application of stress release models to historical earthquakes from north china univariate and multivariate stress release models are fitted to historical earthquake data from north china it is shown that a better fit is obtained by treating separately the eastern part of the region including the north china plain and bohai sea and the western part of the region including the ordos plateau and its eastern boundary further improvement is obtained by fitting the large events m 7 6 and smaller events in the western region by different stress release models the comparisons are made by computing the likelihoods of the fitted models and discounting the number of parameters used by akaike s aic criterion the models are used to develop long term risk scenarios for the east and west regions

accelerating seismic release from a self correcting stochastic model 1 we investigate the conditions under which the stress release model a stochastic version of the elastic rebound model produces synthetic earthquake sequences characterized by accelerating seismic release asr in this model the level or stress of the process accumulates linearly with time through tectonic input and decreases as the result of earthquakes these stress drops correspond to some power of the energy released in the earthquakes either e0 5 benioff strain or e seismic moment earthquakes occur in a point process with rate controlled by the level of the process we hypothesize that the critical factor in the appearance of asr is the manner in which the event sizes depend on the level of the process this is modeled by the square root of energy released following either a tapered pareto or truncated gutenberg richter distribution with maximum earthquake size controlled by a tail off or truncation point as the tail off point becomes large so does the average size corresponding to an acceleration to criticality of the system we found that those cases where the underlying level of the process corresponded to accumulated seismic moment produced numerous asr sequences whereas those cases using accumulated benioff strain as the level did not these results suggest that the occurrence of asr is strongly dependent on how large earthquakes affect the dynamics of the fault system in which they are embedded and hopefully provide some insight into the mechanics of acceleration to criticality i e on the possible causes of occurrence nonoccurrence of asr

seismic moment distribution revisited i statistical results summary an accumulation of seismic moment data gathered over the previous decade justifies a new attempt at a comprehensive statistical analysis of these data herein more rigourous statistical techniques are introduced their properties investigated and these methods are employed for analysis of large modern data sets several theoretical distributions of earthquake size seismic moment frequency relations are described and compared we discuss the requirements for such distributions and introduce an upper bound or a corner moment for a distribution to have a finite energy or moment flux we derive expressions for probability density functions and statistical moments of the distributions we also describe parameter evaluation in particular how to estimate the seismic moment distribution for the largest earthquakes simulating earthquake size distributions allows for a more rigourous evaluation of distribution parameters and points to the limitations of the classical statistical analysis of earthquake data simulations suggest that several earthquakes approaching or exceeding the corner magnitude mc limit need to be registered to evaluate mc with reasonable accuracy using the harvard catalogue data we compare moment distribution parameters for various temporal spans of the catalogue for different tectonic provinces and depth ranges and for earthquakes with various focal mechanisms the statistical analysis suggests that the exponent b is universal b 0 60 0 65 for all moderate earthquakes the corner moment mc value determined by the maximum likelihood method both in subduction zones and globally is about 10 21 n m corresponding to the corner moment magnitude mc 8 0 for midoceanic earthquakes mc is apparently smaller for spreading ridges it is about 5 8 and for strike slip earthquakes on transform faults it decreases from 7 2 to 6 5 as the relative slip velocity of faults increases we investigate the seismic moment errors both random and systematic and their dependence on earthquake size the relative errors seem to decrease for larger events the influence of moment uncertainties on the parameter estimates is studied whereas the b values do not appear to be significantly influenced by the errors for the corner moment large errors can lead to substantially biased estimates we compare the harvard catalogue results with the earthquake data from instrumental catalogues in the first three quarters of the 20th century several very large earthquakes mi9 occurred around the middle of the century their magnitude values cannot be fitted by a modified gutenberg richter law with mc 8 0 8 5 among other factors this discrepancy can be explained by either substantially higher errors in the earlier magnitude values or by mc being higher for some subduction zones it is unlikely that data available presently or soon will be sufficient to determine the corner magnitude of 9 and above with reasonable precision using purely statistical methods

retrospective on the accelerating seismic release asr hypothesis controversy and new horizons abstract the hypothesis that large earthquakes may be preceded by a period of accelerating seismicity or accelerating seismic release asr was proposed about twenty years ago a compilation of almost one hundred peer reviewed publications on this topic since the late 1980s to the present day shows that the rate of asr studies increased gradually until 2004 but decreased afterwards this negative trend is amplified by a recent increase in the number of negative results and criticisms of the asr hypothesis the author suggests that much of the recent negativity regarding this topic is due to the formulation of this hypothesis as a power law fit to cumulative seismicity series this approach is intrinsically linked to the consensus for criticality evident from an overview of the asr literature to explain the emergence of power laws in earthquake populations the holistic view of the earth s crust as a complex system restricts seismicity pattern analyses to the study of main features such as power laws while a reductionist view would allow for more refined ones such a paradigm shift or sea change might be under way in the asr literature where in 2007 a new approach was proposed to explain the asr power law from combined concepts of elastic rebound and geometry reductionism versus holism is a fundamental problem that not only applies to the study of asr but also to the broader field of earthquake physics and earthquake predictability science

seismic moment distribution summary we review possible errors in determining the size of earthquakes we propose that the size distribution can be effectively defined only for earthquake sequences not for individual earthquakes as a result of the error analysis we question the validity of many reported correlations between the 6 value and spatio temporal characteristics of tectonics and seismicity the study of the distribution of earthquake seismic moment largely avoids the influence of these errors and biases and is therefore superior to the standard analysis of the magnitude frequency law the gamma distribution is applied to describe the distribution of seismic moments of earthquake sequences this distribution which generalizes the well known gutenberg richter g r relation is characterized by two parameters we use the maximum likelihood method to determine the parameters of the gamma distribution for worldwide earthquakes in different depth ranges the empirical distribution is derived from the moment tensor catalogue compiled by the harvard group the p value for scalar seismic moment of earthquake sequences an analogue of the 6 value in the g r magnitude frequency law is close to 1 2 for all earthquakes the value predicted by a critical branching model of seismicity this result which will be improved as more seismic moment data become available provides input for modelling of seismicity based on percolation or on self organized criticality models if 3 equals 1 2 then using the critical branching model we find that most small earthquakes in available catalogues are dependent shocks i e aftershocks even among earthquakes of intermediate magnitudes the number of dependent events may exceed that of independent events

patagonian and southern south atlantic view of holocene climate abstract we present a comprehensive 10be chronology for holocene moraines in the lago argentino basin on the east side of the south patagonian icefield we focus on three different areas where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change the 10be dated records are from the lago pearson herminita peninsula brazo upsala and lago frias areas which span a distance of almost 100 km adjacent to the modern icefield new 10be ages show that expanded glaciers and moraine building events occurred at least at 6120 390 n 13 4450 220 n 7 1450 or 1410 110 n 18 360 30 n 5 and 240 20 n 8 years ago furthermore other less well dated glacier expansions of the upsala glacier occurred between 1400 and 1000 and 2300 and 2000 years ago the most extensive glaciers occurred over the interval from 6100 to 4500 years ago and their margins over the last 600 years were well within and lower than those in the middle holocene the 10be ages agree with 14c limiting data for the glacier histories in this area we then link southern south american adjacent south atlantic and other southern hemisphere records to elucidate broader regional patterns of climate and their possible causes in the early holocene a far southward position of the westerly winds fostered warmth small patagonian glaciers and reduced sea ice coverage over the south atlantic although we infer a pronounced southward displacement of the westerlies during the early holocene these conditions did not occur throughout the southern mid high latitudes an important exception being over the southwest pacific sector subsequently a northward locus and or expansion of the winds over the patagonia south atlantic sector promoted the largest glaciers between 6100 and 4500 years ago and greatest sea ice coverage over the last few millennia the south patagonian icefield has experienced successive century scale advances superimposed on a long term net decrease in size our findings indicate that glaciers and sea ice in the patagonian south atlantic sector of the southern hemisphere did not achieve their largest holocene extents over the last millennium we conclude that a pattern of more extensive holocene ice prior to the last millennium is characteristic of the southern hemisphere middle latitudes which differs from the glacier history traditionally thought for the northern hemisphere

recent glacier mass changes in the gulf of alaska region from grace mascon solutions the mass changes of the gulf of alaska goa glaciers are computed from the gravity recovery and climate experiment grace inter satellite range rate data for the period april 2003 september 2007 through the application of unique processing techniques and a surface mass concentration mascon parameterization the mass variations in the goa glacier regions have been estimated at high temporal 10 day and spatial 2 2 arc degrees resolution the mascon solutions are directly estimated from a reduction of the grace k band inter satellite range rate data and unlike previous grace solutions for the goa glaciers do not exhibit contamination by leakage from mass change occurring outside the region of interest the mascon solutions reveal considerable temporal and spatial variation within the goa glacier region with the largest negative mass balances observed in the st elias mountains including the yakutat and glacier bay regions the most rapid losses occurred during the 2004 melt season due to record temperatures in alaska during that year the total mass balance of the goa glacier region was 84 5 gt a 1 contributing 0 23 0 01 mm a 1 to global sea level rise from april 2003 through march 2007 highlighting the large seasonal and interannual variability of the goa glaciers the rate determined over the period april 2003 march 2006 is 102 5 gt a 1 which includes the anomalously high temperatures of 2004 and does not include the large 2007 winter balance year snowfall the mascon solutions agree well with regional patterns of glacier mass loss determined from aircraft altimetry and in situ measurements

geomorphological evidence for variations of the north patagonian icefield during the holocene abstract elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies here we present new geomorphological evidence of the patterns of glacier behaviour around the north patagonian icefield during the holocene mapping is based on visual interpretation of landsat 7 etm and terra aster satellite images including the contemporary glaciers areas of ice scoured bedrock trimlines glacial lineations terminal moraines sandur and fluvial sediments deltas and ice contact deposits and alluvial fans recession of the icefield is marked by three distinct moraine sets these moraine sets are interpreted as marking terminal positions related to the little ice age and two preceding but as yet undated phases of holocene glacier expansion large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features reflecting topographic limits to glacier expansion indicating that caution is required in the interpretation of previous 14c dates obtained from these moraines there are strong contrasts in the patterns of glacier behaviour between the east and west sides of the north patagonian icefield which cannot be attributed simply to an east west differential in the rates of change of atmospheric temperature and precipitation we argue here that glacier response to first order climate forcing is tempered by second order controls introduced by regional scale topographic effects notably glacier drainage basin extent and area topographic controls on glacier snout morphology and differences in terminal environment calving non calving during glacier recession

hazardous processes and events from glacier and permafrost areas lessons from the chilean and argentinean andes glacier and permafrost hazards such as glacial lake outburst floods and rock ice avalanches cause significant socio economic damages worldwide and these processes may increase in frequency and magnitude if the atmospheric temperature rises in the extratropical andes nearly 200 human deaths were linked to these processes during the twentieth century we analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio economic damages in this region in historic time including glacial lake outburst floods ice and rock ice avalanches and lahars to unravel their causes and geomorphological impacts in the extratropical andes at least 15 ice dammed lakes and 16 moraine dammed lakes have failed since the eighteenth century causing dozens of floods some floods rank amongst the largest events ever recorded 5000 106 m3 and 229 106 m3 respectively outburst flood frequency has increased in the last three decades partially as a consequence of long term decades to centuries climatic changes glaciers shrinkage and lake growth short term days to weeks meteorological conditions i e intense and or prolonged rainfall and high temperature that increased meltwater production have also triggered outburst floods and mass movements enormous mass failures of glaciers and permafrost 10 106 m3 have impacted lakes glaciers and snow covered valleys initiating chain reactions that have ultimately resulted in lake tsunamis and far reaching 50 km flows the eruption of ice covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 106 m3 despite the importance of these events basic information about their occurrence e g date causes and geomorphological impact which is well established in other mountain ranges is absent in the extratropical andes a better knowledge of the processes involved can help to forecast and mitigate these events copyright 2014 john wiley sons ltd

satellite derived volume loss rates and glacier speeds for the juneau icefield alaska we provide a high resolution map of elevation change rates dh dt at the juneau icefield jif southeastern alaska in order to quantify its contribution to sea level rise between 2000 and 2009 2013 we also produce the first high resolution map of ice speeds at the jif which we use to constrain flux and look for acceleration we calculate dh dt using stacked digital elevation models dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm taking into account srtm c band penetration via comparison with srtm x band elevations overall the jif is losing mass less rapidly 0 13 0 12mw e a than other alaskan icefields 0 79mw e a we determine glacier speeds using pixel tracking on optical image pairs acquired from 2001 to 2010 by aster from radar image pairs acquired between 2007 and 2011 and from radar interferometry in 1995 we detect seasonal speed variations but no interannual acceleration ruling out dynamics as the cause of the observed thinning thinning must therefore be due to the documented warming in the region flux measurements confirm this for mendenhall glacier showing that calving constitutes only 2 5 5 of mass loss there

calving processes and the dynamics of calving glaciers abstract calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world calving rates can increase dramatically in response to increases in velocity and or retreat of the glacier margin with important implications for sea level change despite their importance calving and related dynamic processes are poorly represented in the current generation of ice sheet models this is largely because understanding the calving problem involves several other long standing problems in glaciology combined with the difficulties and dangers of field data collection in this paper we systematically review different aspects of the calving problem and outline a new framework for representing calving processes in ice sheet models we define a hierarchy of calving processes to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events the first order control on calving is the strain rate arising from spatial variations in velocity particularly sliding speed which determines the location and depth of surface crevasses superimposed on this first order process are second order processes that can further erode the ice margin these include fracture propagation in response to local stress imbalances in the immediate vicinity of the glacier front undercutting of the glacier terminus by melting at or below the waterline and bending at the junction between grounded and buoyant parts of an ice tongue calving of projecting submerged ice feet can be regarded as a third order process because it is paced by first or second order calving above the waterline first order calving can be represented in glacier models using a calving criterion based on crevasse depth which is a function of longitudinal strain rate modelling changes in terminus position and calving rates thus reduces to the problem of determining the ice geometry and velocity distribution realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini but an important limitation is that they cannot be used to model floating glacier termini or ice shelves alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models such models can explain a remarkable range of observed phenomena within a simple unifying framework including downglacier increases in velocity and strain rates where basal and or lateral drag diminishes flow acceleration in response to thinning through time the tendency for glaciers to stabilise at pinning points in relatively shallow water or fjord narrowings the constraints on ice shelf stability and the contrasts in calving rates between tidewater and freshwater calving glaciers many unresolved issues remain however including the role played by the removal of backstress in the acceleration of retreating calving glaciers and the controls on melting at and below the waterline

penetration depth of interferometric synthetic aperture radar signals in snow and ice digital elevation models of glaciated terrain produced by the nasa jet propulsion laboratory jpl airborne interferometric synthetic aperture radar insar instrument in greenland and alaska at the c 5 6 cm wave length and l band 24 cm frequencies were compared with surface elevation measured from airborne laser altimetry to estimate the phase center of the interferometric depth or penetration depth p on cold polar firn at greenland summit p 9 2m at c and 14 4m at l band on the exposed ice surface of jakobshavn isbrae west greenland p 1 2 m at c and 3 3 m at l band except on smooth marginal ice where p 15 5 m on colder marginal ice of northeast greenland p reaches 60 to 120 m at l band on the temperate ice of brady glacier alaska p is 4 2 m at c and 12 6 m at l band with little dependence on snow ice conditions the implications of the results on the scientific use of insar data over snow ice terrain is discussed

evolution of stress deficit and changing rates of seismicity in cellular automaton models of earthquake faults we investigate the internal dynamics of two cellular automaton models with heterogeneous strength fields and differing nearest neighbour laws one model is a crack like automaton transferring all stress from a rupture zone to the surroundings the other automaton is a partial stress drop automaton transferring only a fraction of the stress within a rupture zone to the surroundings to study evolution of stress the mean spectral density cal s k r of a stress deficit field is examined prior to and immediately following ruptures in both models both models display a power law relationship between cal s k r and spatial wavenumber k r of the form cal s k r sim k beta r in the crack model the evolution of stress deficit is consistent with cyclic approach to and retreat from a critical state in which large events occur the approach to criticality is driven by tectonic loading short range stress transfer in the model does not affect the approach to criticality of broad regions in the model the evolution of stress deficit in the partial stress drop model is consistent with small fluctuations about a mean state of high stress behaviour indicative of a self organised critical system despite statistics similar to natural earthquakes these simplified models lack a physical basis physically motivated models of earthquakes also display dynamical complexity similar to that of a critical point system studies of dynamical complexity in physical models of earthquakes may lead to advancement towards a physical theory for earthquakes

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

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

ice motion of the patagonian icefields of south america 1984 2014 2015 american geophysical union all rights reserved we present the first comprehensive high resolution mosaic of ice velocity of the northern npi and southern patagonian icefields spi from multiple synthetic aperture radar and optical data collected between 1984 and 2014 the results reveal that many of the outlet glaciers extend far into the central ice plateaus which implies that changes in ice dynamics propagate far inside the accumulation area we report pronounced seasonal to interannual variability of ice motion on pio xi and jorge montt a doubling in speed of jorge montt a major slow down of o higgins significant fluctuations of upsala and a deceleration of san rafael which illustrate the need for sustained continuous time series of ice motion to understand the long term evolution of the rapidly thinning icefields the velocity product also resolves major ambiguities in glacier drainage in areas of relatively flat topography illustrating the need to combine topography and flow direction to map drainage basins

application of the stress release model to the nankai earthquake sequence southwest japan abstract the stress release model was applied to the nankai earthquakes which occurred in an area off the kii peninsula and shikoku island in the southwest of japan these are considered to be inter plate earthquakes the result of relative movement between the eurasian and the philippine sea plates the dates and sizes of earlier events were determined from historical documents recurrence intervals of the earthquakes were distributed in a range from around 90 to 210 years the stress release model attempts to provide a general formulation of the idea of the elastic rebound theory the hazard rate of the model is given in the form of exp a0 b0t c0s t where a0 b0 and c0 are the parameters adjusted to the data the function of s t corresponds to the stress released by the events up to time t the adjusted parameters are estimated through the optimization of the likelihood function by using the akaike information criterion aic the stress release model is compared with models based on a renewal process several cases were studied using subsets of the sequence the best example of the stress release model in comparison with renewal models is observed in the case of the eight most recent events this model evaluates the timing of the next event in later years and in a narrower time range than those obtained from the renewal models

multi decadal ice velocity and elevation changes of a monsoonal maritime glacier hailuogou glacier china digital elevation models dems of the ablation area of hailuogou glacier china produced from advanced spaceborne thermal emission and reflection radiometer aster data obtained in 2009 differential gps dgps data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long and short term glacier surface elevation change dh dt the mean dh dt of the ablation area over 43 years 1966 2009 is 1 1 0 4 m a 1 since 1989 the thinning has accelerated significantly ice velocities measured by dgps at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus ranging from 41 0 m a 1 approaching the glacier terminus to a maximum of 205 0 m a 1 at the base of an icefall our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics which are driven by different factors for different regions and periods

heterogeneity and the earthquake magnitude frequency distribution regional earthquake populations are widely observed to have power law magnitude frequency statistics whether earthquake distributions on individual faults are similarly power law is presently the subject of considerable research effort recent careful observations suggest that event statistics on rough faults are power law whereas earthquake distributions on smooth faults are better described by a characteristic model in which there are more large earthquakes than would be expected by extrapolation from the distribution of small events here the relation between heterogeneity and the magnitude frequency distribution is investigated in a cellular automaton that includes new nearest neighbor stress transfer rules which produce realistic stress concentrations the results agree with the suggestion that smooth faults have more characteristic earthquake distributions and support the view that an earthquake s size is controlled by rupture arrest

the influence of debris flow rheology on fan morphology owens valley california we have investigated factors controlling the surface morphology of debris flow fans comprising the bajada along the western slope of owens valley california these fans have average slopes of 4 an extensive network of abandoned boulder lined channels rough undulatory surfaces near the range front and smooth distal surfaces field relationships and mechanical considerations indicate that the channels of the bajada are products of fluvial incision and not debris flow scour this is significant because detailed geomorphic maps indicate that the channels strongly influence the pattern of debris flow deposition the locus of debris flow deposition on a channelized fan surface is set by the interaction of debris flows with the channel system and is controlled by channel size channel gradient flow volume flow hydrograph and flow rheology debris flow behavior is most directly controlled by variations in bulk sediment concentration and its influence on flow rheology whereas low sediment concentration debris flows tend to smooth the surface of the lower fan spreading into thin sheets and filling channels and surface undulations repeated deposition of high sediment concentration debris flows produces the rugged topography of the upper fan the texture of the fan surface rough or smooth is determined by the relative volumetric importance of these two types of debris flow in addition channel avulsions and the associated long term shifting of depositional loci are driven by in channel deposition of debris flows with the highest sediment concentrations these debris flows therefore play a critical role in determining both the structure of the channel network and the long term pattern of deposition on the fan surface as a whole we infer that the frequency distribution of debris flow rheologies set by source terrain geology and hydrology is an important control on fan morphology

spatial variability of glacier elevation changes in the swiss alps obtained from two digital elevation models 1 massive glacier thinning in the alps during the past 20 years is documented by direct mass balance measurements on nine regularly observed glaciers how representative this limited sample of glaciers is for the entire alps however remained uncertain the near global digital terrain model from the srtm enables a closer analysis of this question which is of fundamental importance to assess overall glacier volume change here we present elevation changes from 1985 to 1999 for about 1050 glaciers in the swiss alps the analysis reveals extreme thickness losses 80 m for flat low lying glacier tongues and a strong overall surface lowering the mean cumulative mass balance of the nine glaciers with direct measurements 10 8 m w e agrees well with the mean change of the entire region from dem differencing 11 m w e and can thus be considered to be representative mean thickness change of individual glaciers is correlated with their size elevation and exposure to solar irradiation this implies that mass losses of large glaciers can be underestimated when they are directly inferred from values measured at much smaller glaciers

temporal variations of seismic parameters in tehran region the study of earthquake precursors can lead to deliver an entirely measurable time varying estimation of the coming events which is strongly based on physical and geological principals and fully responsive to any future examination the temporal variation of the seismic parameters such as b values in the gutenberg richter formula logn a bm some details of the pre shock accelerating moment release amr and the variation of the thirumalai and mountain tm metric before the past big event is investigated in the vicinity of the tehran city the temporal variation of the b value in some cases strongly supports the assumption that it has potential to be used as a precursory signal in addition analysis of the pre shock amr along with the inverse tm metric signal in the region shows deviations from the background long term behavior prior to some of the bigger events in the studied area the aggregation of these signs suggests that a combination of studied physical precursors has a potential which could be employed in a medium term earthquake warnings

precursory seismic activation and critical point phenomena in this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability we illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion we draw an analogy between the steam explosion and a characteristic earthquake and show that the power law activation associated with the spinodal instability is essentially identical to the power law increase in benioff strain observed prior to characteristic earthquakes we find that theory and actual data give very similar results

rapid disintegration of alpine glaciers observed with satellite data analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s by using digitized glacier outlines inferred from the 1973 inventory and landsat thematic mapper tm satellite data from 1985 to 1999 we obtained area changes of about 930 alpine glaciers the 18 area reduction as observed for the period 1985 to 1999 1 3 a corresponds to a seven times higher loss rate compared to the 1850 1973 decadal mean extrapolation of area change rates and cumulative mass balances to all alpine glaciers yields a corresponding volume loss of about 25 km since 1973 highly individual and non uniform changes in glacier geometry disintegration indicate a massive down wasting rather than a dynamic response to a changed climate our results imply stronger ongoing glacier retreat than assumed so far and a probable further enhancement of glacier disintegration by positive feedbacks

where glaciers meet water subaqueous melt and its relevance to glaciers in various settings glacier change is ubiquitous but the fastest and largest magnitude changes occur in glaciers that terminate in water this includes the most rapidly retreating glaciers and also several advancing ones often in similar regional climate settings furthermore water terminating glaciers show a large range in morphology particularly when ice flow into ocean water is compared to that into freshwater lakes all water terminating glaciers share the ability to lose significant volume of ice at the front either through mechanical calving or direct melt from the water in contact here we present a review of the subaqueous melt process we discuss the relevant physics and show how different physical settings can lead to different glacial responses we find that subaqueous melt can be an important trigger for glacier change it can explain many of the morphological differences such as the existence or absence of floating tongues subaqueous melting is influenced by glacial runoff which is largely a function of atmospheric conditions this shows a tight connection between atmosphere oceans and lakes and glaciers subaqueous melt rates even if shown to be large should always be discussed in the context of ice supply to the glacier front to assess its overall relevance we find that melt is often relevant to explain seasonal evolution can be instrumental in shifting a glacier into a different dynamical regime and often forms a large part of a glacier s mass loss on the other hand in some cases melt is a small component of mass loss and does not significantly affect glacier response

ice thickness of the northern half of the patagonia icefields of south america from high resolution airborne gravity surveys author s gourlet p rignot e rivera a casassa g abstract 2015 american geophysical union all rights reserved we employ high resolution high precision helicopter borne gravity observations of the northern npi and southern patagonia icefields spi south america to infer ice thickness and bed topography using a three dimensional model constrained by fjord and lake bathymetry and a land ice mask the results reveal thicker ice than the reflecting horizon of radar sounders with 1 km deep ice for glaciar san rafael and colonia npi and 1 5 km deep ice for glaciar occidental spi these bedrock troughs channelize fast motion of ice from the plateaus combining ice motion and thickness we calculate balance accumulation levels of 3 6 m yr water equivalent for the plateaus bed elevation remains below sea lake level 15 20 km inland for jorge montt and o higgins which favors retreat and is at sea level for san rafael which halted its retreat the results demonstrate the utility of airborne gravity surveys for providing critical data on ice volume bed elevation and balance accumulation of temperate ice masses

glacier calving observed with time lapse imagery and tsunami waves at glaciar perito moreno patagonia calving plays a key role in the recent rapid retreat of glaciers around the world however many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain when calving occurs at a glacier front surface water waves arise over the ocean or a lake in front of glaciers to study calving processes from these surface waves we performed field observations at glaciar perito moreno patagonia we synchronized time lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise a total of 1074 calving events were observed over the course of 39 d during austral summer calving occurred twice more frequently than in spring the cumulative distribution of calving interevent time interval followed exponential model implying random occurrence of events in time we further investigated wave properties and found that source to sensor distance can be estimated from wave dispersion within 20 error we also found that waves produced by different calving types showed similar spectra in the same frequency range between 0 05 0 2 hz and that the amplitude of surface waves increased with the size of calving this study demonstrates the potential of surface wave monitoring for understanding calving processes

further applications of the stochastic stress release model to historical earthquake data abstract the stochastic stress release model provides a stochastic version of the elastic rebound model which may be used to fit simulate and forecast occurrence of large earthquakes within a seismic region this paper reviews its applications to historical earthquakes from china iran and japan thereby extending and supporting earlier work on the chinese historical data the model generally provides an improvement in fit over poisson models with either constant rate or linear trend a crucial factor is the identification of suitable subregions which can act as largely independent seismic units in northern china divisions into two and four such units are considered based on recognized geophysical subdivisions in iran the best results are obtained from a subdivision into three such units the situation in japan seems more complex a preliminary model with two units gives a significant improvement of fit in one out of the two cases in all regions treating the subregions separately gives marked improvements over treating the whole region as a single unit however the quality of fit within subregions differs sharply from case to case pointing to substantial differences in the seismic regimes as reflected in the historical data

precursory accelerating seismic moment release amr in a synthetic seismicity catalog a preliminary study 1 a power law like acceleration of seismic moment release amr has been proposed as a precursor to large earthquakes because of problems with real world data we have used a synthetic seismicity model of 256 interacting faults embedded in a 3 d elastic half space to search for periods of amr preceding the largest events mw 7 1 in only 5 of 18 cases does the amr model fit the data significantly better than a linear moment release and then only weakly so this proportion or higher occurs in 8 of 1000 randomized catalogs we conclude that either amr is unlikely to be a common precursor or that factors contributing to the amr pattern in the real world are missing from the synthetic model

what controls an earthquake s size results from a heterogeneous cellular automaton the controls on an earthquake s size are examined in a heterogeneous cellular automaton that includes stress concentrations which scale with rupture size large events only occur when stress is highly correlated with strength over the entire fault although the largest events occur when this correlation is the highest the magnitude of the correlation has no predictive value as events of all magnitudes occur during times of high stress strength correlation rather the size of any particular event depends on the local stress heterogeneity encountered by the growing rupture patterns of energy release with time for individual ruptures reflect this heterogeneity and many show nucleation type behaviour although there is no relation between the duration of nucleation phase and the size of the event these results support the view that earthquake size is determined by complex interactions between previous event history and dynamic stress concentrations and suggest that deterministic earthquake prediction based on monitoring nucleation zones will not be possible

repeated intermittent earthquake cycles in the san francisco bay region forecasts of future earthquake hazard in the san francisco bay region sfbr are dependent on the distribution used for the possible magnitude of future events based on the limited observed data it is not possible to statistically distinguish between many distributions with very different tail behavior these include the modified and truncated gutenberg richter distributions and a composite distribution assembled by the working group on california earthquake probabilities there is consequent ambiguity in the estimated probability of very large and hence damaging events a related question is whether the energy released in earthquakes is a small or large proportion of the stored energy in the crust corresponding loosely to the ideas of self organized criticality and intermittent criticality respectively however the sfbr has experienced three observed accelerating moment release amr cycles terminating in the 1868 hayward 1906 san andreas and 1989 loma prieta events a simple stochastic model based on elastic rebound has been shown to be capable of producing repeated amr cycles in large synthetic catalogs we propose that such catalogs can provide the basis of a test of a given magnitude distribution via comparisons between the amr properties of the real and synthetic data our results show that the truncated gutenberg richter distribution produces amr behavior closest to the observed amr behavior the proviso is that the magnitude parameters b and m max are such that a sequence of large events that suppresses activity for several centuries is unlikely to occur repeated simulation from the stochastic model using such distributions produces 30 year hazard estimates at various magnitudes which are compared with the estimates from the 2003 working group on california earthquake probabilities

analysis of sub pixel snow and ice extent over the extratropical andes using spectral unmixing of historical landsat imagery abstract with more than 30 years of imagery the landsat database offers potential insights into changes in the global cryosphere in this study a landsat based sub pixel fractional snow covered area retrieval model based on spectral unmixing is applied and validated over a southern andes study region an application analyzing minimum annual snow ice covered areas is presented as an example of the utility of the existence of such a model and the landsat database the model was validated using high resolution imagery aggregated to the nominal landsat resolution showing good correlation for both fresh snow and ice old snow presence using annual minimum snow ice retrievals from landsat 5 and 7 the presence of trends in each snow ice covered pixel area was assessed for the 1986 2013 historical period and three metrics were examined pixels with significant negative trends total area loss and areas with any absolute negative change significant negative area reduction trends in most of the glacier fronts were found with a loss of approximately 15 of the original 241 km2 glacierized snow area between 1986 and 2011 trends in fractional values were compared with those derived from traditional binary classification of snow and significant discrepancies were observed even though the binary classification identified a greater total areal loss 33 vs 23 km2 when comparing scenes from the beginning and the end of the study period the fractional algorithm identified a larger number of pixels with significant negative trends between 1986 and 2013 42 3 vs 10 5 km2 the binary algorithm resulted in consistent overestimations of ice and snow area and does not offer the ability for identifying subpixel changes the method could enable future monitoring of andean and other glaciers and snow cover at a sub pixel scale over large scales and with landsat 8 in orbit a continuous stream of more than 30 years of data is already available

non poissonian earthquake occurrence in coupled stress release models and its effect on seismic hazard summary most seismic hazard estimations are based on the assumption of a poisson process for earthquake occurrence even though both observations and models indicate a departure of real seismic sequences from this simplistic assumption instrumental earthquake catalogues show earthquake clustering on regional scales while the elastic rebound theory predicts a periodic recurrence of characteristic earthquakes on longer timescales for individual events recent implementations of time dependent hazard calculations in california and japan are based on quasi periodic recurrences of fault ruptures according to renewal models such as the brownian passage time model however these renewal models neglect earthquake interactions and the dependence on the stressing history which might destroy any regularity of earthquake recurrences in reality to explore this we investigate the coupled stress release model a stochastic version of the elastic rebound hypothesis in particular we are interested in the time variability of the occurrence of large earthquakes and its sensitivity to the occurrence of gutenberg richter type earthquake activity and fault interactions our results show that in general large earthquakes occur quasi periodically in the model the occurrence probability of large earthquakes is strongly decreased shortly after a strong event and becomes constant on longer timescales although possible stress interaction between adjacent fault zones does not affect the recurrence time distributions in each zone significantly it leads to a temporal clustering of events on larger regional scales the non random characteristics especially the quasi periodic behaviour of large earthquakes are even more pronounced if stress changes due to small earthquakes are less important the recurrence time distribution for the largest events is characterized by a coefficient of variation from 0 6 to 0 84 depending on the relative importance of small earthquakes

use of remotely sensed and field data to estimate the contribution of chilean glaciers to eustatic sea level rise a synthesis of glaciological studies carried out in chile during recent decades is presented including inventories and records of glacier variations fluctuations of whicharerelatedtoregionalclimate changeandtheircontributionto eustatic sea level rise basedupon satelliteimagery aerialphotographsandhistorical records newdata for 20 glaciersarepresented these newdata arecombinedwithpreviousrecordsto coverthe historicalvariations of95 chileanglaciers oftheseglaciers only 6 showa netadvance during the study period 6 show no significant change while 88 have retreated the contributionof chileanglaciersto eustatic sea levelrisehasbeenestimatedtobeapproxi mately 8 2 of the worldwide contribution of small glaciers on earth during the last 51years most of the glacier variations are thought to have been driven by a temperature increase which has been documented by several stations in chile anomalies in rainfall and the decreasing trend in annual precipitation shown at a few stations have probably also contributedtoglacier recession basedonobservedclimatictrends itisexpectedthat the glacier retreat will continue that the mass balance will continue to show a negative trend and that thinning rates will increase all of these changes will ultimately affect the availability of water resources in chile that depend on glacierizedbasins

the upper truncated power law applied to earthquake cumulative frequency magnitude distributions evidence for a time independent scaling parameter earthquake cumulative frequency magnitude cfm distributions are described by the gutenberg richter power law where the exponent is the b value although it has been reported that the b value changes before large earthquakes we find that an upper truncated power law applied to earthquake cfm distributions yields a time independent scaling parameter herein called the value we analyze earthquakes associated with subduction of the nazca plate beneath south america and find a region of isolated seismic activity at depths greater than 500 km between 20 s and 30 s for the entire record 1973 2000 the earthquake cfm distribution in this isolated region is well described by a gutenberg richter power law with b 0 58 the data set includes several large seismic events with m b 6 8 a power law applied to the cfm distributions for short time intervals between the large events yields b values greater than the b value for the entire record cfm distributions for the short time intervals are better described by an upper truncated power law than by a power law the value determined by applying an upper truncated power law to the short time intervals is equal to the b value obtained by applying the gutenberg richter power law to the entire record temporal changes in b value are due to temporal fluctuations in maximum magnitude analysis of four flinn engdahl regions two in subduction zones and two along spreading ridges demonstrates wider applicability of the results the value is an unchanging characteristic of the system that may be determined from a short term record manuscript received 2 july 2001

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

air sea co2 fluxes along the coast of chile from co2 outgassing in central northern upwelling waters to co2 uptake in southern patagonian fjords 1 carbon system parameters measured during several expeditions along the coast of chile 23 s 56 s have been used to show the main spatial and temporal trends of air sea co2 fluxes in the coastal waters of the eastern south pacific chilean coastal waters are characterized by strong pco2 gradients between the atmosphere and the surface water with high spatial and temporal variability on average the direction of the carbon flux changes from co2 outgassing at the coastal upwelling region to co2 sequestering at the nonupwelling fjord region in chilean patagonia estimations of surface water pco2 along the patagonian fjord region showed that while minimum pco2 levels strong co2 undersaturation occurs during the spring and summer period maximum levels including co2 supersaturation occur during the austral winter co2 uptake in the patagonia fjord region during spring summer is within the order of 5 mol c m 2 yr 1 indicating a significant regional sink of atmospheric co2 during that season we suggest that the co2 sink at patagonia most probably exceeds the co2 source exerted by the coastal upwelling system off central northern chile

variations in sediment yield over the advance and retreat of a calving glacier laguna san rafael north patagonian icefield abstract bathymetric and sub bottom acoustic data were collected in laguna san rafael chile to determine sediment yields during the little ice age advance and subsequent retreat of san rafael glacier the sediment volumes and subaqueous landforms imaged are used to interpret the proglacial dynamics and estimate erosion rates from a temperate tidewater glacier over a complete advance retreat cycle sediment yields from san rafael glacier averaged 2 7 107 m3 a since the end of the little ice age circa ad 1898 corresponding to average basin wide erosion rates of 23 9 mm a the highest erosion rates 68 23 mm a occurred at the start of the retreat phase and have since been steadily decreasing erosion rates were much lower during glacial advance averaging at most 7 mm a than during retreat such large glacial sediment yields over two centuries of advance and retreat suggest that the contribution of sediments stored subglacially cannot account for much of the sediment being delivered to the terminus today the detailed sub bottom information of a proglacial lagoon yields important clues as to the timing of erosion deposition and transfer of glacigenic sediments from orogens to the continental shelves and the influence of glacier dynamics on this process

application of a bayesian approach for estimation of seismic hazard parameters in some regions of the circum pacific belt the maximum possible regional magnitude mmax and other seismic hazard parameters like which is the slope of gutenberg richter law and which is the intensity rate of seismic activity are estimated in eight seismic regions of the west side of the circum pacific belt the bayesian approach as described by pisarenko et al 1996 pisarenko and lyubushin 1997 1999 is a straightforward technique of estimating the seismic hazard the main assumptions for the method applied are a poissonian character of seismic events flow a frequency magnitude law of gutenberg richter s type with cutoff maximum value for the estimated parameter and a seismic catalog which have a rather sizeable number of events we also estimated the quantiles of the probabilistic distribution of the apparent mmax for future given time length intervals

general theory of the modified gutenberg richter law for large seismic moments abstract it is well known that the gutenberg richter power law distribution has to be modified for large seismic moments because of energy conservation and geometrical reasons several models have been proposed either in terms of a second power law with a larger b value beyond a crossover magnitude or based on a hard magnitude cut off or a soft magnitude cut off using an exponential taper since large scale tectonic deformation is dominated by the very largest earthquakes and since their impact on loss of life and properties is huge it is of great importance to constrain as much as possible the shape of their distribution we present a simple and powerful probabilistic theoretical approach that shows that the gamma distribution is the best model given the two hypotheses that the gutenberg richter power law distribution holds in absence of any condition and that one or several constraints are imposed either based on conservation laws or on the nature of the observations themselves the selection of the gamma distribution does not depend on the specific nature of the constraint we illustrate the approach with two constraints the existence of a finite moment release rate and the observation of the size of a maximum earthquake in a finite catalog our predicted soft maximum magnitudes compare favorably with those obtained by kagan for the flinn engdahl regionalization of subduction zones collision zones and midocean ridges

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

physical basis for statistical patterns in complex earthquake populations models predictions and tests understanding the physics of earthquakes and the space time patterns they produce is illuminated by the use of coarse grained models and simulations that capture the basic physical processes and that are amenable to analysis we present a summary of ideas that describe the nucleation growth and arrest of earthquakes on individual faults under shear loading we find that faults reside in a metastable state near a classical spinodal that governs the nucleation and growth of slip events the roughness of an associated stress distribution field x t determines whether slip events are confined within the initial high stress patch or break away and grow to become very large we find a critical value of roughness that is associated with a first order order disorder transition we also give a number of predictions examples and applications of these ideas and indicate how they might be tested through systematic observational programs

estimating rate and state friction parameters using a two node stochastic model for aftershocks abstract the well known omori and modified omori omori utsu empirical formulae describe the decay in the rate of occurrence of aftershocks dieterich s rate and state dependent constitutive law for aftershock production produces a similar temporal formula with physically interpretable parameters such as the shear stressing rates the normal stress and a fault constitutive parameter this naturally leads to an interest in estimating these parameters from earthquake catalogs which requires a simpler stochastic model an alternative to the epidemic type aftershock sequence etas model is the two node seismic transfer and release model where one node represents the mainshock process and a secondary node represents the aftershock zone the aftershock decay rate in the two node model equals that derived from dieterich s rate and state dependent constitutive law and the inclusion of aseismic slip in the aftershock zone allows for values of p 1 in the best matching modified omori law the two node model can be easily fitted to aftershock data and has an application to aftershock stacking for estimating p values the equivalence between the rate and state and two node aftershock rates forms a bridge between a formula derived from physical considerations and a phenomenological stochastic model we show how this can be exploited by identifying physical units for the parameters in the latter to estimate the fault constitutive parameters and the stressing rates in dieterich s formula through a best fit inversion on real aftershock sequences the procedure is illustrated using data from four japanese earthquakes

seismic moment frequency relation for shallow earthquakes regional comparison we determine the parameter values for the seismic moment frequency relation using flinn engdahl s regionalization of global seismicity and the harvard centroid moment tensor data the earthquake size distribution is approximated by the gamma law a version of the gutenberg richter distribution with an exponential taper at the maximum moment there is no statistically significant variation of the fj value the analog of the b value for all seismic regions except for the midocean ridge systems for the latter regions fj 0 93 whereas for all other zones fj 0 63 the maximum moment mxg can be statistically evaluated only for subduction zones treated as a whole mxg 10 21 2 x 10 22 newton m which corresponds to the worldwide mxg value for other regions as well as for single subduction zones mxg is determined by comparing the number of events in each zone with the seismic moment rate calculated on the basis of the nuvel 1 model of plate motion for subduction zones we obtain the estimate of mxg which agrees with the statistical value giving evidence that most tectonic deformation is released by earthquakes we test the hypothesis that no statistically significant variation in mxg occurs in subduction and continent collision zones the hypothesis cannot be rejected with available data for the midocean ridges the mxg estimate cannot be unambiguously determined it is quite possible that the estimate is significantly biased because only a small part of tectonic deformation at the ridges is released by earthquakes these results have importance in evaluating seismic risk and may also lead to developing a physical theory for earthquake generation

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

fast tidewater glaciers some iceberg calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets no temperate tidewater glaciers are known to have floating termini but many polar and subpolar tidewater glaciers do the fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed which may approach zero and the longitudinal back stress on the terminus the terminus boundary condition the calving relation is imperfectly known yet is vital to the dynamics of these glaciers calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested the calving relations for floating termini are virtually unknown this together with the imperfect understanding of basal sliding inhibits confidence in our understanding of the stability of these glaciers columbia glacier alaska is an instructive example because observations have been made on the major changes in its geometry calving rate and dynamics that have occurred in less than 10 years the calving flux has increased more rapidly than the glacier flux causing thinning and retreat as a result the ice velocity has increased markedly the short term velocity changes relate to changes in back pressure ice recession tidal changes and the flux of water injected to the bed these results have relevance to the mechanisms of basal sliding glacier surges and the stability of marine ice streams

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

the linked stress release model for spatio temporal seismicity formulations procedures and applications summary the linked stress release model is based on the build up of stress through elastic rebound and its dissipation in the form of earthquakes in addition stress can be transferred between large scale geological or seismic features the model can be statistically fitted to both historical and synthetic seismicity catalogues and through simulation can be used to create probabilistic forecasts of earthquake risk we review the genesis of the model provide some observations on forecasting using the model and follow with a comprehensive review of applications to date a systematic procedure for identification of the best model is illustrated by data from the persian region we then consider the evaluation of fitted models using residual point processes and information gains implications of the use of benioff strain rather than seismic moment are discussed the sensitivity of the model to regionalization magnitude errors catalogue incompleteness catalogue size and declustering magnitude cut off is then considered in detail with reference to data from north china the latter data are also used to illustrate the model evaluation techniques introduced earlier some technical material on numerical fitting simulation and calculation of the information gain is given in an appendix

large earthquake cycles and intermittent criticality on heterogeneous faults due to evolving stress and seismicity 1 we analyze evolving stress and seismicity generated by three realizations of a discrete model of a strike slip fault in a three dimensional 3 d elastic half space using five functions of stress and five functions of seismicity the first model f has realistic dynamic weakening static minus dynamic frictions the second fc has zero critical dynamic weakening and the third sys is constrained to produce only system size events the results for model f show cyclical development saturation and destruction of fluctuations and long range correlations on the fault punctuated by the system size events the development stage involves evolution of stress and seismicity to distributions having broad ranges of scales evolution of response functions toward scale invariant behavior increasing seismicity rate and event sizes and increasing hypocenter diffusion most functions reach asymptotically stable values around 2 3 of the cycle and then fluctuate until one event cascades to become the next large earthquake in model fc the above evolution is replaced by scale invariant statistical fluctuations while in model sys the signals show simple cyclic behavior the results suggest that large earthquake cycles on heterogeneous faults with realistic positive dynamic weakening are associated with intermittent criticality produced by spontaneous evolution of stress heterogeneities toward a critical level of disorder having a broad range of scales the stress evolution and development of large earthquake cycles may be tracked with seismicity functions

late holocene advance of the collins ice cap king george island south shetland islands radiocarbon dates of incorporated moss indicate advance of the collins ice cap on fildes peninsula king george island after 650 cal yr bp ad 1300 broadly contemporaneous with the little ice age as defined in europe during that time the glacier extended less than 400 500 m beyond its present day margin moreover radiocarbon data indicate that this was the most extensive advance of the last 3500 cal years prior to 650 cal yr bp the ice must have been at or behind its present position furthermore the data indicate that climate conditions prior to the late holocene advance may have been similar to or possibly warmer than today