afterslip evolution on the crustal ramp of the main himalayan thrust fault following the 2015 mw 7 8 gorkha nepal earthquake abstract current afterslip models of the mw 7 8 gorkha earthquake contradict with the depth ranges of relocated aftershock distribution and inter seismic locked creeping transition zone we use both gps and interferometric synthetic aperture radar insar data to image the afterslip evolution in the first 189 post seismic days i e from 25 april to 1 november 2015 in the study region 51 gps stations are divided into three categories based on their observation time 1 25 stations with both pre and post seismic observations 2 16 stations with only post seismic observations and 3 10 stations with only pre seismic observations the secular tectonic motion and seasonal variations are corrected carefully and directly using the fitted functions from the pre seismic position time series during the inversions we adopt the widely accepted flat ramp flat geometrical model of the main frontal thrust fault mft main himalayan thrust fault mht the preferred weight ratios between gps and insar observations are elaborately determined through comprehensive analysis of model resolution and fitting residuals in contrast to previous afterslip models our preferred afterslip distributes on the crustal ramp of the mht from depths of 11 to 29 km which is verified by further inversions using only gps data and checkerboard resolution tests the seismic moment released by the afterslip in the first six months is 3 42 1019 n m only approximately 4 of the mainshock moment the rupture gap between the mainshock and the 12 may aftershock is filled up with post seismic aseismic slip

persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

characteristics of turbulent unidirectional flow over rough beds double averaging perspective with particular focus on sand dunes and gravel beds 1 we address some unsolved methodological issues in modeling of natural rough bed flows by critically examining existing approaches that parameterize rough bed flows these often utilize loosely defined variables here we suggest that double averaging in time and in a volume occupying a thin slab in a plane parallel to the mean bed provides a rigorous straightforward alternative that can aid in the parameterization process we further present two examples two dimensional bed form and gravel bed flows we argue that the double averaging approach based on momentum equations should serve as a better methodological basis for modeling phenomenological developments and parameterizations these equations explicitly include drag terms and form induced momentum fluxes due to spatial heterogeneity of the time averaged flow in the near bed region they also provide a solid basis for better definitions of basic flow variables including the shear stress partitioning into turbulent and form induced momentum fluxes skin friction and pressure form drag we show that for a range of rough bed flows the vertical distribution of the double averaged velocity consists of two distinct regions 1 a linear region below roughness tops and 2 a logarithmic region above them

predicting incipient motion including the effect of turbulent pressure fluctuations in the bed 1 incipient motion of particles on a river bed can in principle be understood and predicted from a balance of the forces acting on the particles on a natural river bed the exposure of particles to the flow is variable the effect of exposure on the initiation of motion including the case of deep embedding is studied in this paper so far the turbulence induced lifting force has been derived exclusively from examinations of the surface flow the understanding of destabilization processes of the riverbed is improved when turbulence induced vertical pressure gradients in the upper sediment layer are included this is particularly important for particles that lie in the lee of larger ones an analytical solution for the critical shields parameter of spherical particles is found including the effects of pressure fluctuations in the bed macroscale flow structures average bed slope and shallow flow existing laboratory data designed to test the effect of exposure and roughness conditions are in excellent agreement with the new model

petroleum geology of the puguang sour gas field in the sichuan basin sw china abstract the puguang sour gas field in northeastern sichuan basin is the largest gas discovery in the paleozoic marine strata in china with at least 9 trillion cubic feet tcf of proven gas reserves it is one of the many anticlinal structures formed during the indo sinian orogeny with gas being trapped in a composite structure lithology pool the presence of the upper permian coal measures lower silurian and lower cambrian marine shales provided excellent hydrocarbon source rocks the lower triassic and upper permian oolitic dolomites serve as high quality reservoir rocks with 10 25 porosity and 1 1000 md permeability largely due to diagenetically produced secondary porosity the lower and middle triassic evaporate beds have acted as the direct top seal for the large lower triassic upper permian gas accumulation the thick upper triassic and jurassic mudstone beds regionally cap the underlying marine carbonate strata the deep seated basement faults acted as vertical hydrocarbon migration conduits during faulting and became effective flow barriers when the faulting ceased the deep burial of a paleo oil accumulation in reservoirs rich in sulfate resulted in extensive thermochemical sulfate reduction tsr this together with the new gas injection and structural reconfiguration transformed a paleo oil pool to a large sour gas pool

sichuan basin and beyond eastward foreland growth of the tibetan plateau from an integration of late cretaceous cenozoic fission track and u th he ages of the eastern tibetan plateau qinling and daba shan combining 121 new fission track and u th he ages with published thermochronologic data we investigate the late cretaceous cenozoic exhumation cooling history of the eastern tibetan plateau qinling daba shan and sichuan basin of east central china the qinling orogen shows terminal southwestward foreland growth in the northern daba shan thrust belt at 100 90 ma and in the southern daba shan fold belt at 85 70 ma the eastern margin of tibet plateau experienced major exhumation phases at 70 40 ma exhumation rate 0 05 0 08 mm yr 25 15 ma 1 mm yr in the pengguan massif 0 2 mm yr in the imbricated western sichuan basin and since 11 10 ma along the longmen shan 0 80 mm yr and the interior of the eastern tibet plateau dadu river gorge min shan 0 50 mm yr the sichuan basin records two basin wide denudation phases likely a result of the reorganization of the upper yangtze river drainage system the first phase commenced at 45 ma and probably ended before the miocene 1 km of rocks were eroded from the central and eastern sichuan basin the second phase commenced at 12 ma and denudated the central sichuan basin longmen shan and southern daba shan more than 2 km of rocks were eroded after the lower yangtze river had cut through the three gorges and captured the sichuan basin drainage in contrast to the east qinling which was weakly effected by late cenozoic exhumation the west qinling and daba shan have experienced rapid exhumation cooling since 15 13 ma a result of growth of the tibetan plateau beyond the sichuan basin

an investigation of seismicity induced by hydraulic fracturing in the sichuan basin of china based on data from a temporary seismic networkan investigation of seismicity induced by hydraulic fracturing in the sichuan basin

the 2019 m w 5 7 changning earthquake sichuan basin china a shallow doublet with different faulting styles the increased seismic activity of the last 10 years in changning county of sichuan province comprised just small mostly ml 5 0 injection induced earthquakes the mw 5 7 earthquake of june 17 2019 is the largest event ever reported there moment tensor of the mainshock was remarkably dominated by a compensated linear vector dipole we resolve its fine structure showing it was a doublet allowing approximation by a thrust and strike slip subevent the mainshock nucleated as thrust faulting which together with the largest aftershocks can be linked with previously known reverse faults favorably oriented to regional stress field contrarily the strike slip segment of the mainshock less favorably oriented was probably facilitated by elevated pore pressure due to previous injections shallow active strike slip faulting not yet mapped in the region is a new feature important for future hazard assessment

effects of a pebble cluster on the turbulent structure of a depth limited flow in a gravel bed river pebble clusters are important morphological features of gravel bed rivers and have a significant effect on the spatial and temporal response of the flow this paper presents original results from measurements of velocity taken at a high spatial and temporal resolution in a turbulent flow upstream and downstream from a pebble cluster three electromagnetic current meters 0 013 m in diameter mounted on a wading rod were deployed upstream and downstream of an isolated pebble cluster along 31 vertical profiles that contained between 7 and 13 points in a 5 m long section the high sampling resolutions in a natural environment permitted characterization of the complex dynamics of the turbulent flow in the vicinity of the cluster the description of these dynamics is based on the interpretation of contour maps of several turbulence statistics including moments of velocity distributions reynolds shear stress quadrant analysis and autocorrelation function downstream from the cluster flow is decelerated the intensity of turbulence increases and zones of strong vertical motions are present the superimposition of the maps allowed us to decompose the field of turbulent flow around a pebble cluster into distinct regions in a downstream direction from the cluster we observed zones of flow acceleration recirculation vortex shedding flow reattachment fluid upwelling and flow recovering results indicate the existence of highly dynamic boundaries between zones where strong intermittent events are generated they also highlight the difference between shedding and upwelling motions of the flow

a mixing layer theory for flow resistance in shallow streams 1 a variety of surface roughness characterizations have emerged from nineteenth and twentieth century studies of channel hydraulics when the water depth h is much larger than the characteristic roughness height ks roughness formulations such as manning s n and the friction factor f can be explicitly related to the momentum roughness height zo in the log law formulation for turbulent boundary layers thereby unifying roughness definitions for a given surface however when h is comparable to or even smaller than ks the log law need not be valid using a newly proposed mixing layer analogy for the inflectional velocity profile within and just above the roughness layer a model for the flow resistance in shallow flows is developed the key model parameter is the characteristic length scale describing the depth of the kelvin helmholtz wave instability it is shown that the new theory originally developed for canopy turbulence recovers much of the earlier roughness results for flume experiments and shallow gravel streams this study is the first to provide such a unifying framework between canopy atmospheric turbulence and shallow gravel stream roughness characterization the broader implication of this study is to support the merger of a wealth of surface roughness characterizations independently developed in nineteenth and twentieth century hydraulics and atmospheric sciences and to establish a connection between roughness formulations across traditionally distinct boundary layer types

evaporation induced 18o and 13c enrichment in lake systems a global perspective on hydrologic balance effects growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time one of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions however endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined as a consequence isotopic researchers are often required to assume values for multiple parameters including temperature of carbonate formation or lake water delta o 18 in order to interpret changes in hydrologic conditions here we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions through integration of multiple large datasets we show that lake carbonate delta o 18 values and the lake waters from which they are derived are often shifted by 10 parts per thousand relative to source waters discharging into the lake the global pattern of delta o 18 and delta c 13 covariation observed in 70 of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where delta o 18 and delta c 13 covariation is absent aridisol pedogenic carbonates show similar isotopic responses to evaporation and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed recent advances in stable isotope research techniques present unprecedented opportunities to overcome the underdetermined nature of stable isotopic data through integration of multiple isotopic proxies including dual element c 13 excess values and clumped isotope temperature estimates we demonstrate the utility of applying these multi proxy approaches to the interpretation of paleohy droclimatic conditions in ancient lake systems understanding past present and future hydroclimatic systems is a global imperative significant progress should be expected as these modern research techniques become more widely applied and integrated with traditional stable isotopic proxies c 2015 elsevier ltd all rights reserved

macroroughness and variations in reach averaged flow resistance in steep mountain streams 1 steep mountain streams typically feature macroroughness elements like large immobile boulders or channel spanning bedforms such as step pool sequences the effects of macroroughness on resistance and flow velocity are not well understood and appropriate field parameters for representing macroroughness in flow velocity equations have not been identified the prediction of flow velocity in rough and steep streams therefore remains challenging we measured flow velocity and several macroroughness parameters i e boulder concentration boulder diameter and protrusion and roughness of longitudinal channel profiles in six reaches of steep mountain streams with plane bed riffle step pool and cascade channel morphologies the between site variations in flow resistance can be explained to a large degree by nondimensionalization of discharge and flow velocity using channel slope and a characteristic roughness length using any of our roughness parameters as the characteristic roughness length this nondimensionalization leads to a similarity collapse of the entire data set the remaining differences in flow resistance among the streams are related to dimensionless measures of macroroughness that describe the concentration of boulders or step density in a reach boulder concentration represents the measure best describing the data and is used in a simple regression equation for flow velocity the predictions were better than predictions by the variable power law equation proposed by ferguson although the regression might not be statistically significant the observed trends suggest that boulder concentration partly explains the residual variance of between site variation of flow resistance

high rate injection is associated with the increase in u s mid continent seismicity an unprecedented increase in earthquakes in the u s mid continent began in 2009 many of these earthquakes have been documented as induced by wastewater injection we examine the relationship between wastewater injection and u s mid continent seismicity using a newly assembled injection well database for the central and eastern united states we find that the entire increase in earthquake rate is associated with fluid injection wells high rate injection wells 300 000 barrels per month are much more likely to be associated with earthquakes than lower rate wells at the scale of our study a well s cumulative injected volume monthly wellhead pressure depth and proximity to crystalline basement do not strongly correlate with earthquake association managing injection rates may be a useful tool to minimize the likelihood of induced earthquakes

the characteristics of turbulence in a shear zone downstream of a channel constriction in a coarse grained forced pool a field based project was initiated to characterize the influence of varying discharge and bed topography along a pool exit slope on the strength of turbulence generated by vortex shedding velocities were measured with an adv downstream of a boulder constriction within a shear zone of a large pool measurements were repeated for four flows that varied from 20 to 50 of bankfull discharge an additional longitudinal profile was conducted along the pool thalweg plots of velocity demonstrate high near bed velocities and turbulence levels in the pools turbulence levels were highest closer to the constriction in the shear zone turbulent kinetic energy decayed in the downstream direction in response to the bed topography and at lower discharges instantaneous velocities are large enough to temporarily lift pebbles at this depth it appears that instantaneous forces created by vortex shedding may play an important role in scouring pools downstream of constrictions the turbulence may also respond to changes in bed topography in a manner that encourages feedbacks among bed topography characteristics of turbulence and sediment transport

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

velocity distribution in compound channel flows by numerical modeling the paper examines the problem of prediction of uniform turbulent flow in a compound channel with the nonlinear k e model this model is capable of predicting the secondary currents caused by the anisotropy of normal turbulent stresses that are important features of the flow in compound channels as they determine the transverse momentum transfer the model is applied to reproduce experimental runs available in the literature the comparison shows that the model predicts with accuracy the distribution of the primary velocity component the secondary circulation and the discharge distribution the numerical results are used to search a subdivision surface between main channel and floodplain on the basis of the flow field and to compare different subdivision surfaces on the basis of the discharge distribution by a simple uniform flow formula the better subdivision surfaces as predicted by the model are the diagonal surface going from the corner between main channel and floodplain to the free surface on

origins of 210 pb 226 ra disequilibria in basalts new insights from the 1978 asal rift eruption 1 there has been much debate as to whether 210pb 226ra disequilibria in young volcanic rocks result from partial melting cumulate interaction or magma degassing here we present new data from basalts erupted in 1978 from ardoukoba volcano in the asal rift the 210pb 226ra t ratios are very low 0 2 to 0 6 and appear to correlate negatively with 226ra 230th invariant 230th 238u and 231pa 235u ratios require similar melting rates porosities and extents for all parental magmas thus the range in 226ra 230th which is negatively correlated with th concentration reflects fractional crystallization over millennia after the magmas were emplaced into the crust this precludes the 210pb deficits from resulting from partial melting instead the 210pb deficits must have formed subsequent to magma differentiation and are interpreted to reflect several decades of magma degassing many young basalts erupted in a variety of tectonic settings are similarly depleted in 210pb with respect to 226ra suggesting that they continuously degas over a period of a few to several decades perhaps reflecting the time required to rise to the surface from deeper reservoirs in some of these basalts gas accumulation leads to the shallowest most evolved and earliest erupting magmas having the highest 210pb 226ra ratios and sometimes 210pb excesses

flow resistance in steep streams an experimental study 1 frequently an assessment of the mean water velocity in a stream is necessary to estimate the discharge associated with a particular flow depth or conversely the mean depth associated with a particular discharge in the absence of a direct measurement of flow velocity a flow resistance approach which establishes the relation between depth and velocity can be applied two approaches have been used in the past traditional approaches based on the use of a resistance coefficient e g darcy weisbach or dimensionless hydraulic geometry approaches to examine if one approach is more appropriate for steep streams data from 31 flume experiments conducted to examine flow resistance in self formed cascade channels were analyzed a dimensionless hydraulic geometry approach developed using at a station data to characterize the q exponent and between site data to characterize the exponent on the channel slope term was more accurate than more traditional approaches the developed relation was similar to the established rational relation v g0 2q0 6s 0 4s0 2 suggesting that the rational relation has merit the approach does not utilize a flow partitioning approach since in steep streams with small relative depths the grains themselves generate form and spill resistance the observation that a single dimensionless hydraulic geometry flow resistance relation can describe measurements across a range of grain sizes and bed slopes 3 21 suggests that steep streams may follow a single scaling relation similar to the regime equations associated with lowland rivers

response of bed surface patchiness to reductions in sediment supply 1 river beds are often arranged into patches of similar grain size and sorting patches can be distinguished into free patches which are zones of sorted material that move freely such as bed load sheets forced patches which are areas of sorting forced by topographic controls and fixed patches of bed material rendered immobile through localized coarsening that remain fairly persistent through time two sets of flume experiments one using bimodal sand rich sediment and the other using unimodal sand free sediment are used to explore how fixed and free patches respond to stepwise reductions in sediment supply at high sediment supply migrating bed load sheets formed even in unimodal sand free sediment yet grain interactions visibly played a central role in their formation in both sets of experiments reductions in supply led to the development of fixed coarse patches which expanded at the expense of finer more mobile patches narrowing the zone of active bed load transport and leading to the eventual disappearance of migrating bed load sheets reductions in sediment supply decreased the migration rate of bed load sheets and increased the spacing between successive sheets one dimensional morphodynamic models of river channel beds generally are not designed to capture the observed variability but should be capable of capturing the time averaged character of the channel when applied to our experiments a 1 d morphodynamic model rte bookagdegnormgravmixpw xls predicted the bed load flux well but overpredicted slope changes and was unable to predict the substantial variability in bed load flux and load grain size because of the migration of mobile patches our results suggest that 1 the distribution of free and fixed patches is primarily a function of sediment supply 2 the dynamics of bed load sheets are primarily scaled by sediment supply 3 channels with reduced sediment supply may inherently be unable to transport sediment uniformly across their width and 4 cross stream variability in shear stress and grain size can produce potentially large errors in width averaged sediment flux calculations

linking spatial patterns of bed surface texture bed mobility and channel hydraulics in a mountain stream to potential spawning substrate for small resident trout abstract in this paper we examined spatial patterns of bed texture bed mobility and channel hydraulics in four reaches of a mountain stream with moderate gradient

flow resistance estimation in mountain rivers examination of the flow resistance of high gradient gravel and boulder bed rivers using data collected in british mountain rivers with slopes of 0 4 4 shows that there are differences in resistance variation between mountain and lowland rivers and that between site variations do not necessarily reflect at a site variations comparison of data with the familiar resistance equation relating the dracy weisbach friction factor to the logarithm of relative submergence shows that the equation tends to overestimate the resistance in uniform flow the equation also tends to underestimate the rate of change of resistance at a site as discharge varies with high gradients the influences of nonuniform channel profile sediment size distribution channel slope and sediment transport are reviewed but the data do not allow any quantification of these effects instead an empirical approach based on the available data is presented allowing the friction factor to be calculated from the relative submergence with an error of up to n25 to n35 a summary of the field data is included

numerical simulation of turbulence and sediment transport of medium sand a model of sand transport in water is produced by combining a turbulence resolving large eddy simulation les with a discrete element model dem prescribing the motion of individual grains of medium sand the momentum effect of each particle on the fluid is calculated at the les cell containing the particle and the fluid velocity and pressure interpolated to each particle center is used to derive fluid force on each particle in the dem eleven numerical experiments are conducted of an initially flat bed of particles the experiments span a range of motion from essentially no motion to vigorous suspension hydraulic roughness is found to increase abruptly at the transition from bed load to suspended load transport suspended sediment extracts momentum from the flow and decreases the rate of shear whereas slightly higher in the flow vertical drag by suspended grains damps turbulence and increases the rate of shear vertical sediment diffusivity and effective particle settling velocity are much smaller than is commonly assumed in suspended sediment models the bed load experiments suggest that saltation by itself is a poor model of bed load sand transport in contrast to expectations from saltation models the peak bed load flux occurs at essentially the same level as the bed and grains move slowly in frequent contact with other grains higher and faster moving bed load grains that can be considered to be in saltation represent a smaller portion of the total flux entrainment of bed load grains occurs in response to fluid penetration of the bed by high vorticity turbulence structures embedded within broader high speed fluid regions referred to as a sweeps or high speed wedges

understanding induced seismicity fluid injection induced seismicity has become increasingly widespread in oil and gas producing areas of the united states 1 3 and western canada it has shelved deep geothermal energy projects in switzerland and the united states 4 and its effects are especially acute in oklahoma where seismic hazard is now approaching the tectonic levels of parts of california unclear in the highly charged debate over expansion of shale gas recovery has been the role of hydraulic fracturing fracking in causing increased levels of induced seismicity opponents to shale gas development have vilified fracking as directly responsible for this increase in seismicity however this purported causal link is not substantiated the predominant view is that triggering in the midwestern united states is principally a result of massive reinjection of energy coproduced wastewaters on page 1406 of this issue bao and eaton 5 identify at least one example of seismicity developed from hydraulic fracturing for shale gas in the alberta basin

gps observed horizontal ground extension at the hutubi china underground gas storage facility and its application to geomechanical modeling for induced seismicity abstract induced earthquakes and ground displacements were seldom reported in relation to gas injection or extraction the hutubi underground gas storage hugs facility is the largest one in china and is also a unique case with both earthquakes and ground displacements detected during multiple cycles of injection and extraction since 9 june 2013 unlike previous studies with a primarily seismological focus here we conducted quantitative analysis on the geomechanics of seismicity induced by the hugs through developing a hydrogeologic framework which systematically integrated geodetic geophysical and geological data first we measured horizontal ground extension and shortening on the order of cm in response to gas injection and extraction of the hugs at depth using a local gps network which was not reported in other regions with induced seismicity second we synthesized a variety of data including seismic reflection profiles a newly acquired local velocity model rock physics measurements well drilling and logging data to build up a 2d geomechanical model for the hugs third based on fully coupled poroelasticity we proposed two methods to optimize the permeability of the upper aquifers as well as the reservoir porosity and permeability with constraints from well level gps and well pressure data numerical simulations using the calibrated 2d model revealed that the horizontal extension due to the reservoir dilation is larger than ground uplift the observed seismicity on faults without hydraulic connections to the gas repository was probably induced by the poroelastic effect of reservoir dilation our study provided a prototype scheme for detecting and characterizing the geomechanical behavior of cyclic fluid injection and extraction in a deep reservoir which would be applicable to other ugs facilities

crustal deformation in the india eurasia collision zone from 25 years of gps measurements the india eurasia collision zone is the largest deforming region on the planet direct measurements of present day deformation from global positioning system gps have the potential to discriminate between competing models of continental tectonics but the increasing spatial resolution and accuracy of observations have only led to increasingly complex realizations of competing models here we present the most complete accurate and up to date velocity field for india eurasia available comprising 2576 velocities measured during 1991 2015 the core of our velocity field is from the crustal movement observation network of china i ii 27 continuous stations observed since 1999 56 campaign stations observed annually during 1998 2007 1000 campaign stations observed in 1999 2001 2004 and 2007 260 continuous stations operating since late 2010 and 2000 campaign stations observed in 2009 2011 2013 and 2015 we process these data and combine the solutions in a consistent reference frame with stations from the global strain rate model compilation then invert for continuous velocity and strain rate fields we update geodetic slip rates for the major faults some vary along strike and find that those along the major tibetan strike slip faults are in good agreement with recent geological estimates the velocity field shows several large undeforming areas strain focused around some major faults areas of diffuse strain and dilation of the high plateau we suggest that a new generation of dynamic models incorporating strength variations and strain weakening mechanisms is required to explain the key observations seismic hazard in much of the region is elevated not just near the major faults

the november 2017 mw 5 5 pohang earthquake a possible case of induced seismicity in south korea the moment magnitude mw 5 5 earthquake that struck south korea in november 2017 was one of the largest and most damaging events in that country over the past century its proximity to an enhanced geothermal system site where high pressure hydraulic injection had been performed during the previous 2 years raises the possibility that this earthquake was anthropogenic we have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks constrain the geometry of this seismic sequence and shed light on its causal factors according to our analysis it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities finally we found that the earthquake transferred static stress to larger nearby faults potentially increasing the seismic hazard in the area

coseismic slip distribution of the 2008 mw 7 9 wenchuan earthquake from joint inversion of gps and insar data on 12 may 2008 the m w 7 9 wenchuan earthquake occurred at the eastern margin of the tibetan plateau along the longmen shan fault based on previous geological and geophysical studies and offset maps from advanced land observing satellite phased array type l band synthetic aperture radar alos palsar data a layered crustal structure and a five segment rupture model are established to study the coseismic deformation of this event using the constrained least squares method a preferred coseismic slip model is derived from global positioning system gps and interferometric synthetic aperture radar insar data in particular the helmert variance component estimation hvce method is used to determine the relative weight ratio between the gps and insar data in contrast to the initial weight ratio 0 752 0 246 0 002 among three type observations gps horizontal gps vertical and insar los displacement the final optimal weight ratio is found to be 0 473 0 279 0 248 and the overall root mean square rms misfit for all three datasets decreases from 9 15 cm without hvce to 5 46 cm with hvce as revealed by the preferred slip the slip changes obviously along the strike direction from southwest to northeast and exhibits four asperities close to hongkou town yuejiashan town beichuan county and nanba town respectively two major asperities are located on the hongkou and beichuan segments with the maximum slip close to 10 m the slips of hongkou yuejiashan and beichuan segments are dominated by the thrust movement with a significant right lateral strike slip component the qingchuan segment experiences a dominant right lateral strike slip with an average magnitude of 1 2 m most of the slip asperities are shallower than 10 km depth except for the southwest part near the hypocenter where the slip may exceed 20 km the seismic moment of the wenchuan earthquake is 8 19 1020 n m m w 7 91 based on the layered crust model which is slightly larger than that using a corresponding homogeneous crust model m w 7 87

a detailed view of the injection induced seismicity in a natural gas reservoir in zigong southwestern sichuan basin china 1 seismicity at a gas reservoir located in the relatively stable sichuan basin china mirrors the injection pressure of unwanted water suggesting that the seismicity is injection induced injection under high pressure on a routine basis began on 9 january 2009 and continued to july 2011 during the injection period over 120 000 m3 of water was pumped under a wellhead pressure of up to 6 2 mpa into the limestone formation of permian 2 45 to 2 55 km beneath the surface the injection induced more than 7000 surface recorded earthquakes including 2 m4 the largest one was ml4 4 20 m3 and more than 100 m2 events data observed by a nearby local seismic network and five temporal stations provide a detailed view of the spatiotemporal distribution of the induced earthquakes most events were limited to depths ranging from 2 5 to 4 km which is consistent with the limestone formation of permian in a map view hypocenters are concentrated in a nnw extended ellipsoidal zone approximately 6 km long and approximately 2 km wide centered approximately at the injection well multisources of evidence such as the shear mechanism pattern of hypocenter distribution and small elevated pore pressure as compared with the least principal stress in the region show that the induced earthquakes occurred as a result of lowering of the effective normal stress on known or unknown preexisting blind faults which are critically loaded under the regional stress field epidemic type aftershock sequence modeling results indicate that injection inducing and earthquake triggering are both important during earlier periods of injection while later periods are dominated by forced injection induced seismicity

earthquakes induced by water injection at 3 km depth within the rongchang gas field chongqing china 1 unwanted water amounting more than 1 million m 3 has been injected intermittently at a pumping pressure of 2 1 2 9 mpa over hydrostatic at 2 6 2 9 km depth within the rongchang gas field western chongqing china since july 1988 the injections have induced more than 32 000 surface recorded earthquakes including 2 of m l 5 14 of m l 4 and more than 100 of m l 3 up until the end of 2006 we examined the epidemic type aftershock sequence etas model and the temporal evolution of several statistics of the earthquake sequence the random component in the etas model can be considered as an indicator of fluid driven activity while the rate of omori law type aftershocks indicates stress triggering of the preceding earthquakes we observed three distinct seismic activity phases that were coincident with different injection periods phase i corresponds to initial injections with low injection rate long time interval and shows a vast majority of omori type events and only 8 externally forced activity phase ii corresponds to a period of high injection rates and shows intense earthquake activity characterized by a high percentage 45 of fluid driven earthquakes phase iii demonstrates decreasing seismicity as a result of a lowering in the injection rate more than 70 of earthquakes occurred randomly over time indicating the dominance of external triggering the physical mechanism that induced the rongchang earthquake sequence was a change in coulomb s failure stress caused by pore pressure diffusion and transformed from seismic slip of preceding earthquakes a pressure increase of 2 1 2 9 mpa at the injection well is more than sufficient to induce failure within the local formations

theoretical development on the effects of changing flow hydraulics on incipient bed load motion 1 several decades of flume and field measurements have indicated that in rough turbulent flows the critical shields stress increases with increasing slope and associated decreasing relative depth this result contradicts the usual consideration of a decreased critical shields value on very steep slopes because of increased gravitational effects however recent studies have demonstrated that these experimental results could be reproduced with a force balance model if the classical logarithmic velocity profile was replaced with a velocity profile that was more compatible with available velocity measurements over gravel beds these measurements indicate the existence of a roughness layer that is a zone of almost constant velocity close to the bed whose properties mean velocity and turbulence depended on the flow s relative depth unfortunately velocity profile measurements for low relative depth associated with steep slopes are scarce and it is still difficult to include such flow properties in a force balance model flow resistance data on the basis of depth average velocity measurements are very common and cover a wide range of slopes and relative depths in this paper these data are used to fit a velocity profile including a roughness layer when used in a force balance model for incipient motion it adequately reproduced a data set composed of 270 critical shields values measured in a flume with near uniform sediments the relevance of this research to field problems is discussed using a data set composed of 92 critical shields stresses obtained from field measurements finally a model is proposed for field applications taking into account the slope effect

influence of relative submergence on spatial variance and form induced stress of gravel bed flows 1 spatial flow variance has a strong control on sediment transport sediment water interface exchange mechanisms and the distribution and behavior of aquatic organisms in rivers thus being able to quantify spatial flow variance and how it varies with different water levels is important for understanding how fluvial processes change during periods of time varying flow in this paper laboratory flume measurements of near bed flow velocity were used to quantify spatial flow variance and form induced stress and their variation with flow submergence within and above the surface of porous gravel beds with differing grain roughness the analysis revealed spatial flow variance was usually four or five times higher within the roughness layer than above a rise in relative submergence resulted typically in a decrease in spatial variance relative to bed shear velocity in streamwise form induced intensity streamwise turbulence intensity and form induced momentum flux both within and above the roughness layer flow submergence had no consistent influence on spatial variance in the vertical flow direction and in reynolds stress form induced stress was significant within the roughness layer more so at shallow depths the greater significance was driven primarily by higher spatial flow variance in time averaged streamwise velocity at these depths the implication is the relative role of momentum transfer mechanisms within the roughness layer and thus sediment water interface exchange processes in rivers will change during periods of time varying flows

decompression and h2o exsolution driven crystallization and fractionation development of a new model for low pressure fractional crystallization in calc alkaline magmatic systems magma ascent decompression induced h2o exsolution and crystallization is now recognized as an important process in hydrous subduction zone magmas during the course of such a process calculations suggest that the ascent rate of a degassing and crystallizing mafic magma will be greater than crystal settling velocities thus any crystals formed as a consequence of volatile exsolution will remain suspended in the magma if the magma erupts before the percentage of suspended crystals reaches the critical crystallinity value for mafic magma 55 vol it will produce the commonly observed crystal rich island arc basalt lava if the magma reaches its critical crystallinity before it erupts then it will stall within the crust extension of compaction experiments on a 55 vol sand karo syrup suspension at different temperatures and liquid viscosities to the likely viscosities of interstitial andesitic to dacitic liquid within such a stalled magma suggest that small amounts up to 10 can be expelled on a time scale of 1 10 years the expelled liquid can create a new intermediate to silicic body of magma that is related to the original mafic magma via fractional crystallization the short time scale for liquid expulsion indicate that decompression induced h2o exsolution and crystallization can be an important mechanism for fractional crystallization based on this assumption a general model of decompression induced crystallization and fractionation is proposed that explains many of the compositional mineralogical and textural features of aleutian and other andesites

robust classification for the joint velocity intermittency structure of turbulent flow over fixed and mobile bedforms two datasets of turbulence velocities collected over different bedform types under contrasting experimental conditions show similarity in terms of velocity intermittency characteristics and suggest a universality to the velocity intermittency structure for flow over bedforms one dataset was obtained by sampling flow over static bedforms in different locations and the other was based on a static position but mobile bedforms a flow classification based on the velocity intermittency behaviour is shown to reveal some differences from that based on an analysis of reynolds stresses boundary layer correlation and turbulent kinetic energy this may be attributed to the intermittency variable which captures the local effect of individual turbulent flow structures locations in the wake region or the outer layer of the flow are both shown to have a velocity intermittency behaviour that departs from that for idealized wakes or outer layer flow because of the superposition of localized flow structures generated by bedforms the combined effect of this yields a velocity intermittency structure unique to bedform flow the use of a time series of a single velocity component highlights the potential power of our approach for field numerical and laboratory studies the further validation of the velocity intermittency method for non idealized flows undertaken here suggests that this technique can be used for flow classification purposes in geomorphology hydraulics meteorology and environmental fluid mechanics 2014 the authors earth surface processes and landforms published by john wiley sons ltd

hydraulic properties of injection formations constrained by surface deformation author s shirzaei m manga m zhai g abstract 2019 the author s wastewater injection over the past decade has increased seismicity in the central usa in some cases accompanied by detectable surface uplift here we use this uplift to constrain subsurface properties and pore pressure evolution we apply an advanced multitemporal interferometric algorithm to 35 synthetic aperture radar images acquired by alos satellite over four years before the 2012 earthquake sequence in east texas where large volumes of wastewater are disposed at depths of 800 m and 1800 m to solve for the hydraulic diffusivity of the injection layers we jointly inverted the injected volume and uplift data considering a poroelastic layered half space we find diffusivity values of 0 3 0 1 m 2 s and 0 7 0 15 m 2 s for shallow and deep injection layers respectively which combined with seismically derived bulk moduli yields permeability values of 5 5 2 6 10 14 m 2 and 1 9 0 25 10 13 m 2 for these layers consistent with permeability range reported for rodessa formation and well test values hydraulic conductivity determines the evolution of pore pressure and thus the origin and location of induced seismicity this study highlights the value of geodetic observations to constrain key hydrogeological properties of injection layers and to monitor the evolution of the subsurface pressure change

three dimensional flow structure around small scale bedforms in a simulated gravel bed environment pebble clusters are common small scale morphological features in gravel bed rivers occupying as much as 10 per cent of the bed surface important links exist between the presence of pebble clusters and the development of flow structures these links are poorly understood at the three dimensional level particularly neglected has been the effect of clusters on the lateral flow characteristics a laboratory study was conducted using a hydraulic flume within which simulated pebble clusters were superimposed onto a plane bed of gravel material high resolution three dimensional flow data were collected above the bed at two different flow depths using an acoustic doppler velocimeter the results present evidence of the importance of lateral flow in the development of turbulent flow structure narrow regions of high lateral and downstream turbulence intensity exist to both sides of clusters and in a three dimensional separation zone in their lee this may indicate the presence of horseshoe type vortical structures analogous to those identified in less hydraulically rough environments however it is likely that these structures are more complicated given the mutual interference of the surrounding medium the lateral flow was also identified as a key component in the upwelling identified by other authors in the lee of pebble clusters the results of the vertical flow analysis confirm the hypothesis that six regions with distinct vertical flow characteristics exist above clusters flow acceleration up the stoss side of the cluster recirculation behind the cluster in the wake region vortex shedding from the pebble crest and shear layer flow reattachment downstream of the cluster upwelling of flow downstream of the point of reattachment and recovery of flow copyright 2001 john wiley sons ltd

identification of a magma chamber in the ghoubbet asal rift djibouti from a magnetotelluric experiment abstract a very broad band 10 3 to 10 4 hz magnetotelluric investigation of the axial zone of the ghoubbet asal rift djibouti has revealed a shallow 2 4 km magma chamber which can be mapped in some detail the suggested roof of the chamber is shallowest very close to the ardoukoba volcano which was built during the november 1978 rifting episode

a 210pb 226ra 230th 238u study of klyuchevskoy and bezymianny volcanoes kamchatka abstract lavas from klyuchevskoy and bezymianny volcanoes kamchatka appear to show a link between the extent of partial melting in their mantle source region and the subsequent degree of fractionation suffered by the magmas during passage through the crust this fractionation may have occurred on timescales significantly less than 1000 years if observed 226 ra excesses largely reflect variable residual porosity in the source melting region unlike most arc lavas those with the highest mgo contents and ba th ratios have the lowest 226 ra excess forward models suggest that those portions of the source which had undergone the greatest addition of u by fluids from the subducting plate also underwent the greatest extents of partial melting at the highest residual porosity at kluchevskoy a change from eruption of high mgo to high al 2 o 3 basaltic andesites around 1945 is reflected in an increase in size of 226 ra excess which seems to require a simultaneous decrease in residual porosity and suggests a rapid changes in the melting regime the eruption of andesites at bezyminanny simultaneous with the eruption of basaltic andesites at klyuchevskoy further suggests that different degree melts produced at differing residual porosity can be formed and extracted from the melt region at the same time thus the melting processes beneath klyuchevskoy and bezyminanny are demonstrably complex they have clearly been influenced by both fluid addition from the subducting plate and extension and decompression beneath the central kamchatka depression finally the 210 pb data are with one or two exceptions in equilibrium with 226 ra suggesting that there was restricted relative magma gas movement in this highly productive magmatic system

is the critical shields stress for incipient sediment motion dependent on channel bed slope data from laboratory flumes and natural streams show that the critical shields stress for initial sediment motion increases with channel slope which indicates that particles of the same size are more stable on steeper slopes this observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force processes that might explain this discrepancy are explored using a simple force balance model including increased drag from channel walls and bed morphology variable friction angles grain emergence flow aeration and changes to the local flow velocity and turbulent fluctuations surprisingly increased drag due to changes in bed morphology does not appear to be the cause of the slope dependency because both the magnitude and trend of the critical shields stress are similar for flume experiments and natural streams and significant variations in bed morphology in flumes is unlikely instead grain emergence and changes in local flow velocity and turbulent fluctuations seem to be responsible for the slope dependency due to the coincident increase in the ratio of bed roughness scale to flow depth i e relative roughness a model for the local velocity within the grain roughness layer is proposed based on a 1 d eddy viscosity with wake mixing in addition the magnitude of near bed turbulent fluctuations is shown to depend on the depth averaged flow velocity and the relative roughness extension of the model to mixed grain sizes indicates that the coarser fraction becomes increasingly difficult to transport on steeper slopes

influence of crustal cumulates on 210pb disequilibria in basalts abstract in historical basalts from a wide range of tectonic settings 210 pb is often found to have an activity deficit relative to its predecessor 226 ra several processes have been hypothesized as causes of 210 pb deficits in basalts in subduction zone and ocean island environments 210 pb deficits have often been attributed to shallow magmatic degassing at mid ocean ridges 210 pb deficits have been inferred to result from mantle melting limiting the time between melt production and eruption to 100 years or less here we present an alternative mechanism for producing 210 pb deficits in magmas by diffusive exchange between a melt and cumulate minerals plagioclase and or clinopyroxene in the crust the deficit in 210 pb develops in response to its decay toward secular equilibrium with 226 ra within the mineral grains decay provides an internal sink for 210 pb that drives continuous diffusive exchange with the melt deficits in 210 pb develop under a broad range of conditions in enriched and depleted melts and during interaction with young or old cumulate minerals the magnitude of the deficit depends mainly on the equilibrium mineral melt partition coefficients for pb and ra and on the melt rock ratio during diffusive interaction and is only weakly dependent on the relative diffusivities of ra and pb in the minerals or the trace element disequilibrium between the melt and cumulate minerals plagioclase in the crust has greater leverage on the 210 pb 226 ra system than any silicate mineral present during mantle melting and is capable of inducing significant 210 pb deficits in the melt even at melt fractions above 50 its influence on the melt is also rapid with a substantial 210 pb deficit developing in less than a year and approaching a steady state value after several decades or less the strong control crustal cumulates are capable of exerting on 210 pb 226 ra fractionation in melts indicates that they may have a significant role in a wide range of tectonic environments and suggests caution in interpreting 210 pb deficits as a signature of mantle melting or as a product of 222 rn degassing

a simple model of 222rn accumulation leading to 210pb excesses in volcanic rocks while most rocks from active volcanoes display 210pb 226ra activity ratios lower than or close to the equilibrium value of 1 several other have ratios much higher than 1 transfer of 222rn by magmatic volatiles has often been advocated to explain both 210pb deficits and excesses we develop here a model to account for 210pb excesses through 222rn accumulation we show that large 210pb excesses can be readily obtained even for moderate ratios of degassing magma over accumulating magma in a closed system model where the 222rn atoms produced by decay of 226ra in the degassing magma are continuously extracted by a gas phase for a given duration of volatile transfer relative 210pb excesses are expected to be much larger than 210pb deficits this model is applied to samples from santorini aegean arc and surtsey iceland both of which show high 210pb 226ra ratios of 6 7 and 2 3 respectively at the time of eruption the agreement with field data suggests that 222rn accumulation leading to 210pb excesses might be a rather common process in zoned magma chambers as well as in individual lava flows and that it can be described by a closed system model

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

unobstructed and obstructed turbulent flow in gravel bed rivers an acoustic doppler velocimeter was used to characterize turbulence in two gravel bed rivers data were collected in unobstructed flow and compared to recent investigations additional data collected in the wake of emergent boulders indicate that mean flow velocity turbulent kinetic energy gradients in the streamwise velocity and reynolds stress downstream from large rocks deviate from unobstructed flow results but similar turbulence patterns are found behind each boulder results of this study are discussed with regard to natural channel design and fish habitat

calculating bed load transport in steep boulder bed channels 1 steep rough channels occupy a large fraction of the total channel length in mountainous regions most sediment mobilized on hillslopes must pass through these streams before reaching lower gradient channels steep channels have wide grain size distributions that are composed of finer more mobile sediment and large rarely mobile grains the large grains can bear a significant portion of the total shear stress and thereby reduce the stress available to move the finer sediment conventional bed load transport equations often overpredict the sediment flux in steep channels by several orders of magnitude we hypothesize that sediment transport equations overpredict the sediment flux because they do not 1 account for the stress borne by rarely mobile grains 2 differentiate between highly and rarely mobile sediment and 3 account for the limited availability of mobile sediment here we modify a conventional bed load transport equation to include these three effects we use measurements of the flow bed properties and sediment flux in a small steep flume to test this equation we supply gravel at a constant rate through fields of regularly spaced immobile spheres and measure the bed coverage by gravel and sphere protrusion the percent of the sphere that protrudes above the gravel deposit for a given sphere spacing the proportion of the bed covered by gravel increases and the sphere protrusion decreases with greater sediment supply thus bed coverage and immobile grain protrusion may serve as proxies for sediment availability in steep rough streams unlike most transport equations that we tested our modified bed load equation predicts sediment fluxes to within an order of magnitude of the measured values our results demonstrate that accurately predicting bed load transport in steep rough streams may require accounting for the effects of local sediment availability coverage by mobile sediment and drag due to rarely mobile particles

effects of partial melting on the uranium decay series distinction between possible partial melting processes using stable incompatible trace elements depends largely on the mass fraction of liquid produced at low degrees of melting less than 5 both incompatible element concentrations and interelement fractionations are greater for batch fractional and accumulated fractional melting than for dynamic or continuous melting at higher degrees of melting uncertainty in initial source composition and small fractionations between incompatible elements make it unlikely that the most realistic melting models batch and dynamic could be discriminated however it is possible for these melting processes to be distinguished by the magnitude of radioactive disequilibria that is produced within the 238u decay series even for durations of partial melting much longer than the half lives of 230th and 226ra both230th 238u and 226ra 230th disequilibria can occur because of differences in the bulk solid liquid partition coefficients for these elements the magnitude of these disequilibria depends on melting process the 230th 232th of a dynamic melt can differ significantly from that of a batch melt and will not necessarily indicate the original 238u 232th of the source if morb is formed by a dynamic melting process then the th u of the upper mantle near ridge axes may be higher than that calculated from the 230th 232th of the basalts

effects of macro scale bed roughness geometry on flow resistance 1 flow field over macro roughness elements as for example in flow conditions such as of steep mountain streams is investigated by means of a theoretical model and a laboratory study with the main aim of understanding the influence of concentration and planimetric disposition of grain roughness on flow resistance a theoretical model for the average velocity distribution profile over a bed with macro roughness elements is developed herein the model is based on a two layer approach which takes into account the displacement of the main flow due to the drag around the roughness the laboratory study is composed of an extensive set of flume experiments in the case of steep slopes and large relative roughness conditions for a given flow discharge and bed slope various experiments have been carried out with different pattern and spacing of the roughness elements constituted by river pebbles application of the theoretical model to the experimental results enables the determination of how flow resistance is affected by the macro roughness in particular it appears that when the concentration of the roughness is within an optimal range flow resistance is maximum

the magnetite crisis in the evolution of arc related magmas and the initial concentration of au ag and cu the association of large au cu ag ore deposits with convergent margins is commonly attributed to the higher content of chalcophile elements in the parental magmas generated at subduction zones compared with mid ocean ridges we present new geochemical data for arc like relatively oxidized mantle derived basalt to rhyolite magmas from the pual ridge and vicinity eastern manus basin which show that the initial abundances of base and precious metals in the parental basalts are similar to those of mid ocean ridge basalt morb the contents of au cu and ag are built up in the evolving pual ridge liquids to levels considerably in excess of those in morb because unlike morb they are not saturated in a sulfide phase which is a consequence of their being more oxidized than morb the behaviour of s during the evolution of the pual ridge magmas is obscured by late stage so2 loss during eruption but we show that it may be inferred by using se as a proxy because this element follows s closely during magmatic evolution except it is not lost during low pressure near sea floor degassing the onset of magnetite fractionation at 60 wt sio2 and an mg number of 40 is accompanied by an abrupt decrease in the contents of au cu and ag previously attributed to separation of cu au rich fluid which is also shown by se implying that magnetite fractionation triggers sulfide saturation petrological modelling reveals that the amount of magnetite fractionation involved is sufficient to convert most of the s originally dissolved in the magma as sulfate so42 to sulfide s2 triggering saturation in a cu rich sulfide phase tentatively identified as bornite cu5fes4 this sulfide phase sequesters au and ag elements with the same valence as cu in sulfides but not other potentially chalcophile elements such as ni re and pt which suggests that the phase is crystalline rather than an immiscible sulfide melt the relatively high contents of cu and au characteristic of evolved convergent margin magmas requires no enrichment from subducted material instead the association of major cu au deposits with convergent margin magmatism results specifically from the process of magmatic evolution under oxidizing conditions this same property also leads to early magnetite fractionation triggering the abrupt saturation in the cu rich sulfide hence the easily recognizable trend of magmatic evolution under oxidizing conditions i e the sharp drop in chalcophile element concentrations may be an exploration guide to economic au ag cu provinces or a crucial pre enrichment step in the formation of such deposits the decrease in p2o5 and sr at the same stage in the fractionation sequence 60 wt sio2 indicates that saturation in apatite is concomitant with magnetite sulfide saturation in the eastern manus basin

effects of bed forms and large protruding grains on near bed flow hydraulics in low relative submergence conditions in mountain rivers bedforms large relatively immobile grains and bed texture and topographic variability can significantly alter local and reach averaged flow characteristics the low relative submergence of large immobile grains causes highly three dimensional flow fields that may not be represented by traditional shear stress flow velocity and turbulence intensity equations to explore the influence of large protruding grains and bedforms on flow properties we conducted a set of experiments in which we varied the relative submergence while holding the sediment transport capacity and upstream sediment supply constant flow and bed measurements were conducted at the beginning and end of each experiment to account for the absence or presence of bedforms respectively detailed information on the flow was obtained by combining our measurements with a 3d numerical model commonly used velocity profile equations only performed well at the reach scale when shallow flow effects and the roughness length of the relatively mobile sediment were considered however at the local scale large deviations from these profiles were observed and simple methods to estimate the spatial distribution of near bed shear stresses are likely to be inaccurate zones of high turbulent kinetic energy occurred near the water surface and were largely controlled by the immobile grains and plunging flow the reach averaged shear stress did not correlate to depth or slope as commonly assumed but instead was controlled by the relative boulder submergence and degree of plunging flow for accurate flow predictions in mountain rivers the effects of bedforms and large boulders must be considered

minimum speed limit for ocean ridge magmatism from 210pb 226ra 230th disequilibria although 70 per cent of global crustal magmatism occurs at mid ocean ridges where the heat budget controls crustal structure hydrothermal activity and a vibrant biosphere the tempo of magmatic inputs in these regions remains poorly understood such timescales can be assessed however with natural radioactive decay chain nuclides because chemical disruption to secular equilibrium systems initiates parent daughter disequilibria which re equilibrate by the shorter half life in a pair here we use 210pb 226ra 230th radioactive disequilibria and other geochemical attributes in oceanic basalts less than 20 years old to infer that melts of the earth s mantle can be transported accumulated and erupted in a few decades this implies that magmatic conditions can fluctuate rapidly at ridge volcanoes 210pb deficits of up to 15 per cent relative to 226ra occur in normal mid ocean ridge basalts with the largest deficits in the most magnesium rich lavas the 22 year half life of 210pb requires very recent fractionation of these two uranium series nuclides relationships between 210pb deficits 226ra 230th activity ratios and compatible trace element ratios preclude crustal magma differentiation or daughter isotope degassing as the main causes for the signal a mantle melting model can simulate observed disequilibria but preservation requires a subsequent mechanism to transport melt rapidly the likelihood of magmatic disequilibria occurring before melt enters shallow crustal magma bodies also limits differentiation and heat replenishment timescales to decades at the localities studied

validation of a three dimensional numerical code in the simulation of pseudo natural meandering flows validation of a three dimensional finite volume code solving the navier stokes equations with the standard k epsilon turbulence model is conducted using a high quality and high spatial resolution data set the data set was collected from a large scale meandering channel with a self formed fixed bed and comprises detailed bed profiling and laser doppler anemometer velocity measurements comparisons of the computed primary and secondary velocities are made with those observed and it is found that the lateral momentum transfer is generally under predicted at the apices this results in the predicted position of the primary velocity maximum having a bias towards the channel center compared to the position where it has been measured using a simplified two zone roughness distribution whereby a separate roughness height was prescribed for the channel center and channel sides relative to a single distributed roughness height generally led to a slightly improved longitudinal velocity distribution the higher velocities were located nearer to the outside of the bend improving both the free surface calculation and scheme for discretization of the convection terms led to no appreciable difference in the computed velocity distributions a more detailed study involving turbulence measurements and bed form height distribution should discriminate whether using distributed roughness height is a precursor to using an anisotropic turbulence representation for the accurate prediction of three dimensional river flows

seismotectonics of the 2013 lushan mw 6 7 earthquake inversion tectonics in the eastern margin of the tibetan plateau on 20 april 2013 an unexpected mw 6 7 earthquake occurred in lushan county at the southern longmen shan the eastern margin of the tibetan plateau a high resolution seismic reflection profile was combined with near surface geological data earthquake relocation and geodetic measurements and a recent deep artificial seismic reflection profile to identify the active fault and seismotectonics of this earthquake three dimensional imaging of the aftershocks was used to identify two planar faults that together form a y shape f1 and f2 seismic interpretations suggest that fault f1 did not break through the overlying mesozoic and cenozoic rocks and is a typical blind fault geodetic measurements suggest that the coseismic deformation is consistent with the geometry and kinematics of shear fault bend folding deep seismic data indicate the syndepositional nature of fault f1 a preexisting normal fault older than the triassic which underwent positive inversion tectonics during the late cenozoic a thrust fault f3 converges with f1 at a depth of approximately 12 km with an accumulated slip 3 6 km this 2013 lushan earthquake triggered by blind faults is a hidden earthquake blind and reactivated faults increase the potential risk and uncertainty related to earthquakes in the eastern margin of the tibetan plateau

sediment supply and the development of the coarse surface layer in gravel bedded rivers the bed surface of most gravel rivers is considerably coarser than the sub surface or the gravel load transported over it a phenomenon affecting river dynamics morphology and ecology the coarse surface layer often called an armour or pavement has been attributed to an inherent tendency for small grains to settle between larger ones during active transport of all sizes1 2 and to selective erosion or trapping of finer particles when the coarse grains are relatively immobile3 4 where bedload supply is cut off below dams selective erosion causes coarsening5 6 using a simple quantitative model we propose that surface coarsening develops in gravel bedded rivers when local bedload supply from upstream is less than the ability of the flow to transport that load we present laboratory results which support this hypothesis and show that supply reduction causes changes in bedforms and progressive confinement of active bedload transport to a narrow band of finer bed surface bordered by a coarse less active bed it may therefore be possible to relate the degree of river bed surface coarsening to sediment supply resulting from land use

spectral analysis of turbulent flow and suspended sediment transport over fixed dunes laboratory measurements of turbulent fluctuations in velocity and suspended sediment concentration were obtained synchronously over fixed two dimensional dunes in a sediment starved flow contour maps of turbulent flow parameters demonstrate that the flow separation cell and a perturbed shear layer are the main sources of turbulence production and that the distribution of suspended sediment is controlled by spatially dependent macro turbulent flow structures spectral analysis reveals that peak spectral energies generally occur at 1 2 hz for the stream wise velocity component and 2 4 hz for the cross stream and vertical velocity components spectra show larger and better defined energy peaks near the shear layer peak spectral energies for suspended sediment concentration occur near 1 hz throughout the flow squared coherency values for cospectral analysis of velocity and sediment concentration are insignificant integral timescales for velocity range from 0 20 s for the streamwise component to 0 06 s for the cross stream and vertical components integral length scales for velocity range from 0 065 to 0 135 m for the streamwise component which is comparable to flow depth and from 0 020 to 0 030 m for the crossstream and vertical components which is comparable to dune height for suspended sediment concentration integral timescales and length scales are similar to the streamwise velocity component

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

magma differentiation rates from 226ra 230th and the size and power output of magma chambers we present a mathematical model for the evolution of the 226ra 230th activity ratio during simultaneous fractional crystallization and ageing of magma the model is applied to published data for four volcanic suites that are independently known to have evolved by fractional crystallization these are tholeiitic basalt from ardoukoba djibouti morb from the east pacific rise alkali basalt to mugearite from vestmannaeyjar iceland and basaltic andesites from miyakejima izu bonin arc in all cases 226ra 230th correlates with indices of fractional crystallization such as th and the data fall close to model curves of constant fractional crystallization rate the best fit rates vary from 2 to 6 10 4 yr 1 consequently the time required to generate moderately evolved magmas f 0 7 is of the order of 500 to 1500 yrs and closed magma chambers will have lifetimes of 1700 to 5000 yrs these rates and timescales are argued to depend principally on the specific power output i e power output per unit volume of the magma chambers that are the sites of fractional crystallization equating the heat flux at the epr to the heat flux from the sub axial magma chamber that evolves at a rate of ca 3 10 4 yr 1 implies that the magma body is a sill of ca 100 m thickness a value which coincides with independent estimates from seismology the similarity of the four inferred differentiation rates suggests that the specific power output of shallow magma chambers in a range of tectonic settings covers a similarly narrow range of ca 10 to 50 mw km 3 their differentiation rates are some two orders of magnitude slower than that of the basaltic makaopuhi lava lake hawaii that cooled to the atmosphere this is consistent with the two orders of magnitude difference in heat flux between makaopuhi and the east pacific rise 226ra 230th data for magma suites related by fractional crystallization allow the magma differentiation rate to be estimated and from this the thermal budget of the magma chamber addressed and where an independent measurement of heat flux exists to place constraints on the size of the magma chamber such results have the potential to constrain the likely timescale and size of future eruptions of evolved magmas

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

turbulent flow over three dimensional dunes 2 fluid and bed stresses 1 dunes formed in response to fluid flow exert a total boundary stress on the fluid that is made up of form drag and skin friction the latter of which is generally considered important for predicting sediment transport and dune evolution previous research has used various methods to estimate the total stress and its subcomponents with recent work suggesting the application of a spatial average to the equations of motion a complete three dimensional 3 d form of this analysis is derived and applied to recent measurements of turbulent open channel flow over 3 d dunes spatial averages of reynolds shear stresses over 3 d dunes cannot be used to predict total boundary shear stress however estimations of total boundary shear stress from the spatially averaged equations of motion agree with not only the sum of form drag and skin friction but also the direct measurements of average free surface slope form induced stresses from secondary circulations augment the relatively low reynolds shear stresses over the 3 d dunes these low turbulence levels have ramifications for sediment transport predictions in that use of the total boundary shear stress in prediction of sediment transport over 3 d dunes must account for these low turbulence levels so as not to overpredict transport rates

when does bedload transport begin in steep boulder bed streams the paper presents the results of field measurements of critical conditions for bedload motion conducted in the rio cordon a steep boulder bed stream in the italian alps under conditions of high reynolds numbers and low relative submergence poorly explored before two methods have been used to determine threshold of motion the displacement of marked clasts and the flow competence approach which uses the largest grain size diameter transported by each flood event the high values of confirm the great relevance of non bedload effective shear stresses in step pool streams given by the additional form drag associated with this morphology relative submergence effects on the dimensionless critical shear stress have been quantified by considering the relative submergence ratio rh d84 and the major effect of relative size on the mobility of each particle in steep widely graded bed mixtures has been evaluated finally the dimensionless critical unit discharge has also been adopted in the regression equations as the critical hydraulic parameter because it may represent an easier parameter to use than the critical shear stress for steep rough mountain rivers copyright 2006 john wiley sons ltd

decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano caldera forming volcanic eruptions are low frequency highimpact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days with devastating effects on local and global scales1 because no such eruption has been monitored during its long build up phase the precursor phenomena are not well understood geophysical signals obtained during recent episodes of unrest at calderas such as yellowstone usa and campi flegrei italy are difficult to interpret and the conditions necessary for large eruptions are poorly constrained2 3 here we present a study of pre eruptive magmatic processes and their timescales using chemically zoned crystals from the minoan caldera formingeruption of santorini volcano greece4 which occurred in the late 1600s bc the results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption5 6 despite the large volume of erupted magma4 40 60 cubic kilometres and the 18 000 year gestation period between the minoan eruption and the previous major eruption most crystals in the minoan magma record processes that occurred less than about 100 years before the eruption recharge of the magma reservoir by large volumes of silicic magma and some mafic magma occurred during the century before eruption and mixing between different silicicmagmabatches was still taking place during the final months final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period with major growth phases immediately before eruption these observations have implications for the monitoring of long dormant but potentially active caldera systems

prediction of sediment transport in step pool channels 1 in mountainous drainage networks sediment mobilized on hillslopes must first pass through steep streams before reaching lower gradient channels the bed of steep channels is typically composed of large relatively immobile boulders and finer more mobile gravel most sediment transport equations overpredict sediment flux in steep streams by several orders of magnitude because they do not account for the stress borne by immobile grains and the limited availability of the more mobile sediment we previously developed and tested in flume experiments a sediment transport equation that accounts for these two effects here we modify the parker 1990 bed load equation to include the resistance borne by steps and selective transport of the relatively mobile sediment using a range of hiding functions we test a number of resistance equations and hiding functions combined with our modified and the original parker equations against measured flow and sediment transport in three steep channels our modified sediment transport equation generally predicts the transported sediment volumes to within an order of magnitude of the measured values whereas the unmodified equations do not the most accurate sediment flux predictions were obtained from using our modified equation combined with a hiding function that calculates highly selective transport of the relatively mobile sediment furthermore this hiding function has a critical shields stress that is similar to those reported for lower gradient channels the effects of the immobile steps on flow and sediment transport are not adequately captured by simply increasing the critical shields stress to values reported in steep streams

reservoir evaluation of the lower silurian longmaxi formation shale gas in the southern sichuan basin of china abstract the lower silurian longmaxi formation the palaeozoic is organic rich black shale in the southern sichuan basin the yangtze plate of china this study analyses the lateral extent and thickness burial depth total organic carbon content and thermal maturity of the longmaxi formation black shale as the key features of the shale gas reservoir the thickness of the black shale ranges from 10 to 170 m the thickest reservoir is located in changning naxi yongchuan region the toc of the shale at the bottom of the formation 50 m thickness is above 2 0 the lateral distribution of toc varies with the lateral distribution of thickness with the maximum toc in the gongxian luzhou yongchuan region the burial depth ranges from 2000 to 4500 m the shale is thermally over mature the evaluation of reservoir characteristics indicates that the longmaxi formation has conditions appropriate for shale gas accumulation and thus resource potential in the southern sichuan basin of china the objective of this preliminary evaluation of the reservoir characteristics is to locate potential areas favourable for exploration the most favourable areas are defined here as those where the thickness of black shale is more than 100 m and the burial depth is less than 3000 m these cover approximately 12 600 km 2 the most favourable areas which cover an area of approximately 5100 km 2 are located in the northeast luzhou region

subsidence at the geysers geothermal field n california from a comparison of gps and leveling surveys between 1994 and 1996 three gps surveys were conducted in the geysers region of northern california our aim was to constrain models of the stresses and strains induced by geothermal power production in that region each survey spanned the geysers geothermal field and consisted of typically 40 monuments these monuments had been previously employed in a series of first order leveling surveys during the 1970 s this earlier study had determined that the geysers region was subsiding with a maximum rate of 0 048 0 0055 m yr between 1973 and 1977 in order to be able to directly compare the leveling and gps surveys we transform them to the same reference frame using the geoid 96 geoid model for the period 1977 1996 we determine a maximum susbsidence rate of 0 047 0 002 m yr we then model this subsidence using a series of point sources of contraction and find their optimal configuration by applying the random cost method and the f test the minimum volume strain that we find consistent with this subsidence is approximately 5 10 4 such a strain cannot be explained by a thermoelastic mechanism but does seem to be consistent with poroelastic deformation and a quasi static reservoir bulk modulus k of 3 6 109 pa