seismic gap that has not witnessed any surface rupture earthquakes in the last 200 500 years located in the central sub himalaya i e area around chitwan intermontane valley a higher rate of convergence in these parts poses a great threat of a surface rupturing earthquake in future recent analysis of the 2015 gorkha earthquake to the north of this region suggests that it failed to rupture the surface moreover the stress is suggested to have transferred towards south therefore the chitwan intermontane valley located in the sub himalaya of the central himalayan seismic gap is investigated in this study to identify the active structures the longitudinal profile of a river considered to be one of the important geomorphic markers is used in this study for the identification of the active structures the hack profile and stream length gradient index sl index is used to identify the anomalous segments of the rivers these anomalous reaches are verified in the field for the presence of structures geomorphology of the region also supports the presence of active reverse faults in the valley abrupt break in the continuity of the geomorphic units and its correlation with the knick points and high sl index values indicate presence of around nine active structures in the chitwan intermontane valley six new structures viz jharahi thrust jht belani thrust bt west chitwan thrust wct danda thrust dt central churia thrust 2 cct 2 and shaktikhor thrust st have been identified in this study whereas three previously mapped structures viz main boundary thrust mbt barakot fault bkf and central churia thrust cct are also found to be active during the quaternary holocene most of the newly identified structures appear to be splays of either the mbt or the cct these structures have displaced quaternary landforms within the valley and are potentially active the structures can get re activated during large magnitude earthquake events in future

evidence of a late glacial warming event and early holocene cooling in the southern brazilian coastal highlands a high resolution pollen record of the atlantic rain forest arf biome from the coastal serra do tabuleiro mountains of southern brazil documents an 11 960 yr history of vegetation and climate change a marked expansion of weinmannia into the grassland vegetation marks the latter part of the younger dryas reflecting warm and relatively wet conditions between 11 490 and 9110 cal yr bp grasslands became dominant again indicating a long cold and dry phase probably in response to the stronger influence of cold south atlantic seawater and to antarctic cold fronts between 9110 and 2640 cal yr bp four distinct phases with strong or moderate expansions of different arf biome taxa were recorded reflecting warmer and relatively dry conditions with changes in rainfall and length of the annual dry season after 2640 cal yr bp the modern arf biome became established with high amounts of ferns reflecting somewhat cooler and wetter conditions with a reduced annual dry season in particular after 1000 cal yr bp tree ferns increased reflecting wetter conditions with no dry season

evidence of a large triggered event in the nepal himalaya following the gorkha earthquake implications toward enhanced seismic hazard a dc double couple constrained multiple point source moment tensor inversion is performed on the band passed 0 008 0 10 hz displacement data of the 25 april mw 7 8 2015 nepal mainshock from 17 broadband stations in india our results reveal that the 25 april event strike 324 dip 14 rake 88 ruptured the north dipping main himalayan thrust mht at 16 km depth we modeled the coulomb failure stress changes cfs produced by the slip on the fault plane of the 25 april nepal mainshock a strong correlation with occurrences of aftershocks and regions of increased positive cfs is obtained below the aftershock zone of the 2015 nepal mainshock we notice that predicted cfs at 16 km depth show a positive coulomb stress of 0 06 mpa at the location of the 12 may 2015 event these small modeled stress changes can lead to trigger events if the crust is already near to failure but these small stresses can also advance the occurrence of future earthquakes the main finding of our cfs modeling implies that the 25 april event increased the coulomb stress changes by 0 06 mpa at 16 km depth below the site of the 12 may event and thus this event can be termed as triggered we propose that the seismic hazard in the himalaya is not only caused by the mainshock slip on the mht rather the occurrence of large triggered event on the mht can also enhance our understanding of the seismic hazard in the nepal himalaya

gps measurements from the ladakh himalaya india preliminary tests of plate like or continuous deformation in tibet observations of relative motion in a geodetic network in ladakh india and across southern tibet indicate slow shear on the karakorum fault rapid east west extension across the whole of southern tibet and constant arc normal convergence between india and southern tibet along the himalayan arc measurements of ten campaign style and six permanent sites with global positioning system gps precise geodesy provide these bounds on the style and rates of the large scale deformation in the tibet himalaya region divergence between sites at leh ladakh india and shiquanhe western tibet as well as slow relative motion among sites within the ladakh network limit right lateral slip parallel to the karakorum fault to only 3 4 5 mm yr this low rate concurs with a recent estimate of 3 4 mm yr for late holocene time but disagrees with the much higher rate of 30 35 mm yr that has been used to argue for plate like behavior of the tibetan plateau convergence between ladakh and the indian subcontinent at 18 8 3 mm yr at 224 17 1 differs little from estimates of convergence across the central segment of the himalaya finally lengthening of the baseline between leh ladakh and lhasa in southeastern tibet at 17 8 1 mm yr or between leh and bayi farther to the southeast at 18 3 mm yr is consistent with an extrapolation of rates of east west extension of the tibetan plateau based both on shorter gps baselines e g lhasa simikot and on diverging slip vectors of earthquakes in the himalaya we interpret these results to indicate that tibet behaves more like a fl uid than like a plate

millennial scale precipitation changes in southern brazil over the past 90 000 years 1 a u th dated 90 000 year long speleothem oxygen isotope record from southern brazil anti correlates remarkably with the cave calcite records from eastern china but positively correlates with the speleothem record from northeastern brazil suggesting an interhemispheric anti phasing of rainfall on both millennial and orbital timescales likely related to displacement in the mean position of the intertropical convergence zone and associated asymmetry in hadley circulation the phase relationships among these records are consistent with the hypothesis that abrupt climate events during the last glacial period are triggered by oceanic circulation changes in the high latitudes and enhanced by tropical feedbacks

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

slow tilt reversal of the lesser himalaya between 1862 and 1992 at 78 e and bounds to the southeast rupture of the 1905 kangra earthquake summary measurements between 1862 and 1992 of a 77 km long spirit levelling line that crosses the main frontal thrust of the himalaya near dehra dun 78 e reveal a slow reversal of tilt in the early part of the last century unperturbed by the destructive 1905 april 4 kangra earthquake 200 km to the northwest the lesser himalaya are inferred to be tilting currently to the northeast at 0 08 rad yr 1 with similar rate but opposite sign to their tilt in 1862 the absence of co seismic deformation near dehra dun in 1905 indicates that the kangra rupture terminated short of dehra dun consistent with a revised ms 7 8 estimate for the size of the kangra earthquake but inconsistent with previous analyses of the levelling data that interpret a large slope dependent systematic error as co seismic slip the reversal in tilt corresponds to a linear northeast down tilt acceleration of 0 0015 0 0004 rad yr 2

convergence across the northwest himalaya from gps measurements 1 horizontal velocities of 26 global positioning system gps stations in the northwest himalayan region provide new constraints on the partitioning of india eurasia convergence and elastic strain accumulation about the locked main frontal thrust mft the northwest striking karakorum fault slips at 11 4 mm yr and contributes to east west extension of southern tibet and westward motion of the northwest himalaya towards nanga parbat rather than playing a role in eastward extrusion of tibet crustal shortening across the himalaya occurs within a zone centered about 100 km north of the siwalik foothills and the mft model inversions of the gps data indicate that the mft is locked over a width of 100 km comparison with geologic mft slip rate estimates suggests that this zone is building up a slip deficit at a rate of 14 1 mm yr and will eventually fail in future great earthquakes

earth s copper resources estimated from tectonic diffusion of porphyry copper deposits improved estimates of global mineral endowments are relevant to issues ranging from strategic planning to global geochemical cycling we have used a time space model for the tectonic migration of porphyry copper deposits vertically through the crust to calculate earth s endowment of copper in mineral deposits the model relies only on knowledge of numbers and ages of porphyry copper deposits earth s most widespread and important source of copper in order to estimate numbers of eroded and preserved deposits in the crust model results indicate that 125 895 porphyry copper deposits were formed during phanerozoic time that only 47 789 of these remain at various crustal depths and that these contain 1 7 1011 tonnes t of copper assuming that other types of copper deposits behave similarly in the crust and have abundances proportional to their current global production yields an estimate of 3 1011 t for total global copper resources at all levels in earth s crust thus 0 25 of the copper in the crust has been concentrated into deposits through phanerozoic time and about two thirds of this has been recycled by uplift and erosion the amount of copper in deposits above 3 3 km a likely limit of future mining could supply current world mine production for 5500 yr thus quantifying the highly unusual and nonrenewable nature of mineral deposits

coseismic and early postseismic deformation due to the 25 april 2015 mw 7 8 gorkha nepal earthquake from insar and gps measurements analysis of interferometric synthetic aperture radar insar and global positioning system gps data reveals coseismic and early postseismic 4 88 days surface displacements associated with the 25 april 2015 mw 7 8 gorkha nepal earthquake the pattern of early postseismic surface uplift and subsidence is found to be opposite to that of the coseismic motion insar and gps data were jointly inverted for coseismic and postseismic slip on the main himalayan thrust mht we consider a complex ramp flat ramp flat subsurface structure of the mht with four connected fault planes dipping toward north from the main frontal thrust mft the inverted coseismic slip distribution follows an elliptical pattern extending east southeastward from the hypocenter with maximum amplitude of 5 7 m above the upper edge of the midcrustal ramp we infer early postseismic afterslip 4 16 days of 0 2 0 47 m toward downdip of the coseismic slip asperity and another patch with 0 1 0 2 m slip toward east the shallow portion of the mht toward south is found to have remained unruptured during the earthquake nor did it slip aseismically after the earthquake suggesting possibility of large events in the future

southern oscillation signal in south american palaeoclimatic data of the last 7000 years abstract during strong el nino events rainfall anomalies and changes in wind patterns are observed in different regions of south america along the central brazilian coast during the 1983 el nino year the frontal systems were blocked to the south provoking a reversal of the longshore sand transport long duration reversals of longshore transport were also recorded in holocene beach ridge terraces from the rio doce coastal plain this led to the formulation of a model relating these reversals of longshore transport to el nino like conditions el nino like conditions are past average climate situations that generate the same perturbations as the strong el nino events observed during the last decade they are likely to correspond to the long duration low phase of the southern oscillation to confirm this hypothesis we compared the holocene beach ridge record with other palaeoenvironmental records from regions where strong el nino events would have a substancial signal as well 1 water level fluctuations of lake titicaca 2 a pollen and sediment record in an eastern amazonian lake 3 changes of the rio xingu discharge in eastern amazonia and 4 variations of sand supply at the rio piura and rio chira outlets in the sechura desert the occurrences of el nino like conditions were numerous before 3900 3600 yr b p absent between 39003600 and 2800 2500 yr b p and infrequent after 2800 2500 yr b p

surface deformation in the region of the 1905 kangra mw 7 8 earthquake in the period 1846 2001 1 one century after the mw 7 8 kangra earthquake of 4 april 1905 we report weak constraints on its rupture parameters based on the remeasurement of historic triangulation points in the epicentral region the western corner of the 1905 rupture is constrained to within 20 km and its sw edge strikes n135 15w the down dip width of the rupture is inferred from the location of the interseismic locking line to have been less than 55 km scaling laws and revised msk intensities suggest an along arc rupture length of 100 km with uniform slip of 4 m because the earthquake ruptured 60 of the width of the plate boundary and released a fraction of the inferred slip deficit complacency about its re rupture in the distant future is unwarranted the kangra rupture could fail again today in a mw 7 5 earthquake 1 4 m of slip or as part of a much larger earthquake mw 8 6

dynamic triggering of small local earthquakes in the central himalaya we present the first observation of remote dynamic triggering of local micro earthquakes in central himalaya caused by the teleseismic waves from the 2007 m8 5 sumatra earthquake that occurs 4 500 km away we find small local earthquakes in the kumaon garhwal himalaya triggered by teleseismic long period surface waves interestingly an elevated level of seismicity persists for a week or so after the arrival of the teleseismic waves the teleseismic waves impart 9 kpa of peak dynamic stresses suggesting that the himalayan faults in this area are sensitive to small stress changes this heightened and protracted seismicity indicates that the transient dynamic stresses may have triggered a secondary process such as slow slip that may be responsible for the persistence of this earthquake sequence the region is thought to be close to a large damaging earthquake in the near future rajendran rajendran 2005 this study provides improved constraints on the factors controlling the earthquake cycle

a stalagmite record of changes in atmospheric circulation and soil processes in the brazilian subtropics during the late pleistocene we present a high resolution 116 000 year carbon stable isotope record from a stalagmite from southern brazil which has been precisely dated using the u series method evaluation of carbon and oxygen isotope ratios together with the speleothem growth history suggest that the carbon isotopic composition of the speleothem is primarily controlled by biogenic co2 supply from the soil which is in turn affected by temperature and secondarily rainfall amount thus the speleothem provides evidence of paleoenvironmental change in southern brazil during the last glacial period predominantly high d 13 c values and low stalagmite growth rates reflect persistent cool conditions during most of the glacial period in subtropical brazil this cooling is probably related to an intensified extratropical circulation with more frequent and intense cold surges reaching a maximum at approximately 19 ky b p this cooling tendency is interrupted during periods of high obliquity values within the full glacial period at 93 85 and 47 40 ky b p and after 19 ky b p when a dramatic decrease in d 13 c marks the deglaciation time in the continent unlike d 18 o the d 13 c record does not exhibit a strong response to precessional forcing instead it shows a strong 40 ky obliquity signal here we propose that local temperature and thus the biological processes in the soil are primarily steered by the gradients of temperature between low and mid high latitudes which influence the meridional heat transport these gradient changes in turn are paced by obliquity r 2006 published by elsevier ltd

seismology raising kathmandu on 25 april 2015 northern nepal shifted up to 7 m southward and kathmandu was raised by 1 m the causal earthquake failed to fully rupture the main fault beneath the himalaya and hence a large earthquake appears to be inevitable in nepal s future

thermochronology of economic mineral deposits dating the stages of mineralization at panasqueira portugal by high precision 40 39 ar age spectrum techniques on muscovite 40 ar 39 ar age spectrum dates for 13 muscovites have been used to reconstruct the thermal history thermochronology of the panasqueira portugal tin tungsten deposit a deposit spatially associated with a belt of hercynian plutons muscovite samples with an age difference as small as 2 2 m y 0 7 of the age are statistically distinct statistics are even better for comparison of multiple samples from separate events that is a difference of 0 9 m y 0 3 can be resolved in this approximately 300 m y old deposit the major tin and tungsten ore forming stages which are the oxide silicate stage the main sulfide stage and greisenization occurred between 296 3 or 0 8 1 sigma and 291 6 or 0 8 m y 1 sigma the first substage of the oxide silicate stage was a short lived thermal pulse at 296 3 or 0 6 m y the fluids responsible may have emanated from the known granite cupola the main sulfide stage was active at 294 5 or 0 9 m y as a slightly longer lived pulse with oldest evidence for this stage 295 8 or 0 6 m y coming from areas farthest away from the known cupola and youngest evidence 293 5 or 0 8 m y closest to the cupola a second substage of the oxide silicate stage occurred as a short lived thermal pulse at 292 9 or 0 7 m y synchronous with greisenization of the cupola and alteration of the silica cap at 292 1 or 0 4 m y the duration of activity of the oxide silicate stage the main sulfide stage greisenization and alteration of the silica cap based on the ages of all 13 muscovites was greater than 4 2 or 0 5 m y 1 sigma minor argon loss from all dated muscovites occurred during later reheating probably during the longer lived pyrrhotite alteration stage a single center the known cupola had a prolonged role and was the source for main sulfide stage oxide silicate stage ii greisenization and alteration of the silica cap and possibly oxide silicate stage i and the pyrrhotite alteration stage however a separate source for these latter two stages cannot be ruled out this study is an example of a new and powerful application of 40 ar 39 ar age spectrum dating of muscovite because of the high precision demonstrated in this study it is now possible to establish time constraints necessary for solving some of the long standing problems in economic geology beyond this the unique geologic situation of panasqueira has allowed us to quantify the thermal characteristics of muscovite published fluid inclusion data have been used to estimate a muscovite argon closure temperature of approximately 325 degrees c during rapid cooling or short reheating and a temperature of approximately 270 degrees c during slow cooling or extended reheating argon loss patterns displayed by all dated muscovites resulted from reheating after original closure the mechanism for this argon loss appears to have been argon transport by volume diffusion thus 40 ar 39 ar age spectrum dating of muscovite can be used to evaluate thermal conditions controlling argon diffusion as well as age duration and number of episodes of mineralization

plateau pop up in the great 1897 assam earthquake the great assam earthquake of 12 june 1897 reduced to rubble all masonry buildings within a region of northeastern india roughly the size of england and was felt over an area exceeding that of the great 1755 lisbon earthquake1 hitherto it was believed that rupture occurred on a north dipping himalayan thrust fault propagating south of bhutan2 3 4 5 but here we show that the northern edge of the shillong plateau rose violently by at least 11 m during the assam earthquake and that this was due to the rupture of a buried reverse fault approximately 110 km in length and dipping steeply away from the himalaya the stress drop implied by the rupture geometry and the prodigious fault slip of 18 7 m explains epicentral accelerations observed to exceed 1g vertically and surface velocities exceeding 3 m s 1 ref 1 this quantitative observation of active deformation of a pop up structure confirms that faults bounding such structures can penetrate the whole crust plateau uplift in the past 2 5 million years has caused the indian plate to contract locally by 4 2 mm yr 1 reducing seismic risk in bhutan but increasing the risk in northern bangladesh

south and southeast brazilian grasslands during late quaternary times a synthesis fourteen pollen records from the south s and the southeast se brazilian regions have been synthesised late glacial records from s brazilian highlands document the predominance of grassland campos where today araucaria forests occur records from se brazil show that during pre and full glacial times modern tropical semideciduous forest and cerrado savanna to dry forest were mostly replaced by grassland and some subtropical gallery forest modern montane araucaria forests and cloud forests in se brazil were mostly replaced by grassland during pre and full glacial times there is evidence that the modern tropical atlantic rainforest in s brazil was significantly reduced and replaced by cold adapted forest taxa or grassland during glacial especially during full glacial times the synthesis indicates that grasslands dominated the s and se brazilian landscape during the late pleistocene where today different forest ecosystems exist grassland extended over 750 km from s to se brazil from latitudes of about 28 27 s to at least 20 s these results indicate that climates in the region were markedly drier and 5 7 c cooler during glacial times antarctic cold fronts must have been much stronger and more frequent than today studies from s brazil show that huge areas of late pleistocene campos vegetation were still found on the s brazilian highlands during early and mid holocene times reflecting dry climatic conditions with an annual dry period of probably 3 months modern wet climatic conditions with no or only short dry periods were not established until the late holocene period when araucaria forests replaced large areas of grassland vegetation after about 3000 14c yr b p and especially after 1500 1000 14c yr b p

paleoseismological evidence of surface faulting along the northeastern himalayan front india timing size and spatial extent of great earthquakes the similar to 2500 km long himalayan arc has experienced three large to great earthquakes of m w 7 8 to 8 4 during the past century but none produced surface rupture paleoseismic studies have been conducted during the last decade to begin understanding the timing size rupture extent return period and mechanics of the faulting associated with the occurrence of large surface rupturing earthquakes along the similar to 2500 km long himalayan frontal thrust hft system of india and nepal the previous studies have been limited to about nine sites along the western two thirds of the hft extending through northwest india and along the southern border of nepal we present here the results of paleoseismic investigations at three additional sites further to the northeast along the hft within the indian states of west bengal and assam the three sites reside between the meizoseismal areas of the 1934 bihar nepal and 1950 assam earthquakes the two westernmost of the sites near the village of chalsa and near the nameri tiger preserve show that offsets during the last surface rupture event were at minimum of about 14 m and 12 m respectively limits on the ages of surface rupture at chalsa site a and nameri site b though broad allow the possibility that the two sites record the same great historical rupture reported in nepal around a d 1100 the correlation between the two sites is supported by the observation that the large displacements as recorded at chalsa and nameri would most likely be associated with rupture lengths of hundreds of kilometers or more and are on the same order as reported for a surface rupture earthquake reported in nepal around a d 1100 assuming the offsets observed at chalsa and nameri occurred synchronously with reported offsets in nepal the rupture length of the event would approach 700 to 800 km the easternmost site is located within harmutty tea estate site c at the edges of the 1950 assam earthquake meizoseismal area here the most recent event offset is relatively much smaller 2 5 m and radiocarbon dating shows it to have occurred after a d 1100 after about a d 1270 the location of the site near the edge of the meizoseismal region of the 1950 assam earthquake and the relatively lesser offset allows speculation that the displacement records the 1950 m w 8 4 assam earthquake scatter in radiocarbon ages on detrital charcoal has not resulted in a firm bracket on the timing of events observed in the trenches nonetheless the observations collected here when taken together suggest that the largest of thrust earthquakes along the himalayan arc have rupture lengths and displacements of similar scale to the largest that have occurred historically along the world s subduction zones

ore deposits in an evolving earth an introduction ore deposits form by a variety of natural processes that concentrate elements into a small volume that can be economically mined their type character and abundance reflect the environment in which they formed and thus they preserve key evidence for the evolution of magmatic and tectonic processes the state of the atmosphere and hydrosphere and the evolution of life over geological time this volume presents 13 papers on topical subjects in ore deposit research viewed in the context of earth evolution these diverse yet interlinked papers cover topics including controls on the temporal and spatial distribution of ore deposits the sources of fluid gold and other components in orogenic gold deposits the degree of oxygenation in the neoproterozoic ocean bacterial immobilization of gold in the semi arid near surface environment and mineral resources for the future including issues of resource estimation sustainability of supply and the criticality of certain elements to society

quantitative identification of metallogenic epochs and provinces application to phanerozoic porphyry copper deposits the terms metallogenic epoch and metallogenic province have been widely used for many years but are so poorly defined that most of earth s surface and geologic history has been designated a metallogenic feature of some sort we propose defining metallogenic epoch and metallogenic province as those time intervals of earth history and regions of earth respectively which contain a significantly greater number of deposits or larger tonnage of a specific deposit type than would have resulted from average rates of mineralization that have occurred over phanerozoic time here we evaluate the application of this definition to porphyry copper deposits metallogenic epochs for porphyry copper deposits can be identified by comparison between a real earth age frequency distribution based on ages of known deposits and a model age frequency distribution that simulates the formation of porphyry copper deposits and their subsequent vertical uplift and or subsidence relative to the earth s surface after they form the latter represents the age frequency distribution that would be expected if rates of mineralization did not deviate from the phanerozoic average and is determined by least squared minimization of differences between model and real earth age frequency values metallogenic epochs are defined as duration normalized time periods in which real earth numbers or sizes of deposits differ significantly from the model value of average numbers or sizes of deposits that have formed over the past 545 m y of earth history eight of the 80 phanerozoic stages constituting 5 5 percent of this time interval meet this definition these include the upper eocene paleocene all 3 stages lower triassic middle pennsylvanian upper silurian and upper ordovician metallogenically impoverished stages occurred during the upper cretaceous and the upper oligocene time intervals of deposit enrichment and scarcity exhibit little correlation with records of widely known global geologic features or processes at a more regional scale however mineralization along south and central america slightly postdated times of enhanced production of east pacific sea floor and many paleocene deposits underwent enhanced preservation beneath younger rocks metallogenic provinces appear to be recognizable through use of the power law relationship between the duration normalized spatial density of real earth deposits and the size of areas that host the deposits comparison of real earth spatial densities to a best fit line to data for all areas containing deposits allows recognition of areas that have greater spatial densities our analysis suggests that variation in the distribution of porphyry copper deposits in both time and space are largely unpredictable at even epoch and regional scales of consideration respectively and indicate that the presence or absence of deposits in one time interval or region does not effectively predict the abundance of other deposits in other time intervals or geographic localities this conclusion however does not preclude the importance of geologic controls on either deposits or metallogenic features rather it strongly affirms the widely accepted fact that the distribution of ore deposits and metallogenic features is due to a large number of geologic factors and processes that vary from place to place and time to time more rigorous definition of metallogenic epochs and provinces and more detailed geologic study at the local scale will lead to a better understanding of those processes that account for statistically anomalous concentrations of mineralization in both time and space

implications for elastic energy storage in the himalaya from the gorkha 2015 earthquake and other incomplete ruptures of the main himalayan thrust abstract rupture in the 2015 m7 8 gorkha earthquake nucleated at the downdip edge of the main himalayan thrust mht near the transition from interseismic locking to aseismic creep beneath the tibetan plateau and propagated incompletely towards the main frontal thrusts mft despite the imposition of a substantial static strain in the mid decollement afterslip on the mht within a year of the earthquake had decayed to negligible levels earthquakes that incompletely rupture the mht 7

abrupt changes in high latitude nutrient supply to the atlantic during the last glacial cycle the supply of nutrients to the low latitude thermocline is largely controlled by intermediate depth waters formed at the surface in the high southern latitudes silicic acid is an essential macronutrient for diatoms which are responsible for a significant portion of marine carbon export production changes in ocean circulation such as those observed during the last deglaciation would influence the nutrient composition of the thermocline and therefore the relative abundance of diatoms in the low latitudes here we present the first record of the silicic acid content of the atlantic over the last glacial cycle our results show that at intermediate depths of the south atlantic the silicic acid concentration was the same at the lgm as it is today overprinted by high silicic acid pulses that coincided with abrupt changes in ocean and atmospheric circulation during heinrich stadials and the younger dryas we suggest these pulses were caused by changes in intermediate water formation resulting from shifts in the subpolar hydrological cycle with fundamental implications for the nutrient supply to the atlantic

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

related changes in biodiversity insolation and climate in the atlantic rainforest since the last interglacial abstract the long term colonia record is located in the atlantic rainforest domain in brazil 23 52 s 46 42 20 w 900 m a s l the 780 cm long core co3 provides a coverage of a complete interglacial glacial cycle for the first time in a neotropical rainforest information on the behavior of tropical climates compared to global changes in temperatures indicates specific climate responses in terms of precipitation at these latitudes winter extratropical circulation was very active during the last interglacial and most of the glacial floristic composition of the rainforest changed several times in each phase of expansion twice during the interglacial and three times during glacial episodes araucaria was well developed in the area of sao paulo until the beginning of the first dry phase of the glacial at ca 50 000 yr b p changes in insolation controlled the expansion of the rainforest and the tropical hydrological cycle as evidenced by a strong precession signal however precession had no impact on regional climatic features the two interglacials mis 5e and holocene showed completely different patterns attesting to the continuous evolution of the forest the biodiversity index shannon wiener index remained high during both the interglacial and glacial attesting to the permanence of small patches of rainforest refugia during drier phases the lowest shannon wiener indexes were recorded between 23 000 and 12 000 yr b p and 40 000 and 30 000 yr b p and characterize two marked phases of stress for the rainforest

upper pleistocene to holocene peatland evolution in southern brazilian highlands as depicted by radar stratigraphy sedimentology and palynology paleoenvironmental interpretation of proxy data derived from peatlands is largely based upon an evolutionary model for ombrotrophic bogs in which peat accumulates in still environments reports on proxies obtained from minerotrophic fens where hydrologic inputs are variable are less common in this study a highland peatland in southern brazil is presented through ground penetrating radar gpr and sedimentological palynological and geochronologic data the radar stratigraphic interpretation suggests a relatively complex history of erosion and deposition at the site since the beginning of marine isotope stage 3 mis 3 interstadial period in spite of this radar stratigraphic and palynologic interpretations converge electromagnetic reflections tend to group in clusters that show lateral coherence and correlate with different sediment types while pollen grains abound and are well preserved as a result the study of minerotrophic fens provides a source of proxies suggesting that ombrotrophic bogs are not the only reliable source of data in wetlands for palynological analysis

late quaternary araucaria forest grassland campos fire and climate dynamics studied by high resolution pollen charcoal and multivariate analysis of the cambara do sul core in southern brazil abstract late quaternary vegetation fire and climate dynamics have been studied based on high resolution dated pollen and charcoal samples and multivariate data analysis the samples were taken from a 212 cm long sediment core of a bog in the cambara do sul region on the highlands of northeastern rio grande do sul state brazil the records including seven ams radiocarbon dates span 42 840 14c years for the first time extending the reconstruction of past environmental changes on the southern brazilian highlands back to the last glacial maximum lgm and pre lgm times the last 1100 years provide a decadal resolution initially the site was a permanent shallow lake which became seasonally dry after 26 900 14c yr bp seasonal climate with a long annual dry period prevailed until the late holocene the climate was somewhat wetter from 42 840 to 41 470 14c yr bp and from 41 470 to 26 900 14c yr bp than during the lgm and the late glacial period natural fires were rare but became very frequent after 7400 cal bp suggesting human occupation of the southernmost brazilian highlands since that time the records suggest that a species rich campos grassland vegetation existed in the area under a relatively dry and cold climate during glacial times under possibly as low as 10 c the record also suggests that small populations of araucaria were probably only present in refugia of deep and protected valleys and or on wetter coastal slopes campos vegetation existed through the early and mid holocene until 4320 cal yr bp after which araucaria forest expanded into the network of gallery forests along the streams by 1100 cal yr bp the araucaria forest replaced the campos vegetation reflecting the onset of the wettest period with no marked annual dry season the marked expansion of the araucaria forest coincided with the reduction in fire between ad 1520 and 1770 weinmannia became a common taxa in the araucaria forest suggesting a shift to warmer climatic conditions on the highlands this interval was synchronous with a cool phase within the little ice age known from north atlantic land records after about ad 1780 human activities changed the original forest composition first by introducing cattle into the forest and than by selective logging of araucaria trees multivariate analysis of the pollen data shows compositional changes that follow a trajectory alternating undirectional random phases and phases with directional sometimes fast transitions the results also show that compositional changes in the vegetation are slower during cool periods lgm compared to pre lgm and faster in warm periods holocene

probabilistic seismic hazard assessment for himalayan tibetan region from historical and instrumental earthquake catalogs the himalayan tibetan region has a long history of devastating earthquakes with wide spread casualties and socio economic damages here we conduct the probabilistic seismic hazard analysis by incorporating the incomplete historical earthquake records along with the instrumental earthquake catalogs for the himalayan tibetan region historical earthquake records back to more than 1000 years ago and an updated homogenized and declustered instrumental earthquake catalog since 1906 are utilized the essential seismicity parameters namely the mean seismicity rate the gutenberg richter b value and the maximum expected magnitude m max are estimated using the maximum likelihood algorithm assuming the incompleteness of the catalog to compute the hazard value three seismogenic source models smoothed gridded linear and areal sources and two sets of ground motion prediction equations are combined by means of a logic tree on accounting the epistemic uncertainties the peak ground acceleration pga and spectral acceleration sa at 0 2 and 1 0 s are predicted for 2 and 10 probabilities of exceedance over 50 years assuming bedrock condition the resulting pga and sa maps show a significant spatio temporal variation in the hazard values in general hazard value is found to be much higher than the previous studies for regions where great earthquakes have actually occurred the use of the historical and instrumental earthquake catalogs in combination of multiple seismogenic source models provides better seismic hazard constraints for the himalayan tibetan region

block and fault dynamics modelling of the himalayan frontal arc implications for seismic cycle slip deficit and great earthquakes abstract a numerical block and fault dynamics model bafd of the himalayan frontal arc india is developed to understand the long term patterns of strain accumulation and occurrences of great earthquakes in the himalaya the morphostructural scheme outlines twelve major crustal blocks and external driving motions are prescribed using gps data the bafd model reproduces essential features of the geodynamics and seismicity of the himalayan frontal arc the locations of the large synthetic earthquakes and their maximum magnitudes are consistent with the information available from the instrumental and historical earthquake catalogues we model the evolution of the slip deficit and seismic cycles for different sections across the himalaya frontal arc the modelled seismic cycles are found to be varying from 700 to 2100 years and are in good agreement with the return periods estimates from the recent paleoseismological studies we notice that the accumulation of the slip deficit depends not only on the rate of shortening rheology and structure but also on the dynamics of the confining crustal blocks further we observe that tectonic motions of the shillong plateau and assam basin microplates play a significant role in controlling the seismicity patterns of the bhutan block which resulted in the decreased seismic activity and increased rate of aseismic displacement thus we infer that the regional seismicity patterns are a consequence of dynamics of the entire regional fault and block system rather than dynamics of individual fault our bafd modelling predicts the maximum earthquake hazard associated with future large great earthquakes for the central himalayan gap region which lies between the 1905 kangra and the 2015 gorkha earthquake ruptures but relatively less hazard in kashmir and assam

isoseismal map of the 2015 nepal earthquake and its relationships with ground motion parameters distance and magnitude abstract a devastating earthquake of mw 7 8 struck central nepal on 25th april 2015 6 11 25 ut which resulted in more than 9000 deaths and destroyed millions of houses standing buildings roads and electrical installations worth 25 30 billions of dollars are reduced to rubbles the earthquake was widely felt in the northern parts of india and moderate damage have been observed in the northern part of up and bihar region of india maximum intensity ix according to the usgs report was observed in the meizoseismal zone surrounding the kathmandu region in the present study we have compiled available information from the print electronic media and various reports of damages and other effects caused by the event and interpreted them to obtain modified mercalli intensities mmi at over 175 locations spread over nepal and surrounding indian and tibet region we have also obtained a number of strong motion recordings from india and nepal seismic network and developed an empirical relationship between the mmi and peak ground acceleration pga peak ground velocity pgv we have used least square regression technique to derive the empirical relation between the mmi and ground motion parameters and compared them with the empirical relationships available for other regions of the world further seismic intensity information available for historical earthquakes which have occurred in the nepal himalaya along with the present intensity data has been utilized for developing an attenuation relationship for the studied region using two step regression analyses the derived attenuation relationship is useful for assessing damage of a potential future large earthquake earthquake scenario based planning purposes in the region

a fractal approach to the relationship between ore grade and tonnage it is now recognized that a variety of natural processes exhibit scale invariance over a wide range of scales scale invariant processes often exhibit a fractal behavior there are various ways to define fractal behavior one is to relate the frequency of occurrence to size tonnage and grade relations for economic ore deposits exhibit a fractal behavior if the tonnage of ore with a mean grade is proportional to the mean grade raised to a power we show that such a relation is a good approximation for mercury copper and uranium deposits in the united states the respective fractal dimensions are 2 01 1 16 and 1 48 the renormalization group approach is a quantitative method for studying scale invariant processes if it is assumed that the concentration of elements in ores is statistically scale invariant the renormalization group approach can be used to derive a fractal relationship between tonnage and mean grade

evidence of rainfall variations in southern brazil from trace element ratios mg ca and sr ca in a late pleistocene stalagmite trace element ratios in the bt2 stalagmite from botuveracave southern brazil are explored as a proxy for changes in the local rainfall recharge during the last 116 ky bp mg ca and sr ca ratios measured with an electron microprobe are signif icantly positively correlated with one another throughout the entire record and vary in a way that is very consistent with variations of d 18 o in the same speleothem during the last glacial period we suggest that prior calcite precipitation in the vadose zone of the cave system is the main factor affecting the incorporation of mg and sr into calcite of the stalagmite this interpretation is supported by trace element correlation patterns and by results from a hydrochemistry study performed in a cave located in the same region and in a similar environmental setting therefore we conclude that higher lower mg ca and sr ca values are associated with lower higher levels of recharge into the karstic aquifer as such conditions lead to an increase decrease in the volume of calcite precipitated in the unsaturated zone above the cave during dry wet climate periods trace element variations point to generally dryer wetter conditions during lower high phases of summer insolation in the southern hemisphere these periods coincide with decreased increased activity of the south american summer monsoon as revealed by d 18 o stalagmite records in addition trace element variations show that rather wet conditions persisted through out most of the last glacial period from approximately 70 to 17 ky bp we suggest that during this period the glacial boundary conditions especially ice volume buildup in the northern hemisphere played an important role for monsoon rainfall inten sification in the region 2007 elsevier ltd all rights reserved

characteristic ground motions of the 25th april 2015 nepal earthquake mw 7 9 and its implications for the structural design codes for the border areas of india to nepal abstract the 25th april 2015 nepal earthquake was found associated with a series of aftershocks and the mainshock rupture propagated predominantly towards se direction where a major aftershock mw 7 3 rocked on 12th may 2015 to the east of the mainshock that enhanced the rate of occurrence of aftershocks in the affected region we conducted a rigorous analysis of strong motion data to understand the characteristics of ground motion and their bearing on the structural design codes responsible for the damage to the structures in the border area of india to nepal the effect of ground geology on the acceleration response spectra are also evaluated using main shock and its associated strong earthquakes all the sites used in the present analysis are located on alluvium deposits showing a predominant period of 0 242 sec for horizontal components and at 0 193 sec for vertical components our results demonstrated that observed peak ground acceleration pga has prominent distribution in the border cities of up and bihar pga ranges from 3 to 80 cm sec 2 in the study region for the epicentral distance varying from 120 km to 495 km with respect to the source zone mainshock the peak ground velocity pgv varies from 1 to 16 cm sec while the peak ground displacement pgd lies in between 1 cm and 20 cm for the same area our study shows that variation of pgd pgv and pga are controlled and dictated by the geo morphological constraints besides the nature and extent of structural heterogeneities of the sub surface geological formation materials the obtained normalised spectral amplifications are compared with the bureau of indian standard code for construction of buildings which shows that the current indian building design code is within the structural limits proposed for the seismic forces at all periods for alluvium sites suggesting that the structural heterogeneity has the strong role contributing towards the intrinsic attenuation in the seismic wave propagating medium our analysis also shows a good correspondence with the nonlinearity of the seismic waves which in turn controls the degree of damage in an area we infer that extent of damage to the structures in the border cities of india vicinity to the rupture zone can be avoided if the existing building design code could have been implemented as the earthquake risk resilient mitigation plan

estimating the return times of great himalayan earthquakes in eastern nepal evidence from the patu and bardibas strands of the main frontal thrust the return times of large himalayan earthquakes are poorly constrained despite historical devastation of cities along the mountain range definitive links between events and specific segments of the main frontal thrust mft are not established and paleoseismological records have not documented the occurrence of several similar events at the same location in east central nepal however recently discovered primary surface ruptures of that megathrust in the a d 1255 and 1934 earthquakes are associated with flights of tectonically uplifted terraces we present here a refined longer slip history of the mft s two overlapping strands patu and bardibas thrusts in that region based on updated geomorphic neotectonic mapping of active faulting two 1 3 km long shallow seismic profiles and logging of two river cut cliffs three paleoseismological trenches and several pits with constraints from 74 detrital charcoals and 14 cosmogenic nuclide ages the amount of hanging wall uplift on the patu thrust since 3650 450 years requires three more events than the two aforementioned the uplift rate 8 5 1 5mm yr thrust dip 25 5 n and apparent characteristic behavior imply 12 17 5m of slip per event on the bardibas thrust discrete pulses of colluvial deposition resulting from the coseismic growth of a flexural fold scarp suggest the occurrence of six or seven paleo earthquakes in the last 4500 50 years the coeval rupture of both strands during great himalayan earthquakes implies that in eastern nepal the late holocene return times of such earthquakes probably ranged between 750 140 and 870 350 years

using geodetic data to calculate stress changes on faults in the tibetan plateau caused by the 2015 mw7 8 nepal earthquake abstract the 2015 m w 7 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 0 kpa 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 100 kpa 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

source characteristics of the 2015 m w 7 8 gorkha nepal earthquake and its m w 7 2 aftershock from space geodesy abstract on april 25 2015 a destructive m w 7 8 earthquake struck the capital of nepal kathmandu killing more than 8800 people and destroying numerous historical structures we analyze six coseismic interferograms from several satellites alos 2 sentinel 1 a and radarsat 2 as well as three dimensional displacements at six gps stations to investigate fault structure and slip distribution of the gorkha earthquake using a layered crustal structure the best fit slip model shows that the preferred dip angle of the mainshock fault is 6 3 5 and the major slip is concentrated within depths of 8 15 km the maximum slip of 6 0 m occurs at a depth of 11 km 70 km south east of the epicenter the coseismic rupture extends 150 km eastward of the epicentre with a cumulative geodetic moment of 7 8 10 20 nm equivalent to an earthquake of m w 7 84 we also investigate the m w 7 2 aftershock on 12 may 2015 using another three postseismic interferograms from alos2 radarsat 2 and sentinel 1 a the insar based best fit slip model of the largest aftershock implies that its major slip is next to the eastern lower end of the mainshock rupture with a similar maximum slip of 6 m at a depth of 13 km this study generates various coseismic geodetic measurements to determine the source parameters of the m w 7 8 gorkha earthquake and 12 may m w 7 2 afershock providing an additional chance to understand the local fault structure and slip extent

seismotectonics and seismogenesis of mw7 8 gorkha earthquake and its aftershocks abstract the april 25 2015 mw7 8 gorkha earthquake in central nepal was followed by intense aftershock activity including mw6 7 shock on april 26 2015 and mw7 3 shock on may 12 2015 synthesis of the focal mechanisms space time distribution of seismic activity in relation to previously imaged crustal velocity and resistivity structures reveals focusing of the mw7 8 gorkha earthquake near the upper surface of the thin fluid filled low velocity and high conducting layer immediately above the plane of the detachment on the geophysical sections the detachment is identified as a sharp positive velocity interface modulation of frictional coupling and mechanical weakening by high pore pressure fluids counteract the arc normal stresses creating conditions for failure and nucleation of the gorkha earthquakes on a plane sub parallel with the detachment spatio temporal patterns in aftershock activity indicate rapid alteration of main shock induced stress fields triggering a strong aftershock of mw6 7 large stress drop and increased energy released by the mw6 7 event facilitates upward injection of high pore pressure fluid fluxes into the hidden out of sequence thrust it is suggested that decrease in shear strength along the hidden thrust plane due to the diffusion of high pore pressure fluids created conditions favourable to trigger mw7 3 aftershock

no major active backthrust bounds the pir panjal range near kashmir basin nw himalaya abstract this research disputes the geomorphic data presented in dar et al 2014 and demonstrates that their data strongly conflicts with their own field evidence and also with the previous geological observations the authors have proposed a major sw dipping frontal fault that bounds the pir panjal range near kashmir basin of nw himalaya however field photographs show a very steep 86 dipping normal fault this therefore contradicts with all the morphometric indices interpretations and discussion presented because those are based on a major se dipping thrust fault that bounds pir panjal range in kashmir basin the proposed fault is a major sw dipping backthrust which primarily conflicts with the previous geological observations in kashmir basin because mostly ne dipping major thrusts are mapped in this region and presently only three major ne dipping faults the main frontal thrust mft the raisi fault rf and the kashmir basin fault kbf are tectonically active the new proposed major active thrust as suggested by the triangular facets mapped by dar et al 2014 was mapped on the basis of geomorphic evidence as a sw dipping thrust fault and field evidence shows a normal fault which utterly questions the nature and significance of the new research work

orbitally driven east west antiphasing of south american precipitation the variations of tropical precipitation are antiphased between the hemispheres on orbital timescales a comparison between a speleothem record of precipitation in northeast brazil and rainfall reconstructions from the rest of tropical south america shows that a similar antiphasing operated in the same hemisphere during the holocene the variations of tropical precipitation are antiphased between the hemispheres on orbital timescales this antiphasing arises through the alternating strength of incoming solar radiation in the two hemispheres which affects monsoon intensity and hence the position of the meridional atmospheric circulation of the hadley cells1 2 3 4 here we compare an oxygen isotopic record recovered from a speleothem from northeast brazil for the past 26 000 years with existing reconstructions of precipitation in tropical south america5 6 7 8 during the holocene we identify a similar but zonally oriented antiphasing of precipitation within the same hemisphere northeast brazil experiences humid conditions during low summer insolation and aridity when summer insolation is high whereas the rest of southern tropical south america shows opposite characteristics simulations with a general circulation model that incorporates isotopic variations support this pattern as well as the link to insolation driven monsoon activity our results suggest that convective heating over tropical south america and associated adjustments in large scale subsidence over northeast brazil lead to a remote forcing of the south american monsoon which determines most of the precipitation changes in the region on orbital timescales

interaction of the south american monsoon system and the southern westerly wind belt during the last 14 kyr abstract surface currents and sediment distribution of the se south american upper continental margin are under the influence of the south american monsoon system sams and the southern westerly wind belt swwb both climatic systems determine the meridional position of the subtropical shelf front stsf and probably also of the brazil malvinas confluence bmc we reconstruct the changing impact of the sams and the swwb on sediment composition at the upper rio grande cone off southern brazil during the last 14 cal kyr bp combining sedimentological geochemical micropaleontological and rock magnetic proxies of marine sediment core geob 6211 2 sharp reciprocal changes in ferri and paramagnetic mineral content and prominent grain size shifts give strong clues to systematic source changes and transport modes of these mostly terrigenous sediments our interpretations support the assumption that the sams over se south america was weaker than today during most of the late glacial and entire early holocene while the swwb was contracted to more southern latitudes resembling modern austral summer like conditions in consequence the stsf and the bmc were driven to more southern positions than today s favoring the deposition of fe rich but weakly magnetic la plata river silts at the rio grande cone during the mid holocene the northern boundary of the swwb migrated northward while the stsf reached its northernmost position of the last 14 cal kyr bp and the bmc most likely arrived at its modern position this shift enabled the transport of antarctic diatoms and more strongly magnetic argentinean shelf sands to the rio grande cone while sediment contributions from the la plata river became less important during the late holocene the modern el nino southern oscillation set in and the sams and the austral tradewinds intensified causing a southward shift of the stsf to its modern position this reinforced a significant deposition of la plata river silts at the rio grande cone these higher magnetic silts with intermediate fe contents mirror the modern more humid terrestrial climatic conditions over se south america

variable anelastic attenuation and site effect in estimating source parameters of various major earthquakes including m w 7 8 nepal and m w 7 5 hindu kush earthquake by using far field strong motion data strong motion records of recent gorkha nepal earthquake m w 7 8 its strong aftershocks and seismic events of hindu kush region have been analysed for estimation of source parameters the m w 7 8 gorkha nepal earthquake of 25 april 2015 and its six aftershocks of magnitude range 5 3 7 3 are recorded at multi parametric geophysical observatory ghuttu garhwal himalaya india 600 km west from the epicentre of main shock of gorkha earthquake the acceleration data of eight earthquakes occurred in the hindu kush region also recorded at this observatory which is located 1000 km east from the epicentre of m w 7 5 hindu kush earthquake on 26 october 2015 the shear wave spectra of acceleration record are corrected for the possible effects of anelastic attenuation at both source and recording site as well as for site amplification the strong motion data of six local earthquakes are used to estimate the site amplification and the shear wave quality factor q at recording site the frequency dependent q f 124f 0 98 is computed at ghuttu station by using inversion technique the corrected spectrum is compared with theoretical spectrum obtained from brune s circular model for the horizontal components using grid search algorithm computed seismic moment stress drop and source radius of the earthquakes used in this work range 8 20 1016 5 72 1020 nm 7 1 50 6 bars and 3 55 36 70 km respectively the results match with the available values obtained by other agencies

high resolution seismic tomography of the 2015 mw7 8 gorkha earthquake nepal evidence for the crustal tearing of the himalayan rift the mw7 8 gorkha earthquake struck nepal and ruptured the boundary between the indian and eurasian plates we conducted 2d pg wave tomography to clarify the seismogenic structure and try to understand causal mechanisms for this large earthquake using the aftershock data recorded by 15 broadband seismic stations located near the china nepal border our high resolution results show that coseismic slip area of the main shock is consistent with the high p wave velocity anomaly and the region of maximum slip has a larger area with higher velocity than the region of initial slip possibly resulting in the dominant low frequency radiation of energy observed after the dominant high frequency radiation of energy in the source rupture process the boundary between these regions of contrasting high and low seismic velocity anomalies suggests a potential crustal tearing at the southern end of the tangra yum co rift possibly resulting from different thrust speeds in the greater himalaya

increasing seismicity in southern tibet following the 2015 mw 7 8 gorkha nepal earthquake abstract we conducted a systematic detection of micro seismicity in southern tibet 1 6 days before and 4 4 days after the 2015 mw 7 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 mw 5 8 tingri and mw 5 3 nyalam earthquakes about 3 and 11 h after the mainshock respectively although the static stress changes cfs showed a slightly better correlation with the seismicity rate changes than the peak dynamic stress changes cfs t the absolute value of the static stress change at the epicenter region of the mw 5 8 tingri earthquake is 10 kpa roughly two orders smaller than the peak dynamic stress change of 2 2 mpa 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

rupture model of mw 7 8 2015 gorkha nepal earthquake constraints from gps measurements of coseismic offsets abstract we estimate coseismic offsets at 20 sites in india due to the 25 april 2015 gorkha nepal mw 7 8 earthquake only four sites in the indian region immediately to the south of the rupture showed discernible coseismic horizontal offsets ranging between 3 and 7 mm toward north we invert these offsets along with 13 other offsets at gps sites in nepal and 33 offsets at sites in china for the estimation of slip distribution on the causative rupture we assume that rupture occurred on the main himalayan thrust mht in our estimated slip model high slip reaching 5 m occurred east of the mainshock epicenter and the slip on rupture terminated close to the main boundary thrust mbt thus the rupture for this earthquake remained blind increasing the potential for future earthquake in the shallow updip unruptured part of the mht

magnitude calibration of north indian earthquakes this article is concerned primarily with the evaluation of the size and location of northern indian and southern tibetan earthquakes during the last 200 yr it draws attention to the problems of assessing intensity of early and more recent earthquakes in a built environment which is different from that for which the intensity scale has been constructed and to the way in which isoseismals are drawn through a re evaluation of intensities and a reassessment of isoseismals a formula for the estimation of surface wave magnitude using isoseismal radii is derived this formula is used to estimate the surface wave magnitudes of 16 earthquakes that occurred in the region between 1803 and 1900 this study shows that it is possible to calculate accurate surface wave magnitudes for earthquakes that occurred before the advent of the scale and that there is no need to resort to empirical formulae for the assessment of the size and seismic moment release of pre 20th century earthquakes also derived are formulae for the conversion of ms to m0 in total locations surface wave magnitudes and m0 estimates are presented for 43 important events that occurred in the region between 1803 and 1974 eight of which were in the lower crust or were subcrustal we find that the m0 ms scaling for india yields smaller ms than the global relation and that the methodology used can help to evaluate more realistic slip rates as well as to address other issues related to earthquake hazard in northern india

gravity increase before the 2015 mw 7 8 nepal earthquake the 25 april 2015 nepal earthquake mw 7 8 ruptured a segment of the himalayan front fault zone four absolute gravimetric stations in southern tibet surveyed from 2010 2011 to 2013 and corrected for secular variations recorded up to 22 40 1 11 gal yr of gravity increase during this period the gravity increase is distinct from the long wavelength secular trends of gravity decrease over the tibetan plateau and may be related to interseismic mass change around the locked plate interface under the himalayan tibetan plateau we modeled the source region as a disk of 580 km in diameter which is consistent with the notion that much of the southern tibetan crust is involved in storing strain energy that drives the himalayan earthquakes if validated in other regions high precision ground measurements of absolute gravity may provide a useful method for monitoring mass changes in the source regions of potential large earthquakes