itrf2014 a new release of the international terrestrial reference frame modeling nonlinear station motions for the first time in the international terrestrial reference frame itrf history the itrf2014 is generated with an enhanced modeling of nonlinear station motions including seasonal annual and semiannual signals of station positions and postseismic deformation for sites that were subject to major earthquakes using the full observation history of the four space geodetic techniques very long baseline interferometry vlbi satellite laser ranging slr global navigation satellite systems gnss and doppler orbitography and radiopositioning integrated by satellite doris the corresponding international services provided reprocessed time series weekly from slr and doris daily from gnss and 24 h session wise from vlbi of station positions and daily earth orientation parameters itrf2014 is demonstrated to be superior to past itrf releases as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities the itrf2014 long term origin coincides with the earth system center of mass as sensed by slr observations collected on the two lageos satellites over the time span between 1993 0 and 2015 0 the estimated accuracy of the itrf2014 origin as reflected by the level of agreement with the itrf2008 both origins are defined by slr is at the level of less than 3 mm at epoch 2010 0 and less than 0 2 mm yr in time evolution the itrf2014 scale is defined by the arithmetic average of the implicit scales of slr and vlbi solutions as obtained by the stacking of their respective time series the resulting scale and scale rate differences between the two solutions are 1 37 0 10 ppb at epoch 2010 0 and 0 02 0 02 ppb yr while the postseismic deformation models were estimated using gnss gps data the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques showing a very high level of consistency which enforces more the link between techniques within the itrf2014 frame the users should be aware that the postseismic deformation models are part of the itrf2014 products unlike the annual and semiannual signals which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame

a consistent sea level reconstruction and its budget on basin and global scales over 1958 2014 different sea level reconstructions show a spread in sea level rise over the last six decades and it is not yet certain whether the sum of contributors explains the reconstructed rise possible causes for this spread are among others vertical land motion at tide gauge locations and the sparse sampling of the spatially variable ocean to assess these open questions reconstructed sea level and the role of the contributors are investigated on a local basin and global scale high latitude seas are excluded tide gauge records are combined with observations of vertical land motion independent estimates of ice mass loss terrestrial water storage and barotropic atmospheric forcing in a self consistent framework to reconstruct sea level changes on basin and global scales which are compared to the estimated sum of contributing processes for the first time it is shown that for most basins the reconstructed sea level trend and acceleration can be explained by the sum of contributors as well as a large part of the decadal variability the sparsely sampled south atlantic ocean forms an exception the global mean sea level reconstruction shows a trend of 1 5 0 2 mm yr 1 over 1958 2014 1 compared to 1 3 0 1 mm yr 1 for the sum of contributors over the same period the reconstruction shows a positive acceleration of 0 07 0 02 mm yr 2 which is also in agreement with the sum of contributors which shows an acceleration of 0 07 0 01 mm yr 2 since 1993 both reconstructed sea level and the sum of contributors show good agreement with altimetry estimates

sedimentary response to intra arc extension controls on oligo miocene deposition sarcidano sub basin sardinia the oligo miocene sardinian rift is a rare example of a well exposed intra arc basin comprising several independent depocentres synthesis of field observations from one such depocentre the sarcidano sub basin in central sardinia not only allows a new and integrated sedimentological and tectonostratigraphic history for the area but also provides insights into controls on syn and post rift sedimentation in intra arc settings initial rifting during the late rupelian early chattian oligocene occurred on nw se trending normal faults and produced a half graben topography which controlled the dispersal of locally supplied coarse continental clastic sediments latest chattian aquitanian miocene ne sw trending normal faulting defined a more complex block topography that remained underfilled in all areas except those which received voluminous ignimbritic volcanic material subsequent marginal and shallow marine sedimentation progressively infilled the fault topography as sea level rose deposition of coarse clastic sediments eroded from fault scarps was focused in the hanging wall depocentres of the intersecting fault trends whilst platform carbonates became established in topographically higher areas protected from clastic sedimentary supply finally as the relative rise in sea level drowned sediment source areas in the burdigalian deeper marine marlstones dominated sedimentation the results demonstrate that the sarcidano sub basin was dominated by a mixed volcanic siliciclastic carbonate basin fill with abrupt facies changes developed in response to complex fault defined topography relative rise in sea level and an episodic volcanic supply whilst the rift structure largely controlled the provenance supply and accumulation of sediments relative sea level primarily controlled the types of facies that developed

the tectonic development of the western margin of the gulf of elat aqaba rift abstract along the western coast of the gulf of elat a 30 km wide shear belt of subparallel faults trending n s to ne sw is developed this shear belt is observed mainly within the precambrian basement terrain sinistral movements on these faults have been recognized based on offsets of magmatic bodies and lithological contacts in rocks of precambrian age the cumulative displacement measured independently at several localities across the belt attains a total of 24 km early neogene volcanism in the form of long dikes trending nw se is known from the eastern desert of egypt of the gulf of suez and along the red sea coast of saudi arabia volcanic bodies of a similar pattern have been identified in eastern sinai these bodies mainly dolerites and basalts intruding mesozoic sediments are parallel to each other and to the gulf of suez they are tens to hundreds of kilometers long and spaced several tens of kilometers apart dating k ar of bodies in sinai saudi arabia and in the eastern desert of egypt suggest an age of 20 22 m y for this extensive volcanism all the dikes are sinistrally displaced by the individual faults of the eastern sinai shear belt the amount of movement recorded using the precambrian markers is identical to movement recorded by offsets of the early neogene dikes this proves that the total 24 km shear of this fault system postdates the 20 22 m y volcanic phase it is assumed that the recorded movements are part of the 105 110 km shear persumed to exist along the gulf of elat which is also younger than 20 22 m y preliminary results suggest that a similar amount of movement is observable along a shear zone developed on the eastern coast of the gulf of elat thus only some 60 km movement are taken up by faults in the gulf itself the evolving model suggests that 1 a the intrusion of very long basaltic dikes in a nw se direction on both sides of the red sea accompanied the initial stage of development of the red sea gulf of suez rift valley 2 b a basic change in the geotectonic regime occurs after the intrusion of this volcanic suite large scale horizontal movements are initiated being recorded as a 105 110 km sinistral movement along the arava jordan rift this movement implies a synchronous opening of the red sea

ocean bottom deformation due to present day mass redistribution and its impact on sea level observations present day mass redistribution increases the total ocean mass and on average causes the ocean bottom to subside elastically therefore barystatic sea level rise is larger than the resulting global mean geocentric sea level rise observed by satellite altimetry and gps corrected tide gauges we use realistic estimates of mass redistribution from ice mass loss and land water storage to quantify the resulting ocean bottom deformation and its e ect on global and regional ocean volume change estimates over 1993 2014 the resulting globally averaged geocentric sea level change is 8 percent smaller than the barystatic contribution over the altimetry domain the di erence is about 5 percent and due to this e ect barystatic sea level rise will be underestimated by more than 0 1 mm y over 1993 2014 regional di erences are of ten larger up to 1 mm y over the arctic ocean and 0 4 mm y in the south paci c ocean bottom deformation should be considered when regional sea level changes are observed in a geocentric reference frame

bias in estimates of global mean sea level change inferred from satellite altimetry abstractestimates of regional and global average sea level change remain a focus of climate change research one complication in obtaining coherent estimates is that geodetic datasets measure different aspects of the sea level field satellite altimetry constrains changes in the sea surface height ssh or absolute sea level whereas tide gauge data provide a measure of changes in ssh relative to the crust i e relative sea level the latter is a direct measure of changes in ocean volume and the combined impacts of ice sheet melt and steric effects but the former is not since it does not account for crustal deformation nevertheless the literature commonly conflates the two estimates by directly comparing them we demonstrate that using satellite altimetry records to estimate global ocean volume changes can lead to biases that can exceed 15 the level of bias will depend on the relative contributions to sea level changes from the antarctic and greenland ice sheets the bias is also more sensitive

twentieth century global mean sea level rise is the whole greater than the sum of the parts confidence in projections of global mean sea level rise gmslr depends on an ability to account for gmslr during the twentieth century there are contributions from ocean thermal expansion mass loss from glaciers and ice sheets groundwater extraction and reservoir impoundment progress has been made toward solving the enigma of twentieth century gmslr which is that the observed gmslr has previously been found to exceed the sum of estimated contributions especially for the earlier decades the authors propose the following thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century the greenland ice sheet could have made a positive contribution throughout the century and groundwater depletion and reservoir impoundment which are of opposite sign may have been approximately equal in magnitude it is possible to reconstruct the time series of gmslr from the quantified contributions apart from a constant residual term which is small enough to be explained as a long term contribution from the antarctic ice sheet the reconstructions account for the observation that the rate of gmslr was not much larger during the last 50 years than during the twentieth century as a whole despite the increasing anthropogenic forcing semiempirical methods for projecting gmslr depend on the existence of a relationship between global climate change and the rate of gmslr but the implication of the authors closure of the budget is that such a relationship is weak or absent during the twentieth century

geodetic vertical velocities affected by recent rapid changes in polar motion summary secular motion of earth s rotation pole results in large scale secular deformation of earth here we investigate the magnitude of the deformation that has resulted from the rapid motion of the rotation pole to the east since 2005 we show that geodetic gnss doris vlbi and slr estimates of vertical velocity since 2005 have been biased by up to 0 38 mm yr 1 relative to the longer term deformation pattern the largest signals occur within regions that include the u s pacific coast europe and south pacific islands where geodetic measurements provide essential measurements of tide gauge vertical movement and important constraints on models of glacial isostatic adjustment consequently geodetic vertical velocities based on recent data should not be interpreted as being identical to centennial or longer term vertical land movement since 2010 the effect is further amplified by the overprediction of the iers polar motion model relative to the ongoing secular change in pole position during this time geodetic vertical velocities based on the iers pole tide model are not just biased relative to the long termratesbutalsofromactualpost 2010earthdeformation forgeophysicalorreference frame studies seeking geodetic vertical velocities that are representative of decadal timescales where interannual variation is considered noise the correction for this non linear effect is straightforward requiring an elastic computation using a reference rate of polar motion that is linear over the timescales of interest

lower miocene nukhul formation gebel el zeit egypt model for structural control on early synrift strata and reservoirs gulf of suez the aquitanian early burdigalian lower miocene nukhul formation at gebel el zeit egypt was deposited during early stages of gulf of suez rifting the unit dips 8 15 less than underlying prerift strata indicating that significant rotation and extension preceded subsidence of the gebel el zeit fault block the nukhul formation at gebel el zeit is up to 75 m thick in outcrop and consists of a lower sandstone and an upper carbonate unit the formation varies considerably along strike because of syndepositional differential movement of small fault bounded blocks the lower clastic unit at south gebel el zeit contains poorly sorted conglomeratic marly sandstone that commonly displays grading and bouma sequences beds were deposited below storm base by sediment gravity flows thicker intervals are inferred to fill small structurally controlled submarine gullies that funneled sand and gravel southwestward to a half graben basin in contrast an inferred correlative thin basal conglomeratic unit in north gebel el zeit was deposited in a shallow marine setting the presence of basement clasts in nukhul strata indicates early syndepositional uplift due to structural tilting the upper carbonate unit consists of bioclast peloid and intraclast packstone wackestone and grainstone with minor floatstone rudstone and coral algal boundstone carbonate strata were deposited variously in deep marine low energy peritidal and subtidal and reefal environments deeper submerged blocks were the site of carbonate resedimentation or deeper shelf deposition reefs and shallow marine bioclast shoals formed on higher submerged blocks nukhul strata show that synrift reservoir prediction in the gulf of suez the red sea and presumably in other rifts requires mapping of synrift cross faults and fault block by fault block facies analysis robert winn is a consulting geologist he received a ph d from the university of wisconsin madison in 1975 and joined marathon oil company as a research geologist in 1977 he left marathon in 1994 for the university of papua new guinea where he was senior lecturer and then associate professor he was head of the geology department from 1996 to 2000 his primary interests are in clastic sedimentology and sequence stratigraphy paul crevello is a consulting geologist and technical director of petrexasia which he formed in 1997 he received an m s degree from the university of miami 1978 and a ph d from colorado school of mines 1989 he was employed by marathon oil as a research geologist from 1978 to 1994 and by the university of brunei as senior lecturer from 1994 to 1997 his specialties are in sequence stratigraphy and sedimentology of carbonate and turbidite systems and the integrated calibration of 3 d reservoir models william bosworth is employed by marathon oil company he joined marathon in 1984 and has worked principally on international exploration and development projects from 1980 to 1984 he taught structural geology and tectonics at colgate university in hamilton new york his research interests are principally in extensional tectonics continental stress field evolution and the paleogeodynamics of the african plate

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

ongoing glacial isostatic contributions to observations of sea level change studies determining the contribution of water fluxes to sea level rise typically remove the ongoing effects of glacial isostatic adjustment gia unfortunately use of inconsistent terminology between various disciplines has caused confusion as to how contributions from gia should be removed from altimetry and grace measurements in this paper we review the physics of the gia corrections applicable to these measurements and discuss the differing nomenclature between the gia literature and other studies of sea level change we then examine a range of estimates for the gia contribution derived by varying the earth and ice models employed in the prediction we find similar to early studies that gia produces a small compared to the observed value but systematic contribution to the altimetry estimates with a maximum range of 0 15 to 0 5 mm yr 1 moreover we also find that the gia contribution to the mass change measured by grace over the ocean is significant in this regard we demonstrate that confusion in nomenclature between the terms absolute sea level and geoid has led to an overestimation of this contribution in some previous studies a component of this overestimation is the incorrect inclusion of the direct effect of the contemporaneous perturbations of the rotation vector which leads to a factor of two larger value of the degree two order one spherical harmonic component of the model results aside from this confusion uncertainties in earth model structure and ice sheet history yield a spread of up to 1 4 mm yr 1 in the estimates of this contribution however even if the ice and earth models were perfectly known the processing techniques used in grace data analysis can introduce variations of up to 0 4 mm yr 1 thus we conclude that a single valued gia correction is not appropriate for sea level studies based on gravity data each study must estimate a bound on the gia correction consistent with the adopted data analysis scheme

dips of normal faults in british coal measures and other sedimentary sequences fault dip measurements n 3291 from 122 faults in british coalfields are presented two classes of normal fault are recognized a gently dipping 55 post coalification tectonic faults formed at depths of about 2 5 km which comprise 90 of the faults analysed dip data from the steeply dipping faults are variable standard deviation 9 both on single faults and between faults and 70 is a better approximation of fault dip than the commonly accepted value of 60 data on tectonic normal faults with comparable depths of formation using the modified griffith fracture criterion the dips of faults at varying depths up to 4 km are calculated for both unsaturated dry and saturated rocks the dips of normal faults are expected to vary from 90 at the surface to 60 at 3 4 km and this variation is consistent with the limited field data available the coalfield data are consistent with fault formation at standard hydrostatic pore fluid pressures at depths of about 2 5 km below depths of a few kilometres normal faults are expected to flatten out gradually to a dip of 45 but such flattening is not necessarily an indication of an underlying detachment

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction

mechanical response to stratigraphic inhomogeneity during extension and surface expression of buried structures gulf of suez egypt abstract mechanical response of the stratigraphic succession to rifting in the gulf of suez egypt varies depending on the degree of competence of the rock units this mechanical stratigraphy has been documented by observational evidence from field surveys in the northern esh el mallaha and in the ras issaran area in conjunction with seismic reflection data complex response patterns to basement rooted block faulting is seen on several scales in both the prerift and synrift rocks the prerift section is divided into three major units based on mechanical response precambrian basement pre cenomanian nubian sandstone and cenomanian through eocene stable platform marine rocks brittle faulting in the basement propagates into the nubian sandstone by densely fracturing the latter parallel to the fault planes the overlying inhomogeneous cenomanian eocene section drapes and folds over underlying structural elements these rocks contain complicated structures due to the interlayering of thin brittle and ductile beds the incompetent units allow bedding parallel detachment and also flow into voids created during faulting or folding of the competent units the synrift section comprises three major stratigraphic units each of which reacts differently to block faulting these are the early miocene carbonate clastic section the middle late miocene evaporite section and the onshore pliocene recent clastic passive cover sequence in general the lower synrift rocks respond to deformation much like the cenomanian eocene units draping and folding due to interlayered brittle and ductile beds seismic reflection data indicate that the evaporite section is a major detachment zone with faults in underlying units dying out upwards as the ductile salts or anhydrites drape and flow structural response in this section is varied and complex the deformation of the evaporites breaks the overlying passive cover rocks with faults in the latter soling into the underlying ductile strate on gravel plains flanking the gulf of suez the neotectonic fault pattern and resulting topographic and drainage changes reflect underlying structures the faults breaking the passive cover sequence at the surface initially form en echelon traces with continued movement these coalesce into straight or curved often splaying fault traces where the evaporite section reaches a significant thickness the structures seen at the surface may be entirely decoupled from those of the prerift and early synrift sequences

recent global sea level acceleration started over 200 years ago 1 we present a reconstruction of global sea level gsl since 1700 calculated from tide gauge records and analyse the evolution of global sea level acceleration during the past 300 years we provide observational evidence that sea level acceleration up to the present has been about 0 01 mm yr2 and appears to have started at the end of the 18th century sea level rose by 6 cm during the 19th century and 19 cm in the 20th century superimposed on the long term acceleration are quasi periodic fluctuations with a period of about 60 years if the conditions that established the acceleration continue then sea level will rise 34 cm over the 21st century long time constants in oceanic heat content and increased ice sheet melting imply that the latest intergovernmental panel on climate change ipcc estimates of sea level are probably too low

the pole tide and its effect on grace time variable gravity measurements implications for estimates of surface mass variations gravity recovery and climate experiment grace provides monthly solutions for the earth s gravity field in the form of spherical harmonic coefficients these can be used to infer changes in mass at the earth s surface the pole tide the response of the earth and oceans to polar motion causes gravity signals dominated by harmonics of degree 2 order 1 if the pole tide is not removed from grace data it affects the coefficients of those harmonics c21 s21 and introduces errors when using those coefficients to determine surface mass variations the pole tide is partially removed by grace processing centers before solving for the gravity field but long period pole tide signals are not usually included in the grace pole tide correction and so those signals are still present in the grace coefficients we discuss this issue from the standpoint of somebody who uses the grace gravity fields to infer changes in surface mass we arrive at a recommendation for an optimal grace pole tide correction we describe how to modify the c21 s21 coefficients provided by the processing centers so that they conform with our recommendation we discuss the size of the pole tide contributions to c21 s21 compared to those of the direct load induced contributions as an example we show how an incompletely removed pole tide can impact grace results for the trend in ocean mass we consider the impact of mantle anelasticity on long period pole tide corrections and conclude that it is unlikely to affect those corrections by more than 20

tectonic analysis of the dead sea rift region since the late cretaceous based on mesostructures we have measured the orientations of small faults slickensides tectonic stylolites vein with secondary mineralization small folds and dikes in israel and sinai these structures are indicators of paleo stress or strain and provide the pattern of tectonic deformation data were collected at 130 stations most with tens of separate measurements most stations showed consistent deformation stations were located on exposures ranging from precambrian crystalline rocks to pleistocene sediments we have defined two tectonic stress fields each relatively uniform in both time and space one stress field with dominating maximum horizontal compression trending w to wnw in the late cretaceous to eocene rocks in the folds and plateaus west of the dead sea rift the second field with dominating horizontal extension trending e to ene in all rocks inside the rift and proximal thereto the first stress field is called the syrian arc stress and the second is called the dead sea stress a change in style of tectonic deformation which corresponds to the two stress fields is manifested also in the major structures in israel the late cretaceous to neogene deformation is characterized by long wavelength folds and monoclines whereas the neogene to recent deformation is characterized by normal and strike slip faults and volcanic activity

frictional properties of low angle normal fault gouges and implications for low angle normal fault slip abstract the mechanics of slip on low angle normal faults lanfs remain an enduring problem in structural geology and fault mechanics in most cases new faults should form rather than having slip occur on lanfs assuming values of fault friction consistent with byerlee s law we present results of laboratory measurements on the frictional properties of natural clay rich gouges from low angle normal faults lanf in the american cordillera from the whipple mts detachment the panamint range front detachment and the waterman hills detachment these clay rich gouges are dominated by neoformed clay minerals and are an integral part of fault zones in many lanfs yet their frictional properties under in situ conditions remain relatively unknown we conducted measurements under saturated and controlled pore pressure conditions at effective normal stresses ranging from 20 to 60 mpa corresponding to depths of 0 9 2 9 km on both powdered and intact wafers of fault rock for the whipple mountains detachment friction coefficient varies depending on clast content with values ranging from 0 40 to 0 58 for clast rich material and 0 29 0 30 for clay rich gouge samples from the panamint range front detachment were clay rich and exhibit friction values of 0 28 to 0 38 significantly lower than reported from previous studies on fault gouges tested under room humidity nominally dry conditions including samples from the same exposure samples from the waterman hills detachment are slightly stronger with ranging from 0 38 to 0 43 the neoformed gouge materials from all three localities exhibits velocity strengthening frictional behavior under almost all of the experimental conditions we explored with values of the friction rate parameter a b ranging from 0 001 to 0 025 clast rich samples exhibited frictional healing strength increases with hold time whereas clay rich samples do not our results indicate that where clay rich neoformed gouges are present along lanfs they provide a mechanically viable explanation for slip on faults with dips p f 3 overpressures and or correcting for 5 of footwall tilting furthermore the low rates of frictional strength recovery and velocity strengthening frictional behavior we observe provide an explanation for the lack of observed seismicity on these structures we suggest that lanfs in the upper crust depth

ocean mass from grace and glacial isostatic adjustment 1 we examine geoid rates and ocean mass corrections from two published global glacial isostatic adjustment gia models both of which have been used in previous studies to estimate ocean mass trends from gravity recovery and climate experiment grace satellite gravity data these two models are different implementations of the same ice loading history and use similar mantle viscosity profiles the model results are compared with each other and with geoid rates determined from grace during august 2002 to november 2009 when averaged over the global ocean the two models have rates that differ by nearly 1 mm yr 1 of ocean mass with the first model giving a correction closer to 2 mm yr 1 and the second closer to 1 mm yr 1 by comparing the two models we have discovered that 50 of the difference is caused by a global land ocean mean in the first model while it is appropriate to include this mean when subtracting gia effects from measurements of sea level change measured by tide gauges or satellite altimetry the mean should not be included when subtracting gia effects from ocean mass variations derived from satellite gravity data when this mean is removed the ocean mass corrections from the two models still disagree by 0 4 mm yr 1 we trace the residual difference to the fact that the first model also has large trends over the ocean related to large rates in its predicted degree 2 order 1 geoid coefficients such oceanic trends are not observed by grace nor are they predicted by the second model and they are shown to be inconsistent with the polar wander rates predicted by the first model itself if these two problems are corrected we find that the two model predictions agree at the 3 level on the basis of this analysis we conclude that the ocean mass correction for grace is closer to 1 mm yr 1 than 2 mm yr 1 although significant uncertainties remain

the effect of spatially non uniform water loads on prediction of sea level change summary numerical modelling of postglacial rebound predics a spatially variable pattern of sea level change yet many previous models predicting late pleistocene sea level change either neglect the load of water added to the oceans or assume a spatially uniform time dependent load over the whole ocean this is a poor approximation of the load near the former ice sheet since sea level change varies geographically in addition the coastline goemetry changes through time a spectral technique has been used to solve the sea level equation on an earth model with axisymmetric distribution of ice and oceans and also for a realistic ice ocean configuration the axisymmetric model is useful for demonstrating the fundamental physics involved in sea level changes caused by changes in surface loads in particular it can be seen that the elastic and gravitational response to the load is spread over a great distance whereas the viscous response is more localized a realistic ice ocean configuration has been used to demonstrate that neglect of the melt water load underestimates the amount of uplift in fennoscandia and other regions where rebound occurs in the ocean as previously noted by wu peltier 1983 in hudson bay and that movement of the coastlines and spatially varying water loads must both be included in calculations for the north sea and other near field regions with shallow seas sea level calculations including these effects and careful analysis of the sea level and ice melting record are required to determine modifications to the viscosity profile and ice model inferred by previous inaccurate models of the ocean load in the near field

accelerated west antarctic ice mass loss continues to outpace east antarctic gains a b s t r a c t article history while multiple data sources have confirmed that antarctica is losing ice at an accelerating rate different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy spatio temporal resolution and coverage some scope remains for methodological improvements using a single data type in this study we report our progress in increasing the accuracy and spatial resolution of time variable gravimetry from the gravity recovery and climate experiment grace we determine the geographic pattern of ice mass change in antarctica between january 2003 and june 2014 accounting for glacio isostatic adjustment gia using the ij05 r2 model expressing the unknown signal in a sparse slepian basis constructed by optimization to prevent leakage out of the regions of interest we use robust signal processing and statistical estimation methods applying those to the latest time series of monthly grace solutions we map antarctica s mass loss in space and time as well as can be recovered from satellite gravity alone ignoring gia model uncertainty over the period 2003 2014 west antarctica has been losing ice mass at a rate of 121 8g t yr and has experienced large acceleration of ice mass losses along the amundsen sea coast of 18 5g t yr 2 doubling the mass loss rate in the past six years the antarctic peninsula shows slightly accelerating ice mass loss with larger accelerated losses in the southern half of the peninsula ice mass gains due to snowfall in dronning maud land have continued to add about half the amount of west antarctica s loss back onto the continent over the last decade we estimate the overall mass losses from antarctica since january 2003 at 92 10 gt yr

glacial isostatic adjustment and the anomalous tide gauge record of eastern north america sea level variations as recorded by the global network of tide gauges represent a rich data set for studying a wide range of natural and anthropogenic phenomena such as the sea level rise induced by possible global warming for this purpose long term sea level trends must be corrected for the contaminating effects of continuing glacial isostatic adjustment1 5 gia the numerical correction procedure has for sites on the east coast of north america yielded a set of highly anomalous sea level rates characterized by systematic geographical trends2 4 5 we demonstrate that these trends are a consequence of inadequacies in the previous standard numerical prediction for gia in particular we find that the well known trends in the gia corrected tide gauge rates are eliminated if the lower mantle viscosity of the earth model used in the gia prediction is increased this result obviates the need to explain the anomalous trend as a manifestation of gulf stream ocean circulation4 or neotectonic processes2

recent relative sea level trends an attempt to quantify the forcing factors local sea level is affected by a number of forcing factors which all contribute to the trends observed by tide gauges here we use the fingerprints of main factors contributing to secular sea level trends to construct an initial empirical model that explains best the trends in sea level as recorded by the large number of coastal tide gauges over the last 50 years the forcing factors considered include steric changes derived from observations post glacial rebound as predicted by geophysical models and mass changes in the greenland and antarctic ice sheets as predicted by the static sea level equation the approximation of the observed spatial pattern of sea level trends through a model based on the spatial fingerprints of the main forcing factors fully utilizes the information contents of the available observations and models and allows the interpolation of the sealevel trends between the tide gauges as a result we obtain the global picture of sea level trends due to the forcing factors accounted for in the analysis moreover we derive constraints on the mass changes of the large ice sheets the empirical models explain about 15 of the variance of the sea level trends nevertheless the models are correlated with the observations on the level of 0 38g0 07 indicating that most of the unexplained variance is due to contributions with small spatial scales averaged over the last five decades the results indicate that the antarctic and greenland ice sheets have been melting with an equivalent contribution to global sea level rise of 0 39g0 11 and 0 10g0 05 mm yr k1 respectively the steric signal derived from observations is clearly identified in the sea level trends and is found to be at a minimum of 0 2 mm yr k1 with the most likely value being close to 0 35 mm yr k1 the global tide gauge network which covers only a small fraction of the ocean surface appears to sense an average sea level rise larger than the global average extrapolating the regression models to the global ocean and taking into account the uncertainties in the extrapolation results in a most likely global average of the order of 1 05g0 75 mm yr k1

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

regional sea level change in response to ice mass loss in greenland the west antarctic and alaska besides the warming of the ocean sea level is mainly rising due to land ice mass loss of the major ice sheets in greenland the west antarctic and the alaskan glaciers however it is not clear yet how these land ice mass losses in uence regional sea level here we use the global finite element sea ice ocean model fesom to simulate sea surface height ssh changes caused by these ice mass losses and combine it with the passive ocean response to varying surface loading using the sea level equation we prescribe rates of fresh water in ow not only around greenland but also around the west antarctic ice sheet and the mountain glaciers in alaska with approximately present day amplitudes of 200 100 and 50 gt yr respectively perturbations in sea level and in freshwater distribution with respect to a reference simulation are computed for each source separately and in their combination the ocean mass change shows an almost globally uniform behavior in the north atlantic and arctic ocean mass is redistributed toward coastal regions steric sea level change varies locally in the order of several centimeters on advective time scales of decades steric effects to local sea level differ signi cantly in different coastal locations e g at north american coastal regions the steric effects may have the same order of magnitude as the mass driven effect whereas at the european coast steric effects remain small during the simulation period

tension fractures and extensional tectonics a characteristic pattern of normal faults that we have studied in several regions illustrates successive geometries relating to increasing amounts of extension from 10 50 gulf of suez egypt to 50 100 western gulf of california mexico up to 200 southern basin and range usa tension fractures formed at an early stage of extension have an essential role the resulting structure is described as a multiple tilted packs of cards model in which rotational deformation within the major blocks is accommodated by normal faulting on previously formed tension fractures thus defining smaller blocks of second and third generation

postglacial sea level change on a rotating earth first results from a gravitationally self consistent sea level equation we present and solve a gravitationally self consistent sea level equation which governs postglacial sea level variations on a spherically symmetric self gravitating viscoelastic and rotating earth we find that the inclusion of a glacio isostatically induced rotational excitation can significantly affect previous predictions of both present day sea level rates and postglacial sea level histories which were based on a theory that assumed a non rotating earth model to illustrate we consider present day sea level rates and tide gauge corrections along the us east coast and relative sea level curves in the far field of the late pleistocene ice sheets

spatial variations in the rate of sea level rise caused by the present day melting of glaciers and ice sheets the redistribution of surface water mass associated with the melting of glacial ice causes uplift near areas of mass depletion depression of the seafloors and changes in the earth s gravitational field which perturb the ocean surface as a result local spatial variations exist in the rate of sea level rise tide gauges on continental coastlines measure a sea level rise 5 smaller than the global average tide gauges in the hemisphere opposite a source of continental mass depletion measure sea level rise 10 to 20 greater than the global average produced by that source while satellites make measurements 10 too low because most long duration tide gauges are in the northern hemisphere if the sources of sea level rise are unbalanced between the two hemispheres estimates of global sea level rise could be in error by 10 to 20 individual tide gauges could be more seriously unrepresentative if they are near regions of significant present day mass depletion

extension and rifting the zeit region gulf of suez abstract a field analysis of faults and fractures in the ras gharib ras gemsa region of the gulf of suez shows that the main late cenozoic extension occurred perpendicular to the rift axis three main types of dip slip normal faults successively developed as the tilt of blocks bounded by antithetic normal faults increased determinations of the amount of extension from structural data are compatible with estimates made using subsidence data through a simplified model of lithospheric stretching the uplift of rift shoulders is related in chronology and volume to the subsidence of the rift the geometry of fault patterns and directions of extension suggests that the late cenozoic total movement corresponds to a counterclockwise rotation of 4 5 of sinai relative to africa with a pole close to cairo