dislocation models of interseismic deformation in the western united states 1 the gps derived crustal velocity field of the western united states is used to construct dislocation models in a viscoelastic medium of interseismic crustal deformation the interseismic velocity field is constrained by 1052 gps velocity vectors spanning the 2500 km long plate boundary zone adjacent to the san andreas fault and cascadia subduction zone and extending 1000 km into the plate interior the gps data set is compiled from u s geological survey campaign data plate boundary observatory data and the western u s cordillera velocity field of bennett et al 1999 in the context of viscoelastic cycle models of postearthquake deformation the interseismic velocity field is modeled with a combination of earthquake sources on 100 known faults plus broadly distributed sources models that best explain the observed interseismic velocity field include the contributions of viscoelastic relaxation from faulting near the major plate margins viscoelastic relaxation from distributed faulting in the plate interior as well as lateral variations in depth averaged rigidity in the elastic lithosphere resulting rigidity variations are consistent with reduced effective elastic plate thickness in a zone a few tens of kilometers wide surrounding the san andreas fault saf system primary deformation characteristics are captured along the entire saf system eastern california shear zone walker lane the mendocino triple junction the cascadia margin and the plate interior up to 1000 km from the major plate boundaries

itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

estimation of strain distribution using gps measurements in the kumaun region of lesser himalaya abstract the continuous process of continent continent collision between the indian and the eurasian plates has led to the formation of the himalayan range and continuously caused earthquakes in the region large earthquakes with magnitudes of 8 and above occur in this region infrequently releasing the elastic strain accumulated over years around the plate boundary geodetic measurements can help estimate the strain distribution along the fault system these measurements provide information on active deformations and associated potential seismic hazards along the himalayan arc in order to understand the present deformation around the plate boundary we collected gps data during three campaigns in the years of 2005 2007 at 16 sites in the kumaun region of the lesser himalaya horizontal velocity vectors estimated in itrf2000 are found to be in the range of 41 50 mm yr with an uncertainty level of the order of 1 mm yr the velocity field indicates that the present convergence of around 15 mm yr takes place in the kumaun himalaya further we estimate the strain components in the study area for understanding the currently active tectonic process in the region the estimated dilatational strain indicates that the northern part near the main central thrust mct is more compressional than the southern part maximum shear strain is mostly accommodated in the northern part too the maximum shear and dilatational strain rates are about 1 0 and 0 5 strain yr it is seen that the distribution of high shear strain spatially correlates with seismicity the maximum of extensional and compressional strains due to the force acting along the main central thrust mct in the nw se direction are found to be 0 4 and 0 1 strain yr respectively the maximum shear strain in the northern part of the himalaya appears to be associated with the convergence of the region proposed by other geophysical studies

imprint of the north american plate in siberia revealed by gps 1 gps observations in east siberia combined with global observations collected 1995 2002 place constraints on the geometry and motions of the eurasian north american and pacific plates in east asia by comparing velocities relative to eurasia and to north america we conclude that east siberia to the east of the cherskiy range belongs to the north american plate hypothesized for three decades but not proven because of uncertainties with the plate boundary arising from the ambiguous seismicity smaller plates in east asia such as okhotsk and amurian can neither be resolved nor excluded by the gps velocities

oil oil and oil source rock correlations in the carpathian foredeep and overthrust south east poland abstract the chemical composition of 35 crude oils and the extracts of potential source rock samples from south east poland were studied in detail by geochemical methods in order to understand their genetic relationships twenty six oils including three seep samples were collected from cretaceous to oligocene reservoirs within the carpathian overthrust nine oils originated from carboniferous to miocene reservoirs within the carpathian foredeep the rock samples studied were selected after rock eval pyrolysis screening of a large suite of samples and consist of one lower cretaceous sample and five oligocene menilite shale samples from three different outcrop locations all within the carpathian overthrust geochemical fingerprinting indicates at least two families of crude oils the first represented only by one oil has no specific characteristics except for a light carbon isotope composition the second family is characterized by the presence of 28 30 dinor hopane oleanane and a highly branched isoprenoid c25 alkane within this latter family four subfamilies were recognized a 19 oils having the aforementioned characteristics b seven oils similar to subfamily a but with a relatively high sulphur content c one oil with high abundance of higher plant derived triterpanes and d seven oils with abundant 28 30 dinor hopane although maturity influences the relative abundance of 28 30 dinor hopane it suggested that subfamilies a b and c had an initial low 28 30 dinor hopane content whereas subfamily d an initial high 28 30 dinor hopane content only one oil of subfamily a could potentially be a high maturity counterpart of subfamily d a palaeozoic source rock is suggested for the first family and the second family including the majority of the pils from the carpathian foredeep is most likely derived from the oligocene menilite shales an oil source rock relationship with the menilite shale is supported by the presence although not in all samples studied of 28 30 dinor hopane oleanane or its precursors and the highly branched isoprenoid alkane the strong facies variations observed within this shale gave rise to the different types of crude oils in the second family

combined effects of tectonics and glacial isostatic adjustment on intraplate deformation in central and northern europe applications to geodetic baseline analyses 6 1 we use a suite of spherical thin sheet finite element model calculations to investigate 7 the pattern of horizontal tectonic deformation within europe the calculations incorporate 8 the effects of africa eurasia convergence atlantic ridge push forces and changes 9 in the lithospheric strength of the east european and mediterranean subdomains these 10 predictions are compared to the deformation computed for the same region using a 11 spherically symmetric self gravitating viscoelastic earth model of glacial isostatic 12 adjustment the radial viscosity profile and ice history input into the gia model are taken 13 from a model that best fits three dimensional crustal velocities estimated from the 14 bifrost fennoscandian gps network the comparison of the tectonic and gia signals 15 includes predictions of both crustal velocity maps and baseline length changes associated 16 with sites within the permanent itrf2000 and bifrost gps networks our baseline 17 analysis includes reference sites in northern and central europe that are representative of 18 sites at the center edge and periphery of the gia induced deformation baseline length 19 change predictions associated with all three reference sites are significantly impacted 20 by both tectonic and gia effects albeit with distinct geometric sensitivities in this regard 21 several of our tectonic models yield baseline rates from vaas onsala and potsdam to sites 22 below 55 n which are consistent with observed trends we find that a best fit to the 23 itrf2000 data set is obtained by simultaneously considering the effects of gia plus 24 tectonics where the latter is modeled with a relatively weak mediterranean subdomain in 25 this case the tectonic model contributes to the observed shortening between onsala 26 potsdam and sites to the south without corrupting the extension observed for baselines 27 extending from these reference sites and sites to the north this extension is well reconciled 28 by the gia process alone index terms 1208 geodesy and gravity crustal movements 29 intraplate 8110 3210 mathematical geophysics modeling 8110 tectonophysics continental tectonics 30 general 0905 9335 information related to geographic region europe keywords tectonics gia 31 intraplate deformation

biomarker distributions in australian oils predominantly derived from terrigenous source material oils found in many australian sedimentary basins contain a relatively high input of terrigenous organic source material a study of a large number of these oils has permitted a number of biomarker distributions to be determined that appear to be characteristic for oils derived from terrigenous source material these features include the presence of sesquiterpanes absence of tricyclic terpanes relatively high concentrations of a c24 tetracyclic terpane predominance of c29 steranes presence of two unidentified c27 and c30 terpanes and virtual absence of 18 h oleanane the latter observation is significant since it appears that 18 h oleanane appears only in oils of tertiary age derived from terrigenous source material an attempt has also been made to compare the results for the australian oils with published results for oils derived from terrigenous source material in other parts of the world the number of reports in the literature for these oils is fairly limited but it appears that some of the observations for the australian oils can be extended to them this study is an initial attempt to devise a classification scheme that can be used to determine the origin of an oil unambiguously from biomarker parameters in order for this approach to be successful a relatively large number of biomarker parameters need to be assigned as characteristic of a particular type of source material

hydrological flowpaths and nitrate removal rates within a riparian floodplain along a fourth order stream in brittany france three main reservoirs were identified that contribute to the shallow subsurface flow regime of a valley drained by a fourth order stream in brittany western france i an upland flow that supplied a wetland area mainly during the high water period it has high n no3 and average cl concentrations ii a deep confined aquifer characterized by low nitrate and low chloride concentrations that supplied the floodplain via flow upwelling iii an unconfined aquifer under the riparian zone with high cl and low n no3 concentrations where biological processes removed groundwater nitrate this aquifer collected the upland flow and supplied a relict channel that controlled drainage from the whole riparian zone patterns of n no3 and cl concentrations along riparian transects together with calculated high nitrate removal indicate that removal occurred mainly at the hillslope riparian zone interface i e first few metres of wetland whereas dilution occurred in lower parts of the transects especially during low water periods and at the beginning of recharge periods stream flow was modelled as a mixture of water from the three reservoirs an estimation of these contributions revealed that the deep aquifer contribution to stream flow averaged 37 throughout the study period while the contribution of the unconfined reservoir below the riparian zone and hillslope flow was more variable from ca 6 to 85 relative to rainfall events and the level of the riparian water table at the entire riparian zone scale no3 removal probably from denitrification appeared most effective in winter despite higher estimated upland no3 fluxes entering the riparian zone during this period copyright 2003 john wiley sons ltd

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

india and sunda plates motion and deformation along their boundary in myanmar determined by gps using a regional gps data set including 190 stations in asia from nepal to eastern indonesia and spanning 11 years we update the present day relative motion between the indian and sundaland plates and discuss the deformation taking place between them in myanmar revisiting measurements acquired on the main boundary thrust in nepal it appears that points in southern nepal exhibit negligible deformation with respect to mainland india including these points using a longer time span than previous studies and making an accurate geodetic mapping in the newest reference frame allows us to refine the present day indian motion our results confirm that the current motion of india is slower than predicted by the nuvel 1a model and in addition our india eurasia motion is significantly 5 mm yr slower than previous geodetic determinations this new indian motion combined with a refined determination of the sundaland motion gives way to a relative india sunda angular velocity of 20 2 n 26 1 e 0 370 myr in itrf2000 predicting a relative motion of 35 mm yr oriented n10 at the latitude of myanmar there the sagaing fault accommodates only 18 mm yr of right lateral strike slip only half of the shear component of motion we present two models addressing how and where the remaining deformation may occur a first model of distributed deformation implies convergence on the arakan subduction the northern continuation of the now famous sumatra andaman trench and wrench faulting in the arakan wedge the second model uses localized deformation where deformation observed west of the sagaing fault is entirely due to elastic loading on a faster and oblique arakan subduction 23 mm yr this latter model predicts that a major earthquake of mw 8 5 may occur every century on this segment of the subduction

interplate locking condition derived from seafloor geodetic data at the northernmost part of the suruga trough japan we observed seafloor crustal deformation at two observation sites on opposite sides of the suruga trough off japan from 2005 to 2011 to investigate the interplate locking condition at the source region of the anticipated great subduction earthquake named tokai earthquake we estimated the displacement velocity vectors relative to the amurian plate on the basis of repeated observations our results at the two points suruga northeast and suruga northwest snw were 42 8 mm yr toward n94 3 w and 39 11 mm yr toward n84 9 w respectively these directions are the same as those measured at on land gps stations the magnitudes of the velocity vectors indicate a significant shortening of approximately 4 mm yr between snw and on land gps stations located to the west of the suruga trough the results show that the plate interface is strongly locked no slip shallower than the source region of the anticipated tokai earthquake

glacial isostatic adjustment observed using very long baseline interferometry and satellite laser ranging geodesy in global space geodetic solutions radial site motions are usually estimated relative to the geocenter the center of figure of the solid earth most geodesists estimate the motion of the geocenter assuming both that sites do not move radially and that sites move laterally as predicted by plate motion model nuvel 1a demets et al 1990 1994 here we estimate the motion of the geocenter assuming that the plate interiors deform radially and laterally as predicted by the postglacial rebound model of peltier 1994 or that of peltier 1996 without assuming a priori knowledge about relative plate motion radial site motions estimated relative to this rebound adjusted geocenter are in the same reference frame as the rebound model predictions whereas site motions estimated without adjusting for rebound are not we further constrain the motion of the rebound adjusted geocenter using satellite laser ranging s sensitivity to the center of mass of the solid earth the oceans and the atmosphere by assuming that the mean velocity between the rebound adjusted geocenter and the center of mass is negligible over the time period of geodetic measurement twenty years of observation with satellite laser ranging and very long baseline interferometry record the isostatic response of the solid earth to the unloading of the late pleistocene ice sheets the misfits of the postglacial rebound model of peltier 1994 and that of peltier 1996 are 34 and 16 less respectively than the misfit of the rigid plate model sites at onsala sweden and algonquin park ontario are observed to be rising at 3 mm yr and 2 mm yr respectively reflecting unloading of the fennoscandian and laurentide ice sheets sites along the east coast of the united states are subsiding at 2 mm yr indicating that the forebulge produced by the laurentide ice sheet is currently collapsing very slowly sites beneath the margins of the ice sheets during the last glacial maximum are currently moving laterally away from the ice sheet centers at 1 5 mm yr in disagreement with the moderately fast outward motion predicted by the model of peltier 1996

first global positioning system results in northern myanmar constant and localized slip rate along the sagaing fault we present the first recorded global positioning system gps data from myanmar measured at the northern tip of the sagaing fault this area is in a very complex geodynamic context where rigid and semirigid plates interact the 12 gps sites measured in 2005 and 2008 in northern myanmar show that the slip rate is 18 mm yr and is localized along a single active narrow fault trace 20 km wide the same rate was previously demonstrated and remeasured 500 km southward in central myanmar despite the geodynamic regional complexity induced by interaction between the sunda and india plates the burma microplate and the highly deformable eastern himalayan syntaxis the slip rate remains surprisingly constant along this fault however the modeled locking depth varies from 20 km in central myanmar to 5 km in the north

correlation of nitrate profiles with groundwater and sediment characteristics in a shallow sandy aquifer abstract sediment profiles of a shallow sandy aquifer in an agricultural area of denmark can be characterized by a new term called total reduction capacity trc quantifying the total amount of reduced compounds in the aquifer material ferrous iron reduced sulfur compounds solid organic carbon a distinct increase of trc was observed at and below the oxidation reduction front in this study the front was a zone 30 cm wide oxygen nitrate and sulfate were present above the oxidation reduction front but disappeared at the front detailed porewater profiles indicate that denitrification also takes place above the front supposedly in anaerobic microenvironments not evident in the water samples from the small wells the trc profiles showed that some reduction capacity is still present above the oxidation reduction front and is apparently able to support denitrification

itrf2000 a new release of the international terrestrial reference frame for earth science applications 1 for the first time in the history of the international terrestrial reference frame the itrf2000 combines unconstrained space geodesy solutions that are free from any tectonic plate motion model minimum constraints are applied to these solutions solely in order to define the underlying terrestrial reference frame trf the itrf2000 origin is defined by the earth center of mass sensed by satellite laser ranging slr and its scale by slr and very long baseline interferometry its orientation is aligned to the itrf97 at epoch 1997 0 and its orientation time evolution follows conventionally that of the no net rotation nnr nuvel 1a model the itrf2000 orientation and its rate are implemented using a consistent geodetic method anchored over a selection of itrf sites of high geodetic quality ensuring a datum definition at the 1 mm level this new frame is the most extensive and accurate one ever developed containing about 800 stations located at about 500 sites with better distribution over the globe compared to past itrf versions but still with more site concentration in western europe and north america about 50 of station positions are determined to better than 1 cm and about 100 sites have their velocity estimated to at or better than 1 mm yr level the itrf2000 velocity field was used to estimate relative rotation poles for six major tectonic plates that are independent of the trf orientation rate a comparison to relative rotation poles of the nuvel 1a plate motion model shows vector differences ranging between 0 03 and 0 08 m y equivalent to approximately 1 7 mm yr over the earth s surface itrf2000 angular velocities for four plates relative to the pacific plate appear to be faster than those predicted by the nuvel 1a model the two most populated plates in terms of space geodetic sites north america and eurasia exhibit a relative euler rotation pole of about 0 056 0 005 m y faster than the pole predicted by nuvel 1a and located about 10 n 7 e more to the northwest compared to that model

external validation of the grace ggm01c gravity field using gps and doris positioning results 1 we have used the new gravity field model ggm01c derived from grace data to reanalyze doris data from 1993 0 to 2003 2 using the gipsy oasis software and a free network approach we have estimated the position and velocity of each doris station in itrf2000 in order to test the accuracy of these results we have compared them to the positions and velocities of 43 collocated gps stations using local ties and covariance information doris results computed using the ggm01c gravity field instead of the egm96 gravity field show a significantly improved external agreement with gps position agreement of 12 26 mm was reduced to 10 13 mm and velocity agreement of 3 3 3 7 mm yr was reduced to 2 4 3 3 mm yr this can be interpreted as an external test of the accuracy of the new ggm01c gravity field

a new velocity field for africa from combined gps and doris space geodetic solutions contribution to the definition of the african reference frame afref 1 we analyzed 16 years of gps and 17 years of doppler orbitography and radiopositioning integrated by satellite doris data at continuously operating geodetic sites in africa and surroundings to describe the present day kinematics of the nubian and somalian plates and constrain relative motions across the east african rift the resulting velocity field describes horizontal and vertical motion at 133 gps sites and 9 doris sites horizontal velocities at sites located on stable nubia fit a single plate model with a weighted root mean square residual of 0 6 mm yr maximum residual 1 mm yr an upper bound for plate wide motions and for regional scale deformation in the seismically active southern africa and cameroon volcanic line we confirm significant southward motion 1 5 mm yr in morocco with respect to nubia consistent with earlier findings we propose an updated angular velocity for the divergence between nubia and somalia which provides the kinematic boundary conditions to rifting in east africa we update a plate motion model for the east african rift and revise the counterclockwise rotation of the victoria plate and clockwise rotation of the rovuma plate with respect to nubia vertical velocities range from 2 to 2 mm yr close to their uncertainties with no clear geographic pattern this study provides the first continent wide position velocity solution for africa expressed in international terrestrial reference frame itrf2008 a contribution to the upcoming african reference frame afref except for a few regions the african continent remains largely under sampled by continuous space geodetic data efforts are needed to augment the geodetic infrastructure and openly share existing data sets so that the objectives of afref can be fully reached

current plate velocities relative to the hotspots incorporating the nuvel 1 global plate motion model nuvel 1 is a new global model of current relative plate velocities demets et al 1990 which differ significantly from those of prior models here we incorporate nuvel 1 into hs2 nuvel1 a new global model of plate velocities relative to the hotspots hs2 nuvel1 was determined from the hotspot data and errors used by minster and jordan 1978 to determine am1 2 which is their model of plate velocities relative to the hotspots am1 2 is consistent with minster and jordan s relative plate velocity model rm2 here we compare hs2 nuvel1 with am1 2 and examine how their differences relate to differences between nuvel 1 and rm2 hs2 nuvel1 plate velocities relative to the hotspots are mainly similar to those of am1 2 minor differences between the two models include the following 1 in hs2 nuvel1 the speed of the partly continental apparently non subducting indian plate is greater than that of the purely oceanic subducting nazca plate 2 in places the direction of motion of the african antarctic arabian australian caribbean cocos eurasian north american and south american plates differs between models by more than 10 3 in places the speed of the australian caribbean cocos indian and nazca plates differs between models by more than 8 mm yr although 27 of the 30 rm2 euler vectors differ with 95 confidence from those of nuvel 1 only the am1 2 arabia hotspot and india hotspot euler vectors differ with 95 confidence from those of hs2 nuvel1 thus substituting nuvel 1 for rm2 in the inversion for plate velocities relative to the hotspots changes few euler vectors significantly presumably because the uncertainty in the velocity of a plate relative to the hotspots is much greater than the uncertainty in its velocity relative to other plates

interseismic plate coupling and strain partitioning in the northeastern caribbean summary the northeastern caribbean provides a natural laboratory to investigate strain partitioning its causes and its consequences on the stress regime and tectonic evolution of a subduction plate boundary here we use gps and earthquake slip vector data to produce a present day kinematic model that accounts for secular block rotation and elastic strain accumulation with variable interplate coupling on active faults we confirm that the oblique convergence between caribbean and north america in hispaniola is partitioned between plate boundary parallel motion on the septentrional and enriquillo faults in the overriding plate and plateboundary normal motion at the plate interface on the northern hispaniola fault to the east the caribbean north america plate motion is accommodated by oblique slip on the faults bounding the puerto rico block to the north puerto rico subduction and to the south muertos thrust with no evidence for partitioning the spatial correlation between interplate coupling strain partitioning and the subduction of buoyant oceanic asperities suggests that the latter enhance the transfer of interplate shear stresses to the overriding plate facilitating strike slip faulting in the overriding plate the model slip rate deficit together with the dates of large historical earthquakes indicates the potential for a large m w7 5 or greater earthquake on the septentrional fault in the dominican republic similarly the enriquillo fault in haiti is currently capable of a m w7 2 earthquake if the entire elastic strain accumulated since the last major earthquake was released in a single event today the model results show that the puerto rico lesser antilles subduction thrust is only partially coupled meaning that the plate interface is accumulating elastic strain at rates slower than the total plate motion this does not preclude the existence of isolated locked patches accumulating elastic strain to be released in future earthquakes but whose location and geometry are not resolvable with the present data distribution slip deficit on faults from this study are used in a companion paper to calculate interseismic stress loading and together with stress changes due to historical earthquakes derive the recent stress evolution in the ne caribbean

land motion estimates from gps at tide gauges a geophysical evaluation summary space geodesy applications have mainly been limited to horizontal deformations due to a number of restrictions on the vertical component accuracy monitoring vertical land motion is nonetheless of crucial interest in observations of long term sea level change or postglacial rebound measurements here we present a global vertical velocity field obtained with more than 200 permanent gps stations most of them colocated with tide gauges tgs we used a state of the art homogeneous processing strategy to ensure that the reference frame was stable throughout the observation period of almost 10 yr we associate realistic uncertainties to our vertical rates taking into account the time correlation noise in the time series the results are compared with two independent geophysical vertical velocity fields 1 vertical velocity estimates using long term tg records and 2 postglacial model predictions from the ice 5g vm2 adjustment the quantitative agreement of the gps vertical velocities with the internal estimates of vertical displacements using the tg record is very good with a mean difference of 0 13 1 64 mm yr 1 on more than 100 sites for 84 per cent of the gps stations considered the vertical velocity is confirmed by the tg estimate to within 2 mm yr 1 the overall agreement with the glacial isostatic adjustment gia model is good with discrepancy patterns related either to a local misfit of the model or to active tectonics for 72 per cent of the sites considered the predictions of the gia model agree with the gps results to within two standard deviations most of the gps velocities showing discrepancies with respect to the predictions of the gia model are however consistent with previously published space geodesy results we in turn confirm the value of 1 8 0 5 mm yr 1 for the 20th century average global sea level rise and conclude that gps is now a robust tool for vertical land motion monitoring which is accurate at least at 1 mm yr 1

crustal deformation measurements in guerrero mexico 1 gps measurements of crustal deformation in guerrero southern mexico include surveys collected between 1992 and 2001 as well as continuous gps measurements at a few sites these geodetic observations are used to calculate interseismic deformation rates and assess the presence and possible location of transient deformation during the period encompassing 1992 25 to 2001 75 the data are used to examine transient deformation in 1998 previously described from data at a single site by lowry et al 2001 survey measurements and continuous data from a site near popocatepetl volcano confirm the 1998 transient and survey data also suggest another transient occurred following the 14 september 1995 mw 7 3 copala earthquake all of the available gps position estimates have been inverted for a combined model of slip during each event plus the steady state slip on the plate interface modeling of the steady state deformation rates confirms that the guerrero seismic gap is partially frictionally locked at depths shallower than about 25 km and accumulating strain that may eventually be released in a great earthquake the data also suggest that there is frictional coupling to much greater 40 km depths which releases more frequently in aseismic slip events the locations and sizes of the transient events are only partially constrained by the available data however the transient models which best fit the gps coordinate time series suggest that aseismic slip was centered downdip of the seismogenic portion of the plate bounding thrust in both events and the moment release had equivalent magnitudes mw 7 1 1 3 1 0 in 1995 1996 and 7 1 0 4 0 1 in 1998

using global positioning system derived crustal velocities to estimate rates of absolute sea level change from north american tide gauge records 1 we identified 37 tide gauges each located within 40 km of a geodetic station whose international terrestrial reference frame of 2000 itrf2000 crustal velocity had been rigorously derived from continuous global positioning system gps observations spanning from 3 to 11 years the tide gauges are located along the coasts of north america bermuda hawaii and kwajalein in the marshall islands we obtained the itrf2000 crustal velocities by averaging values from six solutions each produced by a team of investigators acting essentially independently of the other teams we then applied crustal velocities to convert rates of relative sea level change to rates of absolute sea level change in a sample containing 30 sites we found that the mean rate of absolute sea level change equals 1 80 0 18 mm yr in the 1900 1999 period the scatter about the mean for individual sites in this sample is characterized by a weighted rms value of 0 85 mm yr this scatter primarily reflects the uncertainty associated with derived crustal velocities the remaining seven sites i e five sites on the pacific coast of alaska one on dauphin island alabama and one on kwajalein an atoll in the pacific ocean experienced relatively low rates of absolute sea level change we hypothesize the low rates in alaska are caused by ongoing melting of mountain glaciers and ice masses near the stations while the low rates found for dauphin island and kwajalein remain unexplained

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

application of a ramp flat fault model to interpretation of the naga thrust and possible implications for petroleum exploration along the naga thrust front the assam arakan thrust belt extends along the india myanmar border from the chinese border on the north to the bay of bengal on the south tertiary nonmarine sediments dominate the stratigraphy within the frontal zone of this fold and thrust belt thrust fault flats occur in the upper barail group coaly interval and ramps are localized by preexistent normal faults and stratigraphic discontinuities as a result the frontal zone of the thrust belt is characterized by multiscale imbricate structures the jaipur anticline occurs at the foreland edge of the naga thrust imbricate zone at the northeastern end of the assam valley application of flat ramp geometric models with a limited data set from the jaipur anticline allows creation of geometrically viable models for interpreting the general structure of the jaipur anticline and for developing hydrocarbon exploration leads the results of this method indicate that 1 the proven productive foreland trend extends several kilometers beneath the naga thrust and 2 zones of high dip in the thrust belt mark the location of prospect leads probably related to local thrust imbrication the method provides a testable process of identifying prospective areas therefore it can minimize exploration expense and optimize exploration planning

secular variation of the geocenter the degree 1 deformations of earth induced by a surface load are computed in a reference frame related to the center of mass of the planet using a theoretical approach love number formalism at secular timescale where earth has a viscoelastic behavior the temporal variation of the coordinates of the geocenter induced by the pleistocenic deglaciation is investigated for two loading histories three ice sheets with the same time dependence or ice 3g model testing different viscosity profiles within the mantle the present day secular variation of earth s geocenter induced by postglacial rebound is found to be from 0 2 up to 0 5 mm yr and consequently we suggest that observations from space geodesy of this rate could be used to constrain the viscosity contrast between upper and lower mantle

geophysical interpretation of observed geocenter variations geocenter variations are caused by mass redistribution within the earth system especially the atmosphere oceans and continental water using surface pressure fields and soil moisture and snow depth fields of the ncep ncar climate data assimilation system i cdas i 1 we estimate contributions from variations in atmospheric surface pressure and continental water storage to the earth s geocenter center of mass variation in addition sea surface anomalies determined by the topex poseidon altimeter are used to investigate geocenter variations resulting from ocean mass redistribution these sea surface height data were corrected using a simplified steric model a comparison with observed geocenter variations derived from lageos 1 and 2 satellite laser ranging data indicates that the atmosphere oceans and continental hydrological cycle all provide significant contributions at different frequencies geocenter variations estimated in this paper are in reasonably good agreement with results given by dong et al 1997 for atmospheric and ocean contributions but not for the estimates of continental hydrological contributions

uncertainty in the velocity between the mass center and surface of earth 1 using spectral analysis and data decimation we estimate the uncertainty in the velocity between the cumulative mass center of earth cm and geodetic sites on earth s surface knowing this velocity is crucial for evaluating space geodetic observations of continental uplift and subsidence in terms of postglacial rebound and sea level rise we find slr observations of satellite lageos to constrain the x and y components of the velocity of cm to 0 4 mm yr and the z component to 0 9 mm yr 95 confidence limits x is in the direction of 0 n0 e y of 0 n9 0 e and z of 90 n the uncertainty in z is high so that the estimate includes the independent inference made jointly using site velocities the rigid plate hypothesis and models of postglacial rebound that the true velocity of cm has a z component of 0 5 1 0 mm yr relative to that in itrf2008 uncertainty in scale rate an intermediate parameter in the determination of an itrf is 0 36 mm yr for vlbi 0 52 mm yr for slr and 0 20 mm yr for gps the scale of gps depends on that of vlbi and slr but the low gps uncertainty indicates that gps results are for the first time unbiased by changing satellite block types evidently due to newly incorporated satellite phase center variations gps constrains the velocity of cm nearly as well as slr representing a technical advance given that a gps satellite is not a sphere and responds strongly to solar radiation pressure citation argus d f 2012 uncertainty in the velocity between the mass center and surface of earth j geophys res 117 b10405 doi 10 1029 2012jb009196

origin of the international terrestrial reference frame 1 with recent improvements in space geodesy the earth s center of mass cm and center of figure cf are no longer indistinguishable the current origin of the international terrestrial reference frame itrf is defined as the cm which shows measured seasonal variations of several millimeters to 1 cm with respect to true cm as scientists study earth s dynamic deformations on seasonal and shorter timescales and begin to compare observed geocenter motion with predictions from geophysical models the reference frame origin presents significant error due to missing the geocenter motion this paper discusses the nature of the origin of the itrf and explores the sensitivity of gps measurements to geocenter motion we find that since the values of nonlinear geocenter motion are not included in the positions of the itrf sites the behavior of the current itrf origin reflects cm on secular timescale but reflects cf on seasonal and short timescales the nature of the itrf origin depends on both the adopted kinematic model and unmodeled network motion the realized itrf origin should be defined by a new nomenclature to reflect its nature accurately by the new nomenclature the origin will maintain its current long term stability while improving its stability on seasonal timescales to the submillimeter level with the degree 1 deformation approach gps measurements are able to provide potentially valuable information on geocenter variations on seasonal and short timescales

distribution of the right lateral strike slip motion from the main recent fault to the kazerun fault system zagros iran evidence from present day gps velocities article i nfo gps measurements across the kazerun fault system in the zagros mountain belt provide first instantaneous velocities on the different segments these results are closely consistent with the geological fault slip rates over 150 ka implying stable velocities over a longer period the present day strike slip motion is distributed from the main recent fault to the n trending kazerun fault system along a preferential en echelon fault zone included in a more distributed fan shape fault pattern the hormuz salt decoupling layer cannot be the only cause of a sedimentary spreading because seismicity attests these faults are rooted in the basement the dena fault 3 7 mm yr transfers the mrf fault slip mainly to the kazerun 3 6 mm yr and slightly to the high zagros and sabz pushan faults 1 5 mm yr and the kazerun fault further to the kareh bas fault 3 4 mm yr total geological horizontal offsets associated with gps slip rates help inferring precise fault slip onset ages the successive onsets deduced by this approach imply that the right lateral strike slip activity of the mrf has propagated in time southeastward to the dena segment and then to the kazerun segment and to the kareh bas fault

improved identification of pay zones through integration of geochemical and log data a case study from upper assam basin india the upper paleocene lower eocene clastic reservoirs constitute one of the most important hydrocarbon producing horizons in the upper assam basin of northeast india these reservoirs are characterized by the presence of 1 normal gravity oil 23 31 api 2 low to intermediate gravity oil 13 23 api and 3 gas and light oil condensate 31 api the sandstone reservoirs show complex wire line log signatures which are commonly misleading the main impediments to understanding the nature of reservoir fluid include 1 distinguishing low gravity intermediate gravity and normal gravity oil bearing zones and 2 resolving the problem of density rhob neutron porosity nphi crossover for gas bearing as well as oil bearing reservoirs geochemical analyses of sidewall core extracts by thin layer chromatography with flame ionization detection tlc fid and gas chromatography gc provide valuable cost effective input for reservoir fluid characterization the important parameters needed to identify the nature and composition of the reservoir fluid include 1 the bulk composition of the sidewall core extract i e saturated hydrocarbons aromatic hydrocarbons and resins asphaltenes 2 amount of extract in mg g of rock 3 gc fingerprint and 4 the ratio of pristane to n c17 these parameters integrated with geological and geophysical wire line logs evidence yield more accurate and reliable formation evaluation criteria the technique is simple and inexpensive and may find application as an additional formation evaluation tool in any geological setting

heterogeneous coupling of the sumatran megathrust constrained by geodetic and paleogeodetic measurements geodetic and paleogeodetic measurements of interseismic strain above the sumatran portion of the sunda subduction zone reveal a heterogeneous pattern of coupling annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century and repeated gps surveys between 1991 and 2001 and continuous measurements at gps stations operated since 2002 provide horizontal velocities near the equator the megathrust is locked over a narrow width of only a few tens of kilometers in contrast the locked fault zone is up to about 175 km wide in areas where great interplate earthquakes have occurred in the past formal inversion of the data reveals that these strongly coupled patches are roughly coincident with asperities that ruptured during these events the correlation is most spectacular for rupture of the m w 8 7 nias simeulue earthquake of 2005 which released half of the moment deficit that had accumulated since its previous rupture in 1861 suggesting that this earthquake was overdue beneath the mentawai islands strong coupling is observed within the overlapping rupture areas of the great earthquakes of 1797 and 1833 the accumulated slip deficit since these events is slowly reaching the amount of slip that occurred during the 1833 earthquake but already exceeds the slip that occurred during the 1797 earthquake thus rerupture of part of the mentawai patch in september 2007 was not a surprise in contrast coupling is low below the batu islands near the equator and around enggano island at about 5 s where only moderate earthquakes m w 8 0 have occurred in the past two centuries the correlation of large seismic asperities with patches that are locked during the interseismic period suggests that they are persistent features this interpretation is reinforced by the fact that the large locked patches and great ruptures occur beneath persistent geomorphologic features the largest outer arc islands depth and convergence rate dependent temperature might influence the pattern of coupling through its effect on the rheology of the plate interface but other influences are required to account for the observed along strike heterogeneity of coupling in particular subduction of the investigator fracture zone could be the cause for the low coupling near the equator

the paleogene vegetation and petroleum system in the tropics a biomarker approach abstract the present study investigates the biomarker signatures of sediments and crude oils to infer the paleovegetation from the two petroleum systems of assam basin eastern india they are classified as the paleocene middle eocene and the middle eocene oligocene petroleum systems the sediments are oil and gas prone with an early catagenetic stage of thermal evolution here we report tricyclic diterpanes such as rimuane pimarane rosane and isopimarane along with tetracyclic diterpanes ent beyerane phyllocladane kaurane from paleocene eocene coal bearing sediments and crude oils these diterpane biomarkers attest dominant contribution from conifers possibly from podocarpaceae and araucariaceae however diterpanes are not detected in oligocene sediments and oils crude oils from both paleocene eocene and oligocene reservoirs and organic rich sediments contain angiosperm biomarkers such oleanane and related triterpanes along with bicadinane a biomarker specific for the dipterocarpaceae family of angiosperms the equatorial position of india during early paleogene along with the presence of angiosperm signatures including dipterocarpaceae and gymnosperms reflect the emergence of tropical rainforest elements in eastern india absence of diterpenoids in oligocene samples and difference in angiosperm parameters from paleocene eocene samples suggests a change in source vegetation and organofacies

tests of the rigid plate hypothesis and bounds on intraplate deformation using geodetic data from very long baseline interferometry the geodetic results of ma et al 1994 from very long baseline interferometry are used to assess rates of intraplate deformation we analyze the resulting set of velocities of 18 plate interior sites nine on the north american plate four western european sites on the eurasian plate three on the pacific plate and two on the australian plate we formulate three alternative error budgets based partly on the work of ryan et al 1993a an optimistic error budget a conservative error budget and an upper bound error budget all three budgets assume the existence of a previously unmodeled error that is inversely proportional to the time span of observations at a site use of the conservative error budget indicates no significant motion between sites on any one of the four plates use of the upper bound error budget designed to be precisely large enough to be consistent with rigid plates places a usefully small upper bound on how fast any site might be moving relative to the rest of its plate speeds faster than 2 mm yr are excluded at the 95 confidence level for seven of the 18 plate interior sites adjustments of the site velocities for motion due to postglacial rebound as predicted from the model of tushingham and peltier 1991 give an insignificant improvement to the fit of the horizontal velocities to the rigid plate model the velocities of six sites near the western margin of the interior of the north american plate were also analyzed use of the conservative error budget indicates that a site near fairbanks alaska has an upper bound of 3 mm yr on its speed a site in nome alaska has an upper bound on its speed of 8 mm yr and a site in penticton british columbia has an upper bound on its speed of 4 mm yr of three sites on the colorado plateau two move marginally significantly and one moves insignificantly relative to stable north america upper limits on their speeds relative to stable north america range from 4 to 5 mm yr we conclude that the data do not yet demonstrate significant velocities between sites in the stable interior of any one plate but do provide useful and small upper bounds of 2 mm yr or less on the speeds of the best observed intraplate sites six sites near the western margin of the north american interior have upper bound speeds of 3 to 8 mm yr

nitrate in groundwater and water sources used by riparian trees in an agricultural watershed a chemical and isotopic investigation in southern minnesota this study evaluates processes that affect nitrate concentrations in groundwater beneath riparian zones in an agricultural watershed nitrate pathways in the upper 2 m of groundwater were investigated beneath wooded and grass shrub riparian zones next to cultivated fields because trees can be important components of the overall nitrate pathway in wooded riparian zones water sources used by riparian trees and possible effects of trees on nitrate concentrations in groundwater were also investigated average nitrate concentrations in shallow groundwater beneath the cultivated fields were 5 5 mg l upgradient of the wooded riparian zone and 3 5 mg l upgradient of the grass shrub zone shallow groundwater beneath the fields passed through the riparian zones and discharged into streams that had average nitrate concentrations of 8 5 mg l as n lateral variations of d values in groundwater showed that mixing among different water sources occurred beneath the riparian zones in the wooded riparian zone nitrate concentrations in shallow groundwater were diluted by upwelling nitrate poor deep groundwater upwelling deep groundwater contained ammonium with a 15n of 5 that upon nitrification and mixing with nitrate in shallow groundwater caused nitrate 15n values in shallow groundwater to decrease by as much as 19 5 stream water penetrated laterally beneath the wooded riparian zone as far as 19 m from the stream s edge and beneath the grass shrub zone as far as 27 m from the stream s edge nitrate concentrations in shallow groundwater immediately upgradient of where it mixed with stream water averaged 0 4 mg l in the wooded riparian zone and 0 8 mg l near the grass shrub riparian zone nitrate concentrations increased toward the streams because of mixing with nitrate rich stream water because nitrate concentrations were larger in stream water than shallow groundwater concentrated nitrate in the streams cannot have come from shallow groundwater at these sites water sources of riparian trees were identified by comparing d values of sap water soil water groundwater and stream water soil water was the main water source for trees in the outer 4 to 6 m of one part of the wooded riparian zone and outer 10 m of another part groundwater was a significant water source for trees closer to the streams where the water table was less than about 2 1 to 2 7 m below the surface no evidence was found in the nitrate concentration profiles that trees close to the streams that took up groundwater through their roots also took up nitrate from groundwater the lack of such evidence is attributed to the nitrate concentration profiles being insufficiently sensitive indicators of nitrate removal by trees

tertiary oils from upper assam basin india a geochemical study using terrigenous biomarkers abstract the upper assam basin in northeast india is a tertiary sub basin of the assam arakan basin hydrocarbons are present in the langpar formation upper palaeocene lakadong member of the sylhet formation lower eocene and the barail oligocene tipam lower miocene and girujan middle miocene formations in the basin a detailed study to understand the nature and origin of the oils from different stratigraphic horizons using terrigenous and other biomarkers has been carried out further the variation in maturities of oils occurring in different stratigraphic horizons has also been studied the study shows that rearranged oleananes oleananes and bicadinanes are present in these oils implying land plant input to their source rocks the oils have been classified into different groups using ratios of rearranged oleananes oleananes bicadinanes and steranes indicating presence of multiple source rocks in the basin with subtle variation in characteristics maturity studies show that oils from younger horizons barail tipam and girujan are more mature than oils from older horizons langpar and lakadong there is an apparent mismatch in maturity of oils as measured by different biomarker maturity parameters this is due to the mixing of two different charges of oils having different maturities and generated from two different source rock kitchens in the same reservoir principal component analysis pca of biomarker data has also been able to classify the oils into various groups a new parameter has been developed using ratios of rearranged oleananes for determining maturity of these oils

potential volcanological applications of the doris system a geodetic study of the socorro island mexico coordinate time series summary we analysed doris data from socorro island mexico providing weekly coordinates in itrf2000 from 1900 to 2006 careful analysis of this time series shows horizontal and vertical movements related to recent activity of the mt evermannn volcano a deflation of the volcano between 1993 and 1996 94 mm yr 1 in the n23 w direction directly pointing in the direction of the crater summit is observed we identify also a clear horizontal discontinuity of 81 mm and a significant change in velocity on 2002 october 3 we use a mogi formalism to provide constraints from our geodetic results on the successive locations and size of the depletion and inflation sources our model is consistent with a deflation source for the period 1993 1996 located beneath mt evermannn at a depth of about 6 2 km below sea level however our data constrain only the azimuth and dip angles of the source which could be located elsewhere along the azimuth of the summit depth and volume varying linearly with the distance

the itrf96 realization and its associated velocity field this text intends to present and to analyse the quality of the new 1996 edition of the international terrestrial reference system called the itrf96 the itrf96 represents a key step forward in the activity of the iers terrestrial system determinations a new physical combination model has been developed as well as a new stochastic model for the first time the level of accuracy has reached 1 cm or better in position for about 50 of itrf96 stations and 30 of the stations have their velocities determined free of any aditional tectonic plate model assumption with an uncertainty better than 3 mm yr the itrf96 also provides a more complete solution a new software has been developed which makes available the itrf96 full variance covariance matrix whereas this information was restricted to station positions in the previous itrf94 edition moreover the network coverage is clearly the largest set of globally distributed terrestrial space geodesy stations that have ever been computed 521 stations located among 290 sites in addition station velocities are also determined at a very accurate level allowing possible determination of kinematic plate motion models free of any geological assumption

the state of toxicity and cause of elevated iron and manganese concentrations in surface water and groundwater around naga thrust of assam arakan basin northeastern india an alarming situation of exceedingly high fe and mn concentrations in both surface water and groundwater has been identified in a tectonically active region located in assam arakan basin of northeast india cross plots pearson correlation principal component analysis and flow net methods were applied to elucidate the present state and possible sources of fe and mn contamination out of 32 water samples collected for the study all of them found exceeding 28 times more for fe and 136 times more for mn than epa limit correlation and cross plots of ph tds ec fe mn cu zn suggest the reduction of both fe hydroxides and mn oxides in redox condition into dissolve states leading to fe and mn elevations in groundwater principal component analysis exhibits three pc factors in which pc1 and pc3 reflected oxidized condition and pc2 reflected reducing environment that controlled fe and mn concentrations the study also revealed that source of high fe and mn contaminations was controlled by groundwater flows water table contour flow net suggests that the chathe river acts as influent stream and supplies elevated fe and mn water into the shallow aquifers baseflow from the discharge areas into low lying areas causes accretion of fe and mn in pond oxbow lake backswamp and shallow aquifers

defining the translational velocity of the reference frame of earth summary earth s centre is fundamental to geodesy and geoscience because motions of sites on the surface are estimated relative to it international terrestrial reference frames itrf2000 and itrf2005 are defined by the centre of mass of earth s system cm consisting of solid earth the ice sheets the oceans and the atmosphere satellite lageos rotates about cm satellite laser ranging slr is used to estimate the velocity of cm relative to sites on the surface however itrf2000 and itrf2005 differ by 1 8 mm yr 1 suggesting that the velocity of cm is constrained poorly by slr in this study we define earth s reference frame with the centre of mass of solid earth ce site velocities estimated using slr vlbi gps and doris are corrected for a postglacial rebound model and inverted for the rotational velocities of the plates and the rotational and translational velocities of the four space techniques because the postglacial rebound predictions are relative to ce the velocity of ce relative to sites on the surface is estimated because the input slr site velocities are relative to cm the output slr translational velocity is the velocity of cm relative to ce the estimated velocity of ce does not depend strongly on the postglacial rebound model corrected for equal within uncertainties and having a root mean square of 0 5 mm yr 1 are estimates of the velocity of ce determined assuming that plate interiors are deforming radially as predicted by three postglacial rebound models and an estimate of the velocity of ce determined assuming that parts of plate interiors neither beneath nor along the margins of the late pleistocene ice sheets are not deforming laterally the velocity of ce equals within uncertainties probability greater than 5 per cent the velocity of cm in itrf2000 the velocity of ce differs significantly 0 05 per cent probability from the velocity of cm in itrf2005 earth s reference frame and we believe itrf s should be defined with the tightly constrained velocity of ce not with the poorly constrained velocity of cm because ce is believed to be moving relative to cm no faster than 0 5 mm yr 1 the velocity of ce estimated in this study is likely to be nearer the true velocity of cm than is the velocity of cm estimated using slr

guadalupe island mexico as a new constraint for pacific plate motion 1 we use gps data collected on isla de guadalupe and in northern baja california mexico to estimate site velocities relative to pacific plate motion the velocities of all three geodetic monuments on guadalupe fit a rigid pacific plate model with residuals of 1 mm yr using the guadalupe data and data from five igs stations on the pacific plate chat kokb kwj1 mkea and thti we estimate an angular velocity for this plate that is consistent with other recently published estimates our results indicate that isla de guadalupe lies on the pacific plate and that gps data collection on the island usefully constrains pacific plate motion and rigidity

crustal velocity and strain rate fields in italy and surrounding regions new results from the analysis of permanent and non permanent gps networks summary we present a new geodetic velocity solution for italy and the surrounding areas obtained from an analysis of continuous and survey mode global positioning system observations collected between 1991 and 2002 we have combined local regional and global networks into a common reference frame velocity solution providing a new detailed picture of the regional scale deformation field in the central mediterranean our velocity estimates are computed with respect to a new stable eurasian reference frame constraining the kinematics of the greater african eurasian plate boundary system in the study area we provide strain rate values for the main seismotectonic districts which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms the southern tyrrhenian area calabria the apennines the southeastern alps the southern dinarides and the albanides display deformation rates at the order of 20 30 nanostrain yr 1 the corsica sardinia block moves according to eurasian plate motions and there is no indication that the opening of the tyrrhenian is still active the pelagian and sicilian domains are separated by a northwest southeast discontinuity the sicily channel rifted area and marginally significant relative motion between the pelagian plateau and the african plate is also observed the southern tyrrhenian is affected by north south compression and accommodates up to 50 per cent of the africa eurasia relative plate motion whereas the calabrian arc exhibits 2 mm yr 1 northwest southeast extension the observed deformation pattern suggests the presence of a major approximately north south tectonic discontinuity separating the sicilian and calabrian domains an extensional boundary observed along peninsular italy coincides with the distribution of seismogenic faults along the axis of the apennines this boundary separates a tyrrhenian and an adriatic domain with diverging velocities orientated north nnw ward and northeastward respectively the apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr 1 and only in the outer northern apennines indications of active shortening are observed insignificant deformation is observed in the western po plain and the western alps while the central and eastern alps display north south shortening the eastern adriatic domain is shortening perpendicular to the dinaric front with strain rates increasing from north to south the locus of collision between the aegean balkan system and the adriatic and ionian domains is marked by the kephalonia fault system which accommodates up to 20 1 mm yr 1 of right lateral motion the deformation pattern observed in the peri adriatic domain is well described by a counter clockwise rotation of the adriatic microplate around a pole located in the western alps

a reassessment of global and regional mean sea level trends from topex and jason 1 altimetry based on revised reference frame and orbits 1 mean sea level trends from topex and jason 1 altimeter data are recomputed using unified geophysical modeling and the new itrf2005 terrestrial reference frame for the entire altimetric time series with consistent orbits based on satellite laser ranging slr and doris tracking data we obtain a global rate of 3 36 0 41 mm yr over the 14 year period from 1993 to 2007 the regional sea level trends computed with the new reference frame show significant north south hemispherical offsets of 1 5 mm yr relative to trends based on the previous 1995 era frame regional sea level trend comparisons for the time periods of 1993 1999 and 1999 2005 reveal strong basin scale polarities and pronounced inter decadal variability with a relative increase in the global mean sea level trend of 1 5 0 7 mm yr in the latter seven years

measuring the onset of locking in the peru chile trench with gps and acoustic measurements the subduction zone off the west coast of south america marks the convergence of the oceanic nazca plate and the continental south america plate nazca south america convergence over the past 23 million years has created the 6 km deep peru chile trench 150 km offshore high pressure between the plates creates a locked zone leading to deformation of the overriding plate the surface area of this locked zone is thought to control the magnitude of co seismic release and is limited by pressure temperature sediment type and fluid content1 here we present seafloor deformation data from the submerged south america plate obtained from a combination of global positioning system gps receivers and acoustic transponders we estimate that the measured horizontal surface motion perpendicular to the trench is consistent with a model having no slip along the thrust fault between 2 and 40 km depth a tsunami in 1996 200 km north of our site was interpreted as being the result of an anomalously shallow interplate earthquake2 seismic coupling at shallow depths such as we observe may explain why co seismic events in the peruvian subduction zone create large tsunamis

analysis of gps measurements in eastern canada using principal component analysis continuous global positioning system cgps position time series from eastern north america constrain the pattern and magnitude of regional crustal deformation initial analysis delineates consistent uplift patterns as expected from glacial isostatic adjustment gia predictions but the associated horizontal deformation is not definitive in part due to the short time periods for a significant number of the available stations we employ an eigenpattern decomposition in order to define a unique finite set of deformation patterns for this continuous gps data similar in nature to the empirical orthogonal functions historically employed in the analysis of atmospheric and oceanographic phenomena the method derives the eigenvalues and eigenstates from the diagonalization of the correlation matrix using a karhunen loeve expansion kle the kle technique is used to identify the important modes in both time and space for the cgps data modes that potentially include signals such as horizontal and vertical gia tectonic strain and seasonal effects here we filter both the vertical and horizontal velocity patterns on different spatiotemporal scales in order to study the potential geophysical sources after the removal of correlated and random noise the method is successful in disaggregating the linear vertical signal from more variable and less spatially correlated signals the vertical and horizontal results are compared to the predictions of the ice 3g gia loading model with a number of plausible mantle viscosity profiles the horizontal velocity analysis allows for qualitative differentiation between several potential gia models and suggests that with longer time series this technique can be employed to remove correlated noise and improve estimates of crustal strain patterns and their sources

plate motion at the ridge transform boundary of the south cleft segment of the juan de fuca ridge from gps acoustic data 1 we measure the present day plate velocity of the juan de fuca ridge 25 km off axis to be 63 6 3 6 mm a at s67 2 e 7 9 degrees 1 relative to the pacific plate pa this velocity was derived from gps acoustic gpsa measurements in 2000 2001 2002 and 2003 that observed the position of a seafloor array 44 43 n 130 03 w 2900 m depth with a repeatability of 4 6 mm three transient events at the juan de fuca ridge and blanco transform account for 10 of this motion in viscoelastic modeling suggesting that the observed gpsa pa velocity is due primarily to steady state plate dynamics subtracting the modeled transient motion gives a velocity of 57 3 3 9 mm a at s72 9 e 12 1 degrees 1 which is consistent at the 95 confidence level with the velocity calculated from the wilson 1993 0 0 78 ma euler pole therefore this site is interpreted to be in a region of continuous full rate plate motion a robust result of this study which holds with and without correcting for transient motions these results provide direct geodetic evidence that spreading occurs predominantly within 25 km of the axis at this intermediate spreading rate ridge previously reported geodetic monitoring across the 1 km wide axial valley from 1994 1999 and 2000 2003 shows no significant extension chadwell et al 1999 hildebrand et al 1999 chadwick and stapp 2002 w w chadwick personal communication 2006 and seismic monitoring shows no activity this suggests the crust between 0 5 and 25 km off axis accommodates 26 mm of aseismic deformation each year through some combination of near axis fault motion and elastic strain accumulation

modeling of petroleum generation in the vietnamese part of the malay basin using measured kinetics two dimensional 2 d modeling of source rock maturation and hydrocarbon hc generation histories were conducted for the malay cho thu basin in the gulf of thailand and south china sea the source rocks comprise oligocene synrift lacustrine mudstones and coals postrift coals and terrigenous influenced mudstones three different lacustrine mudstone source rocks and coals were considered in the 2 d modeling and each source rock was assigned specific generation potential and kinetics measured kinetics for bulk petroleum generation determined on two thermally immature upper oligocene oil prone lacustrine mudstones and on a terrigenous influenced mudstone derived from wells were used together with published coal kinetics the onshore krong pa graben a small scale rift basin in central vietnam was used as a conceptual model for the distribution of lithofacies including source rock types in the 2 d models exploration targets and drilled direct hc indicators dhis are mainly located in the tectonically disturbed postrift succession modeling results suggest that the risks related to this play are 1 timing of petroleum generation from the oil prone lacustrine synrift deposits relative to structural trap formation 2 complex migration pathways through strongly faulted strata and 3 relatively small kitchen areas oil generation from uppermost synrift and postrift coaly source rocks with minor contribution from lacustrine deposits after principal trap formation is consistent with the prominent terrigenous geochemical signature of oils in the malay cho thu basin a new untested play is proposed based on mapping of potential dhis associated with sandstone bodies in tectonically undisturbed synrift traps

deformation of jamaica and motion of the gonâve microplate from gps and seismic data summary we use velocities from 20 gps sites on the island of jamaica and seismic data from the jamaican seismic network to quantify motion of the proposed gonave microplate and study deformation and earthquake hazard in jamaica all 20 jamaican gps sites move significantly relative to both the caribbean and north american plates thereby confirming the existence of the gonave microplate in a caribbean plate reference frame the fastest site velocities in jamaica are 8 1m m yr 1 representing a minimum estimate for the rate of gonave caribbean plate motion we estimate a firm upper limit of 13 1m m yr 1 for gonave caribbean plate motion assuming that additional elastic or permanent deformation occurs north of jamaica beyond the reach of our gps network the range of estimates for gonave caribbean plate motion exceeds the 3 7m m yr 1 range of geologically derived rates for post 10 ma fault slip in jamaica suggesting that motion has either increased relative to the long term deformation rate or that estimates of the long term deformation rate are too slow minimum and maximum rates for gonave north america plate motion are 6 1m m yr 1 and 11 1m m yr 1 based on the differences between the estimated gonave caribbean rates and a recent gps based estimate of 19 3 1m m yr 1 of caribbean north american plate motion in jamaica these are slower than 15 20 mm yr 1 published estimates of the long term seafloor spreading rate across the cayman spreading centre which records gonave north american plate motion our observations are thus consistent with a model in which gonave caribbean plate motion has increased through time while gonave north america plate motion has decreased possibly reflecting a progressive transfer of slip from plate boundary structures that accommodate gonave north america motion to faults that carry gonave caribbean plate motion in jamaica gps site directions in both the caribbean and north american plate reference frames are parallel to the caribbean north america plate slip direction and are only 10 20 different from the azimuths of the island s major strike slip faults the mean p and t axes for 48 earthquakes since 1941 have near horizontal plunges and are oriented 45 from the predicted plate slip direction the kinematic and seismic data thus indicate that deformation on the island is dominated by left lateral shear along largely e w trending strike slip faults relative to the caribbean plate the jamaican gps velocities exhibit a nearly monotonic increase in site velocities from south to north along a transect orthogonal to the island s major e w faults this velocity gradient likely reflects the accumulation of elastic strain due to frictional locking of the major e w faults velocities however also increase monotonically from the wsw to ene along a transect orthogonal to the island s numerous nnw striking faults consistent with the accumulation of significant elastic shortening along those faults and supportive of an interpretation of those faults as restraining bends seismic hazard assessment based on the gps derived deformation budget likely maximum fault rupture lengths and the historical seismic record suggests approximate repeat times of one to several centuries for earthquakes of maximum magnitudes of m w 7 0 7 3 the strain that has accumulated since the destructive 1692 earthquake near the capital city of kingston is presently sufficient to release a m w 7 2 earthquake in eastern jamaica

structural evolution in response to fold and thrust belt tectonics in northern assam a key to hydrocarbon exploration in the jaipur anticline area abstract the upper assam basin is an intermountain basin surrounded on two sides by eastern himalayan fold belt and the third side by assam arakan fold belt the basin has the contradictory characteristics of being a historic oil producing province in one of the most tectonically active areas of the world assam is a seismically active area and the location of major earthquakes yet contains one of the world s largest oil and gas fields an integrated study based on surface and subsurface data and relying on the sequence stratigraphic approach was undertaken to provide a re appraisal of the upper miocene to recent succession and its relationship to the region s structural history detailed data in the jaipur anticline region of the basin is viewed in regional context while the seismic database area includes only the northeastern part of the basin we suggest that the interpretations are applicable to the entire upper assam basin for interpreting the complex relationship between structural evolution and the generation and remigration of hydrocarbons in tectonically active regions a regional geo history analysis is a required component of the petroleum system description necessary for a successful exploration model

no net rotation model of current plate velocities incorporating plate motion model nuvel 1 we present nnr nuvel1 a model of plate velocities relative to the unique reference frame defined by requiring no net rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model nuvel 1 demets et al 1990 differences between nnr nuvel1 and no net rotation plate motion model am0 2 minster and jordan 1978 are as large as 15 mm yr in nnr nuvel1 the pacific plate rotates in a right handed sense relative to the no net rotation reference frame at 0 67 m y about 63 s 107 e this rotation nearly parallels but is 32 slower than the pacific hotspot euler vector of hs2 nuvel1 which is a global model of plate hotspot velocities constrained to consistency with nuvel 1 gripp and gordon 1990 at hawaii the pacific plate moves relative to the no net rotation reference frame at 70 mm yr which is 25 mm yr slower than the pacific plate moves relative to the hotspots differences between nnr nuvel1 and hs2 nuvel1 are described completely by a right handed rotation of 0 33 m y about 49 s 65 e the 99 confidence ellipsoids for plate hotspot motion in model hs2 nuvel1 exclude the corresponding euler vectors from model nnr nuvell thus the no net rotation reference frame differs significantly from the hotspot reference frame if the difference between reference frames is caused by motion of the hotspots relative to a mean mantle reference frame then hotspots beneath the pacific plate move with coherent motion towards the east southeast alternatively the difference between reference frames may show that the uniform drag no net torque reference frame which is kinematically equivalent to the no net rotation reference frame is based on a dynamically incorrect premise possible exceptions to the assumption of uniform drag include a net torque on the lithosphere due to attached subducting slabs and greater resistance to plate motion beneath continents than beneath oceans

temperature distribution and its relation to hydrocarbon accumulation in upper assam valley india well log temperatures have been recorded in more than 400 wells drilled so far by oil india ltd in its concessions in the upper assam tertiary sedimentary basin at the northeastern corner of the indian subcontinent subsurface temperatures presented in the form of isogeothermal maps show 1 a general increase with the rise of basement configuration and 2 maximum values over the crests of local highs with gradual decrease toward the flanks the difference being on the order of 15 c geothermal gradients in the areas studied decrease with depth within argillaceous sediments but increase in the arenaceous group the geothermal gradients obtained for different areas of this sedimentary basin can be used in the hydrocarbon liquid window concept for oil exploration the study reveals that in the eastern part of this basin theoretically a considerable thickness of potentially hydrocarbon bearing section could be down to a depth of about 9 150 m which is yet to be explored by deep drilling

observations of tidally coherent diurnal and semidiurnal variations in the geocenter the center of mass of the earth about which a satellite orbits is determined by the mass distribution of the solid earth including the earth s interior the oceans and the atmosphere the tracking sites however are all located on the lithosphere only and so the network origin will not generally coincide with the center of mass changes in the vector offset between these two points referred to as apparent geocenter motion are due to global scale movement of mass in this study we have extended the approach used by space geodetic techniques for determination of tidally coherent nearly diurnal and semidiurnal variations in the earth s orientation to include geocenter variations due to ocean tides we demonstrate the weaker observability of nearly diurnal retrograde motions in x and y and hence the utility of their separation from the other equatorial terms we find statistically significant terms at the 99 5 level due to o1 p1 k1 and m2 the solutions which indicate geocenter motions at the few millimeter level per tide compare well with predicted values from theoretical ocean tide models and from topex poseidon radar altimetry

consideration of tidal variations in the geocenter on satellite altimeter observations of ocean tides tidal geocenter motion has been previously ignored when developing ocean tide models from satellite altimetry accounting for tidal geocenter motion is necessary because the best orbit determinations for altimetric satellites position sea surface heights relative to the center of mass of the total earth system including the ocean tides but the ocean tides are presumed relative to the earth s crust and thus are effectively relative to the center of figure by accounting for this effect we find improved agreement between an altimeter based ocean tide model and bottom pressure recorder observations the variance of differences between these two observations is reduced by 31 and 43 for the two tidal constituents with the largest contributions to geocenter variations o1 and k1 respectively with this accommodation the predicted contribution from altimeter based ocean tide models to geocenter variations is amplified by 15 22 providing improved agreement with observations especially for the k1 component

transient rheology of the upper mantle beneath central alaska inferred from the crustal velocity field following the 2002 denali earthquake the m7 9 2002 denali earthquake alaska is one of the largest strike slip earthquakes ever recorded the postseismic gps velocity field around the 300 km long rupture is characterized by very rapid horizontal velocity up to 300 mm yr for the first 0 1 years and slower but still elevated horizontal velocity up to 100 mm yr for the succeeding 1 5 years i find that the spatial and temporal pattern of the displacement field may be explained by a transient mantle rheology representing the regional upper mantle as a burghers body 1 infer steady state and transient viscosities of 1 2 8 x 10 18 pa s and 2 1 0 x 10 17 pa s respectively corresponding to material relaxation times of 1 3 and 0 05 years the lower crustal viscosity is poorly constrained by the considered horizontal velocity field and the quoted mantle viscosities assume a steady state lower crust viscosity that is 7 1 systematic bias in predicted versus observed velocity vectors with respect to a fixed north america during the first 3 6 months following the earthquake is reduced when all velocity vectors are referred to a fixed site this suggests that the post denali gps time series for the first 1 63 years are shaped by a combination of a common mode noise source during the first 3 6 months plus viscoelastic relaxation controlled by a transient mantle rheology

kinematics of the iberia maghreb plate contact from seismic moment tensors and gps observations the iberian peninsula and the maghreb experience moderate earthquake activity and oblique nw se convergence between africa and eurasia at a rate of 5 mm yr coeval extension in the alboran basin and a n35 e trending band of active left lateral shear deformation in the alboran betic region are not straightforward to understand in the context of regional shortening and evidence complexity of deformation at the plate contact we estimate 86 seismic moment tensors mw 3 3 to 6 9 from time domain inversion of near regional waveforms in an intermediate period band those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors the solutions associated to the trans alboran shear zone show predominantly strike slip faulting and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction 1 at n350 e at the n algerian and sw iberian margins reverse faulting solutions dominate corresponding to n350 e and n310 e compression respectively over most of the betic range and intraplate iberia we observe predominately normal faulting and wsw ene extension 3 at n240 e from gps observations we estimate that more than 3 mm yr of african nubian eurasian plate convergence are currently accommodated at the n algerian margin 2 mm yr in the moroccan atlas and 2 mm yr at the sw iberian margin 2 mm yr is a reasonable estimate for convergence within the alboran region while alboran extension can be quantified as 2 5 mm yr along the stretching direction n240 e superposition of both motions explains the observed left lateral transtensional regime in the trans alboran shear zone two potential driving mechanisms of differential motion of the alboran betic gibraltar domain may coexist in the region a secondary stress source other than plate convergence related to regional scale dynamic processes in the upper mantle of the alboran region as well as drag from the continental scale motion of the nubian plate along the southern limit of the region in the atlantic ocean the 3 5 mm yr westward motion of the gibraltar arc relative to intraplate iberia can be accommodated at the transpressive sw iberian margin while available gps observations do not support an active subduction process in this area

geodetic observations of ice flow velocities over the southern part of subglacial lake vostok antarctica and their glaciological implications summary in the austral summer seasons 2001 02 and 2002 03 global positioning system gps data were collected in the vicinity of vostok station to determine ice flow velocities over lake vostok ten gps sites are located within a radius of 30 km around vostok station on floating ice as well as on grounded ice to the east and to the west of the lake additionally a local deformation network around the ice core drilling site 5g 1 was installed the derived ice flow velocity for vostok station is 2 00 m a 1 0 01 m a 1 along the flowline of vostok station an extension rate of about 10 5 a 1 equivalent to 1 cm km 1 a 1 was determined this significant velocity gradient results in a new estimate of 28 700 years for the transit time of an ice particle along the vostok flowline from the bedrock ridge in the southwest of the lake to the eastern shoreline with these lower velocities compared to earlier studies and hence larger transit times the basal accretion rate is estimated to be 4 mm a 1 along a portion of the vostok flowline an assessment of the local accretion rate at vostok station using the observed geodetic quantities yields an accretion rate in the same order of magnitude furthermore the comparison of our geodetic observations with results inferred from ice penetrating radar data indicates that the ice flow may not have changed significantly for several thousand years

separation of tectonic and local components of horizontal gps station velocities a case study for glacial isostatic adjustment in east antarctica accurate measurement of the local component of geodetic motion at gps stations presents a challenge due to the need to separate this signal from the tectonic plate rotation a pressing example is the observation of glacial isostatic adjustment gia which constrains the earth s response to ice unloading and hence contributions of ice covered regions such as antarctica to global sea level rise following ice mass loss while both vertical and horizontal motions are of interest in general we focus on horizontal gps velocities which typically contain a large component of plate rotation and a smaller local component primarily relating to gia incomplete separation of these components introduces significant bias into estimates of gia motion vectors we present the results of a series of tests based on the motions of gps stations from east antarctica 1 signal separation for sets of synthetic data that replicate the geometric character of non separable and separable gia like horizontal velocities and 2 signal separation for real gps station data with an appraisal of uncertainties for both synthetic and real motions we compare results where the stations are unweighted and where each station is areal weighted using a metric representing the inverse of the spatial density of neighbouring stations from the synthetic tests we show that a gia like signal is recoverable from the plate rotation signal providing it has geometric variability across east antarctica we also show that areal weighting has a very significant effect on the ability to recover a gia like signal with geometric variability and hence on separating the plate rotation and local components for the real data assuming a rigid antarctic plate fitted plate rotation parameters compare well with other studies in the literature we find that 25 out of 36 gps stations examined in east antarctica have non zero local horizontal velocities at the 2 level after signal separation we make the code for weighted signal separation available to assist in the consistent appraisal of separated signals and the comparison of likely uncertainty bounds for future studies

effects of atmospheric pressure loading and seven parameter transformations on estimates of geocenter motion and station heights from space geodetic observations 1 variations in fluid loads such as the oceans and the atmosphere deform the surface of the earth the accuracy of station coordinates in particular heights that can be estimated depends on how well one can separate these surface deformations from the associated translational motion between the center of mass of the solid earth and the total earth cm we applied simulated atmospheric pressure loading effects to the coordinates of sites in the cm frame to explore to what level of accuracy both geocenter motion and accurate station coordinates can actually be recovered from geodetic analyses we found that standard seven parameter transformations three rotations three translations scale generally recover about 80 of the geocenter motion however the inclusion of a scale factor permits the aliasing of surface loading deformation introducing scale errors of up to 0 3 ppb and daily height errors as large as 4 mm this limits the geophysical studies that can be performed accurately using the results of geodetic analyses where the magnitudes of the signals are small e g tectonic movement of tide gauges uplift rates for interpreting glacial isostatic adjustment the quality of the geodetic results is extremely sensitive to the number and distribution of sites used to estimate the transformations and becomes worse when regional rather than global sets of sites are used if the scale factor parameter is omitted then the amount of aliasing of surface loading effects is reduced considerably and more accurate site velocities and geocenter motion estimates are achieved

repeated absolute gravity measurements for monitoring slow intraplate vertical deformation in western europe in continental plate interiors ground surface movements are at the limit of the noise level and close to or below the accuracy of current geodetic techniques absolute gravity measurements are valuable to quantify slow vertical movements as this instrument is drift free and unlike gps independent of the terrestrial reference frame repeated absolute gravity ag measurements have been performed in oostende belgian coastline and at 8 stations along a southwest northeast profile across the belgian ardennes and the roer valley graben germany in order to estimate the tectonic deformations in the area the ag measurements repeated once or twice a year can resolve elusive gravity changes with a precision better than 3 7 nm s yr 95 confidence interval after 11 years even in difficult conditions after 8 15 years depending on the station we find that the gravity rates of change lie in the 3 1 8 1 nm s yr interval and result from a combination of anthropogenic climatic tectonic and glacial isostatic adjustment gia effects after correcting for the gia the inferred gravity rates and consequently the vertical land movements reduce to zero within the uncertainty level at all stations except julich due to man induced subsidence and sohier possibly an artifact due to the shortness of the time series at that station

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

pattern of deformation around the central aeolian islands evidence from multichannel seismics and gps data the tectonics of the central aeolian islands which are located within the tyrrhenian backarc basin has been investigated through a marine seismic reflection survey we find that compressional structures dominate around the islands whereas extensional faults occur only to the north of salina and filicudi towards the marsili basin this pattern of deformation although different from previously reported is in agreement with the strain field and stress regime obtained from gps measurements and seismological data age constraints suggest that contractional deformation was active since middle pleistocene being coeval with the building of the volcanic edifices of the aeolian islands and is superimposed on pre existing extensional deformation compressional and extensional regimes therefore can coexist within a backarc setting seismic profiles show that the tindari letojanni fault considered as a major tectonic element does not extend to the north towards the island of vulcano as a throughgoing fault rather deformation is accommodated in a broader belt displaying greater structural complexity

lithosphere thickness and mantle viscosity inverted from gps derived deformation rates in fennoscandia summary crustal deformation in fennoscandia is associated with the glacial isostatic adjustment gia process that is caused by ongoing stress release of the mantle after removal of the late pleistocene ice sheet by 10 cal ka bp with an earth model of defined structure and rheology and an ice sheet model of known melting history the gia process can be simulated by geophysical models and the surface deformation rates can be calculated and used to compare with global positioning system gps observations therefore the crustal deformation rates observed by gps in fennoscandia provide constraints on the geophysical models on the basis of two ice sheet models anu ice and ice 5g reconstructed independently by the australian national university anu and university of toronto we use the gps derived deformation rates to invert for lithosphere thickness and mantle viscosity in fennoscandia the results show that only a three layer earth model can be resolved from current gps data providing robust estimates of effective lithosphere thickness upper and lower mantle viscosity the earth models estimated from inversion of gps data with two different ice sheet models define a narrow range of parameter space the lithosphere thickness between 93 and 110 km upper mantle viscosity between 3 4 and 5 0 1020 pa s and lower mantle viscosity between 7 1021 and 13 1021 pa s the estimates are consistent with those inverted from relative sea level indicators

gps determination of the velocity and strain rate fields on schirmacher glacier central dronning maud land antarctica global positioning system gps campaigns were conducted during the 2003 and 2004 austral summer seasons to obtain insight into the velocity and strain rate distribution on schirmacher glacier central dronning maud land east antarctica gps data were collected at 21 sites and analyzed to estimate the site coordinates baselines and velocities the short term precision of the base station mait is estimated from the daily coordinate repeatability solutions during the two years all gps points on the glacier were constrained with respect to mait and nearby international gps service stations horizontal velocities of the glacier sites lie between 1 89 0 01 and 10 88 0 01 m a 1 to the north northeast with an average velocity of 6 21 0 01 m a 1 the principal strain rates provide a quantitative measurement of extension rates which range from 0 11 0 01 10 3 to 1 48 0 85 10 3 a 1 and shortening rates which range from 0 04 0 02 10 3 to 0 96 0 16 10 3 a 1 the velocity and strain rate distributions across the gps network in schirmacher glacier are spatially correlated with topography subsurface undulations fracture zones crevasses and the partial blockage of the flow by nunataks and the schirmacher oasis

kinematic models of plate boundary deformation in southwest iceland derived from gps observations 1 we use data from gps campaign and continuous measurements from 1992 to 2004 in sw iceland to map the surface velocity field from the reykjanes peninsula to the eastern volcanic zone we divide the time series into preseismic july 1992 to june 2000 and postseismic june 2000 to may 2004 time intervals and we estimate gps station velocities for each interval as well as coseismic offsets due to the june 2000 earthquake sequence in the south iceland seismic zone sisz in addition to the plate spreading the preseismic velocity field shows the effects of inflation at hengill and hekla volcanoes whereas the postseismic velocities show deformation following the june 2000 earthquakes we consider several kinematic models to explain the preseismic velocities our preferred model includes several dislocations and point sources in an elastic half space with left lateral slip along the plate boundary on the reykjanes peninsula and below the sisz opening across the reykjanes peninsula and the western and eastern rift zones the optimal model has a locking depth of about 8 km in the central and eastern part of the reykjanes peninsula with a deep slip rate of about 17 mm yr and an opening of about 9 mm yr this locking depth is in agreement with the thickness of the seismogenic crust on the reykjanes peninsula which appears to vary between 7 and 9 km for the sisz we obtain a deep slip rate of about 19 mm yr below 16 km depth which is considerably deeper than the earthquake hypocenter depths in the area

thermal maturity evaluation by sonic log and seismic velocity analysis in parts of upper assam basin india vitrinite reflectance is an important index used in assessment of thermal maturity of petroleum source rocks vitrinite reflectance typically increases with depth of burial as a function of time and temperature and is accompanied by a decrease in log derived interval transit time the relationship between these parameters has been investigated in the upper assam tertiary basin india an equation that relates sonic log transit time to vitrinite reflectance has been derived thus interpretation of the sonic log enables a quantitative estimation of thermal maturity that is not affected by the problems frequently encountered in measurement and interpretation of vitrinite reflectance data further the approach has been extended to the determination of thermal maturity from seismic velocity analysis the results suggest that seismic data can be used as an additional maturity evaluation tool which can provide preliminary estimates of maturity in undrilled areas of the basin

relative and absolute sea level rise in western canada and northwestern united states from a combined tide gauge gps analysis 1 empirical studies and climate models suggest large variations of absolute sea level asl changes between oceanic basins such potential variations raise concern on the applicability of global mean asl predictions to specific regions and on estimates of relative sea level rsl hazards we address this issue for the western canada and northwestern united states coastline by estimating the 20th century asl rate using a combination of 34 colocated tide gauge and global positioning system gps stations the tide gauge data are quality controlled and corrected for spatially and temporally correlated sea level transients in order to derive robust rsl trends and standard errors reference frame and other gps specific issues are considered as part of the error budget in absolute gps vertical velocities our combined tide gauge gps analysis aligned to the international terrestrial reference frame 2000 indicates a northeast pacific asl rise of 1 8 0 2 mm a through the 20th century which is similar to accepted rates for the global eustatic mean for the period 1993 2003 we find a regional asl rate of 4 4 0 5 mm a consistent with satellite altimetry on the basis of the intergovernment panel on climate change assessment report 4 mean scenario and our assessment of coastal motions from gps and tide gauge data we derive a map of predicted 21st century rsl rise in western canada and the northwestern united states variations in coastal uplift strongly affect spatial rsl patterns subsidence of southern puget sound may significantly increase rsl rise in the seattle tacoma metropolitan area conversely tectonic uplift along parts of the outer west coast may reduce future rsl rise by up to 50 100

higher plant biomarker signatures of early eocene sediments of north eastern india abstract the biomarkers molecular fossils of paleobiota have been studied in detail from a coal bearing sequence of early eocene lakadong sandstone member of sylhet formation of upper assam basin ne india using gas chromatography mass spectrometry corresponding hydrocarbon source potential of the same unit has been studied using rock eval pyrolysis the rock eval data suggest dominant terrestrial land plant contribution i e type iii kerogen and the sediments of the section had entered the early stage of catagenesis the alkane and isoprenoid distributions are characterized by odd over even preference oep 1 1 1 2 of n alkanes and high pristane phytane ratio 2 9 7 6 which corroborate the rock eval data the distribution of aliphatic biomarkers is characterized by dominance of c24 tetracyclics over c23 tricyclics high concentration of des e hopane moderate to high c29 c30 hopane ratio extremely low oleanane index and low c35 homohopane index the extremely low oleanane index is correlated with a high degree of aromatization of oleanane skeleton favoured by acidic swampy depositional environment the presence of diterpanes at the base of the early eocene section indicates contribution from gymnosperms coniferales order of land plants whereas angiospermous biomarkers with oleanoid skeleton are also preserved this pattern subsequently evolved to angiosperm dominated towards the top of the section with no gymnosperm signature indicating possible climatic variation during the early eocene towards the top of the section presence of bicadinanes indicates contribution of dipterocarpaceae family of trees and advent of the evergreen tropical rain forest element in eastern india in early eocene similar to the pattern found in western india e g cambay and kutch basins

merging gps and atmospherically corrected insar data to map 3 d terrain displacement velocity a method to derive accurate spatially dense maps of 3 d terrain displacement velocity is presented it is based on the merging of terrain displacement velocities estimated by time series of interferometric synthetic aperture radar insar data acquired along ascending and descending orbits and repeated gps measurements the method uses selected persistent scatterers pss and gps measurements of the horizontal velocity an important step of the proposed method is the mitigation of the impact of atmospheric phase delay in insar data it is shown that accurate vertical velocities at ps locations can be retrieved if smooth horizontal velocity variations can be assumed furthermore the mitigation of atmospheric effects reduces the spatial dispersion of vertical velocity estimates resulting in a more spatially regular 3 d velocity map the proposed methodology is applied to the case study of azores islands characterized by important tectonic phenomena

instantaneous global plate motion model from 12 years of continuous gps observations 1 we estimate a global plate motion model for 17 major and minor tectonic plates solely on the basis of analysis of data from 106 globally distributed continuous gps stations spanning the period from january 1991 to july 2003 site positions estimated from 24 hour segments of data are aligned day by day to the international gps service igs realization of the itrf2000 reference frame using a similarity transformation thereby ensuring that the itrf2000 no net rotation condition is preserved linear velocities of a carefully selected set of stations are estimated from the position time series along with annual and semiannual fluctuations and position offsets due to gps instrument changes a white noise plus flicker noise model is applied to estimate realistic uncertainties for the site velocities which are then propagated into the derived plate motion model parameters we also examine the vertical velocities in the site selection process at the scripps orbit and permanent array center we have implemented a procedure whereby the plate motion model is updated on a regular monthly basis to improve its precision and reliability as new data become available and as a baseline against which anomalous motions can be detected

strain localization due to structural in homogeneities in the central european basin system the large scale crustal deformations observed in the central european basin system cebs are the result of the interplay between several controlling factors among which lateral rheological heterogeneities play a key role we present a finite element integral thin sheet model of stress and strain distribution within the cebs unlike many previous models this study is based on thermo mechanical data to quantify the impact of lateral contrasts on the tectonic deformation elasto plastic material behaviour is used for both the mantle and the crust and the effects of the sedimentary fill are also investigated the consistency of model results is ensured through comparisons with observed data the results resemble the present day dynamics and kinematics when 1 a weak granite like lower crust below the elbe fault system is modelled in contrast to a stronger lower crust in the area extending north of the elbe line throughout the baltic region and 2 a transition domain in the upper mantle is considered between the shallow mantle of the variscan domain and the deep mantle beneath the east european craton eec extending from the elbe line in the south till the tornquist zone the strain localizations observed along these structural contrasts strongly enhance the dominant role played by large structural domains in stiffening the propagation of tectonic deformation and in controlling the basin formation and the evolution in the cebs

petroleum geochemistry of a part of upper assam basin india a brief overview abstract the upper assam tertiary sedimentary basin is an important petroleum province with reservoir rocks ranging in age from upper paleocene to miocene the bulk of the oil production is from the barail oligocene and tipam miocene formations promising hydrocarbon pools have been discovered recently in upper paleocene lower eocene formations prolific source rocks occur within the barail oligocene formation langpar formation upper paleocene and lakadong theria member of sylhet formation of upper paleocene lower eocene age the source rocks contain predominantly type ii organic matter and are thermally immature to early mature biomarker ratios indicate the dominance of land plant derived kerogen the barail and tipam oils have moderate gravity and significant wax contents the physical and chemical characteristics of the paleocene eocene crude oil is similar to that produced from younger horizons within the basin with the exception of minor quantities of heavy viscous crude oils observed in a few wells multivariate analysis including principal components analysis and factor analysis of fluorescence data and principal components analysis of biomarker data indicate that the barail oligocene and tipam miocene oil have been derived from barail source rocks with a possible contribution from eocene source rocks these preliminary studies have not provided conclusive evidence for the source of the eocene oils although geological factors indicate that the source rocks are probably the interbedded shales coals occurring within the upper paleocene lower eocene sediments