four decades of winter mass balance of vernagtferner and hintereisferner austria methodology and results in this study long term series of winter mass balances from two neighbouring glaciers in the southern oetztal alps austria i e hintereisferner and vernagtferner are analyzed with respect to the methods used in their determination for this purpose 1 some basic data of field surveys are presented 2 the influence of different temporal systems is discussed and 3 the profile contour and a model method based on energy balance ablation modelling and measured net mass balance are discussed with respect to the reliability of the resulting series the main findings of the investigations are 1 the winter mass balance series for hintereisferner and vernagtferner as determined with all applied methods result in a reliable climatologic average of 1000 100 mm w e 2 when using the profile method different spatial integration approaches are quite sensitive to the altitudinal coverage and the spatial pattern of observations 3 the error of the model method occurs randomly whereas contour as well as profile method errors are more systematic 4 filtered time series from the two glaciers show similar tendencies for the last three decades

evidence for an earthquake cycle in nw outer himalaya near 78 e longitude from precision levelling observations a levelling line along the saharanpur dehradun mussoorie highway crosses the nw outer himalaya the line has been surveyed over most parts of its length several times at irregular intervals since 1861 the observations show that there was coseismic uplift along the line during the great kangra earthquake of 1905 but most benchmarks have started subsiding in the decades following the earthquake this is seen as evidence that the upper crust along and adjoining the levelling line experiences a cyclic process of strain accumulation and release in great earthquakes

a snow transport model for complex terrain as part of the winter environment in middle and high latitude regions the interactions between wind vegetation topography and snowfall produce snow covers of non uniform depth and snow water equivalent distribution a physically based numerical snow transport model snowtran 3d is developed and used to simulate this three dimensional snow depth evolution over topographically variable terrain the mass transport model includes processes related to vegetation snow holding capacity topographic modification of wind speeds snow cover shear strength wind induced surface shear stress snow transport resulting from saltation and suspension snow accumulation and erosion and sublimation of the blowing and drifting snow the model simulates the cold season evolution of snow depth distribution when forced with inputs of vegetation type and topography and atmospheric foreings of air temperature humidity wind speed and direction and precipitation model outputs include the spatial and temporal evolution of snow depth resulting from variations in precipitation saltation and suspension transport and sublimation using 4 years of snow depth distribution observations from the foothills north of the brooks range in arctic alaska the model is found to simulate closely the observed snow depth distribution patterns and the interannual variability

pattern recognition of air photographs for estimation of snow reserves a certain snow covered area determined from air photographs in different years can contain different volumes of snow the pattern recognition of snow fields reveals whether the snow reserves are relatively high or low for the given snow coverage it also signals a short terra increase of the snow covered area by summer snowfall

cupri observations of persistence asymmetry reversals in up down vertical type i echoes from the equatorial electro jet above alcântara brazil high resolution vertical radar measurements of the equatorial electrojet above alc ntara brazil were made with the cornell university portable radar interferometer cupri as part of the guara dip equator campaign type i spectra obtained from the main body of the electrojet during strong daytime conditions show a preponderance of upward phase velocities as a function of time however the data from a few kilometers higher show a persistence of downward phase velocities this reversal in sign of the most persistent type i peak occurs regularly in our data whenever the electrojet is strongly driven the persistence of upward phase velocities is similar to that seen earlier at jicamarca but the reversal in sign of the dominating mode has not been previously observed nor is it consistent with current electrojet theories another unexpected result from the alc ntara data set is that the absolute values of the phase velocities of the type i spectra peaks decrease with altitude this is through a region where the temperature and hence the acoustic velocity should be increasing with altitude hence the saturation of the type i peak phase velocities is not just a simple function of the acoustic velocity

temporal observations of a seasonal snowpack using upward looking gpr an increase of the spatial and temporal resolution of snowpack measurements in alpine or arctic regions will improve the predictability of flood and avalanche hazards and increase the spatial validity of snowpack simulation models in the winter season 2009 we installed a ground penetrating radar gpr system beneath the snowpack to measure snowpack conditions above the antennas in comparison with modulated frequency systems gpr systems consist of a much simpler technology are commercially available and therefore are cheaper the radar observed the temporal alternation of the snow height over more than 2 5 months the presented data showed that with moved antennas it is possible to record the snow height with an uncertainty of less than 8 in comparison with the probed snow depth three persistent melt crusts which formed at the snow surface and were buried by further new snow events were used as reflecting tracers to follow the snow cover evolution and to determine the strain rates of underlaying layers between adjacent measurements the height in two way travel time of each layer changed over time which is a cumulative effect of settlement and variation of wave speed in response to densification and liquid water content the infiltration of liquid water with depth during melt processes was clearly observed during one event all recorded reflections appeared in concordance with the physical principles e g in phase structure and one can assume that distinct density steps above a certain threshold result in reflections in the radargram the accuracy of the used impulse radar system in determining the snow water equivalent is in good agreement with previous studies which used continuous wave radar systems the results of this pilot study encourage further investigations with radar measurements using the described test arrangement on a daily basis for continuous destruction free monitoring of the snow cover

an analysis of snow cover patterns in a small alpine catchment snow cover patterns in a 9 4 km2 basin in the austrian alps are examined during spring and summer 1989 digital mono plotting from oblique aerophotographs is used for mapping on the basis of a square grid with 25 m spacing snow cover as mapped during nine surveys is analysed as a function of elevation and slope during winter conditions the snow cover is found to be much better related to these terrain features than during the late ablation period

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

high resolution radar measurements of turbulent structure in the equatorial electrojet observations of the equatorial electrojet were made with unprecedented altitude resolution at the jicamarca radio observatory in january 1990 we obtained high quality doppler spectra with 250 m and sometimes better altitude resolution at heights from 95 to 120 km during the daytime and early evening with the large 50 mhz radar this resolution and coverage revealed a richness of dynamics and structure not previously appreciated a structure that is sometimes reminiscent of vhf radar maps of equatorial spread f albeit at smaller primary scale sizes individual scattering centers sometimes appear to drift in large swirls over many kilometers in altitude maintaining their identity for times occasionally as long as a minute or two on the other hand we also see rapid variations with altitude a kilometer or less and time a few seconds or less in the doppler spectra and signal power

imaging spread f structures using gps observations at alcântara brazil during october 1994 a dual frequency gps receiver was operated in alc ntara brazil at the same site where the cornell university portable radar interferometer cupri was performing spread f measurements for an ongoing rocket campaign we present data for two nights during which several spread f plumes drifted through the field of view of cupri fluctuations in the total electron content tec measured with the gps receiver were correlated with those plumes we define a roughness measure from a specialized high frequency filter plots of roughness in a magnetic longitude versus time space show initially low activity followed by regions of dramatic localized onsets and a slower subsequent decline features in the roughness image are well correlated with plumes in the cupri backscatter power map

distributed snow process modelling an image processing approach an approach to spatially distribute a snow process model by segmenting images of land cover terrain and snow properties is reported a small 1 7 ha study area with an existing database was selected for this preliminary evaluation the methodology was carried out over a relatively flat valley bottom at camp grayling michigan meteorological measurements on two sides of the area showed only small differences so uniform meteorological variables were assumed over the site initial snow cover conditions were reconstructed and were distributed over the area using snow maps and sparse snow pit measurements one metre resolution terrain soil vegetation and snow type maps were individually processed into class maps these layers were then combined to produce a segmented class map where the attributes from the data layers were known for each class a one dimensional model of snow processes was run for each class then the results were mapped back into images shallow snow conditions provided high sensitivity of ablation patterns to meteorological conditions over a 72 h period the model performance was assessed by comparing predicted and observed ablation patterns the error in total snow covered area was less than 9 however the location errors were greater predicted snow where no snow was observed and observed snow where no snow was predicted extensive error analysis was not justified because of the lack of multiple point measurements of snow properties

homogenization of long term mass balance time series the re analysis of long term mass balance time series is important to provide bias corrected mass balance data for climate change impact studies a method to homogenize time series of compre hensive mass balance monitoring programmes is presented and applied to the nearly 50 year mass balance records of griesgletscher and silvrettagletscher switzerland using a distributed mass balance model in daily resolution we correct the mass balance data for varying observation dates direct point measurements are combined with independent geodetic mass changes a prerequisite for a thorough homogenization of mass balance records differences between mass balance evaluated in the hydro logical year or according to the measurement period and the stratigraphic system are analyzed and may be up to 0 5 m w e a 1 cumulative mass balance of both glaciers based on the glaciological method generally agrees well with geodetic mass change on the investigated glaciers however for silvretta gletscher a significant bias of 0 37 m w e a 1 has been detected and corrected for since 1994

on interseismic elevation changes observed near 75 5 e longitude in the nw himalaya abstract we interpret in this article the available observations of interseismic elevation changes along the pathankot dalhousie leveling line near 75 5 e longitude in the nw himalaya we find the data consistent with the view that the major earthquakes of this section of the himalayan convergent plate margin may occur in a manner similar to that inferred for subduction zones along the pacific rim in both cases the main thrust zone mtz a dipwise section of the plate boundary fault pbf which ruptures during major earthquakes is locked in the interseismic period and the overlying rocks experience downdip drag due to subduction of underlying rocks at the local plate convergence rate we estimate that the mtz may have a downdip width of only 25 km in the vicinity of the leveling line we estimate also that in the current interseismic period enough strain may have accumulated already for the next major earthquake of the region

rupture parameters of the 1999 chamoli earthquake in garhwal himalaya constraints from aftershocks and change in failure stress abstract a positive correlation between areas of increased coulomb stress changes induced by an earthquake and the spatial distribution in the occurrence of aftershocks have been reported in recent years we consider such a correlation between the aftershocks of march 29 1999 chamoli earthquake ms 6 6 that occurred in the garhwal himalaya india and the mainshock induced coulomb stresses to constrain some of the rupture parameters of the mainshock most of the aftershocks occurred above and near the updip edge of the rupture implying reactivation of pre existing thrust fault of the himalayan wedge the 15 12 km2 rupture appears to be lying above the detachment the plate boundary fault between the underthrusting indian shield rocks and the himalayan wedge rocks in the basement thrust front btf zone

a close ridge small scale atmospheric flow field and its influence on snow accumulation the rough steep and complex terrain in the alpine environment causes a variety of flow patterns such as blocking speed up or flow separation which influence precipitation snow deposition and ultimately snow distribution on the ground cloud terrain interactions flow particle interactions and snow transport affect snow accumulation patterns but the relative importance of these processes is not fully understood in particular in complex mountainous terrain a unique combination of measurements and model simulations is used in a local case study during a two day snowfall event to demonstrate the current understanding of snow accumulation in very steep alpine terrain doppler wind lidar measurements show an eddy like structure on the leeward side of the sattelhorn ridge in the dischma valley near davos switzerland which could partly be replicated by advanced regional prediction system arps flow simulations snow deposition measurements with a terrestrial laser scanner tls show a complex deposition pattern which is only partially captured by alpine3d deposition simulations driven by the arps flow fields this shows that additional processes such as avalanches may play a role or that a more refined simulation of flow or flow particle interactions is required to fully understand snow distribution in very steep mountainous terrain

oblique convergence and slip partitioning in the nw himalaya implications from gps measurements we report gps measurements of crustal deformation across the kashmir himalaya we combined these results with the published results of gps measurements from the karakoram fault system and suggest that in the kashmir himalaya the motion between the southern tibet and india plate is oblique with respect to the structural trend we estimated this almost north south oblique motion to be 17 2 mm yr which is partitioned between dextral motion of 5 2 mm yr on the karakoram fault system and oblique motion of 13 6 1 mm yr with an azimuth of n198 e in the northwest southeast trending kashmir himalayan frontal arc thus the partitioning of the india southern tibet oblique motion is partial in the kashmir himalayan frontal arc however in the neighboring nepal himalaya there is no partitioning the entire india southern tibet motion of 19 20 mm yr is arc normal and is accommodated entirely in the himalayan frontal arc the convergence rate in the kashmir frontal himalaya is about 25 less than that in the nepal himalayan region however here the karakoram fault system accommodates about 20 of the southern tibet and indian plate convergence and marks the northern extent of the nw himalayan arc sliver the kaurik chango rift a north south oriented seismically active cross wedge transtensional fault appears to divide the sliver in two parts causing varying translatory motion on the karakoram fault on either side of the kaurik chango rift

cupri observations of the east west power asymmetry in oblique type i echoes from the equatorial electrojet above alcântara brazil radar observations of the equatorial electrojet at oblique incidence made by the cornell university portable radar interferometer cupri from alc ntara brazil show the same east west asymmetry in the echo strength seen previously at jicamarca peru namely type i echoes from the west are stronger than those from the east balsley 1965 one early theory attributed the results at jicamarca to topographical asymmetries with the andes mountains to the east and the pacific ocean to the west ierkic et al 1980 however the lack of comparable topographical features at alc ntara now implies that this postulate is no longer tenable other proposed theories are then examined but none has so far been found to be fully consistent with both the cupri and the jicamarca data

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

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

distributed mass balance modelling on two neighbouring glaciers in ortles cevedale italy from 2004 to 2009 a 6 year application of an enhanced temperature index mass balance model to careser and la mare glaciers eastern italian alps is presented the two glaciers exhibit very different characteristics and a comprehensive dataset of distributed mass balance measurements was used to test the model performance the model was run using meteorological data acquired outside the glaciers the work was focused on two main aspects 1 the development of a morphological redistribution procedure for snow and 2 the comparison of three different melt algorithms proposed in the literature the results show that the simple method proposed for snow redistribution can greatly improve simulation of winter balance and further improvements would be achievable by collecting data on inaccessible and high altitude areas all three melt formulations displayed a good skill level and very similar results in modelling the mass balance distribution over glacier areas with slightly better results from a multiplicative algorithm in capturing the vertical balance gradient the simulation errors are related to aspect and elevation and tend to be spatially aggregated some assumptions concerning the spatial and temporal distribution of air temperature and incoming solar radiation although reasonable and widely used in the literature may be responsible for this aggregation hence there is a need to further investigate the processes that regulate the distribution of melt energy and that appear to control the current deglaciation phase in this area

snow accumulation distribution inferred from time lapse photography and simple modelling the spatial and temporal distribution of snow accumulation is complex and significantly influences the hydrological characteristics of mountain catchments many snow redistribution processes such as avalanching slushflow or wind drift are controlled by topography but their modelling remains challenging in situ measurements of snow accumulation are laborious and generally have a coarse spatial or temporal resolution in this respect time lapse photography shows itself as a powerful tool for collecting information at relatively low cost and without the need for direct field access in this paper the snow accumulation distribution of an alpine catchment is inferred by adjusting a simple snow accumulation model combined with a temperature index melt model to match the modelled melt out pattern evolution to the pattern monitored during an ablation season through terrestrial oblique photography the comparison of the resulting end of winter snow water equivalent distribution with direct measurements shows that the achieved accuracy is comparable with that obtained with an inverse distance interpolation of the point measurements on average over the ablation season the observed melt out pattern can be reproduced correctly in 93 of the area visible from the fixed camera the relations between inferred snow accumulation distribution and topographic variables indicate large scatter however a significant correlation with local slope is found and terrain curvature is detected as a factor limiting the maximal snow accumulation copyright 2010 john wiley sons ltd

measurements and one dimensional model calculations of snow transport over a mountain ridge wind transport of snow can cause an additional snow load on leeward slopes which often has a considerable influence on avalanche danger for a quantitative assessment of this process a model is proposed which calculates the snow transport over a two dimensional mountain ridge based on input measurements of wind speed and precipitation since the topography is idealized the model is focused on the snow mass that is transported over the ridge and no statements are made about the exact snow distribution over the slopes three transport modes are distinguished snow transport in saltation snow transport in suspension and preferential deposition of precipitation suspension is modelled with a one dimensional diffusion equation and for the saltation layer a newly developed model based on the microscale physical processes is implemented the effect of speed up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge advective effects are taken into account in a parameterization of the turbulent shear stress profile the model is compared with measurements taken at the experimental snowdrift site gaudergrat in the parsenn area switzerland and good agreement is obtained between calculated and measured results

estimating glacier snow accumulation from backward calculation of melt and snowline tracking estimating precipitation to determine accumulation is challenging we present a method that combines melt modelling and snowline tracking to determine winter glacier snow accumulation along snowlines the method assumes that the net accumulation is zero on the transient snowlines and the maximum winter accumulation at the snowline can be calculated backwards with a temperature index melt model to verify the method the accumulation model is applied for the year 2004 on storglaciaren sweden for which extensive meteorological and mass balance data are available the measured mean snowline accumulation is 0 94 0 10 m w e for 2004 modelled accumulation using backward melt modelling at the same snowlines is 0 82 0 25 m w e the accumulation model is also compared with an often used linear regression accumulation model which yields a mean snowline accumulation of 1 02 0 38 m w e the reduction in standard error from 0 38 m w e to 0 25 m w e shows that the backward melt modelling applied at snowlines can provide a better spatial representation of the accumulation pattern than the regression model importantly the applied method requires no field measurements of accumulation during the winter and snowlines can be readily traced in remotely sensed images

experimental investigation of dielectric properties of seasonal snow at field observatories in the northwest himalaya radio echo sounding techniques are very useful for fast profiling of seasonal snowpack ground penetrating radar gpr is used widely for various cryospheric applications such as snow glacier depth estimation snow layer identification and snow water equivalent assessment the dielectric constant of snow is an important input parameter for the acquisition and interpretation of gpr data from the snowpack in this study snow dielectric constant was measured along with physical properties of snow using a snow fork operating at 1ghz frequency experiments were conducted at field observatories of the snow and avalanche study establishment located in different himalayan ranges patseo greater himalayan range dhundhi and solang pir panjal range interseasonal spatial and temporal variations in snow dielectric constant and associated snowpack properties were analysed for five winter seasons 2010 14 the mean seasonal snow dielectric constant is higher at dhundhi 1 82 0 02 than at patseo 1 69 0 02 the measured snow dielectric constant was used to derive snow density and liquid water content lwc a better correlation between snow dielectric constant and lwc is observed for high density snow 300 kgm 3 r 2 0 95 than for low density snow 200 kgm 3 r 2 0 73 snow fork derived snow density was in good agreement with manually measured values the snow dielectric constant database generated during this study can be used as a reference for various field applications of gpr in snow related studies

strong seismic coupling underneath garhwal kumaun region nw himalaya india abstract no great earthquake has occurred in the garhwal kumaun region of nw himalaya in the past 500 years or more we report results of continuous gps measurements from 28 sites from the region to suggest that the convergence rate in this part of the himalaya is about 18 mm yr which is leading to strain accumulation in the region the main himalayan thrust mht in the frontal part of the himalaya under the outer and southern lesser himalaya is strongly coupled for a width of about 85 km the midcrustal ramp where earthquakes of himalayan seismic belt occur exhibits low coupling strong coupling on the mht beneath the outer and lesser himalaya is homogeneous except in the very shallow updip part of the mht subduction of sediments of the indo gangetic plains or the delhi hardwar ridge does not seem to influence coupling a high rate of strain accumulation which has continued for more than 500 years on a strongly coupled mht makes this one of the most earthquake vulnerable segments of the himalayan arc

a virtual network for estimating daily new snow water equivalent and snow depth in the swiss alps daily new snow water equivalent hnw and snow depth hs are of significant practical importance in cryospheric sciences such as snow hydrology and avalanche formation in this study we present a virtual network vn for estimating hnw and hs on a regular mesh over switzerland with a grid size of 7 km the method is based on the hnw output data of the numerical weather prediction model cosmo 7 driving an external accumulation melting routine the verification of the vn shows that on average hnw can be estimated with a mean systematic bias close to 0 and an averaged absolute accuracy of 4 01 mm the results are equivalent to the performance observed when comparing different automatic hnw point estimations with manual reference measurements however at the local scale hs derived by the vn may significantly deviate from corresponding point measurements we argue that the vn presented here may introduce promising cost effective options as input for spatially distributed snow hydrological and avalanche risk management applications in the swiss alps

methodological approaches to infer end of winter snow distribution on alpine glaciers snow accumulation is an important component of the mass balance of alpine glaciers to improve our understanding of the processes related to accumulation and their representation in state of the art mass balance models extensive field measurements are required we present measurements of snow accumulation distribution on findelengletscher switzerland for april 2010 using 1 in situ snow probings 2 airborne ground penetrating radar gpr and 3 differencing of two airborne light detection and ranging lidar digital elevation models dems calculating high resolution snow depth from dem differencing requires careful correction for vertical ice flow velocity and densification in the accumulation area all three methods reveal a general increase in snow depth with elevation but also a significant small scale spatial variability lidar differencing and in situ snow probings show good agreement for the mean specific winter balance 0 72 and 0 78 m w e respectively the lidar derived distributed snow depth reveals significant zonal correlations with elevation slope and curvature in a multiple linear regression model unlike lidar differencing gpr derived snow depth is not affected by glacier dynamics or firn compaction but to a smaller degree by snow density and liquid water content it is thus a valuable independent data source for validation the simultaneous availability of the three datasets facilitates the comparison of the methods and contributes to a better understanding of processes that govern winter accumulation distribution on alpine glaciers

towards remote monitoring of sub seasonal glacier mass balance this study presents a method that allows continuous monitoring of mass balance for remote or inaccessible glaciers based on repeated oblique photography hourly to daily pictures from two automatic cameras overlooking two large valley glaciers in the swiss alps are available for eight ablation seasons 2004 11 in total we determine the fraction of snow covered glacier surface from orthorectified and georeferenced images and combine this information with simple accumulation and melt modelling using meteorological data by applying this approach the evolution of glacier wide mass balance throughout the ablation period can be directly calculated based on terrestrial remote sensing data validation against independent in situ mass balance observations indicates good agreement our methodology has considerable potential for the remote determination of mountain glacier mass balance at high temporal resolution and could be applied using both repeated terrestrial and air spaceborne observations

inhomogeneous precipitation distribution and snow transport in steep terrain 1 the inhomogeneous snow distribution found in alpine terrain is the result of wind and precipitation interacting with the snow surface over topography we introduce and explain preferential deposition of precipitation as the deposition process without erosion of previously deposited snow and thus in absence of saltation a numerical model is developed describing the relevant processes of saltation suspension and preferential deposition the model uses high resolution wind fields calculated with a meteorological model arps the model is used to simulate a 120 h snow storm period over a steep alpine ridge for which snow distribution measurements are available the comparison to measurements shows that the model captures the larger scale snow distribution patterns and predicts the total additional lee slope loading well however the spatial resolution of 25 m is still insufficient to capture the smaller scale deposition features observed the model suggests that the snow distribution on the ridge scale is primarily caused by preferential deposition and that this result is not sensitive to model parameters such as turbulent diffusivity drift threshold or concentration in the saltation layer

on the use of dislocations to model interseismic strain and stress build up at intracontinental thrust faults creeping dislocations in an elastic half space are commonly used to model interseismic deformation at subduction zones and might also apply to major intracontinental thrust faults such as the main himalayan thrust here we compare such models with a more realistic 2 d finite element model that accounts for the mechanical layering of the continental lithosphere and surface processes and that was found to fit all available constraints on interseismic and long term surface displacements these can also be fitted satisfactorily from dislocation models the conventional back slip model commonly used for subduction zones may however lead to a biased inference about the geometry of the locked portion of the thrust fault we therefore favour the use of a creeping buried dislocation that simulates the ductile shear zone in the lower crust a limitation of dislocation models is that the mechanical response of the lithosphere to the growth of the topography by bending of the elastic cores and ductile flow in the lower crust cannot be easily introduced fortunately these effects can be neglected because we may assume to first order a stationary topography moreover we show that not only can dislocation models be used to adjust surface displacements but with some caution they can also provide a physically sound rationale to interpret interseismic microseismicity in terms of stress variations

same night observations of spread f by the jicamarca radio observatory in peru and cupri in alcântara brazil 50 mhz echoes from equatorial spread f were observed on several nights by both the jicamarca radio observatory jro in peru and the cornell university portable radar interferometer cupri in alc ntara brazil although little detailed correlation is expected between sites separated by such large distances the night of october 17 1994 shows some remarkable similarities between peru and brazil on this night spread f commenced at both jicamarca and alc ntara as thin bottomside layers situated near 320 km altitude at nearly the same local times later major plumes erupted that reached to over 1000 km altitude at both sites since plumes normally drift west to east these are obviously not the same structures but the similarities indicate that conditions for spawning them must have been coincidentally very similar on this night the next two nights which produced plumes over brazil but only bottomside layers over peru emphasize that local conditions on the same night can be very different at the two locations the importance of having a sufficiently wide beam for exploring spread f over a large altitude range at the alc ntara site is also explored

enhanced estimation of glacier mass balance in unsampled areas by means of topographic data a new method was developed to estimate the mass balance in unsampled areas from existing datasets three years of mass balance data from two glaciers in the central italian alps were used to develop and test a multiple regression method based exclusively on a 10 m resolution digital terrain model the introduction of a relative elevation attribute which expresses the degree of wind exposure of the gridcells notably increased the amount of explainable variance in winter balance with respect to altitude itself the summer balance is highly correlated with elevation but in order to obtain reliable extrapolations the clear sky shortwave radiation and the diurnal cloud cover cycle had to be taken into account the net annual mass balance on a glacier system comprising the two monitored glaciers was calculated by applying both a single regression of winter and summer balance with altitude and the new regression method the consistency of results was assessed against measured net balances and snow cover maps drawn in the ablation season the results of the new method were in close agreement with observations and proved to be less sensitive to the spatial representation of the sampled areas

a dislocation model for the earthquake cycle at convergent plate boundaries summary a kinematic model for the earthquake cycle at convergent plate boundaries has been constructed on the basis of dislocation theory we model the lithosphere asthenosphere system by a stratified semi infinite medium under gravity consisting of an elastic surface layer an intervening layer with maxwell viscoelasticity and an elastic substratum the steady motion of plate convergence is naturally represented by uniform slip at a constant rate on the upper boundary of the descending oceanic plate the occurrence of interplate earthquakes is regarded as a perturbation of the steady state plate motion and represented by a periodic sequence of step slips on a finite seismic zone of the plate interface based on dislocation theory we can show that the steady slip on the interface deeper than the lithosphereasthenosphere boundary does not contribute to surface deformation in the steady state accordingly the surface deformation associated with the earthquake cycle is given by the superposition of viscoelastic responses to the steady slip on the interface shallower than the lithosphere asthenosphere boundary the steady backslip on the seismic zone and the periodic sequence of seismic slips we have computed cyclic patterns of vertical displacements at the free surface for two representative cases taking account of gravity effects the patterns of vertical displacements differ notably in the latter stage of the cycle depending on whether or not the seismic zone extends through the entire thickness of the lithosphere after the completion of one earthquake cycle our model yields a certain amount of permanent deformation resulting from the steady plate convergence the pattern of the permanent deformation that is characterized by steep uplift on the continental side sharp subsidence at the plate boundary and gentle uplift on the oceanic side is irrespective of the cyclic process of stress accumulation and release repeated on the seismic zone the earthquake cycle model developed here provides a possible explanation for the formation of earthquake origin marine terraces

estimation of snow water equivalence using sir c x sar ii inferring snow depth and particle size for pt i see ibid vol 38 no 6 p 2465 74 2000 the relationship between snow water equivalence swe and sar backscattering coefficients at c and x band 5 5 and 9 6 ghz can be either positive or negative therefore discovery of the relationship with an empirical approach is unrealistic instead the authors estimate snow depth and particle size using sir c x sar imagery from a physically based first order backscattering model through analyses of the importance of each scattering term and its sensitivity to snow properties using numerically simulated backscattering values the authors develop semi empirical models for characterizing the snow ground interaction terms the relationships between the ground surface backscattering components and the snowpack extinction properties at c band and x band with these relationships snow depth and optical equivalent grain size can be estimated from sir c x sar measurements validation using three sir c x sar images shows that the algorithm performs usefully for incidence angles greater than 300 with root mean square errors rmses of 34 cm and 0 27 mm for estimating snow depth and ice optical equivalent particle radius respectively

southern limits of major earthquake ruptures along the himalaya between longitudes 75 and 90 e the ruptures responsible for major earthquakes along the himalayan convergent plate margin hcpm occur in a strikewise oriented zone of frictional failure and relative slip in a buried detachment along the upper surface of the indian shield rocks subducting under the himalaya the southern limit of the rupture zone is a geotectonic lineament whose geographic location is important in assessing risk due to earthquakes a major part of this article is taken up in arguing that the available macroseismic and instrumental evidence for the 1934 bihar nepal earthquake is consistent with the view that the rupture which caused it occurred in the detachment mostly under the lesser himalaya northward from the vicinity of the surface trace of the main boundary thrust mbt since a similar location has been inferred by others for the 1905 kangra earthquake rupture a basis arises for postulating that over more than half of the length of the hcpm between 75 and 90 e longitudes the ruptures responsible for major earthquakes lie in the detachment with their southern limits geographically similarly close to the surface trace of the mbt this includes the nearly 700 km long seismic gap between the 1905 and 1934 ruptures

hysteretic dynamics of seasonal snow depth distribution in the swiss alps 1 the dynamics of the spatial snow distribution is a key feature when investigating a seasonal snow cover on the catchment scale this study explores the spatial variability of snow depth during the course of snow accumulation and depletion based on daily data from 77 weather stations in the swiss alps during 6 consecutive seasons we derive a statistical description of the snow cover dynamics by analyzing temporal trajectories in plots of the standard deviation over mean where xi is a set of snow depth measurements on one particular day the analysis reveals that the evolution of closely follows a power law 0 84 0 01 during the accumulation period for all 6 winters however during snowmelt the trajectory of displays a clearly different path as with classical hysteresis phenomena surprisingly a simplistic model of uniform melting describes this path reasonably well we believe that the conceptual framework outlined in this study is helpful in describing important characteristics of the dynamics of seasonal snow depth spatial variability future studies could apply the methodology introduced here to incorporate stochastic means in modeling snow distribution even for a broader range of length scales and different alpine terrain

implications of spatial distributions of snow mass and melt rate for snow cover depletion theoretical considerations snow becomes patchy while melting giving a heterogeneous surface with large contrasts in characteristics such as albedo it is therefore necessary for surface schemes used in atmospheric and hydrological models to represent the influence of heterogeneities in snow cover on scales smaller than the model grid this is typically done by introducing a snow cover depletion scd curve relating fractional snow cover to average depth here ad hoc functional forms which have been used for this relationship are first compared with forms obtained for an assumed initial snow distribution undergoing homogeneous melt the energy available for melt may be heterogeneous however and can be influenced by factors that also influence snow distribution such as slope aspect and vegetation cover themodification of scd curves by spatial variations in melt energy is investigated and resulting curves are found to be similar to those which would be given by homogeneous melting of a snow cover with greater initial variance this influence is increased by any negative correlation between snow depth and melt rate

constraints on himalayan deformation inferred from vertical velocity fields in nepal and tibet spirit leveling data from the nepal himalaya between 1977 and 1990 indicate localized uplift at 2 3 mm yr in the lesser himalaya with spatial wavelengths of 25 35 km and at 4 6 mm yr in the greater himalaya with a wavelength of 40 km leveling data with significantly sparser spatial sampling in southern tibet between 1959 and 1981 suggest that the himalayan divide may be rising at a rate of 7 5 5 6 mm yr relative to central tibet we use two dimensional dislocation modeling methods to examine a number of structural models that yield vertical velocity fields similar to those observed although these models are structurally nonunique dislocation models that satisfy the data require aseismic slip rates of 2 7 mm yr on shallow dipping faults beneath the lesser himalaya and rates of 9 18 mm yr on deep thrust faults dipping at 25 n near the greater himalaya unfortunately the leveling data cannot constrain long wavelength uplift 100 km across the himalaya and unequivocal estimates of aseismic slip in central nepal are therefore not possible in turn the poor spatial density of leveling data in southern tibet may inadequately sample the processes responsible for the uplift of the greater himalaya despite these shortcomings in the leveling data the pattern of uplift is consistent with a crustal scale ramp near the greater himalaya linking shallow northward dipping thrust planes 3 6 beneath the lesser himalaya and southern tibet aseismic slip on the potential rupture surface of future great earthquakes beneath the nepal himalaya south of this ramp appears not to exceed 30 of the total convergence rate between india and southern tibet resulting in an accumulating slip deficit of 13 8 mm yr

interpretation of observed ground level changes due to the 1905 kangra earthquake northwest himalaya the kangra earthquake of 1905 in the northwest himalaya was the first indian earthquake for which coseismic ground elevation changes were measured through repeat precision levelling the levelling une from saharanpur to mussoorie via dehra dun was situated near the southeastern extremity of the nw se trending meizoseismal area maximum uplift of 14 3 cm was measured at a bench mark in dehra dun some details of the levelling data having been published recently data for eight bench marks were considered for interpretation in this study in principle these are sufficient for us to estimate eight parameters of a rectangular rupture buried in a homogeneous poisson solid but because of some uncertainties regarding the bench mark positions and also the relatively small amounts of uplift measured at the bench marks we have preferred to use the data as a means to check the reasonableness of rupture models proposed on other grounds rather than to propose a new model independently the observed elevation changes are not in accord with the view that the kangra earthquake was caused by a single 100 km long rupture along the shahpur mandi sector of the northwest himalaya however the data can be explained if in addition a second smaller rupture extending on either side of the levelling une near dehra dun is assumed the data can also be explained if the rupture during the earthquake had 1 a length of 280 km parallel to the general strike of the himalaya from around kangra up to a short distance about 10 15 km northwest of the levelling une near dehra dun 2 a breadth of 80 km perpendicular to the strike of the himalaya 3 a northeasterly dip of about 5 and 4 a depth of 10 15 km along its sw edge finally the elevation data rule out any role for the main boundary thrust in the occurrence of the kangra earthquake this major tectonic feature demarcating the geological boundary between the outer and the lesser himalaya thus appears to be unimportant in the current seismotectonics of the region and the subduction of the indian lithospheric plate under the mountains

mapping snow distribution in the alaskan arctic using aerial photography and topographic relationships a method is presented for mapping the end of winter snow distribution in the arctic using vertical aerial photographs taken during the melt the photos show a limited number of distinctive snowmelt patterns that arise reliably year after year data and results from an energy balance melt model indicate that the patterns are not caused by differential melt but instead represent areas of distinctive end of winter snow depth a map of these snowmelt patterns is thus a map of the end of winter snow distribution because wind transport of snow is common the patterns are closely related to the topography rules based on this pattern topography relationship are developed and used to map the snow cover directly from topographic maps for three areas covering 220 km2 of the kuparuk basin in northern alaska analysis of the snow maps suggests that about 75 of the area was mapped correctly applicability reliability and limitations of this mapping approach are discussed

prototype wireless sensors for monitoring subsurface processes in snow and firn the detection and monitoring of meltwater within firn presents a significant monitoring challenge we explore the potential of small wireless sensors etracer et to measure temperature pressure electrical conductivity and thus the presence or absence of meltwater within firn through tests in the dry snow zone at the east greenland ice core project site the tested sensor platforms are small robust and low cost and communicate data via a vhf radio link to surface receivers the sensors were deployed in low temperature firn at the centre and shear margins of an ice stream for 4 weeks and a bucket experiment was used to test the detection of water within otherwise dry firn the tests showed the et could log subsurface temperatures and transmit the recorded data through up to 150 m dry firn two vhf receivers were tested an autonomous phase sensitive radio echo sounder apres and a winradio the apres can combine high resolution imaging of the firn layers by radio echo sounding with in situ measurements from the sensors to build up a high spatial and temporal resolution picture of the subsurface these results indicate that wireless sensors have great potential for long term monitoring of firn processes

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

mass balance reconstruction for glacier no 354 tien shan from 2003 to 2014 this study presents a reconstruction of the seasonal mass balance of glacier no 354 located in the akshiirak range kyrgyzstan from 2003 to 2014 we use a distributed accumulation and temperature index melt model driven by daily air temperature and precipitation from a nearby meteorological station the model is calibrated with in situ measurements of the annual mass balance collected from 2011 to 2014 the snow cover depletion pattern observed using satellite imagery provides additional information on the dynamics of mass change throughout the melting season two digital elevation models derived from high resolution satellite stereo images acquired in 2003 and 2012 are used to calculate glacier volume change for the corresponding period the geodetic mass change thus derived is used to validate the modelled cumulative glacier wide balance for the period 2003 12 we find a cumulative mass balance of 0 40 10mw e a 1 this result agrees well with the geodetic balance of 0 48 0 07mw e a 1 over the same period

present day kinematics of asia derived from geologic fault rates active fault geometry available quaternary rates on major faults and the far field plate motion are used to determine crustal kinematics in the collision zone between india and asia using a finite element formalism to construct a spherical shell model of the asian continent with embedded faults we seek a velocity solution approaching the motion of rigid blocks by minimizing the elastic strain energy in the fault bounded blocks by doing so we test the assumption that long term deformation within continents is mostly localized into major faults in the solution fault motion accounts for more than 80 of the deformation allowing us to describe our velocity model in terms of quasi rigid block rotations on the sphere south china is rotating clockwise about a pole located southwest of borneo implying an e ese velocity vector of 11 mm yr for a point at shanghai in agreement with the velocity vector determined by very long baseline interferometry heki et al 1995 the eastward movement of south china is accommodated by oblique extension along the red river fault at a rate of 10 5 mm yr in the south and by the combination of left lateral strike slip motion on the qinling dabie shan fault and the counterclockwise rotation of the ordos and adjacent blocks in the north the tarim rotates clockwise with respect to dzungaria about a pole located at 44 n 92 e consistent with increasing crustal shortening toward the west throughout the tien shan assuming incompressibility a crustal volume budget over a domain encompassing the tertiary mountain ranges in asia shows that over the last 10 000 years 73 4 of the north south shortening between india and asia has been absorbed by thickening of the lithosphere and 27 has been accommodated by lateral extrusion of continental blocks the present day predominance of thickening in asia results from the relatively slow eastward motion of south china controlled by strike slip faulting in the qinling shan and oblique extension in northeastern china

mapping the descent of indian and eurasian plates beneath the tibetan plateau from gravity anomalies the collision of india with asia has produced a complicated continental continental plate boundary involving folding and faulting of variable trends and styles within and along the margins of the tibetan plateau numerous lines of evidence including the development of two scales of folding in tibet suggest that the lowermost crust is behaving in a ductile fashion this weak lower crust might then decouple the fundamental plate tectonic motions in the uppermost mantle from the complex pattern of surface faulting in this study we use bouguer gravity anomalies to map out the geometry of indian and eurasian plate interactions in the mantle beneath the plateau based on both the inferred geometry of the moho and lateral variations in lithospheric strength determined from mechanical modeling in our preferred model the lithosphere beneath tibet consists of two distinct units 1 the underthrust to the north indian plate which sutures with the eurasian plate in the upper mantle below the yarlung zangpo suture or the gangdese igneous belt 200 400 km north of the main boundary thrust and 2 the underthrust to the south eurasian plate a subducting slab of indian upper mantle extends about 200 km into the asthenosphere north from the mantle suture and exerts a bending moment of about 3 5 1017 n on the indian plate thus the mantle lithosphere appears to be behaving in the simple fashion of converging oceanic plates while the more buoyant continental crust deforms under high gravitational potential in a complex pattern controlled by its lateral and vertical strength heterogeneity

a numerical model to simulate snow cover stratigraphy for operational avalanche forecasting laws of snow metamorphism have been introduced in a numerical model which simulates the evolution of temperature density and liquid water profiles of snow cover as a function of weather conditions to establish these laws the authors have summarized previous studies on temperature gradient and on wet snow metamorphism and they have also conducted metamorphism experiments on dry or wet fresh snow samples an original formalism was developed to allow a description of snow with parameters evolving continuously throughout time the introduction of laws of metamorphism has improved significantly the derivation of the settlement of internal layers and of snow covered albedo which depend on the simulated stratigraphy i e the type and size of snow grains of different layers of the snow cover the model was tested during a whole winter season without any re initialization comparison between the simulated characteristics of the snow cover and the observations made in the field are described in detail the model proved itself to be very efficient in simulating accurately the evolution of the snow cover stratigraphy throughout the whole winter season

combining binary decision tree and geostatistical methods to estimate snow distribution in a mountain watershed we model the spatial distribution of snow across a mountain basin using an approach that combines binary decision tree and geostatistical techniques in april 1997 and 1998 intensive snow surveys were conducted in the 6 9 km2 loch vale watershed lvws rocky mountain national park colorado binary decision trees were used to model the large scale variations in snow depth while the small scale variations were modeled through kriging interpolation methods binary decision trees related depth to the physically based independent variables of net solar radiation elevation slope and vegetation cover type these decision tree models explained 54 65 of the observed variance in the depth measurements the tree based modeled depths were then subtracted from the measured depths and the resulting residuals were spatially distributed across lvws through kriging techniques the kriged estimates of the residuals were added to the tree based modeled depths to produce a combined depth model the combined depth estimates explained 60 85 of the variance in the measured depths snow densities were mapped across lvws using regression analysis snow covered area was determined from high resolution aerial photographs combining the modeled depths and densities with a snow cover map produced estimates of the spatial distribution of snow water equivalence swe this modeling approach offers improvement over previous methods of estimating swe distribution in mountain basins

east west and vertical spectral asymmetry associated with equatorial type i waves during strong electrojet conditions 1 pohnpei radar observations 1 we have studied a particularly strong vertical type i event with the equatorial pohnpei radar during that event which lasted several hours we routinely obtained type i waves in radar beams pointed vertically as well as at 14 3 degrees east and west of vertical this data set has allowed us to revisit the question of the equatorial electrojet east west and up down asymmetries these asymmetries are known to favor downshifted waves during the daytime electrojet in our study we have contrasted type i spectra obtained simultaneously in the east and west beams in addition to analyzing upshifted and downshifted waves in the vertical beam data we have found that when the echoes become particularly strong both the east west and up down power asymmetries may not only vanish but can even reverse their signs furthermore these tendencies occur simultaneously in the east west and up down asymmetries finally we have noted that the power asymmetry is accompanied by an asymmetry in type i doppler shifts which is only clearly visible however when the overall echo power is weaker

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

a unified interpretation of vertical movement in himalaya and horizontal deformation in tibet on the basis of elastic and viscoelastic dislocation theory abstract the present day convergence rate between the indian and the eurasian plates has been estimated to be about 50 mm year at the collision boundary extending along the himalayas about 40 of the total convergence is consumed by the subduction of the indian plate beneath the eurasian plate the rest of about 60 is consumed by the internal deformation of the eurasian plate the present crustal movement in this region is characterized by rapid uplift along the high himalayas and large scale horizontal deformation in and around tibet the fundamental causes of these two different types of crustal movement are the same interaction between the indian and the eurasian plates in this study we represent the plate interaction by steady increase in tangential displacement discontinuity dislocation across the interface that divides a surface layer overlying a viscoelastic half space into the indian and the eurasian plates first given a steady slip of 20 mm year at the plate interface with a ramp shaped undulation below the high himalayas we computed the profile of surface uplift rates along a line perpendicular to the himalayan arc the result accords with observed free air gravity anomalies and the intermediate and short term uplift rates estimated respectively from the present heights of river terraces and levelling data this means that the rapid uplift of the high himalayas is due to the steady slip along the ramp shaped plate interface below it second given the steady slips of 20 mm year along the 2000 km long collision boundary and 50 mm year along the remaining portions of the india eurasia plate boundary we computed the increase rates of horizontal deformation in and around tibet the result accords with the observed strikes and slip rates of major quaternary active faults this means that the horizontal deformation in and around tibet is due to the slip deficits of 30 mm year at the collision boundary from these two results we can conclude that the present rapid uplift of the high himalayas and large scale horizontal deformation in and around tibet are consistently explained by a single plate interaction model based on elastic and viscoelastic dislocation theory this study sheds new light on the driving mechanism of the crustal deformation in the india eurasia collision zone as follows the plate interaction on single plate interface consists of coexisting two different physical mechanisms 1 slip along the ramp undulation spatial changes in slip direction 2 slip deficit at the collision boundary spatial changes in slip rates as a consequence the two different types of crustal deformation in the india eurasia collision zone are driven by these two different physical mechanisms

can an earthquake of mw 9 occur in the himalayan region it has been suggested that all of the earth s subduction zones are capable of producing an m w 9 earthquake such a possibility has also been suggested for the himalayan collisional arc we examined recent and historical earthquakes in the himalayan region and suggest that in the past few hundred years only great earthquakes m w 8 have occurred in the region the largest being the 1950 assam earthquake with m w 8 6 several aseismic ridges segment the himalayan arc and these appear to have limited the extent of rupture in earthquakes of the past 200 years there is also evidence of distributed deformation and out of sequence thrusting where only part of the detachment participates in the accommodation of the convergence we concluded that although it is unlikely that an m w 9 earthquake could occur in the himalaya from the hazard point of view a great earthquake of m w 8 anywhere along the himalayan arc could kill about one million people in the himalaya and adjoining indo ganga plains as an example a scenario developed for a hypothetical m w 8 earthquake occurring in the middle of the night at mandi close to the epicentre of the 1905 kangra earthquake predicts an estimated loss of one million human lives

potential of time lapse photography of snow for hydrological purposes at the small catchment scale time lapse photography provides an attractive source of information about snow cover characteristics especially at the small catchment scale the objective of this study was to design and test a monitoring system which allows multi resolution observations of snow cover characteristics the main aim was to simultaneously investigate the spatio temporal patterns of snow cover snow depth and snowfall interception in the area very close to the camera and the spatio temporal patterns of snow cover in the far range the multi resolution design was tested at three sites in the eastern part of the austrian alps hochschwab rax region digital photographs were taken at hourly time steps between 6 00 and 18 00 in the period november 2004 to december 2006 the results showed that the time lapse photography allows effective mapping of the snow depths at high temporal resolution in the region close to the digital camera at many snow stake locations it is possible to process a large number of photos by using an automatic procedure for accurate snow depth readings the digital photographs can also be used to infer the settling characteristics of the snow pack and snow interception during the day although it is not possible to directly estimate the snow interception mass the photos may indeed give very useful information on the snow processes on and beneath the forest canopy the main advantage of using time lapse photography in the far range of the digital camera is to observe the spatio temporal patterns of snow cover over different landscape configurations the results illustrate that digital photographs can be very useful for parameterising processes such as sloughing on steep slopes snow deposition in gullies and snow erosion on mountain ridges in a distributed snow model copyright 2011 john wiley sons ltd

an energy and mass model of snow cover suitable for operational avalanche forecasting a numerical model has been developed to simulate energy and mass evolution of snow cover at a given location as a function of meteorological conditions precipitation air temperature humidity wind velocity and incoming short wave and long wave radiation this model named crocus was first tested on a well instrumented field during a whole winter showing its ability to simulate the important phenomena affecting the evolution of the snow layers high temperature gradients wetting compaction and melting freezing cycles a second test was conducted at two locations in the french network used for operational avalanche forecasting though the weather observations are made there only twice daily the snow profiles calculated by the model were very close to those obtained once a week by a pit observation crocus proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting

evolution of the stress field in southern california and triggering of moderate size earthquakes a 200 year perspective changes in stress in southern california are modeled from 1812 to 2025 using as input 1 stress drops associated with six large 7 0 7 5 earthquakes through 1995 and 2 stress buildup associated with major faults with slip rates 3 mm yr as constrained by geodetic paleoseismic and seismic measurements evolution of stress and the triggering of moderate to large earthquakes are treated in a tensoffal rather than a scalar manner we present snapshots of the cumulative coulomb failure function acff as a function of time for faults of various strike dip and rake throughout southern california we take acff to be zero everywhere just prior to the great shock of 1812 we find that about 95 of those well located m 6 earthquakes whose mechanisms involve either strike slip or reverse faulting are consistent with the coulomb stress evolutionary model that is they occurred in areas of positive acff the interaction between slow moving faults and stresses generated by faster moving faults significantly advanced the occurrence of the 1933 long beach and 1992 landers events in their earthquake cycles coulomb stresses near major thrust faults of the western and central transverse ranges have been accumulating for a long time future great earthquakes along the san andreas fault especially if the san bernardino and coachella valley segments rupture together can trigger moderate to large earthquakes in the transverse ranges as appears to have happened in the santa barbara earthquake that occurred 13 days after the great san andreas shock of 1812 maps of current acff provide additional guides to long term earthquake prediction

small scale spatial structure of shallow snowcovers the results of a field study of the small scale spatial structure of the depth of shallow seasonal snowcovers in prairie and arctic environments are presented it is shown that the spatial distribution of snow depth is fractal at small scales becoming random at scales beyond some limiting length this is due to the autocorrelation of depth at small sampling distances the transition of fractal to random behaviour is indexed by a cutoff length which is defined by the intersection of the fractal slope and horizontal tangent of a logarithmic plot of the standard deviation of depth versus sampling distance the magnitude of the cutoff length is related to the degree of macroscopic variability of the underlying topography an increase in length due to the effects of macroscopic topographic variability on snowcover accumulation is confirmed by de trending field measurements the de trended data shown a cutoff length for wheat stubble and fallow surfaces of approximately 30 m which is consistent with the distance determined from measurements on flat fields the implications of the transition of snow depth from fractal to random structure on the scales of snow sampling and modelling are presented the cutoff length may provide a statistic for stratifying shallow snowcovers by linking snowcover properties to the underlying topography

on interseismic elevation changes and strain accumulation for great thrust earthquakes in the nepal himalaya estimates of interseismic ground elevation change rates from nepal himalaya based on repeat levelling observations between 1977 and 1990 in the meizoseismal zone of the great thrust earthquake of 1934 have been reported by jackson and bilham 1994 we explain them using the model of savage 1983 for seismic strain accumulation and release along plate boundary faults pbf at convergent plate margins thus the section of the pbf under the nepal himalaya that ruptured during the 1934 earthquake may be currently locked and the hanging wall rocks may be experiencing downdip drag at the local plate convergence rate three independent estimates of 150 100 and 50 km for downdip rupture width during the 1934 earthquake are available if we use them as estimates of the current width of the locked zone in nepal then values of 18 14 and 12 mm year respectively for the plate convergence rate are obtained although all these values compare favourably with the estimated long term average rate of 18 7 mm year for plate convergence accommodated at the himalaya the rms error is the least for the model with 150 km width of the locked zone

the field of crustal velocity in asia calculated from quaternary rates of slip on faults rates of quaternary faulting when treated as measures of strain rates within regions several times larger than the depths of brittle faulting yield a velocity field for asia that matches the average relative velocity between the indian and eurasian plates over the past 2 myr nuvel 1a and the velocity of shanghai with respect to eurasia measured with very long baseline interferometry vlbi by using rates of slip on discrete surfaces faults to define average strain rates we explicitly assume that the large scale deformation can be treated as that of a continuum depending on the jcales over which strain rates are averaged 87 to 93 per cent of the assumed strain ites are fit within assigned 1 sigma uncertainties and 97 to 99 per cent are fit within 2 sigma the internal consistency of these data and the agreement with independent rates nuvel 1a and vlbi test the validity of treating large scale deformation of continents as that of a continuum in the calculated velocity field a large fraction 85 per cent of india s convergence with eurasia is absorbed by crustal or lithospheric thickening among consistently misfit assumed strain rates are those dominated by high rates of strike slip faulting strain associated with 20 30 mm a 1 of slip on the altyn tagh karakax and karakorum faults is inconsistent with the distributions of strain in surrounding regions we conclude that these rates all of which are based on correlations of ages of offset landforms with changes in global climate and not on radiometric dating have been systematically overestimated lateral transport out of india s northward path is relatively minor south china is calculated to move east southeast at less than 10 mm a 1

re analysis of seasonal mass balance at abramov glacier 1968 2014 abramov glacier located in the pamir alay kyrgyzstan is a reference glacier within the global terrestrial network for glaciers long term glaciological measurements exist from 1968 to 1998 and a mass balance monitoring programme was re established in 2011 in this study we re analyse existing mass balance data and use a spatially distributed mass balance model to provide continuous seasonal time series of glacier mass balance covering the period 1968 2014 the model is calibrated to seasonal mass balance surveys and then applied to the period with no measurements validation and recalibration is carried out using snowline observations derived from satellite imagery and after 2011 also from automatic terrestrial camera images we combine direct measurements remote observations and modelling the results are compared to geodetic glacier volume change over the past decade and to a ground penetrating radar survey in the accumulation zone resolving several layers of accumulation previously published geodetic mass budget estimates for abramov glacier suggest a close to zero mass balance for the past decade which contradicts our results we find a low plausibility for equilibrium conditions over the past 15 years instead we suggest that the glacier s sensitivity to increased summer air temperature is decisive for the substantial mass loss during the past decade

are flat field snow depth measurements representative a comparison of selected index sites with areal snow depth measurements at the small catchment scale single or a limited number of point observations such as from index stations are commonly assumed to be representative for the snow cover of larger areas in many applications this study presents a systematic investigation of the relationship between point observations and areal mean snow depths ranging from the scale of tens of metres to entire catchments we analyse aerial snow depth information from four mountain regions in the european alps one in the spanish pyrenees and one in the canadian rocky mountains obtained from airborne laser scanning surveys this rich data set allowed to compare point values with snow cover statistics reflecting the real snow depth distribution of the investigation areas we present two contrasting approaches in order to assess the representativeness of typical flat field snow depth measurements in the first approach we define potential index stations based on topographic characteristics as commonly applied for snow cover monitoring stations the point observations of these index stations are then compared with the mean values in their vicinities we show that most of the index stations strongly overestimate the snow depth of the catchment and of their surrounding area at distances of several hundreds of metres results confirm the expectation that the larger the support area the smaller the difference to the mean of the complete catchment the second approach was to analyse topographic characteristics of all cells with snow depths that deviated less than 10 from the catchment mean it appears that these representative cells are rather randomly distributed and cannot be identified a priori in summary our results show large potential biases of index stations with respect to snow distribution and therefore also snow water equivalent copyright c 2014 john wiley sons ltd

strong spatial variability of snow accumulation observed with helicopter borne gpr on two adjacent alpine glaciers the spatial distribution of snow accumulation plays an essential role for the mass balancedistribution on alpine glaciers traditional point measurements snow pits and probes are labour intensive and interpolation in between the points causes uncertainties airborne radar measurements have already been used for snow mapping innon glacierized terrain but not on alpine glaciers to enhance our understanding ofthe spatial distribution of accumulation and pin down reasons for observed variations we have conducted high resolution helicopter borne radar measurements on the temperatedglacier findel and neighbouring adler glacier in southwestern switzerland the radar sensor was mounted underneath a helicopter and operated at a centre frequencyof 500 mhz with a bandwidth of 400 mhz the results were validated withextensive ground based profiling of the snow cover the radar data allows a clearrecognition of the snow cover 6 of the total profile length of 10 km did not allowinterpretation due to missing or disturbed layering and agreed well with the groundbased measurements r2 0 85 reduced accumulation has been observed in allcrevassed zones statistical analysis of the correlation between observed accumulationand terrain characteristics have been performed in a gis environment revealing differingaccumulation patterns on the lower part of findel glacier accumulation showsa clear altitudinal trend while the upper part is dominated by strongly varying snowdepth without an altitudinal trend the accumulation characteristic on adler glacieris similar to the upper part of findel glacier but despite of their close vicinity accumulationis reduced by 40 compared to the same elevation on findel glacier thisstudy reveals a large potential of helicopter borne snow profiling for measurements ofaccumulation distribution on alpine glaciers

spatial variability of new snow amounts derived from a dense network of alpine automatic stations since 1996 a dense network of alpine automatic weather and snow measurement inter kantonales mess und informationssystem imis stations has been in operational use for local and regional avalanche warning the measurements of the imis stations are assumed to be representative for spatially extended regions around the measuring sites for applications in avalanche risk management in this study the regional representativeness of these stations with regard to the daily amount of new snow is investigated the results show that the amount of daily new snow is spatially correlated in a range of 5 55 km regarding simultaneous observations of daily new snow measurements which are 5 10 km apart the probability of detection pod is given as 0 5 0 03 in this paper the pod of an automatic warning network is introduced as an indicator of the representativeness of point measurement information for avalanche warning applications the results of this study may mark a reference value for verification of spatially distributed alpine meteorological models which evaluate the amount of daily new snow in the swiss alps

estimating alpine snowpack properties using fmcw radar large variations in both snow water equivalent swe and snow slope stability are known to exist in the alpine snowpack caused by wind topographic and microclimatic effects this variability makes extrapolation of point measurements of snowpack properties difficult and prone to error but these types of measurements are used to estimate swe and stability across entire mountain ranges radar technology provides a promising alternative to point measurements because large areas can be covered quickly and non intrusively there is great potential for obtaining information on a large spatial scale from airborne applications frequency modulated continuous wave fmcw radar measurements were made from the ground in several different alpine snowpacks along with manual and in situ electrical measurements the surface and ground reflections from the radar data combined with an average density estimate can provide a useful estimate of swe in addition the locations of internal reflections are highly correlated with both visually identified layers and measured changes in in situ dielectric properties

cupri observations of pre sunrise vertical type i echoes from the equatorial electrojet above alcântara brazil the cornell university portable radar interferometer cupri made high resolution vertical radar measurements of the equatorial electrojet above alc ntara brazil from mid august to mid october 1994 as part of the guara dip equator campaign spectra obtained during the period of a few hours before sunrise show the usual nighttime persistence asymmetry wherein there is a preponderance of downward type i phase velocities as a function of time these are the first high resolution measurements in south america of this effect at a location other than jicamarca peru furthermore the cupri interferometer phase data clearly indicate that when changes in the sign of the dominate type i peaks occur they are tied to the normal phase progressions of the large scale waves no reversal of the asymmetry as does occur in the daytime was seen in this nighttime period

wind influence on snow depth distribution and accumulation over glaciers 1 in mountain regions wind is known to cause snow redistribution while physically based models of snow redistribution have been developed for flat to gently rolling terrain extension of these findings to steep terrain has been limited by the complexity of wind fields in such areas in this study we applied a nonhydrostatic and compressible atmospheric prediction model to steep alpine topography and compared the results to a fully distributed data set of snow depth estimations the results show reduced horizontal wind velocity as well as an increasing downward vertical wind velocity over areas with the largest winter accumulation which are mostly glacierized we show that the wind velocity normal to the local surface which should be zero in a nondivergent flow field and is a direct measure of increased or decreased local deposition is a function of small scale features of local topography the correlation between wind fields snow accumulation and glacierization suggests that accurate modeling of wind fields over glacierized areas in complex terrain is a key factor for understanding the mass balance distribution of glaciers

ice volume changes of selected glaciers in the swiss alps since the end of the 19th century the evolution of surface topography of glaciers in the swiss alps is well documented with high resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid 19th century in order to quantify and interpret glacier changes in the swiss alps time series of volume changes over the last 100 150 years have been collected the available datasets provide a detailed spatial resolution for the retreat period since the end of the little ice age the spatial distribution as well as temporal variations of the thickness change were analyzed a significant ice loss since the end of the 19th century was observed in the ablation area while the changes in the accumulation area were small we found moderate negative secular rates until the 1960s followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present an evaluation of 19 glaciers revealed a total ice volume loss of about 13 km 3 since the 1870s of which 8 7 km 3 occurred since the 1920s and 3 5 km 3 since 1980 decadal mean net balance rates for the periods 1920 60 1960 80 and 1980 present are 0 29 0 03 and 0 53 m a 1 w e respectively

continuous snowpack monitoring using upward looking ground penetrating radar technology snow stratigraphy and water percolation are key contributing factors to avalanche formation so far only destructive methods can provide this kind of information radar technology allows continuous non destructive scanning of the snowpack so that the temporal evolution of internal properties can be followed we installed an upward looking ground penetrating radar system upgpr at the weissfluhjoch study site davos switzerland during two winter seasons 2010 11 and 2011 12 we recorded data with the aim of quantitatively determining snowpack properties and their temporal evolution we automatically derived the snow height with an accuracy of about 5 cm tracked the settlement of internal layers 7 cm and measured the amount of new snow 10 cm using external snow height measurements we determined the bulk density with a mean error of 4 3 compared to manual measurements radar derived snow water equivalent deviated from manual measurements by 5 furthermore we tracked the location of the dry to wet transition in the snowpack until water percolated to the ground based on the transition and an independent snow height measurement it was possible to estimate the volumetric liquid water content and its temporal evolution even though we need additional information to derive some of the snow properties our results show that it is possible to quantitatively derive snow properties with upgpr

a synthetic study to assess the applicability of full waveform inversion to infer snow stratigraphy from upward looking ground penetrating radar data snow stratigraphy and liquid water content are key contributing factors to avalanche formation upward looking groundpenetrating radar upgpr systems allow nondestructive monitoring of the snowpack but deriving density and liquid water content profiles is not yet possible based on the direct analysis of the reflection response we have investigated the feasibility of deducing these quantities using full waveform inversion fwi techniques applied to upgpr data for that purpose we have developed a frequency domain fwi algorithm in which we additionally took advantage of time domain features such as the arrival times of reflected waves our results indicated that fwi applied to upgpr data is generally feasible more specifically we could show that in the case of a dry snowpack it is possible to derive snow densities and layer thicknesses if sufficient a priori information is available in case of a wet snowpack in which it also needs to be inverted for the liquid water content the algorithm might fail even if sufficient a priori information is available particularly in the presence of realistic noise finally we have investigated the capability of fwi to resolve thin layers that play a key role in snow stability evaluation our simulations indicate that layers with thicknesses well below the gpr wavelengths can be identified but in the presence of significant liquid water the thin layer properties may be prone to inaccuracies these results are encouraging and motivate applications to field data but significant issues remain to be resolved such as the determination of the generally unknown upgpr source function and identifying the optimal number of layers in the inversion models furthermore a relatively high level of prior knowledge is required to let the algorithm converge however we feel these are not insurmountable and the new technology has significant potential to improve field data analysis