pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle abstract the geoid low over french polynesia has been previously interpreted as the signature of an upper mantle upwelling associated with a low viscosity zone located immediately below the lithosphere we propose here an alternative explanation using new high quality satellite gravity data and fluid mechanics constraints we thus discuss the origin of the high concentration of hotspots in the central pacific which is still debated satellite gravity data from the grace mission analyzed with wavelets allow us to better characterize the geoid low on french polynesia and the large scale positive geoid anomaly 600 km east of the line islands chain we show that the geoid anomalies are consistent with thermochemical oscillating domes and we bring constraints on their density contrast and their upper limit depth under this hypothesis the central pacific mantle would contain two thermochemical instabilities at different stages of their development a rising dome lighter extending approximately from the cmb up to the transition zone beneath the south pacific superswell toped by secondary plumes that generate short lived hot spot chains and a sinking dome denser in the lower mantle beneath the area located 600 km east of the line islands chain plate reconstructions further show that the latter could also have generated the southern line islands 35 m y ago and shatsky rise 140 m y ago when it was in its ascending phase while the south pacific dome probably created darwin rise 100 m y ago in a same type of event

unsolved problems in the lowermost mantle 1 many characteristics of d layer may be attributed to the recently discovered mgsio3 post perovskite phase without chemical heterogeneities they include a sharp discontinuity at the top of d regional variation in seismic anisotropy and a steep clapeyron slope however some features remain unexplained the seismically inferred velocity jump is too large in comparison to first principles calculations and the sharpness of the discontinuity may require a chemical boundary chemical heterogeneity may play an important role in addition to the phase transformation from perovskite to post perovskite phase transformation and chemical heterogeneity and the attendant changes in physical properties such as rheology and thermal conductivity are likely to play competing roles in defining the dynamical stability of the d layer revealing the relative roles between phase transition and chemical anomalies is an outstanding challenge in the study of the role of d in thermal chemical evolution of the earth

the relationships between large scale variations in shear velocity density and compressional velocity in the earth s mantle a large data set of surface wave phase anomalies body wave travel times normal mode splitting functions and long period waveforms is used to investigate the scaling between shear velocity density and compressional velocity in the earth s mantle we introduce a methodology that allows construction of joint models with various levels of scaling complexity d ln d lnvs d lnvs d lnvp in order to detect seismological signatures of chemical heterogeneity we demonstrate that the data sets considered cannot be fit concurrently with a uniform or a positive and uniform throughout the mantle the variance reductions to p wave travel times and vp sensitive modes are up to 40 higher with our preferred model of anisotropic shear and compressional velocity than the recent anisotropic shear velocity model s362ani m which was constructed assuming a uniform throughout the mantle several features reported in earlier tomographic studies persist after the inclusion of new and larger data sets anticorrelation between bulk sound and shear velocities in the lowermost mantle as well as an increase in with depth in the lower mantle are largely independent of the regularization scheme when correlations between density and shear velocity variations are imposed in the lowermost mantle variance reductions of several spheroidal and toroidal modes deteriorate by as much as 40 recent measurements of the splitting of 0s2 in particular are largely incompatible with perfectly correlated shear velocity and density heterogeneity throughout the mantle a way to significantly improve the fits to various data sets is by allowing independent density perturbations in the lowermost mantle our preferred joint model consists of denser than average anomalies 1 peak to peak at the base of the mantle roughly coincident with the low velocity superplumes the relative variation of shear velocity density and compressional velocity in our study disfavors a purely thermal contribution to heterogeneity in the lowermost mantle with implications for the long term stability and evolution of superplumes

a new approach to interpreting rock eval s2 and toc data for kerogen quality assessment abstract a simple method for application in source potential mapping is used to assess the original oil and gas potentials in source rock horizons based upon rock eval potential s 2 and total organic carbon toc values the method assumes that kerogens consist of mixtures of end members with assigned hydrogen index values based on suggested algorithms the average amounts of oil prone gas prone and inert organic material over source rock intervals are determined in toc units the method uses regression lines from plots of remaining hydrocarbon potentials s 2 versus total organic carbon toc and quick look transparent overlays are used to read the appropriate kerogen mixture mineral matrix effects during pyrolysis when strong can cause erroneous results this effect which occurs for oil prone kerogens and adsorptive minerals can cause problems particularly for lean samples s 2 0 3 mg hc g rock whilst the errors for richer samples are less the method is applied on three sections of upper jurassic organic rich rocks from the danish north sea sector which are at different maturity stages one of these sections is dominated by gas prone material one is dominated by oil prone material and the third section contains a mixture of oil and gas prone material the method has been compared with other methods that split kerogens in oil and gas generating potential and has given reasonable results experience using the method and a presented example suggest that sedimentological system tract information may be derived from s 2 to toc cross plots a constructed modelling example suggests that the end member concept used in this approach may be used in forward type source rock prediction models when combined with sedimentological models the resulting s 2 toc plots can be used in order to check the forward modelling results against observed values

seismic and mineralogical structures of the lower mantle from probabilistic tomography 1 one of the most powerful approaches for understanding the 3 d thermo chemical structure of the lower mantle is to link tomographic models with mineral physics data this is not straightforward because of strong trade offs between thermal and chemical structures and their influence on seismic structures they can be reduced by mapping simultaneously perturbations of wave speeds and density anomalies and by the quantitative assessment of the accuracy and uniqueness of seismic and mineralogical data here we present new tomographic maps of low order even degree seismic structures which are an improvement on earlier models they satisfy constraints from body wave surface wave and normal mode data simultaneously thereby enhancing the spatial resolution furthermore the seismic structure at a given location is represented by a probability density function pdf which takes into account the uncertainty and non uniqueness of the solution due to modeling and data restrictions following a robust statistical procedure we fit heterogeneity of wave speeds and density from hypothetical thermo chemical models to those of our tomographic maps we thereby constrain lateral variations of temperature as well as iron silica and post perovskite concentration in terms of pdfs our work shows that large scale chemical variations are likely everywhere in the lower mantle in most of the d region post perovskite is most abundant in the circum pacific belt but near the core its lateral variation is more complex furthermore post perovskite concentration trades off with the amplitudes of temperature and silicate variations but not with their lateral distribution this might be the reason why temperature and silicate variations appear not constrained by our data in the lowermost few hundred km of the mantle

geographic boundary of the pacific anomaly and its geometry and transitional structure in the north 1 we determine the geographical boundary and average shear velocity structure of the pacific anomaly at the base of the mantle based on travel time analysis of scsh sh and scs2 scsscs ss phases and waveform modeling results we further constrain the detailed geometry of the northern anomaly around 20 n 170 e and its transition to the surrounding high velocity region along three perpendicular cross sections on the basis of forward waveform modeling of the observed direct s and scs phases the observed differential travel time residuals and waveform modeling results allow the whole geographic boundary of the anomaly to be delineated and the area of the base of the anomaly is estimated to be 1 9 107 km2 the maximum shear velocity perturbation inside the anomaly reaches 5 in the lowermost 500 km of the mantle waveform analysis suggests that the northern anomaly reaches 450 km above the cmb with both steeply and shallowly dipping edges and its basal layer extends beneath the surrounding mantle with the degree of extension changing rapidly across a small distance the inferred characteristics of the anomaly support the previous suggestion that the pacific anomaly represents a chemical anomaly however unlike the inferred features of the african anomaly pointing to an ancient compositionally distinct and geologically stable anomaly the existence of several separated piles extending into the mid lower mantle the complex morphology of the piles with both steeply and shallowly dipping edges and the presence of many ultra low velocity zones at its base suggest that the pacific anomaly likely possesses varying intrinsic compositions and exhibits complex interaction with the surrounding mantle

constraints on the presence of post perovskite in earth s lowermost mantle from tomographic geodynamic model comparisons abstract lower mantle tomography models consistently feature an increase in the ratio of shear wave velocity v s to compressional wave velocity v p variations and a negative correlation between shear wave and bulk sound velocity v c variations these seismic characteristics also observed in the recent sp12rts model have been interpreted to be indicative of large scale chemical variations other explanations such as the lower mantle post perovskite ppv phase which would not require chemical heterogeneity have been explored less constraining the origin of these seismic features is important as geodynamic simulations predict a fundamentally different style of mantle convection under both scenarios here we investigate to what extent the presence of ppv explains the observed high v s v p ratios and negative v s v c correlation globally we compare the statistical properties of sp12rts with the statistics of synthetic tomography models derived from both thermal and thermochemical models of 3 d global mantle convection we convert the temperature fields of these models into seismic velocity structures using mineral physics lookup tables with and without ppv we account for the limited tomographic resolution of sp12rts using its resolution operator for both v s and v p structures this allows for direct comparisons of the resulting velocity ratios and correlations although the tomographic filtering significantly affects the synthetic tomography images we demonstrate that the effect of ppv remains evident in the ratios and correlations of seismic velocities we find that lateral variations in the presence of ppv have a dominant influence on the v s v p ratio and v s v c correlation which are thus unsuitable measures to constrain the presence of large scale chemical variations in the lowermost mantle to explain the decrease in the v s v p ratio of sp12rts close to the cmb our results favour a ppv bearing cmb region which has implications for the stability field of ppv in the earth s mantle

organic geochemistry and petrography of lower cretaceous wealden black shales of the lower saxony basin the transition from lacustrine oil shales to gas shales abstract ninety seven wealden black shale samples from three wells in the lower saxony basin have been studied by organic geochemical and organic petrographical methods to determine their maturity organic facies and depositional environment the maturities of the three wells range from early mature ex a late to postmature ex c to overmature ex b as determined by vitrinite reflectance measurements diamondoid ratios and other geochemical maturity parameters ex c and ex b show distinct petrographic features related to oil generation and migration in particular the occurrence of dispersed solid bitumen replacing initial type i kerogen suggests a formerly active petroleum system structural and textural differences between early mature alginites and solid bitumen in postmature to overmature samples show an alteration of the pore system with increasing maturity a freshwater depositional environment is indicated by widespread occurrence of botryococcus algae and other small alginite particles predominating in the immature well these alginites are absent in the more mature gas shales of wells ex c and ex b geochemical evidence of algae and phytoplankton in general is provided by numerous biomarker parameters while the occurrence of carotane in some samples indicates events of increased salinity although no hypersaline conditions are inferred due to very low gammacerane indices increased amounts of vitrinite and inertinite in samples of ex b suggest locally significant terrigenous input of organic matter for some periods during wealden shale deposition high sulfur organic carbon ratios provide evidence for sulfate rich waters and partly anoxic bottom water conditions while the lower mature lacustrine source rocks generate paraffinic waxy oils gas and condensates are produced at post mature stages furthermore maturity distribution maps from 3d numerical petroleum systems modeling reveal substantial differences in respect to petroleum generation

sp12rts a degree 12 model of shear and compressional wave velocity for earth s mantle we present the new model sp12rts of isotropic shear wave vs and compressional wave vp velocity variations in the earth s mantle sp12rts is derived using the same methods as employed in the construction of the shear wave velocity models s20rts and s40rts and the same data types sp12rts includes additional traveltime measurements of p waves and new splitting measurements 33 normal modes with sensitivity to the compressional wave velocity and 9 stoneley modes with sensitivity primarily to the lowermost mantle contrary to s20rts and s40rts variations in vs and vp are determined without invoking scaling relationships lateral velocity variations in sp12rts are parametrised using spherical harmonics up to degree 12 to focus on long wavelength features of vs and vp and their ratio r largelow velocity provinces llvps are observed for both vs and vp sp12rts also features an increase of r up to 2500 km depth followed by a decrease towards the core mantle boundary a negative correlation between the shear wave and bulk sound velocity variations is observed for both the llvps and the surrounding mantle these characteristics can be explained by the presence of post perovskite or large scale chemical heterogeneity in the lower mantle

s to p heterogeneity ratio in the lower mantle and thermo chemical implications we evaluate the thermo chemical state of the lower mantle by analysing the differences in the pattern of heterogeneity between shear and compressional velocity variations and the s to p heterogeneity ratio rs p lnvs lnvp as mapped in our model spani and in alternative joint models robust structural differences between vp and vs evidence the presence of compositional heterogeneity within the two large low shear velocity provinces llsvps we find also an increasing decorrelation with depth that can be associated with compositional layering of the llsvps in addition our model shows heterogeneity in the transition zone and mid mantle by complex morphology of subducting slabs and further differences between vp and vs that point to an unexpected heterogeneous lower mantle precise estimates of compositional heterogeneities are not yet affordable because of the difficulty to provide quantitative measure of rs p making it difficult to use this ratio to evaluate chemical heterogeneity for instance rs p global median value drops from 2 8 to 1 9 at 2500 km depth when the vp component of spani is replaced by a vp model resulting from a differently regularized inversion and obtaining an equally good data fit an increase of 20 of the spani vp anomalies also drastically reduces without significantly degrading the data fit noise in model parameters also leads to overestimate rs p in the two llsvps as we show with synthetic tests additional mineral physics uncertainties for compositional effects on rs p and for the conversion of lnvs and lnvp into density further complicates a precise chemical interpretation

joint inversion of normal mode and body wave data for inner core anisotropy 1 laterally homogeneous anisotropy 1 we use mantle and inner core sensitive normal modes to invert for laterally varying mantle models and a transversely isotropic inner core to obtain an inner core model that is compatible with long period mode and short period body wave data we incorporate mantle corrected absolute travel time and differential travel time data in our inversions using this diverse data set we investigate the dependence of inner core models upon mantle parameterization and possible radial structure within the inner core inner core anisotropy obtained from a simultaneous inversion for mantle and inner core structure has a weak dependence upon the parameterization within the mantle that is the results for the inner core are insensitive to whether the mantle is inverted only for shear velocity structure or for shear and compressional velocity structure as well as density an inner core model with constant anisotropy is capable of fitting all types of data but mode and absolute travel time data are more compatible with one another than with differential travel time data allowing for radial variations within the inner core reduces this incompatibility and it is possible to obtain a radially dependent model that fits normal mode absolute travel time and differential travel time data with a variance reduction greater than 75

indoor seismology by probing the earth s interior by using sound velocity measurements at high pressures and temperatures the adiabatic bulk ks and shear g moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics we present the application of the current state of the art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high pressure phases by using these updated thermoelasticity data for these phases velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models we conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410 and 660 km depths the gradient in the transition zone as well as the velocities in the lower mantle if the uncertainties in the modeling and the variations in different seismic models are considered the characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities as well as the large positive density anomalies observed in the lower mantle cannot be explained fully without invoking chemical variations

a new catalogue of normal mode splitting function measurements up to 10 mhz the splitting of the earth s free oscillation spectra places important constraints on the wave speed and density structure of the earth s mantle and core we present a new set of 164 self coupled and 32 cross coupled splitting functions they are derived from modal spectra up to 10 mhz for 91 events with mw 7 4 from the last 34 yr 1976 2010 our data include the 2001 june 23 peru event mw 8 4 the sumatra events of 2004 mw 9 0 and 2005 mw 8 6 the 2008 wenchuan china event mw 7 9 and the 2010 chile event mw 8 8 the new events provide significant improvement of data coverage particularly in continental areas almost half of the splitting functions have never been measured before in particular we measured 33 new modes sensitive to mantle compressional wave velocity 10 new inner core sensitive modes and 22 new cross coupled splitting functions these provide new constraints on the large scale compressional structure of the mantle and the odd degree structure of the mantle and inner core and can be used in future inversions of heterogeneous earth structure our new splitting function coefficient data set will be available online

influence of thermochemical piles on topography at earth s core mantle boundary abstract numerous seismic studies reveal the presence of two large low velocity anomalies beneath africa and the central pacific efforts to characterize these anomalies have yielded a variety of interpretations over the years both isochemical and thermochemical previous interpretations have included large isochemical superplumes clusters of smaller thermal plumes and doming thermochemical superplumes a conceptual mantle model that is presently growing favor involves long lived thermochemical piles in anticipation that nutation studies will provide better topographic constraints on the core mantle boundary cmb in the future we examine the effects of thermochemical piles at this boundary in this study we perform numerical modeling of thermochemical and isochemical convection as a function of convective vigor and temperature dependent viscosity to predict the topography at earth s cmb our results show that in isochemical convection downwellings always lead to negative depressed cmb topography while upwellings cause positive elevated topography consistent with previous studies however in thermochemical convection cmb topography and its relationship to downwellings and thermochemical piles are significantly affected by temperature dependent viscosity for isoviscous or weakly temperature dependent viscosity the piles cause negative cmb topography while positive topography is often below cold downwellings however for realistic more strongly temperature dependent viscosity the most negative cmb topography is below downwellings while the topography below the piles is often slightly more positive and or flat similar to upwellings in isochemical models we also show that although thermochemical piles are intrinsically more dense the large thermal buoyancy associated with them leads to overall relative buoyancy that is on par with slabs consequently thermochemical models lead to an overall reduction in magnitude of cmb topography with respect to isochemical models

in situ monitoring and 3d geomechanical numerical modelling to evaluate seismic and aseismic rock deformation in response to deep mining abstract in this work we investigated seismic and aseismic rock mass behaviors in response to deep underground mining for this purpose an area under production of the metal mine of garpenberg sweden was instrumented with a geophysical and geotechnical monitoring network in situ monitoring data were analyzed and interpreted considering mining operations and the local geological setting in addition a 3d elasto plastic numerical model was built to better understand the interactions between quasi static stress changes due to mining and the generation of the induced seismicity results of this multiparameter approach show a complex rock mass response we observed two main types of seismic behaviors one local and temporally short directly induced by production the other long lasting over time and remote from excavations being mainly controlled by geological heterogeneities in addition to seismicity we also observed creep like phenomena induced by mining in turn these time dependent strains appear to be a third mechanism driving seismicity all these findings underline the importance of considering both seismic and aseismic deformations when one wants to characterize the rock mass response to mining this significantly enhances our understanding of the phenomena involved as well as their interactions for an improved hazard assessment in deep mining operations

reliable mantle density error bars an application of the neighbourhood algorithm to normal mode and surface wave data summary we demonstrate the feasibility and reliability of a new approach to seismic modelling of long wavelength mantle structure in doing so we present new estimates of mantle model uncertainties that successfully explain apparent discrepancies in earlier 3d seismic density models and justify a new generation of model building the characteristics of good models and of modelling error are described by model space maps that display the data fit of a representative set of potential models the neighbourhood algorithm na recently developed by malcolm sambridge allows efficient production of such maps for the long wavelength model parametrizations used in imaging the mantle density using normal mode data we observe that when na is applied to our global modelling problem the results are not only self consistent and consistent with independent resolution tests but also explain discrepancies in the results of damped inversions synthetic mapping experiments using the sensitivity kernels and measurement errors of several data catalogues allow us to determine the resolution of these data sets such resolution tests let us know which model parametrizations and data sets if any can yield meaningful results in inversions of real data the new resolution tests reveal that recent density models from damped inversions of normal mode data are not robust however we also show that the addition of the most recent long wavelength data will for the first time reduce model covariances enough to achieve robust constraints on the depth and size of long wavelength density heterogeneity throughout the mantle

calculation of normal mode spectra in laterally heterogeneous earth models using an iterative direct solution method summary normal mode observations play an important role in studying broad scale lateral variations in the earth such studies require the calculation of accurate synthetic spectra in realistic earth models and this remains a computationally challenging problem here we describe a new implementation of the direct solution method for calculating normal mode spectra in laterally heterogeneous earth models in this iterative direct solution method the modecoupling equations are solved in the frequency domain using the preconditioned biconjugate gradientalgorithm andthetime domainsolutionisrecoveredusinganumericalinversefourier transform a number of example calculations are presented to demonstrate the accuracy and efficiency of the method for performing large full coupling calculations as compared to methods based on matrix diagonalization and the traditional direct solution method

elasticity of single crystal periclase at high pressure and temperature the effect of iron on the elasticity and seismic parameters of ferropericlase in the lower mantle

deep mantle seismic modeling and imaging detailed seismic modeling and imaging of earth s deep interior is providing key information about lower mantle structures and processes including heat flow across the core mantle boundary the configuration of mantle upwellings and downwellings phase equilibria and transport properties of deep mantle materials and mechanisms of core mantle coupling multichannel seismic wave analysis methods that provide the highest resolution deep mantle structural information include network waveform modeling and stacking array processing and 3d migrations of p and s wave seismograms these methods detect and identify weak signals from structures that cannot be resolved by global seismic tomography some methods are adapted from oil exploration seismology but all are constrained by the source and receiver distributions long travel paths and strong attenuation experienced by seismic waves that penetrate to the deep mantle large and small scale structures with velocity variations ranging from a fraction of a percent to tens of percent have been detected and are guiding geophysicists to new perspectives of thermochemical mantle convection and evolution

poisson s ratio in the lower mantle beneath alaska evidence for compositional heterogeneity 1 using waveform cross correlation we have measured 17 000 p and s wave differential travel times from earthquakes and receivers near a great circle path from japan across alaska to north america we jointly invert the data for variations in shear and bulk sound speed and derived poisson s ratio variations in the mantle beneath 1000 km depth we explore the model space using different levels of regularization and our conclusions are based on a range of models that give acceptable data fits the correlation between vs and vp variations is good to 1500 km depth but gradually degrades in the bottom 1000 km whereas the ratio r lnvs lnvp is between 1 0 and 1 8 at most depths our data suggest that there is no significant correlation between bulk and shear wave speed but they appear anticorrelated in several regions we estimate the effect on the poisson s ratio of changes in temperature iron content and the magnesiowustite mw to perovskite pv ratio at all depths the effect of temperature is largest and that of the pv to mw ratio smallest our data cannot resolve the trade off between thermal and compositional effects but explaining the poisson s ratio variability by temperature alone would require unrealistic perturbations and it would not explain the inferred anticorrelation between shear and bulk sound speed our results suggest that despite r being significantly smaller than 2 5 we need a combination of thermal and compositional effects in order to explain the elastic parameter variations in the deep mantle beneath alaska with realistic values of t of 300 800 k variation in xfe of 4 and pv enrichment or depletion of up to 10 just sufficient for explaining the data

normal mode and free air gravity constraints on lateral variations in velocity and density of earth s mantle with the use of a large collection of free oscillation data and additional constraints imposed by the free air gravity anomaly lateral variations in shear velocity compressional velocity and density within the mantle dynamic topography on the free surface and topography on the 660 km discontinuity and the core mantle boundary were determined the velocity models are consistent with existing models based on travel time and waveform inversions in the lowermost mantle near the core mantle boundary denser than average material is found beneath regions of upwellings centered on the pacific ocean and africa that are characterized by slow shear velocities these anomalies suggest the existence of compositional heterogeneity near the core mantle boundary

properties of thermally metamorphosed coal from tanjung enim area south sumatra basin indonesia with special reference to the coalification path of macerals abstract thermally metamorphosed tertiary age coals from tanjung enim in south sumatra basin have been investigated by means of petrographic mineralogical and chemical analyses these coals were influenced by heat from an andesitic igneous intrusion the original coal outside the metamorphosed zone is characterized by high moisture content 4 13 11 25 wt and volatile matter content 40 wt daf as well as less than 80 wt daf carbon and low vitrinite reflectance vr max 0 52 0 76 those coals are of subbituminous and high volatile bituminous rank in contrast the thermally metamorphosed coals are of medium volatile bituminous to meta anthracite rank and characterized by low moisture content only 80 wt daf and vitrinite reflectance vr max 1 87 6 20 all the studied coals have a low mineral matter content except for those which are highly metamorphosed due to the formation of new minerals the coalification path of each maceral shows that vitrinite liptinite and inertinite reflectance converge in a transition zone at vr max of around 1 5 significant decrease of volatile matter occurs in the zone between 0 5 and 2 0 vr max a sharp bend occurs at vr max between 2 0 and 2 5 above 2 5 the volatile matter decreases only very slightly between vr r 0 5 and 2 0 the carbon content of the coals is ascending drastically above 2 5 vr r the carbon content becomes relatively stable around 95 wt daf vitrinite is the most abundant maceral in low rank coal 69 6 86 2 vol liptinite and inertinite are minor constituents in the high rank coal the thermally altered vitrinite composes 82 4 93 8 vol mosaic structures can be recognized as groundmasss and crack fillings the most common minerals found are carbonates pyrite or marcasite and clay minerals the latter consist of kaolinite in low rank coal and illite and rectorite in high rank coal change of functional groups with rank increase is reflected most of all by the increase of the ratio of aromatic c h to aliphatic c h absorbances based on ftir analysis the oxygen index values of all studied coals are low oi 2 g toc and the high rank coals have a lower hydrogen index t max increases with maturity 420 440 c for low rank coals and 475 551 c for high rank coals based on the above data it was calculated that the temperature of contact metamorphism reached 700 750 c in the most metamorphosed coal

simultaneous inversion for 3 d variations in shear and bulk velocity in the mantle until recently most of the seismic tomographic modeling has been addressing the question of lateral heterogeneity either in p or s wave velocities the s wave velocity variations are larger and hence provide stronger signal on long period waveforms the direct p travel times being the first arrivals on the other hand are most frequently reported in the international seismological centre isc bulletins in mineral physics experiments the variation in bulk velocity is more often measured to better understand the differences between vp and vp patterns and better link the results from mineral physics to those of seismic tomography we formulate the inverse problem in terms of relative perturbations in the shear velocity vs 12 and bulk sound velocity v k 12 we use a large data set which consists of waveforms waveform derived travel times and travel times from the isc bulletins the earthquakes are relocated using corrections for lateral heterogeneity the events which cannot be reliably determined are discarded the model is defined as spherical harmonics to degree 12 horizontally and as chebyshev polynomials to order 13 radially for both shear and bulk sound velocity the inversion is performed under smoothness constraint the resolution tests and bootstrapping analysis indicate that the model is well recovered particularly at long wavelength the results indicate a much larger variability of shear than bulk sound velocity the model explains observations well the most intriguing result obtained in this study is that the variations in shear velocity and bulk sound velocity are negatively correlated in the lowermost mantle the explanation is not very clear from the mineral physics point of view it is not unlikely that this could be explained in terms of thermal variation even though we are unwilling to rule out the possibility of large wavelength compositional variations

organic matter maturation under the influence of a deep intrusive heat source a natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock toarcian shale northern germany four shallow boreholes were drilled in the hils syncline northern germany in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen type ii bearing source rock the holes penetrated the carbonceous lias shales posidonia shale lower toarcian and part of the adjacent dogger and lias mudstones the maturity of the organic matter in the cores recovered ranges from immature 0 48 r0 to overmature 1 45 r0 due to location of the hils syncline in the vicinity of the vlotho massif which is deep seated intrusive body facies variations of the lias within the short geographical distances in the study area are negligible organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the lias shales kerogen bitumen etc and on the evidence of a uniform initial composition of these sediments in the study area dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations about 50 of the initial kerogen was transformed into oil gas and inorganic compounds during the vitrinite reflectance increase from 0 48 to 0 88 ro and only marginally more during the maturity increase from 0 88 to 1 45 ro only a small portion of the generated material remained in the source rock even at a relatively early stage of generation 0 68 ro expulsion efficiency of oil plus gas reached a value of 86 at the end of the main generation stage 0 88 ro

malargue group maastrichtian danian deposits in the neuquen andes argentina implications for the onset of the first atlantic transgression related to western gondwana break up abstract the discovery of marine to brackish and fresh water carbonates in the inner agrio fold and thrust belt at pichaihue neuquen argentina located to the west of the andean orogenic front imposes important constraints on the paleogeography of the first atlantic transgression in the neuquen basin related to the break up of western gondwana the constraints on the timing and areal extent of these deposits shed light on the early uplift history of the southern andes these limestones are part of the maastrichtian danian malargue group which was previously only known from its exposures in the extra andean area representing foreland basin deposits the presence of stromatolites oncoids serpulids bivalves and gastropods as well as silicified stems of macrophytes indicates a shallow marine partially brackish environment associated with non marine deposits these strata are interfingered with and overlie distal tuffs and proximal pyroclastic flows whose geochemical characteristics point to a magmatic arc source shrimp u pb dating of volcanic zircons of these tuffs yielded an age of 64 3 0 9 ma that confirms the correlation to the maastrichtian paleocene marine transgression from the atlantic ocean the change in the paleoslope of the basin from pacific ocean transgressions to this atlantic transgression is related to the uplift and deformation of the agrio fold and thrust belt the pichaihue limestone is unconformably deposited on volcanic agglomerates which in turn unconformably overlie early cretaceous deposits based on these data it is confirmed that the cretaceous uplift of the andes was episodic at these latitudes with a first pulse in the cenomanian and a second one in pre maastrichtian times the episodic uplift is also related to an eastward migration of the thrust front and the volcanic arc related to a previously proposed shallowing of the subduction zone these episodes were controlled by the western gondwana break up and the beginning of absolute motion of south america toward the west

quantification of loss of calcite pyrite and organic matter due to weathering of toarcian black shales and effects on kerogen and bitumen characteristics abstract comparison of geochemical data on posidonia shale early toarcian from a shallow unweathered core and from adjacent weathered exposures of the same fades was performed results revealed that quantitatively the most affected petrographic constituent is pyrite and that organic matter and carbonate were also altered by weathering due to this process of weathering the bulk composition of organic matter especially the molecular composition of soluble organic matter and the fluorescence colour of organic particles are changed estimates of weathering rates reveal that the annual release of sulphur and organic carbon from black shales may significantly add to anthropogenic pollution

aptian to recent compressional deformation foothills of the neuquen basin argentina abstract the neuquen basin lies in north western patagonia on the eastern foreland of the andes it formed as a rift basin in the early mesozoic and contains some 5000 m of triassic to aptian sediment mainly marine as a result of andean orogeny the western edge of the basin now forms part of the foothills we describe some of the main compressional structures drawing on surface and sub surface data we argue that regional eastward dips are due to west verging thrust displacements on the andacollo loncopue fault system during a late cretaceous peruvian phase aptian to campanian continental sediment accumulated in a retro arc foreland basin which was mainly of flexural origin nevertheless more than 1500 m of late cretaceous sediment accumulated in the footwall of the east verging agua amarga thrust the peruvian phase was responsible also for transpressional reactivation of a rift transfer zone the huincul arch the incaic phase eocene was responsible for north westerly trending folds and thrusts reactivation of cretaceous thrusts abundant andesitic lavas and high level intrusions and a swarm of north easterly trending bitumen dykes the quechua phase miocene to recent produced northerly trending folds and thrusts and a miocene foreland basin containing some 1000 m of basalt lava flows structures that formed during the incaic and quechua phases are broadly compatible with the history of convergence at the pacific margin of south america as deduced from plate reconstructions

global mantle tomography progress status in the past 10 years abstract we review the present status of global mantle tomography and discuss two main classes of models that have been developed in the past 10 years p velocity models based on large datasets of travel times from the international seismological centre bulletins often referred to as high resolution models and s velocity models based on a combination of surface wave and hand picked body wave travel times or waveforms referred to as long wavelength models we discuss their respective strengths and weaknesses as well as progress in the resolution of other physical parameters such as anisotropy anelasticity density and bulk sound velocity using tomographic approaches we present the view that future improvements in global seismic tomography require the utilization of the rich information contained in complete broadband seismic waveforms this is presently within our reach owing to theoretical progress as well as the increase in computational power in recent years

postperovskite phase transition and its geophysical implications 1 the stability of mg fe sio3 perovskite in the deep lower mantle has long been uncertain recently a phase transition from perovskite to postperovskite was discovered through a significant change in the x ray diffraction pattern at high pressure and high temperature conditions corresponding to the core mantle boundary region this phase transition was also confirmed by first principles calculations these suggest that mg fe sio3 postperovskite is the predominant mineral in the lowermost mantle called the d layer and phase transition from perovskite to postperovskite has significant geophysical implications for its nature and dynamics the postperovskite phase may account for the large seismic anomalies observed in the d region such as the d discontinuity s wave anisotropy and anticorrelation between the anomalies in s wave and bulk sound velocities in addition this phase transition is a strongly exothermic reaction it destabilizes the thermal boundary layer at the base of the mantle and should promote the formation of high temperature upwelling plumes

compressible thermochemical convection and application to lower mantle structures a new finite element code for compressible thermochemical convection is developed to study the stability of a chemical layer at the base of the mantle using composition dependent compressibility and a density difference between compositions at a reference pressure a composition dependent density profile is derived together with depth dependent thermal expansion this combination of parameters yields a wide range of dynamic evolutions for the chemical layer the chemical structures are classified into five major categories classical plumes mushroom shaped plume domes ridges and continuous layers and a few abnormal cases such as hourglass shaped plumes and columnar plumes several models have a chemical structure morphologically similar to the african low v s structure in the lower mantle at least at a single time guided by our models several dynamic scenarios are proposed for the dynamic nature of the lower mantle low velocity structures a k a superplumes including plumes at an early stage plume clusters ridges passive piles sluggish domes and high bulk modulus domes we predict seismic velocity anomalies from these dynamic models the thermoelastic parameters used in the conversion are additional constraints we compare the density structure with normal mode inversion the predicted seismic signature observations and the required thermoelastic parameters with mineral physics data among the proposed scenarios only the scenario of high bulk modulus domes satisfies all constraints simultaneously the implication on the geochemistry and mineralogy of lower mantle chemical structures is discussed

short scale heterogeneity in the lowermost mantle insights from pcp p and scs s data we compare lateral variations at the base of the mantle as inferred from a global dataset of pcp p travel time residuals measured on broadband records and existing p and s tomographic velocity models as well as scs s travel time data in some selected regions in many regions the pcp p dataset implies short scale lateral variations that are not resolved by global tomographic models except under eastern eurasia where data and models describe a broad region of fast velocity anomalies across which variations appear to be of thermal origin in other regions such as central america and southeastern africa correlated short scale lateral variations several hundred kilometers are observed in pcp and scs implying large but not excessive values for the ratio r d ln vs d ln vp v2 5 on the other hand in at least two instances in the heart of the african plume and on the edge of the pacific plume variations in p and s velocities appear to be incompatible implying strong lateral gradients across compositionally different domains possibly also involving topography on the core mantle boundary one should be cautious in estimating r at the base of the mantle from global datasets as different smoothing and sampling of p and s datasets may result in strong biases and meaningless results 7 2002 elsevier science b v all rights reserved

late cretaceous late turonian coniacian and santonian petroleum source rocks as part of an oae tarfaya basin morocco abstract late turonian coniacian and santonian source rock samples from a recently drilled well tafaya sondage no 2 2010 in the tarfaya basin were analyzed for quantity quality maturity and depositional environment of the organic matter om to our knowledge such a thick sequence of organic matter rich turonian to santonian source rocks was investigated in that great detail for the first time organic geochemical and organic petrological investigations were carried out on a large sample set from the 200 m thick sequence in total 195 core samples were analyzed for total organic carbon corg total inorganic carbon contents and total sulfur ts contents rock eval pyrolysis and vitrinite reflectance measurements were performed on 28 samples chosen on the basis of their corg content non aromatic hydrocarbons were analyzed on selected samples by way of gas chromatography flame ionization detection gc fid and gc mass spectrometry gc ms the organic matter rich carbonates revealed a high source rock potential representing type i kerogen and a good preservation of the organic matter which is mainly of marine phytoplankton origin hi values are high 400 900 mg g corg and in a similar range as those described for more recent upwelling sediments along the continental slope of north africa ts corg ratios as well as pristane over phytane ratios indicate variable oxygen content during sediment deposition all samples are clearly immature with respect to petroleum generation which is supported by maturity parameters such as vitrinite reflectance 0 3 0 4 tmax values 401 423 c production indices s1 s1 s2 0 1 as well as maturity parameters based on ratios of specific steranes and hopanes

prospecting for water in the transition zone d ln vs d ln vp abstract we report the values of r d ln vs d ln vp due to water as a function of pressure for mg 2 sio 4 olivine wadsleyite ringwoodite the results show that ringwoodite has significantly lower r than olivine and wadsleyite due to the reason that bulk modulus of ringwoodite is more sensitive to water than shear modulus r of ringwoodite decreases with pressure while r of olivine and wadsleyite increases with pressure r reported here was calculated using theoretical method derived equation of states r due to temperature is also reported as a comparison of r due to water the local value of r in the upper mantle and transition zone can discriminate between lateral variations of water content and temperature as the origin of lateral seismic variations

on the resolution of density anomalies in the earth s mantle using spectral fitting of normal mode data summary the resolution of the 3 d density structure in the earth s deep interior has long eluded geoscientists high quality data from digital seismic instruments emplaced this decade have renewed interest in the measurement of low frequency earth normal modes with the goal of extracting heterogeneous density structure here we perform a series of synthetic experiments aimed at investigating the resolution of lateral variations in the mantle from normal mode spectral data contamination effects between seismic velocities and density are examined in two ways 1 by using resolution matrices computed from data kernels and 2 by inverting synthetic spectra computed from realistic input earth models the first type of experiment assumes that the non linearity of the inverse problem is weak no such assumptions are necessary in the second type of tests which nevertheless concur in their results with the former these synthetic tests indicate that density structure retrieved from presently available normal mode data is not reliable contamination of seismic velocity structure into the density model space produces patterns that resemble those obtained from inversions of real data the resulting density models appear to be dependent on a combination of the starting velocity models and the model parametrization

tectonic control on hydrocarbon generation in the northwestern neuquen basin argentina the petroleum systems of the malargue fold thrust belt in the northwestern neuquen basin argentina comprise multiple reservoir and seal rocks and three major source rocks of the lower jurassic los molles formation fm the lower tithonian to lower valanginian vaca muerta fm and the lower hauterivian to lower barremian agrio fm the thermal history of the mesozoic source rocks has been reconstructed using one dimensional and two dimensional modeling the most important factors that affected the source rock maturation are the timing of maximum late cretaceous to paleogene burial and the heat flow during back arc extension we postulate that synclines have been buried over longer periods and source rock maturation ceased earlier in anticlines accordingly hydrocarbon generation from the vaca muerta fm and agrio fm has started during the campanian despite late stage magmatic activity causing local thermal perturbations the models suggest that the thermal field has been dominated by conductive heat transport and that heat flow has been a response to the evolution from back arc extension to orogenic shortening high heat flows of 85 mw m2 during back arc extension between the latest cretaceous and paleogene have been modeled two main source pods supply hydrocarbons until the present they are related to structurally deep footwall positions of thrust faults active since the late cretaceous and to deep frontal synclines having formed through late stage thick skinned tectonics since the neogene modeling of hydrocarbon fluid type is consistent with existing oil fields exhibiting light and medium oils with api between 22 api and 39 api charged from early to peak mature source rocks

bullen s parameter η a link between seismology and geodynamical modelling valuable information concerning the style of mantle density stratification can be gleaned from the spatial distribution of bullen s parameter by means of numerical modelling of 2 d cartesian convection and by monitoring this with the 2 d field of the local bullen s parameter values which were obtained by post processing the convection results we show that the local adiabaticity is seriously influenced by the presence of an endothermic phase transition at 670 km depth in this situation the upper mantle suffers much more from non adiabatic effects than the lower mantle we have also employed the 3 d distributions of density and seismic velocities from the model of ishii and tromp based on free oscillation observations and constructed 3 d local bullen s parameter for a spherical earth in the lower mantle we find that there is a striking similarity in the range of magnitudes of the local bullen s parameter calculated from convection and those inferred from the splitting of seismic free oscillations the morphologies of subadiabatic regions in the deep mantle under africa and the central pacific would suggest a thermal chemical nature of the superplumes their vertical extent is limited to around 400 km above the core mantle boundary cmb underneath the icelandic area in the north atlantic such an subadiabatic region in the deep mantle above the cmb cannot be discerned we conclude that the mantle is not as adiabatic as has commonly been held fl 2002 elsevier science b v all rights reserved

using probabilistic seismic tomography to test mantle velocity density relationships we use a neighborhood algorithm to explore the fit to long period seismic data of a wide variety of long wavelength mantle models this approach to the global tomographic inverse problem yields probability distributions for seismic velocities density and related properties as functions of depth such distributions can be robust even when individual models are not and allow us to test several assumptions about the earth that have long been enforced a priori in inversions in particular we are able to test the paradigm ofdeep mantle heterogeneity that is dominantly thermal in origin producing velocity and density perturbations that are well correlated and have relative amplitudes given by nlnb nlnvs 6 0 5 our distributions show that such relationships are unlikely and even though the results are consistent with recent best fitting models from damped seismic inversions they demonstrate that many specific properties ofsuch models are not robust the data clearly f density perturbations that are poorly or negatively correlated with velocity heterogeneity and have amplitudes several times larger yielding nlnb nlnvs s 1 0 than damped inversions allow these characteristics are most pronounced in the upper mantle transition zone and the base ofthe lower mantle suggesting layered convection the negative density velocity correlations f at these depths imply dominantly chemical heterogeneity while the likelihood ofrelatively high amplitude density variations suggests that variable iron content is an important component ofthis heterogeneity these results which we show to be consistent with independent gravity constraints represent a profound change in the interpretation of seismic constraints in addition the distributions show that even though best fitting density models from recent inversions or our sampling are consistent with the data most specific properties of such models are not robust this implies that it is more appropriate to use seismic model distributions rather than individual models to make geodynamic and geochemical inferences

microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in toarcian source rocks of different maturities abstract this study is part of a comprehensive research program on the generation and migration of petroleum from the organic rich posidonia shale lower toarcian jurassic of the hils syncline northern germany four cores of the complete posidonia shale with varying amounts of underlying pliensbachian and overlying aalenian mudstones provided the sample base depending upon their distance from a presumed subjacent heat source the vlotho massif the cores display progressive levels of increasing thermal maturation with r 0 values 0 48 0 68 0 88 and 1 45 which span the limits of the oil generation window primary stratigraphic lithologic and petrographic attributes of the four sections are all very similar each includes a lower marlstone member about 5 m thick overlain by 11 31 m of calcareous clay shale clay minerals calcite pyrite kerogen and quartz are the principal constituents thus there is no evidence that depositional conditions of the posidonia shale varied significantly over the sampled area the omnipresence of framboidal pyrite clearly formed from the activity of sulphate reducing bacteria at or near the depositional interface is strong evidence that uniform reducing anoxic conditions were persistent at all localities this conclusion supports the assumption that initially each section was identical in overall properties and that significant differences observed in geochemistry organic macerals and other properties are directly related to the variable levels of thermal maturation kerogen from the least mature section r o 0 48 is type ii and composed of alginite a alginite b liptodetrinite bituminite and some terrestrial sporinite vitrinite and inertinite macerals with increasing maturation the alginite macerals exhibit a progressive change in morphology and fluorescence properties alginite of the least mature section displays a strong green fluorescence at 0 68 r o alginite macerals exhibit yellow orange fluorescence and are structurally well preserved although geochemical data indicate generation and loss of large amounts of oil at 0 88 r o hydrocarbon generation is almost complete and few primary alginites remain they have been transformed into secondary liptinites designated as metaalginite which have similar fluorescence colours at the highest maturation level 1 45 r o metaalginites are only weakly fluorescent with a shift toward red colours calcite and or bitumen filled bedding plane micro and macrofractures occur exclusively in the organic rich posidonia shale at maturity levels of 0 68 r o and above such features are totally absent in the immature posidonia section and in the adjacent organic poor mudstones this observation indicates that the fractures developed in direct response to overpressuring i e pore pressure exceeding lithologic load related to oil and gas generation in the source rock the fractures undoubtedly provided important expulsion conduits for generated products

can we resolve 3d density heterogeneity in the lower mantle we reexamine the possibility of resolving 3d density structure in the mantle by performing test inversions using a dataset of well constrained degree 2 splitting coefficients we show that degree 2 in vs and vp can be resolved and confirm that dlnvs dlnvp 2 5 at depths 2000km indicating a chemical component to large scale heterogeneity models with positively correlated with vs in the deepest mantle fit the data at least as well as those in which density and velocities are anti correlated however some rough bounds on dln dlnvs can be inferred models obtained from geodynamic considerations are acceptable in contrast to models with large negative 0 6 dln dlnvs throughout the lower mantle the most robust feature is a marked increase in dln dlnvs at the top of the lower mantle reaching a maximum around 1500 km

splitting function measurements for earth s longest period normal modes using recent large earthquakes recent megathrust earthquakes such as the 23 june 2001 peru event the sumatra events of 2004 and 2005 and the 27 february 2010 chile event have given us the opportunity to measure splitting of the longest period normal modes we use wave spectra to make robust measurements for modes 0s2 0s3 0s4 2s1 and 1s2 singlet frequencies of these modes have been measured previously using gravimeters but here we use seismic records to observe splitting functions for 0s2 and 2s1 for the first time cross coupling with nearby modes is included to account for ellipticity and rotation of the earth and results in significantly improved splitting function measurements for 0s3 0s4 and 1s2 compared with previous studies the new splitting function measurements can easily be implemented in future tomographic modelling of aspherical velocity and particularly density structure

toroidal splitting observations from the great 1994 bolivia and kuril islands earthquakes the june 9 1994 bolivia earthquake and the october 4 1994 kuril islands earthquake provide a unique opportunity for a splitting analysis of the earth s long period toroidal free oscillations we present toroidal splitting observations for the 6 fundamental modes 0t4 0t5 0t6 0t7 0t8 and 0t9 and for the 5 first overtones 1t1 1t2 1t3 1t4 and 1t6 the first identification of mode 1t1 is made possible by simultaneously fitting the multiplets 1t1 and 0t7 the observed splitting is reasonably well explained by current shear velocity models of the mantle our analysis yields new estimates of the center frequencies and quality factors of these 11 toroidal modes

mgsio3 postperovskite at d conditions the postperovskite transition in mgsio3 at conditions similar to those expected at the d discontinuity of earth s lower mantle offers a paradigm for interpreting the properties of this region despite consistent experimental and theoretical predictions of this phase transformation the complexity of the d region raises questions about its geophysical significance here we report the thermoelastic properties of cmcm postperovskite at appropriate conditions and evidences of its presence in the lowermost mantle these are i the jumps in shear and longitudinal velocities similar to those observed in certain places of the d discontinuity and ii the anticorrelation between shear and bulk velocity anomalies as detected within the d region in addition the increase in shear modulus across the phase transition provides a possible explanation for the reported discrepancy between the calculated shear modulus of postperovskite free aggregates and the seismological counterpart in the lowermost mantle

trans pacific upper mantle shear velocity structure 1 we use 50 tonga fiji events recorded at the broadband trinet array southern california to develop a pure path upper mantle shear velocity model across the pacific at the epicentral distances of 70 95 multibounce s waves up to s5 are observed including their triplicated branches which become particularly clear after stacking since these s wave multiples turn at various depths simultaneously modeling their differential traveltimes and waveforms provides strong constraints on the radial velocity structure we parameterize the velocity model according to a priori information from the previous oceanic models so that we can take a grid search approach to fully investigate possible interdependencies among the model parameters we construct synthetics with a reflectivity code and study both the sh and sv components by modeling the whole recordings from events at different depths with different mechanisms we are able to separate shallow low velocity zone lvz features from deeper structure our preferred model pac06 contains a fast lid vsh 4 78 km s 1 vsv 4 58 km s 1 with a thickness of 60 km the underlying lvz is prominent with the lowest velocities vsh 4 34 km s 1 and vsv 4 22 km s 1 occurring at a depth of 160 km these velocities are below the estimates of solid state lvz suggesting the presence of partial melt the anisotropy vsv vsh of pac06 extends to 300 km depth which is constrained by s5 turning at this depth besides the 406 km and 651 km discontinuities pac06 also has a small 1 velocity jump at 516 km we consider these main features of pac06 to be well determined since pac06 explains a large data set from various events therefore it is ideally suited for comparing with mineralogical models

inferring radial models of mantle viscosity from gravity grace data and an evolutionary algorithm convective flow in the mantle can be thought of and modeled as exclusively driven by density heterogeneities in the mantle itself and the resulting lateral variations in the earth s gravity field with this assumption and a model of mantle rheology a theoretical relationship can be found between 3d mantle structure and flow related quantities that can be measured on the earth s surface like free air gravity anomalies this relationship can be used to set up an inverse problem with 1d mantle viscosity as a solution in the assumption that seismic velocity anomalies be of purely thermal origin and related to density anomalies by a simple scaling factor we invert the large scale length component of the above mentioned measurements jointly with seismic observations waveforms and or travel times to derive an accurate 5 layer spherically symmetric model of upper and lower mantle viscosity we attempt to account for non uniqueness in the inverse problem by exploring the solution space formed of all possible radial profiles of earth viscosity by means of a non deterministic global optimization method the evolutionary algorithm ea for each sampled point of the solution space a forward calculation is conducted to determine a map of gravity anomalies whose similarity to grace gravity recovery and climate experiment is then measured the procedure is iterated to convergence according to ea criteria the robustness of the inversion is tested by means of synthetic tests indicating that our gravity data set is able to constrain less than 6 radial layers each with uniform viscosity independently of the tomographic model or the scaling factor adopted to convert seismic velocity into density structure the ea optimization method finds viscosity profiles characterized by low viscosity in a depth range corresponding to the transition zone and relatively uniform elsewhere

partial melting in a thermo chemical boundary layer at the base of the mantle abstract seismological detections of complex structures in the lowermost mantle boundary layer the d region motivate a conceptual model of a compositionally stratified thermo chemical boundary layer tcbl within which lateral temperature variations sustained by large scale mid mantle flow cause variations of partial melt fraction partial melt fractions of from 0 to 30 in the tcbl occur due to the eutectic of the boundary layer material lying below the high temperature at the core mantle boundary cmb coupled with the presence of steep thermal gradients across the boundary layer regions of the tcbl with the highest temperatures have extensive partial melting producing lateral chemical variations and strong effects on seismic velocities and boundary layer dynamics this tcbl concept provides a relatively simple framework that can plausibly account for diverse seismological observations such as predominance of large scale volumetric elastic wave velocity heterogeneity in the boundary layer laterally extensive but intermittent abrupt shear and compressional velocity increases and decreases at the top of the d region small scale topography of d velocity discontinuities thin ultra low velocity zones at the cmb widespread shear wave anisotropy in d bulk sound velocity anomalies detected in low shear velocity regions of d and large scale upwellings from the most extensively melted regions of the boundary layer neutral or negative buoyancy of the partial melt in the tcbl is required along with an increase in bulk modulus and some density increase of the boundary layer material relative to the overlying mantle more complex models in which the partially melted chemical boundary layer is laterally displaced by mid mantle downwellings are also viable but these appear to require additional special circumstances such as a phase change efficient segregation of slab crustal material or abrupt onset of anisotropy in order to account for rapid velocity increases at the top of d the precise nature of the compositional anomaly or anomalies in d and the eutectic composition of this zone are yet to be determined but it appears likely that partial melting within the lowermost mantle plays a paramount role in the observed seismic velocity heterogeneity increased resolution geodynamic calculations of dense boundary layer structures with partial melting and attendant viscosity reductions and chemical heterogeneity are needed to quantify this tcbl concept

a 6 year westward rotary motion in the earth detection and possible micg coupling mechanism abstract seeking geophysical explanations for the periodic six year oscillation syo previously found in the earth s length of day variation lod we analyze the global gps displacement and geomagnetic data using the array processing technique of ose optimal sequence estimation and find clear evidences of the 6 yr signals which manifest as a westward rotary propagating wave of the sectoral spherical harmonic pattern of degree 2 order 2 y 22 based on the period the spatial pattern and the amplitudes and the estimated phases that exhibit consistent synchronicity among the three datasets we propose the following scenario the mantle inner core gravitational micg coupling gives rise to a 6 yr axial torsional libration of the inner core controlled by the sectoral y 22 density anomalies or the equatorial ellipticities in the inner core and the lower mantle the angular momentum exchange between which manifests as the syo in lod it forces into action a pressure wave 2 cyclic in 6 yr through the fluid outer core which in turn produces the corresponding gps and geomagnetic variations our findings provide insight into the dynamics of the deep earth and corroborate a positive density anomaly for the lower mantle large low shear velocity provinces

on the anelastic contribution to the temperature dependence of lower mantle seismic velocities abstract there is little agreement regarding the importance of anelastic contributions to the temperature dependence of seismic wave velocities some studies consider the anelastic contribution to be negligible whereas others argue that it may be as important as the purely elastic contribution in order to evaluate these claims we review physically plausible models for mantle relaxation processes and construct a model of activation enthalpy based on solid state physics as well as on recent experimental results we then deduce self consistent 1 d q profiles and evaluate the anelastic contribution to the temperature dependence of v s and v p physically plausible values of activation enthalpies yield anelastic contributions that increase with depth and account for at least 20 of the velocity temperature derivatives at 2600 km we show that anelasticity may significantly moderate temperature variations in hot slow velocity zones this suggests that inferred lateral changes in temperature as well as arguments regarding the presence of chemical heterogeneity and or temperature induced phase transformations are likely to be significantly affected by anelastic effects in the mantle we also compute values of the dimensionless parameters r s p r s and r s we find that anelasticity can either increase or decrease r s p but the magnitude of the correction of the order of 15 is smaller than the uncertainty in the elastic value anelasticity cannot change the sign of r s and r s but it can decrease their values by as much as 50 however given current uncertainties in seismic and mineral data the effects of anelasticity on the dimensionless parameters do not bring any quantitative constraints on lateral variations of temperature chemical composition and or mineral phase

global mantle shear velocity model developed using nonlinear asymptotic coupling theory we present a three dimensional shear velocity model of the whole mantle developed using s h waveform data the model is expressed horizontally in terms of spherical harmonics up to degree 12 and vertically in terms of legendre polynomials up to degrees 5 and 7 in the upper and lower mantle respectively what distinguishes this model from other tomographic models published to date is 1 the theoretical normal mode based wave propagation approach where we include across branch mode coupling terms in order to model the body wave sensitivity to structure along the path more accurately 2 the wave packet weighting scheme which allows to balance contributions from high amplitude and low amplitude phases increasing the resolution in some parts of the mantle we also relax the constraints on the moho depth which is allowed to vary in the inversion thus absorbing some uncertainties in crustal structure the resulting model is generally in good agreement with other recent global mantle s velocity models and with some regional models the rms profile with depth has more power than other models in the upper mantle lower mantle transition region and the zone of increased power and low degree structure near the base of the mantle is confined to the last 500 km in depth this model provides a particularly good fit to the non hydrostatic geoid through harmonic degree 12 79 variance reduction as well as good fits to observed splitting functions of s velocity sensitive mantle modes indicating that both large scale and small scale features are really well constrained