tracking holocene glacial and high altitude alpine environments fluctuations from minerogenic and organic markers in proglacial lake sediments lake blanc huez western french alps holocene palaeoenvironmental evolution and glacial fluctuations at high altitude in the western french alps are reconstructed based on a multiproxy approach within lake blanc huez 2550 m a s l drainage basin the combination of seismic profiling 3 5 khz piston coring and radiocarbon dating in proglacial lacustrine sediments together with a detailed organic analysis of autochthonous and allochthonous supply allows documenting the evolution of glacier activity during the holocene over the last 9700 years the holocene lake record has a bimodal pattern whose transition is progressive and occurring between 5400 and 4700 cal bp during the early holocene the organic lacustrine facies reflects reduced glacial activity in the catchment this major glacial retreat seems to result from solar forcing and high summer insolation after 5400 cal bp lacustrine sedimentation is marked by the gradual increase both of minerogenic supply and soil erosion suggesting a progressive transition to wetter climatic conditions this climate change is synchronous both from the gradual decrease of summer insolation and the gradual reorganization of oceanic and atmospheric circulations characterizing the beginning of the neoglacial period both colder temperature and humid climate induced significant glacier advance since 4700 cal bp over this global trend three periods are particularly associated with higher runoff processes and higher soil erosion interpreted as wetter time intervals resulting from enhanced northern westerlies regimes across the north atlantic and western europe they are dated from 8700 to 7000 4700 to 2500 and 1200 to 200 cal bp these wetter phases drastically contrast with periods of reduced glacial activities dated from the early bronze age ca 3870 3770 cal bp the iron age ca 2220 2150 cal bp the roman period ca ad115 330 and the medieval warm period ca ad760 1160 in addition these dryer periods are associated with mining activities at high altitude

reconstructing recent environmental changes from proglacial lake sediments in the western alps lake blanc huez 2543 m a s l grandes rousses massif france abstract the evolution of high altitude glaciers and human activities in the grandes rousses massif is documented by high resolution seismic reflection profiling and multiproxy analysis of short sediment cores in proglacial lake blanc huez these lacustrine data are compared with historical chronicles geomorphological features and glaciological studies in this region of the western alps and they allow the documentation of recent environmental changes the specific geometry of high amplitude reflections in the uppermost seismic unit the lithology of short cores and the available limnological data in the lake suggest that clastic particles eroded by the glaciers and transported in suspension by glacial melt waters in early summer essentially develop homopycnal flood events in the lake a conceptual model linking fluctuations of glacier equilibrium line altitudes in the catchment area with sedimentary facies retrieved in the lake basin is proposed this approach allows reconstructing continuous glacier fluctuations since ad1820 1850 and suggests several phases of glacier fluctuations during the little ice age lia these reconstructions are based on changes in lacustrine sediment laminations density magnetic susceptibility reflectance spectra organic matter and arsenic content the age depth model of short sediment cores is provided by 210 pb 137 cs and 241 am radionuclide dating this chronology is further supported by identifying in lacustrine sediments the impact of i the nearby m 5 3 correncon earthquake in ad 1962 ii the development of the ski resort at high altitude close to the lake and iii the last advance of glaciers during the lia in ad1820 1850 and the following phase of glacier retreat observed in the alpine region at the end of the lia in ad 1880 frequent sandy layers enriched in organic matter and associated with fluctuations in the arsenic concentrations may result from hydraulic remobilisation of middle age mine tailings at the lake shore by snow melt or heavy rain fall events during the lia

instruments and methods glaciological and volumetric mass balance measurements error analysis over 51 years for glacier de sarennes french alps the mass balance of glacier de sarennes french alps has been measured since 1949 using the glaciological method based on core and ablation stake data and area extrapolations to find the overall glacier balance the cumulative balance obtained in this way is very dependent on systematic errors that can increase linearly with the number n of measurement years whereas random errors rise with the volumetric balance method based on aerial photogrammetry provides results whose errors do not depend on the number of years this method was used to test field measurements for the period 1952 2003 and gives a mass balance of 32 30 1 04 m w e compared to 34 89 1 15 m w e based on field data the discrepancy between the two methods is discussed on the basis of a careful error analysis moreover the possibility of using the volumetric method to detect biases in field measurements is evaluated in terms of two types of errors the number and locations of measurement sites required to account for all the spatial and temporal variabilities of the mass balance is discussed by variance analysis methodological implications and recommendations are presented to provide mass balance measurements of the best possible accuracy

positive degree day factors for ablation on the greenland ice sheet studied by energy balance modelling ice ablation is related to air temperature by the positive degree day factor variations of the positive degree day factor in west greenland are studied using an energy balance model to simulate ablation under different conditions degree day factors for simulated and measured ice ablation at nordbogletscher and qaman rssup sermia agree well with values around 8 mm d 1 c 1 degree day factors for snow are less than half those for ice energy balance modelling shows that degree day factors vary with summer mean temperature surface albedo and turbulence but there is only evidence of large positive degree day factors at lower temperatures and with low albedo 0 3 the greatest effect of albedo variations 0 3 0 7 is at lower temperatures while variations in turbulence have greater effect at higher temperatures current models may underestimate runoff from the greenland ice sheet by several tenths because they use a degree day factor for melting ice that is too small for the colder parts of the ice sheet i e the upper ablation area and the northerly margin

structure and seismogenic properties of the mentawai segment of the sumatra subduction zone revealed by local earthquake traveltime tomography 1 on 12 september 2007 an mw8 4 earthquake occurred within the southern section of the mentawai segment of the sumatra subduction zone where the subduction thrust had previously ruptured in 1833 and 1797 traveltime data obtained from a temporary local seismic network deployed between december 2007 and october 2008 to record the aftershocks of the 2007 event was used to determine two dimensional 2 d and three dimensional 3 d velocity models of the mentawai segment the seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin the downgoing slab is clearly distinguished by a dipping region of highvp 8 0 km s which can be a traced to 50 km depth with an increased vp vs ratio 1 75 to 1 90 beneath the islands and the western side of the forearc basin suggesting hydrated oceanic crust above the slab a shallow continental moho of less than 30 km depth can be inferred suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge the outer arc islands are characterized by low vp 4 5 5 8 km s and high vp vs greater than 2 0 suggesting that they consist of fluid saturated sediments the very low rigidity of the outer forearc contributed to the slow rupture of the mw 7 7 mentawai tsunami earthquake on 25 october 2010

using upper air conditions to estimate south cascade glacier washington u s a summer balance asimplemodelusesonce dailymeteorologicalvaluesintheu s national centers for environmental predictionand u s national center foratmospheric research ncep ncar re analysis databaseto estimate summerbalanceof south cascade glacier washington u s a each year over1959 99 the rms error 0 30mw e r 2 0 71 is com parable to measurement error the model relates summer balance linearly to temperature t 0 c at 2000m and to snow flux at1650m the altitudes in recent years of the equilib rium line and terminus the snow flux is the product of the humidity and westerly wind component at 850hpa when temperature t 2 c at 1650m temperatures are inter polated linearly betweenthe 850 and 700hpa levels boththe positive 2000mtemperature andthe snow flux are summedfrom 26 aprilto 4 october whenthe summerestimatesare combinedwiththosefromawinterbalancemodelusingthesamedatabase thermserrorin estimating netbalance is 0 40m r 2 0 81 the indicated sensitivities of balance to warm ing of 1 c are 0 51m for summerand 0 24m for winter onthe assumptionthatthetotal 0 75m c 1 sensitivityexists atall altitudes awarmingof only 0 7 c wouldbe sufficientto overcome the1986 98 averagenetbalance 0 5matthe top of theglacier

offshore geodetic data conducive to the estimation of the afterslip distribution following the 2003 tokachi oki earthquake a cable based seafloor observatory located offshore of hokkaido japan provides the world s first direct observation of offshore post seismic displacement after removing thermal noise this data is used to constrain the distribution of offshore afterslip from a great interplate earthquake mw 8 0 that occurred during 2003 along the southern kuril trench a checkerboard resolution test showed a great contribution of the offshore data to improving the spatial resolution on the plate interface slip near the trench the 1 yr afterslip is distributed in a u shaped pattern encircling its co seismic slip area this result indicates that the stick slip frictional properties of the plate interface are distributed in a patch like pattern as opposed to a banding pattern as previously assumed in young subduction zones

cyclostratigraphy and eccentricity tuning of the early oligocene through early miocene 30 1 17 1 ma cibicides mundulus stable oxygen and carbon isotope records from walvis ridge site 1264 few astronomically calibrated high resolution 5 kyr climate records exist that span the oligocene miocene time interval notably available proxy records show responses varying in amplitude at frequencies related to astronomical forcing and the main pacemakers of global change on astronomical time scales remain debated here we present newly generated x ray fluorescence core scanning and benthic foraminiferal stable oxygen and carbon isotope records from ocean drilling program site 1264 walvis ridge southeastern atlantic ocean complemented by data from nearby site 1265 the site 1264 benthic stable isotope records span a continuous 13 myr interval of the oligo miocene 30 1 17 1 ma at high resolution 3 0 kyr spectral analyses in the stratigraphic depth domain indicate that the largest amplitude variability of all proxy records is associated with periods of 3 4 m 3 4 m and 0 9 m 0 9 m which correspond to 405 and 110 kyr eccentricity using a magnetobiostratigraphic age model maxima in caco3 content 18o and 13c are interpreted to coincide with 110 kyr eccentricity minima the strong expression of these cycles in combination with the weakness of the precession and obliquity related signals allow construction of an astronomical age model that is solely based on tuning the caco3 content to the nominal la2011 ecc3l eccentricity solution very long period eccentricity maxima 2 4 myr are marked by recurrent episodes of high amplitude 110 kyr 18o cycles at walvis ridge indicating greater sensitivity of the climate cryosphere system to short eccentricity modulation of climatic precession in contrast the responses of the global high latitude climate system cryosphere and carbon cycle to the 405 kyr cycle as expressed in benthic 18o and especially 13c signals are more pronounced during 2 4 myr minima the relationship between the recurrent episodes of high amplitude 110 kyr 18o cycles and the 1 2 myr amplitude modulation of obliquity is not consistent through the oligo miocene identification of these recurrent episodes at walvis ridge and their pacing by the 2 4 myr eccentricity cycle revises the current understanding of the main climate events of the oligo miocene

meteorological controls on glacier mass balance empirical relations suggested by measurements on glacier de sarennes france glacial mass balance reconstruction for a long term time scale requires knowledge of the relation between climate change and mass balance fluctuations a large number of mass balance reconstructions since the beginning of the century are based on statistical relations between monthly meteorological data and mass balance the question examined in this paper is are these relationships reliable enough for long term time scale extrapolation from the glacier de sarennes long mass balance observations series we were surprised to discover large discrepancies between relations resulting from different time periods the importance of the albedo in relation to ablation and mass balance is highlighted and it is shown that it is impossible to ignore glacier surface conditions in establishing the empirical relation between mass balance fluctuations and climatic variation to omit this parameter leads to incorrect results for mass balance reconstruction in the past based on meteorological data

silver and lead in high altitude lake sediments proxies for climate changes and human activities abstract high altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long term changes that have occurred in their catchment area here trace element concentrations and pb isotopes are presented for two sedimentary cores from lake blanc huez in the french alps to trace the impact of climate changes and human activities over the holocene lead and ag contents are very high and clearly dominated by input from a pb ag vein located a few meters from the lakeshore a vein that also buffers the pb isotopes mining of this vein in medieval times is recorded in the corresponding lake sediments with high ag content coupled with high pb u ratio these chemical characteristics can be used to constrain the major holocene climate changes significant advances of glaciers next to the lake produced sediments with ag and pb concentration peaks and high pb u ratios due to accelerated erosion of the pb ag vein similar to the effects of the medieval mining in contrast reduced glacier activity led to the formation of organic rich sediments with high u and as contents and low pb u ratios more generally the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time

high altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the western french alps lake bramant grandes rousses massif abstract two twin short gravity cores and a long piston core recovered from the deepest part of proglacial lake bramant grandes rousses massif french alps under and overlying a large slump identified by high resolution seismic profile allow the investigation of holocene natural hazards and interactions between human activity and climatic changes at high altitude annual sedimentation throughout the cores glacial varves is identified on photographs itrax high resolution continuous microfluorescence x and cat scan computerized axial tomography analyses and is supported by 1 the number of dark and light laminations between dates obtained by radionuclide measurements 137cs 241am 2 the correlation of a slump triggered by the nearby ad 1881 allemond earthquake msk intensity vii and of a turbidite triggered by the ad 1822 chautagne regional earthquake msk intensity viii 3 the number of laminations between two accelerator mass spectrometry ams 14c dates and 4 archaeological data in lake bramant dark layers are coarser contain less detrital elements but more neoformed elements and organic matter content these darker laminations result from calm background sedimentation whereas the lighter layers are finer and rich in detrital elements and reflect the summer snowmelt traces of mining activity during the roman civilization apogee ad 115 330 and during the early bronze age 3770 3870 cal bp are recorded by lead and copper content in the sediments and probably result from regional and local mining activity in the nw alps warmer climate during the bronze age in this part of the alps is suggested by 1 two organic deposits 4160 3600 cal bp and 3300 2850 cal bp likely reflecting a lower lake level and smaller glaciers and 2 evidence of a different vegetation cover around 2500 m a s l the onset of clastic proglacial sedimentation between 3600 3300 cal bp and since 2850 cal bp is synchronous with periods of glacier advances documented in the alps and high lake levels in west central europe this major change in proglacial sedimentation highlights the development of a larger st sorlin glacier in the catchment area of lake bramant

a century reconstruction of the mass balance of glacier de sarennes french alps the 50 year time series of mass balance on glacier de sarennes is one of the longest in the french alps and so is often used as a reference for glacier variations in the french alps meteorological data can be used to extend the series backwards in time martin 1978 proposed such a reconstruction for the 1882 1977 period with 50 years of observations we show that the classical method used by martin is too dependent on the calibration period we therefore try to improve the accuracy of this reconstruction using the vincent and vallon 1997 method which takes into account the albedo change of the surface during the ablation period this is called the daily method this new method appears to be stable in time once calibrated the daily method is applied to reconstruct the 1881 1949 period the new reconstruction is compared to a volumetric balance between two maps from 1906 and 1981 it appears that both reconstructions classical and daily fail to render the trend correctly over a long period of time the cumulative centred mass balance correlates well r 2 0 62 with the hydrological mass balance series of aletschgletscher switzerland

postseismic deformation of the andaman islands following the 26 december 2004 great sumatra andaman earthquake 1 two years after the great sumatra andaman earthquake the 3 1 m wsw coseismic displacement at port blair andaman islands had increased by 32 cm postseismic uplift initially exceeded 1 cm per week and decreased to 1 mm week by 2007 points near port blair had risen more than 20 cm a 24 reversal of coseismic subsidence uplift at eight gps sites suggests a gradual eastward shift of the coseismic neutral axis separating subsidence from uplift simulations of the gps postseismic displacements as viscoelastic relaxation of coseismic stress change and as slip on the plate interface indicate that slip down dip of the seismic rupture dominates near field deformation during the first two years postseismic slip beneath the andaman islands released moment equivalent to a magnitude mw 7 5 earthquake and the distribution suggests deep slip in the stable frictional regime accelerated to catch up to the coseismic rupture

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

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

space time distribution of afterslip following the 2003 tokachi oki earthquake implications for variations in fault zone frictional properties 1 gps time series following the september 25 2003 ut tokachi oki earthquake m w 8 0 reveal significant deformation we use the network inversion filter to invert for the spatial and temporal evolution of afterslip in the 30 days following the earthquake afterslip is concentrated adjacent to the coseismic rupture zone between the 2003 rupture and the inferred source regions of the 1968 tokachi oki and the 1973 nemuro oki earthquakes the inversion shows a rapid decay of slip rate in the 2003 rupture zone with slower deceleration in the surrounding regions the stress velocity paths for the afterslip regions approximately follow d d in v 0 6 mpa suggestive of steady state velocity strengthening friction the complementary spatial pattern of coseismic rupture and afterslip may indicate along strike spatial variations of frictional properties although other interpretations can not be ruled out

ice ablation as evidence of climate change in the alps over the 20th century 1 over fifty years of cumulative annual mass balance data for several glaciers in the alps shows similar fluctuations which seem to provide evidence of a common climatic signal separate winter and summer mass balance measurements from the claridenfirn glacier in switzerland since 1914 and the sarennes glacier france since 1949 show that 1 the annual mass balance is primarily driven by the summer mass balance term and 2 melting rate variations with time are very similar for these two glaciers located 290 km apart the increase in the ablation rate of 0 5 cm w e day 1 between the two periods 1954 1981 and 1982 2002 over these two glaciers corresponds to a 20 wm 2 rise in the energy flux at the glacier surface these results suggest that a common summer melting rate change may have affected the alps as a whole detailed observations on the sarennes glacier show that the origin of this strong increase in summer ablation since 1982 is not only a rise in the summer melting rate but also an increase in the ablation period during the months of september and october

co and postseismic characteristics of indian sub continent in response to the 2004 sumatra earthquake abstract the m w 9 3 sumatra earthquake of december 26 2004 caused extensive coseismic displacements globally measurements of which were made essentially using modern geodetic techniques this earthquake induced considerable perturbation in stress distribution as far as 8000 km away from the epicenteral region which is tending to relax to its normal rates as seen from postseismic transient deformation the monitoring of crustal displacements from strategically located sites using gps provides coseismic as well as postseismic deformation that facilitates the understanding of the fault geometry elastic thickness postseismic relaxation mechanisms rheology and earthquake recurrence time interval we investigated coseismic and postseismic gps derived displacements in indian region together with the gps data collected from andaman and sumatra region it is found that while ew displacements are significantly large in peninsular india those in the region to the north of central india tectonic zone citz are relatively small we could delineate the postseismic transients from position time series and interpreted them in terms of viscoelastic relaxation it is inferred that the postseismic deformation is characterized by a power law viscoelastic flow in the mantle in indian peninsula region the timescale parameter of the exponential decay 250 days would require an extremely low viscosity for the upper mantle relying on the prevailing coseismic and postseismic displacement fields the present study also reflects upon the contemporary litho tectonics of the indian sub continent

three dimensional viscoelastic finite element model for postseismic deformation of the great 1960 chile earthquake 2 5 10 19 pa s for the continental upper mantle the model well explains the gps observations numerical tests suggest that the continental mantle viscosity value is reasonably well constrained the model shows the prolonged postseismic seaward motion of the inland area to be a unique feature of earthquakes with very long rupture along strike and large coseismic fault slip for short rupture and small coseismic slip the motion will stop very quickly after the earthquake explaining why this phenomenon is not more commonly observed with an oceanic mantle viscosity of 10 20 pa s the model also provides an explanation for tide gauge constrained postseismic uplift 200 km from the trench that had previously been explained using a model of prolonged afterslip of a deep segment of the chile subduction fault index terms 1236 geodesy and gravity rheology of the lithosphere and mantle 8160 1242 geodesy and gravity seismic deformations 7205 3230 mathematical geophysics numerical solutions 7209 seismology earthquake dynamics and mechanics 7260 seismology theory and modeling keywords postseismic deformation viscoelastic stress relaxation gps finite element modeling chile subduction zone upper mantle viscosity

time dependent distributed afterslip on and deep below the izmit earthquake rupture surface deformation transients measured with the global positioning system during the 87 days between the 17 august 1999 izmit earthquake and the 12 november 1999 duzce earthquake indicate rapidly decaying aseismic fault slip on and well below the coseismic rupture elastic model inversions for time dependent distributed fault slip using a network inversion filter approach show that afterslip was highest between and below the regions of maximum coseismic slip and propa gated downward to or even below the base of the crust maximum afterslip rates decayed from greater than 2 m yr immediately after the i zmit earthquake to about 1 2 m yr just prior to the duzce earthquake maximum afterslip occurred below the eastern karadere rupture segment and near the i zmit hypocenter afterslip in the upper 16 km decayed more rapidly than that below the seismogenic zone these observations are consistent with a phase of rapid aseismic fault slip concentrated near the base of the seismogenic zone continued loading from the rapid deep afterslip along the eastern rupture zone is a plausible mechanism that helped trigger the nearby mw 7 2 12 november duzce earthquake

statistical modelling of the surface mass balance variability of the morteratsch glacier switzerland strong control of early melting season meteorological conditions in this study we analyse a 15 year long time series of surface mass balance smb measurements performed between 2001 and 2016 in the ablation zone of the morteratsch glacier complex engadine switzerland for a better understanding of the smb variability and its causes multiple linear regressions analyses are performed with temperature and precipitation series from nearby meteorological stations up to 85 of the observed smb variance can be explained by the mean may june july temperature and the total precipitation from october to march a new method is presented where the contribution of each month s individual temperature and precipitation to the smb can be examined in a total sample of 2 24 16 8 million combinations more than 90 of the observed smb can be explained with particular combinations in which the may june july temperature is the most recurrent followed by october temperature the role of precipitation is less pronounced but autumn winter and spring precipitation are always more important than summer precipitation our results indicate that the length of the ice ablation season is of larger importance than its intensity to explain year to year variations the widely used june july august temperature index may not always be the best option to describe smb variability through statistical correlation

postseismic deformation in chile constraints on the asthenospheric viscosity by means of a spherical earth model with maxwell rheology an analysis of the postseismic deformation field due to the viscoelastic relaxation of the mantle and asthenosphere following the great 1960 chile earthquake is performed due to the exceptional energy release of that earthquake geomorphological evidences of postseismic deformation are available in a broad area surrounding the rupture zone the comparison of the synthetic results with the available data allows to put some constraints on the viscosity of the asthenosphere beneath the chilean region values between 8 1019 and 1020pa s are compatible with the available postseismic deformation field data

interseismic deformation above the sunda megathrust recorded in coral microatolls of the mentawai islands west sumatra past half century vary from 2 to 14 mm yr 1 and increase southwestward toward the subduction trench the pattern is consistent with rates of subsidence measured by a sparse network of continuously recording global positioning system cgps stations and with locking of a 400 km long section of the underlying subduction megathrust between about 1s and 4s this record of subsidence and tilting extending nearly a century into the past implies that the region is advancing toward the occurrence of another giant earthquake however evidence of episodic rather than steady subsidence reflects a behavior that is more complex than simple elastic strain accumulation and relief most prominent of these episodes is an extensive emergence subsidence couplet in about 1962 which may be the result of rapid aseismic slip on the megathrust between the islands and the trench lower subsidence rates recorded by the corals since about 1985 may reflect failure on many small patches within the locked section of the megathrust

mobility of continental mantle evidence from postseismic geodetic observations following the 1992 landers earthquake the crust around the rupture zone of the 1992 landers earthquake has continued to deform in the years following the earthquake at rates 3 times greater than pre earthquake rates we use a combination of global positioning system gps and synthetic aperture radar insar data collected during a 3 year epoch following the earthquake in order to investigate postseismic mechanisms responsible for the high transient velocities in order to maximize the potential signal from viscoelastic relaxation we evaluate and model postseismic relaxation following the first few months of documented accelerated deformation the combination of gps and insar data allows us to establish viscoelastic relaxation of the lower crust and upper mantle as the dominant postseismic process and to discriminate among possible viscoelastic models the data particularly require the presence of a highly ductile uppermost mantle beneath the central mojave domain with temperature between the wet and dry basalt solidus this is consistent with independent seismic and geochemical inferences of a regionally warm uppermost mantle further consideration of seismic velocity variations in conjunction with faulting patterns within the mojave desert suggests that the primary faulting characteristics of the mojave desert namely the pervasive late cenozoic deformation within the eastern california shear zone versus the near absence of faults in the western mojave domain are controlled by the rheology of the uppermost mantle

postseismic mantle relaxation in the central nevada seismic belt holocene acceleration of deformation and postseismic relaxation are two hypotheses to explain the present day deformation in the central nevada seismic belt cnsb discriminating between these two mechanisms is critical for understanding the dynamics and seismic potential of the basin and range province interferometric synthetic aperture radar detected a broad area of uplift 2 to 3 millimeters per year that can be explained by postseismic mantle relaxation after a sequence of large crustal earthquakes from 1915 to 1954 the results lead to a broad agreement between geologic and geodetic strain indicators and support a model of a rigid basin and range between the cnsb and the wasatch fault

global postseismic rebound of a viscoelastic earth theory for finite faults and application to the 1964 alaska earthquake a spherically symmetric earth model with viscoelastic rheology is used to study the postseismic rebound associated with finite lithospheric dislocations we perform a systematic study of surface deformations due to sources characterized by two and three dimensional faults modeled by a linear and planar distribution of point sources our approach is based on the normal mode technique for a layered earth with linear viscoelastic rheology and allows for a self consistent description of the time evolution of postseismic displacements due to strike and dip slip faults as a case study we compare the predicted horizontal displacements due to the 1964 alaska earthquake with very long baseline interferometry vlbi baselines changes observed in this region in the period 1984 1989 although subduction and postglacial isostatic adjustment are expected to contribute significantly to present day velocities our results show that the postseismic rebound due to the 1964 alaska earthquake plays a relevant role in the changes of several vlbi baselines the last section is devoted to the analysis of the evolution of other north american baselines as suggested by recent investigations based on forward approaches isostatic readjustment of the earth s crust in response to the melting of the last pleistocene ice sheets is a major contributor to baseline variations in this area our results indicate that a correct interpretation of vlbi baseline changes in north america should account also for the effects of postseismic deformation

upper mantle rheology from grace and gps postseismic deformation after the 2004 sumatra andaman earthquake 1 mantle rheology is one of the essential yet least understood material properties of our planet controlling the dynamic processes inside the earth s mantle and the earth s response to various forces with the advent of grace satellite gravity measurements of mass displacements associated with many processes are now available in the case of mass displacements related to postseismic deformation these data may provide new constraints on the mantle rheology we consider the postseismic deformation due to the m w 9 2 sumatra 26 december 2004 and m w 8 7 nias 28 march 2005 earthquakes applying wavelet analyses to enhance those local signals in the grace time varying geoids up to september 2007 we detect a clear postseismic gravity signal we supplement these gravity variations with gps measurements of postseismic crustal displacements to constrain postseismic relaxation processes throughout the upper mantle the observed gps displacements and gravity variations are well explained by a model of visco elastic relaxation plus a small amount of afterslip at the downdip extension of the coseismically ruptured fault planes our model uses a 60 km thick elastic layer above a viscoelastic asthenosphere with burgers body rheology the mantle below depth 220 km has a maxwell rheology assuming a low transient viscosity in the 60 220 km depth range the grace data are best explained by a constant steady state viscosity throughout the ductile portion of the upper mantle e g 60 660 km this suggests that the localization of relatively low viscosity in the asthenosphere is chiefly in the transient viscosity rather than the steady state viscosity we find a 8 10 18 pa s mantle viscosity in the 220 660 km depth range this may indicate a transient response of the upper mantle to the high amount of stress released by the earthquakes to fit the remaining misfit to the grace data larger at the smaller spatial scales cumulative afterslip of about 75 cm at depth should be added over the period spanned by the grace models it produces only small crustal displacements our results confirm that satellite gravity data are an essential complement to ground geodetic and geophysical networks in order to understand the seismic cycle and the earth s inner structure

implications of postseismic gravity change following the great 2004 sumatra andaman earthquake from the regional harmonic analysis of grace intersatellite tracking data 1 we report gravity recovery and climate experiment grace satellite observations of coseismic displacements and postseismic transients from the great sumatra andaman islands thrust event mw 9 2 earthquake in december 2004 instead of using global spherical harmonic solutions of monthly gravity fields we estimated the gravity changes directly using intersatellite range rate data with regionally concentrated spherical slepian basis functions every 15 day interval we found significant step like coseismic and exponential like postseismic behavior in the time series of estimated coefficients from may 2003 to april 2007 for the spherical slepian functions after deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models the large spatial coverage and uniform accuracy of our grace solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake grace data our preferred interpretation of the long wavelength components of the postseismic gravity change is biviscous viscoelastic flow we estimated a transient viscosity of 5 1017 pa s and a steady state viscosity of 5 1018 1019 pa s additional years of the grace observations should provide improved steady state viscosity estimates in contrast to our interpretation of coseismic gravity change the prominent postearthquake positive gravity change around the nicobar islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake

mass balance of rhonegletscher during 1882 83 1986 87 les bilans de masse effectues sur le glacier des sources du rhone alpes suisses pendant differentes periodes 1884 85 1908 09 1979 80 et 1981 82 sont presentes

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