a transient heating event in the history of a highlands troctolite from apollo 12 soil 12033 a 1 5 mm clast of a highlands troctolite attached to a glassy alkali rich soil breccia was identified in a thin section of 1 2 mm particles from apollo 12 soil sample 12033 the troctolite consists of euhedral olivines fo89 in a groundmass of granulitic plagioclase an95 each olivine grain is rimmed by a thin selvage of olivine plagioclase glass containing vesicles and minute crystallites of spinel olivine and plagioclase this unique texture records a complex history beginning with the formation of the troctolite as a plutonic cumulate followed by subsolidus metamorphism partial remelting vesculation crystallite growth and quenching experimental runs on plagioclase olivine melting rates show that at temperatures above incipient melting the grain boundary selvages in the lunar troctolite would have formed very rapidly in less than about 10 min preservation of selvage glass required rapid cooling the troctolite was subject to a heat pulse most likely accompanying an impact event the same event or more probably a later one welded the troctolite to the soil breccia inasmuch as this particle was found on oceanus procellarum at a site crossed by a ray from copernicus and because olivine has been identified by remote sensing experiments as the dominant mafic mineral in the central peak of copernicus we suggest that the troctolite is a fragment of copernicus ejecta

how partial melts of mafic lower crust affect ascending magmas at oceanic ridges we present experiments showing that the lower oceanic crust should melt efficiently and quickly when heated by hot ascending magmas average plagioclase olivine and plagioclase augite pairs from the lower crust at the southwest indian ridge have melt mineral saturation boundaries at 1 190 and 1 154 c respectively and melt rapidly 0 01 mm h at 50 c or more above these temperatures melting experiments performed on olivine plagioclase and augite plagioclase mineral pairs from actual oceanic lower crustal rock samples and under conditions applicable to a mor setting 1 220 1 330 c 1 atm quartz fayalite magnetite oxygen buffer 0 25 24 h indicate that the resulting disequilibrium melts are linear mixes of the mineral compositions the rates of melting are slower than the rate of heat diffusion into a sample and are approximated as 2 43 10 26 e0 004109 t degc m s1 2 for augite melted with plagioclase 3 47 10 15 e0 002041 t degc for plagioclase melted with augite and 1 79 10 21 e0 0032 t degc for plagioclase melted with olivine our results indicate that great care must be taken in backward models using basalt chemistry alone to explore mantle melting processes assuming only crystallization and fractionation during ascent as partial melts may mix with intruded hot magma

the nature of crater rays the copernicus example crater rays are formed during a cratering event as target material is ballistically ejected to distances of many crater radii forming narrow generally high albedo approximately linear features extending outward from the crater the nature of crater rays was examined for the lunar crater copernicus using new information on the composition of surface material from near ir reflectance measurements surface roughness from radar backscatter measurements and photogeologic data from available images part of the data analysis included use of mixing models to quantify the mixing systematics observed between primary ejecta and local substrate of the ray on the basis of compositional parameters from reflectance spectra primary material from copernicus can be detected in the surface material of rays in decreasing amounts with increasing radial distance e g 20 25 primary ejecta at six crater radii for distances greater than three crater radii the proportion of local material to primary ejecta observed from these compositional reflectance data is approximately equal to that predicted by previous laboratory and ballistic studies of craters within three crater radii the compositional data indicate a higher proportion of primary ejecta than predicted for extended areas along the ray that do not contain large secondary craters the primary ejecta is intimately mixed on the granular scale with local material throughout the regolith the relatively high albedo of the rays of copernicus is due to the feldspathic composition highland of the primary ejecta in rays emplaced on a mare substrate immature local substrate is only observed in copernicus s ray at large unmantied secondary craters or other areas with sufficient topographic slope to prevent the accumulation of mature soils crater rays are filamentous generally high albedo features that emanate nearly radially from young impact structures rays are narrow in relation to the crater radius extend distally for many crater radii and constitute a distinctive albedo feature around some of the largest and freshest lunar craters visible from earth synoptic views of ray systems figure la give the strong impression that the rays comprise bright material that has been excavated from the crater cavity and been emplaced beyond the continuous ejecta deposit if this visual impression is correct then the process that forms crater rays represents a significant mechanism for the lateral transport of primary material to great distances from its point of origin and particularly for craters larger than a let tens of kilometers in diameter constitutes a fundamental process for the regional mixing of crustal materials earth based telescopic images of the moon allowed the first studies and descriptions of rays and ray systems shoemaker 1962 described the arcuate and loop shaped streaks of the copernicus ray systems and showed that these patterns could be locally resolved into individual en echelon feather shaped elements 15 20 km in length with their long axes oriented approximately radially to the crater he noted the presence of elongate depressions or gouges in the ray system ranking in diameter from 8 km down to the limits of resolution and generally located at the proximal ends of the individual ray elements shoemaker observed that some of the gouges were

evolution of ocean slicks under a rising wind 1 airborne synthetic aperture radar and high resolution infrared imagery are used to examine the evolution of natural ocean slicks during a period of freshening wind initially the slicks are of the order of 50 m in width and have radar and thermal contrasts of the order of 10 db and several 0 1 c while there can be over time a transient reorganization of surface film material by internal waves the slicks are observed to disperse and are no longer detectible after 5 h the dispersion occurs through the action of langmuir circulation which results in along wind streaks or windrows as well as other effects prominent streaks occur preferentially along a slick s upwind side the downwind side resembling more of a leading edge at least early on over time the leading edge develops a corrugated shape and gaps begin to develop within the slicks the formation of gaps is compared with a conceptual model by dysthe 2006 for the tearing of a surface film in the region of positive surface straining eventually the slicks break into elongated patches that co exist with windrows which is consistent with the effects of advective dispersion

the sensitivity of post glacial sea level to viscosity structure and ice load history for realistically parameterized viscosity profiles the continuous variation of viscosity with depth expected from microphysical theories of silicate creep differs significantly from the layered structures typically used to model post glacial relative sea level variations and to refine models of ice load histories here we predict relative sea level rsl curves for a set of realistically parameterized continuous viscosity profiles with different amounts of depth dependence we demonstrate by forward modeling that different classes of realistically parameterized mantle viscosity structures are resolvable by rsl at the edge sites but the predicted rsl there is very sensitive to the assumed ice load history furthermore the sensitivity of rsl variations at these sites to the viscosity structure depends strongly upon the ice model at sites less sensitive to the ice model the resolving power for viscosity structure is also less when ice 1a an ice model derived without assumption of mantle viscosity structure is used to compute rsl variations some models with realistic continuous viscosity increases with depth fit the observations better than the standard model used to derive more recent ice models

dissolution kinetics of plagioclase in the melt of the system diopside albite anorthite and origin of dusty plagioclase in andesites the textures and kinetics of reaction between plagioclase and melts have been investigated experimentally and origin of dusty plagioclase in andesites has been discussed in the experiments plagioclase of different compositions an96 an61 an54 an23 and an22 surrounded by glasses of six different compositions in the system diopside albite anorthite was heated at temperatures ranging from 1 200 to 1 410 c for 30 min to 88 h textures were closely related to temperature and chemical compositions a crystal became smaller and rounded above the plagioclase liquidus temperature of the starting melt glass and remained its original euhedral shape below the liquidus whatever the temperature the crystal melt interface became rough and often more complicated sieve like texture composed of plagioclase melt mixture in the scale of a few m was developed from the surface of the crystal inward formation of mantled plagioclase if the crystal is less calcic than the plagioclase in equilibrium with the surrounding melt and the interface remained smooth if the crystal is more calcic than the equilibrium plagioclase from these results the following two types of dissolution have been recognized 1 a crystal simply dissolves in the melt which is undersaturated with respect to the phase simple dissolution and a crystal is partially dissolved to form mantled plagioclase by reaction between sodic plagioclase and calcic melt partial dissolution the amount of a crystal dissolved and reacted increased proportional to the square root of time this suggests that these processes are controlled by diffusion probably in the crystal mantled plagioclase produced in the experiments were very similar both texturally and chemically to some of the so called resorbed plagioclase in igneous rocks chemical compositions and textures of plagioclase phenocrysts in island arc andesites of magma mixing origin have been examined cores of clear and dusty plagioclase were clacic about an90 and sodic about an50 respectively this result indicates that dusty plagioclases were formed by the partial melting due to reaction between sodic plagioclase already precipitated in a dacitic magma and a melt of intermediate composition in a mixed magma during the magma mixing

haskell 1935 revisited the haskell 1935 value of 1021 pa s for mantle viscosity is a classic and enduring constraint on the rheology of the earth s interior we revisit this inference using spherically symmetric self gravitating maxwell viscoelastic earth models our inference is based on both forward and inverse analyses of decay times associated with uplift at two sites considered by haskell angerman river sweden and oslo norway rather than the raw relative sea level rsl data at these sites we demonstrate that predictions of the decay time associated with the angerman river data are insensitive to variations in both the late pleistocene ice load history and the lithospheric thickness of the earth model the predictions at oslo are sensitive to both these inputs and hence decay times at this site provide a remarkably robust constraint on mantle viscosity we derive a constraint on the average viscosity of the mantle of 0 65 1 10 1021 pa s where the average resolved by the data encompasses a region which extends from the base of the lithosphere to a depth of near 1400 km this indicates that many previous analyses which have invoked the haskell value of 1021 pa s as a constraint on the average upper mantle i e above 670 km depth viscosity alone have misinterpreted the resolving power of the inference furthermore our analysis indicates that a number of apparently contradictory inferences of viscosity based on fennoscandian data satisfy the new rigorous interpretation of the haskell constraint finally we demonstrate how the ambiguity in the upper mantle lower mantle viscosity contrast associated with the haskell average may be reduced by invoking decay time constraints estimated from rsl curves in hudson bay a preliminary inversion of decay times at angerman river and richmond gulf in hudson bay suggests a contrast of approximately an order of magnitude between the average viscosities of the upper mantle and the top 1000 km of the lower mantle however a conclusive analysis in this regard must await the determination of consistent decay time estimates for the hudson bay region

green s functions for post seismic strain changes in a realistic earth model and their application to the tohoku oki m w 9 0 earthquake based on a spherically symmetric self gravitating viscoelastic earth model we derive a complete set of green s functions for the post seismic surface strain changes for four independent dislocation sources strike slip dip slip and horizontal and vertical tensile point sources the post seismic surface strain changes caused by an arbitrary earthquake can be obtained by a combination of the above green s functions the post seismic surface strain changes in the near field agree well with the results calculated by the method in a half space earth model wang et al in comupt geosci 32 527 541 2006 which verifies our green s functions with an increase in the epicentral distance the effect of the curvature on both the co and post seismic strain changes clearly increases revealing the importance of our spherical theory for far field calculations next we use our green s functions to simulate the post seismic surface strain changes that were caused by the viscoelastic relaxation of the mantle over the 6 year period after the tohoku oki mw 9 0 earthquake based on continuous global positioning system gps observations around honshu island of japan northeastern china south korea and the russian far east we also deduce the post seismic strain changes caused by the tohoku oki mw 9 0 earthquake overall the distributions of the calculated and gps derived strain changes agree well each other finally we compare the relative error between the observed and simulated strain changes over the 3 0 4 5 year period after the earthquake in both the near and far field we find that the relative errors decrease as the epicentral distance increases which validates our green s functions for research in the far field

trajectories in gulf stream meanders a simple model based on conservation of stream function and potential vorticity is used to derive theoretical estimates for the horizontal and vertical displacements of fluid particles in gulf stream meanders these displacements are given as functions of the meander s curvature and meridional displacement the theory also provides an estimate of the translation speed of the meander finally comparisons with rafos float trajectories and observational estimates of the components of the potential vorticity budget validate the theory

a review and analysis of silicate mineral dissolution experiments in natural silicate melts abstract we present a database and a graphical analysis of published experimental results for dissolution rates of olivine quartz plagioclase clinopyroxene orthopyroxene spinel and garnet in basaltic and andesitic melts covering a range of experimental temperatures 1100 1500 c and pressures 10 5 pa 3 0 gpa the published datasets of donaldson 1985 1990 and brearly and scarfe 1986 are the most complete experimental dissolution rates from all datasets are recalculated and normalized to a constant oxygen basis to allow for direct comparison of dissolution rates between different minerals dissolution rates range from 5 10 10 oxygen equivalent moles o e m cm 2 s 1 for olivine in a basaltic melt to 1 3 10 5 o e m cm 2 s 1 for garnet in a basaltic melt values of ln are arthenian for the experiments examined and activation energies range from 118 to 1800 kj o e m for quartz and clinopyroxene respectively the relationship between calculated a rt for the dissolution reactions where a is the thermodynamic potential affinity and values of is linear for olivine plagioclase and quartz we interpret this as strong evidence in support of using calculated a as a predictor of for at least superliquidus melt conditions

synthetic aperture radar observations of currents colocated with slicks during low wind conditions our synthetic aperture radar sar imagery of the ocean contains examples of strong perturbations in the geometry of persistent turbulent ship wakes at the intersection of wakes with dark slicklike features the perturbations in the wakes are presumably caused by currents and are invariably colocated with slicklike submesoscale features the current dynamics influencing the geometry of turbulent wakes are hypothesized to contribute to the efficient accretion of a biotic and abiotic microlayer in a localized surface zone which is observed as a dark slick in our sar imagery time displaced sar imagery allows us to track the time evolution of the turbulent wake perturbations to determine the differential surface current responsible for the perturbations and to estimate the associated shear in addition the time displaced imagery also allows us to observe the temporal stability of the slicklike features

gulf stream surface convergence imaged by synthetic aperture radar on july 20 1990 the north edge of the gulf stream 36 7 n 72 0 w was sampled by the r v cape henlopen and simultaneously imaged by the jet propulsion laboratory s airborne synthetic aperture radar sar hydrographic measurements show an abrupt surface front separating warm salty gulf stream water in the south from a filament of cool fresh 33 practical salinity unit psu water to the north the filament lies within the stream and is likely water entrained from the continental shelf the southern boundary of the filament is marked by increased surface wave breaking in a 100 to 200 m wide zone accumulations of sargassum and an orthogonal velocity change of 20 cm s the front is manifested in a sequence of sar images as a narrow line having returns 1 2 db higher than background a second transient sar line occurs near the northern filament boundary the observations are compared with model calculations of the surface wave hydrodynamics and radar scattering the ocean waves are driven by southwesterly 8 m s winds and interact with the front to produce primarily an enhancement of 2 to 3 m waves over a 200 m wide region centered downwind of the front using a composite scattering radar model along with measured breaking wave statistics we show that the observed modulations in the radar backscatter can be accounted for through breaking wave and tilted bragg wave scattering effects these results further show that sar images of the ocean surface can be exploited for detailed study of particular ocean processes

inertial instability and sea spirals 1 the ubiquitous occurrence of submesoscale cyclonic spirals in the sea as inferred from space imagery is interpreted in terms of the inertial instability of a horizontally sheared current in the oceanic mixed layer the instability is shown to weaken anticyclonic current shear while enhancing cyclonic shear which in turn becomes unstable and creates a cyclonic vortex concurrently surface tracer particles concentrated along the evolving cyclonic shear are wound up into a spiral mimicking the spiral slick patterns seen in the imagery the entire process investigated with a fully nonlinear nonhydrostatic 3d numerical model is contrasted with the baroclinic frontal process considered previously the differences point to a clear need for field observations of this significant phenomenon which are presently almost totally lacking

melting and dissolution kinetics application to partial melting and dissolution of xenoliths kinetics of melting and dissolution rates and textures in magmatic systems is reviewed and applied to partial melting and dissolution of xenoliths special attention is paid to melting dissolution of solid solution crystals in which characteristic cloudy textures are formed and diffusion of elements in the crystals plays an important role due to compositional change of the crystals based on the above discussion model calculations are made for xenolith digestion using the haplogabbro system diopside plagioclase xenolith digestion can proceed by partial melting of the xenolith itself as well as dissolution in this case xenolith size is not important the digestion rates suggest that many xenoliths could survive only if they were incorporated into a host basaltic magma just prior to eruption natural partial melting found in a spinel lherzolite xenolith from kilbourne hole new mexico is also examined with additional heating experiments it is concluded that spongy clinopyroxene in the spinel lherzolite was formed by partial dissolution reaction between clinopyroxene and partial melt during partial melting at depth for a short run duration a month or less both the model calculations and the heating experiments show that even mafic to ultramafic xenoliths can easily undergo partial melting or react with basaltic melts and many xenoliths found in basaltic rocks could be incorporated into the basalts just prior to eruptions

flow field properties of long propagating frontal waves abstract recent observations of particle paths in the gulf stream show clear evidence of strong vertical motion with upwelling approaching anticyclonic turns and sinking approaching cyclonic turns in a recent paper a simple model of propagating long waves on oceanic fronts was developed based on stommel s model of the gulf stream and its wave propagation properties compared with observations in this paper properties of the associated model flow field especially the vertical velocity are examined for comparison with the observations of rossby et al similar phase and amplitude results are found

computing ocean surface currents over the coastal california current system using 30 min lag sequential sar images as compared with conventional methods for measuring ocean surface currents spaceborne synthetic aperture radar sar offers cloud penetrating ocean current observation capability at high spatial resolution while some studies have shown the potential of sar for studying ocean surface currents through feature tracking they have only analyzed a few images to demonstrate the basic measurement technique and no concise general technique has been developed this paper shows the application of the maximum cross correlation mcc method to generate ocean surface currents from nearly two years of available sequential spaceborne c band sar imagery from the envisat asar and ers 2 advanced microwave instrument sar sensors over the coastal california current system the data processing strategies are discussed in detail and results are compared with hf radar measured currents one dimensional wavenumber spectra of the sar derived surface currents agree with the k 2 power law as predicted by submesoscale resolution models comparisons with hf radar currents show encouraging results with mcc sar vectors oriented slightly counterclockwise relative to hf radar vectors mcc sar surface currents are found to have larger magnitudes than hf radar currents approx 11 cm s which may be due to the fact that sar penetrates only a few centimeters into the ocean surface whereas hf radar currents are averaged over the top 1 m of the ocean surface the larger part of this magnitude difference is contained in the along shore component which can be attributed to higher hf radar accuracy in the direct radial cross shore measurements as compared with along shore components derived from multiple cross shore radial measurements

horizontal motions due to post glacial rebound north american horizontal post glacial rebound velocities are computed for three five layered incompressible spherical maxwell earth models using a simple glacial loading cycle centered on hudson bay the reference earth model has a 120 km thick elastic lithosphere and upper and lower mantle viscosities of 1021 pa s and 2 1022 pa s respectively the second model has a lower viscosity upper mantle 5 1020 pa s and a higher viscosity lower mantle 1023 pa s and the third has a 250 km thick lithosphere the reference model and the low viscosity upper mantle model calculations are in good agreement with uplift and gravity data although they may somewhat overestimate the present day central uplift rate the thick lithosphere model fares less well because it fails to exhibit the well pronounced peripheral bulge sinking that is required by eastern north america tide gauge data the reference model generally has the largest horizontal rebound velocities reaching a maximum of 4 mm yr towards hudson bay at 2400 km from the load center the effect of a thick lithosphere or of a low viscosity upper mantle is to reduce present day horizontal velocities especially in the formerly glaciated region the sensitivity of horizontal motions to lithospheric thickness and upper mantle viscosity may assist in discriminating between different models of the earth s rheology once sufficient high quality geodetic data exist

radial profile of mantle viscosity results from the joint inversion of convection and postglacial rebound observables we present new inferences of the radial profile of mantle viscosity that simultaneously fit long wavelength free air gravity harmonics associated with mantle convection and a large set of decay times estimated from the postglacial uplift of sites within previously glaciated regions hudson bay arctic canada and fennoscandia the relative sea level variation at these latter sites is constrained by age height pairs obtained by geological survey rather than the subjective trends which are commonly used in glacial isostatic adjustment gia studies our viscosity inferences are generated using two approaches first we adopt a relative viscosity profile which is known to provide a good fit to the free air gravity harmonics and determine an absolute scaling which yields a best fit to the gia decay time constraints second we perform an iterative nonlinear joint inversion of the two data sets in both cases our inferred profiles are characterized by a significant increase of viscosity 2 orders of magnitude with depth to values of 1022 pa s in the bottom half of the lower mantle the new viscosity profiles are shown to satisfy constraints based on the postglacial uplift of both fennoscandia the classic haskell 1935 number and hudson bay which have commonly been invoked to argue for an isoviscous mantle furthermore the models are used to predict a set of long wavelength signatures of the gia process these include predictions of gia induced variations in 1 the length of day over the late holocene period 2 the earth s precession constant and obliquity over the last 2 6 myr and 3 the present day zonal harmonics of the geopotential jl l 7 the predictions 1 and 3 bound the late holocene and ongoing mass flux between the large polar ice sheets greenland and antarctic and the global oceans to small values 0 4 mm yr equivalent eustatic sea level rise

measurement of surface currents using sequential synthetic aperture radar images of slick patterns near the edge of the gulf stream two dimensional surface currents are estimated over an area of 100 km2 near the inshore edge of the gulf stream by correlating the surface slick patterns observed on two synthetic aperture radar sar images collected about 20 min apart the currents obtained from this analysis are found to agree well with shipboard acoustic doppler current profiler adcp measurements at 10 to 20 m depths the orientations of the long linear slicks observed in this region differ from the mean current direction by about 16 but coincide with the direction of maximum radial deformation or strain as calculated from the observed current field the calculated current gradients indicate a mean surface convergence of about 2 10 5 s 1 and a cyclonic vorticity of about 1 10 4 s 1 values which fall within the range of previous estimates in the study area these results suggest that slick patterns may be used to infer surface current magnitude and direction from a time sequence of sar images but that care must be exercised in inferring current directions from the orientations of slick patterns within a single image

sea surface velocities in shallow seas extracted from sequential coastal zone color scanner satellite data sequential images of visible wavelength reflectance from channel 3 540 560 nm of the coastal zone color scanner czcs have been used for computing advective velocities in the eastern english channel using the maximum cross correlation technique the computation method known as matched filtering is widely used by meteorologists and has recently been applied by oceanographers to detect sea surface motion from satellite infrared images provided accurate coregistration of images is achieved by matching ground control points significant correlation is obtained when the technique is applied to czcs data and coherent velocity distributions are obtained for united kingdom shelf waters the residual circulation patterns for the english channel are found to be consistent with previous studies and recent observations

unique spinel rich lithology in lunar meteorite alha 81005 origin and possible connection to m3 observations of the farside highlands 1 a new lunar rock type rich in mg fe al spinel and lacking abundant olivine and pyroxene was recently detected by near infrared reflectance spectroscopy by the m3 instrument on the chandrayaan 1 spacecraft no such material has been described from lunar rocks either returned samples or meteorites here we describe a fragment of rock containing 30 mg fe al spinel from the lunar meteorite alha 81005 although the fragment is not identical to the material detected by m3 it contains 20 olivine pyroxene both share the defining feature of an unusual enrichment in spinel the fragment 350 150 m is so fine grained that it reasonably could represent a larger rock body it is not spinel rich merely by chance incorporation of a few spinel grains the fragment is so rich in spinel and consequently in al2o3 that it could not have formed by melting a peridotitic mantle or a basaltic lunar crust the clast s small grain size and its apparent disequilibrium between spinel and pyroxene suggest fairly rapid crystallization at low pressure it could have formed as a spinel cumulate from an impact melt of troctolitic composition or from a picritic magma body that assimilated crustal anorthosite on its margins the latter mechanism is preferred because it not only explains the petrographic and chemical features of our clast but is also consistent with the regional setting of the moscoviense spinel deposit in that area m3 spectra have defined areas rich in olivine and in orthopyroxene these could represent igneous cumulate rocks formed during crystallization and differentiation of a picritic magma body and thus suggests a possible link between the analyzed clast and the observed spinels at moscoviense

the discovery and initial characterization of allan hills 81005 the first lunar meteorite antarctic meteorite alha81005 discovered in the allan hills region of victoria land is a polymict anorthositic breccia which differs from other meteorites in mineralogical and chemical composition but is strikingly similar to lunar highlands soil breccias the petrologic character and several independent lines of evidence identify alha81005 as a meteorite from the moon two small clasts of probable mare basalt occur among the highlands lithologies in thin section 81005 22 this lunar specimen which shows relatively minor shock effects has generated new ideas on the types of planetary samples we may find on the earth and has added fresh excitement to the antarctic meteorite program

xenolith digestion in large magma bodies xenolith digestion during sinking in a corrosive magma is treated with a surface controlled dissolution relation suggested from recent experiments on silicate crystals the relation is shown to apply to a wide range of dynamical regimes from analog experiments on nacl dissolution in water using this relation xenolith penetration by sinking into magmas is shown to be strongly dependent on xenolith size crystal sinking is unimportant but sinking of meter sized chunks can be a major process of mass and heat transport in planetary scale magma body evolution this evolution cannot be adequately treated with current information

an objective method for computing advective surface velocities from sequential infrared satellite images using cross correlations between sequential infrared satellite images an objective technique is developed to compute advective sea surface velocities cross correlations are computed in 32 x 32 pixel search second image and 22 x 22 template first image windows from gradients of sea surface temperature computed from the satellite images velocity vectors computed from sequential images of the british columbia coastal ocean generally appear coherent and consistent with the seasonal surface current in the region during periods of strong wind forcing as indicated by maps of sea level pressure the image advective velocities are stronger and more coherent spatially and appear to cross surface temperature gradients when winds are weaker the advective velocities correspond better with the infrared temperature patterns suggesting the increased contribution of the geostrophic current to the surface flow velocities determined from coincident near surface drogued 5 10 m buoys positioned every half hour by internal loran c units in mid june show excellent agreement with the image advective velocities in addition conductivity temperature and depth ctd measurements taken during the buoy tracking confirm the homogeneity of the upper 10 m and ctd derived geostrophic currents are consistent with

vertical deformation and absolute gravity summary crustal deformation in the greenland and antarctic areas is strongly influenced by both postglacial rebound and contemporary mass redistribution we explore the relationship between the displacement field and the gravitational disturbance for a viscoelastic maxwell earth with an arbitrary radial viscosity profile we seek to determine whether the effects of viscous relaxation in the memory of surface mass change can be separated from the effects of present day mass variation by combined measurements of vertical displacement and absolute gravity when the viscosity profile in the earth s interior is unknown our conclusion is positive specifically the non elastic effects can be reduced substantially by combined measurements of displacement and gravity change for a maxwell viscoelastic earth regardless of its radial viscosity profile the underlying physics has nothing to do with the mathematical structure of viscous relaxation modes rather it is due to the fact that the non elastic response of a maxwell earth is nearly incompressible

influence of mantle compressibility and ocean warping on dynamical models of the geoid summary the influence of mantle compressibility and warping of the ocean surface on dynamical models of the geoid has been investigated topography and geoid kernels show that compressibility modifies the mantle flow pattern and hence the geoid whereas the deflection of the oceanic surface amplifies the geoid signal without affecting the global flow the combined influence of these two effects is significant and depends on the viscosity profile in the mantle comparisons with incompressible dynamical geoids show that including the effects of compressibility and ocean warping improves the fit to the observed geoid thus these effects must not be neglected in dynamical computations of the geoid

basaltic diversity at the apollo 12 landing site inferences from petrologic examinations of the soil sample 12003 a detailed petrologic survey has been made of 17 basaltic chips sized between 1 and 10 mm from the 12003 soil sample as part of an ongoing study of basaltic diversity at the apollo 12 landing site an attempt has been made to classify these samples according to the well established grouping of olivine pigeonite ilmenite and feldspathic basalts particular attention has been paid to variations in major minor and trace element mineral chemistry determined by electron microprobe analysis and laser ablation icp ms which may be indicative of particular basaltic suites and less susceptible to sampling bias than bulk sample characteristics examples of all three main olivine pigeonite and ilmenite basaltic suites have been identified within the 12003 soil one sample is identified as a possible new addition to the feldspathic suite which currently consists of only one other confirmed sample identification of additional feldspathic basalts strengthens the argument that they represent a poorly sampled basaltic flow local to the apollo 12 site rather than exotic material introduced to the site by impact mixing processes three samples are identified as representing members of one or two previously unrecognized basaltic suites

a singularity free approach to post glacial rebound calculations calculating the post glacial response of a viscoelastic earth model using the exponential decay normal mode technique leads to intrinsic singularities if viscosity varies continuously as a function of radius we develop a numerical implementation of the complex real fourier transform crft method as an accurate and stable procedure to avoid these singularities using crft we investigate the response of a set of maxwell earth models to surface loading we find that the effect of expanding a layered viscosity structure into a continuously varying structure is to destroy the modes associated with the boundary between layers horizontal motion is more sensitive than vertical motion to the viscosity structure just below the lithosphere horizontal motion is less sensitive to the viscosity of the lower mantle than the vertical motion is when the viscosity increases at 670 km depth by a factor of about 60 the response of the lower mantle is close to its elastic limit any further increase of the viscosity contrast at 670 km depth or further increase of viscosity as a continuous function of depth starting from 670 km depth is unlikely to be resolved

the viscoelastic relaxation of a realistically stratified earth and a further analysis of postglacial rebound summary we discuss the isostatic adjustment of the earth in response to pleistocene deglaciation and derive constraints on the earth s viscosity profile we model the earth as viscoelastic self gravitating realistically stratified and spherically symmetric it is shown that the earth s relaxation eigenspectrum besides possessing a small set of well known discrete modes also includes infinitely dense sets of modes a continuous spectrum which separate into classes that depend on the principal restoring force of the mode methods for estimating the continuous spectrum are discussed and the effects on the predicted uplift are assessed we find that the effects of the continuous spectrum are far less important than those of the discrete modes though the presence of the continuous spectrum can make the discrete modes more difficult to identify the continuous spectrum does become important when computing the rebound due to more recent loading such as might be associated with present day changes in polar ice we use our model to refine predictions of the earth s response to pleistocene glacial loading with particular emphasis on implications for mantle viscosity we have used time histories that are consistent with the recently recalibrated 14c time scale a special effort is made to match the geologic records of sea level at sites in the vicinity of hudson bay we find consistent with the results of other authors that the curvatures of the records are sensitive indicators of lower mantle viscosity but that there are inconsistencies between the records at different sites however we find we are also able to change the predicted curvatures by modifying the temporal and spatial distribution of the ice loads if we assume a factor of 50 increase in viscosity between the upper and lower mantles and if we assume that the ice on the eastern side of hudson bay melted a few thousand years later than the ice on the western side a result consistent with recent geologic evidence we are able to match the observed sea level data about as well as we are able to if we use instead a uniform mantle viscosity profile a model with a factor of 50 jump in viscosity predicts a large free air gravity anomaly over northern canada that is reasonably consistent with what is observed whereas a uniform viscosity model does not though some authors have argued that the observed north american gravity anomaly may be mostly a consequence of mantle convection and largely unrelated to postglacial rebound our objective here is not to present a preferred ice model or viscosity profile rather we conclude only that the interpretation of the data is ambiguous and that the mantle viscosity profile can not yet be uniquely inferred from them

spectral finite element approach to viscoelastic relaxation in a spherical compressible earth application to gia modelling summary the choice of the physical model of postglacial rebound plays a decisive role to derive information about the mantle rheology and viscosity from observed data in models for the mantle rheology an incompressible maxwell material is often assumed in spite of seismic observations showing that the earth s mantle is composed of compressible material in this study in order to assess the influence of compressibility on glacial isostatic adjustment gia the spectral finite element approach proposed by martinec is extended to incorporate the effect of compressibility using this approach the present day velocity field is computed for peltier s ice5g vm2 earth model glaciation history combination considering the sea level equation in the formulation of hagedoorn et al the results show that the effect of compressibility on the vertical displacement rate is small whereas the horizontal rates are markedly enhanced for example the rate around fennoscandia and laurentide becomes twice as large when compressibility is considered this large difference between the compressible and incompressible models can be reduced by adjusting the elastic rigidity of the incompressible model so that the flexural rigidity becomes approximately the same as that in the compressible model however differences of 1 mm yr 1 still remain for wavelengths longer than 8000 km these findings show that when modelling horizontal motion induced by gia the influence of compressibility cannot be neglected

origin of olivine at copernicus the central peaks of copernicus are among the few lunar areas where near infrared telescopic reflectance spectra indicate extensive exposures of olivine other parts of copernicus crater and ejecta which were derived from highland units in the upper parts of the target site contain only low ca pyroxene as a mafic mineral the exposure of compositionally distinct layers including the presence of extensive olivine may result from penetration to an anomalously deep layer of the crust or to the lunar mantle we suggest that the procellarum basin and the younger superposed insularum basin have provided access to these normally deep seated crustal or mantle materials by thinning the upper crustal material early in lunar history the occurrences of olivine in portions of the compositionally heterogeneous aristarchus region in a related geologic setting may be due to the same sequence of early events

glacial rebound and relative sea level variations a new appraisal summary late pleistocene and holocene changes in sea level at technically stable shorelines contain information on the melting history of the ice sheets and on the response of the earth to changes in surface loads on time scales of 104yr some separation of parameters defining the ice loads and the earth s response can be achieved by examining sea level change at different sites around the world and at different epochs this paper examines the mathematical requirements for obtaining satisfactory solutions for the sea level equation rather than emphasizing results for the earth s response to the surface loads an examination of the equation expressing the sea level variation on a viscoelastic earth indicates that careful consideration needs to be given to both the definition of the ice load and the geometry of the redistributed water load if geophysically significant earth response parameters are to be deduced from observations of relative sea level the spectrum of the 5 x 5 area mean description of the ice load widely used in glacial rebound studies contains significant power at high degrees n 30 and can result in substantial spatial variations in sea level unless a thick lithosphere is introduced in the earth s response function a smoothed 1 1 description of the ice model avoids these high degree oscillations in relative sea level and produces satisfactory sea level results without requiring a thick lithosphere at far field sites the holocene sea levels are sensitive to the earth s response to the meltwater loading in the vicinity of the site and a high degree spatial resolution of coastline geometry is required to model the mantle flow driven by the differential loading about the site at some sites convergence of the solution to the sea level equation is not obtained even when the solution is expanded to degree 180 convergent solutions at lower degrees can be achieved by introducing earth models with a moderately thick lithosphere if high resolution ice and meltwater load models are not used then the tendency will be to overestimate the effective elastic thickness of the lithosphere estimates of mantle viscosity are also of questionable value if these high resolution models are not used a preliminary examination of sea levels at sites in both the near and far field places an upper limit of about 50 80 km on the effective lithospheric thickness these sea level observations are also consistent with an upper mantle viscosity of about 1021 pas with a lower mantle viscosity in the range of 1021 1023pa s

post glacial relaxation of a viscously stratified compressible mantle summary we investigate the post glacial relaxation phenomenon of a viscously compressible non self gravitating spherical shell model we have developed analytical solutions to an exponentially depth dependent viscosity with various types of compressible density models such as those with an exponential dependence of the radius and an algebraic root dependence of the radius the solutions of a viscously compressible multilayered model with constant thermodynamic properties and viscosity are developed by the propagator matrix method our results show that inferences of deep mantle viscosity from post glacial rebound would be hampered by mantle compressibility for long wavelength harmonics because of the smaller excitation of compressible eigenfunctions in the lower mantle the relaxation times and velocity fields are more sensitive to higher viscosity contrast for the exponentially varying viscosity than for models with discrete jumps in the viscosity structure stress fields associated with deglaciation are extremely sensitive to the underlying mantle viscosity structure large stresses o 102 bar can still remain at the deglaciated region if the lower mantle viscosity is o 1023p the presence of a hard garnet layer in the transition zone will induce a smaller viscosity in the lower mantle in the viscosity trade off with the standard two layer model

viscoelastic perturbations of the earth significance of the incremental gravitational force in models of glacial isostasy summary the incremental gravitational force igf arises from perturbations of the earth s gravitational potential in glacial isostasy its sources are the surjicial and internal mass redistributions associated with the growth and decay of the continental ice sheets we examine the errors caused by the neglect of the igf using closed form solutions of the equations governing surface load induced perturbations of two types of incompressible spherical earth models 1 maxwellian viscoelastic mantle enclosed by elastic lithosphere and 2 maxwellian viscoelustic mantle enclosing inviscid core calculations in the legendre domain of the radial surface displacement for these models show that neglecting the igf causes enhancement of the elastic response and acceleration of the viscous relaxation in the space domain these changes entail corresponding modifications of the calculated land adjustment the magnitude of the error caused by the neglect of the igf strongly depends on the deglaciation history and load radius adopted assuming a typical deglaciation history the error reaches a maximum of less than 20 m at the end of the deglaciation phase for loads comparable in size to the canadian or the fennoscandian ice sheets we also compare sphericul earth models with igf and plane earth models without igf calculations of the radial surface displacement show that the errors due to the neglect of sphericity and the igf partially compensate each other taking the uncertainties of the observational data into account we conclude that the majority of the canadian and fennoscandian glacial isostatic adjustment data can be modelled with sufficient accuracy using a plane earth model without igf

effects due to compressional and compositional density stratification on load induced maxwell viscoelastic perturbations summary calculations of viscoelastic perturbations of an incompressible uid earth initially in hydrostatic equilibrium have been conventionally based on models consisting of isocompositional layers a special case is the incompressible isocompositional half space for which the initial density distribution is spatially uniform one of the de ciencies of this model is that it ignores the increase of the initial density with depth in the earth s interior due to compressional and compositional strati cation the presentstudy is concernedwith load induced maxwellviscoelastic perturbations of a half space with a compressional and compositional initial density gradient analytic solutions to this problem are deduced for the limiting cases of purely compressional strati cation earth model p and purely compositional strati cation earth model c the comparison of the solutions for these earth models with that for the special case of no density strati cation earth model r shows that eiects due to the initial density gradient become important for perturbations whose lateral scale length exceeds about 10 3 km using axisymmetric models of the pleistocene fennoscandian and canadian ice sheets and considering the vertical surface displacements near the load axes the maximum diierences are found to be about 10 m fennoscandia or 35 m canada at the beginning of relaxation for earth models p and r and about 50 m fennoscandia or 150 m canada at intermediate times of relaxation for earth models c and r

initial value and modal approaches for transient viscoelastic responses with complex viscosity profiles summary an initial value theory is proposed for studying viscoelastic responses of compressible earth models with complex viscosity profiles continuous spectra are caused by both compressibility and the viscosity stratification and they can cause numerical difficulties for the modal approach we have studied the different responses for various types of viscosity profiles and found that there are differences in the responses at short wavelengths for viscosity profiles with sharp low viscosity zones we found that many modes are required to match the full initial value solutions in the presence of sharp viscosity stratifications in both the upper and lower mantle the normal mode approach is best suited for simple layered models long wavelengths and timescales greater than several thousand years while the initial value approach is indispensable in treating short timescale problems with sharp low viscosity zones in the upper mantle and viscosity stratification in the lower mantle

comparison of airborne synthetic aperture radar imagery with in situ surface slope measurements across gulf stream slicks and a convergent front synthetic aperture radar sar imagery showing two types of features near the inshore edge of the gulf stream are compared with nearly simultaneous estimates of the sea surface slope field derived from optical shipboard measurements one class of feature consists of a set of narrow dark lines having radar signal modulations of about 10 db at l band these modulations are comparable to those observed in the in situ wave slope data over wavenumbers corresponding to the radar resonant bragg waves these modulations are also predicted by a simplified equilibrium wave spectrum model using a surface elasticity of about 25 mn m as determined from in situ measurements of surface tension and a wind friction velocity of about 10 cm s from buoy and shipboard measurements these results support lyzenga and marmorino s 1998 inference that the gulf stream dark lines represent relatively passive biogenically derived surfactant slicks that are advected and strained by the large scale surface flow field the second class of feature consists of a pair of bright dark signatures over the shallow continental shelf region near cape hatteras north carolina these features are characterized by signal modulations of about 4 and 4 db in both the l band sar and in situ data these modulations appear to be due to the interaction of surface waves with the current convergence and divergence regions associated with a rotary circulation in a shallow convergent front model calculations of this interaction by lyzenga 1998 indicate that the positive perturbations associated with current convergence should be relatively independent of the wavenumber which is in approximate agreement with the in situ measurements of the present paper the model also indicates that the negative perturbations associated with the region of current divergence should decrease for wavenumbers higher than l band that trend is observed in the sar data but not in the in situ data which show significant perturbations at higher wavenumbers it is conjectured that this is due to the effects of surfactants and either along front or time variability in the frontal dynamics which are not included in the model additional comparisons of this kind should be useful to further test and improve physical models of near surface phenomena

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

mesoscale variability in the alboran sea synthetic aperture radar imaging of frontal eddies in autumn 1992 the entire alboran sea western mediterranean was sampled by the spanish r v garcia del cid the incoming jet of atlantic water its associated meandering front and the two big anticyclonic gyres were described from conductivity temperature depth ctd and acoustic doppler current profiler adcp data smaller scale eddies were also observed additionally 36 ers 1 synthetic aperture radar sar scenes were obtained from mid september to mid october the sar images capture these features when wind conditions are suitable the current shear is mainly depicted as narrow lines of low backscatter because of the damping of waves by natural surface films these lines delineate the northern border of both gyres and the beginning of the alongslope algerian current at the eastern limit of the alboran sea adcp observations confirm that lines on sar imagery follow the direction of the surface currents the two gyres present high backscatter values in their center while their frontal boundaries appear modulated by the variation of the marine atmospheric boundary layer stratification due to the surface thermal front sar has observed small spiral eddies that were not evidenced by the almost contemporaneous but too coarse ctd in situ sampling good spatial correspondence between radar detected and in situ measured structures occurs when comparing sar images to the surface dynamic topography rather than strictly surface water characteristics

gulf stream kinematics along an isopycnal float trajectory abstract an isopycnal following float was deployed near the 400 m depth level in the high speed jet region of the gulf stream and tracked for approximately 300 km from the blake plateau towards cape hatteras during 16 19 may 1983 during its transit through a 400 change in bottom depth the layer tagged by the float was surveyed with xbts and hydrostations and the surface mesoscale structure was determined from noaa 6 7 and 8 ir imagery these data provide the first three dimensional observations of water parcel motion along a gulf stream trajectory in the upper main thermocline approaching path segments with anticyclonic curvature flow in the surrounding stream volume was divergent and vertically compressed approaching path segments with cyclonic curvature the flow in the surrounding stream volume was divergent and vertically compressed approaching path segments with cyclonic curvature the flow in the surrounding steam volume was convergent and vertically stretched the float was upwelled approa

airborne synthetic aperture radar observations of spiral eddy slick patterns in the southern california bight 1 repeat sampling on hourly time scales using an airborne synthetic aperture radar sar is used to investigate the occurrence and evolving characteristics of spiral shaped slick patterns commonly presumed to be indicators of submesoscale ocean eddies in the area around santa catalina island california 33 4 n 118 4 w simultaneous sar imagery and boat survey data are examined over two 5 h long periods spaced 3 days apart in april 2003 the sar imagery reveals several spiral like patterns roughly 5 km in diameter occurring downstream of the western end of catalina we believe that the most likely formation mechanism for these patterns is current wake instability related to the flow of the southern california countercurrent along the north shore of catalina in one case there is an observed cold core eddy and vortex sheet attached to the tip of the island similar to island wake simulations done by dong and mcwilliams 2007 in another case the sar imagery shows a series of slick patterns that at least initially resemble spiral eddies but the data show no clear evidence of actual ocean eddies being present either at depth or through a rotating surface expression a speculation is that such features signify island wake eddies that are relatively weak and dissipate quickly an unexpected finding was how quickly a spiral slick pattern could deteriorate suggesting a time scale for the surface feature of the order of only several hours an implication of this result is that care is needed when interpreting a single satellite sar imagery for evidence of active submesoscale eddies recommendations are made for future field studies

understanding the effects of mantle compressibility on geoid kernels summary we develop a quasi analytical solution to compute geoid kernels for a compressible mantle with newtonian rheology by separating the stresses induced by self gravitation from the stresses resulting from viscous flow we simplify the equations and gain some insight for realistic variations in the background density field po r the solution obtained using propagator matrices converges rapidly compressibility enters into the flow problem directly through the continuity equation and indirectly by influencing parameters such as gravitational acceleration g r and density contrasts across compositional boundaries in order to understand all these effects we introduce them sequentially starting with an incompressible earth model and ending up with a realistic compressible model that includes a compressible inner and outer core phase changes in the transition zone and an ocean the largest effects on geoid kernels are from different assumptions for g r possible effects of transformational superplasticity and differences in assumptions for density contrasts at the surface and at the core mantle boundary are next in importance the effects of compressibility on the flow itself are somewhat smaller followed by the effect of compressibility of the outer core a gravitationally consistent treatment of the ocean layer yields geoid kernels that are very similar to those for a dry planet the compressibility of the inner core has a negligible impact on the geoid kernels the largest effects from compressibility are comparable to the effects of a moderate 40 per cent change in the viscosity contrast between the upper and lower mantle

scientific objectives of current and future wegener activities abstract the wegener group has promoted the development of scientific space geodetic activities in the mediterranean and in the european area for the last fifteen years and has contributed to the establishment of geodetic networks designed particularly for earth science research wegener currently has three scientific objectives which are related to plate boundary processes sea level and height changes and postglacial rebound in a full exploitation of the space geodetic techniques namely slr vlbi and gps the individual scientific projects do not only pursue these objectives but also contribute to improving and developing the observation techniques as well as the modelling theories in the past particularly slr observations within wegener medlas have provided a fundamental contribution to determine the regional kinematics of the tectonic plates in the mediterranean with high precision with gps spatially denser site distributions are feasible and in several wegener projects detailed studies of tectonically active areas were possible on the basis of repeated episodic gps observations current projects associated with wegener are successful in separating crustal movements and absolute sea level variations as well as in monitoring postglacial rebound these tasks require high precision height determinations a problem central to all of the present wegener activities in these projects continuously occupied gps sites are of increasing importance time series of heights observed with continuous gps can be determined with a few centimeters rms error thus enabling the reliable estimates of vertical rates over relatively short time intervals regional networks of continuous gps sites are already providing results relevant for example for the study of postglacial rebound the mediterranean area is an extraordinary natural laboratory for the study of seismotectonic processes and the wealth of observations acquired in previous wegener projects together with new space geodetic observations will allow the test of geophysical hypotheses linking three dimensional deformations of the earth s surface to the dynamics of the earth s interior in particular it is anticipated that wegener projects will aim at a test of the slab detachment hypothesis the complex investigations on sea level fluctuations presently carried out at basin scale from the strait of gibraltar to the black sea make it possible to study the present and recent past interactions of ocean atmosphere and solid earth as well as to develop appropriate models to assess future aspects

derivation of sea surface tidal current from spaceborne sar constellation data in this paper we demonstrate an application of spaceborne synthetic aperture radar sar constellation data to derive sea surface tidal current at high spatial resolution the maximum cross correlation mcc method which has been widely applied to optical remote sensing data to derive sea surface velocities is applied to x band sar data from terrasar x tsx and tandem x tdx which were operating in pursuit monostatic mode because of the short temporal interval of tsx and tdx s pursuit acquisitions temporal de correlation is minimized to derive tidal current fields that exhibit significant temporal and spatial variations in addition we combined data from tdx and another x band sar cosmo skymed to obtain a virtual sar constellation data pair which was also analyzed using the mcc method to derive the tidal current field case studies of hangzhou bay in the east china sea and amrum island in the north sea are presented the sar derived tidal current fields were compared to the results of numerical model simulations high frequency hf radar measurements and in situ measurements mcc coefficients that are greater than 0 8 are an appropriate threshold for the further derivation of tidal currents comparisons to finite volume community ocean model hf radar and general estuarine transport model results yield root mean square errors of 0 13 0 06 and 0 05 m s respectively measurements from three field stations were also compared to the mcc sar retrievals yielding differences of 0 3 0 07 and 0 09 m s

the influence of the marine atmospheric boundary layer on ers 1 synthetic aperture radar imagery of the gulf stream in september 1991 the ers 1 synthetic aperture radar sar collected a set of four colocated images over the western gulf stream gs the sar images were supplemented by satellite infrared imagery and measurements of the marine atmospheric boundary layer mabl from both a pair of surface buoys and a suite of instrument on the ukrainian research vessel r v vernadsky which between september 15 and 19 made six transects across the gs northern boundary within the sar swaths the influence of wind variations within the mabl was evident in each of the four sar images evidence for thermal wind effects is seen in the changing character of the imagery as the mean wind across the sea surface temperature boundary changed direction from pass to pass both in situ data and analytical models suggest that much of the day to day sar image variability was the result of changes in the character of the mabl especially evident near the northern gs boundary where the sign of the atmospheric stability fluctuated over short spatial scales because many of the governing parameters of the mabl rapidly decorrelate significant changes in the sar imagery occurred during the 3 days between passes nevertheless at least some manifestation of the gs was evident in the sar imagery on each of the four passes

global postseismic gravity changes of a viscoelastic earth a spherically symmetric earth model with a viscoelastic mantle and an inviscid core is used to study the gravitational perturbation due to a lithospheric shear dislocation in the coseismic and postseismic regime our approach is based on a quasi static solution of the equilibrium equations taking advantage of the normal mode technique for a layered incompressible earth with linear viscoelastic rheology we perform a systematic study of space and time evolution of gravity changes associated with a wide selection of seismic sources investigating the effects of several different mantle viscosity profiles our results show that the gravitational signal is sensitive not only to the viscosity of the asthenosphere but also to that of the mantle including the portion below the 670 km discontinuity as a case study we compute the coseismic and postseismic gravity perturbation due to the 1964 alaska earthquake the last section is devoted to the analysis of the postseismic relaxation rates of the gravitational perturbation following that earthquake for several different viscosity profiles of the mantle our results show that experimental attempts to obtain reliable detection of static and quasi static gravitational perturbation associated with seismic events would be of great importance in understanding the dynamic and viscosity profile of both upper and lower mantle

reactive flow as dominant evolution process in the lowermost oceanic crust evidence from olivine of the pineto ophiolite corsica the jurassic pineto ophiolite from corsica exposes a 1 km thick troctolite olivine gabbro sequence interpreted to represent a lowermost sector of the gabbroic oceanic crust from a ultra slow spreading system to constrain the petrogenesis of the olivine gabbros minor and trace element analyses of olivine forsterite 84 82 mol were carried out olivine from the olivine gabbros is depleted in incompatible trace elements sc v ti y zr and heavy rare earth elements with respect to olivines from associated troctolites depleted incompatible element compositions are also shown by olivine forsterite 86 mol from a clinopyroxene rich troctolite the incompatible element compositions of olivine argue against a petrogenetic process entirely driven by fractional crystallization we propose that melts migrating through an olivine plagioclase crystal mush chemically evolved by reaction with the existing minerals changing in composition as it flowed upward the melt residual from these interactions led to partial dissolution of preexisting olivine and to crystallization of clinopyroxene generating olivine gabbro bodies within a troctolite matrix reactive flow was the major evolution process active in the 1 km crustal transect exposed at the pineto ophiolite producing lithological variations classically attributed to fractional crystallization processes

a new method for the computation of global viscoelastic post seismic deformation in a realistic earth model i vertical displacement and gravity variation summary we introduce a new method by which to compute global post seismic deformation psd in a spherically symmetric self gravitating viscoelastic earth model previous methods are based on simplified earth models that neglect compressibility and or the continuous variation of the radial structure of earth this is because the previous mode summation technique cannot avoid intrinsic numerical difficulties caused by the innumerable poles that appear in a realistic earth model that considers such effects in contrast the proposed method enables both of these effects to be taken into account simultaneously we carry out numerical inverse laplace integration which allows evaluation of the contribution from all of the innumerable modes of the realistic earth model using this method a complete set of green s functions is obtained including functions of the time variation of the displacement gravity change and the geoid height change at the surface for strike slip dip slip horizontal and vertical tensile point dislocations as an earth model we employ the preliminary reference earth model prem and a convex viscosity profile further we investigate the effects of fine layering of the viscoelastic structure and compressibility on a time series of psd using the green s function for a dip slip fault the result indicates that the effect of increasing number of layers is saturated at several tens of layers even when compressibility is taken into account and that the effect of compressibility is detectable with modern observational techniques for a shallower large earthquake mw 8 as an application the psd due to the sumatra andaman islands earthquake mw 9 3 is estimated we show that the rate of post seismic vertical displacement and gravity change is possibly detected in the far field where the epicentral distance exceeds 400 km

copernicus crater central peak lunar mountain of unique composition olivine is identified as the major mafic mineral in a central peak of copernicus crater information on the mineral assemblages of such unsampled lunar surface material is provided by near infrared reflectance spectra 0 7 to 2 5 micrometers obtained with earth based telescopes the composition of the deep seated material comprising the copernicus central peak is unique among measured areas other lunar terra areas and the wall of copernicus exhibit spectral characteristics of mineral assemblages comparable to the feldspathic breccias returned by the apollo missions with low calcium orthopyroxene being the major mafic mineral