crustal velocity structure around the eastern himalayan syntaxis implications for the nucleation mechanism of the 2017 ms 6 9 mainling earthquake and regional tectonics abstract a magnitude ms 6 9 earthquake occurred on november 18 2017 in mainling southeastern tibet which is the largest earthquake to occur in or around the eastern himalayan syntaxis within the last 50 years to further understand the nucleation mechanism of this earthquake the local seismicity distribution and the regional tectonics the detailed crustal velocity structure is obtained by direct ambient noise tomography using the rayleigh wave phase velocity data t 5 40 s in this area the spatial correlation of the velocity model with the distribution of the seismicity reveals that the nucleation mechanism of the 2017 ms 6 9 mainling earthquake is closely related to the local stress condition and velocity structure and to the aqueous fluid and geothermal states our velocity model is extensively compared with previous magnetotelluric inversion results and reveals the distribution and connectivity of the crustal low velocity zones lvzs the general patterns of the velocity model in the middle crust show lvzs in the northwest and high velocity zones in the southeast that are truncated by major faults we also find a relatively low velocity anomaly in the upper crust near the namche barwa massif this can be explained by the conceptional tectonic aneurysms model which emphasizes the coupling effects of climate erosion and tectonics to reconcile our velocity model with previous observations we propose a tentatively integrated geodynamic model to explain the regional seismicity and stress condition

mobility of major minor and some redox sensitive trace elements and rare earth elements during weathering of four granitoids in central portugal abstract element mobility was studied in four different granitoids in central portugal samples of fresh and weathered rock parts were collected from each type of granitoid an increase in the degree of weathering is accompanied by reductions in na 2 o cao and sio 2 plagioclase p 2 o 5 apatite and in most cases also by reduction in k 2 o biotite potash feldspar losses as well as gains are observed for mgo relative changes in the al 2 o 3 contents are attributed to physical transport or accumulation of fine weathering products mass balance calculations indicate that kaolinite and in some cases also gibbsite are the dominant weathering products this is in agreement with x ray diffraction analyses manganese is found to decrease but not fe there is a high correlation between v and fe this is preserved during weathering there were both increases and decreases in the trace elements cr as and sb u had become slightly enriched in the weathered parts no systematic trends in ree behaviour were observed differences in the behaviour of these elements and in their ratios can be explained by a combination of factors such as differential dissolution of the host minerals redox conditions and redox kinetics complexation by organic and inorganic ligands and sorption the interpretation of the results is complicated by apparent inhomogeneities in the granites on the mesoscale of an outcrop

surface deformation and lower crustal flow in eastern tibet field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern tibetan plateau since about 4 million years ago instead central eastern tibet has been nearly stationary relative to southeastern china southeastern tibet has rotated clockwise without major crustal shortening and the crust along portions of the eastern plateau margin has been extended modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle this model also predicts east west extension on the high plateau without convective removal of tibetan lithosphere and without eastward movement of the crust east of the plateau

propagation of the deformation and growth of the tibetan himalayan orogen a review abstract long standing problems in the geological evolution of the tibetan himalayan orogen include where the india asia convergence was accommodated and how the plateau grew to clarify these problems we review the deformations and their role in the plateau s growth our results show that 1630 km of shortening occurred across the tibetan himalayan orogen since 55 ma with more than 1400 km accommodated by large scale thrust belts these thrust belts display an outward expansion from central tibet and couple with the surficial uplift the development of the tibetan plateau involved three significant steps primitive plateau 90 55 ma proto plateau 55 40 ma and neoteric plateau 40 0 ma several processes have collaborated to produce the proto plateau including the pre existing primitive plateau the india asia collision and subductions of greater india and songpan ganzi beneath the lhasa qiangtang terrane since 40 ma the proto plateau which was dominated by a topographic gradient lower crustal flow and continuous india asia convergence experienced three periods of rapid outward growth 40 23 23 10 and 10 0 ma in general the n s trending rifts were caused by the eastward growth of the plateau dominated by thrusting and crust flow in central tibet while they were the results of intense n s shortening in himalaya

evidence for mechanically coupled lithosphere in central asia and resulting implications the recent dramatic increase in seismic anisotropy and surface global positioning system gps data for central asia permits a comprehensive examination of the mantle s role in mountain building a joint analysis of 178 shear wave splitting and 2000 gps observations using a new technique reveals that the crust and lithospheric mantle deform coherently arguing for crust mantle mechanical coupling during deformation the observed spatial variations in anisotropy refl ect the large scale pattern of lithospheric deformation as well as a change in deformational style from simple shear on the tibetan plateau transitioning to pure shear in surrounding regions

correlation between geology and radon levels in groundwater soil and indoor air in bhilangana valley garhwal himalaya india radon concentrations were measured in soil air and groundwater in bhilangana valley garhwal himalaya india by using an lr 115 plastic track detector and radon emanometer radon concentrations were found to vary from 1 kbq m3 to 57 kbq m3 in soil 5 bq l to 887 bq l in water and 95 bq m3 to 208 bq m3 in air the recorded values are quite high due to associated uranium mineralization in the area radon concentration was also found to depend on the tectonic structure and geology of the area

weakly coupled lithospheric extension in southern tibet a b s t r a c t west east extension is a prominent tectonic feature of southern and central tibet despite ongoing north south n s convergence between india and eurasia knowledge of deep structure beneath the n s trending rifts is key to evaluating models proposed for their origin including gravitational collapse oblique convergence along the arcuate plate boundary and mantle upwelling we model direct s and moho reflected sspmp phases at teleseismic distances to constrain variations in crustal thickness across the major rifts crossed by a 900 km long w e broadband array in the lhasa terrane crustal thicknesses are 70 80 km however moho depth decreases by 10 km within a horizontal distance of 100 km west of the yadong gulu rift ygr and nyainquentanghla mountains nqtl this moho uplift taken with deep extensional focal mechanisms and reduced seismic velocity in the upper mantle suggests that asthenospheric upwelling has significantly contributed to the pattern of extension across the ygr and nqtl the 100 km separation between surface rift and moho uplift is likely enabled by partial decoupling across a ductile middle crust 2015 the authors published by elsevier b v this is an open access article under the cc by nc nd license http creativecommons org licenses by nc nd 4 0

tectonic control of yarlung tsangpo gorge revealed by a buried canyon in southern tibet the himalayan mountains are dissected by some of the deepest and most impressive gorges on earth constraining the interplay between river incision and rock uplift is important for understanding tectonic deformation in this region we report here the discovery of a deeply incised canyon of the yarlung tsangpo river at the eastern end of the himalaya which is now buried under more than 500 meters of sediments by reconstructing the former valley bottom and dating sediments at the base of the valley fill we show that steepening of the tsangpo gorge started at about 2 million to 2 5 million years ago as a consequence of an increase in rock uplift rates the high erosion rates within the gorge are therefore a direct consequence of rapid rock uplift

mapping radon prone areas a geophysical approach radon prone areas in israel were mapped on the basis of direct measurements of radon 222rn in the soil rock gas of all exposed geological units supported by the accumulated knowledge of local stratigraphy and sub surface geology measurements were carried out by a modified alpha track detection system resulting in high radon levels mainly in rocks of the senonian paleocene aged mount scopus group comprised of chert bearing marly chalks rich in phosphorite which acts as the major uranium source issues of source depth seasonal variations and comparison with indoor radon levels are addressed as well this approach could be applied to other similar terrains especially the mediterranean phosphate belt

elastic thickness of the himalayan tibetan orogen estimated from the fan wavelet coherence method and its implications for lithospheric structure abstract this paper is concerned with the spatial variation of the elastic thickness t e in the himalayan tibetan orogen and its implications for the understanding of lithospheric structure and deformation new t e maps of the himalayan tibetan orogen are generated from the new combined satellite terrestrial gravity eigen6c3stat and topography etopo1 models using the fan wavelet coherence technique the high t e values 60 km are observed in the indian shield and the tarim basin while the low t e values 40 km are prevailing over most of the tibetan plateau we also find that the t e distributions estimated using the high and low central wavenumber i e k 0 wavelets are different in southern tibet by combining constraints from the current seismic and thermo rheological modeling this difference may reflect that the strength of the lithosphere in southern tibet mainly resides in the lithospheric mantle within most parts of central and northern tibet the t e values are relatively low 30 km indicating that the entire lithosphere is weak our analysis finds that the t e variations are probably associated with changes in lithosphere structure we interpret the abrupt changes in t e between southern and northern tibet to indicate the location of the underthrusting strong indian lithosphere beneath tibet our results suggest that the northern limit of the underthrusting indian plate reaches as far north as the hindu kush and the southwestern margin of the tarim basin near 70 80 e and extends along the bangong nujiang suture in the central 80 87 e eastward between 87 e 93 e it may move to the indus tsangpo suture indicating a delamination of indian mantle lithosphere there further to the east it may underthrust northward beneath the eastern qiangtang block

crustal structure variation along 30 n in the eastern tibetan plateau and its tectonic implications abstract we determined crustal structure along the latitude 30 n through the eastern tibetan plateau using a teleseismic receiver function analysis the data came mostly from seismic stations deployed in eastern tibet and western sichuan region from 2004 to 2006 crustal thickness and vp vs ratio at each station were estimated by the h k stacking method on the profile the mean crustal thickness and vp vs ratio were found to be 62 3 km and 1 74 in the lhasa block 71 2 km and 1 79 near the bangong nujiang suture 66 3 km and 1 80 in the qiangtang block 59 8 km and 1 81 in the songpan garze block and 42 9 km and 1 76 in the yangtze block respectively the estimated crustal thicknesses are consistent with predictions based on the topography and the airy isostasy except near the bangong nujiang suture and in the qiangtang block where the crust is 5 10 km thicker than predicted indicating that the crust may be denser possibly due to mafic underplating we also inverted receiver functions for crustal velocity structure along the profile which reveals a low s wave velocity zone in the lower crust beneath the eastern tibetan plateau although the extent of the low velocity zone varies considerably the low velocity zone together with previous results suggests limited partial melting and localized crustal flow in the lower crust of the eastern tibetan plateau

distribution of radon sources and effects on radon emanation in granitic soil at ben lomond california the abundance and distribution of radioelements on bulk and microscopic scales were investigated in residual granitic derived soil at a facility for investigating the movement of radon into structures in bulk soil samples ra concentrations range from 0 6 to 1 3 pci g and variations in ra th and k appear to be controlled mainly by heterogeneities inherited from the parent granitic rock which contains abundant dikes and inclusions u in soil and parent rock is concentrated in primary minerals mainly zircon and sphene and in secondary sites that are of greater importance for rn emanation the main u bearing secondary sites are weathered sphene grain boundary coatings weathered biotite and plagioclase as well as dense fe rich coatings and a ree phosphate mineral present in near vertical fracture zones in saprolite underlying shallow loam elevated u in these sites generally correlates with high ti al fe and or p preferential distribution of u and ra on grain boundaries and porous weathered minerals is reflected in relatively high rn emanation rates in the soil highest emanation occurs between 1 3 and 2 3 m depth where fine pedogenic phasesgibbsite and amorphous silica and fe ooh are most abundant it is related to fixation of ra by these phases which precipitate close to the surface and accumulate at these depths by illuviation separation of ra from u may occur locally given remobilization of u series elements from secondary sites and large differences between ra and u sorption capabilities of several phases present in the soil concentration of u along permeable fracture zones in saprolite suggests that contribution of soil gas rn from depth 2 m could be significant to rn availability near the surface

recoil emanation theory applied to radon release from mineral grains abstract in this paper the recoil emanation theory is presented as a major mechanism for rn release from solid materials the basic theory is developed for rn emanation from geometrical shapes spheres and cylinders having variable thickness of precursor ra containing material subsequently a sphere pore model of emanation from mineral grains like those in rocks soils etc is developed in this model a surface of the grain is constructed as a superposition of in and out directed spherical caps and cylindrical pores the model incorporates processes like rn embedding pore overlap water effect and emanation from the edges using such a geometrical model it is shown how the rn emanating power measurements can give a clue to the ra distribution and surface properties of the samples in particular it is shown that for grains reasonably larger than the recoil range and for surface ra distribution the emanating power is independent of the grain size but the total ra concentration varies with the reciprocal of the grain size the opposite is true for ra distributed uniformly throughout the volume of the grain it is shown how the rn emanating power is related to the surface porosity of the grain also implications are made with respect to u transport in nature and with respect to low emanating power from lunar soil finally a failure of the emanation theory is discussed to reproduce emanation curves for the samples having high specific surface areas and ra distributed throughout the volume

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

the eastern himalayan syntaxis major tectonic domains ophiolitic melanges and geologic evolution abstract geologic mapping in the eastern himalayan syntaxis confirmed the three regional tectonic elements outlined by previous geologic workers our studies however show that the indus yarlung tsangpo suture iys is a continuous melange zone that forms an inverted u in map view around the namche barwa antiform the namche barwa and nyainqentanglha crystalline complexes lie below and above the iys suture respectively and both were parts of the northern indian plate basement rocks with petrologically and geochronologically correlative protoliths both units were deformed metamorphosed and intruded at the end of the proterozoic the zhibai formation the lower part of the namche barwa group extends along the northwest slope of the himalaya and is mainly composed of highly deformed aluminous felsic gneiss containing sporadic boudins of high pressure granulite in the namche barwa antiform the upper part of the namche barwa group includes a calcareous rock assemblage characteristized by marble and diopside bearing calcsilicate rocks interlayed with felsic gneiss petrochemical studies show that the iys contains lenses of oceanic crustal rocks originated from fore arc trench island arc and back arc basin environments which implies they were derived from a ssz type supra subduction zone ophiolite our field mapping identifies the jiali parlung tsangpo remnant suture jps that lies north of the namche barwa antiform as a possible branch of the neo tethyan oceanic realm subduction of the mesozoic neo tethyan oceanic plate resulted in both mesozoic and cenozoic granite intrusions in the northwest trending gangdise magmatic belt along the southern edge of asia uplift and exhumation have been the most recent dominant tectonic processes in the late cenozoic for the high himalayan crystalline rocks namche barwa group in the core of the namche barwa antiform

finite frequency tomography in southeastern tibet evidence for the causal relationship between mantle lithosphere delamination and the north south trending rifts 1 while several mechanisms have been suggested to explain the evolution of the tibetan plateau observational constraints on the deep lithospheric processes have been sparse and previous seismic studies were mostly along profiles perpendicular to the collision front of the indian and eurasian plates in this study we show tomographic evidence for the delamination of the mantle lithosphere beneath southeastern tibet a process in which the entire mantle lithosphere peels away from the crust along the moho and thus is a mechanism for rapid thinning of the lithosphere our p and s wave velocity models show the presence of a low velocity anomaly in the crust and upper mantle down to 300 km depth beneath a north south trending rift zone in southeastern tibet this low velocity anomaly is situated above a tabular high dipping angle high velocity anomaly that extends into the upper mantle transition zone the vp vs ratio of this high velocity anomaly suggests that temperature variations are not the only cause of the anomaly and a highly melt depleted mantle is required these observations suggest a causal relationship between the delamination of mantle lithosphere and the formation of the north south trending rift in southeastern tibet

crustal and upper mantle structure of southeast tibet from rayleigh wave tomography 1 we have applied the two plane wave inversion technique to fundamental mode rayleigh waves in southeast tibet phase velocity variations are obtained at 15 periods from 20 to 143 s and are used to construct three dimensional shear wave velocity structure a low velocity zone is imaged in the middle crust of southeast tibet in which velocity perturbation varies from 4 to 3 the slow area might be associated with high temperature and partial melt and can flow ductilely while the high velocity region could be relatively cold and mechanically strong enough to pass crustal strain implying that coherent lithospheric deformation is possible with the presence of complicated crustal flow strong negative anomalies in the shallow crust are imaged at 92 e correlating with the location of a north south rift zone a fast mantle lid to a depth of 120 km is present beneath most of the study area the lithosphere is significantly slower in the central part of the study area than in the west and east to the east of 96 e a subvertical high velocity zone is imaged at 120 240 km depths under the bangong nujiang suture bns which is more like the subduction of the asian lithosphere we interpret the high velocity anomalies to the south of the bns as the subducted indian lithosphere and those to the north as the asian lithosphere a vertical low velocity column is observed in the central part of the region from the lower crust to the midupper mantle which is probably in part responsible for the rift at 92 e the slow anomaly is likely associated with asthenosphere upwelling following the opening of a slab window that could have developed when the slab was torn apart vertically because of the significant change of subducting direction at the eastern syntaxis

can erosion drive tectonics can climate modulated erosion affect the location rate and style of tectonic deformation in earth s crust and thus seismic hazards particularly in the himalaya there are clear correlations between rugged topography and high rates of rainfall erosion and rock uplift 1 2 but a vigorous cause and effect debate continues with new papers presenting evidence for 1 4 and against 5 7 erosional control of tectonics see the figure although much field data are consistent with predicted associations among topography erosion climate and deformation unambiguous evidence has proven elusive 8 by focusing on a simple diagnostic test wang et al show on page 978 1 of this issue 9 that the zone of rugged topography and extreme erosion rates where the tsangpo brahmaputra river cuts through the namche barwa massif see the figure often argued to reflect a dynamic tectonic response to river incision 2 records instead a passive landscape response to tectonics over the past 2 to 2 5 million years the data threaten to undermine one of the most dramatic examples of a proposed tectonic response to erosion 1 lookup volpage 346 978 iss 6212

pedogeochemical models on prognosis and control of radon fluxes from humid tropical landscapes over granite the principal relationships between radon 222rn and 220rn exhalation intensities and the morpho dynamic elements of humid tropical landscapes have been established and analyzed with the objective of elaborating rn exhalation models which can be used on the scale of small habitational nuclei the current radioactive processes of generation emanation and migration of rn in relation to its exhalation rates on a landscape slope of granitic rock having normal u and th contents were correlated with the latosol podzolic soil association developed as a product of supergene processes during geological and pedological times and also with the water regime of an overlying phreatic aquifer this approach encompassing pedogeochemical models of radionuclide dispersion linked to soil systems and surface geochemistry was framed within a tridimensional interdisciplinary and systemic focus using concepts of nuclear physics climate and hydrogeology the characteristic signatures of elementary landscapes include 1 different landforms namely eluvial transeluvial and superaqual 2 residual soils having varying types thicknesses and perma porosities and 3 radioanomalies corresponding to different u and th concentrations secondary hosting minerals and also to different pedological ages considering these factors and their spatial relationships and on the basis of moisture content of soils it is postulated that the highest rn exhalation rates especially of 222rn are confined to superaqual and transeluvial landscapes in an eluvial landscape the rn fluxes are found to be less important even though gamma anomalies exist mainly due to the presence of resistant minerals containing u and th in short the products of supergene alteration organized in a sloping system can exhibit rn exhaling intensities higher than that measured on unaltered subjacent rock

convergence of the indian and eurasian plates under eastern tibet revealed by seismic tomography 1 a three dimensional p wave velocity model of the crust and upper mantle down to 400 km depth beneath eastern tibet is obtained using many temporary seismic stations of the ascent project and the namche barwa broadband seismic network we collected 16 508 arrival times of p pn and pg phases from 573 local and regional earthquakes and 7 450 p wave arrivals from seismograms of 435 teleseismic events our high quality data set enables us to reconstruct the 3 d velocity structure under eastern tibet in more detail than the previous studies in the shallow depth our results show that the low velocity zones are not interconnected well no wide spread low velocity zones which may reflect the complex pattern of material flowing in the study region below the moho we find that the indian lithospheric mantle underthrusts sub horizontally under eastern tibet and the extent of the northward advancing indian lithosphere decreases from west to east in the north the asian lithospheric mantle is detected under the vicinity of the qaidam basin between the indian and asian lithospheric mantles there is an obvious low velocity anomaly which may reflect an upwelling mantle diapir

subduction of the indian lithosphere beneath the tibetan plateau and burma abstract subduction of the indian lithosphere under eurasia plays an important role in the tectonic evolution of the tibetan plateau and surrounding regions to improve our knowledge of pertinent mantle structures through tomographic imaging we combine p wave arrival time data from temporary arrays in tibet and stations of the chinese seismograph network with reprocessed data from the international seismological centre the new images reveal considerable spatial variations in mantle structure along the collision zone and the horizontal distance over which presumed continental indian lithosphere slides northward beneath the plateau decreases from west where it underlies the himalayas and the entire plateau to east where no indication is found for present day underthrusting beyond the himalayan block and indus tsangpo suture p wavespeed appears low in the shallow mantle beneath much of central and eastern tibet these observations suggest that indian lithosphere underlies only the southwestern part of the plateau and that the central and northeastern part is underlain by lithosphere of asian origin the continental parts of the indian plate that currently underthrust or subduct below the plateau appear generally detached from the oceanic slab fragments that subducted longer ago and that have been detected deeper in the mantle except perhaps in the central part of the collision zone 80 90 e this suggests that ongoing india eurasia collision must increasingly be driven by other forces such as subduction of the indian plate further west and east e g beneath indochina our images reveal structures associated with eastward subduction along the burmese arc southeast of the eastern himalayan syntaxis the tengchong volcanic complex in southwest china is marked by slow wave propagation to 150 km depth suggesting a causal link to subduction along the burmese arc the low velocities beneath the red river fault region extend to greater depth and may be related to upper mantle processes further southeast

kinematics and dynamics of the namche barwa syntaxis eastern himalaya constraints from deformation fabrics and geochronology abstract field observations deformation and fabric analyses and precise age data acquired by zircon shrimp la icp ms u pb and 40 ar 39 ar dating methods have yielded new constraints on the kinematics and dynamics of the namche barwa syntaxis nbs which is the eastern corner of the himalaya a two stage model has been established to explain the formation and evolution of the nbs the northward indentation of the indian plate beneath the lhasa terrane began at 55 40 ma and crustal materials at this corner were subducted to depths 70 km where they experienced hp uhp metamorphism since 40 ma large scale right lateral strike slip along the sagaing fault has accommodated the rapid northward movement of the eastern indian plate corner with respect to the indochina block this caused significant and progressive bending of the indus yarlung suture zone iysz such that it became the dongjiu milin left lateral strike slip shear zone dmsz in the west and the aniqiao motuo right lateral strike slip shear zone amsz in the east both zones underwent strong mylonitization meanwhile the hp uhp metamorphic rocks were rapidly exhumed first into the deep crust at 22 18 ma and then to the shallow crust to form an antiformal dome at 6 2 ma our model provides new insight into the processes of post collisional crustal thickening related to the formation of the himalayan orogenic belt

experimental study of bore driven swash hydrodynamics on impermeable rough slopes abstract a detailed experimental investigation of the hydrodynamics of large scale bore driven swash on impermeable rough beach slopes is described the experiments were carried out on 1 10 impermeable rough slopes with three different surface roughnesses based on 1 3 mm sand 5 4 mm gravel and 8 4 mm gravel the large scale discrete swash event was produced by the collapse of a dambreak generated bore on the beach simultaneous depths and velocities were measured using lif laser induced fluorescence and piv particle image velocimetry respectively yielding better resolution of the hydrodynamics than previous studies depth time series instantaneous velocity profiles depth averaged velocities instantaneous turbulent kinetic energy profiles depth averaged turbulent kinetic energy reynolds stress profiles and bed shear stresses are presented for five cross shore measurement locations in the swash the measurements resolve the backwash shoreline position and the late backwash period when depths are shallow and velocities are high the detailed data can be used to test and develop advanced numerical models for bore driven waves on rough slopes

changing uranium distributions during weathering of granite abstract changes in uranium distribution during chemical weathering were investigated in three granitoid types from the new england district new south wales australia over a range of samples from unweathered rock to profoundly weathered material uranium fission track micromapping was used to characterise the three principal modes of u abundance in unweathered granitoid rock low concentrations of background u in fine fractures in quartz and in deuterically altered feldspar biotite and hornblende interstitial u in concentrations between 140 and 1500 g g 1 principally in hydrated fe oxide mn oxide and clay minerals and the greatest proportion as resistate u 90 4000 g g 1 located in the accessory minerals during low temperature chemical weathering a significant net u loss occurs and the remaining u is redistributed amongst the three modes background u is depleted and the mobilised u is adsorbed by interstitial aggregates thereby increasing interstitial u concentrations resistate u is also depleted as sphene zircon monazite and acicular apatite retain their initial u concentrations but are reduced in modal abundance prismatic apatite fluorite and allanite are progressively removed the significant net loss of u during chemical weathering provides uranium for potential secondary sedimentary mineralisation and implies that weathered granitoid rock is not an appropriate element in the geological barrier for nuclear waste

coupling of rock uplift and river incision in the namche barwa gyala peri massif tibet geodynamic modeling demonstrates the strong potential for erosion to influence the pattern and style of deformation in active mountain belts but field studies yield conflicting views on the importance of erosion in influencing orogenesis here we compare patterns in river power inferred excess fluvial transport capacity topographic relief precipitation and mineral cooling ages to assess the coupling between surface erosion and rock uplift within the vicinity of the namche barwa gyala peri massif an active antiformal structure within the eastern himalayan syntaxis our rich and dense data set reveals a tight spatial correspondence of fluvial incision potential high relief and young cooling ages the spatial coincidence is most easily explained by a sustained balance between rock uplift and denudation driven by river incision over at least the last 1 m y the yarlung tsangpo brahmaputra river is the largest and most powerful river in the himalaya and two lines of evidence point to its active role in the dynamic interaction of local erosion rock uplift thermal weakening of the lithosphere and deformation 1 whereas along the rest of the himalayan front high relief and high rock uplift rates are essentially continuous the high relief and rapid exhumation in the syntaxis is restricted to a bull s eye pattern exactly where the largest river in the himalaya the yarlung tsangpo brahmaputra has the most energy per unit area available to erode its channel and transport sediment 2 the location of rapid incision on the yarlung tsangpo brahmaputra has been pinned for at least 1 m y and without compensatory uplift of the namche barwa gyala peri massif during this time the river would have eroded headward rapidly incising deeply into tibet

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

factors controlling the emanation of radon and thoron in soils of the eastern u s a abstract emanation coefficients proportion of generated rn atoms that escape from a solid material have been measured for 222rn t 1 2 3 8 days and 220rn thoron t 1 2 55 s on 68 disaggregated soil samples from 12 soil profiles representative of the eastern u s a average values for sites are 0 20 for 222rn and 0 16 for 220rn based on distribution of 226ra among the exchangeable organic fe oxide sand silt and clay fractions of the soils a multiple regression indicates that the organic exchangeable fraction occurring mainly as coatings on grains has an emanation coefficient for 222rn of 0 46 and the silt clay fraction has an emanation coefficient of 0 22 the latter value is verified by experiments the organic component makes the largest single contribution to rn in soil gas mineral grains have twice the 222rn emanation as 220rn implying that about half the rn atoms are emanated directly to pore space and the remainder are freed by track etching and diffusion over a period of days emanation for 220rn appears to be dominated by fe oxides the main host for pedogenic 232th surface a and e horizons have low emanation coefficients for su220 rn probably because of a lack of fe oxides in these horizons

heterogeneity and anisotropy of the lithosphere of se tibet from surface wave array tomography 1 understanding the geotectonic evolution of the southeastern tibetan plateau requires knowledge about the structure of the lithosphere using data from 77 broadband stations in sw china we invert rayleigh wave phase velocity dispersion curves from ambient noise interferometry t 1 0 40 s and teleseismic surface waves t 2 0 150 s for 3 d heterogeneity and azimuthal anisotropy in the lithosphere to 150 km depth our surface wave array tomography reveals 1 deep crustal zones of anomalously low shear wave speed and 2 substantial variations with depth of the pattern of azimuthal anisotropy upper crustal azimuthal anisotropy reveals a curvilinear pattern around the eastern himalayan syntaxis with fast directions generally parallel to the main strike slip faults the mantle pattern of azimuthal anisotropy is different from that in the crust and varies from north to south the tomographically inferred 3 d variation in azimuthal anisotropy helps constrain the source region of shear wave splitting south of 26 n off the high plateau most of the observed splitting can be accounted for by upper mantle anisotropy but for stations on the plateau proper with thick crust crustal anisotropy cannot be ignored on long wavelengths the pattern of azimuthal anisotropy in the crust differs from that in the mantle this is easiest explained if deformation varies with depth the deep crustal zones of low shear wave speed and presumably mechanical strength may represent loci of ductile deformation but their lateral variation suggests that in se tibet localized crustal channel flow and motion along the major strike slip faults are both important

chemical weathering in the drainage basin of a tropical watershed nsimi zoetele site cameroon comparison between organic poor and organic rich waters abstract this study deals with the weathering processes operating at the scale of a small catchment nsimi zoetele cameroon and is focused on the role of organic colloids on mineral weathering and transport of elements in natural waters samples of river spring and groundwaters from nsimi zoetele were filtered through membranes of decreasing pore size 0 22 m 0 025 m or 300 000 da 5000 da to separate colloidal fractions from the truly dissolved one major and trace elements and dissolved organic carbon doc were analysed in each fraction two kinds of waters can be distinguished in the catchment clear and coloured waters clear waters exhibit low concentrations of major and trace elements and doc elements are carried in these solutions in a true dissolved form except al and rare earth elements rees by contrast the higher abundances of al fe and trace elements in coloured waters are controlled by the colloidal fraction thermodynamic equilibrium calculations show that clear waters are in equilibrium with kaolinite and iron oxi hydroxide which are major minerals in the weathered soil for coloured waters the aqueous speciation of ca mg cu fe al la and th was calculated taking into account the complexes with humic acids speciation calculations for cu fe al la th show a strong complexation with humic acids in good agreement with the results of the filtration experiments by contrast although filtration experiments show a strong control of major cations by organic matter for example 75 for ca speciation calculations reveal that their complexes with humic ligands do not exceed a few percent of total dissolved elements this discrepancy is explained as an artefact induced by the organic colloids and occurring during the filtration procedure finally both filtration experiments and speciation calculations show that organic matter plays an important role in natural doc rich waters organic acids increase significantly the dissolution rates of silicates and oxi hydroxides and thus the amounts of solutes and of complexed elements leaving the catchment

geodynamics of the southeastern tibetan plateau from seismic anisotropy and geodesy ongoing plate convergence between india and eurasia provides a natural laboratory for studying the dynamics of continental collision a fi rst order process in the evolution of continents regional climate and natural hazards in southeastern tibet the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with the surfi cial geology including major sutures and shear zones and with the surface strain derived from the global positioning system velocity fi eld these observations are consistent with a clockwise rotation of material around the eastern himalayan syntaxis and suggest coherent distributed lithospheric deformation beneath much of southeastern tibet at the southeastern edge of the tibetan plateau we observe a sharp transition in mantle anisotropy with a change in fast directions to a consistent e w direction and a clockwise rotation of the surface velocity surface strain fi eld and fault network toward burma around the eastern himalayan syntaxis the coincidence between structural crustal features surface strain and mantle anisotropy suggests that the deformation in the lithosphere is mechanically coupled across the crust mantle interface and that the lower crust is suffi ciently strong to transmit stress at the southeastern margin of the plateau in yunnan province a change in orientation between mantle anisotropy and surface strain suggests a change in the relationship between crustal and mantle deformation lateral variations in boundary conditions and rheological properties of the lithosphere play an important role in the geodynamic evolution of the himalayan orogen and tibetan plateau and require the development of three dimensional models that incorporate lateral heterogeneity

distribution of indoor radon concentrations and uranium bearing rocks in texas the purpose of this study was to compare regional patterns of indoor radon concentration with uranium bearing rock zones and county populations in texas zones yielding radon concentrations that are relatively high for texas include shale and sandstone in northwest texas red beds in north central texas felsic volcanic rocks in west texas and sandstone limestone and igneous rocks in central texas located in northwest texas only five of the 202 counties evaluated have mean indoor radon concentrations above 4 0 pci l 1 two of those counties have populations above the state median of 20 115 the highest county mean concentration is 8 8 pci l 1 results of this study suggest that 1 regional geology influences indoor radon concentrations in texas 2 statewide the radon concentrations are relatively low 3 highly populated counties do not coincide with regions of high indoor radon concentration and 4 regions that may warrant further monitoring include northwest texas and to a lesser degree west and central texas

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

structural control of rupturing of the mw7 9 2008 wenchuan earthquake china abstract analyses of global seismic waveform data for the 2008 devastating wenchuan earthquake have indicated where the rupture started and how it expanded here we reveal that the rupture process of this earthquake was strongly controlled by structural heterogeneities of the upper crust we made a tomographic inversion of 200 000 local travel time data according to which the rupture was confined in a presumably brittle layer of high p and s wave velocity anomalies within the upper 15 km depths the rupture propagated northeastward through the southwest sw segment of the fault and then jumped to the northeast ne segment with little slip at the intervening presumably ductile zone characterized by low p and s velocities with high poisson s ratio the rupture initiated near the southwestern end of the sw segment within a body of high poisson s ratio which extends down into the lower crust suggesting upward migration of deep seated aqueous fluid to trigger the earthquake by reducing the mechanical strength of the brittle layer

tearing of the indian lithospheric slab beneath southern tibet revealed by sks wave splitting measurements a b s t r a c t shear wave birefringence is a direct diagnostic of seismic anisotropy it is often used to infer the northern limit of the underthrusting indian lithosphere based on the seismic anisotropy contrast between the indian and eurasian plates most studies have been made through several near north south trending passive source seismic experiments in southern tibet to investigate the geometry and the nature of the underthrusting indian lithosphere an east west trending seismic array consisting of 48 seismographs was operated in the central lhasa block from september 2009 to november 2010 splitting of sks waves was measured and verified with different methods along the profile the direction of fast wave polarization is about 60 in average with small fluctuations the delay time generally increases from east to west between 0 2 s and 1 0 s and its variation correlates spatially with north south oriented rifts in southern tibet the sks wave arrives 1 0 2 0 s later at stations in the eastern part of the profile than in the west the source of the anisotropy estimated by non overlapped parts of the fresnel zones at stations with different splitting parameters is concentrated above ca 195 km depth all the first order features suggest that the geometry of the underthrusting indian lithospheric slab in the himalayan tibetan collision zone beneath southern tibet is characterized by systematic lateral variations a slab tearing and or breakoff model of indian lithosphere with different subduction angles is likely a good candidate to explain the observations

kinematics and strain rates of the eastern himalayan syntaxis from new gps campaigns in northeast india abstract newly acquired gps data along transects across himalaya in eastern himalayan syntaxis ehs reveal a clockwise rotation of rigid micro plate comprising part of brahmaputra valley ne himalaya and northern myanmar that rotates about a pole located at 14 5 n 100 8 e at an angular rate of 1 75 0 12 myr the ehs is being torn off from the main indian plate as a rigid block around which the kinematic clockwise rotation of tibetan gps sites toward the sichuan yunnan region occurs in the eurasia fixed frame the residual velocity field of the newly acquired data estimated after removing the rotation that minimizes the gps rates around ehs show a clear ne motion of the ehs sites indentation of the rigid indian plate into a less rigid area of the eurasian plate the most extensive ehs zones of compression and shortening are in the direction of indenter convergence with average values ranging between 50 100 nanostrain year along the frontal segment of ehs from nw to se the shortening rate is reduced from the local maximum value of 160 to 80 nanostrain year thus indicating a possibly locked fault patch of mishmi or lohit thrusts the southernmost part of segment activated during the large 1950 assam earthquake mw 8 6 an elastic block model was invoked to infer the average slip rates of sections around ehs and to estimate an average locking depth of 15 km the slip rate perpendicular to the locked sector of ehs reaches 32 4 mm year and permits to roughly infer a recurrence time of 200 year for an earthquake as energetic as the 1950 assam event

radon emanation from giant landslides of koefels tyrol austria and langtang himal nepal the identification of extremely high indoor radon concentrations in the village umhausen tyrol austria initiated a scientific program to get information about the source and distribution of this noble gas the high concentrations can not be related to u anomalies or large scale fault zones the nearby giant landslide of koefels with its highly fractured and crushed orthogneisses are the only possible source of radon despite the fact that the u and ra content of the rocks is by no means exceptional the reasons for the high emanation rates from the landslide are discussed and compared to results gained from a similar examination of the giant landslide of langtang himal nepal the exceptional geologic situation in both cases as well as the spatial distribution of different concentration levels indicate that both landslides must be considered as the production sites of radon independent of the u and ra contents of the rocks the most important factors producing high emanation rates are the production of a high active surface area and circulation pathways for rn enriched soil air by brittle deformation due to the impact of the landslidemass

a synoptic view of the distribution and connectivity of the mid crustal low velocity zone beneath tibet 1 based on 1 2 years of continuous observations of seismic ambient noise data obtained at more than 600 stations in and around tibet rayleigh wave phase velocity maps are constructed from 10 s to 60 s period a 3 d vsv model of the crust and uppermost mantle is derived from these maps the 3 d model exhibits significant apparently inter connected low shear velocity features across most of the tibetan middle crust at depths between 20 and 40 km these low velocity zones lvzs do not conform to surface faults and significantly are most prominent near the periphery of tibet the observations support the internal deformation model in which strain is dispersed in the deeper crust into broad ductile shear zones rather than being localized horizontally near the edges of rigid blocks the prominent lvzs are coincident with strong mid crustal radial anisotropy in western and central tibet and probably result at least partially from anisotropic minerals aligned by deformation which mitigates the need to invoke partial melt to explain the observations irrespective of their cause in partial melt or mineral alignment mid crustal lvzs reflect deformation and their amplification near the periphery of tibet provides new information about the mode of deformation across tibet