volume change reconstruction of swiss glaciers from length change data 1 a novel method to reconstruct glacier volume changes from a measured length record is presented and tested for 13 glaciers in the swiss alps the response of a glacier to changes in climate is modeled with a two parameter dynamical system in the variables length and volume driven by a history of equilibrium line altitude ela the model yields variations of glacier length and volume a dynamically equivalent simple model desm is determined for each glacier by matching modeled and measured length changes the volume changes predicted with the desm agree well with measurements for 12 glaciers whereas agreement is poor for one glacier with topographic breaks in the terminus area for all glaciers which are located in different climate regions the length and volume changes are reproduced with the same ela history this agreement shows that the macroscopic glacier response to the climate history is well correlated over a whole mountain range modeling the future evolution of the glaciers under a constant present day climate reveals that fast reacting glaciers are close to equilibrium whereas length and volume of the large valley glaciers would be reduced during the next century by an amount similar to the volume lost during the last 150 years

a note on induced stress changes in hydrocarbon and geothermal reservoirs abstract earthquakes have been induced by oil and gas production where pore pressures have decreased in some cases by several tens of mpa it has previously been suggested that such earthquakes are caused by poroelastic stressing of crust surrounding the reservoir induced earthquakes are also common in geothermal fields such as the geysers where strong correlations between both steam production and condensate injection and earthquake activity have been observed over the last several decades stress measurements within hydrocarbon reservoirs show that the least horizontal stress decreases with declining reservoir pressure as predicted by poroelasticity for circular disk shaped reservoirs isothermal reduction in pore pressure induces a relative horizontal tension within the reservoir production induced stressing may promote frictional sliding on pre existing faults within the reservoir itself normal faulting is promoted if the regional stress is extensional and the biot coefficient is sufficiently large 0 85 for reasonable coefficients of friction on the other hand dilatant fracturing and normal faulting are always promoted in extensional environments near the edge of the reservoir or in regions of high pore pressure gradient it is suggested that such fracturing could enhance fracture permeability in tight rocks adjacent to portions of the reservoir that experience large reductions in pore pressure due to production in regional compressional environments production modestly favors reverse faulting above and below the reservoir the ratio of thermal to poroelastic stress can be quite large in geothermal reservoirs such as the geysers reservoir wide energy balance considerations suggest that the average temperature has declined at the geysers by 6 c during the past 20 years reservoir average stress changes are thus on the order of 2 mpa and are certainly much larger near injection wells and steam producing fractures

geomechanical response to seasonal gas storage in depleted reservoirs a case study in the po river basin italy 1 underground gas storage ugs in depleted hydrocarbon reservoirs is a strategic practice to cope with the growing energy demand and occurs in many places in europe and north america in response to summer gas injection and winter gas withdrawal the reservoir expands and contracts essentially elastically as a major consequence of the fluid gas and water pore pressure fluctuations depending on a number of factors including the reservoir burial depth the difference between the largest and the smallest gas pore pressure and the geomechanical properties of the injected formation and the overburden the porous medium overlying the reservoir is subject to three dimensional deformation with the related cyclic motion of the land surface being both vertical and horizontal we present a methodology to evaluate the environmental impact of underground gas storage and sequestration from the geomechanical perspective particularly in relation to the ground surface displacements long term records of injected and removed gas volume and fluid pore pressure in the lombardia gas field northern italy are available together with multiyear detection of vertical and horizontal west east displacement of the land surface above the reservoir by an advanced permanent scatterer interferometric synthetic aperture radar psinsar analysis these data have been used to calibrate a 3 d fluid dynamic model and develop a 3 d transversally isotropic geomechanical model the latter has been successfully implemented and used to reproduce the vertical and horizontal cyclic displacements on the range of 8 10 mm and 6 8 mm respectively measured between 2003 and 2007 above the reservoir where a ugs program has been underway by stogit eni s p a since 1986 following a 5 year field production life because of the great economical interest to increase the working gas volume as much as possible the model addresses two ugs scenarios where the gas pore overpressure is pushed from the current 103 pi where pi is the gas pore pressure prior to the field development to 107 pi and 120 pi results of both scenarios show that there is a negligible impact on the ground surface with deformation gradients that remain well below the most restrictive admissible limits for the civil structures and infrastructures

application of a degree day model for the determination of contributions to glacier meltwater and runoff near keqicar baqi glacier southwestern tien shan a so called warm and wet transition of climate has occurred in the arid part of northwestern china since the late 1980s a result of this climatic transition is an increase in runoff in xinjiang and neighboring regions in a warming and wetting change of climate scenario we attempt to evaluate the impact of glacier meltwater and precipitation on the increase in outlet discharge runoff from keqicar baqi glacier southwestern tien shan china in our research we have applied a degree day model which is one of the most widely used methods of ice and snowmelt computations for a multitude of purposes such as hydrological modeling ice dynamic modeling and climate sensitivity studies it is concluded that under the warming and wetting scenario the primary supply for the runoff in this catchment is glacier meltwater with precipitation being the dominant secondary source 84 and 8 of total runoff respectively

the world stress map database release 2016 crustal stress pattern across scales abstract knowledge of the present day crustal in situ stress field is a key for the understanding of geodynamic processes such as global plate tectonics and earthquakes it is also essential for the management of geo reservoirs and underground storage sites for energy and waste since 1986 the world stress map wsm project has systematically compiled the orientation of maximum horizontal stress shmax for the 30th anniversary of the project the wsm database has been updated significantly with 42 870 data records which is double the amount of data in comparison to the database release in 2008 the update focuses on areas with previously sparse data coverage to resolve the stress pattern on different spatial scales in this paper we present details of the new wsm database release 2016 and an analysis of global and regional stress pattern with the higher data density we can now resolve stress pattern heterogeneities from plate wide to local scales in particular we show two examples of 40 60 shmax rotations within 70 km these rotations can be used as proxies to better understand the relative importance of plate boundary forces that control the long wave length pattern in comparison to regional and local controls of the crustal stress state in the new wsm project phase iv that started in 2017 we will continue to further refine the information on the shmax orientation and the stress regime however we will also focus on the compilation of stress magnitude data as this information is essential for the calibration of geomechanical numerical models this enables us to derive a 3 d continuous description of the stress tensor from point wise and incomplete stress tensor information provided with the wsm database such forward models are required for safety aspects of anthropogenic activities in the underground and for a better understanding of tectonic processes such as the earthquake cycle

reservoir conditions related to induced seismicity at the geysers steam reservoir northern california abstract seismicity at the geysers appears to be induced by steam production in which water boils to steam within a pervasively fractured reservoir subject to high levels of tectonic shear stresses and strains the steam reservoir is composed of fractured franciscan graywacke with a very heterogeneous multiple permeability and porosity distribution permeability is controlled by the larger fracture systems of the reservoir which act as a very permeable conduit to less permeable rock containing liquid water the reservoir fluid remains close to the liquidus conditions during production implying both a temperature and pressure decline in the rock matrix bounding the fracture systems as the reservoir is depleted reservoir earthquake focal mechanisms are nearly aligned with the regional tectonic strain field and reservoir earthquakes are indistinguishable from tectonic earthquakes elsewhere in the region within the reservoir the volume defined by the earthquakes has not changed within the resolution of the seismic network from 1975 to 1979 the log moment per earthquake also has not changed suggesting a steady state process of stress buildup and release added to the zero correlation of the fluid injection history with the earthquake activity the above observations suggest that elevated pore pressures and fluid injection are not likely causes for the geysers induced seismicity instead all available evidence points to the association of induced seismicity with pore pressure and temperature declines the two most likely mechanisms are either an increase in local shear stress levels with fissure deflation or a transition from stable to unstable sliding stick slip no other documented mechanism for induced seismicity are consistent with in situ reservoir conditions at the geysers

mechanism of induced seismicity at the geysers geothermal reservoir california the geysers reservoir is situated in a 60 80 km wide right lateral shear zone associated with the north american pacific plate boundary a small fraction of the shear may be occurring as permanent aseismic creep which is being converted to stick slip movement in the geysers reservoir due to steam production two mechanisms could be responsible for the induced seismicity a large 100 bars increase in effective rock pressure and an increase in the coefficient of friction the first mechanism requires that the initial state of the reservoir be predominantly liquid dominated the second mechanism is a consequence of dehydration of the reservoir causing both the hardening of clay and fault gouge and the precipitation of silica

near surface microearthquakes at the geysers geothermal field california a 150 m length 6 level three component vertical geophone array was cemented into the 67 to 219 m depth interval 220 to 720 ft of unocal s well gdcf 63 29 during a plug and abandonment operation on april 7 1998 casing deformation has been observed in wells of the study area including the gdcf 63 29 well an objective of the study was to determine if shallow deformation at the geysers is manifested seismically near surface microearthquake activity was monitored for a period of one year during the latter four months monitoring was supplemented with four surface stations to help constrain locations of shallow seismicity event locations occurring within about 750 m of the array bottom have been determined for the 10 week period january 6 to march 16 1999 these events are distinct from surface monitored seismicity at the geysers in that they occur predominantly above the producing reservoir at depths ranging from about 220 to 1000 m 600 to c180 m elevation the shallow events tend to be episodic with relatively quiescent periods of up to three weeks occurring between swarms event locations show a northeast striking trend similar to seismicity trends mapped deeper in the reservoir and parallel to the strike of a major surface lineaments observed over the productive field however clear fault or fracture planes are not resolved from the hypocenters composite fault plane solutions suggest oblique reverse faulting in the overburden the shallowest seismicity terminates near the base of a serpentine unit a contact which is the locus of most of the well casing deformations logged in the area suggesting that reservoir contraction is accommodated along numerous discrete faults below the serpentine but as continuous plastic deformation in the serpentine it is hypothesized that the resulting strain discontinuity at the base of the serpentine explains the prevalence of wellbore deformation there the shallow above reservoir microseismicity is strongly correlated in time with the injection and the deeper injection induced seismic activity occurring in the reservoir immediately below this suggests that deep injection induced events trigger shallower events by a remote triggering mechanism which has been observed at a larger scale at the geysers and elsewhere

estimation of glacier runoff and future trends in the yangtze river source region china glacier runoff from the yangtze river source region yrsr china is estimated for the period 1961 2000 using a degree day approach in the investigation area glacier runoff accounts for 11 0 of the total river runoff during the period 1961 2000 in the 1990s its contribution to river runoff rises to 17 0 due to the current rate of glacier decline the impact of glacier runoff on river runoff has recently increased in the source region based on two different climate change scenarios derived from echam5 mpi om future glacier runoff is assessed for the period 2001 50 in all climate change scenarios annual glacier runoff shows a significant increase due to intensified ice melting there is an increase in glacier runoff during spring and early summer yet a significant decrease in late summer this study highlights the current and future impact of glacier runoff on river runoff in the yrsr

glacier mass balance in the qinghai tibet plateau and its surroundings from the mid 1970s to 2000 based on hexagon kh 9 and srtm dems abstract in the context of global warming glacier changes in the qinghai tibet plateau qtp and its surroundings have attracted a great amount of public attention to date there have been many studies of glacier mass balance across the qtp however given that most of the previous studies have focused on a short observation period 2000 2015 and that long term mass change measurements are available only for some local regions we utilized declassified kh 9 images and 1 arc second shuttle radar topography mission srtm digital elevation models dems to provide the region wide mass balance from the mid 1970s to 2000 for a larger scale including 11 sample regions across the qtp and its surroundings the final results indicate that the glaciers in the northwest of the qtp have shown a less negative or near zero mass balance ranging from 0 11 0 13 m w e a 1 to 0 02 0 10 m w e a 1 compared to those in the southeast part with a mass balance range of 0 30 0 12 m w e a 1 to 0 11 0 14 m w e a 1 the most serious mass loss has emerged in the central eastern himalaya integrating our results with the observations after 2000 suggests that over the past four decades mid 1970s to the mid 2010s the glaciers in the himalaya nyainqentanglha and tanggula mountains as a whole have exhibited accelerated mass loss and the most significant acceleration has occurred in the eastern nyainqentanglha moreover the hindu raj glaciers have shown a stable rate of continuous mass loss while a nearly stable or slight mass gain state in the western kunlun region can be dated back to at least as far as the mid 1970s

changes in the glacier extent and surface elevation along the ningchan and shuiguan river source eastern qilian mountains china we investigate the changes at nine glaciers in the ningchan and shuiguan river source eastern qilian mountains between 1972 and 2010 according to analysis of topographic maps and multispectral satellite data all nine glaciers in the study area have retreated by a maximum of 250 57 4 m and a minimum of 91 57 4 m the total glacier area decreased by 1 20 km 2 corresponding to 9 9 of the glacierized area in 1972 comparing the two dems generated from the topographic maps and real time kinematic gps data the mean glacier thinning rate was 0 64 m yr 1 between 1972 and 2010 the most significant thinning generally occurred on the termini the ice volume loss was about 106 8 46 7 x 10 3 km 3 equal to 90 8 39 7 x 10 3 km 3 w e which suggested a mean water discharge of 0 1 0 05 m 3 s during 1972 2010 based on analysis of meteorological data the summer temperature june august tends to increase over a similar time period the consistency of temperature increase and glacier shrinkage allows us to suggest that air temperature plays an important role in glacier changes in this region c 2014 university of washington published by elsevier inc all rights reserved

contribution of alaskan glaciers to sea level rise derived from satellite imagery over the last 50 years retreating glaciers and ice caps gic contributed 0 5 mm yr to sea level rises slr and one third is believed to originate from ice masses bordering the gulf of alaska however these estimates of ice wastage in alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others how these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear here combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models dems we found that between 1962 and 2006 alaskan glaciers lost 41 9 8 6 km 3 yr water equivalent w e and contributed 0 12 0 02 mm yr to slr our ice loss is 34 lower than previous estimates reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work estimates of mass loss from gic in other mountain regions could be subject to similar revisions

sensitivity of net mass balance estimates to near surface temperature lapse rates when employing the degree day method to estimate glacier melt glacier mass balance models that employ the degree day method of melt modeling are most commonly driven by surface air temperatures that have been downscaled over the area of interest using digital elevation models and assuming a constant free air lapse rate that is often taken to be the moist adiabatic lapse rate malr 6 58 ck m 1 air temperature lapse rates measured over melting glacier surface are however consistently less steep than free air values and have been shown to vary systematically with lower tropospheric temperatures in this study the implications of including a variable near surface lapse rate in a 26 year 1980 2006 degree day model simulation of the surface mass balance of devon ice cap nunavut canada are examined and compared with estimates derived from surface air temperatures downscaled using a constant near surface lapse rate equal to the measured summer mean 4 98 ck m 1 and the malr our results show that degree day models are highly sensitive to the choice of lapse rate when compared with 23 years of surface mass balance measurements from the northwest sector of the ice cap model estimates are significantly better when surface air temperatures are downscaled using a modeled daily lapse rate rather than a constant lapse equal to either the summer mean or the malr

early 21st century glacier thickness changes in the central tien shan abstract although studies based on satellite gravimetry 2003 2010 and laser altimetry 2003 2009 measurements have achieved region wide glacier mass change for the tien shan the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately in this study we investigated region wide glacier thickness change in the central tien shan cts during 2000 2012 by differencing the shuttle radar topographic mission srtm digital elevation model dem with a newly constructed dem from 27 tandem x images for a total glacier area of 7239 8 527 2 km 2 an average glacier thickness change rate of 0 24 0 22 m a was derived this result agrees well with the result based on satellite laser altimetry measurements reported earlier 0 31 0 41 m a with temporal synchronization a fine spatial resolution and wide coverage our measurements are able to reveal abundant glacier change features and dependencies in the cts firstly the lower mountains have seen a more severe glacier decline and the glaciers facing the prevailing wind westerlies have experienced a greater decline because of the stronger evaporation furthermore those glaciers lying along the extremely high meridian mountain range have obviously gained mass in their upper reaches because the air current from the west is blocked and lifted by the meridian mountain range secondly for the entire glacier body the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish some huge glaciers covered by heavy debris have still experienced a severe decline however even though the heavy debris did not prevent the ablation its attenuating effects were considerable thirdly for the glaciers that surged before 2000 the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones some large glaciers surged again during 2000 2012 however with much lower magnitudes than in previous surges in general the surge glaciers have experienced a greater decline than the non surge glaciers fourthly due to the ice front calving and subglacial thermal erosion glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land terminated glaciers overall the glaciers in the cts are more stable than those in other parts of the tien shan however the glacier state there is still alarming a moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

heterogeneous mass loss of glaciers in the aksu tarim catchment central tien shan revealed by 1976 kh 9 hexagon and 2009 spot 5 stereo imagery the meltwater released by the glaciers in the aksu tarim catchment south of tomur peak central tien shan feeds the tarim river which is the main artery for the oases at the northern margin of the taklamakan desert the correct modeling of the contribution of the glaciers meltwater to the total runoff of the tarim river is hampered by the lack of mass balance data multi temporal digital terrain models dtms allow the determination of volume changes for large samples of glacier here we present the mass changes for 12 glaciers using 1976 kh 9 hexagon 2000 srtm3 and 2009 spot 5 datasets the results show that most of the glaciers have been losing mass since 1976 the largest glaciers koxkar and west qongterang lost 0 27 0 15 m w e a 1 and 0 43 0 15 m w e a 1 between 1976 and 2009 despite thick debris cover however some smaller glaciers show mass gain at their tongues indicating glacier surges using srtm3 data the volume gain of qinbingtan glacier no 74 could be dated to the time period 1999 2009 the overall mass budget of 0 33 0 15 m w e a 1 for 1976 2009 of the investigated glaciers is within the variability range of the global average however in the recent years 1999 2009 a slightly decelerated mass loss of 0 23 0 19 m w e a 1 could be observed c 2012 elsevier inc all rights reserved

ten years of seismic monitoring over a gas field abstract ten years of seismic recording allows us to locate more than 800 tremors with magnitudes ranging from 1 0 to 4 2 in a small 10 by 10 by 5 km volume near a major gas field lacq france the seismic activity began 10 yr after gas extraction began nearly all of the epicenters are located within the lateral extent of the gas field the only perturbation of the stress or strain fields which has the same spatial and temporal scale as the seismicity is the 500 bar drop in gas pressure due to 20 yr of gas exploitation demonstrating that these events are induced the network established to monitor this activity consists of eight telemetered stations including a well bottom geophone located at 3200 m depth using three dimensional relocation techniques we computed new hypocenter positions for more than 280 events these better located hypocenters form a diffuse zone that mimics the local dome structure taking the regional tectonic stresses into account we suggest that these ruptures may be the result of unfolding of the dome structure

extensional tectonics at the geysers geothermal area california comparisons between the yearly volume of steam withdrawn from the geysers california geothermal reservoir and the number of earthquakes indicate that most of the seismicity is induced to establish the inducing mechanism an estimate of the stress field orientation was calculated from inversion of 210 fault plane solutions below 1 km depth the geysers is undergoing uniaxial extension with the least principal stress 3 oriented near horizontal at approximately 105 azimuth the consistency between the local and regional stress fields indicates that the regional tectonic stress is much larger than the stresses induced locally through geothermal activities the stress data are equivocal as to whether earthquakes are induced due to conversion of aseismic to seismic slip or by increased shear stresses arising from reservoir contraction the observed tendency for downward growth of seismicity may arise from a preferential fracture orientation that is near vertical in conjunction with a stress state where the gradient of 1 exceeds that of 3 evidence of extension at the geysers and in the surrounding clear lake region indicates a direct relationship to the presence of the quaternary clear lake volcanics

loading rate impact on fracturing pattern lessons from hydrocarbon recovery lacq gas field france using scaling parameters of induced seismicity in size and space domains seismic b value and spatial correlation dimension d respectively we analyze the fracturing pattern of the gas reservoir of lacq in correlation with the production rate on the basis of previous observations and a previous model segall et al 1994 we assume that the cause of induced seismicity is a poroelastic stressing such that the production rate can be viewed as a stress rate for the rocks adjacent to the reservoir during the 20 year study period the production rate has decreased dramatically leading to a change of poroelastic stress rate from 4 5 10 3 to 1 5 10 3 mpa yr accordingly we observe a significant decrease in the size of activated fractures and a reduction of the spatial clustering of fracturing both arguing for a stress rate impact on the fracturing pattern in the gas field we interpret these changes in terms of a change in the deformation mode of stressed rocks from a more brittle to a more ductile behavior as the stress rate was decreased this hypothesis is supported by independent evidence from a number of experimental numerical and field studies the loading rate thus appears as a possible candidate to drive changes of b and d in time and space the apparent sensitivity of the earth s crust fracturing pattern to loading rate variations of much lower frequency than the tidal variations suggests that the earth s crust deformation mode itself be frequency dependent also our observations may have strong implications in contexts where the loading rate is induced by human intervention e g hydrocarbon recovery mines suggesting the possibility of adjusting the loading rate so as to shape the fracturing pattern locally according to human needs

sensitivity of mass balance of five swiss glaciers to temperature changes assessed by tuning a degree day model a degree day model is used to assess the sensitivity of the mass balance of five swiss glaciers to temperature changes the model uses temperature data extrapolated from nearby climate stations and is tuned by varying precipitation to make the model fit the observed distribution of mass balance with altitude once the model is tuned the effect of temperature change is simulated by recalculating the mass balance with the same parameters as before but with a temperature increase of 1 c throughout the year the largest mass balance changes involving increased ablation of 1 m w e a 1 c 1 occur at the snout with a progressively smaller increase with altitude the area averaged sensitivities for the five glaciers are 0 7 to 0 9 m w e a 1 c 1 if annual precipitation also increased by 20 it would partly offset the effect of the 1 c higher temperatures but could not compensate for it

rapid large area mapping of ice flow using landsat 8 abstract we report on the maturation of optical satellite image based ice velocity mapping over the ice sheets and large glacierized areas enabled by the high radiometric resolution and internal geometric accuracy of landsat 8 s operational land imager oli detailed large area single season mosaics and time series maps of ice flow were created using data spanning june 2013 to june 2015 the 12 bit radiometric quantization and 15 m pixel scale resolution of oli band 8 enable displacement tracking of subtle snow drift patterns on ice sheet surfaces at 1 m precision ice sheet and snowfield snow drift features persist for typically 16 to 64 days and up to 432 days depending primarily on snow accumulation rates this results in spatially continuous mapping of ice flow extending the mapping capability beyond crevassed areas our method uses image chip cross correlation and sub pixel peak fitting in matching landsat path row pairs high pass filtering is applied to the imagery to enhance local surface texture the current high image acquisition rates of landsat 8 725 scenes per day globally reduces the impact of high cloudiness in polar and mountain terrain and allows rapid compilation of large areas or dense temporal coverage of seasonal ice flow variations the results rival the coverage and accuracy of interferometric synthetic aperture radar insar mapping

reconstruction of the annual mass balance of chhota shigri glacier western himalaya india since 1969 this study presents a reconstruction of the mass balance mb of chhota shigri glacier western himalaya india and discusses the regional climatic drivers responsible for its evolution since 1969 the mb is reconstructed by a temperature index and an accumulation model using daily air temperature and precipitation records from the nearest meteorological station at bhuntar observatory the only adjusted parameter is the altitudinal precipitation gradient the model is calibrated against 10 years of annual altitudinal mb measurements between 2002 and 2012 and decadal cumulative mbs between 1988 and 2010 three periods were distinguished in the mb series periods i 1969 85 and iii 2001 12 show significant mass loss at mb rates of 0 36 0 36 and 0 57 0 36mw e a 1 respectively whereas period ii 1986 2000 exhibits steady state conditions with average mbs of 0 01 0 36mw e a 1 the comparison among these three periods suggests that winter precipitation and summer temperature are almost equally important drivers controlling the mb pattern of chhota shigri glacier at decadal scale the sensitivity of the modelled glacier wide mb to temperature is 0 52 m w e a 1 c 1 whereas the sensitivity to precipitation is calculated as 0 16mw e a 1 for a 10 change

poroelastic stressing and induced seismicity near the lacq gas field southwestern france o hundreds of shallow small to moderate earthquakes have occurred near the lacq deep gas field in southwestern france since 1969 these earthquakes are clearly separated from tectonic seismicity occurring in the pyrenees 25 km to the southwest the induced seismicity began when the reservoir pressure had declined by 30 mpa repeated levehng over the field shows localized subsidence reaching a maximum of 60 mm in 1989 segall 1989 suggested that poroelastic stressing associated with volumetric contraction of the reservoir rocks is responsible for induced seismicity associated with fluid extraction to test this model we compare the observed subsidence and hypocentral distributions with the predicted displacement and stress fields we find that the relationship between average reservoir pressure drop and subsidence is remarkably linear lending support to the linear poroelastic model displacements and stresses are computed based on a priori knowledge of the reservoir geometry materim properties and reservoir pressure changes the computed vertical displacements are found to be in excellent agreement with the subsidence observed from leveling stress perturbations accompanying gas extraction computed using the same parameters are found to be 0 2 mpa or less changes in coulomb failure stress are computed assuming that shp occurs on optimally oriented planes the predicted failure zones correlate very well with the spatial distribution of earthquakes if the perturbing stresses are small in comparison to the ambient regional deviatoric stresses and if the minimum regional compresslye stress axis is vertical accurate determination of focal mechanisms of the induced events would allow a more rigorous test of the poroelastic model and could lead to important inferences about the crustal stress state

changes in glacier volume on mt gongga southeastern tibetan plateau based on the analysis of multi temporal dems from 1966 to 2015 the accelerated retreat of glaciers and the reduction of glacier ice reserves caused by climate change can significantly affect regional water resources and hydrological cycles changes in glacier thickness are among the key indicators that reflect this process we analyzed changes observed in the elevation of glacier surfaces in the gongga mountains ggm using multi temporal digital elevation models dems derived from topographic maps srtm icesat and zy 3 data the results showed that the mean rate of change in glacier surface altitude in the ggm was 26 7 2 03 m 0 54 0 04 m a 1 between 1966 and 2015 the mean melt rates differed over different time periods latterly showing an accelerating trend as a general rule glaciers appear to be losing more volume at lower than at higher elevations further analysis of these results suggests that supraglacial debris coverage in the ggm promotes higher rates of mass loss

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

induced stresses due to fluid extraction from axisymmetric reservoirs earthquakes can be induced by fluid extraction as well as by fluid injection segall 1989 proposed that poroelastic stresses are responsible for inducing earthquakes associated with fluid extraction here i present methods for computing poroelastic stress changes due to fluid extraction for general axisymmetric reservoir geometries the results ofgeertsma 1973 for a thin disk reservoir with uniform pressure drop are recovered as a special case predicted surface subsidence agrees very well with measured leveling changes over the deep lacq gas field in southwestern france the induced stresses are finite if the reservoir pressure changes are continuous computed stress changes are on the order of several bars suggesting that the preexisting stress states in regions of extraction induced seismicity are very close to frictional instability prior to production

glacier mass variation and its effect on surface runoff in the beida river catchment during 1957 2013 using in situ measured data from qiyi glacier in combination with meteorological and runoff data from stations a distributed degree day model was developed for 631 investigated glaciers in the beida river catchment to explore glacier mass change and its effect on streamflow the results showed that the average mass balance was 272 67 mm w e a 1 with an ice loss of 3 99 gt during 1957 2013 assuming a continuous linear trend equilibrium line altitude rose by 242 m compared with morpho topographic variables climatic control is a more important factor affecting glacier change mass balance sensitivity to air temperature was 239 mm w e degrees c 1 a 1 while to precipitation it was 1 1 mm w e mm 1 a 1 that is a 210 mm increase in precipitation would be needed to compensate for the net mass loss induced by an air temperature increase of 1 degrees c average annual glacier meltwater runoff was 1 51 x 10 8 m 3 from 1957 to 2013 accounting for 15 2 of surface runoff the time series of meltwater runoff changed abruptly in 2000 and its contribution to surface runoff increased from 13 9 to 20 4

the evolution of seismic barriers and asperities caused by the depressuring of fault planes in oil and gas fields of south texas fluid pressures within some oil and gas fields of south texas have dropped to less than 20 per cent of their original values producing earthquakes with magnitudes up to 3 9 in recent years differential compaction of the depressurized region may be sufficient to result in the number and size of earthquakes generated or the faults may have been creeping prior to depressurization in either model the depressuring of fluids strengthens a fault and at first produces a barrier to slip as strain accumulates due to compaction or the continued aseismic slip of nearby portions of the fault stress builds up along the locked portions eventually forming high stress regions or asperities the asperities ultimately fail and earthquakes occur the process is repeated as long as the faults are active as the fluid pressures continue to decrease the barriers and subsequent asperities may increase in size and strength resulting in increasingly large and frequent earthquakes

glacier variations in response to climate change from 1972 to 2007 in the western lenglongling mountains northeastern tibetan plateau global warming is causing widespread glacier retreat with small glaciers disappearing we investigate changes in glaciers over the western lenglongling mountains located in the northeastern margin of the tibetan plateau glacier extent over the western lenglongling mountains is estimated by comparing digitized glacier outlines obtained from aerial photographs and satellite imagery these results suggest that all 179 glaciers in the western lenglongling mountains shrunk between 1972 and 2007 the total area loss was similar to 24 4 km 2 accounting for similar to 28 3 0 81 a 1 of the glacierized area in 1972 the average area retreat rates differ over different time intervals they are approximately 0 68 0 90 0 77 and 0 56 km 2 a 1 over the periods 1972 95 1995 99 1999 2002 and 2002 07 respectively based on analysis of meteorological data glacier shrinkage in the study area can probably be attributed to the increase in air temperature furthermore the smaller glaciers display a higher shrinkage rate than larger glaciers and glaciers on southwest facing slopes appear to retreat faster than those on northeast facing slopes

glacier change and glacier runoff variation in the tuotuo river basin the source region of yangtze river in western china glaciers in the tuotuo river basin western china have been monitored in recent decades by applying topographical maps and high resolution satellite images results indicate that most of glaciers in the tuotuo river basin have retreated in the period from 1968 1971 to 2001 2002 and their shrinkage area is 3 2 of the total area in the late 1960s to assess the influence of glacier runoff on river runoff a modified degree day model including potential clear sky direct solar radiation has been applied to the glaciated regions of the river basin over the period 1961 2004 it was found that glacier runoff has increased in the last 44 years especially in the 1990s when a two thirds increase in river runoff was derived from the increase in glacier runoff caused by loss of ice mass in the entire tuotuo river basin

the glaciers climate change initiative methods for creating glacier area elevation change and velocity products glaciers and their changes through time are increasingly obtained from a wide range of satellite sensors due to the often remote location of glaciers in inaccessible and high mountain terrain satellite observations frequently provide the only available measurements furthermore satellite data provide observations of glacier characteristics that are difficult to monitor using ground based measurements thus complementing the latter in the glaciers cci project of the european space agency esa three of these characteristics are investigated in detail glacier area elevation change and surface velocity we use a data from optical sensors to derive glacier outlines b digital elevation models from at least two points in time c repeat altimetry for determining elevation changes and d data from repeat optical and microwave sensors for calculating surface velocity for the latter the two sensor types provide complementary information in terms of spatio temporal coverage while c and d can be generated mostly automatically a and b require the intervention of an analyst largely based on the results of various round robin experiments multi analyst benchmark studies for each of the products we suggest and describe the most suitable algorithms for product creation and provide recommendations concerning their practical implementation and the required post processing for some of the products area velocity post processing can influence product quality more than the main processing algorithm

chronostratigraphic correlation of lacustrine deposits using 87sr 86sr ratios eocene green river formation wyoming u s a abstract the reconstruction of detailed basin scale depositional histories from sedimentary rocks fundamentally depends on the availability of reliable time markers unlike marine strata lacustrine strata typically lack rapidly evolving cosmopolitan fauna or flora that might serve this purpose depending on their geologic context lacustrine strata may also lack tephras that could provide isochronous markers or radioisotopic age variations in 87 sr 86 sr ratios could potentially provide an alternative means of chronostratigraphic correlation for carbonate rich lake deposits based on the hypothesis that sr isotopes are well mixed in a lake and do not experience significant fractionation to test this hypothesis we measured 87 sr 86 sr ratios in 114 samples from two drill cores of the upper wilkins peak member from the green river formation that are located 23 km apart these cores can be independently correlated using distinctive tephras and organic carbon rich mudstone horizons measured 87 sr 86 sr ratios range from 0 71154 to 0 71504 and vary inversely with lake water depth as interpreted by sedimentary lithofacies characteristics lower ratios of 87 sr 86 sr are found in lithofacies deposited during lake highstands which are marked by laminated dark gray mudstone and elevated organic carbon enrichment as measured by fischer assay analysis higher 87 sr 86 sr ratios occur in lithofacies deposited during lake lowstands which are marked by organic lean gray green mudstone 87 sr 86 sr in approximately time equivalent samples from the two cores show a strong positive correlation r 0 68 despite the likely presence of small temporal mismatches between approximately correlative samples we conclude that lake water was consistently well mixed with respect to sr across distances of at least 23 km these results suggest that 87 sr 86 sr can serve as a powerful tool to aid high resolution chronostratigraphic correlation of lake deposits

modelling 60 years of glacier mass balance and runoff for chhota shigri glacier western himalaya northern india glacier mass balance and runoff are simulated from 1955 to 2014 for the catchment 46 glacier cover containing chhota shigri glacier western himalaya using gridded data from three regional climate models 1 the rossby centre regional atmospheric climate model v 4 rca4 2 the regional atmosphere model remo and 3 the weather research and forecasting model wrf the input data are downscaled to the simulation grid 300 m and calibrated with point measurements of temperature and precipitation additional input is daily potential global radiation calculated using a dem at a resolution of 30 m the mass balance model calculates daily snow accumulation melt and runoff the model parameters are calibrated with available mass balance measurements and results are validated with geodetic measurements other mass balance model results and run off measurements simulated annual mass balances slightly decreased from 0 3 m w e a 1 1955 99 to 0 6 m w e a 1 for 2000 14 for the same periods mean runoff increased from 2 0 m 3 s 1 1955 99 to 2 4 m 3 s 1 2000 14 with glacier melt contributing about one third to the runoff monthly runoff increases are greatest in july due to both increased snow and glacier melt whereas slightly decreased snowmelt in august and september was more than compensated by increased glacier melt

climate sensitivity of a high precipitation glacier in new zealand the sensitivity of glaciers to climatic change is key information in assessing the response and sea level implications of projected future warming new zealand glaciers are important globally as an example of how maritime glaciers will contribute to sea level rise a spatially distributed energy balance model is applied to brewster glacier new zealand in order to calculate glacier mass balance run off and sensitivity to climate change the model successfully simulates four annual mass balance cycles close to half 52 of the energy available for melt on the glacier is supplied by turbulent heat fluxes with radiation less important except during the winter model sensitivity to temperature change is one of the largest reported on earth at 2 0 m w e a 1 8c 1 in contrast a 50 change in precipitation is required to offset the mass balance change resulting from a 18c temperature change meltwater run off sensitivity is also very high increasing 60 with a 18c warming the extreme sensitivity of mass balance to temperature change suggests that significant ice loss will occur with even moderate climate warming

hydraulic stimulation of natural fractures as revealed by induced microearthquakes carthage cotton valley gas field east texas we produced a high resolution microseismic image of a hydraulic fracture stimulation in the carthage cotton valley gas field of east texas we improved the precision of microseismic event locations four fold over initial locations by manually repicking the traveltimes in a spatial sequence allowing us to visually correlate waveforms of adjacent sources the new locations show vertical containment within individual targeted sands suggesting little or no hydraulic communication between the discrete perforation intervals simultaneously treated within an 80 m section treatment i e fracture zone lengths inferred from event locations are about 200 m greater at the shallow perforation intervals than at the deeper intervals the highest quality locations indicate fracture zone widths as narrow as 6 m similarity of adjacent source waveforms along with systematic changes of phase amplitude ratios and polarities indicate fairly uniform source mechanisms fracture plane orientation and sense of slip over

the second chinese glacier inventory data methods and results the second chinese glacier inventory was compiled based on 218 landsat tm etm scenes acquired mainly during 2006 10 the widely used band ratio segmentation method was applied as the first step in delineating glacier outlines and then intensive manual improvements were performed the shuttle radar topography mission digital elevation model was used to derive altitudinal attributes of glaciers the boundaries of some glaciers measured by real time kinematic differential gps or digitized from high resolution images were used as references to validate the accuracy of the methods used to delineate glaciers which resulted in positioning errors of 10 m for manually improved clean ice outlines and 30 m for manually digitized outlines of debris covered parts the glacier area error of the compiled inventory evaluated using these two positioning accuracies was 3 2 the compiled parts of the new inventory have a total area of 43 087 km 2 in which 1723 glaciers were covered by debris with a total debris covered area of 1494 km 2 the area of uncompiled glaciers from the digitized first chinese glacier inventory is similar to 8753 km 2 mainly distributed in the southeastern tibetan plateau where no images of acceptable quality for glacier outline delineation can be found during 2006 10

earthquakes near rocky mountain house alberta and their relationship to gas production facilities a 1980 field survey of earthquake activity near rocky mountain house alberta using one digital and six conventional seismographs recorded 146 microearthquakes m 3 4 in 23 days and located 67 of them the located events and probably the unlocated events as well all occurred in a small zone approximately 4 km north south by 4 km east west by 1 km thick centred near 52 12 5 n 115 15 w at a depth of 4 0 km with an uncertainty of 2 km on each of the location coordinates the activity occurred below and or in the strachan d 3a sour gas reservoir which is a devonian aged limestone reef complex in a section of nearly flat lying unfaulted sediments the earthquakes had a composite thrust faulting mechanism with generally north trending intermediate dipping planes in the presence of a regional deviatoric stress field that was horizontally compressive and oriented approximately east west the earthquake activity may be related to the extraction of the natural gas and related fluids from the reservo

changes in glacier mass in the lenglongling mountains from 1972 to 2016 based on remote sensing data and modeling abstract glacial meltwater fed streamflow from the qilian mountains provides a much needed source of water for the northeastern margins of the tibetan plateau tp and surrounding regions we analyzed changes in glaciers located in the lenglongling mountains llm in the eastern qilian mountains in terms of glacier area and surface elevation these analyses were accomplished using multi temporal satellite images and studying digital elevation models dems based on topographic maps and zy 3 data the results showed that from 1972 to 2016 glacier coverage decreased by 41 1 km2 leaving only 62 1 km2 extant in 2016 the mean rate of change in glacier surface elevation asl was 18 7 1 2 m 0 43 0 03 m a 1 over the same period in situ measured data from ningchan no 1 glacier nc01 combined with meteorological records were also employed to develop a spatially distributed degree day model for the llm glaciers these two approaches yielded similar results allowing the reconstruction of a consistent time series that detailed annual changes in glacier mass over the past 44 years in addition we calculated that the mean annual glacial meltwater fed streamflow from 1972 to 2013 in the jiutiaoling basin jtlb northeast of the llm was equivalent to 1 4 107 m3 or 4 6 of the area s total annual streamflow it is remarkable that in years when streamflow was relatively lower such as 1972 1991 and 2013 glacial meltwater accounted for a higher proportion more than 8 of the streamflow

influence of poroelastic behavior on the magnitude of minimum horizontal stress sh in overpressured parts of sedimentary basins in many sedimentary basins of the world the minimum hori zontal stress s h is greater in overpressured zones than in normally pressured zones at equivalent depths a common explanation is that the frictional slip on listric normal faults keeps the difference between vertical stress s v and s h within certain bounds and the difference is smaller under lower effective stress i e higher pore pressure p p however in the overpressured parts of the central north sea graben united kingdom and the sable subbasin of the scotian shelf canada conventional friction envelopes underestimate the magnitude of s h these data instead indicate that s h increases at a rate proportional to but less than the rate of increase of p p a condition consistent with a p p induced deformation of the rock called poroelastic behavior this paper argues that whereas friction may govern s h in normally pressured basins poroelastic behavior is responsible for the unusually high s h in the overpres sured parts of these same basins data on the p p and s h gradients from these basins suggest that s h p p 0 7

glacier changes on the tibetan plateau derived from landsat imagery mid 1970s 2000 13 glacier area changes on the tibetan plateau were studied in different drainage basins based on landsat satellite images from three epochs 263 in the mid 1970s 150 in 1999 2002 and 148 in 2013 14 three mosaics m1976 m2001 and m2013 with minimal cloud and snow cover were constructed and the uncertainty due to each epoch having a finite span was accounted for glacier outlines tpg1976 tpg2001 and tpg2013 were digitized manually with guidance from the srtm dem v4 1 and google earth imagery to achieve complete multi temporal coverage in a reasonable time only debris free ice was delineated area mapping uncertainty was evaluated at three study sites mount qomolangma everest mount naimona nyi mount geladandong where the largest differences between present and earlier measurements were within similar to 4 area differences with previous inventories ranged from 19 6 tpg1976 minus the first chinese glacier inventory to 3 6 and 1 1 tpg2013 and tpg2001 respectively minus the second chinese glacier inventory while the difference tpg2001 minus the gamdam glacier inventory was 10 4 glacier area on the plateau decreased from 44 366 2827 km 2 1 7 of the study area in the 1970s to 42 210 1621 km2 in 2001 and 41 137 1616 km2 in 2013 shrinkage was faster in external drainage basins of the southeast than in the interior basins of the northwest from a maximum of 0 43 a 1 1 60 a 1 during 19942013 in the mekong catchment down to a minimum of 0 12 a 1 in the tarim interior drainage

reservoir characterization using oil production induced microseismicity clinton county kentucky abstract microseismic monitoring tests were conducted from 1993 to 1995 in the seventy six oil field clinton county kentucky oil is produced from low porosity fractured carbonate rocks at 3 no injection operations were conducted gross changes in production rate correlate with event rate event rate lags changes in production rate by 2 to 3 weeks hypocenters and first motion data have revealed previously undetected low angle thrust faults above and below the currently drained depth intervals production history well logs and drill tests indicate that the seismically active faults or fractures are previously drained intervals that have subsequently recovered to hydrostatic pressure via brine invasion storage capacity computed for one of these drained fractures implies that total oil production represents about 20 of total pore volume correlation of older production intervals and well log porosity anomalies with the seismically active faults indicate that the oil reservoir in the study area is primarily a set of compartmentalized low angle thrust faults although low angle fracture sets have not previously been considered in the exploration and development of the area the mapped thrust faults are consistent with other investigators interpretations of oil associated with secondary fracture sets occurring along deeper seated wrench fault structures stress determined from composite focal mechanisms indicates a near surface

glacier mass changes in rongbuk catchment on mt qomolangma from 1974 to 2006 based on topographic maps and alos prism data abstract elevation changes of glacier surfaces were investigated in rongbuk catchment rc on the northern slopes of mt qomolangma in the central himalayas by comparing a digital elevation model dem generated from the 2006 alos prism imageries with the base dem1974 derived from the 1 50 000 topographic maps the average elevation change rate of glacier surfaces in rc was estimated at 0 47 0 23 m a 1 between 1974 and 2006 such surface lowering rates varied significantly with glaciers and altitudes one of the notable results is that the debris covered ice thinned much more rapidly than the exposed ice at higher altitudes overall glaciers in rc have lost mass of 0 06 0 04 gt a 1 during 1974 2006 glacier imbalance constitutes about 50 or more of the rongbuk runoff

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