itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

surface energy balance and melt thresholds over 11 years at taylor glacier antarctica 11 years ablation 18 cm a 1 was dominated by sublimation with very few occurrences of melt 42 days during 11 years results also indicated that above freezing air temperatures did not necessarily result in melt and in turn melt occurred during subfreezing air temperatures under some conditions for air temperatures near freezing low wind speed was critically important for melt initiation according to the model subsurface melt away from rocks and sediment in the ice occurred three times more frequently than surface melt occurs no deeper than 50 cm below the glacier surface and was small never exceeding 8 by mass the magnitude of subsurface melting and the energy balance indicate that taylor glacier ice is intermediate in optical properties between snow and blue ice

paleostress adjacent to the alpine fault broader implications from fault analysis near nelson south island new zealand stress tensor determinations from probable mio pliocene age minor faults along the edge of the richmond block northwest of the alpine fault system of south island show pervasive thrusting rather than strike slip motion as proposed in some analyses this study with results almost identical to that of nicol and wise 1992 on the other side of the alpine marlborough fault system shows that the present pattern of regional compression at high angles to the alpine fault has persisted through much of the neogene over a width of about 150 km normal to the alpine fault zone one explanation might be san andreas type models invoking strike slip motion concentrated in fault zones by highly lubricating gouge coupled with strain partitioning to allow compression in adjacent regions to act at high angles to strike such models are difficult to apply to the new zealand example which now must include deformed forelands on either side of the zone but which shows little or no strike slip motion instead a model is proposed for a crustal scale flower structure to accommodate the along strike convergence of opposite dipping subducting plates a regional surface slab comprising marlborough and its adjacent forelands is undergoing compression normal to the strike of the system while semidetached deeper plate motion accommodates most of the fundamental converging oblique strike slip displacements

paleostress adjacent to the alpine fault of new zealand fault vein and styolite data from the doctors dome area doctors dome 75 km north of christchurch new zealand is an early pleistocene to recent structure being deformed along the southeast edge of the pacific australian plate boundary paleostress in the area has been determined in basement rocks of the mesozoic meta graywacke torlesse supergroup which lies unconformably beneath cretaceous and younger cover rocks pre late cretaceous multiple folding and bedding plane faulting produced a complex low grade metasedimentary basement with predominantly steeply plunging fold hinges and largely isotropic overall behavior with respect to later deformation probable late cretaceous wnw ese shortening and nne wsw extension of the basement produced widespread laumontite calcite and silica veins widespread but sparse slickensided minor fault surfaces are probably related to the same stress system during the late cenozoic dome stage basement was uplifted rotated and severely thrust along some of the range fronts to produce local high concentrations of small slickensided surfaces in the frontal areas inversion of basement fault data for the area indicates a general northwest compression with two peaks one wnw ese parallel to the shortening suggested by the older vein system and the other parallel to southeast northwest stylolite columns in the cover rocks this direction is approximately parallel to regional indicators of contemporary deformation in and adjacent to the alpine fault zone and suggests that the stress field affecting these rocks has not changed significantly since the late pliocene early pleistocene like the san andreas system this compression is at a high angle to the strike of the zone as a whole but is compatible with the direction of plate convergence and motion of the major faults between the overlapping ends of the alpine fault and the hikurangi subduction zone the alpine fault may become subhorizontal at middle lower crustal levels partially decoupling the crust from underlying structures and thus allowing oblique motion to be transferred directly onto the fault from the subduction complex while aiding the change from subduction to continental collision

the nature of the plate interface and driving force of interseismic deformation in the new zealand plate boundary zone revealed by the continuous gps velocity field 1 new zealand straddles the boundary between the australian and pacific plates cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation with displacements on individual faults up to hundreds of kilometers however over periods of several years gps measurements show a remarkably smooth pattern of velocities we show here using a new method of back slip analysis that almost the entire plate boundary continuous gps velocity field can be predicted within measurement error from a simple model of elastic distortion due to deep slip on a single plate interface megathrust in the hikurangi and putsegur subduction zones or fault through continental lithosphere beneath the southern alps at the relative plate motion rates this suggests that the main driving force of plate boundary deformation is slip on the deeper moving part of the plate interface without buried creep in localized shear zones beneath individual surface faults the depth at which this deep slip terminates locking point line determines the width of deformation along the hikurangi margin there is also clockwise rotation of 150 km long segment of the fore arc wairoa domain at 4 5 1 ma relative to the australian plate about a pole in western north island model residuals in the velocity field are mainly a result of incomplete averaging of the cycle of slow slip events on the plate interface downdip of the locking point

geomorphology and ecology unifying themes for complex systems in biogeomorphology the interaction of geomorphic and ecologic landscape components has been largely conceptualized as independent in one direction geomorphic processes and landforms shape the distribution of biota conversely in the other direction biota modify geomorphic processes and landforms increasingly the interactions between geomorphic and ecological components are more circular and developmentally intertwined in this paper i integrate these two independent perspectives within the framework of complexity theory i outline four themes that characterize complex systems in biogeomorphology multiple causality and the concept of recursivity the influence of organisms that function as ecosystem engineers the expression of an ecological topology and ecological memory implicit in all of these themes is the recognition that biogeomorphic systems are open and path dependent they may exhibit a range of assembly states from self reinforcing stability domains to more transient configurations of organisms and environment

biogeomorphology and landscape evolution the problem of scale abstract vegetation may vary continuously and rapidly while landforms sometimes vary episodically and relatively slowly this disparity in temporal scales creates scale linkage problems in dealing with landform vegetation interactions four theoretical approaches for coping with these issues are outlined and illustrated via applications to problems arising from fieldwork on the coastal plain of north carolina the first approach the transient form ratio is used to determine whether ecosystems and geomorphic environments preserved in pleistocene stratigraphy represent stable landform ecosystem combinations which should reflect landform and vegetation responses to sea level rise the second the information criterion is applied to estimate the appropriate time steps for simulation modelling and appropriate spatial resolutions for field studies of vegetation effects on soil thickness in coastal plain uplands the abstracted systems argument the third approach is used to show that alluvial sedimentation and floodplain ecological dynamics cannot be considered independently in studies of floodplain system response to post european settlement finally ratios of relaxation times and durations suggest that changes in upland erosion regimes associated with historical devegetation are best treated as a singular perturbation in the context of quaternary landscape evolution

determination of stress from slip data faults and folds a new technique is derived to invert slickenside data for the stress field that caused the faulting episode this inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes at the time of rupture is similar study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes comparison of the inversion results with the geometry of the folds shows this application to be successful greatly increasing the number of data sets that can be used to find the paleostress field

review of the status and mass changes of himalayan karakoram glaciers we present a comprehensive review of the status and changes in glacier length since the 1850s area and mass since the 1960s along the himalayan karakoram hk region and their climate change context a quantitative reliability classification of the field based mass balance series is developed glaciological mass balances agree better with remotely sensed balances when we make an objective systematic exclusion of likely flawed mass balance series the himalayan mean glaciological mass budget was similar to the global average until 2000 and likely less negative after 2000 mass wastage in the himalaya resulted in increasing debris cover the growth of glacial lakes and possibly decreasing ice velocities geodetic measurements indicate nearly balanced mass budgets for karakoram glaciers since the 1970s consistent with the unchanged extent of supraglacial debris cover himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short wave radiation balance melt contributions from hk glaciers should increase until 2050 and then decrease though a wide range of present day area and volume estimates propagates large uncertainties in the future runoff this review reflects an increasing understanding of hk glaciers and highlights the remaining challenges

frictional properties and 3 d stress analysis of the southern alpine fault new zealand abstract new zealand s alpine fault af ruptures quasi periodically in large magnitude earthquakes paleoseismological evidence suggests that about half of all recognized af earthquakes terminated at the boundary between the central and south westland sections of the fault there fault geometry and the polarity of uplift change the south westland af exhibits oblique normal fault motion on a structure oriented 052 82 se that for at least 35 km along strike contains saponite rich principal slip zone gouges new hydrothermal friction experiments reveal that the saponite fault gouge is frictionally weak exhibiting friction coefficients between 0 12 and 0 16 for a range of temperatures t 25 210 c and effective normal stresses n 31 2 93 6 mpa the saponite gouge is rate strengthening in all velocity steps performed at velocities between 0 01 and 3 0 m s behavior conducive to aseismic creep a three dimensional stress analysis shows that the south westland af is favorably oriented with respect to the regional stress field for slip within the frictionally weak saponite fault gouge geometrically the fault is severely misoriented for slip in any fault forming materials with friction coefficients exceeding 0 5 the combination of weak gouges prone to aseismic creep strong asperities and low resolved shear stress may impede earthquake rupture propagation along the south westland alpine fault

the effects of seasonal changes to in stream vegetation cover on patterns of flow and accumulation of sediment abstract in stream macrophytes are typically abundant in nutrient rich chalk streams during the spring and summer months and modify the in stream environment by altering river flows and trapping sediments we present results from an inter disciplinary study of two river reaches in the river frome catchment dorset uk the investigation focused on how ranunculus water crowfoot the dominant submerged macrophyte in the study reaches modified patterns of flow and sediment deposition measurements were taken on a monthly basis throughout 2003 to determine seasonal patterns in macrophyte cover associated changes in the distributions of flow velocities and the character and amount of accumulated fine sediment within stands of ranunculus maximum in stream cover of macrophytes exceeded 70 at both sites flow velocities were less than 0 1 m s 1 within the stands of ranunculus and accelerated to 0 8 m s 1 outside the stands during the early stages of the growth of ranunculus fine sediment mostly accumulated within the upstream section of the plant but the area of fine sediment accumulation extended into the downstream trailing section of the plant later in the growing season the fine sediment accumulations were dominated by sand 63 1000 m with silts and clays 0 37 63 m comprising

interaction between neighboring vegetation patches impact on flow and deposition flow and sedimentation around patches of vegetation are important to landscape evolution and a better understanding of these processes would facilitate more effective river restoration and wetlands engineering in wetlands and channels patches of vegetation are rarely isolated and neighboring patches influence one another during their development in this experimental study an adjacent pair of emergent vegetation patches were modeled by circular arrays of cylinders with their centers aligned in a direction that was perpendicular to the flow direction the flow and deposition patterns behind the pair of patches were measured for two stem densities and for different patch separations gap widths the wake pattern immediately behind each individual patch was similar to that observed behind an isolated patch with a velocity minimum directly behind each patch that produced a well defined region of enhanced deposition in line with the patch for all gap widths the velocity on the centerline between the patches uc was elevated to a peak velocity umax that persisted over a distance lj although umax was not a function of lj decreased with decreasing beyond lj the wakes merged and uc decayed to a local minimum the merging of wakes and associated velocity minimum produced a local maximum in deposition downstream from and on the centerline between the patches if this secondary region of enhanced deposition promotes new vegetation growth the increased drag on the centerline could slow velocity between the upstream patch pair leading to conditions favorable to their merger

hydrology of debris covered glaciers in high mountain asia abstract the hydrological characteristics of debris covered glaciers are known to be fundamentally different from those of clean ice glaciers even within the same climatological geological and geomorphological setting understanding how these characteristics influence the timing and magnitude of meltwater discharge is particularly important for regions where downstream communities rely on this resource for sanitation irrigation and hydropower such as high mountain asia the hydrology of debris covered glaciers is complex rugged surface topographies typically route meltwater through compound supraglacial englacial systems involving both channels and ponds as well as pathways that remain unknown low gradient tongues that extend several kilometres retard water conveyance and promote englacial storage englacial conduits are frequently abandoned and reactivated as water supply changes new lines of permeability are exploited and drainage is captured due to high rates of surface and subsurface change seasonal influences such as the monsoon are superimposed on these distinctive characteristics reorganising surface and subsurface drainage rapidly from one season to the next recent advances in understanding have mostly come from studies aimed at quantifying and describing supraglacial processes little is known about the subsurface hydrology particularly the nature or even existence of subglacial drainage in this review we consider in turn the supraglacial englacial subglacial and proglacial hydrological domains of debris covered glaciers in high mountain asia we summarise different lines of evidence to establish the current state of knowledge and in doing so identify major knowledge gaps finally we use this information to suggest six themes for future hydrological research at high mountain asian debris covered glaciers in order to make timely long term predictions of changes in the water they supply

reconstruction of surface air temperature in a glaciated region in the western qilian mountains tibetan plateau 1957 2013 and its variation characteristics abstract based on the meteorological observations at three sites 4180 m 4550 m and 5040 m a s l in laohugou and the surrounding 7 national meteorological stations the long term surface air temperature of the glaciated region in the qilian mountains northeastern tibetan plateau during 1957 2013 was reconstructed the in situ air temperature observed at 4180 m during 1959 1961 was used to verify the reconstructed temperature series several approaches of multiple regressions were applied to select the optimal method in estimating the daily air temperature including the ordinary least square regression olsr stepwise regression sr principal component regression pcr and partial least squares regression plsr respectively according to root mean square error mean bias error and correlation coefficient olsr is selected as the optimal approach in the study region the reconstructed daily temperature correlates well with the synchronous observations and correlation coefficients are higher than 0 96 p p

focal mechanisms of large earthquakes in the south island of new zealand implications for the accommodation of pacific australia plate motion b the plate motion model nuvel 1 predicts oblique convergence between the pacific and australian plates in the south island of new zealand we used p and sh body waveform analysis to constrain the focal mechanisms of the 15 largest earthquakes ms 5 8 that have occurred in this region since 1964 in order to see how the plate motion is accommodated at the southern end of the alpine fault convergence is achieved by oblique slip movement along a concentrated zone of deformation in the southern offshore region one event may be related to thrusting of the australian plate beneath the pacific plate and another strike slip event probably demonstrates movement on an active strike slip fault system parallel to but offset from the southern limit of the alpine fault this geometry provides a possible mechanism for the rapid uplift of the fiordland region deformation in the northern south island is more distributed in the south west marlborough region partitioning occurs between strike slip faulting in the se and reverse faulting farther nw in the buller region we suggest that the partitioning developed as a consequence of an increasing component of shortening that was accommodated by slip on reactivated pre existing normal faults in the buller region shortening in the buller region may have deflected the ne end of the alpine fault towards the nw forming the prominent bend the marlborough fault system with its youngest and most active faults to the se probably developed in an attempt to maintain a through going strike slip structure as each of the strike slip faults was transported towards the north west partitioning of the opposite polarity with reverse faulting se of the strike slip faulting occurs in north east marlborough the boundary between the two different styles of partitioning in ne and sw marlborough appears to coincide with a change in the nature of the downgoing slab and a change in strike of faults of the marlborough fault system a normal faulting earthquake on the northern edge of the chatham rise probably results from a complex interaction of the buoyant continental crust in that region with the subduction zone and the overlying marlborough fault system

warming glacier melt and surface energy budget from weather station observations in the melville bay region of northwest greenland the glaciers in the melville bay region of northwest greenland have shown a mean retreat since the earliest observations at the beginning of the 20th century the largest steenstrup gletscher has retreated 20 km partly during the period of atmospheric cooling 1940 80 melville bay air temperature observations starting in 1981 indicate a regional change of 0 208 ca 1 this exceeds the warming on the east coast of greenland confirming the west coast to be a region of relatively large change also in a global perspective the largest temperature increase is observed in the winter months 0 3 0 48 ca 1 results from a 4 year 2004 08 net ablation record obtained by an automatic weather station aws near the calving front of steenstrup gletscher show an ablation rate that is relatively low for a low elevation position on the greenland ice sheet 2 4 m ice equivalent per year a first order estimate from positive degree day totals suggests that net ablation has roughly doubled since the 1980s a surface energy and mass balance model is applied to the steenstrup aws data to quantify the energy flux contributions to surface melt solar radiation is the main source for melt energy but due to shortwave radiation penetration into the ice only one third of the melt takes place at the glacier surface nearly two thirds occurs within the upper ice layers

the motion of crustal blocks driven by flow of the lower lithosphere and implications for slip rates of continental strike slip faults geodetic measurements in actively deforming areas of the continents reveal the pattern of deformation in the lithosphere if the dominant forces acting on crustal blocks are tractions at their bases then the long term motion of each block will be given by the average velocity of the underlying lithosphere slip rates between blocks estimated in this way from recent geodetic measurements across fault zones in the south island of new zealand and southern california are in good agreement with slip rates estimated geologically

effects of clouds on surface melting of laohugou glacier no 12 western qilian mountains china we analyzed a 2 year time series of meteorological data january 2011 december 2012 from three automatic weather stations on laohugou glacier no 12 western qilian mountains china air temperature humidity and incoming radiation were significantly correlated between the three sites while wind speed and direction were not in this work we focus on the effects of clouds on other meteorological parameters and on glacier melt on an average 18 of top of atmosphere shortwave radiation was attenuated by the clear sky atmosphere and clouds attenuated a further 12 most of the time the monthly average increases in net longwave radiation caused by clouds were larger than decreases in net shortwave radiation but there was a tendency to lose energy during the daytime when melting was most intense air temperature and wind speed related to turbulent heat flux were found to suppress glacier melt during cloudy periods while increased water vapor pressure during cloudy days could enhance glacier melt by reducing energy loss by latent heat from these results we have increased the physical understanding of the significance of cloud effects on continental glaciers

strain distribution across the australian pacific plate boundary in the central south island new zealand from 1992 gps and earlier terrestrial observations as part of a geodetic experiment aimed at understanding the deformation associated with the australian pacific plate boundary in the south island of new zealand in 1992 we reoccupied using global positioning system gps techniques a first order triangulation and trilateration network established in 1978 between christchurch on the east coast and hokitika on the west the network crosses the south island a few tens of kilometers southwest of the region where the plate boundary changes from a single throughgoing oblique slip fault the alpine fault to a series of subparallel strike slip faults the marlborough faults the gps data have been analyzed as daily network solutions with about 12 stations in each solution rms repeatabilities for stations with multiple occupations are 4 mm 8 mm and 15 mm in the north east and vertical components respectively the observed strain across the network is consistent with the entire nuvel ia pacific australia plate velocity being accommodated on land across this part of the south island shear strain rates derived from the gps and terrestrial data show that the highest strain rate 0 4 rad yr occurs in the region of the southern alps and alpine fault this rate is about two thirds of the rate predicted from the nuvel ia plate velocity model assuming that all the plate boundary deformation occurs across this region implying that about two thirds of the plate motion is accommodated in the vicinity of the alpine fault significant shear strain rates greater than 0 2 rad yr are also observed farther east particularly in the region of the porters pass amberley fault zone demonstrating that this zone accommodates a significant part of the plate boundary deformation using dislocation modeling we show that the variation in fault parallel shear strain rates across the alpine fault is reasonably consistent with a nonoptimized dislocation model involving a 50 dipping fault that is presently locked to a depth of 12 km one explanation for this observation is that the upper 12 km of the crust in this area is storing most of the right lateral shear component of the relative plate motion as elastic energy that will be released in a future major earthquake the variation in the other component of shear strain which may be interpreted as fault normal relative contraction is not explained by a simple dislocation model implying that the normal component of plate motion is taken up in other ways

a focused look at the alpine fault new zealand seismicity focal mechanisms and stress observations the alpine fault is the pacific australian plate boundary in the south island of new zealand this study analyzes 195 earthquakes recorded during the 6 month duration of the southern alps passive seismic experiment sapse in 1995 1996 and two mr 5 0 earthquakes and aftershocks in 1997 which occurred close to the central part of the alpine fault precise earthquake locations are derived by simultaneous inversion for hypocenter parameters a one dimensional velocity model and station corrections together with focal mechanisms calculated using a first motion and amplitude ratio method these results provide a picture of the seismotectonics in the central south island over a 6 month period moment tensor inversions of three earthquakes provide an independent means of comparison to the focal mechanisms derived using the amplitude first motion method to validate our observations over time we compare the sapse seismicity with the seismicity recorded by the new zealand national seismic network nznsn and a local network at lake pukaki east of the southern alps 6 months versus 8 years our study indicates that the alpine fault releases elastic strain seismically from the surface down to 10 12 km depth between milford sound in the south and the hope fault in the north the seismicity rate of the alpine fault is low but comparable to locked sections of the san andreas fault with large earthquakes expected seismicity decreases north of bruce bay at the alpine fault and within a triangular region along the alpine fault located between the hope and porters pass fault zones we interpret this as the result of deformation distributed on the alpine fault and the hope and porters pass fault zones the base of the seismogenic zone is fairly uniform at 12 km 2km over large parts of the south island the high alps region has a shallower base of the seismogenic zone indicating localized elevated temperatures east of the alpine fault most of the study region deforms under a uniform stress field with a maximum principal horizontal shortening direction of 110o 120 o similar to geodetic observations and plate motions this confirms that the region is not undergoing strain partitioning the earthquake data show that the deformation away from the alpine fault is distributed on mainly nne trending thrust faults and strike slip transfer faults with a maximum seismogenic depth of 12km

contemporary horizontal velocity and strain rate fields of the pacific australian plate boundary zone through new zealand we have inverted velocity solutions from nine geodetic networks distributed across new zealand to derive present day continuous horizontal velocity and strain rate fields at the earth s surface throughout the country the nine networks contain a total of 362 global positioning system gps stations that have been observed at least twice and at least a year apart between 1991 and 1998 the model velocity field is expanded as bicubic spline interpolation functions defined within a curvilinear grid that covers the country and extends into the assumed rigid australian and pacific plates to west and east the inversion jointly minimizes the magnitudes of fitted strain rates and the misfit to the observed velocity data the spline technique allows high spatial resolution of strain rate variations especially in regions with spatially dense gps data expansion of the model velocity field on the surface of a sphere allows arbitrarily large areas to be studied previously known aspects of new zealand plate boundary deformation are highlighted with improved resolution including back arc extension in the taupo volcanic zone rotation of the hikurangi forearc away from this zone in the north island and a band of high shear strain rate under the southern alps to the southeast of the alpine fault our results reveal several new features including a region of enhanced shear straining apparently associated with strike slip faults in the southern north island and a band of contractional straining subparallel and well east of the alpine fault that is similar to features found in numerical and sandbox models of continental collision

a bayesian approach to determining and parametrizing earthquake focal mechanisms summary we develop a new probabilistic bayesian method for estimating the distribution of focal mechanism parameters based on seismic wave polarity data we investigate the use of generalized matrix fisher distributions for parametrizing focal mechanism uncertainties the advantages of our approach are that it 1 models the data generation process and incorporates observational errors particularly those arising from imperfectly known earthquake locations 2 allows exploration of the entire parameter space 3 leads to natural point estimates of focal mechanism parameters 4 allows the inclusion of a priori information about the focal mechanism parameters and 5 allows the resulting posterior pdf to be well approximated by generalized matrix fisher distributions we present here the results of our method in two situations we first consider the case in which the seismic velocity of the region of interest described by a velocity model is presumed to be precisely known with application to seismic data from the raukumara peninsula new zealand we then consider the case in which the velocity model is imperfectly known with application to data from the kawerau region new zealand we find that our estimated focal mechanism solutions are for the most part consistent with all available polarity data and correspond closely to solutions obtained using established methods further the generalized matrix fisher distributions we examine provide a good fit to our bayesian posterior pdf of the focal mechanism parameters finally we demonstrate how informative prior distributions on focal mechanism parameters can be incorporated into our model

behavior of the brittle crust in wide plate boundary zones in wide and active continental plate boundary zones ductile flow in the deeper and strong parts of the lithosphere may control crustal deformation this is likely if average resistive shear stresses on faults in the brittle crust are much less than 108 pa and the underlying bulk effective viscosity is much greater than 1021 pa s in this case a simple model of distributed deformation referred to as the floating block model may be useful this treats the crust as an array of rotating and translating rigid blocks which are floating on an underlying continuous flow with a constant rheology the model is analyzed in detail in this paper because it has the potential to link detailed observations of crustal deformation with the large scale flow crustal blocks are defined by at least two sets of faults the kinematics of crustal deformation can be described in terms of the motions of these blocks both the relative motion on block boundaries faults and block tilting about a horizontal axis can be described in terms of the underlying flow and block rotation about a vertical axis however rotations about a vertical axis which are an important component of the crustal deformation will depend not only on the underlying flow but also on the shape orientation and arrangement of the crustal blocks the average rotation rate about a vertical axis over finite rotations will be significantly different from that predicted at any instant also the rotation history is considerably complicated if as is likely the underlying flow field or block shape has changed with time these aspects of crustal deformation are discussed with reference to real zones of active deformation in new zealand greece and western north america

the dynamics of western north america stress magnitudes and the relative role of gravitational potential energy plate interaction at the boundary and basal tractions summary we investigate the forces involved in driving long term large scale continental deformation in western north america and quantify the vertically averaged deviatoric stress field arising from internal buoyancy forces and the accommodation of relative plate motions in addition we investigate the ability of regional models to resolve the level of tractions acting at the base of the lithosphere we directly solve force balance equations for vertically averaged deviatoric stresses associated with differences in values of 1 lithospheric thickness times the gravitational potential energy per unit area gpe the gpe values are inferred using both the etopo5 topographic data set and the crust2 0 crustal thickness model deviatoric stresses associated with basal tractions are calculated globally with inputs determined from an isoviscous upper mantle 10 21 pa s 3 d large scale convection model in which mantle density variations were inferred from tomographic data and the history of subduction in a 211parameter iterative inversion we then solve for a stress field boundary condition by fitting stress field indicators i e the directions and relative magnitudes of the principal axes of kinematic strain rates magnitudes of the total vertically averaged deviatoric stress field sum of gpe solution with the boundary condition solution range from 5 to 10 mpa within a 100 km thick lithosphere these magnitudes are calibrated by the gpe differences along with the spatial variation in deformation style there is a trade off between the scaling of the basal traction deviatoric stress field and the boundary condition solution however the combined boundary conditions plus basal traction solution is robust in both magnitude and style and when added to the contribution from gpe differences provides a global minimum of misfit between the total deviatoric stress solution and the stress field indicators gpe variations account for 50 per cent of the deviatoric stress magnitudes driving deformation while boundary condition stresses account for the remaining 50 per cent of deviatoric stress magnitude by comparing possible end member strength profiles with our vertically averaged deviatoric stresses we infer that the bulk of the strength within the lithosphere in western north america lies within the brittle seismogenic layer

mechanical evolution of transpression zones affected by fault interactions insights from 3d elasto plastic finite element models abstract the mechanical evolution of transpression zones affected by fault interactions is investigated by a 3d elasto plastic mechanical model solved with the finite element method ductile transpression between non rigid walls implies an upward and lateral extrusion the model results demonstrate that a transpression zone evolves in a 3d strain field along non coaxial strain paths distributed plastic strain slip transfer and maximum plastic strain occur within the transpression zone outside the transpression zone fault slip is reduced because deformation is accommodated by distributed plastic shear with progressive deformation the 3 axis the minimum compressive stress rotates within the transpression zone to form an oblique angle to the regional transport direction 9 10 the magnitude of displacement increases faster within the transpression zone than outside it rotation of the displacement vectors of oblique convergence with time suggests that transpression zone evolves toward an overall non plane strain deformation the slip decreases along fault segments and with increasing depth this can be attributed to the accommodation of bulk shortening over adjacent fault segments the model result shows an almost symmetrical domal uplift due to off fault deformation generating a doubly plunging fold and a positive flower structure outside the overlap zone expanding asymmetric basins subside to negative flower structures on both sides of the transpression zone and are called transpressional basins deflection at fault segments causes the fault dip fall to less than 90 86 89 near the surface 1 5 km this results in a pure shear dominated triclinic and discontinuous heterogeneous flow of the transpression zone

energy and mass balance of zhadang glacier surface central tibetan plateau climate variables that control the annual cycle of the surface energy and mass balance on zhadang glacier in the central tibetan plateau were examined over a 2 year period using a physically based energy balance model forced by routine meteorological data the modelled results agree with measured values of albedo incoming longwave radiation surface temperature and surface level of the glacier for the whole observation period the radiation component dominated 82 the total surface energy heat fluxes this was followed by turbulent sensible 10 and latent heat 6 fluxes subsurface heat flux represented a very minor proportion 2 of the total heat flux the sensitivity of specific mass balance was examined by perturbations of temperature 1 k relative humidity 20 and precipitation 20 the results indicate that the specific mass balance is more sensitive to changes in precipitation than to other variables the main seasonal variations in the energy balance were in the two radiation components net shortwave radiation and net longwave radiation and these controlled whether surface melting occurred a dramatic difference in summer mass balance between 2010 and 2011 indicates that the glacier surface mass balance was closely related to precipitation seasonality and form proportion of snowfall and rainfall

ice ablation and meteorological conditions on the debris covered area of baltoro glacier karakoram pakistan during the recent italian expedition k2 2004 50 years later june july 2004 on baltoro glacier karakoram pakistan glaciological field experiments were carried out on the debris covered area of this high elevation glacier the aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at urdukas 4022 m a s l and at k2 base camp 5033 m a s l in addition temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance r using the air temperature the local mean lapse rate 0 00758 cm 1 and the measured ablation the degree day factors k at different locations on the glacier were calculated the ice ablation rates were related to debris thickness and elevation they are typically on the order of 4 cm d 1 during the observation period however it was found that the surface topography slope aspect has an influence on the total ablation similar to that of the debris thickness thermal resistance of the debris cover and its distribution over the glacier were estimated finally a best guess estimate of the total meltwater production was calculated from available climate data

vegetation modulated landscape evolution effects of vegetation on landscape processes drainage density and topography 1 topography acts as a template for numerous landscape processes that include hydrologic ecologic and biologic phenomena these processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes we have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches vegetation is assumed to form a uniform ground cover runoff erosion is modeled based on a power function of excess shear stress in which shear stress efficiency is inversely proportional to vegetation cover this approach is validated using data plant effect on slope stability is represented by additional cohesion provided by plant roots vegetation cover is assumed to reduce sediment transport rates due to physical creep processes rainsplash dry ravel and expansion and contraction of sediments according to a negative exponential relationship vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances runoff erosion and landsliding and wildfires analytical results suggest that in an equilibrium basin with a fixed vegetation cover plants may cause a transition in the dominant erosion process at the channel head a runoff erosion dominated landscape under none or poor vegetation cover may become landslide dominated under a denser vegetation cover the sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena with model parameter values representative of the oregon coast range ocr numerical experiments conducted using the channel hillslope integrated landscape development child model confirm the findings based on the analytical theory a highly dissected fluvial landscape emerges when surface is assumed bare when vegetation cover is modeled landscape relief increases resulting in hollow erosion dominated by landsliding interestingly our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure simulated landscapes resemble real world catchments in the ocr when such disturbances are considered

mass balance and a glacier surge of guliya ice cap in the western kunlun shan between 2005 and 2015 abstract contemporary estimates of glacier changes are necessary to assess the impact of climate change associated hazards and water resources management glaciers in high mountain asia hma are mostly retreating except the karakoram and western kunlun shan confirmed by remote sensing measurements however ground validation with precise measurements of these mass balance estimates are scarce this study selected guliya ice cap in the western kunlun shan to observe its recent changes regarding surface dynamics and mass balance using aster dem of 2005 and 2015 our findings indicate that one of the north facing glaciers surged with no previous surging history during july and early november 2015 advancing at about 8 m per day on average the mass balance shows a balance condition 0 01 0 02 m w e a 1 the icesat data 2004 2008 at selected locations compared to dgps data collected in the field during 2015 indicating a minute difference of 0 03 0 05 m a 1 with aster data in the same area our findings suggest that guliya ice cap in the western kunlun shan is in equilibrium state following a similar pattern mass gain or stable conditions as observed previously

origin of small scale segmentation and transpressional thrusting along the alpine fault new zealand the alpine fault is the major structural feature of the australian pacific plate boundary in the south island of new zealand geologic evidence suggests that half to three quarters of the plate boundary displacement is accommodated by movement on the fault detailed investigation of the central section of the alpine fault has revealed that it consists of oblique thrust sections striking 020 050 that are linked by subvertical right lateral faults striking between 065 and 090 the segmentation is on a scale of 1 10 km similarly oriented right lateral faults are abundant southeast of the alpine fault and are consistent with stresses induced in an elastic layer by an oblique slip ductile fault zone below propagation of the fault to the surface is predicted to result in an en echelon arrangement of strike slip and thrust segments it is suggested that the spatial distribution of segments is affected by the existence of deeply incised valleys in the hanging wall that disturb the stress field to depths of 1 4 km the segmentation is near surface and does not appear to act as a barrier to the propagation of large earthquakes

ablation modeling and surface energy budget in the ablation zone of laohugou glacier no 12 western qilian mountains china glacier surface melting can be described using energy balance models we conducted a surface energy budget experiment to quantify surface energy fluxes and to identify factors affecting glacial melt in the ablation zone of laohugou glacier no 12 western qilian mountains the surface energy budget was calculated based on data from an automatic weather station and turbulent fluxes calculated using the bulk aerodynamic approach were corrected using measurements from an eddy covariance system simulated mass balances were validated by stake observations net shortwave radiation was the primary component of the surface energy balance 126 w m 2 followed by sensible heat flux net longwave radiation 45 w m 2 and latent heat flux 12 8 w m 2 represented heat sinks the bulk aerodynamic method underestimated sensible and latent heat fluxes by 3 4 and 1 2 w m 2 respectively the simulated total mass balance of 1703 mm w e exceeded the observed total by 90 mm w e daily positive accumulated temperature and low albedo were the main factors accelerating glacier melt an uncertainty assessment showed that mass balance was very sensitive to albedo and varied by 36 when albedo changed by 0 1

continental fault structure and the shallow earthquake source plate boundaries in continental crust are generally less sharply defined than in the oceans with seismicity spread over broad areas interplate displacements appear to be largely accommodated by networks of major fault zones a simple 2 level model for these important structures accounts for the depth distribution of most continental earthquakes and for the observed range of faulting styles and associated rock deformation textures the model consists of a seismogenic frictional slip regime overlying quasi plastic mylonite belts wherein shearing is largely accommodated aseismically due mainly to the changing response of quartz to deformation with increasing temperature shear resistance increases with depth to a peak value in the vicinity of the frictiona1 quasi plastic transition and then decreases rapidly the depth to which microseismic activity extends appears inversely related to regional heat flow and can be satisfactorily modelled as the frictional quasi plastic transition for different geotherms using laboratory determined flow laws for quartz bearing rocks larger earthquake ruptures m 5 5 tend to nucleate near the base of the seismogenic regime in the region inferred to have the highest shear resistance and concentration of distortional strain energy consideration is also given to the depression of isotherms and seismic activity in regions of thrusting and to the question of the downward continuation of major fault zones through the lithosphere decoupling of the upper crust on flat lying shear zones may accompany higher level dip slip and perhaps in some circumstances strike slip faulting being favoured by above average continental heat flow and a high quartz content in the middle or deep crust the average level of deviatoric stress within the seismogenic regime remains an outstanding problem

detailed spatiotemporal analysis of the tectonic stress regime near the central alpine fault new zealand abstract we construct a new data set of 845 focal mechanisms derived from microseismicity recorded between late 2008 and early 2017 to investigate the state of stress near the central alpine fault a major obliquely convergent plate boundary fault we obtain an average maximum horizontal compressive stress orientation shmax of 121 11 which is uniform to first order along the length of the central southern alps we also make use of the local magnitudes of the earthquakes with focal mechanisms to examine the spatial patterns of seismic moment release and obtain a relatively uniform cumulative seismic moment release distribution adjacent to the central alpine fault which appears to be independent of both the perpendicular and parallel distances to the fault we observe an average angle between shmax and the alpine fault of 66 which is consistent with previous observations in the northern and southern sections of the alpine fault this result implies that central alpine fault is not optimally oriented for reactivation detailed temporal investigations using two different approaches did not show any systematic change of the stress parameters with time we also examine the distribution of the shear to normal stress ratio on the fault and do not observe any significant spatial variation along the alpine fault this lack of variation combined with the high angle between the fault strike and shmax implies that the fault is unfavourably oriented for slip

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

andersonian wrench faulting in a regional stress field during the 2010 2011 canterbury new zealand earthquake sequence the initial mw7 1 darfield earthquake sequence was centred west of christchurch city in the south island of new zealand but aftershocks including a highly destructive mw6 3 event eventually extended eastwards across the city to the coast the mainshock gave rise to right lateral strike slip of up to 5 m along the segmented rupture trace of a subvertical fault trending 085 58 across the canterbury plains for c 30 km in agreement with teleseismic focal mechan isms near field data however suggest that the mainshock was composite initiating with reverse slip north of the surface rupture stress determinations for the central south island show maximum compressive stress s1 to be horizontal and oriented 115 58 the principal dextral rupture there fore lies at c 3 08 to regional s1 the classic andersonian orientation for a low displacement wrench fault an aftershock lineament trending c 1458 possibly represents a conjugate left lateral strike slip structure this stress field is also consistent with predominantly reverse slip reactivation of nne ne faults along the southern alps range front the main strike slip fault appears to have a low cumulative displacement and may represent either a fairly newly formed fault in the regional stress field or an existing subvertical fault that happens to be optimally oriented for frictional reactivation

stress field and kinematics for diffuse microseismicity in a zone of continental transpression south island new zealand we analyze shallow 0 20 km microseismicity adjacent to the alpine fault in new zealand where there is oblique convergence of the australian and pacific plates focal mechanisms for 155 earthquakes june 2012 october 2013 are inverted to determine the orientation of the stress field this yields a principal horizontal axis of compression shmax 114 10 which cannot be explained in terms of the sum of stress from tectonic loading due to plate convergence indicated by gps observations and gravitational stresses the azimuth of slip vectors for individual focal mechanisms cluster perpendicular and parallel to the plate convergence vector these faults however strike at 45 to shmax from the stress inversion suggesting a very low coefficient of friction the earthquake slip directions may be kinematically controlled accommodating the plate convergence on a limited set of fractures similar to the segmentation for neotectonic faulting along the alpine fault which is partitioned into strike slip and thrust segments at a 1 10 km scale we suggest two possible controls on our calculated shmax azimuths firstly there may be a slight clockwise bias in the estimates of shmax from earthquakes slip may be occurring on a more limited range of fractures than assumed by the stress inversion method although this effect is likely to be relatively small 5 more importantly the components of the stress field may be relieved at different time scales during big earthquakes resulting in a residual stress field that varies significantly 15 on timescales of several large earthquakes

thermochronological evidence of a low angle mid crustal detachment plane beneath the central south island new zealand oblique continental convergence and uplift in the southern alps new zealand is largely accommodated by dextral transpression on the alpine fault however towards the south of the orogen the alpine fault becomes increasingly strike slip despite evidence for high exhumation rates in the pacific plate here we present 41 new apatite and zircon fission track ages to investigate the role of the southern alpine fault in pacific plate exhumation since the miocene through development of a new maximum likelihood fission track age calculation method to overcome extremely low 0 1 ppm 238u concentrations in apatites we estimate the width of the fully reset apatite zone ages 5 ma southeast of the southern alpine fault which has been previously overestimated instead this zone is 30 km wide rather than 60 km we combine our exhumation profile with thermo kinematic modelling to impose constraints on fault kinematics and deformation history the surface cooling age pattern can be well reproduced by exhumation along a listric reverse fault which shallows to a low angle 6 10 mid crustal detachment beneath the southern lakes this structure is comparable to the listric central alpine fault geometry previously constrained by thermo kinematics models to the north of our study region we propose this detachment plane is continuous beneath a large region of central south island and may be acting to accommodate underthrusting of australian crust beneath the pacific plate this article is protected by copyright all rights reserved

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

a refined methodology for stress inversions of earthquake focal mechanisms we develop an improved methodology for reliable high resolution inversions of focal mechanisms to background stress field orientation and stress ratio r in two or three dimensions the earthquake catalog is declustered to remove events likely affected strongly by local stress interactions rather than reflecting the large scale background stress field the declustered data are discretized with the k means algorithm into groups containing a number of focal mechanisms between a minimum number nmin and 2nmin synthetic tests indicate that nmin 30 provides stable inversion results under different stress regimes and noise conditions when r 0 5 while nmin 45 is needed for r near 0 or 1 additional synthetic tests compare the performance of selecting the fault plane of each focal mechanism using a the plane with lowest misfit angle between the slip vector from the focal mechanism and shear traction from the stress tensor and b the plane with highest instability coefficient representing proximity to the optimally oriented fault for given stress field and friction coefficient the instability criterion is found to provide more accurate inversion results under all tested stress regimes stress ratios and noise conditions the refined inversion methodology combines selecting fault planes using the instability criterion iteratively with a damped simultaneous inversion of different focal mechanism groups results characterizing neighborhoods of discretized domains merged during the damped inversion provide high resolution information independent of the discretization some aspects of the methodology are illustrated with focal mechanism data from the san jacinto fault zone in southern california

spatial and temporal variations of the surface albedo and other factors influencing urumqi glacier no 1 in tien shan china glacier albedo controls the surface energy budget the variability of which affects the glacier surface melt rate and in turn impacts the mass balance of the glacier during 2013 and 2014 spatial and temporal variations of albedo were investigated using 18 landsat images of urumqi glacier no 1 factors influencing these spatiotemporal profiles were analyzed an established retrieval process including geolocation radiometric calibration atmospheric topographic and anisotropic correction and narrow to broadband conversion was applied for the first time to landsat 8 images differences between landsat image derived albedo values and albedo values measured using a handheld spectroradiometer ranged from 0 024 to 0 049 spatial and temporal variations of surface albedo were significant especially in the ablation area the variability of the values of ice albedo ranged from 0 06 to 0 44 due to topographic effects and light absorbing impurities the results suggest that this retrieval method can be used to investigate the spatial and temporal variability of surface albedo from landsat 8 images on mountain glaciers moreover as constant albedo values for ice and snow cannot be assumed the distribution of albedo was not completely dependent on altitude under conditions of more intense ablation and by reason of light absorbing impurities during the melt season

the glacier inventory of china following recommendations from the international commission on snow and ice for a world glacier inventory an inventory of glaciers in china was carried out by chinese glaciologists from 1978 to 2002 each glacier was measured from aerial photographs and topographical maps and 34 parameters recorded these parameters were then analyzed statistically for the various river systems in china twelve volumes of the glacier inventory of china gic have been published consisting of 22 parts in 21 books the data were subsequently abridged into a concise gic published in chinese 2005 and in english 2008 to make the glacier inventory more accessible and better adapted for assessing glacier response to climate change after the gic was completed new aerial photographs became available and remote sensing techniques became more common to investigate glacier changes since completion of the first gic a second glacier inventory of china was initiated in 2007 this 5 year project supported by the ministry of science and technology will be undertaken mainly using remote sensing techniques

on the forces driving plate tectonics inferences from absolute plate velocities and intraplate stress summary absolute plate motions and intraplate stress both serve as tests of models for the forces acting on plate boundaries plate velocities relative to a presumedly fixed underlying mantle are calculated from the hypothesis that no net torque is exerted on the lithosphere intraplate stress is calculated by solving the equilibrium equations for thin elastic shells in the membrane state of stress the absolute velocity fields predicted from a wide assortment of physical and geological models are all very similar while the global pattern of absolute velocity is probably close to those predicted by such models the absolute motions do not therefore provide a strong test of the driving mechanism comparison of predicted intraplate stress with the long wavelength features of the global stress field however as determined by in situ measurements earthquake mechanisms and stressinduced geological structures does prove to be a powerful test of possible driving forces all absolute velocity models have several interesting properties lithosphere in the equatorial half of the earth is moving significantly faster than lithosphere in the polar half some connection to the earth s rotation is implied since this statement is demonstrably untrue for co ordinate poles much different from the geographic pole subducted slabs are characterized by a slow horizontal translation perpendicular to strike that is independent of the plate convergence rate confounding attempts to explain the dip angles of benioff zones in terms of a uniform vertical sinking and a variable absolute velocity for the overthrust plate ridges must migrate at a wide range of velocities relative to their underlying source of new lithosphere such rapid migration may be a necessary but is not a sufficient condition for ridge jumps force models considered in velocity and stress calculations include driving forces at spreading centres and subduction zones and various parameterizations of drag at the base of the lithosphere from the rms absolute velocities of individual plates there is a weak indication that pull by subducted lithosphere at trenches is an important driving force and that drag may be greater beneath continental than oceanic lithosphere the predicted intraplate deviatoric stress cannot match the well determined stress fields in north america and europe unless the driving force exerted at ridges is at least comparable in magnitude to other forces in the system the mid plate stresses are very sensitive to the nature of drag at the base of the lithosphere and thus measured stresses may ultimately provide a sensitive test of absolute plate velocities

automatic glacier ablation measurements using pressure transducers an instrument is described that automatically records ice ablation while eliminating the need for ablation stakes a pressure transducer placed at the bottom of a hole drilled into the ice is connected by a hose to a bladder lying on the surface ice ablation is detected as a reduction in the hydrostatic pressure measured by the transducer

microseismicity and stress in the vicinity of the alpine fault central southern alps new zealand 1 we investigate present day microseismicity associated with the central alpine fault and the zone of active deformation and uplift in the central southern alps using 14 months of data robust hypocenter locations have been obtained for 1800 earthquakes of magnitudes between 0 3 and 4 2 we derived a magnitude scale with a frequency dependent attenuation factor f 0f where 0 1 89 0 02 10 3 s km that enables magnitudes to be calculated consistently for earthquakes of different sizes and frequency contents the maximum depth of the seismicity varies systematically with distance from the alpine fault from 10 2 km near the fault to 8 2 km within 20 km and 15 2 km further southeast this distribution correlates with lateral variations in crustal resistivity earthquake hypocenters are concentrated in areas of strong resistivity gradients and restricted to depths of resistivities 100 m rocks at greater depth are too hot too fluid saturated or too weak to produce detectable earthquakes focal mechanism solutions computed for 211 earthquakes ml 0 44 exhibit predominantly strike slip mechanisms we obtain a maximum horizontal compressive stress direction of 115 10 from focal mechanism inversion this azimuth is consistent with findings from elsewhere in the central and northern south island and indicates a uniform crustal stress field despite pronounced variations in crustal structure and topographic relief our stress estimates suggest that the alpine fault with a mean strike of 055 is poorly oriented in an andersonian sense but that individual thrust and strike slip segments of the fault s surface trace have close to optimal orientations

dynamics of the pacific north american plate boundary in the western united states the vertically averaged deviatoric stress tensor field within the western united states was determined with topographic data geoid data recent global positioning system observations and strain rate magnitudes and styles from quaternary faults gravitational potential energy differences control the large fault normal compression on the california coast deformation in the basin and range is driven in part by gravitational potential energy differences but extension directions there are modified by plate interaction stresses the california shear zone has relatively low vertically averaged viscosity of about 1021 pascal seconds whereas the basin and range has a higher vertically averaged viscosity of 1022pascal seconds

oblique plate motion and continental tectonics three dimensional deformation is necessarily associated with oblique plate convergence and commonly results in partitioning of deformation between contractional and transcurrent components along plate margins kinematic models of strike slip partitioning for transpression and transtension allow the exact relation among three critical parameters plate motion instantaneous strain axes and degree of strike slip partitioning to be calculated application to two end member tectonic environments characterized by a low south island new zealand and high central california degree of strike slip partitioning demonstrates a remarkable consistency among the three parameters suggesting that strike slip partitioned transpression is a valid model for deformation in these regions the extreme degree of strike slip partitioning in wrench dominated systems such as central california is tentatively associated with a fundamental misorientation of finite and instantaneous strain axes

continent scale strike slip on a low angle fault beneath new zealand s southern alps implications for crustal thickening in oblique collision zones new zealand s southern alps lie adjacent to the continent scale dextral strike slip alpine fault on the boundary between the pacific and australian plates we show with a simple 2 d model of crustal balancing that the observed crustal root and erosion expressed as equivalent crustal shortening is up to twice that predicted by the orthogonal plate convergence since 11 ma and even since 23 ma when the alpine fault formed we consider two explanations for this involving a strong component of motion along the length of the plate boundary zone geophysical data indicate that the alpine fault has a listric geometry flattening at mid crustal levels and has accommodated sideways underthrusting of australian plate crust beneath pacific plate crust the geometry of the crustal root together with plate reconstructions requires the underthrust crust to be the hyperextended part of an asymmetric rift system which formed over 500 km farther south during the eocene the narrow remnant part today forms the western margin of the campbell plateau at 10 ma the hyperextended margin underwent shallow subduction in the puysegur subduction zone and then was dragged over 300 km along the length of the southern alps beneath a low angle 20 section of the alpine fault we speculate that prior to 10 ma more distributed lower crustal shortening and thickening occurred beneath the southern alps accommodating southward extrusion of continental crust in the northern part of the plate boundary zone providing a mechanism for clockwise rotation of the hikurangi margin

comparison of the meteorology and surface energy fluxes of debris free and debris covered glaciers in the southeastern tibetan plateau knowledge of debris free and debris covered glaciers is important for understanding the varying response of glaciers to climate change measurements at the debris free parlung no 4 glacier and the debris covered 24 k glacier in the southeastern tibetan plateau were carried out to compare the meteorology and surface energy fluxes and to understand the factors controlling the melting process the meteorological comparisons displayed temporally synchronous fluctuations in air temperature relative humidity and incoming longwave radiation l in but notable differences in precipitation incoming shortwave radiation s in and wind speed under the prevailing regional precipitation and debris conditions more l in 42 w m 2 was supplied from warmer and more humid air and more s in 58 w m 2 was absorbed at the 24 k glacier the relatively high energy supply led mainly to an increased energy output via turbulent heat fluxes and outgoing longwave radiation rather than glacier melting beneath the thick debris the sensitivity experiment showed that melt rates were sensitive to energy supply at debris thicknesses similar to 10 cm in contrast energy supply to the parlung no 4 glacier mainly resulted in snow ice melting the magnitude of which was significantly influenced by energy supplied by s in and the sensible heat flux

focal mechanisms and inter event times of low frequency earthquakes reveal quasi continuous deformation and triggered slow slip on the deep alpine fault abstract characterising the seismicity associated with slow deformation in the vicinity of the alpine fault may provide constraints on the stresses acting on a major transpressive margin prior to an anticipated great m8 earthquake here we use recently detected tremor and low frequency earthquakes lfes to examine how slow tectonic deformation is loading the alpine fault late in its typical 300 yr seismic cycle we analyse a continuous seismic dataset recorded between 2009 and 2016 using a network of 10 13 short period seismometers the southern alps microearthquake borehole array fourteen primary lfe templates are used in an iterative matched filter and stacking routine allowing the detection of similar signals corresponding to lfe families sharing common locations this yields an 8 yr catalogue containing 10 000 lfes that are combined for each of the 14 lfe families using phase weighted stacking to produce signals with the highest possible signal to noise ratios we show that lfes occur almost continuously during the 8 yr study period and highlight two types of lfe distributions 1 discrete behaviour with an inter event time exceeding 2 min 2 burst like behaviour with an inter event time below 2 min we interpret the discrete events as small scale frequent deformation on the deep extent of the alpine fault and lfe bursts corresponding in most cases to known episodes of tremor or large regional earthquakes as brief periods of increased slip activity indicative of slow slip we compute improved non linear earthquake locations using a 3 d velocity model lfes occur below the seismogenic zone at depths of 17 42 km on or near the hypothesised deep extent of the alpine fault the first estimates of lfe focal mechanisms associated with continental faulting in conjunction with recurrence intervals are consistent with quasi continuous shear faulting on the deep extent of the alpine fault

glaciological characteristics of the ablation zone of baltoro glacier karakoram pakistan baltoro glacier in the karakoram pakistan is one of the world s largest valley glaciers it drains an area of about 1500 km 2 and is 60km long in 2004 an italian german expedition carried out a glaciological field program on the ablation zone of the glacier focusing on the ablation conditions and the dynamic state of the glacier as baltoro glacier is a debris covered glacier ice ablation also depends on the debris properties stake measurements of ice ablation and debris cover in combination with meteorological data from automatic weather stations close by have been used to determine the local melt conditions results from these calculations have been combined with an analysis of different classes of surface cover and information about precipitation using remote sensing techniques in order to calculate mass fluxes for the upper part of baltoro glacier the dynamic state of the glacier has been investigated by gps based surface velocity measurements along the stake network a comparison of these short term measurements during the melt season with surface velocities computed from feature tracking of satellite images shows a high seasonal variability of the ice motion we have shown that this variability is up to 100 of the annual mean velocity on the basis of these investigations the mass fluxes at the concordia cross section have been quantified this approach can now be used together with the ablation calculations to reconstruct the variability of glacier extent and volume in the past using available climate data from the central karakoram from the comparison of historical measurements and photographs it is shown that the snout of baltoro glacier is oscillating back and forth a couple of hundred metres otherwise it seems not to react with the same magnitude as other glaciers to the climatic change elevation changes at concordia are a few tens of metres at the most

fluvial process and the establishment of bottomland trees the effects of river regulation on bottomland tree communities in western north america have generated substantial concern because of the important habitat and aesthetic values of these communities consideration of such effects in water management decisions has been hampered by the apparent variability of responses of bottomland tree communities to flow alteration when the relation between streamflow and tree establishment is placed in a geomorphic context however much of that variability is explained and prediction of changes in the tree community is improved the relation between streamflow and establishment of bottomland trees is conditioned by the dominant fluvial process or processes acting along a stream for successful establishment cottonwoods poplars and willows require bare moist surfaces protected from disturbance channel narrowing channel meandering and flood deposition promote different spatial and temporal patterns of establishment during channel narrowing the site requirements are met on portions of the bed abandoned by the stream and establishment is associated with a period of low flow lasting one to several years during channel meandering the requirements are met on point bars following moderate or higher peak flows following flood deposition the requirements are met on flood deposits high above the channel bed flood deposition can occur along most streams but where a channel is constrained by a narrow valley this process may be the only mechanism that can produce a bare moist surface high enough to be safe from future disturbance because of differences in local bedrock tributary influence or geologic history two nearby reaches of the same stream may be dominated by different fluvial processes and have different spatial and temporal patterns of trees we illustrate this phenomenon with examples from forests of plains cottonwood populus deltoides ssp monilifera along meandering and constrained reaches of the missouri river in montana

calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor

flow and deposition in and around a finite patch of vegetation this laboratory study describes the flow and deposition observed in and around a finite patch of vegetation located at the wall of a channel two patch densities are considered with 2 and 10 solid volume fraction the velocity field measured in and around the patch by acoustic doppler velocimetry revealed three distinct zones first there is a diverging flow region at the leading edge of the patch where the flow in line with the patch decelerates and the bulk of the flow is diverted toward the open channel second there is a fully developed region within the vegetation where the velocity is uniform across the patch width and along the length of the patch third a shear layer forms at the interface between the patch and adjacent open channel the pattern of deposition in and around the vegetation was characterized by releasing 12 micron spherical glass particles and recording net deposition on a set of glass slides in the diverging region net deposition increases in the stream wise direction as the local velocity decreases in the fully developed region of the patch deposition decreases with longitudinal position as the concentration in the water column is depleted the deposition pattern is nearly uniform across the patch width consistent with the velocity field and suggesting that turbulent diffusive flux across the lateral edge of the patch is not a significant source of particles to the patch under the conditions studied here

microstructures imply cataclasis and authigenic mineral formation control geomechanical properties of new zealand s alpine fault abstract the alpine fault is capable of generating large mw 8 earthquakes and is the main geohazard on south island nz and late in its 250 291 year seismic cycle to minimize its hazard potential it is indispensable to identify and understand the processes influencing the geomechanical behavior and strength evolution of the fault high resolution microstructural mineralogical and geochemical analyses of the alpine fault s core demonstrate wall rock fragmentation assisted by mineral dissolution and cementation resulting in the formation of a fine grained principal slip zone psz a complex network of anastomosing and mutually cross cutting calcite veins implies that faulting occurred during episodes of dilation slip and sealing fluid assisted dilatancy leads to a significant volume increase accommodated by vein formation in the fault core undeformed euhedral chlorite crystals and calcite veins that have cut footwall gravels demonstrate that these processes occurred very close to the earth s surface microstructural evidence indicates that cataclastic processes dominate the deformation and we suggest that powder lubrication and grain rolling particularly influenced by abundant nanoparticles play a key role in the fault core s velocity weakening behavior rather than frictional sliding this is further supported by the absence of smectite which is reasonable given recently measured geothermal gradients of more than 120 c km 1 and the impermeable nature of the psz which both limit the growth of this phase and restrict its stability to shallow depths our observations demonstrate that high temperature fluids can influence authigenic mineral formation and thus control the fault s geomechanical behavior and the cyclic evolution of its strength

microseismicity in southern south island new zealand implications for the mechanism of crustal deformation adjacent to a major continental transform shallow 25km diffuse crustal seismicity occurs in a zone up to 150km wide adjacent to the southern alpine fault new zealand as a consequence of distributed shear and thickening in the obliquely convergent australian pacific plate boundary zone it has recently been proposed that continental convergence here is accommodated by oblique slip on a low angle detachment that underlies the region and as such forms a previously unrecognized mode of oblique continental convergence we test this model using microseismicity presenting a new 15 month high resolution microearthquake catalog for the southern lakes and northern fiordland regions adjacent to the alpine fault we determine the spatial distribution moment release and style of microearthquakes and show seismicity in the continental lithosphere is predominantly shallower than 20km in a zone up to 150km wide but less frequent deeper microseismicity extending into the mantle at depths of up to 100km is also observed the geometry of the subducted oceanic australian plate is well imaged with a well defined benioff zone to depths of 150km in detail the depth of continental microseismicity shows considerable variation with no clear link with major active surface faults but rather represents diffuse cracking in response to the ambient stress release the moment release rate is 0 1 of that required to accommodate relative plate convergence and the azimuth of the principal horizontal axis of contraction accommodated by microseismicity is 120 15 20 clockwise of the horizontal axis of contractional strain rate observed geodetically thus short term microseismicity independent of knowledge of intermittent large magnitude earthquakes may not be a good guide to the rate and orientation of long term deformation but is an indicator of the instantaneous state of stress and potential distribution of finite deformation thus we show that both the horizontal and vertical spatial distribution of microseismicity can be explained in terms of a low angle detachment model

interactions between plant traits and sediment characteristics influencing species establishment and scale dependent feedbacks in salt marsh ecosystems abstract the importance of ecosystem engineering and biogeomorphic processes in shaping many aquatic and semi aquatic landscapes is increasingly acknowledged ecosystem engineering and biogeomorphic landscape formation involves two critical processes 1 species establishment and 2 scale dependent feedbacks meaning that organisms improve their living conditions on a local scale but at the same time worsen them at larger scales however the influence of organism traits in combination with physical factors e g hydrodynamics sediments on early establishment and successive development due to scale dependent feedbacks is still unclear as a model system this was tested for salt marsh pioneer plants by conducting flume experiments i on the influence of species specific traits such as stiffness of two contrasting dominant pioneer species spartina alterniflora and scirpus mariqueter to withstand current induced stress during establishment and ii to study the impact of species specific traits stiffness and physical forcing water level current stress on the large scale negative feedback at established tussocks induced scour at tussock edges of the two model species the results indicate that not only do species specific plant traits such as stiffness exert a major control on species establishment thresholds but also potentially physiologically triggered plant properties such as adapted root morphology due to sediment properties moreover the results show a clear relation between species specific plant traits abiotics i e sediment currents and the magnitude of the large scale negative scale dependent feedback these findings suggest that the ecosystem engineering ability resulting from physical plant properties can be disadvantageous for plant survival through promoted dislodgement stem stiffness increases the amount of drag experienced at the root system underlying the importance of scale dependent feedbacks on landscape development

a scale dependent model to represent changing aerodynamic roughness of ablating glacier ice based on repeat topographic surveys turbulent fluxes make a substantial and growing contribution to the energy balance of ice surfaces globally but are poorly constrained owing to challenges in estimating the aerodynamic roughness length z0 here we used structure from motion sfm photogrammetry and terrestrial laser scanning tls surveys to make plot scale 2 d and 3 d microtopographic estimations of z0 and upscale these to map z0 across an ablating mountain glacier at plot scales we found spatial variability in z0 estimates of over two orders of magnitude with unpredictable z0 trajectories even when classified into ice surface types tls derived surface roughness exhibited strong relationships with plot scale sfm z0 estimates at the glacier scale a consistent increase in z0 of 0 1 mm d 1 was observed space for time substitution based on time since surface ice was exposed by snow melt confirmed this gradual increase in z0 over 60 d these measurements permit us to propose a scale dependent temporal z0 evolution model where unpredictable variability at the plot scale gives way to more predictable changes of z0 at the glacier scale this model provides a critical step towards deriving spatially and temporally distributed representations of z0 that are currently lacking in the parameterisation of distributed glacier surface energy balance models less

reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors a review of complementary approaches abstract until recently one way relationships between flow dynamics geomorphology and plant ecology were considered dominantly when studying the functioning of river systems whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities however biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics in order to fully identify the processes linked to river dynamics changes in time and space of fluvial landforms and associated plant communities conceptual multidisciplinary progress is clearly needed to understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics this paper presents a detailed literature review of fluvial geomorphology riparian plant ecology and hydraulic engineering knowledge the historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics recent progress in ecology hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes based on this literature review a fluvial biogeomorphic succession concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi directional model the succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes the positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks islands or floodplains which are moderated by the biogeomorphic functional roles of ecosystem engineers that induce or reinforce the positive feedbacks this fluvial biogeomorphic succession concept relates the natural darwinian selection and ecological succession theories to fluvial geomorphology

a bayesian approach to estimating tectonic stress from seismological data summary earthquakes are conspicuous manifestations of tectonic stress but the non linear relationships between the stresses acting on a fault plane its frictional slip and the ensuing seismic radiation are such that a single earthquake by itself provides little information about the ambient state of stress moreover observational uncertainties and inherent ambiguities in the nodal planes of earthquake focal mechanisms preclude straightforward inferences about stress being drawn on the basis of individual focal mechanism observations however by assuming that each earthquake in a small volume of the crust represents a single uniform state of stress the combined constraints imposed on that stress by a suite of focal mechanism observations can be estimated here we outline a probabilistic bayesian technique for estimating tectonic stress directions from primary seismological observations the bayesian formulation combines a geologically motivated prior model of the state of stress with an observation model that implements the physical relationship between the stresses acting on a fault and the resultant seismological observation we show our bayesian formulation to be equivalent to a well known analytical solution for a single errorless focal mechanism observation the new approach has the distinct advantage however of including 1 multiple earthquakes 2 fault plane ambiguities 3 observational errors and 4 any prior knowledge of the stress field our approach while computationally demanding in some cases is intended to yield reliable tectonic stress estimates that can be confidently compared with other tectonic parameters such as seismic anisotropy and geodetic strain rate observations and used to investigate spatial and temporal variations in stress associated with major faults and coseismic stress perturbations

balancing the plate motion budget in the south island new zealand using gps geological and seismological data summary the landmass of new zealand exists as a consequence of transpressional collision between the australian and pacific plates providing an excellent opportunity to quantify the kinematics of deformation at this type of tectonic boundary we interpret gps geological and seismological data describing the active deformation in the south island new zealand by using an elastic rotating block approach that automatically balances the pacific australia relative plate motion budget the data in new zealand are fit to within uncertainty when inverted simultaneously for angular velocities of rotating tectonic blocks and the degree of coupling on faults bounding the blocks we find that most of the plate motion budget has been accounted for in previous geological studies although we suggest that the porter s pass amberley fault zone in north canterbury and a zone of faults in the foothills of the southern alps may have slip rates about twice that of the geological estimates up to 5 mm yr 1 of active deformation on faults distributed within the southern alps 100 km to the east of the alpine fault is possible the role of tectonic block rotations in partitioning plate boundary deformation is less pronounced in the south island compared to the north island vertical axis rotation rates of tectonic blocks in the south island are similar to that of the pacific plate suggesting that edge forces dominate the block kinematics there the southward migrating chatham rise exerts a major influence on the evolution of the new zealand plate boundary we discuss a model for the development of the marlborough fault system and hikurangi subduction zone in the context of this migration

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes