present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

constraints from gps measurements on the dynamics of the zone of convergence between arabia and eurasia we investigate the dynamics of deformation in the zone of convergence between the arabian and eurasian plates using a physical model that treats the lithosphere as a thin fluid sheet deforming in response to lateral variations in gravitational potential energy gpe this model has two free material parameters the power law exponent n of the vertically averaged rheology of the lithosphere and the argand number ar which expresses the relative importance of gpe and stresses required to deform the lithosphere with boundary conditions described by three free parameters the model fits the observed deformation as measured by 367 gps velocities with a root mean square residual of 2 4 mm yr we find negligible improvement when variations in material properties are introduced that represent increases or decreases in the lithospheric strength of the central iranian and turkish iranian plateaux and the zagros mountains effective viscosity of the lithosphere ranges from 5 1022 pa s at 10 nanostrain yr to 1022 pa s at 100 nanostrain yr as well as matching the decadal timescale predominantly interseismic strain rates determined from gps the computed distribution of strain rates is also consistent with the distribution and types of earthquake focal mechanism significant historical earthquake activity is seen in regions with strain rates lower than 20 nanostrain yr implying that it is prudent to base assessments of seismic hazard on regional strain rates

the karoo igneous province a problem area for inferring tectonic setting from basalt geochemistry tholeiitic basalts and associated intrusives are the major component of the karoo igneous province they are of mesozoic age and constitute one of the world s classic continental flood basalt cfb provinces it has been argued that most karoo basalts have not undergone significant contamination with continental crust and that their lithospheric mantle source areas were enriched in incompatible minor and trace elements during the proterozoic the only exceptions to this are late stage morb like dolerites near the present day continental margins which are considered to be of asthenospheric origin when data for the southern karoo basalts are plotted on many of the geochemical discriminant diagrams which have been used to infer tectonic setting essentially all of them would be classified as calc alkali basalts cab s or low k tholeiites virtually none of them plot in the compositional fields designated as characteristic of within plate basalts there is little likelihood that the compositions of the karoo basalts can be controlled by active subduction at the time of their eruption and no convincing evidence that a subduction component has been added to the subcontinental lithospheric mantle under the entire area in which the basalts crop out it must be concluded that the mantle source areas for cab s and the southern karoo basalts have marked similarities in contrast the data for northern karoo basalts largely plot in the within plate field on geochemical discriminant diagrams available data suggest that the source composition and or the restite mineralogy and degree of partial melting are different for southern and northern karoo basalts there is no evidence for any difference in tectonic setting between the southern and northern karoo basalts at the time they were erupted this appears to be clear evidence that specific mantle source characteristics and or magmatic processes can vary within a single cfb province to an extent that renders at least some geochemical discriminant diagrams most unreliable for classifying tectonic environment with respect to continental volcanic rocks

shallow creep along the 1999 izmit earthquake rupture turkey from gps and high temporal resolution interferometric synthetic aperture radar data 2011 2017 characterizing the spatiotemporal evolution of creep is essential to constrain fault slip budget and understand creep mechanism studies based on interferometric synthetic aperture radar and global positioning system gps satellite observations until 2012 have shown that the central segment of the 17 august 1999 mw 7 4 izmit earthquake on the north anatolian fault began slipping aseismically following the event in the present study we combine new interferometric synthetic aperture radar time series based on terrasar x and sentinel 1a b radar images acquired over the period 2011 2017 with near field gps measurement campaigns performed every 6 months from 2014 to 2016 the mean velocity fields reveal that creep on the central segment of the 1999 izmit fault rupture continues to decay more than 19 years after the earthquake in overall agreement with models of postseismic afterslip decaying logarithmically with time for a long period of time along the fault section that experienced supershear velocity rupture during the izmit earthquake creep continues with a rate up to 8 mm year a significant transient accelerating creep is detected in december 2016 on the sentinel 1 time series near the maximum creep rate location associated with a total surface slip of 10 mm released in 1 month only additional analyses of the vertical velocity fields show a persistent subsidence on the hanging wall block of the golcuk normal fault that also ruptured during the izmit earthquake our results demonstrate that afterslip processes along the north anatolian fault east southeast of istanbul are more complex than previously proposed as they vary spatiotemporally along the fault

potential for larger earthquakes in the east san francisco bay area due to the direct connection between the hayward and calaveras faults the hayward and calaveras faults two strike slip faults of the san andreas system located in the east san francisco bay area are commonly considered independent structures for seismic hazard assessment we use interferometric synthetic aperture radar to show that surface creep on the hayward fault continues 15 km farther south than previously known revealing new potential for rupture and damage south of fremont the extended trace of the hayward fault also illuminated by shallow repeating micro earthquakes documents a surface connection with the calaveras fault at depths greater than 3 5 km repeating micro earthquakes located 10 km north of the surface connection highlight the 3 d wedge geometry of the junction our new model of the hayward and calaveras faults argues that they should be treated as a single system with potential for earthquake ruptures generating events with magnitudes greater than 7 posing a higher seismic hazard to the east san francisco bay area than previously considered

evolution of the northern belt southern uplands implications for the southern uplands controversy conodont and graptolite dating provide a high resolution biostratigraphical framework for correlation across the southern upland fault the establishment of an early caradoc age for the red chert and volcanic sequences within the northern belt of the southern uplands confounds the accretionary prism model and our data support the view that following the obduction of the ballantrae ophiolite fan complexes prograded southeastwards across a narrow fault bounded shelf into the deep basin of the northern belt the fan complexes were initiated by uplift in the hinterland caused by the intrusion of plutons into the midland valley terrane sedimentation was controlled by regional extension subsidence and eustasy through the llanvirn and caradoc basic lavas with attenuated within plate geochemical signatures were erupted during the early caradoc peak of extension and may have just post dated the initiation of southwards subduction beneath the lake district

interseismic deformation and creep along the central section of the north anatolian fault turkey insar observations and implications for rate and state friction properties 1 we present high resolution measurements of interseismic deformation along the central section of the north anatolian fault naf in turkey using interferometric synthetic aperture radar data from the advanced land observing satellite and envisat missions we generated maps of satellite line of sight velocity using five ascending advanced land observing satellite tracks and one descending envisat track covering the naf between 31 2 e and 34 3 e the line of sight velocity reveals discontinuities of up to 5 mm yr across the ismetpasa segment of the naf implying surface creep at a rate of 9 mm yr this is a large fraction of the inferred slip rate of the naf 21 25 mm yr the lateral extent of significant surface creep is about 75 km we model the inferred surface velocity and shallow fault creep using numerical simulations of spontaneous earthquake sequences that incorporate laboratory derived rate and state friction our results indicate that frictional behavior in the ismetpasa segment is velocity strengthening at shallow depths and transitions to velocity weakening at a depth of 3 6 km the inferred depth extent of shallow fault creep is 5 5 7 km suggesting that the deeper locked portion of the partially creeping segment is characterized by a higher stressing rate smaller events and shorter recurrence interval we also reproduce surface velocity in a locked segment of the naf by fault models with velocity weakening conditions at shallow depth our results imply that frictional behavior in a shallow portion of major active faults with little or no shallow creep is mostly velocity weakening

the pipestone pond complex central newfoundland complex magmatism in an eastern dunnage zone ophiolite ophiolitic rocks are preserved in both the notre dame and exploits subzones in the dunnage zone of the newfoundland appalachians ophiolites in the exploits subzone are generally less well preserved and exposed than their notre dame subzone counterparts and consequently have received less attention in the literature the pipestone pond complex is an exploits subzone ophiolitic sequence which outcrops on the western side of a structural window through the exploits subzone into the underlying gander zone it includes a basal harzburgite which passes upwards into a cumulate pyroxenite and gabbro sequence and thence into isotropic gabbro intruded by pegmatitic gabbro diabase and plagiogranite there is no sheeted dyke unit pillow lava occurs at the top of the sequence but is not observed to be in stratigraphic contact with the intrusive rocks the ophiolitic rocks are structurally disrupted and no single cross section traverses the complete ophiolitic stratigraphy although the stratigraphic sequence of

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

tidal forcing of basal seismicity of ice stream c west antarctica observed far inland the seismicity rate beneath the downglacier 85 km of ice stream c west antarctica is modulated by the tide the tide beneath the ross ice shelf modifies the force balance of the ice stream basal environment enough to change the rate of basal microearthquake generation by an order of magnitude this tidal forcing travels up the ice stream as an attenuating wave at approximately 1 6m s 1 and is detectable 85km from the grounding line we successfully model this behavior as an elastic ice stream underlain by a viscous substrate of viscosity and thickness hb and calculate that the substrate has an apparent stiffness hb of o 108 pa s m 1 this finding suggests that the conditions of the till layer at the bed of ice stream c are similar to those of ice stream b and that the reason for the recent stagnation of ice stream c is other than loss of till we further find that the ice stream at the grounding line is more strongly affected by ice shelf processes than by the basal shear stress

late quaternary to decadal velocity fields in asia 1 fields of crustal velocity and strain rate within asia averaged over horizontal distances of 300 km are calculated from estimates of quaternary slip rates on faults and rates of change of lengths of baselines between gps sites the calculated fields fit strain rate components estimated from quaternary slip rates within 95 confidence limits and fit the gps data with an rms residual of 2 5 mm yr 1 the strain rate field constrained only by quaternary slip rates of faults differs from the combined solution at the level of 20 nstrain yr 1 and the differences are explicable by the limited accuracy of geological estimates of slip rate therefore the strain rate fields determined by geodetic measurements taken on the 10 year timescale are consistent with geological observations on the 104 year timescale the combined solution for velocities shows plate or block like motion within deforming asia only in tarim south china and the amurian region elsewhere the kinematics of rigid blocks does not provide a useful description of the motion in particular velocities relative to eurasia point at high angles to contours of their magnitudes not parallel to them as they would if large regions moved as rigid blocks the axes of principal horizontal compressional strain align with topographic gradients in agreement with previous suggestions that asia deforms as a continuum under the influence of gravity

a reevaluation of tectonic discrimination diagrams and a new probabilistic approach using large geochemical databases moving beyond binary and ternary plots 1 statistically rigorous confidence intervals calculated from analyses of basaltic volcanic samples obtained from two large geochemical databases petdb and georoc demonstrate that published binary and ternary discrimination diagrams seldom correctly classify samples from mid ocean ridges island arcs and ocean islands with better than 60 accuracy the confidence intervals provide a measure of certainty that was previously absent from these diagrams allowing for a more robust analysis of results a new probabilistic method for geochemical discrimination is developed using the geochemical databases the new method is n dimensional and uses a priori data to construct probability distribution functions from which a posteriori probabilities are generated tests of the new method demonstrate single analysis classification success rates for volcanic rocks from island arcs to be 83 from ocean islands to be 75 and from mid ocean ridges to be 76

interseismic strain accumulation across the central north anatolian fault from iteratively unwrapped insar measurements the north anatolian fault naf is a major tectonic feature in the middle east and is the most active fault in turkey the central portion of the naf is a region of global navigation satellite systems gnss scarcity previous studies of interseismic deformation have focused on the aseismic creep near the town of ismetpasa using radar data acquired in a single line of sight direction requiring several modeling assumptions we have measured interseismic deformation across the naf using both ascending and descending data from the envisat satellite mission acquired between 2003 and 2010 rather than rejecting incorrectly unwrapped areas in the interferograms we develop a new iterative unwrapping procedure for small baseline interferometric synthetic aperture radar insar processing that expands the spatial coverage our method corrects unwrapping errors iteratively and increases the robustness of the unwrapping procedure we remove long wavelength trends from the insar data using gnss observations and deconvolve the insar velocities into fault parallel motion profiles of fault parallel velocity reveal a systematic eastward decrease in fault slip rate from 30 mm yr 25 34 95 confidence interval ci to 21 mm yr 14 27 95 ci over a distance of 200 km direct offset measurements across the fault reveal fault creep along a 130 km section of the central naf with an average creep rate of 8 2 mm yr and a maximum creep rate of 14 2 mm yr located 30 km east of ismetpasa as fault creep is releasing only 30 40 of the long term strain in the shallow crust the fault is still capable of producing large damaging earthquakes in this region

the volcanic stratigraphy and petrogenesis of the oman ophiolite complex the volcanic stratigraphy and trace element geochemistry of the oman ophiolite complex indicate a multistage magmatic origin comprising 1 magmatism due to sea floor spreading in a marginal basin 2 magmatism associated with discrete submarine volcanic centres or seamounts 3 magmatism associated with crustal uplift and rifting and 4 magmatism associated with continent arc collision trace element petrogenetic modelling is used to investigate the nature of the mantle source region and the partial melting and fractional crystallization history for each magmatic event the petrogenetic pathway for the sea floor spreading lavas requires a high degree of melting of a mantle that was depleted in incompatible elements prior to subduction but subsequently selectively enriched in certain elements mostly lil elements and h2o from an underlying subduction zone it also requires magma mixing in an open system magma chamber prior to eruption the seamount lavas were probably derived by a similar degree of partial melting of a similar source but fractional crystallization was restricted to smaller high level magma chambers the rifting lavas were derived from a mantle source that was more depleted than the seamount lavas prior to subduction but which was later modified by a larger subduction zone component the syn collision lavas were however derived from an enriched mantle source which probably underlay the passive continental margin rather than the marginal basin complex results such as these may provide considerable insight into the petrogenetic changes accompanying the transitions from spreading to arc volcanism in a supra subduction zone setting

recent advances in sar interferometry time series analysis for measuring crustal deformation abstract synthetic aperture radar sar interferometry is a technique that permits remote detection of deformation at the earth s surface and has been used extensively to measure displacements associated with earthquakes volcanic activity and many other crustal deformation phenomena analysis of a time series of sar images extends the area where interferometry can be successfully applied and also allows detection of smaller displacements through the reduction of error sources here we review recent advances in time series sar interferometry methods that further improve accuracy this is particularly important when constraining displacements due to processes with low strain rates such as interseismic deformation we include examples of improved algorithms applied to image deformation associated with the 2010 eruption of eyjafjallajokull volcano in iceland slow slip on the guerrero subduction zone in mexico and tectonic deformation in western anatolia turkey

strain rate distribution in south central tibet from two decades of insar and gps the degree to which deformation and seismicity is focused on major mapped structures remains a key unknown in assessing seismic hazards and testing continental deformation models here we combine 208 global positioning system gps velocities with 12 track interferometric synthetic aperture radar insar rate maps to form high resolution velocity and strain rate fields for south central tibet our results show that deformation is not evenly distributed across the region we find a few zones with high strain rates most notably the yutian zhongba strain rate zone however the average of the strain rates is similar within and outside the mapped fault zones in addition the slip rates are low on all the conjugate strike slip faults widespread in central tibet the observations are difficult to reconcile with time invariant block models or with continuum models that lack mechanisms for strain localization our results support arguments that the most robust estimates of seismic hazard should integrate seismicity catalogues active fault maps and geodetic strain rate models

non recognition of continental tholeiites using the ti y zr diagram continental tholeiites cannot be identified using the ti y zr diagram two hundred and thirteen analyses from 16 localities representing 7 continental tholeiitic provinces all plot outside the within plate basalt field of this diagram

rupture kinematics of 2020 january 24 mw 6 7 doganyol sivrice turkey earthquake on the east anatolian fault zone imaged by space geodesy

surface creep on the north anatolian fault at ismetpasa turkey 1944 2016 we re evaluate the 72 year history of surface slip on the north anatolian fault at ismetpasa since the mw 7 4 1944 bolu gerede earthquake a revised analysis of published observations suggests that days after the earthquake the fault had been offset by 3 7 m and 6 years later by an additional 0 74 m creep was first recognized on the fault in 1969 as a 0 13 m offset of a wall constructed in 1957 that now 2016 has been offset by 0 52 m a carbon rod creep meter operated across the fault in the past two years confirms results from an invar wire creep meter operated 1982 1991 that surface slip is episodic months of fault inactivity are interrupted by slow slip 10 m day or multiple creep events with cumulative amplitudes of 2 10 mm durations of several weeks and with slip rates briefly exceeding 2 5 mm hour creep events accommodate 80 of the surface slip and individually release 10 6 shear strain on the flanks of the uppermost 3 7 km of the fault gps and insar methods yield a current fault slip rate of 7 6 1 mm yr suggesting that creep meters incompletely sample the full width of the surface shear zone the slip rate has slowed from 10 mm yr in 1969 to 6 1 mm year at present 4 65 mm yr of which appears to be due to steady interseismic creep driven by plate boundary stressing rates we calculate that a further 1 m of aseismic surface slip will precede the next major earthquake on the fault assuming a 260 year mainshock recurrence interval on this segment

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

three dimensional displacement field of the 2015 mw8 3 illapel earthquake chile from across and along track sentinel 1 tops interferometry wide swath imaging has become a standard acquisition mode for radar missions aiming at applying synthetic aperture radar interferometry insar at global scale with enhanced revisit frequency increased swath width compared to classical stripmap imaging mode is achieved at the expense of azimuthal resolution this makes along track displacements and subsequently north south displacements difficult to measure using conventional split beam multiple aperture insar or cross correlation techniques alternatively we show here that the along track component of ground motion can be deduced from the double difference between backward and forward looking interferograms within regions of burst overlap burst overlap interferometry takes advantage of the large squint angle diversity of sentinel 1 1 to achieve subdecimetric accuracy on the along track component of ground motion we demonstrate the efficiency of this method using sentinel 1 data covering the 2015 mw8 3 illapel earthquake chile for which we retrieve the full 3 d displacement field and validate it against observations from a dense network of gps sensors

the significance of source versus process in the tectonic controls of magma genesis arculus r j 1987 the significance of source versus process in the tectonic controls of magma genesis in s d weaver and r w johnson editors tectonic controls on magma chemistry j volcanol geotherm res 32 1 12 despite the association of certain characteristic trace element signatures with particular tectonic environments of eruption there are accumulating data which would result in significant tectonic misassignments ambiguity of signals appears in active arc back arc systems of the southwestern pacific and particularly in some intracontinental plate suites given the selective preservation of continental as opposed to oceanic lithosphere inappropriate paleotectonic inferences are probable using trace element criteria alone strong relative fractionation of the alkalis and alkaline earth elements aee with respect to the rare earth elements ree in the majority of arc related magmas and a number of intraplate continental basalts is strongly suggestive of the involvement of hydrous fluids at some stages in the respective petrogenetic processes occurring in these two tectonic regimes in contrast fractionation of high field strength elements hfse such as nb and ta with respect to the ree in the same suites is most readily explained by the involvement at some stage in the magma formation process of high sio2 melts a number of widely applied tectonic discriminants makes use of aee hfse fractionation but the processes and sources involved in subduction zone petrogenesis may be duplicated during interaction of mantle derived basalt with the heterogeneous components of continental lithosphere both mantle and crust a significant role for both volatile dominated fluids and silicate melts is implicated in collision and some intracontinental plate magmatism

systematic variation in chemistry and nd sr isotopes across a caledonian calc alkaline volcanic arc implications for source materials abstract sr and nd isotope compositions and major and trace element chemistry are reported for 42 primitive calc alkaline lavas from the siluro devonian scottish old red sandstone northwestward increases in concentrations of sr ba k p and lree associated with northwest subduction of iapetus ocean crust 1 are not accompanied by change in rb th or ti group elements these relationships show that the spatial variation cannot be simply the result of change in the degree of partial melting with depth initial 143 nd 144 nd expressed as e nd at 410 ma shows a wide range from 6 4 to 3 7 and in contrast to e sr decreases markedly to the northwest samples from the midland valley show a strong anticorrelation between e nd and e sr with the correlation band offset to more radiogenic compositions than that defined by modern oceanic volcanic rocks the mantle array such an offset is common in modern volcanic arc magmas but cannot be explained by addition to the overlying mantle of a single component enriched in radiogenic sr derived from subducted lithosphere southwest highland lavas lie in a completely separate field on an e sr e nd diagram most fall within the mantle array but samples with highest concentrations of sr etc are offset to less radiogenic compositions consideration of the chemical and isotopic relationships with respect to several models of crustal contamination shows that the additional lree in the northwest cannot be derived from a crustal source the data imply the existence beneath scotland of a large region of mantle with time integrated lree enrichment parts of which may have anomalous nd sr isotopic compositions less radiogenic than the mantle array midland valley lavas are probably derived from a long term lree depleted mantle source modified by interaction with subducted oceanic lithosphere the coexistence of two mantle sources with differing histories is best explained by vertical stratification with deeper more lree enriched layers accessible only to magmas formed at great depth in a subduction zone the spatial variation probably in part reflects this mantle layering and in part the operation of some mantle zone refining process that permits efficient concentration of incompatible elements from large regions of mantle

petrogenesis and paleotectonic history of the wild bight group an ordovician rifted island arc in central newfoundland the wild bight group wbg is a sequence of early and middle ordovician volcanic subvolcanic and epiclastic rocks part of the dunnage tectonostratigraphic zone of the newfoundland appalachians a detailed geochemical and nd isotopic study of the volcanic and subvolcanic rocks has been carried out to determine the geochemical characteristics of the rocks interpret their palcotectonic environments and constrain their petrogenetic history the lower and central stratigraphic levels of the wbg contain mafic volcanic rocks with island arc geochemical signatures including lree enriched are tholeiites with e nd t 0 1 to 2 2 type a i lree depleted arc tholeiites with e nd t 5 6 to 7 1 type a ii and an unusual suite of strongly incompatible element depleted tholeiites in which e nd t ranges from 0 9 to 4 6 and is negatively correlated with147sm 144nd type a iii high silica low k rhyolites occur locally in the central part of the stratigraphy associated with mafic rocks of arc affinity and have e nd t 4 7 to 5 4 the upper stratigraphic levels of the wbg dominantly contain rocks with non arc geochemical signatures including alkalic basalts with e nd t 4 6 to 5 5 type n i strongly lree and incompatible element enriched tholeiites that are transitional between alkalic and non alkalic rocks with e nd t 4 4 to 7 0 type n ii and rocks with flat to slightly lree enriched patterns and e nd t 5 1 to 7 4 type n iii rocks with non arc and arc signatures are locally interbedded near the stratigraphic type of the wbg nd isotopic data in the type a i and a ii rocks are generally compatible with mixing partial melting models involving depleted mantle variably contaminated by a subducted crustally derived sediment the petrogenesis of type a iii rocks must involve source mixing and multi stage partial melting but the details are not clear the geochemistry and nd isotope data for types n i n ii and n iii rocks are compatible with petrogenetic models involving variable partial melting of a source similar to that postulated for modern oceanic island basalts comparison of the wbg with modern analogues suggests a 3 stage developmental model stage 1 island arc volcanism eruption of type mafic volcancs stage 2 arc rifting continued eruption of type a i a i eruption of types a ii and a iii mafic volcanics and high silica low k rhyolites and stage 3 back arc basin volcanism continued minor eruption of type a i basalts eruption of types n i n ii n iii basalts stages 1 and 2 volcanism involved partial melting of subduction contaminated mantle while stage 3 volcanism utilized depleted mantle sources not affected by the subducting slab this model provides a basis for interpreting coeval sequences in central newfoundland and a comparative framework for some early paleozoic oceanic volcanic sequences elsewhere in the appalachian orogen

bayesian geochemical discrimination of mafic volcanic rocks determining the original tectonic setting of volcanic rocks via their geochemical signature has been a long standing goal for petrologists however current visually based methods for geochemical discrimination afford only limited success we develop a probabilistic method for geochemical discrimination based upon statistics generated from geochemical databases and bayesian analysis this method incorporates elemental covariance accounts for data measurement and theoretical uncertainty and is not restricted in dimensionality of analysis which is inherent in visual systems of discrimination furthermore the method provides a direct way to discern statistical outliers whose inclusion would otherwise lead to lower discrimination accuracy tests of the approach yielded successful classification rates for single analyses of over 90 percent for volcanic arc basalts mid ocean ridge basalts and ocean island basalts

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

nubia arabia eurasia plate motions and the dynamics of mediterranean and middle east tectonics summary we use geodetic and plate tectonic observations to constrain the tectonic evolution of the nubia arabia eurasia plate system two phases of slowing of nubia eurasia convergence each of which resulted in an 50 per cent decrease in the rate of convergence coincided with the initiation of nubia arabia continental rifting along the red sea and somalia arabia rifting along the gulf of aden at 24 4 ma and the initiation of oceanic rifting along the full extent of the gulf of aden at 11 2 ma in addition both the northern and southern red sea nubia arabia plate boundary underwent changes in the configuration of extension at 11 2 ma including the transfer of extension from the suez rift to the gulf of aqaba dead sea fault system in the north and from the central red sea basin bab al mandab to the afar volcanic zone in the south while nubia eurasia convergence slowed the rate of arabia eurasia convergence remained constant within the resolution of our observations and is indistinguishable from the present day global positioning system rate the timing of the initial slowing of nubia eurasia convergence 24 4 ma corresponds to the initiation of extensional tectonics in the mediterranean basin and the second phase of slowing to changes in the character of mediterranean extension reported at 11 ma these observations are consistent with the hypothesis that changes in nubia eurasia convergence and associated nubia arabia divergence are the fundamental cause of both mediterranean and middle east post late oligocene tectonics we speculate about the implications of these kinematic relationships for the dynamics of nubia arabia eurasia plate interactions and favour the interpretation that slowing of nubia eurasia convergence and the resulting tectonic changes in the mediterranean basin and middle east resulted from a decrease in slab pull from the arabia subducted lithosphere across the nubia arabia evolving plate boundary

current plate boundary deformation of the afar rift from a 3 d velocity field inversion of insar and gps extension faulting and magmatism are the main controls on the magnitude and localization of strain at mid ocean ridges however the temporal and spatial patterns of such processes are not clear since the strain distribution has not been resolved in the past at sufficient spatial resolution and over extended areas interferometric synthetic aperture radar insar and gps data with unprecedented resolution are now available to us from the afar rift of ethiopia here we use a velocity field method to combine insar and gps to form the first high resolution continuous three dimensional velocity field of afar we study an area that is 500 km wide and 700 km long covering three branches of the afar continental rift and their triple junctions our velocity field shows that plate spreading is currently achieved in afar in contrasting modes a transient postdiking deformation is focused at the dabbahu rift segment while in central afar spreading is distributed over several overlapping segments and southern afar exhibits an interdiking deformation pattern focused at the asal ghoubbet segment we find that current spreading rates at dabbahu following the 2005 2010 intrusions are up to 110 mm yr 6 times larger than the long term plate divergence a segment centered uplift of up to 80 mm yr also occurs indicating that magma flow is still a primary mechanism of deformation during postdiking on the other hand no vertical displacements are currently observed in central and southern afar suggesting lack of significant magmatic activity at shallow levels

an aseismic slip transient on the north anatolian fault constellations of synthetic aperture radar sar satellites with short repeat time acquisitions allow exploration of active faults behavior with unprecedented temporal resolution along the north anatolian fault naf in turkey an 80 km long section has been creeping at least since the 1944 m w 7 3 earthquake near ismetpasa with a current interferometric synthetic aperture radar insar derived average creep rate of 8 3 mm yr i e a third of the naf long term slip rate we use a dense set of sar images acquired by the cosmo skymed constellation to quantify the spatial distribution and temporal evolution of creep over 1 year we identify a major burst of aseismic slip spanning 31 days with a maximum slip of 2 cm between the surface and 4 km depth this result shows that fault creep along this section of the naf does not occur at a steady rate as previously thought highlighting a need to revise our understanding of the underlying fault mechanics

land subsidence in konya closed basin and its spatio temporal detection by gps and dinsar konya closed basin that includes two depression blocks konya and tuz golu is the biggest endorheic basin in turkey a lowering in the ground levels of the depositional areas has been shown with respect to the surrounding mountains in the past this process was controlled by geological and hydrogeological phenomena nowadays it has gained a new dimension due to the excessive pumping of groundwater to the earth s surface the geodetic techniques such as global positioning system gps and interferometric synthetic aperture radar insar reveal a considerable land subsidence resulting in the rate of 1 4 cm year in konya sub basin it seems that the calculated amounts are responsible for changing environmental conditions like seasonality both gps and differential insar techniques verify these relatively small fluctuations in the subsidence development target districts that should be observed primarily are agricultural zones where groundwater is overused for irrigation and regions where human population density is high the geocoded interferogram and vegetation index map verify the spatial relation between the subsidence and green areas in this study a project dealing with the investigation of the land subsidence occurrences and of their possible causes and consequences within a specific part of konya closed basin is introduced

spatio temporal evolution of aseismic slip along the haiyuan fault china implications for fault frictional properties article history we use 20 years of synthetic aperture radar acquisitions by the ers and envisat satellites to investigate the spatial and temporal variations of strain rates along the 35 km long creeping section of the haiyuan fault at the north eastern boundary of the tibetan plateau we then use the derived displacements to infer the fault s frictional properties and discuss the relationship between creep and the seismic behavior of the fault located in between a millennial seismic gap and the 1920 m8 surface rupture trace this section has an average creep rate of 5 1m m yr about the interseismic loading rate the comparison of average surface velocity profiles derived from sar interferometry across the creeping section reveals a creep rate increase and or a creep migration to shallower depth between the 1990s and the 2000s we apply a smoothed time series analysis scheme on envisat insar data to investigate the creep rate variations during the 2004 2009 time period our analysis reveals that the creep rate accelerated in 2007 although data resolution does not allow to better constrain the onset of creep acceleration and its amplitude both decadal and short term transient behaviors are coeval with the largest earthquakes m 4 5 along the fault segment in recent years from the precise mapping of the surface fault trace we use the fault strike variations and the mohr circle construction to compute the along strike distribution of the friction coefficient along the creeping segment and compare it with the observed distribution of the creep rate we find that the creep rate scales logarithmically with the friction coefficient in agreement with the rate and state friction law in a rate strengthening regime the estimated value of log v 2 10 3 indicates that the earthquakes occurring along the creeping section cannot be the cause for a significant change in the overall segment s creep rate and that the recorded micro seismicity is most likely creep driven finally given the size and frictional properties of the creeping section we estimate based on previous models of dynamic rupture simulations a 0 20 probability for a rupture to break through this section together with the geometrical configuration of the haiyuan fault these results suggest that the creeping segment may act as a persistent barrier to earthquake propagation

probing europa s hidden ocean from tidal effects on orbital dynamics recent observations of europa suggest that the jovian satellite may have a liquid ocean underneath its icy surface geophysical models indicate that the tidal love number k2 has a strong dependence on the presence or absence of an ocean the k2 dependence on the ice shell thickness is also significant measurements of the static and tidal gravity fields through their dynamic effects on the trajectory of a low europan orbiter can be essential in the detection of an ocean and inference of other internal structures covariance analyses have been carried out to assess accuracies using simulated doppler tracking data with 15 days of tracking from 2 earth stations the uncertainties for k2 mantle libration amplitude and the epoch radial position of the spacecraft are expected to be 0 0004 2 8 arcsec and 5 7 m respectively these tight constraints will strongly contribute to ocean detection and ice thickness determination when combined with altimeter measurements

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

a geodesy and seismicity based local earthquake likelihood model for central los angeles we estimate time independent earthquake likelihoods in central los angeles using a model of interseismic strain accumulation and the 1932 2017 seismic catalog we assume that on the long term average earthquakes and aseismic deformation collectively release seismic moment at a rate balancing interseismic loading mainshocks obey the gutenberg richter law a log linear magnitude frequency distribution mfd up to a maximum magnitude and a poisson process and aftershock sequences obey the gutenberg richter and bath laws we model a comprehensive suite of these long term systems assess how likely each system would be to have produced the mfd of the instrumental catalog and use these likelihoods to probabilistically estimate the long term mfd we estimate m max 6 8 1 05 0 4 every 300 years or m max 7 05 0 95 0 4 assuming a truncated or tapered gutenberg richter mfd respectively our results imply that for example the median likelihood of one or more m w 6 5 mainshocks is 0 2 in 1 year 2 in 10 years and 18 21 in 100 years

extent and distribution of aseismic slip on the ismetpasa segment of the north anatolian fault turkey from persistent scatterer insar we use the persistent scatterer insar psi technique with elastic dislocation models and geology along the creeping section of the north anatolian fault naf at ismetpasa to map and deduce the velocity field and the aseismic slip distribution revealing the spatiotemporal nature of the creep helped us associate the creep with potential lithological controls hence providing a new perspective to better understand the underlying causes and mechanisms the psi analysis of envisat asar images between 2003 and 2010 reveals a clear picture of surface creep along the fault and a new interseismic velocity field transitioning gradually between the creeping and the locked fault sections the creep rate is found to fluctuate along a 100 km long section of the fault in a manner similar to that along the hayward fault reaching a maximum of 20 2 mm yr close to the far field plate velocity 25 1 5 mm yr at ismetpasa it is in the range of 8 2 mm yr consistent with the previous geodetic observations the creeping section appears to extend 30 km further east than those previously reported modeling of the psi data reveals a heterogeneous creep distribution at depth with two main patches confined mostly to the uppermost 5 km portion of the seismogenic crust releasing annually 6 2 1016 nm mw 5 1 geodetic moment our analysis combined with previous studies suggests that creep might have commenced as postseismic deformation following the 1944 earthquake and has evolved to stable fault creep with time there is a correlation between aseismic surface creep and the geology along the fault as it is in major part associated to rocks with low frictional strength such as the andesitic basaltic limestone and serpentine bodies within the fault zone

gear1 a global earthquake activity rate model constructed from geodetic strain rates and smoothed seismicity global earthquake activity rate model 1 gear1 estimates the rate of shallow earthquakes with magnitudes 6 9 everywhere on earth it was designed to be reproducible and testable our preferred hybrid forecast is a log linear blend of two parent forecasts based on the global centroid moment tensor cmt catalog smoothing 4602 m 5 767 shallow earthquakes 1977 2004 and the global strain rate map version 2 1 smoothing 22 415 global positioning system velocities optimized to best forecast the 2005 2012 global cmt catalog strain rate is a proxy for fault stress accumulation and earthquakes indicate stress release so a multiplicative blend is desirable capturing the strengths of both approaches this preferred hybrid forecast outperforms its seismicity and strain rate parents the chance that this improvement stems from random seismicity fluctuations is less than 1 the preferred hybrid is also tested against the independent parts of the international seismological centre global earthquake model catalog m 6 8 during 1918 1976 with similar success gear1 is an update of this preferred hybrid comparing gear1 to the uniform california earthquake rupture forecast version 3 ucerf3 net earthquake rates agree within 4 at m 5 8 and at m 7 0 the spatial distribution of ucerf3 epicentroids most resembles gear1 after ucerf3 is smoothed with a 30 km kernel because ucerf3 has been constructed to derive useful information from fault geometry slip rates paleoseismic data and enhanced seismic catalogs not used in our model this is encouraging to build parametric catastrophe bonds from gear1 one could calculate the magnitude for which there is a 1 or any annual probability of occurrence in local regions online material discussion of forecast scoring metrics tables of scoring results and source code and data files needed to reproduce forecast

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

constraining crustal velocity fields with insar for eastern turkey limits to the block like behavior of eastern anatolia the sentinel 1 satellite mission will enable global strain rate mapping from interferometric synthetic aperture radar insar and gps data and methods to combine these data in velocity fields will become increasingly important here we use insar to measure interseismic deformation in eastern turkey across a 250 000 km2 area that spans the arabia eurasia plate boundary zone from our insar data we first estimate slip rates and locking depths for the north and east anatolian faults naf and eaf of 20 3 mm yr and 16 km and 11 3 mm yr and 16 km respectively but we also combine the insar data with existing gps velocity measurements to construct high resolution velocity and strain rate fields across the region for the first time we calculate 2 d and 3 d velocity fields and find that strain is mainly localized across the naf and eaf and that there is negligible differential vertical motion across the eastern anatolian plateau we also show that high resolution 2 d strain rate fields can be calculated from insar alone even in the absence of gps data we fit a block model to our velocity field and estimate slip rates of 21 mm yr and 8 mm yr for the naf and eaf showing that our previous estimates differ from these values because they neglected crustal rotation although this rotation is an important component of the velocity field in eastern turkey systematic residuals between our velocity field and the best fitting block for anatolia suggest that the region is not block like as proposed by previous authors

insar observations of strain accumulation and fault creep along the chaman fault system pakistan and afghanistan we use 2004 2011 envisat synthetic aperture radar imagery and insar time series methods to estimate the contemporary rates of strain accumulation in the chaman fault system in pakistan and afghanistan at 29 n we find long term slip rates of 16 2 3 mm yr for the ghazaband fault and of 8 3 1 mm yr for the chaman fault this makes the ghazaband fault one of the most hazardous faults of the plate boundary zone we further identify a 340 km long segment displaying aseismic surface creep along the chaman fault with maximum surface creep rate of 8 1 2 mm yr the observation that the chaman fault accommodates only 30 of the relative plate motion between india and eurasia implies that the remainder is accommodated south and east of the katawaz block microplate

geochemistry of the miocene mount noel volcanic complex british columbia and comparison with the columbia river basalt the 19 6 ma mount noel volcanic complex mnvc is located about 150 km east of the garibaldi volcanic belt and adjacent to the chilcotin plateau basalts in southwestern british columbia the mnvc unconformably overlies jurassic to cretaceous metasedimentary rocks and lower cretaceous coast plutonic rocks the complex consists of flat lying columnar jointed basalt flows along with volcaniclastic debris flows and minor pyroclastic rocks basaltic flows have olivine fo 60 to fo 85 and plagioclase an 60 to an 80 phenocrysts with clinopyroxene microphenocrysts major trace and rare earth element analyses of the mnvc indicate the flows can be divided into two groups the largest group comprises tholeiitic to transitional basalt whereas a smaller subset is alkaline basalt rare earth element patterns are slightly enriched in the light rare elements in the transitional group and more strongly enriched in the alkaline basalts in tectonic discriminant diagrams all basalts plot in the within plate fields or in overlap areas typical of continental flood basalts alkaline basalts found only at the base of the thick sequence of tholeiitic to transitional basalts are characterized by high p 2 o 5 sr and ba contents the mnvc tholeiitic to transitional basalts are comparable to the chilcotin group basalts and to the lowermost basalts of the columbia river group the origin of mnvc basalts is best interpreted as volcanism behind the pemberton volcanic arc

why earthquake hazard maps often fail and what to do about it abstract the 2011 tohoku earthquake is another striking example after the 2008 wenchuan and 2010 haiti earthquakes of highly destructive earthquakes that occurred in areas predicted by earthquake hazard maps to be relatively safe here we examine what went wrong for tohoku and how this failure illustrates limitations of earthquake hazard mapping we use examples from several seismic regions to show that earthquake occurrence is typically more complicated than the models on which hazard maps are based and that the available history of seismicity is almost always too short to reliably establish the spatiotemporal pattern of large earthquake occurrence as a result key aspects of hazard maps often depend on poorly constrained parameters whose values are chosen based on the mapmakers preconceptions when these are incorrect maps do poorly this situation will improve at best slowly owing to our limited understanding of earthquake processes however because hazard mapping has become widely accepted and used to make major decisions we suggest two changes to improve current practices first the uncertainties in hazard map predictions should be assessed and clearly communicated to potential users recognizing the uncertainties would enable users to decide how much credence to place in the maps and make them more useful in formulating cost effective hazard mitigation policies second hazard maps should undergo rigorous and objective testing to compare their predictions to those of null hypotheses including ones based on uniform regional seismicity or hazard such testing which is common and useful in similar fields will show how well maps actually work and hopefully help produce measurable improvements there are likely however limits on how well hazard maps can ever be made because of the intrinsic variability of earthquake processes

insar velocity field across the north anatolian fault eastern turkey implications for the loading and release of interseismic strain accumulation we use the persistent scatterer interferometric synthetic aperture radar ps insar technique with the european space agency s envisat and ers sar data acquired on three neighboring descending tracks t350 t078 and t307 to map the interseismic strain accumulation along a 225 km long nw se trending section of the north anatolian fault that ruptured during the 1939 1942 and 1943 earthquakes in eastern turkey we derive a line of sight velocity map of the region with a high spatial resolution and accuracy which together with the maps of earthquake surface ruptures shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike slip faults in contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event modeling of the high resolution ps insar velocity field reveals a fairly linear and narrow throughgoing shear zone with an overall 20 3 mm yr slip rate above an unexpectedly shallow 7 2 km locking depth such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault a narrow throughgoing shear zone supports the thick lithosphere model in which continental strike slip faults are thought to extend as discrete shear zones through the entire crust fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and or develop during coseismic rupture propagation the geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles

a spatially varying scaling method for insar tropospheric corrections using a high resolution weather model variation in tropospheric delay is a major limiting factor on the accuracy of interferometric synthetic aperture radar insar measurements this is particularly the case when deformation and topography are correlated to address limitations of previous insar tropospheric correction methods here we present a new approach that combines the use of both external weather model data and the interferometric phase we assume that vertical refractivity profiles calculated from a high resolution weather model data can generally describe the form of the relationship between tropospheric delay and height but that the magnitude can be incorrect we estimate a magnitude correction by scaling the original delays to best match the interferometric phase we validated our new method using simulated data and demonstrate that both coseismic and interseismic signals can be separated from strong tropospheric delays we also applied our algorithm to the central portion of the altyn tagh fault in northern tibet where deformation correlates strongly with topographic relief of 6 000 m and show that the derived velocity field is more internally consistent and agrees better with independent global positioning system measurements

millenary mw 9 0 earthquakes required by geodetic strain in the himalaya the himalayan arc produced the largest known continental earthquake the m w 8 7 assam earthquake of 1950 but how frequently and where else in the himalaya such large magnitude earthquakes occur is not known paleoseismic evidence for coseismic ruptures at the front of the himalaya with 15 to 30 m of slip suggests even larger events in medieval times but this inference is debated here we estimate the frequency and magnitude of the largest earthquake in the himalaya needed so that the moment released by seismicity balances the deficit of moment derived from measurements of geodetic strain assuming one third of the moment buildup is released aseismically and the earthquakes roughly follow a gutenberg richter distribution we find that m w 9 0 events are needed with a confidence level of at least 60 and must return approximately once per 800 years on average

long term growth of the himalaya inferred from interseismic insar measurement the rise and support of the 5000 m topographic scarp at the front of indian eurasian collision in the himalaya involves long term uplift above a mid crustal ramp within the main himalayan thrust mht system locking of the shallower portion of the flat ramp flat during the interseismic period also produces transient uplift above the transition zone however spatial and temporal relationships between permanent and transient vertical deformation in the himalaya are poorly constrained leading to an unresolved causal relationship between the two here we use interferometric synthetic aperture radar insar to measure interseismic uplift on a transect crossing the whole himalaya in central nepal the uplift velocity of 7 mm yr at the front of the annapurna mountain range is explained by an 18 21 mm yr slip rate on the deep shallow dipping portion of the mht with full locking of the mid crustal ramp underlying the high himalaya the transient uplift peak observed by insar matches spatially with the long term uplift peak deduced from the study of trans himalayan river incision although models of the seismic cycle involving thrusting over a ramp of fixed geometry predict an 20 km separation between the two peaks we argue that this coincidence indicates that today s mid crustal ramp in central nepal is located southward with respect to its average long term location suggesting that mountain growth proceeds by frontward migration of the ramp driven by underplating of material from the indian plate under the himalaya

probing europa s interior with natural sound sources europa s interior structure may be determined by relatively simple and robust seismo acoustic echo sounding techniques the strategy is to use ice cracking events or impacts that are hypothesized to occur regularly on europa s surface as sources of opportunity a single passive geophone on europa s surface may then be used to estimate the thickness of its ice shell and the depth of its ocean by measuring the travel time of seismo acoustic reflections from the corresponding internal strata quantitative analysis is presented with full field seismo acoustic modeling of the europan environment this includes models for europan ambient noise and conditions on signal to noise ratio necessary for the proposed technique to be feasible the possibility of determining europa s ice layer thickness by surface wave and modal analysis with a single geophone is also investigated

measurement of interseismic strain accumulation across the north anatolian fault by satellite radar interferometry in recent years interseismic crustal velocities and strains have been determined for a number of tectonically active areas through repeated measurements using the global positioning system the terrain in such areas is often remote and difficult and the density of gps measurements relatively sparse in principle satellite radar interferometry can be used to make millimetric precision measurements of surface displacement over large surface areas in practice the small crustal deformation signal is dominated over short time intervals by errors due to atmospheric topographic and orbital effects here we show that these effects can be overcome by stacking multiple interferograms after screening for atmospheric anomalies effectively creating a new interferogram that covers a longer time interval in this way we have isolated a 70 km wide region of crustal deformation across the eastern end of the north anatolian fault turkey the distribution of deformation is consistent with slip of 17 32 mm yr below 5 33 km on the extension of the surface fault at depth if the gps determined slip rate of 24 1 mm yr is accepted the locking depth is constrained to 18 6 km

interferometric synthetic aperture radar atmospheric correction using a gps based iterative tropospheric decomposition model abstract atmospheric effects represent one of the major error sources of repeat pass interferometric synthetic aperture radar insar and could mask actual displacements due to tectonic or volcanic deformation the tropospheric delays vary both vertically and laterally and can be considered as the sum of i a vertically stratified component highly correlated with topography and ii a turbulent component resulting from turbulent processes in the troposphere varying both in space and time in this paper we outline a framework to routinely use pointwise gps data to reduce tropospheric effects on satellite radar measurements an iterative tropospheric decomposition itd model is used and further developed to separate tropospheric stratified and turbulent signals and then generate high resolution correction maps for sar interferograms cross validation is employed to assess the performance of the itd model and act as an indicator to users of when and where correction is feasible tests were carried out to assess the impact of gps station spacing on the itd model insar correction performance which provides insights into the trade off between station spacing and the achievable accuracy the application of this framework to sentinel 1a interferograms over the southern california usa and southern england uk regions shows approximately 45 78 of noise reduction even with a sparse 50 80 km station spacing gps network and or with strong and non random tropospheric turbulence this is about a 50 greater improvement than previous methods it is believed that this framework could lead to a generic insar atmospheric correction model while incorporating continuous and global tropospheric delay datasets e g numerical weather models

what can gps data tell us about the dynamics of post seismic deformation summary this paper describes differences in time varying post seismic deformation due to after slip and viscoelastic relaxation following large strike slip earthquakes and how these differences may be exploited to characterize the configuration and rheology of aseismically deforming material in the subsurface the analysis involves two steps first near field time dependent post seismic deformation characteristics of a typical mw 7 4 strike slip earthquake is defined based on analysis of gps data from three recent earthquakes secondly this earthquake is modelled assuming uniform slip along a rectangular surface and several classes of after slip and viscoelastic relaxation models that can reproduce the evolution of early post seismic displacements with time at a near field reference point are developed postseismic displacements and velocities away from the reference point where the differences are greatest and thus most likely to be distinguished with gps are compared i find that displacements from a judiciously designed network of continuous or frequently occupied campaign mode gps sites are sufficiently precise to distinguish linear viscoelastic relaxation from after slip on a vertical surface extending the coseismic rupture furthermore both the thickness and viscosity of a relaxing linearly viscoelastic layer may be identified to maximize what post seismic gps surveys can tell us particularly concerning potential relaxation of low viscosity layers in the crust and or upper mantle some gps sites should be located along strike beyond the rupture tip also far field gps sites should be occupied as frequently as sites close to the rupture

lead isotope variability of fine grained river sediments in tibetan plateau water catchments implications for geochemical provinces and crustal evolution abstract the crustal structure of the tibetan plateau records the dynamic processes of several terranes that underwent disaggregation aggregation and amalgamation the dynamic evolution of continental crusts is best understood from these three processes however the detailed geochemical province division of the tibetan plateau and the palaeo tectonic affinity or evolution of terranes remains unclear in this paper the acid insoluble fraction of fine grained river sediments from catchments in the whole tibetan plateau was measured for lead isotopes and trace elements this study aims to reveal lead isotopic characteristics to delineate different lead isotope geochemical provinces and to trace and uncover the tectonic affinities of various terranes in the tibetan plateau results show that by weak acid chemical treatment the characteristics of the pb isotopes of fine grained river sediments can be utilized to represent and discriminate geochemical provinces the characteristics of pb isotopes enable the identification of different geochemical provinces and the palaeo affinity of various tectonic units constrained by tectonic evolution the tibetan plateau tectonic units can be divided into the following five pb isotope geochemical provinces 1 qilian terrane 2 northern tibetan plateau geochemical province including eastern kunlun qaidam songpan ganzi and eastern qiangtang terrane 3 northern lhasa terrane 4 southern lhasa terrane and 5 himalaya terrane in relation to the controversy concerning the palaeo affinity of the qilian and songpan ganzi terranes the pb isotopic compositions of fine grained river sediments suggest that they were much more likely separated from the yangtze craton than from the north china craton the characteristics of pb isotopes and trace elements of the eastern kunlun qaidam and eastern qiangtang terrane show some similarities with the songpan ganzi terrane which indicate that they also possibly originated from the disaggregation of the yangtze craton the various partial melting and contamination of the old himalaya continental crust from radiogenic pb isotopes and tethys mantle materials with low radiogenic pb isotopes caused different pb isotopes and trace elemental associations in the southern and northern lhasa terranes these factors also led to the evolution of the two different geochemical provinces

deformation of western turkey from a combination of permanent and campaign gps data limits to block like behavior 1 we present a new geodetic velocity field covering western turkey south of the north anatolian fault our velocity field is derived from a combination of continuously recording gps stations operating since 2003 survey type gps measurements carried out in the period 1997 2005 and velocities from reilinger et al 2006 the velocity field indicates that western turkey currently undergoes extension whose rate increases from the anatolia plateau to the aegean coast the overall extension in westernmost turkey is about 20 mm yr making it one of the fastest areas of continental extension in the world we test whether the observed deformation is better represented by the rotation of crustal blocks or by more distributed deformation while no deformation is detected in the central anatolian plateau we observe a deformation field west of the plateau that cannot be explained by block models unless the blocks are so small as to be essentially indistinguishable from a continuum although concentration of strain rates up to 140 nstrain yr are found across the major grabens strain rates above 50 nstrain yr are found throughout western turkey the distributions of topography and crustal thickness in western turkey agree with the distributions expected if the crust there had a constant thickness at 5 ma equal to that of the present central anatolian plateau and had subsequently been thinned at the present day distribution of strain rates our results therefore suggest that extensional strain affects the whole continental lithosphere of western turkey rather than being restricted to a small number of block boundaries

constraints from gps measurements on the dynamics of deformation in anatolia and the aegean we estimate the strength of the lithosphere in anatolia and the aegean and the boundary forces acting upon it using a dynamical model that treats the lithosphere as a thin fluid sheet deforming in response to variations in gravitational potential energy this model has one free material parameter the power law exponent n of the vertically averaged rheology of the lithosphere and two parameters that specify the forces per unit length applied to its edges solutions to this model that best fit the velocities of 346 reliable gps sites require an effective viscosity of the lithosphere of 1022 to 1021 pa s at strain rates of 10 to 100 nanostrain per year the best fitting force at the arabia anatolia boundary is consistent with the lithostatic pressure due to the high topography there and the force at the nubia aegean boundary is consistent with the contrast in lithostatic pressure across that boundary no additional force from slab rollback or basal tractions due to convection in the mantle is required to explain the observations these results are supported by scaling relations derived from approximate analytical solutions the inverse relationship between the viscosity of the lithosphere and deviatoric stress produces strong slowly deforming regions in the southern aegean and central anatolia whose motions resemble those of microplates the distribution of geodetic strain rates within the region and the partitioning between normal and strike slip faulting are explained by the interplay between boundary conditions internal variations in gravitational potential energy and the power law rheology of the lithosphere

high resolution interseismic velocity data along the san andreas fault from gps and insar 1 we compared four interseismic velocity models of the san andreas fault based on gps observations the standard deviations of the predicted secular velocity from the four models are larger north of the san francisco bay area near the creeping segment in central california and along the san jacinto fault and the east california shear zone in southern california a coherence spectrum analysis of the secular velocity fields indicates relatively high correlation among the four models at longer wavelengths 15 40 km with lower correlation at shorter wavelengths to improve the short wavelength accuracy of the interseismic velocity model we integrated interferometric synthetic aperture radar insar observations initially from advanced land observing satellite alos ascending data spanning from the middle of 2006 to the end of 2010 totaling more than 1100 interferograms with gps observations using a sum remove filter restore approach the final insar line of sight data match the point gps observations with a mean absolute deviation of 1 5 mm yr we systematically evaluated the fault creep rates along major faults of the san andreas fault and compared them with creepmeters and alignment array data compiled in uniform california earthquake rupture forecast version 2 ucerf2 moreover this insar line of sight dataset can constrain rapid velocity gradients near the faults which are critical for understanding the along strike variations in stress accumulation rate and associated earthquake hazard

applicability of sentinel 1 terrain observation by progressive scans multitemporal interferometry for monitoring slow ground motions in the san francisco bay area 2017 american geophysical union all rights reserved data from the sentinel 1 satellite have already proven useful for investigating seismic and volcanic events since its launch in april 2014 the requirement of ultrahigh coregistration accuracy and the current relatively short time of sentinel 1 acquisitions make its application challenging for studying slow deformation processes such as fault creep and land subsidence here we analyze a set of 14 sar images over the san francisco bay area spanning 1 year from early 2015 to 2016 we show that implementing an existing enhanced spectral diversity algorithm or using precise orbits together with a reference digital elevation model both yield the required coregistration accuracy for making use of the phase measurements in time series analysis of ground deformation following a thorough validation test we update our estimates of hayward fault creep rate and confirm uplift due to recharge of the santa clara valley aquifer system during the final summer of 4 year drought

isotopic and trace element composition of volcanic glasses from the akaki canyon cyprus implications for the origin of the troodos ophiolite abstract we report major elements k rb cs sr ba sc cr ni hf ta th and ree concentrations and isotopic compositions of sr nd pb and o of carefully handpicked volcanic glasses from the akaki river section of the troodos ophiolite complex on the basis of sr and o isotopic composition and fe 2 o 3 feo ratios nine of the ten glasses analyzed are considered to be fresh even with respect to those elements that are easily affected by alteration the glasses range in composition from basaltic andesite to dacite incompatible element concentrations in the mafic compositions are low 10 chondritic and the light ree are strongly depleted however the ratios of low field strength elements k rb cs sr th to high field strength elements ta hf ti and rare earth elements are higher than those in n morb nd isotopic compositions show a very small range with e nd t 80ma varying from 6 5 to 7 5 initial 87 sr 86 sr ratios range from 0 7033 to 0 7040 pb isotope ratios have a restricted range with 206 pb 204 pb 18 60 18 70 207 pb 204 pb 15 55 15 59 and 208 pb 204 pb 38 08 38 51 the oxygen isotopic composition for fresh glasses falls within the range reported for fresh mafic mantle derived volcanics with 18 o varying from 5 4 to 6 5 all geochemical characteristics of the troodos volcanic glasses are similar to those observed in supra subduction zone volcanics but we cannot distinguish between an early stage island arc or back arc origin for the troodos ophiolite on a geochemical basis only however considering our data and previously published geologic and geochemical data we suggest that the troodos ophiolite formed in the earliest stages of island arc development

a model of the earthquake cycle along the san andreas fault system for the past 1000 years 1 we simulate 1000 years of the earthquake cycle along the san andreas fault system by convolving best estimates of interseismic and coseismic slip with the green s function for a point dislocation in an elastic plate overlying a viscoelastic half space interseismic slip rate is based on long term geological estimates while fault locking depths are derived from horizontal gps measurements coseismic and postseismic deformation is modeled using 70 earthquake ruptures compiled from both historical data and paleoseismic data this time dependent velocity model is compared with 290 present day geodetic velocity vectors to place bounds on elastic plate thickness and viscosity of the underlying substrate best fit models rms residual of 2 46 mm yr require an elastic plate thickness greater than 60 km and a substrate viscosity between 2 1018 and 5 1019 pa s these results highlight the need for vertical velocity measurements developed over long time spans 20 years our numerical models are also used to investigate the 1000 year evolution of coulomb stress stress is largely independent of assumed rheology but is very sensitive to the slip history on each fault segment as expected present day coulomb stress is high along the entire southern san andreas because there have been no major earthquakes over the past 150 300 years animations s1 and s2 of the time evolution of vector displacement and coulomb stress are available as auxiliary material

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

an expert system for the tectonic characterization of ancient volcanic rocks the expert system approach enables geochemical evidence to be integrated with geological petrological and mineralogical evidence in identifying the eruptive setting of ancient volcanic rocks this paper explains the development of escort an expert system for characterization of rock types escort uses as its knowledge base a set of dispersion matrices derived from a geochemical data bank of some 8000 immobile element analyses together with tables of magma type membership probabilities based on a priori knowledge the dominant flow type the facies of intercalated sediment the basement to the volcanic sequence the presence or absence of an iron enrichment trend and the phenocryst phase assemblage inferencing is based on the bayes decision rule adapted to take into account possible uncertainties in the geological evidence upper and lower probability thresholds are used to decide whether an interpretation is likely or unlikely evaluation of the system shows that it is able to overcome many of the well publicized ambiquities attached to geochemical discrimination diagrams as well as providing a unified method of decision making and a measure of the correctness of the interpretation

partitioning of localized and diffuse deformation in the tibetan plateau from joint inversions of geologic and geodetic observations abstract the spatial complexity of continental deformation in the greater tibetan plateau region can be defined as the extent to which relative motion of the indian and asian plates is partitioned between localized slip on major faults and distributed deformation potency rates provide a quantitative metric for determining the magnitudes of diffuse and on fault crustal deformation which are proportional to strain rates within crustal micro plates and fault slip rates respectively we simultaneously estimate micro plate rotation rates interseismic elastic strain accumulation fault slip rates on major structures and strain rates within 24 tectonic micro plates inferred from active fault maps in the greater tibetan plateau region using quasi static block models constrained by interseismic surface velocities at 731 gps sites and 9 holocene late quaternary geologic fault slip rates the joint geodetic geologic inversion indicates that geologic slip rates are kinematically consistent with differential micro plate motions estimated left lateral slip rates on the altyn tagh west central kunlun and xianshuihe faults are relatively homogeneous along strike 11 5 10 5 and 11 mm yr respectively while segmentation of the eastern kunlun fault by the intersecting elashan and riyueshan faults results in a decreased slip rate consistent with geologic observations the fraction of total potency rate associated with intrablock strain uncorrected for observational noise ranges from 0 27 in the himalayan range block to 0 91 in the aksai chin block monte carlo simulations are used to quantify the likelihood that internal deformation is statistically distinguishable from the uncertainties in geodetic velocities these simulations indicate that internal block deformation is statistically significant only within the himalayan range front where internal deformation accounts for id 0 11 of block potency rate budget west central plateau id 0 68 ganzi yushu xianshuihe 0 58 burma 0 09 jiali 0 38 and aksai chin 0 68 blocks in the other 18 tectonic micro plates within the plateau region estimated internal block potency is not currently distinguishable from the expected contribution of observational noise to residual velocities of the total potency budget within the tibetan plateau 85 is taken up by slip on major faults with the remaining 15 accommodated by internal processes at sub block scale distinguishable from observational noise the localization of the majority of plate boundary activity is also supported by the spatial distribution of modern and historical crustal earthquakes sixty seven percent of the total moment released by earthquakes in the cmt catalog and 90 of historical moment since 1900 have been released within 25 km of the major faults included in the block model representing only 12 of the characteristic half block length scale of 215 km the localization of deformation inferred from geologic geodetic and seismic observations suggests that forces applied to tectonic micro plates drive fault system activity at the india asia collision zone over decadal to quaternary time scales

localized and distributed creep along the southern san andreas fault we investigate the spatial pattern of surface creep and off fault deformation along the southern segment of the san andreas fault using a combination of multiple interferometric synthetic aperture radar viewing geometries and survey mode gps occupations of a dense array crossing the fault radar observations from envisat during the period 2003 2010 were used to separate the pattern of horizontal and vertical motion providing a high resolution image of uplift and shallow creep along the fault trace the data reveal pervasive shallow creep along the southernmost 50 km of the fault creep is localized on a well defined fault trace only in the mecca hills and durmid hill areas while elsewhere creep appears to be distributed over a 1 2 km wide zone surrounding the fault the degree of strain localization is correlated with variations in the local fault strike using a two dimensional boundary element model we show that stresses resulting from slip on a curved fault can promote or inhibit inelastic failure within the fault zone in a pattern matching the observations the occurrence of shallow localized interseismic fault creep within mature fault zones may thus be partly controlled by the local fault geometry and normal stress with implications for models of fault zone evolution shallow coseismic slip deficit and geologic estimates of long term slip rates

the 2014 2015 eruption of fogo volcano geodetic modeling of sentinel 1 tops interferometry after 20 years of quiescence fogo volcano erupted in november 2014 the eruption produced fast moving lava flows that traveled for several kilometers and destroyed two villages this event represents the first episode of significant surface deformation imaged by the new european space agency s sentinel 1 satellite in its standard acquisition mode terrain observation by progressive scans tops which differs from that of previous synthetic aperture radar sar missions we perform a bayesian inversion of sentinel 1 tops sar interferograms spanning the eruption and accurately account for variations in the tops line of sight vector when modeling displacements our results show that magma ascended beneath the pico do fogo cone and then moved laterally toward its southwestern flank where the eruptive fissure opened this study provides important insights into the inner workings of fogo volcano and shows the potential of sentinel 1 tops interferometry for geophysical e g volcano monitoring applications

geochemical 40ar 39ar age and isotopic data for crustal rocks of the neyriz ophiolite iran trace element data including the rare earth elements in the crustal sequence of the neotethyan neyriz ophiolite in southwest iran indicate normal mid ocean ridge basalt n morb or island arc tholeiite chemistry for the tang e hana basalt the data suggest that the tang e hana rhyodacite basalt plagiogranite and gabbro derived from a low k tholeiitic parent magma trace element distributions in amphibolite clasts in the sole detachment of the ophiolite south of lake neyriz correlate well with distributions in basalt clasts in the melange and in the tang e hana basalt these trace elements suggest that the amphibolite originated from metamorphism and deformation of a tholeiitic basalt protolith new 40 ar 39 ar incremental heating plateau ages from two hornblende plagiogranite specimens in the crustal sequence in tang e hana are 92 07 1 69 and 93 19 2 48 ma isotopic data for five tang e hana basalts yield end values of 7 8 and 7 9 and 87 sr 86 sr values of 0 70368 to 0 70476 the isotopic compositions ophiolite tectonostratigraphy and correlation of the 40 ar 39 ar cooling plagiogranite and deformation amphibolite ages suggest emplacement of the neyriz ophiolite either into an accretionary prism through offscraping and subduction erosion and or formation in a supra subduction zone environment around 82 96 ma progressive accretion probably led to the de velopment of a fore arc basin and deposition of upper cretaceous eocene fore arc and arc derived sediments on the ophiolite resume des donnees sur les elements traces incluant les terres rares dans la sequence crustale de l ophiolite neo tethysienne de neyriz dans le sud ouest de l iran indiquent que le basalte de tang e hana est de type basalte oceanique de type n n morb ou une tholeiite d arc insulaire les donnees recueillies suggerent que la rhyodacite le basalte le plagiogranite et le gabbro de tang e hana proviennent d un magma tholeiitique parent a faible teneur potassique la repartition des elements traces dans les clastes amphiboliques dans l unique portion separee de l ophiolite au sud du lac neyriz est en bonne correlation avec celle trouvee dans les clastes basaltiques du melange ophiolitique et du basalte de tang e hana ces elements traces laissent penser que l amphibolite provient du metamorphisme et de la deformation d un protolithe de basalte tholeiitique de nouveaux ges 40 ar 39 ar par paliers de temperature pour deux specimens de plagiogranite a hornblende appartenant a la sequence crustale de tang e hana ont donne des valeurs de 92 07 1 69 ma et de 93 19 2 48 ma des donnees isotopiques de cinq basaltes de tang e hana ont donne des valeurs end de 7 8 et de 7 9 et des valeurs 87 sr 86 sr de 0 70368 a 0 70476 les compositions isotopiques la tectonostratigraphie ophiolitique et la correlation entre les ges 40 ar 39 ar de refroidissement plagiogranite et de deformation amphibolite laissent croire que l ophiolite de neyriz a ete mise en place dans le prisme d accretion sous l effet de l ecaillage et de l erosion par subduction et ou s est formee au sein d un environnement a zone de supra subduction il y environ 82 ma a 96 ma l accretion graduelle a probablement conduit au developpement d un bassin d avant arc et au depot de sediments provenant de l avant arc et de l arc sur l ophiolite au cours du cretace superieur et de l eocene

block like plate movements in eastern anatolia observed by insar 1 the question whether continental plates deform internally or move as rigid blocks has been debated for several decades to further address this question we use large scale interferometric synthetic aperture radar insar data sets to study how eastern anatolia and its surrounding plates deform we find that most of the deformation is focused at the north and east anatolian faults and little intraplate deformation takes place anatolia is therefore moving at least its eastern part as a uniform block we estimate the slip velocity and locking depth of the north anatolian fault at this location to be 20 mm yr and 14 km respectively high deformation gradient found near the east anatolian fault on the other hand suggests that little stress is accumulating along the eastern sections of that fault

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

insar observations of low slip rates on the major faults of western tibet two contrasting views of the active deformation of asia dominate the debate about how continents deform i the deformation is primarily localized on major faults separating crustal blocks or ii deformation is distributed throughout the continental lithosphere in the first model western tibet is being extruded eastward between the major faults bounding the region surface displacement measurements across the western tibetan plateau using satellite radar interferometry insar indicate that slip rates on the karakoram and altyn tagh faults are lower than would be expected for the extrusion model and suggest a significant amount of internal deformation in tibet

satellite geodetic imaging reveals internal deformation of western tibet 1 it is often assumed that the majority of the interseismic strain accumulates around the major mapped geological block boundaries however numerous recent earthquakes in the continents have occurred on faults that were previously unidentified existing deformation data from tibet are insufficiently dense to map the distribution of interseismic strain here we combine 265 interferograms formed from 166 radar images with gps data to constrain a high resolution velocity field covering 200 000 km2 of western tibet we confirm that the slip rate of the karakoram fault is low 6 mm yr but show that areas of focused strain do not coincide with the major fault structures some of this strain is due to postseismic relaxation after a mw 6 8 earthquake that occurred in 1996 on a structure that is difficult to identify in satellite imagery models of seismic hazard that rely on imperfect knowledge of the boundaries of crustal blocks can therefore underestimate hazard from unknown faults

high resolution surface velocities and strain for anatolia from sentinel 1 insar and gnss data measurements of present day surface deformation are essential for the assessment of long term seismic hazard the european space agency s sentinel 1 satellites enable global high resolution observation of crustal motion from interferometric synthetic aperture radar insar we have developed automated insar processing systems that exploit the first 5 years of sentinel 1 data to measure surface motions for the 800 000 km2 anatolian region our new 3d velocity and strain rate fields illuminate deformation patterns dominated by westward motion of anatolia relative to eurasia localized strain accumulation along the north and east anatolian faults and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western anatolia we show that automatically processed sentinel 1 insar data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions these results are important for assessing the relationship between strain accumulation and release in earthquakes