separation of coseismic and postseismic gravity changes for the 2004 sumatra andaman earthquake from 4 6 yr of grace observations and modelling of the coseismic change by normal modes summation eodspatiale grgs for comparison the release 04 solutions of the center for space research csr are also inves tigated after a spectral windowing or a gaussian spatial smoothing results are shown both in terms of geoid height changes and gravity variations coseismic and postseismic gravitational changes estimated from the different gravity solutions are globally similar although their spa tial extent and amplitude depend on the type of filter used in the processing of grace fields the highest signal to noise ratio is found with the grgs solutions the postseismic signature has a spectral content closer to the grace bandwidth than the coseismic signature and is therefore better detected by grace the coseismic signature consists mainly of a strong gravity decrease east of the sunda trench in the andaman sea a gravity increase is also detected at a smaller scale west of the trench the model for the coseismic gravity changes agrees well with the coseismic signature estimated from grace regarding the overall shape and orientation location with respect to the trench and order of magnitude coseismic gravity changes are followed by a postseismic relaxation that are well fitted by an increasing expo nential function with a mean relaxation time of 0 7 yr the total postseismic gravity change consists of a large scale positive anomaly centred above the trench and extending over 15 of latitude along the subduction after 26 months the coseismic gravity decrease has been partly compensated by the postseismic relaxation but a negative anomaly still remains south of phuket a dominant gravity increase extends over 15 of latitude west of the trench being maximal south of the epicentre area by investigating analyses of two global hydrology models and one ocean general circulation model we show that our grace estimates of the coseismic and postseismic gravitational changes are almost not biased by interannual variations originat ing from continental hydrology and ocean circulation in the subduction area and in the central part of the andaman sea while they are biased by several gal in the malay peninsula

the last british ice sheet a review of the evidence utilised in the compilation of the glacial map of britain this paper reviews the evidence presently available as at december 2003 for the compilation of the glacial map of britain see clark c d evans d j a khatwa a bradwell t jordan c j marsh s h mitchell w a bateman m d 2004 map and gis database of glacial landforms and features related to the last british ice sheet boreas 33 359 375 and http www shef ac uk geography staff clark chris britice html in an effort to stimulate further research on the last british ice sheet and promote a reconstruction of ice sheet behaviour based on glacial geology and geomorphology the wide range of evidence that has been scrutinized for inclusion on the glacial map is assessed with respect to the variability of its quality and quantity and the existing controversies in ice sheet reconstructions landforms interpreted as being of unequivocal ice marginal origin moraines ice contact glacifluvial landforms and lateral meltwater channels and till sheet margins are used in conjunction with available chronological control to locate former glacier and ice sheet margins throughout the last glacial cycle subglacial landforms drumlins flutings and eskers have been used to demarcate former flow patterns within the ice sheet the compilation of evidence in a regional map is crucial to any future reconstructions of palaeo ice sheet dynamics and will provide a clearer understanding of ice sheet configuration ice divide migration and ice thickness and coverage for the british ice sheet as it evolved through the last glacial cycle

potential and gravity changes raised by point dislocations summary we derive expressions in closed form which give the gravity potential changes caused by point dislocations they enable us to evaluate coseismic changes in surface gravity and geoid height numerical simulation shows that a great earthquake could cause a geoid height change of order 1 m

precise oxygen and hydrogen isotope determination in nanoliter quantities of speleothem inclusion water by cavity ring down spectroscopic techniques abstract speleothem inclusion water isotope compositions are a promising new climatic proxy but their applicability is limited by their low content in water and by analytical challenges we have developed a precise and accurate isotopic technique that is based on cavity ring down spectroscopy crds this method features a newly developed crushing apparatus a refined sample extraction line careful evaluation of the water carbonate adsorption effect after crushing chipped speleothem in a newly developed crushing device released inclusion water is purified and mixed with a limited amount of nitrogen gas in the extraction line for crds measurement we have measured 50 260 nl of inclusion water from 77 to 286 mg of stalagmite deposits sampled from gyokusen cave okinawa island japan the small sample size requirement demonstrates that our analytical technique can offer high resolution inclusion water based paleoclimate reconstructions the 1 reproducibility for different stalagmites ranges from 0 05 to 0 61 for 18 o and 0 0 to 2 9 for d the d vs 18 o plot for inclusion water from modern stalagmites is consistent with the local meteoric water line the 1000 ln values based on calcite and fluid inclusion measurements from decades old stalagmites are in agreement with the data from present day farmed calcite experiment combination of coeval carbonate and fluid inclusion data suggests that past temperatures at 9 10 thousand years ago ka and 26 ka were 3 4 0 7 c and 8 2 2 4 c colder than at present respectively

gravity changes due to the sumatra andaman and nias earthquakes as detected by the grace satellites a reexamination summary in this paper we study the geoid changes caused by the sumatra andaman earthquake 2004 december 26 and the nias earthquake 2005 march 28 using data from the gravity recovery and climate experiment grace satellites new is that we explore the possibility to separate the effects of the sumatra andaman and nias earthquakes based on correlation analysis we investigate the separability of the sumatra andaman and nias signals and the feasibility of separating the non seismic linear trend from the time dependent post seismic relaxation effect as input data we use 76 months of global geopotential coefficients from the gfz release 4 rl04 of grace data to suppress unphysical artefacts in grace data striping the grace coefficients are smoothed with an anisotropic decorrelation filter model parameters are estimated through a bayesian approach we compare our results with geophysical models of both earthquakes calculated based on the viscoelastic gravitational dislocation theory the slip models used are inverted from gps measurements our findings indicate that the inversion of grace data for the sumatra andaman effect will contain significant signal from the nias earthquake and will benefit from removing the modelled nias effect from the data comparing grace measurements to geophysical models reveals significant differences we suggest how the gps calibrated models may be improved to better fit the grace data in the first months after the earthquake we also find evidence for a fast process in the andaman sea possibly due to aseismic slip similar phenomena were observed in previous studies

rupture kinematics of the 2005 mw 8 6 nias simeulue earthquake from the joint inversion of seismic and geodetic data the 2005 mw 8 6 nias simeulue earthquake was caused by rupture of a portion of the sunda megathrust offshore northern sumatra this event occurred within an array of continuous global positioning system gps stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture thus this earthquake provides a unique opportunity to assess the source character istics of a megathrust event from the joint analysis of seismic data and near field static co seismic displacements based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip where the dip is determined to be 8 to 10 with corresponding moments of 1 24 10 22 to 1 00 10 22 n m respectively the geodetic constraints on slip distribution help to eliminate the trade off between rupture velocity and slip kine matics source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long period seismic waveforms 100 500 sec our results indicate a rela tively slow average rupture velocity of 1 5 to 2 5 km sec and long average rise time of up to 20 sec the earthquake nucleated between two separate slip patches one beneath nias and the other beneath simeulue island the gap between the two patches and the hypocentral location appears to be coincident with a local geological disrup tion of the forearc coseismic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accre tionary prism using the models from joint inversions we estimate the peak ground velocity on nias island to be about 30 cm sec an order of magnitude slower than for thrust events in continental areas this study emphasizes the importance of util izing multiple datasets in imaging seismic ruptures

post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

rock slope failure in the british mountains abstract in this first full review of extant quaternary rock slope failure rsf in the british mountains we provide a near complete inventory of 1082 sites 40 being rock slope deformations 40 arrested rockslides and 20 rock avalanches current rsf activity is negligible and this relict population is predominantly paraglacial with a parafluvial minority its spatial distribution is perplexing with rsf density varying greatly both regionally and locally in the scottish highlands eight main clusters account for 76 of rsf area in 15 of the montane area local concentrations occur in all the british ranges across high and low relief in core and peripheral locations and on varied geological and glaciological domains as conversely do extensive areas of sparsity even in similar lithologies generic interpretations are thus precluded geology is only a secondary control an association with concentrated erosion of bedrock ceb is proposed as a driver of intensified slope stresses ceb is most evident at those glacial breaches of main divides where the most vigorous recent incision is inferred and also in some trough heads a clear association between rsfs and these late developing breaches is demonstrated in the highlands in 42 localities with sparsity away from them it is also seen in seven lake district localities glaciological models identify ice sheet volatility capable of driving breach ramification high magnitude paleoseismic events are generally unlikely to have provoked rsf clusters a few candidates are considered rsf has been underrated as an agent of mountain landscape evolution in britain its spatio temporal incidence may assist in calibrating regional ice sheet models and in assessing climate change impacts we argue that the ceb rsf association has global relevance in identifying primary drivers of mass movement in bedrock

gravity and potential changes due to shear and tensile faults in a half space analytic expressions derived from a simplified model are invaluable because they often provide deep insight into geophysical phenomena such is the case with potential and gravity changes here we present expressions of potential and gravity changes caused by faulting on a finite rectangular plane buried in a homogeneous half space the expressions can be used to evaluate coseismic changes in surface gravity and geoid height observed gravimetric data combined with our formulae thus provide constraints on the fault geometry and magnitudes of dislocation

coseismic gravity changes of the 2010 earthquake in central chile from satellite gravimetry 1 the first map of coseismic changes in gravity and geoid height has been drawn using the data from the gravity recovery and climate experiment grace satellites for the 2004 sumatra andaman earthquake here we present the second case of coseismic gravity change observation by satellite gravimetry i e the change caused by an interplate thrust earthquake that occurred on 27 february 2010 in central chile mw 8 8 gravity showed a negative jump with the largest drop of 5 gal on the back arc side the observed changes agree with those calculated assuming the realistic earth and fault parameters inferred from coseismic displacements of global positioning system gps stations gravity in this area shows large seasonal and inter annual variability and postseismic gravity changes could be isolated only by carefully removing hydrological signals

crustal dilatation observed by grace after the 2004 sumatra andaman earthquake we report the detection of an earthquake by a space based measurement the gravity recovery and climate experiment grace satellites observed a 15 microgalileo gravity change induced by the great december 2004 sumatra andaman earthquake coseismic deformation produces sudden changes in the gravity field by vertical displacement of earth s layered density structure and by changing the densities of the crust and mantle grace s sensitivity to the long spatial wavelength of gravity changes resulted in roughly equal contributions of vertical displacement and dilatation effects in the gravity measurements the grace observations provide evidence of crustal dilatation resulting from an undersea earthquake

hydrogen and oxygen stable isotope signatures of goethite hydration waters by thermogravimetry enabled laser spectroscopy abstract the hydrogen and oxygen stable isotope composition 2h and 18o values of mineral hydration waters can give information on the environment of mineral formation here we present and validate an approach for the stable isotope analysis of mineral hydration waters based on coupling a thermogravimetric analyzer with a laser based isotope ratio infrared spectroscopy instrument picarro l 2130i which we abbreviate as tga iris tga iris generates 2h and 18o values of liquid water samples with precision for 2h of 1 2 and for 18o of 0 17 for hydration waters in goethite precision for 2h ranges from 0 3 to 1 6 and for 18o ranges from 0 17 to 0 27 the ability of tga iris to generate detailed water yield data and 2h and 18o values of water at varying temperatures allows for the differentiation of water in varying states of binding on mineral surfaces and within the mineral matrix tga iris analyses of hydrogen isotopes in goethite yields 2h values that reflect the hydrogen of the oh phase in the mineral and are comparable to that made by irms and found in the literature in contrast 18o values on goethite reflect the oxygen in oh groups bound to fe fe oh group and not the oxygen bound only to fe fe o group in the mineral crystal lattice and may not be comparable to literature 18o values made by irms that reflect the total o in the mineral tga iris presents the possibility to isotopically differentiate the various oxygen reservoirs in goethite which may allow the mineral to be used as a single mineral geothermometer tga iris measurements of hydration waters are likely to open new avenues and possibilities for research on hydrated minerals

ocean contribution to co seismic crustal deformation and geoid anomalies application to the 2004 december 26 sumatra andaman earthquake large earthquakes do not only heavily deform the crust in the vicinity of the fault they also change the gravity field of the area affected by the earthquake due to mass redistribution in the upper layers of the earth besides that for sub oceanic earthquakes deformation of the ocean floor causes relative sea level changes and mass redistribution of water that have again a significant effect on the gravity field to model these deformations sea level changes and gravity field perturbations self consistently we use an adapted version of the sea level equation sle that has been used for glacial isostatic adjustment studies the sea level equation next to our normal mode model for seismic solid earth modeling allows us to compute a gravitationally self consistent solution for the co seismic relative sea level surface deformation and geoid height changes we apply our geographically detailed models to the case of the 2004 december 26 sumatra andaman earthquake recent studies that have modeled the ocean mass effect on co seismic gravity change for this specific earthquake show model results that indicate a broad negative change in geoid height around the fault due to ocean water redistribution de linage et al 2009 melini et al 2010 our model results for the ocean contribution to geoid height differ from these studies in the sense that we find a pattern similar to the elongated dipole pattern of the solid earth model outputs for gravity and vertical deformation together with a relatively small broad negative geoid height change we explain the relation between outcomes for geoid height relative sea level and vertical deformation of the ocean floor and we confront our model results with a least squares estimation of the co seismic discontinuity in grace derived gravity field time series we show that taking into account the contribution of ocean water redistribution to the co seismic geoid height change next to a compressible solid earth model is essential to explain the predominant negative co seismic geoid anomalies from the grace gravity field solutions besides we introduce a detailed approach to modeling an earthquake in a normal mode model that better approximates realistic continuous slip on the fault plane than models that do not distribute slip with depth to demonstrate the importance of the slip distribution we show the differences in outcomes for modeled geoid height and vertical deformation

grace measurements of mass variability in the earth system monthly gravity field estimates made by the twin gravity recovery and climate experiment grace satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers the annual cycle in the geoid variations up to 10 millimeters in some regions peaked predominantly in the spring and fall seasons geoid variations observed over south america that can be largely attributed to surface water and groundwater changes show a clear separation between the large amazon watershed and the smaller watersheds to the north such observations will help hydrologists to connect processes at traditional length scales tens of kilometers or less to those at regional and global scales

local gravity anomalies produced by dislocation sources rundle 1978 and walsh and rice 1979 have shown that the change in the vertical component of gravity is proportional to uplift for a spherical source of dilatation and for slip on an infinitely long dip slip fault in the first case no free air gravity anomaly is produced and in the second case no bouguer gravity anomaly gravity anomalies due to other dislocation sources in three dimensions are as follows for strike slip faulting the ratio of the gravity change to uplift depends upon position however the gravity change contours are roughly similar to those corresponding to a zero free air gravity anomaly nor is the ratio constant for dip slip faulting except for the two special cases of dip slip on a vertical fault and horizontal slip on a horizontal fault neither of which produce a bouguer anomaly the bouguer anomaly produced by an open horizontal crack is the same as would be produced had the material within the crack been mined out without deforming the solid if the horizontal crack were filled with material of density equal to the host rock a good approximation to sill formation no bouguer anomaly is produced for cracks of other inclinations the ratio of gravity change to uplift is not constant thus dilatancy in general does not correspond to the absence of a free air anomaly as might be suggested by the special case of a spherical source of dilatation for two dimensional models a cylindrical source of dilatation produces no free air gravity anomaly dip slip faulting produces no bouguer anomaly and open cracks produce a bouguer anomaly equal to that which would be produced had the material within the crack been mined out without deforming the solid a two dimensional crack filled with material of density equal to that of the host rock would produce no bouguer anomaly jachens et al 1983 have reported temporal changes in gravity elevation and area strain along the san andreas fault in southern california such that the bouguer anomaly apparently remains unchanged and the uplift to strain ratio is about 100 km several dislocation mechanisms are proposed that fulfill these constraints but these mechanisms appear to be rather contrived and are not regarded as satisfactory explanations

the effect of the subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model in order to interpret observed short term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model in particular the transient stages of growing or shrinking water filled cavities at the ice bedrock interface were analysed it was found that the sliding velocity was larger when cavities were growing than when they had reached the steady state size for a given water pressure the smallest sliding velocities occurred while cavities were shrinking when cavitation is substantial a small drop of water pressure below the steady state value e g by 0 5 bar can temporarily cause backward sliding a limiting water pressure at which sliding becomes unstable is derived the consequences of more realistic assumptions than those of the model are discussed

weertman regelation multiple refreezing events and the isotopic evolution of the basal ice layer a simple model is developed to s imulate the isotopic fractionation which accompanies weertman regelation at the bed of temperate based glaciers the fractionation equations of jouzel and souchez 1 982 are applied to multiple refreezing events over measured glacier bed profiles and mass balance is maintained as the basal ice and meltwater produced at one bedrock hummock enter the next s imulation results indicate that undeformed regelation ice layers are on the order of millimetres to centimetres thick often being completely melted at the stoss face of certain hummocks and exceptionally reaching a thickness in excess of 1 0 cm neither the internal morphology nor the isotopic composition of these layers is constant but both vary down glacier in accordance with bedrock configuration a glacier wide fractionation process is identified whereby heavy isotopes are preferentially removed fro m the basal meltwater film and incorporated into the basal ice this process might go some way to explaining the anomalously light isotopic composition measured in base flow waters leaving some glaciers vertical isotope profiles through undeformed basal ice layers are reconstructed and show that significant isotopic excursions can occur at a scale of millimeteres while the range of isotopic compositions within such m ulti layered regelation ice is greater than that which would occur in ice produced by a single refreezing event in circumstances where the regelation system is disrupted by removal of film waters into a network of linked cavities i t is found that the remaining basal ice may be significantly enriched in heavy isotopes relative to the composition of the initial mass inputs to the system heavy isotope enrichment of this m agnitude and consideration of the thickness of the basal ice layers concerned may explain the absence of recorded basal ice samples heavy enough to h ave been formed in equilibrium with subglacial precipitates sampled at one of the sites glacier de tsanfleuron and reported in an earlier paper

reconstructing past glacier dynamics and erosion from glacial geomorphic evidence snowdon north wales bedrock surfaces exposed around llyn llydaw north wales demonstrate contrasting styles of erosion beneath a late devensian ice sheet and a loch lomond stadial lls valley glacier ice sheet erosion involved lee side fracturing surface fracture wear and abrasive wear while lls erosion was primarily by abrasive wear preservation of ice sheet erosional features indicates limited rates of erosion during the lls analysis of the geometry and distribution of erosional markings suggests that the low erosional capacity of the lls glacier was due to a low basal sliding velocity this prevented the formation of lee side cavities reduced the debris flux over the bed and minimised particle bed contact loads reconstructions of the mass balance and geometry of the lls glacier indicate that most of its balance velocity could be achieved by internal deformation alone a combination of low subglacial water pressures and an unusually rough substrate explain the low sliding velocities high bed roughness is due to the absence of leeside cavities and a change in flow orientation between ice sheet and lls times which meant that the lls glacier was in contact with roughness elements which were generated in cavities beneath the ice sheet

18o 16o and d h ratios of pedogenic kaolinite in a north american cenomanian laterite paleoclimatic implications abstract kaolinite gibbsite and quartz are the dominant minerals in samples collected from two outcrops of a cenomanian 95 ma laterite in southwestern minnesota a combination of measured yields and isotope ratios permitted mass balance calculations of the d and 18 o values of the kaolinite in these samples these calculations yielded kaolinite d values of about 73 and 18 o values of about 18 7 the d and 18 o values appear to preserve information on the ancient weathering system if formed in hydrogen and oxygen isotope equilibrium with water characterized by the global meteoric water line gmwl the kaolinite d and 18 o values indicate a crystallization temperature of 22 5 c a nominal paleotemperature of 22 c implies a 18 o value for the corresponding water of 6 3 the combination of temperature and meteoric water 18 o values is consistent with relatively intense rainfall at that mid paleolatitude location 40 n on the eastern shore of the north american western interior seaway the inferred cenomanian paleosol temperature of 22 c is in general accord with published mid cretaceous continental mean annual temperatures mat estimated from leaf margin analyses of fossil plants when compared with results from a published gcm based cenomanian climate simulation which specifies a latitudinal sea surface temperature sst gradient that was either near modern or smaller than modern the kaolinite paleotemperature of 22 c is closer to the gcm predicted mat for a smaller equator to pole temperature difference in the mid cretaceous moreover the warm kaolinite derived mid paleolatitude temperature of 22 c is associated with proxy estimates of high concentrations of atmospheric co 2 in the cenomanian the overall similarity of proxy and model results suggests that the general features of cenomanian continental climate in that north american locale are probably being revealed

co and postseismic deformation of the 28 march 2005 nias mw 8 7 earthquake from continuous gps data 1 global positioning system gps measurements registered up to 5m of coseismic displacements during the 28 march 2005 mw 8 7 nias earthquake indonesia the vertical offsets put tight constraints on the northern and southern limit of the rupture the inferred coseismic slip distribution indicates high slip patches near the epicenter and near the southern extent of the 26 december 2004 aceh andaman rupture where aftershocks have been abundant six months of postseismic time series are better fit with a logarithmic instead of exponential function suggesting that the postseismic deformation is likely controlled by afterslip our inversion model predicts afterslip to be concentrated both up and down dip from patches of maximum coseismic slip where aftershocks are sparse the shallow afterslip adds further evidence that the earthquake probably did not break the surface with implications for tsunami generation and instead caused aseismic deformation in shallow parts of the subduction zone after the event

topographic effects on coseismic gravity change for the 2011 tohoku oki earthquake and comparison with grace we estimate gravity changes due to coseismic horizontal deformation and inclined bathymetry referred to as topographic effects in this study associated with the 2011 tohoku oki earthquake using a layered half space dislocation model as an approximation we represent inclined topography with ramp body models in the near field of the earthquake and calculate topographic effects from both an inclined seafloor and moho the moho effect partly compensates that from the seafloor an additional contribution comes from seawater column variations as the sloped seafloor moves trenchward topographic effects are first order contributions to coseismic gravity changes for the 2011 tohoku oki earthquake after 300 km gaussian smoothing comparable to the spatial resolution of the gravity recovery and climate experiment grace topographic effects create a dominantly negative gravity pattern with amplitudes up to 1 1 gal for oceanic areas surrounding the epicenter there are discrepancies between model predictions 10 4 to 6 9 gal and grace observations 10 1 to 1 7 gal errors in the adopted fault slip model and difficulties in separating coseismic and postseismic deformation may contribute to these but topographic effects currently neglected in dislocation models are also responsible topographic effects ought to be included in coseismic fault slip and related gravity modeling for the 2011 tohoku oki earthquake and similar events in regions of steep topography

coseismic slip of the 2010 mw 8 8 great maule chile earthquake quantified by the inversion of grace observations abstract the 27 february 2010 mw 8 8 maule chile earthquake ruptured over 500 km along a mature seismic gap between 34 s and 38 s the concepcion constitucion gap where no large megathrust earthquakes had occurred since the 1835 mw 8 5 event notable discrepancies exist in slip distribution and moment magnitude estimated by various models inverted using traditional observations such as teleseismic networks coastal river markers tsunami sensors global positioning system gps and interferometric synthetic aperture radar insar we conduct a spatio spectral localization analysis based on slepian basis functions of data from gravity recovery and climate experiment grace to extract coseismic gravity change signals of the maule earthquake with improved spatial resolution 350 km half wavelength our results reveal discernible differences in the average slip between the grace observation and predictions from various coseismic models the sensitivity analysis reveals that grace observation is sensitive to the size of the fault but unable to separate depth and slip here we assume the depth of the fault is known and simultaneously invert for the fault plane area and the average slip using the simulated annealing algorithm our grace inverted fault plane length and width are 429 6 km 146 5 km respectively the estimated slip is 8 1 1 2 m indicating that most of the strain accumulated since 1835 in the concepcion constitucion gap was released by the 2010 maule earthquake

oxygen and hydrogen isotope variations among goethites α feooh and the determination of paleotemperatures abstract a plot of d vs 18o values from a diverse group of natural goethites defines a data array which is approximately parallel to the meteoric water line the 18o values range from 9 5 to 4 4 per mil while the corresponding d values vary from 202 to 94 per mil there is considerable scatter in the d vs 18o array which can be attributed primarily to different temperatures of mineral formation as determined previously yapp and pedley 1985 and confirmed in this study the goethite water d h fractionation factor is essentially independent of temperature over the range from 25 c to 145 c however the goethitewater 18 o 16 o fractionation factor does vary with temperature as indicated by initial goethite synthesis experiments conducted at 25 c 44 c and 62 c the synthetic goethite 18 g w values suggest that the natural goethites in this study formed at temperatures that may range from about 8 c to 66 c support for the validity of these approximate calculated temperatures is provided by a natural goethite sample from the atlantis ii deep in the red sea these results suggest that goethite can be used as a single mineral low temperature geothermometer perhaps more importantly goethite can be used in low temperature oxygen isotope mineral pair geothermometers such as chert goethite calcite goethite phosphate goethite etc

the importance of pressurized subglacial water in separation and sliding at the glacier bed l effet de l eau sous glaciaire sous pression sur le processus de glissement est examine a partir d un parametre appele indice de decollement du lit qui exprime les contraintes perpendiculaires au lit et la pression d eau les donnees proviennent de trois glaciers de formes differentes une loi puissance du type de weertman avec un exposant voisin de 3 modifiee pour tenir compte de l effet de la pression des eaux sous glaciaires apparait comme etant la meilleure

alpine subglacial hydrology abstract the size and shape of subglacial flow pathways exert a strong influence over the pressure and speed at which meltwaters are routed through glaciers these characteristics in turn influence glacier sliding velocity and the quantity and quality of bulk meltwaters discharging from glaciers in this paper we summarise four empirical research approaches that have been developed to improve our understanding of the subglacial hydrology of predominantly temperate based alpine glaciers investigations of bulk meltwater discharge and chemistry tracer studies proglacial bedrock investigations and borehole investigations as a result of linking these studies to conceptual or numerical models three arborescent and four non arborescent or distributed subglacial drainage configurations are described these drainage networks may be neither spatially nor temporally persistent but may compete with and replace each other on a seasonal basis a qualitative model of the temporal and spatial evolution of a typical alpine subglacial drainage system is advanced on the basis of research conducted at haut glacier d arolla switzerland

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

improved constraints on seismic source parameters of the 2011 tohoku earthquake from grace gravity and gravity gradient changes a new approach of using only the north component of gravity change from gravity recovery and climate experiment grace data reveals that a substantially higher spatial resolution of the observed seismic deformation following the 2011 tohoku earthquake is achievable at 333 km or longer here we show that grace observed north component of gravity change 17 6 1 1 gal and the corresponding gravity gradient change e g txz at 1 25 0 09 meotvos agree well with seismic gps model predictions localized slepian spectrum analysis further confirms that the grace gravity and gravity gradient changes agree well with seismic model spectra and have powers up to the limit of the grace solution complete to spherical harmonic degree 60 using the gravity observations for the fault parameter inversion via simulated annealing algorithm we show that the estimated slip orientation and centroid location are different from gps seismic solutions and potentially due to the additional offshore constraint from grace data

coseismic and post seismic signatures of the sumatra 2004 december and 2005 march earthquakes in grace satellite gravity s u m m a r y the grace satellite mission has been measuring the earth s gravity field and its temporal variations since 2002 april although these variations are mainly due to mass transfer within the geofluid envelops they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes however these last contributions are difficult to isolate because of the presence of noise and of geofluid signals and because of grace s coarse spatial resolution 400 km half wavelength in this paper we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from grace geoid products using a wavelet analysis of grace geoids products we show that the geoid variations caused by the 2004 december m w 9 2 and 2005 march m w 8 7 sumatra earthquakes can be detected at grace resolution the 2004 december earthquake produced a strong coseismic decrease of the gravity field in the andaman sea followed by relaxation in the area affected by both the andaman 2004 and the nias 2005 earthquakes we find two characteristic timescales for the relaxation with a fast variation occurring in the vicinity of the central andaman ridge we discuss our coseismic observations in terms of density changes of crustal and upper mantle rocks and of the vertical displacements in the andaman sea we interpret the post seismic signal in terms of the viscoelastic response of the earth s mantle the transient component of the relaxation may indicate the presence of hot viscous material beneath the active central andaman basin

glacial erosion and bedrock properties in nw scotland abrasion and plucking hardness and joint spacing subglacial erosion beneath glaciers occurs predominantly by abrasion and plucking producing distinct erosional forms the controls on the relative importance of abrasion vs plucking are poorly understood on the one hand glacial conditions that favour or suppress cavity formation ice velocity ice thickness and water pressure are thought to favour plucking or abrasion respectively conversely bedrock properties are also known to control landforms but this has rarely been analysed quantitatively in this study we compare landforms and bedrock properties of sandstone and quartzite at the bed of a palaeo ice stream near ullapool in nw scotland the boundary between the rock types is at right angles to the westward palaeo ice flow and palaeoglacial conditions on both rock types were similar we report quantitative parameters for bedrock properties schmidt hammer hardness and joint spacing and use morphometric parameters to analyse the landforms torridon sandstone is soft but thick bedded and with a wide joint spacing erosional bedforms include roche moutonnees with smoothed tops and concave stoss sides whalebacks and elongate p forms indicating a high proportion of abrasion over plucking cambrian quartzite is hard but thin bedded with narrow joint spacing erosional landforms are angular to subangular with abundant plucked lee faces suggesting a high proportion of plucking over abrasion hardness and joint spacing thus exert a strong control on subglacial erosional landforms and the mechanisms that formed them thus glacial conditions ice velocity ice thickness can only be inferred from glacial erosional landforms if the effects of bedrock properties of the substrate are considered

grace detects coseismic and postseismic deformation from the sumatra andaman earthquake 1 we show that spherical harmonic sh solutions of the gravity recovery and climate experiment grace are now of sufficient quality to observe effects of co seismic and post seismic deformation due to the rupture from the mw 9 3 sumatra andaman earthquake on december 26 2004 and its companion nias earthquake mw 8 7 on march 28 2005 the improved ggm 03 sh level 2 solutions and improved filtering methods provide estimates with spatial resolution comparable to earlier estimates from range rate level 1 grace data the gravityfield disturbance extends over 1800 km along andaman and sunda subduction zones and changes with time following events gravity changes may be due to afterslip viscoelastic relaxation or other processes associated with dilatation satellite gravity measurements from grace provide a unique new measure of deformation and post seismic processes associated with major earthquakes especially in areas which are primarily oceanic citation chen j l c r wilson b d tapley and s grand 2007 grace detects coseismic and postseismic deformation from the sumatraandaman earthquake geophys res lett 34 l13302

bedrock surface roughness and the distribution of subglacially precipitated carbonate deposits implications for formation at glacier de tsanfleuron switzerland two carbonate deposits are identified on the exposed bedrock surface in the forefield of glacier de tsanfleuron switzerland macrocrystalline sparite and microcrystalline micrite comparison of the distributions of these forms with lee side slope facets identified by high pass filtering of a flow parallel bedrock profile at a range of frequencies reveals two significant results first while the distribution of sparite is consistent with formation in the lee side of subglacial bedrock hummocks that of micrite is not this contrasts with previous investigations in which both sparite and micrite have been considered to form by mineral concentration and precipitation during the refreezing of regelation related basal meltwaters in the lee side of bedrock hummocks alternative mechanisms of micrite formation involving carbonate deposition and or precipitation within subglacial bedrock hollows are proposed second the distribution of sparite is most strongly correlated with the distribution of lee side slope facets identified by filtering at a frequency equivalent to a hummock wavelength of c 0 1 m this correspondence indicates empirically that pressure related melting and refreezing regelation operates most effectively around bedrock hummocks that are shorter than c 0 1 m 1998 john wiley sons ltd

hydraulics of subglacial cavities modele theorique du comportement a l etat stationnaire des cavites remplies d eau et interconnectees sur le lit du glacier

coseismic slip and afterslip of the great mw 9 15 sumatra andaman earthquake of 2004 we determine coseismic and the first month postseismic deformation associated with the sumatra andaman earthquake of 26 december 2004 from near field global positioning system gps surveys in northwestern sumatra and along the nicobar andaman islands continuous and campaign gps measurements from thailand and malaysia and in situ and remotely sensed observations of the vertical motion of coral reefs the coseismic model shows that the sunda subduction mega thrust ruptured over a distance of about 1500 km and a width of less than 150 km releasing a total moment of 6 7 7 0 10 22 n m equivalent to a magnitude m w 9 15 the latitudinal distribution of released moment in our model has three distinct peaks at about 4 n 7 n and 9 n which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated t waves our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very long period surface waves the tsunami predicted from this model fits rela tively well the altimetric measurements made by the jason and topex satellites neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave the near field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500 sec long seismic rupture the postseismic geodetic moment of about 2 4 10 22 nm mw 8 8 is equal to about 30 5 of the coseismic moment release evolution of postseismic deformation is consistent with rate strengthening frictional afterslip online material summary of geodetic data used in this study

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

gravity anomaly from faulting on a layered spherical earth with application to central japan abstract the gravity anomaly resulting from mass redistribution from an earthquake source point dislocation is re explored in a spherical earth geometry using a previously developed method of determining the green s functions for the static displacement field on a layered earth i obtain the corresponding green s functions for the perturbed gravitational potential and gravity anomaly in a spherical harmonic expansion the synthesized gravity anomaly includes the effects of changes in the intrinsic density distribution due to divergence of the displacement field and vertical displacement along level surfaces in density stratification displacement numerical examples of the bouguer gravity anomaly produced on a layered crustal model show that the contribution of intrinsic density changes dominates over the contribution of stratification displacement application to central japan yields a new image of a buried thrust structure suspected of having ruptured in the 1891 nobi earthquake

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

gravitational gradient changes following the 2004 december 26 sumatra andaman earthquake inferred from grace summary it has been demonstrated that the gravity recovery and climate experiment grace spaceborne gravimetry data are capable of observing coseismic gravity changes resulting from great earthquakes such as the 2004 december 26 sumatra andaman event mw 9 1 9 3 here we show for the first time that refined deformation signals from the 2004 december 26 sumatra andaman earthquake mw 9 1 9 3 together with the 2005 march 28 nias earthquake mw 8 6 can be revealed by deriving the full gravitational gradient tensor from grace monthly gravitational field the grace inferred coseismic gravitational gradient changes agree well with coseismic slip model predictions since the high frequency contents in gravitational field variation can be amplified by deriving the gravitational gradients the grace derived coseismic gravitational gradient changes clearly delineate the fault lines locate significant slips and better define the extent of the coseismic deformation

chemical weathering studies in relation to geomorphological research in southeastern canada abstract although chemical weathering provides fundamental information relevant to geomorphology the subject has been overlooked during the 20th century in canada this paper provides an overview of the current state of canadian research on chemical weathering in southeastern canada and takes into account three spatial and temporal contexts 1 the formation of bedrock morphology by chemical weathering 2 occurrences characteristics and age of saprolites and 3 contemporary chemical denudation rates long term geomorphological evolution of southeastern canadian landscapes shows that chemical weathering has played an important role an example is taken from the laurentide region of the canadian shield north of montreal quebec the present topography resulted from the stripping of the former weathering mantle and from the probable subsequent modification of the weathering front first by the action of hillslope processes and rivers and then by glaciers before and during plio pleistocene times the present landscape reflects the timing of the formation of erosion surfaces and of the stripping of the paleozoic cover rocks and exposure of the shield since the late seventies several isolated occurrences of saprolite soil profiles have been discovered in eastern canada and prompted a renewal of the study of these materials about the cenozoic evolution of these regions one of the problems in this field of research is the dating of saprolites and their inclusion in a chronostratigraphic framework along with the other cenozoic surficial deposits and landforms because of the multiple factors involved in the development of secondary minerals in saprolites during the course of weathering it is preferable to distinguish the dating of saprolites from the study of their mineralogical and geochemical evolution fortunately several new techniques are becoming available for the absolute dating of surficial deposits and saprolites including the use of cosmogenic radionuclides saprolites provide a strong potential field of research for our understanding of the geological evolution of eastern canada during the cenozoic contemporary weathering and erosion rates are fields of research that have gained increasing interest recently since modeling landscape geochemical response can be applied to various environmental stress situations such as acidification by rain and forest harvesting rock type may be the main factor explaining the large differences between watersheds in fact variability of cation removal in the temperate zone is probably most closely related to flow paths of water investigations at different scales from entire watersheds to slopes to individual pedons highlight the problem in the catamaran brook watershed new brunswick water chemistry is explained by a mix of groundwater and soil solution from the horizons at the base of the floodplain soils geochemical mass balances based on net outputs give little information on the weathering reactions of primary minerals the weathering products or on the nature of the weathering processes that provide the dissolved load of streams mineralogic and petrographic analysis of selected soil pedons are necessary to determine weathering reactions and their role as sources or sinks for bases silica aluminum and iron in the various compartments through which water percolates before it reaches the stream

post seismic relaxation following the great 2004 sumatra andaman earthquake on a compressible self gravitating earth summary the mw 9 0 2004 december 26 sumatra andaman and mw 8 7 2005 march 28 nias earthquakes which collectively ruptured approximately 1800 km of the andaman and sunda subduction zones are expected to be followed by vigorous viscoelastic relaxation involving both the upper and lower mantle because of these large spatial dimensions it is desirable to fully account for gravitational coupling effects in the relaxation process we present a stable method of computing relaxation of a spherically stratified compressible and self gravitating viscoelastic earth following an impulsive moment release event the solution is cast in terms of a spherical harmonic expansion of viscoelastic normal modes for simple layered viscoelastic models which include a low viscosity oceanic asthenosphere we predict substantial post seismic effects over a region several 100s of km wide surrounding the eastern indian ocean we compare observed gps time series from ten regional sites mostly in thailand and indonesia beginning in 2004 december with synthetic time series that include the coseismic and post seismic effects of the 2004 december 26 and 2005 march 28 earthquakes a viscosity structure involving a biviscous burgers body rheology in the asthenosphere explains the pattern and amplitude of post seismic offsets remarkably well

improved source parameter constraints for five undersea earthquakes from north component of grace gravity and gravity gradient change measurements abstract the innovative processing of gravity recovery and climate experiment grace data using only the north component of gravity change and its corresponding gravity gradient changes allows the enhancement of the spatial resolution for coseismic deformation signals here we report the study of five undersea earthquakes using this technique the 2004 sumatra andaman earthquake the 2007 bengkulu earthquake the 2010 maule chile earthquake the 2011 tohoku earthquake and the 2012 indian ocean earthquakes by using the high spherical harmonic degree up to degree 96 data products and the associated grace data processing techniques the retrieved north component of gravity change is up to 34 1 4 gal for the 2004 sumatra andaman earthquake which illustrates by far the highest amplitude of the coseismic signal retrieved from satellite gravimetry among previous studies we creatively apply the localized spectral analysis as an efficient method to empirically determine the practical spherical harmonic truncation degree by combining least squares adjustment with the simulated annealing algorithm point source parameters are estimated which demonstrates the unique constraint on source model from grace data compared to other data sources for the 2004 sumatra andaman earthquake grace data produce a shallower centroid depth 9 1 km as compared to the depth 28 3 km from gps data for the 2011 tohoku earthquake the grace estimated centroid location is southwest of the gps seismic solutions and the slip orientation is about 10 clockwise from the published gps seismic slip models we concluded that these differences demonstrate the additional and critical offshore constraint by grace on source parameters as compared to gps seismic data

unraveling climatic changes from intraprofile variation in oxygen and hydrogen isotopic composition of goethite and kaolinite in laterites an integrated study from yaou french guiana an integrated study of o and h isotopes in the lateritic profile of yaou french guiana was undertaken to investigate the usefulness of stable isotopes as tracers of climatic changes in continental environments the studied profile is composed of a 27 m thick saprolite mostly developed in the past under wet and dry tropical climate in association with a duricrust overlain by a 3 m thick yellow latosol formed more recently under present equatorial hot and humid climate 18o d values determined for weathering goethite pseudomorphs after pyrite and kaolinite microcrystalline clay groundmass throughout the 30 m deep profile reflect formation temperatures consistent with present 25 c and realistic past climatic temperatures 20 c 30 c indicating that weathering minerals formed in isotopic equilibrium with their genetic environment and were not subjected to significant isotope exchange after formation a distinct shift downward 2 for 18o 15 for d from low to high 18o d values occurs around 20 m depth in the saprolite it is interpreted as recording the change from the past tropical to the present equatorial climate goethite and kaolinite in the 5 10 m thick saprolite interval immediately above the active basement weathering front are in isotopic equilibrium with modern water and must have formed under present equatorial humid conditions in contrast goethite and kaolinite found higher up in the saprolite and in the duricrust formed in the past under tropical wet and dry climate from waters distinctly depleted in 18o and d relative to modern water the marked depletion of paleo meteoric water at yaou most likely reflects a more contrasted or monsoonal character of the ancient tropical climate the present study shows that ancient weathering minerals in lateritic profiles preserve their 18o d values and carry a time signal the time signal is best expressed in minerals formed rapidly at the weathering front and not subjected to post formational remobilization such as the goethite pseudomorphs after pyrite occurring at yaou groundmass kaolinite is more susceptible to partial remobilization through successive dissolution precipitation reactions which may obliterate the paleoclimatic signal unraveling the climatic record carried by weathering minerals in old soil systems is greatly enhanced by studying both oxygen and hydrogen isotopic compositions

late pleistocene mountain glacier response to north atlantic climate change in southwest ireland stephan harrison neil glasser ed anderson susan ivy ochs peter w kubik 2010 late pleistocene mountain glacier response to north atlantic climate change in southwest ireland quaternary science reviews 29 27 28 3948 3955

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

18o 16o and d h in goethite from a north american oxisol of the early eocene climatic optimum abstract an early eocene oxisol in the ione formation of california formed in a coastal continental weathering environment at a paleolatitude of 38 n the dominant minerals in the oxisol are goethite quartz and kaolinite material balance calculations were applied to new measurements of chemical composition d h and 18 o 16 o ratios of oxisol samples to determine the d 150 3 and 18 o 2 4 0 3 values of the goethite feooh these data in combination with the global meteoric water line mwl yielded an isotopic temperature of 21 4 c the nominal value of 21 c contrasts with the modern mean annual temperature mat of 16 c in that area the warmer temperature is consistent with formation of the goethite during the early eocene climatic optimum the isotopic composition of the goethite and a temperature of 21 c imply ancient water with a d value of 61 4 and a 18 o value of 8 9 0 5 this early eocene 18 o or d value is more negative than values in the range of isotopic scatter observed for modern global precipitation at sites with a mat of 21 c at times of warm global climates the location of a near surface atmospheric isotherm would generally shift relative to its location under modern climatic conditions a simple rayleigh type condensation model indicates that if one follows the isotherm the associated scatter in d and 18 o of precipitation in very warm global climates should shift for a given isotherm to more negative values that may be detectable in proxy records the isotopic results from the goethite of the early eocene oxisol appear to add to evidence in support of this idea

statistical significance of precursory gravity changes before the 2011 mw 9 0 tohoku oki earthquake author s wang l burgmann r abstract 2019 american geophysical union all rights reserved it is of paramount importance to independently assess the spatiotemporal uniqueness of a proposed regional precursor initiated a few months before the 2011 mw 9 0 tohoku oki earthquake the precursor has been inferred from grace derived gravitational gradient changes and has been interpreted as a large scale aseismic movement of the subducting plate along the japan trench we design a hypothesis test which enables the rigorous assessment of the statistical significance of short term gradient anomalies at any time in any place and the quantitative comparison of the resolved anomalies with the proposed precursory signal we find that the proposed precursory changes are not statistically unique either in time or in space therefore the precursor cannot be attributed to the proposed dynamic acceleration of the subduction process instead such transient features more likely represent temporally correlated grace observation errors or signals associated with other processes

contribution of satellite gravimetry to understanding seismic source processes of the 2011 tohoku oki earthquake 1 the 2011 great tohoku oki earthquake apart from shaking the ground perturbed the motions of satellites orbiting some hundreds km away above the ground such as grace due to coseismic change in the gravity field significant changes in inter satellite distance were observed after the earthquake these unconventional satellite measurements were inverted to examine the earthquake source processes from a radically different perspective that complements the analyses of seismic and geodetic ground recordings we found the average slip located up dip of the hypocenter but within the lower crust as characterized by a limited range of bulk and shear moduli the grace data constrained a group of earthquake source parameters that yield increasing dip 7 16 2 and simultaneously decreasing moment magnitude 9 17 9 02 0 04 with increasing source depth 15 24 km the grace solution includes the cumulative moment released over a month and demonstrates a unique view of the long wavelength gravimetric response to all mass redistribution processes associated with the dynamic rupture and short term postseismic mechanisms to improve our understanding of the physics of megathrusts

coseismic slip distributions of the 26 december 2004 sumatra andaman and 28 march 2005 nias earthquakes from gps static offsets static offsets produced by the 26 december 2004 m 9 sumatra andaman earthquake as measured by global positioning system gps reveal a large amount of slip along the entire 1300 km long rupture most seismic slip inversions place little slip on the andaman segment whereas both near field and far field gps offsets demand large slip on the andaman segment we compile available datasets of the static offset to render a more detailed picture of the static slip distribution we construct geodetic offsets such that postearthquake positions of continuous gps sites are reckoned to a time 1 day after the earthquake and campaign gps sites are similarly corrected for postseismic motions the newly revised slip distribution m w 9 22 reveals substantial segmentation of slip along the andaman islands with the southern quarter slipping 15 m in unison with the adjacent nicobar and northern sumatran segments of length 700 km we infer a small excess of geodetic moment relative to the seismic moment a similar compilation of gps offsets from the 28 march 2005 nias earthquake is well explained with dip slip averaging several meters mw 8 66 distributed primarily at depths greater than 20 km online material offset estimation procedure comparison of results to other stud ies and simpler solutions and tables of coseismic offsets

rock surface roughness as an indicator of degree of rock surface weathering rock surface weathering often leads to increased rock surface roughness but roughness has proved difficult to quantify several instruments are available for micro mapping and recording rock surface profiles but the most appropriate for most purposes is the simple profile gauge short profiles can be recorded quickly and accurately a range of roughness indices has been proposed in other areas of geomorphology and their efficacy as measures of roughness at scales of interest in studies of weathering is assessed some are too complex or labour intensive and others are too sensitive to the scale of roughness to provide reliable measures of magnitude the most appropriate indicator of both the scale and magnitude of roughness is the standard deviation of the differences between height values at a range of set horizontal intervals along a profile the deviogram varying the measurement interval records roughness at different scales a regression approach root mean square roughness provides a reliable measure of the magnitude of roughness at the maximum scale present three case studies confirm the efficacy of these approaches to studies of weathering of different rocks in different environments software is supplied which automates the calculation of roughness indices from gauge profiles

calculating quaternary glacial erosion rates in northeast scotland northeast scotland is an area exhibiting selective erosion by quatemary ice sheets in this area both glacial and preglacial landforms exist in close proximity the depths of erosion which this modification represents are calculated on the assumption of various depths of preglacial weathering a depth of erosion of between 34 and 62 m per unit area is indicated calculated rates of erosion are 0 021 nun a for the entire 2 3 m y of the quaternary and between 0 1 and 0 5 mm aa1 on the assumption that glacial conditions existed in this area for 500 000 years and 100 000 years respectively these figures are compared to the offshore sedimentary record in the adjacent west central north sea the volume of sediment deposited offshore is equivalent to a depth of erosion of 195 m per unit area yielding an average erosion rate of 0 085 mm a i over the entire quatemary rates of erosion were low in the preglacial pliocene 0 049 mm a 1 and early quatemary 0 063 mm a the expansion of ice sheets across the area in the middle quatematy was associated with a sharp increase in the rates of erosion 0 13 mm a but the last late devensian ice sheet in the area was less erosive 0 095 mm a the estimated rates of erosion represented by the offshore sedimentary record therefore exceed the estimated rates of glacial erosion from the onsho re geomorphological reconstruction

slow postseismic recovery of geoid depression formed by the 2004 sumatra andaman earthquake by mantle water diffusion 1 earthquakes are accompanied with mass redistributions and cause changes in gravity field and shape of geoid an equipotential surface coincident with the mean sea surface such coseismic changes were detected by satellite gravimetry after the 2004 sumatra andaman earthquake but little has been known on what happens on geoid after the earthquake here we report slow postseismic recovery of coseismic geoid depression from satellite measurements this cannot be explained with simple afterslip or viscous relaxation of maxwellian upper mantle it suggests the relaxation of coseismic dilatation and compression by the diffusion of supercritical h2o abundant in the upper mantle such a self healing system of coseismic geoid undulations a brand new role of water in mantle would significantly reduce the amount of permanent shifts of the earth s rotation axis by earthquakes

coseismic gravity changes of the 2011 tohoku oki earthquake from satellite gravimetry 1 the massive tohoku oki earthquake of a moment magnitude mw of 9 0 occurred on 11 march 2011 off the pacific coast of the northeastern japan the mass redistribution in and around the focal region associated with this earthquake was studied using the gravity changes detected by gravity recovery and climate experiment grace satellite after the 2004 sumatra andaman and the 2010 central chile maule earthquakes the present study presents the third case of clear detection of coseismic gravity changes by grace the observed gravity changes were dominated by decrease over the back arc region of 7 gal or less this reflects to a large extent coseismic crustal dilatation of the landward plate they agree well with the changes calculated with the green s function for the realistic earth using fault parameters inferred from coseismic crustal movements the spatial patterns of the gravity changes of these earthquakes are very similar because they are all shallow angle reverse faulting at convergent plate boundaries we found linear relationship between gravity decreases and seismic moments

glacial abrasion and sliding their dependence on the debris concentration in basal ice a model of bedrock abrasion by a temperate glacier is developed that takes into account the significant impeding effect of scattered rock fragments at the ice rock interface on glacier sliding an increase in the debris concentration above a relatively low value can reduce the abrasion rate by decreasing both the flux of rock fragments and the effective forces which press fragments against the bed abrasion of a simple wavy bed is shown to be most rapid for a relatively low debris concentration above which the abrasion varies inversely with the debris content a similar concentration dependence of abrasion is expected for beds of arbitrary geometry but low roughness sliding glaciers will tend to abrade until the basal ice is nearly stagnant at which point rocks of all sizes start to lodge against the bed

regional gravity decrease after the 2010 maule chile earthquake indicates large scale mass redistribution 1 we report small but detectable changes in the grace satellites relative trajectory after the m8 8 maule chile earthquake on 27 february 2010 that can be used to delineate the shift in the gravity field a gravity anomaly of 5 gal with a spatial scale of 500 km was found east of the epicenter after the earthquake based on coseismic models the long wavelength negative gravity change is primarily the result of crustal dilatation as well as surface subsidence in the onland region the offshore positive gravity anomaly predicted from finite fault coseismic models is considerably smaller because the gravity changes due to surface uplift and interior deformation are opposite in polarity our study suggests a role for large scale gravity observations in deciphering changes of the earth s interior during great earthquakes by filling in the seldom observed long wavelength spectrum of earthquake deformations as a complement to surface geodetic measurements and seismic data

insight into the 2004 sumatra andaman earthquake from gps measurements in southeast asia data collected at 60 global positioning system gps sites in southeast asia show the crustal deformation caused by the 26 december 2004 sumatra andaman earthquake at an unprecedented large scale small but significant co seismic jumps are clearly detected more than 3 000 km from the earthquake epicentre the nearest sites still more than 400 km away show displacements of 10 cm or more here we show that the rupture plane for this earthquake must have been at least 1 000 km long and that non homogeneous slip is required to fit the large displacement gradients revealed by the gps measurements our kinematic analysis of the gps recordings indicates that the centroid of released deformation is located at least 200 km north of the seismological epicentre it also provides evidence that the rupture propagated northward sufficiently fast for stations in northern thailand to have reached their final positions less than 10 min after the earthquake hence ruling out the hypothesis of a silent slow aseismic rupture data culled from gps stations in indonesia malaysia singapore thailand india and china have answered more questions relating to the 26 december sumatra andaman megathrust earthquake permanent displacements were seen 3 000 km away final displacements occurred within 10 minutes of the earthquake ruling out slow aseismic slip on the fault

genesis of hummocky moraines by thrusting in glacier ice evidence from svalbard and britain irregular mounds of glacial debris commonly referred to as 9hummocky moraine9 until recently were linked to ice stagnation during rapid climatic amelioration however recent work in scotland has demonstrated that some hummocky moraine dating from the younger dryas event c 10 000 years bp was the product of deposition at active ice margins observations at modern high arctic glacier margins in svalbard 76 80 n indicate that some moraines of this type form under a dynamic glaciological regime mainly by thrusting in active polythermal ice undergoing strong longitudinal compression this situation is particularly common where there is a transition from warm based ice in the interior of a glacier to cold based ice at the margins or snout from their morphological similarity rectilinear slopes facing up glacier and irregular downglacier faces and apparent stacking of slabs of sediment of subglacial derivation it is concluded that some assemblages of british moraines are also the product of thrusting this process appears to be most dominant in polythermal glaciers rather than in temperate glaciers on this basis it is tentatively suggested that the younger dryas in britain was characterized by a climatic regime similar to that in svalbard today mean annual temperature 5 c 400 1000 mm precipitation and that the associated glaciers may have been of polythermal character

spectral roughness of glaciated bedrock geomorphic surfaces implications for glacier sliding a microroughness meter mrm was used to measure the high frequency roughness of a number of geomorphic surfaces in the forefield of glacier de tsanfleuron switzerland resulting spectral power densities are added to low frequency spectra measured by electro optical distance meter edm to generate composite roughness spectra that include almost 5 orders of magnitude of roughness in the frequency domain these are used to define two roughness indices a general index of bed roughness is defined as the integral of the raw spectral power densities and a sliding related index of bed roughness is defined as the integral of the spectral power densities weighted to account for the optimum dependence of glacier sliding speed on hummock wavelength results indicate that mrm measured geomorphic components vary in roughness by 3 orders of magnitude principally depending on the surface microenvironment measured and profile orientation relative to the direction of former ice flow both mrm and edm measured roughnesses are lower parallel to the direction of former ice flow than perpendicular to it composite roughness spectra consequently indicate that the glacier bed is smoothed in the direction of former ice flow at all horizontal scales from 1 mm to 40 m typically resulting in an order of magnitude decrease in sliding related roughness relative to that measured perpendicular to ice flow comparison of data from two survey sites located adjacent to and 1 2 km from the current glacier margin indicates that postglacial subaerial weathering homogenizes bedrock roughness in particular reducing high frequency flow orthogonal roughness accounting for the effect of 28 ice bedrock separation over one of the profiles reduces net sliding dependent roughness by between 27 and 43 depending on the transition wave number used

palaeoglaciology of the welsh sector of the british irish ice sheet this palaeoglaciological reconstruction based on the distribution of glacial lineations interpreted from satellite imagery considers the extent thickness and dynamics of the welsh ice cap and its interaction with the british irish ice sheet two major ice flow events were identified the oldest phase of ice flow event i is characterized by ice flowing from an ice dispersal centre situated over the higher terrain in north central wales and by ice thick enough to cover the mountain summits at this time the interior of the ice cap is inferred to have been dominated by cold based ice during the growth of the welsh ice cap it became confluent with the british irish ice sheet the welsh ice cap at this time was again sufficiently thick to submerge the highest mountain summits the youngest detected phase of ice flow event ii was marked by an abrupt change in the dynamics of the welsh ice cap during event ii the welsh ice cap was drained by at least four ice streams which followed major troughs in northern and eastern wales

grace gravity data help constraining seismic models of the 2004 sumatran earthquake 1 the analysis of gravity recovery and climate experiment grace level 2 data time series from the center for space research csr and geoforschungszentrum gfz allows us to extract a new estimate of the co seismic gravity signal due to the 2004 sumatran earthquake owing to compressible self gravitating earth models including sea level feedback in a new self consistent way and designed to compute gravitational perturbations due to volume changes separately we are able to prove that the asymmetry in the co seismic gravity pattern in which the north eastern negative anomaly is twice as large as the south western positive anomaly is not due to the previously overestimated dilatation in the crust the overestimate was due to a large dilatation localized at the fault discontinuity the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust after this localized dilatation is removed we instead predict compression in the footwall and dilatation in the hanging wall the overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust as first indicated by de linage et al 2009 we also detail the differences between compressible and incompressible material properties by focusing on the most robust estimates from grace data consisting of the peak to peak gravity anomaly and an asymmetry coefficient that is given by the ratio of the negative gravity anomaly over the positive anomaly we show that they are quite sensitive to seismic source depths and dip angles this allows us to exploit space gravity data for the first time to help constraining centroid momentum tensor cmt source analyses of the 2004 sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle thus grace data and cmt source analyses as well as geodetic slip distributions aided by gps complement each other for a robust inference of the seismic source of large earthquakes particular care is devoted to the spatial filtering of the gravity anomalies estimated both from observations and models to make their comparison significant

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

coseismic and postseismic deformation of the 2011 tohoku oki earthquake constrained by grace gravimetry 1 spaceborne gravimetry data from the gravity recovery and climate experiment grace are processed using spatio spectral slepian localization analysis enabling the high resolution detection of permanent gravity change associated with both coseismic and postseismic deformation resulting from the great 11 march 2011 mw 9 0 tohoku oki earthquake the grace observations are then used in a geophysical inversion to estimate a new slip model containing both coseismic slip and after slip the grace estimated moment for the total slip up to the end of july 2011 is estimated as 4 59 0 49 1022 n m equivalent to a composite mw of 9 07 0 65 if the moment for the tohoku oki main shock is assumed to be 3 8 1022 n m the contribution from the after slip is estimated to be 3 0 1021 12 8 1021 n m in good agreement with a postseismic slip model inverted from gps data we conclude that grace data provide an independent constraint to quantify co and post seismic deformation for the tohoku oki event