prediction of lateral variability in fracture intensity using multicomponent shear wave surface seismic as a precursor to horizontal drilling in the austin chalk summary a method of multicomponent multisource shear wave interpretation utilizing the output of the alford rotation for separating the fast and slow particle motion stacks in azimuthally anisotropic media yielded a qualitative prediction of lateral fracture intensity variation prior to horizontal drilling the method exploits a fundamental difference between the two particle motion stacks when vertical aligned fractures are the source of the shear wave splitting the fast shear wave s1 section is insensitive to the lateral variation in fracture intensity since its particle motion is parallel to the fractures hence reflectivity on the s1 cdp stacked section should be likewise insensitive to fractures the slow shear wave s2 section however possesses particle motion perpendicular to the fracture planes so variation in lateral fracture intensity will affect velocity and reflectivity examination of the reflectivity on the two sections for a seismic line reveals laterally consistent reflector strength on the s1 section for the austin chalk the horizon of interest but laterally inconsistent reflector strength for the same horizon on the s2 section in the study area reflector dimming on the s2 section was interpreted as indicating fracture intensity maxima horizontal drilling confirmed both fracture azimuth and intensity predictions and resulted in significantly higher initial hydrocarbon production than for surrounding wells

pacific ocean and cenozoic evolution of climate 1 the pacific ocean has played a major role in climate evolution throughout the cenozoic 65 0 ma it is a fundamental component of global heat transport and circulation the dominant locus of primary productivity and consequently the largest reservoir for carbon exchange between the oceans and the atmosphere a satisfactory understanding of the cenozoic evolutionary history of the pacific and its impact on global climate is currently data limited nevertheless the large dynamic range of cenozoic conditions sets the stage to greatly expand our understanding of global climate and biogeochemical cycles past earth experiments are particularly useful to understand interactions between climate and geosystems under different greenhouse gas loads we highlight in this review four important problems in which the pacific played a major role the effect of changing geographic boundary conditions on ocean circulation interactions between the carbon cycle and climate the pacific ocean s influence on north american climate and its water cycle and the gradual evolution of climate systems

measurement and characterization of infrasound from a tornado producing storm a hail producing supercell on 11 may 2017 produced a small tornado near perkins oklahoma 35 97 97 04 at 2013 utc two infrasound microphones with a 59 m separation and a regional doppler radar station were located 18 7 and 70 km from the tornado respectively elevated infrasound levels were observed starting 7 min before the verified tornado infrasound data below 5 hz was contaminated with wind noise but in the 5 50 hz band the infrasound was independent of wind speed with a bearing angle that was consistent with the movement of the storm core that produced the tornado during the tornado a 75 db peak formed at 8 3 hz which was 18 db above pre tornado levels this fundamental frequency had overtones 18 29 36 and 44 hz that were linearly related to mode number analysis of a larger period of time associated with two infrasound bursts the tornado occurred during the first event shows that the spectral peaks from the tornado were present from 4 min before to 40 min after tornadogenesis this suggests that the same geophysical process es was active during this entire window

rare earth element concentrations and nd isotopes in the southeast pacific ocean 1 three vertical profiles of rare earth element concentrations and nd isotopic compositions have been measured in the remote southeast pacific ocean the three stations represent contrasting environments the oligotrophic center of the gyre station gyr the transition zone east of the south tropical front station egy and the peru chile upwelling marked by a pronounced oxygen minimum station upx rare earth concentrations display nutrient like vertical profiles except at upx where surface waters are enriched at this station nd isotopic compositions are clearly more radiogenic than in the open ocean suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic andes unexpected radiogenic values end reaching 3 7 are also observed at 2000 m at station gyr in the upper circumpolar deep water that commonly have end values around 6 exchange processes related to hydrothermal activity are suspected to produce this increase in end in the vicinity of the east pacific rise these results provide some guidance for higher resolution studies planned in this region by the international geotraces program

nd and sr isotope compositions of different phases of surface sediments in the south pacific extraction of seawater signatures boundary exchange and detrital dust provenance the radiogenic isotope composition of neodymium nd and strontium sr are useful tools to investigate present and past oceanic circulation or input of terrigenous material we present nd and sr isotope compositions extracted from different sedimentary phases including early diagenetic fe mn coatings unclean foraminiferal shells fossil fish teeth and detritus of marine surface sediments core tops covering the entire midlatitude south pacific comparison of detrital nd isotope compositions to deep water values from the same locations suggests that boundary exchange has little influence on the nd isotope composition of western south pacific seawater concentrations of rare earth elements ree and al ca ratios of unclean planktonic foraminifera suggest that this phase is a reliable recorder of seawater nd isotope composition the signatures obtained from fish teeth and nondecarbonated leachates of bulk sediment fe mn oxyhydroxide coatings also agree with unclean foraminifera direct comparison of nd isotope compositions extracted using these methods with seawater nd isotope compositions is complicated by the low accumulation rates yielding radiocarbon ages of up to 24 kyr thus mixing the signal of different ocean circulation modes this suggests that different past seawater nd isotope compositions have been integrated in authigenic sediments from regions with low sedimentation rates combined detrital nd and sr isotope signatures indicate a dominant role of the westerly winds transporting lithogenic material from south new zealand and southeastern australia to the open south pacific the proportion of this material decreases toward the east where supply from the andes increases and contributions from antarctica cannot be ruled out

infrasound emitted by tornado like vortices basic theory and a numerical comparison to the acoustic radiation of a single cell thunderstorm this paper addresses the physics and numerical simulation of the adiabatic generation of infrasound by tornadoes classical analytical results regarding the production of infrasound by vortex rossby waves and by corotating suction vortices are reviewed conditions are derived for which critical layers damp vortex rossby waves that would otherwise grow and continually produce acoustic radiation these conditions are similar to those that theoretically suppress gravity wave radiation from larger mesoscale cyclones such as hurricanes to gain perspective the regional atmospheric modeling system rams is used to simulate the infrasound that radiates from a single cell thunderstorm in a shear free environment in this simulation the dominant infrasound in the 0 1 10 hz frequency band appears to radiate from the vicinity of the melting level where diabatic processes involving hail are active it is shown that the 3d rossby waves of a tornado like vortex simulated with rams can generate stronger infrasound if the maximum wind speed of the vortex exceeds a modest threshold technical issues regarding the numerical simulation of tornado infrasound are also addressed most importantly it is shown that simulating tornado infrasound likely requires a spatial resolution that is an order of magnitude finer than the current practical limit 10 m grid spacing for modeling thunderstorms

polarimetric radar metrics related to tornado life cycles and intensity in supercell storms abstractpolarimetric radar signatures have been related to the typical evolution of supercell storms including through tornado life cycles now that polarimetric radar observations are available for a large sample of supercell storms time series of new radar metrics can be derived these metrics can be compared with phases of known tornado life cycles in an effort to develop new methods of anticipating tornadoes and to increase understanding of storm scale structural and microphysical changes through supercell and tornado life cycles in this paper radar metrics including measures of differential reflectivity zdr columns zdr arcs polarimetrically inferred hailfall regions and mean value of copolar correlation coefficient hv in the echo appendage are compared to the tornado life cycle and to storm maximum tornado intensity in a sample of 35 tornadic supercells it is shown that these radar metrics may change repeatedly and thus can be used to distinguish tornadic and nontornadic periods in single su

the large scale evolution of neodymium isotopic composition in the global modern and holocene ocean revealed from seawater and archive data neodymium isotopic compositions 143nd 144nd or end have been used as a tracer of water masses and lithogenic inputs to the ocean to further evaluate the faithfulness of this tracer we have updated a global seawater end database and combined it with hydrography parameters temperature salinity nutrients and oxygen concentrations carbon isotopic ratio and radiocarbon of dissolved inorganic carbon archive end data are also compiled for leachates foraminiferal tests deep sea corals and fish teeth debris from the holocene period 10 000 years at water depths 1500 m property property plots show clear correlations between seawater end and the other variables suggesting that large scale water mass mixing is a primary control of deepwater end distribution at 200 m basin scale seawater t s end diagrams demonstrate the isotopic evolution of different water masses seawater and archive end values are compared using property property plots and t s end diagrams archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the pacific both positive and negative offsets exist in the northern north atlantic applying multiple regression analysis to deep 1500 m seawater data we established empirical equations that predict the main large scale deepwater end trends from hydrography parameters large offsets from the predicted values are interpreted as a sign of significant local regional influence dominant continental influence on seawater and archive end is observed mainly within 1000 km from the continents generally seawater and archive end values form gradual latitudinal trend in the atlantic and pacific at depths 600 m consistent with the idea that nd isotopes help distinguish between northern southern sourced water contributions at intermediate and deep water depths

estimation of reservoir fracturing from marine vsp using local shear wave conversion a marine vsp is designed to estimate the orientation and density of fracturing within a gas producing dolomite layer in the southern north sea the overburden anisotropy is firstly estimated by analysing shear waves converted at or just below the sea bed from airgun sources at four fixed offset azimuths full wave modelling helps confirm that the background has no more than 3 vertical birefringence originating from tih anisotropy with a symmetry axis orientated perpendicular to the maximum horizontal compressive stress of nw se this finding concurs with current hypotheses regarding the background rock matrix in the upper crust more detailed anisotropy estimates reveal two thin zones with possible polarization reversals and a stronger anisotropy the seismic anisotropy of the dolomite is then determined from the behaviour of locally converted shear waves providing a direct link with the physical properties of its fractures it is possible to utilize this phenomenon due to the large seismic velocity contrast between the dolomite and the surrounding evaporites two walkaway vsps at different azimuths recorded on three component receivers placed inside the target zone provide the appropriate acquisition design to monitor this behaviour anisotropy in the dolomite generates a transverse component energy which scales in proportion to the degree of anisotropy the relative amplitudes for this component between the different walkaway azimuths relate principally to the orientation ofthe anisotropy full wave modelling confirms that a 50 vertical birefringence from tih anisotropy with a similar orientation to the overburden is required to simulate the field observations this amount of anisotropy is not entirely unexpected for a fine grained brittle dolomite with a potentially high fracture intensity particularly if the fractures contain fluid which renders them compliant to the shear wave motion

seismic tomography in boreholes summary synthetic seismic tomographic data sets for cross hole and hole to surface arrays are computed and inverted inversion imaging is performed through an iterative projection solution to a matrix equation the orientation as well as the position of an anomaly relative to the source and recorder arrays affects both the rate of convergence of the solution and the resolution obtained data density and distribution determine the physical validity of the image obtained at convergence borehole tomography is apparently a viable method for imaging inter hole structure

south pacific dissolved nd isotope compositions and rare earth element distributions water mass mixing versus biogeochemical cycling despite its enormous extent and importance for global climate the south pacific has been poorly investigated in comparison to other regions with respect to chemical oceanography here we present the first detailed analysis of dissolved radiogenic nd isotopes end and rare earth elements rees in intermediate and deep waters of the mid latitude 40 s south pacific along a meridional transect between south america and new zealand the goal of our study is to gain better insight into the distribution and mixing of water masses in the south pacific and to evaluate the validity of nd isotopes as a water mass tracer in this remote region of the ocean the results demonstrate that biogeochemical cycling scavenging processes in the eastern equatorial pacific and release of lrees from the sediment clearly influence the distribution of the dissolved ree concentrations at certain locations nevertheless the nd isotope signatures clearly trace water masses including aaiw antarctic intermediate water average end 8 2 0 3 lcdw lower circumpolar deep water average end 8 3 0 3 npdw north pacific deep water average end 5 9 0 3 and the remnants of nadw north atlantic deep water average end 9 7 0 3 filtered water samples taken from the sediment water interface under the deep western boundary current off new zealand suggest that boundary exchange processes are limited at this location and highlight the spatial and temporal variability of this process these data will serve as a basis for the paleoceanographic application of nd isotopes in the south pacific

nd isotopic structure of the pacific ocean 40 10 ma and evidence for the reorganization of deep north pacific ocean circulation between 36 and 25 ma abstract early paleogene neodymium nd isotopic reconstructions of ocean circulation in the pacific suggest a bipolar mode of overturning circulation characterized by convection of deep water masses from 70 to at least 40 ma this mode is fundamentally different from the sluggish diffusive mode that characterizes the modern north pacific therefore major reorganization of pacific circulation must have occurred between 40 ma and the modern to investigate the potential timing of such a reorganization we present new nd isotope data from drill sites spanning 40 to 10 ma here we use nd isotopic analyses to identify the sources of dissolved nd to the pacific in order to evaluate the application of the nd proxy for ancient water mass composition we combine analyses of fossil fish debris sequentially leached oxide coatings and leach residues to further refine our understanding of nd marine geochemical cycling and to contribute new constraints on the paleoceanographic history of the pacific overall these data support previous interpretations of the convection of deep water in the pacific sector of the southern ocean and surface ventilated north pacific deep water formation from 70 to 40 ma the new nd isotope data suggest a gradual transition between 36 and 25 ma a time period characterized by global cooling this transition consists of a change from north pacific nd isotopic signatures controlled by convection and water mass mixing to values heavily influenced by overprinting from other sources of nd to the deep pacific such a transition is consistent with a change in overturning circulation from a paleogene mode to a mode dominated by sluggish diffusive mixing after 25 ma the data indicate a significant contribution of radiogenic dissolved nd to the deep waters of the north pacific the most likely source of radiogenic dissolved nd would have been labile volcanic ash that altered the composition of the water mass as it slowly advected through the north pacific a slowing of overturning circulation in the north pacific could have resulted in diminished poleward heat transport increasing equator to pole thermal gradients and contributing to a cooling global climate

estimating physical parameters of cracked porous oil reservoirs by inverting shear wave splitting summary we present the problem of determining crack density porosity and permeability of cracked porous carbonate reservoirs by examining the origin of anisotropy considered from a physical model of porous reservoir rock with a system of vertical fluid filled cracks this stabilizes the non linear optimization inversion procedure and determines a set of significant reservoir parameters on a basis of qp qs1 and qs2 velocities measured in a vsp experiment

balancing the global oceanic neodymium budget evaluating the role of groundwater the distinctly different end 0 values of the atlantic indian and pacific oceans requires that the residence time of nd in the ocean i e nd be on the order of or less than the ocean mixing time of 500 1500 yr however estimates of nd based on river influxes range from 4000 to 15 000 yr thus exceeding the ocean mixing time in order to reconcile the oceanic nd budget and lower the residence time by roughly a factor of 10 an additional as yet unidentified and hence missing nd flux to the ocean is necessary dissolution of materials deposited on continental margins has previously been proposed as a source of the missing flux in this contribution submarine groundwater discharge sgd is examined as a possible source of the missing nd flux neodymium concentrations n 730 and end 0 values n 58 for groundwaters were obtained from the literature in order to establish representative groundwater values mean groundwater nd concentrations and end 0 values were used along with recent estimates of the terrestrial freshwater component of sgd 6 of river discharge on a global basis to test whether groundwater discharge to the coastal oceans could account for the missing flux employing mean nd concentrations of the compiled data base i e 31 8 nmol kg for all 730 analyses and 11 3 nmol kg for 141 groundwater samples from a coastal aquifer the global terrestrialderived sgd flux of nd is estimated to range between 2 9 10 7 and 8 1 10 7 mol yr these estimates are of the same order of magnitude and within a factor of 2 of the missing nd flux i e 5 4 10 7 mol yr applying the sgd nd flux estimates the global average end 0 of sgd is predicted to be 9 1 which is similar to our estimate for the missing nd flux 9 2 and in agreement with the mean s d end 0 measured in groundwaters i e end 0 8 9 4 2 the similarities in the estimated sgd nd flux and corresponding end 0 values to the magnitude and isotope composition of the missing nd flux are compelling and suggest that discharge of groundwater to the oceans could account for the missing nd flux future investigations should focus on quantifying the nd concentrations and isotope compositions of groundwater from coastal aquifers from a variety of coastal settings as well as the important geochemical reactions that effect nd concentrations in subterranean estuaries in order to better constrain contributions of sgd to the oceanic nd budget

an integrated study of seismic anisotropy and the natural fracture system at the conoco borehole test facility kay county oklahoma a significant body of published work has developed establishing fracture related seismic anisotropy as an observable effect to further the understanding of seismic birefringence techniques in characterizing natural fracture systems at depth an integrated program of seismic and geologic measurements has been conducted at conoco s borehole test facility in kay county oklahoma birefringence parameters inferred from the seismic data are consistent with a vertical fracture model of density 0 04 striking east northeast that direction is subparallel to a fracture set mapped both on the surface and from subsurface data to the in situ maximum horizontal stress and to the inferred microfabric

ensemble water isotope enabled coupled general circulation modeling insights into the 8 2 ka event 1 freshwater forcing has long been postulated as a catalyst for abrupt climate change because of its potential to interfere with thermohaline circulation thc the most recent example may have occurred about 8 2 ka ago with the sudden drainage of glacial lakes agassiz and ojibway into the hudson bay we perform an ensemble of simulations for this freshwater release using the fully coupled atmosphere ocean general circulation model goddard institute for space studies modele r in all cases simulated effects include reduced ocean heat transport and enhanced atmospheric heat transport in the atlantic increased surface albedo through greater low cloud and sea ice cover and local cooling of up to 3 c our suite of ensemble experiments allows us to examine the importance of the initial ocean state in particular the presence or absence of labrador sea water in controlling the magnitude and length of the climate response water isotope tracers included in this model provide an improved means for direct comparisons of the modeled tracer response to water isotope based climate proxy data comparison of model simulations to data implies that there was an abrupt approximate halving of atlantic thc hence providing strong support for the hypothesis that the 8 2 ka event was caused by an abrupt release of fresh water into the north atlantic

low frequency atmospheric acoustic energy associated with vortices produced by thunderstorms an infrasonic observatory collocated with the colorado state university chill radar during the summer of 1995 permitted unique comparisons between severe storm kinematics and detected acoustic energy at subaudible frequencies near 1 hz radar observations of a velocity couplet aloft evolving into a tornado showed a circulation maximum descending for about 30 min while moving to the east the detected infrasound followed the trend of these observations a model of sound radiated from vortex systems predicts frequencies in the range observed these data are interpreted in the context of past infrasonic observations an ongoing study comparing regional tornado and funnel sightings with archived infrasonic data has identified over 100 cases to date where the infrasonic signals occurred at the time of and from the direction of the vortices for some of these cases the distances were greater than 100 km the author and his associates continue to collect datasets to permit further evaluation of infrasonic detection methods

reactivity of neodymium carriers in deep sea sediments implications for boundary exchange and paleoceanography the dissolved neodymium nd isotopic distribution in the deep oceans is determined by continental weathering inputs water mass advection and boundary exchange between particulate and dissolved fractions reconstructions of past nd isotopic variability may therefore provide evidence on temporal changes in continental weathering inputs and or ocean circulation patterns over a range of timescales however such an approach is limited by uncertainty in the mechanisms and importance of the boundary exchange process and the challenge in reliably recovering past seawater nd isotopic composition end from deep sea sediments this study addresses these questions by investigating the processes involved in particulate solution interactions and their impact on nd isotopes a better understanding of boundary exchange also has wider implications for the oceanic cycling and budgets of other particle reactive elements sequential acid reductive leaching experiments at ph 2 5 on deep sea sediments from the western indian ocean enable us to investigate natural boundary exchange processes over a timescale appropriate to laboratory experiments we provide evidence that both the dissolution of solid phases and exchange processes influence the end of leachates which suggests that both processes may contribute to boundary exchange we use major element and rare earth element ree data to investigate the pools of nd that are accessed and demonstrate that sediment leachate end values cannot always be explained by admixture between an authigenic component and the bulk detrital component for example in core wind 24b acid reductive leaching generates end values between 11 and 6 as a function of solution solid ratios and leaching times whereas the authigenic components have end 11 and the bulk detrital component has end 15 we infer that leaching in the mascarene basin accesses authigenic components and a minor radiogenic volcanic component that is more reactive than madagascan derived clays the preferential mobilisation of such a minor component demonstrates that the nd released by boundary exchange could often have a significantly different end composition than the bulk detrital sediment these experiments further demonstrate certain limitations on the use of acid reductive leaching to extract the end composition of the authigenic fraction of bulk deep sea sediments for example the detrital component may contain a reactive fraction which is also acid extractible while the incongruent nature of this dissolution suggests that it is often inappropriate to use the bulk detrital sediment elemental chemistry and or end composition when assessing possible detrital contamination of leachates based on the highly systematic controls observed and evidence from ree patterns on the phases extracted we suggest two approaches that lead to the most reliable extraction of the authigenic end component and good agreement with foraminiferal based approaches either i leaching of sediments without a prior decarbonation step or ii the use of short leaching times and low solution solid ratios throughout

changes in shear wave polarization azimuth with depth in cymric and railroad gap oil fields shear wave s wave polarization azimuths although consistent over large depth intervals changed abruptly and by large amount of various depths in nine component vertical seismic profiling vsp data from the cymric and railroad gap oil fields of the southwest san joaquin basin a simple layer stripping technique made it possible to follow the polarization changes and determine the s wave birefringence over successive depth intervals because the birefringence and polarization azimuth are related to in situ stresses and fracture information from such analysis could be important for reservoir development near offset vsp data from cymrix indicated that the subsurface could be appproximated roughly as two anisotropic layers the upper layer from the surface to 800 ft 240 m had vertical s wave birefringence as large was about 6 percent down to 1300 ft 400 m in the upper layer the polarization azimuth of the fast s wave was n 60 e while in the lower layer it was about n 10 e refinement of the laye

eocene circulation of the southern ocean was antarctica kept warm by subtropical waters 1 near the eocene s close 34 million years ago the climate system underwent one of the largest shifts in earth s history antarctic terrestrial ice sheets suddenly grew and ocean productivity patterns changed previous studies conjectured that poleward penetration of warm subtropical currents the east australian current eac in particular caused eocene antarctic warmth late eocene opening of an ocean gateway between australia and antarctica was conjectured to have disrupted the eac cooled antarctica and allowed ice sheets to develop here we reconstruct eocene paleoceanographic circulation in the tasmanian region using 1 biogeographical distributions of phytoplankton including data from recently drilled ocean drilling program leg 189 sites and 2 fully coupled climate model simulations we find that the eac did not penetrate to high latitudes and ocean heat transport in the region was not greater than modern our results do not support changes in thermal isolation as the primary driver of the eocene oligocene climatic transition

multicomponent near surface correction for land vsp data multicomponent seismic data collected using directional sources are degraded by the wave excitation process due to inaccurate control of the ground motion unequal activation strengths or ground couplings between differently oriented sources and misalignment of the pad these acquisition uncertainties are exacerbated by the complicated near surface scattering present in most seismic areas neither group of effects should be neglected in multicomponent analyses that make use of relative wavefield attributes derived from compressional and shear waves these effects prevent analysis of the direct and reflected waves using procedures based on standard scalar techniques or a prima facia interpretation of the vector wavefield properties even for the seemingly straightforward case of a near offset vertical seismic profile vsp near surface correction using a simple matrix operator designed from the shallowest recordings alleviates many of these interpretational difficulties in near offset vsp data results from application of this technique to direct waves from a nine component vsp shot at the conoco test site facility oklahoma are encouraging the technique corrects for unexpected compressional wave energy from shear wave vibrators and collapses near surface multiples thus facilitating further processing for the upgoing wavefield the method provides a simple and effective processing step for routine application to near offset vsp analyses

nd isotopic structure of the pacific ocean 70 30 ma and numerical evidence for vigorous ocean circulation and ocean heat transport in a greenhouse world the oceanic meridional overturning circulation moc is a crucial component of the climate system impacting heat and nutrient transport and global carbon cycling past greenhouse climate intervals present a paradox because their weak equator to pole temperature gradients imply a weaker moc yet increased poleward oceanic heat transport appears to be required to maintain these weak gradients to investigate the mode of moc that operated during the early cenozoic we compare new nd isotope data with nd tracer enabled numerical ocean circulation and coupled climate model simulations assimilation of new nd isotope data from south pacific deep sea drilling project and ocean drilling program sites 323 463 596 865 and 869 with previously published data confirm the hypothesized moc characterized by vigorous sinking in the south and north pacific 70 to 30 ma compilation of all pacific nd isotope data indicates vigorous distinct and separate overturning circulations in each basin until 40 ma simulations consistently reproduce south pacific and north pacific deep convection over a broad range of conditions but cases using strong deep ocean vertical mixing produced the best data model match strong mixing potentially resulting from enhanced abyssal tidal dissipation greater interaction of wind driven internal wave activity with submarine plateaus or higher than modern values of the geothermal heat flux enable models to achieve enhanced moc circulation rates with resulting nd isotope distributions consistent with the proxy data the consequent poleward heat transport may resolve the paradox of warmer worlds with reduced temperature gradients

algebraic processing techniques for estimating shear wave splitting in near offset vsp data theory1 a vector convolutional model for multicomponent data acquired in an anisotropic earth is used as a basis for developing algebraic solutions to interpret near offset vsp data this interpretation of the cumulative or interval medium response green s tensor for shear waves determines a polarization azimuth for the leading shear wave and the time delay between the fast and slow split waves the algebraic solutions effectively implement least squares eigenanalysis or singular value decomposition although the methodology for shear wave analysis is strictly relevant to a transmission response it can be adapted to surface data for a uniform anisotropic overburden the techniques perform well when calibrated and tested using synthetic seismograms from various anisotropic models noise tests demonstrate the sensitivity of the interval measurements to local interferences particularly if the shear waves are generated by one source although the algorithms are faster than numerical search routines this is not seen as their major advantage the solutions may have potential in near real time interpretation of shear wave data in well logging where they may be coded on a microchip to provide a direct stream of separated shear waves or polarization and birefringence information there may also be some benefit for large prestack multicomponent surface data sets where the solutions provide a direct transformation to the split shear wave components reducing the storage space for further processing

deglacial variability of antarctic intermediate water penetration into the north atlantic from authigenic neodymium isotope ratios 1 understanding intermediate water circulation across the last deglacial is critical in assessing the role of oceanic heat transport associated with atlantic meridional overturning circulation variability across abrupt climate events however the links between intermediate water circulation and abrupt climate events such as the younger dryas yd and heinrich event 1 h1 are still poorly constrained here we reconstruct changes in antarctic intermediate water aaiw circulation in the subtropical north atlantic over the past 25 kyr by measuring authigenic neodymium isotope ratios in sediments from two sites in the florida straits our authigenic nd isotope records suggest that there was little to no penetration of aaiw into the subtropical north atlantic during the yd and h1 variations in the northward penetration of aaiw into the florida straits documented in our authigenic nd isotope record are synchronous with multiple climatic archives including the greenland ice core 18o record the cariaco basin atmosphere 14c reconstruction the bermuda rise sedimentary pa th record and nutrient and stable isotope data from the tropical north atlantic the synchroneity of our nd records with multiple climatic archives suggests a tight connection between aaiw variability and high latitude north atlantic climate change

anisotropy survey for reservoir definition summary in the context of franco soviet cooperation a seismic survey was carried out on the romashkino reservoir in the tatar republic ussr this survey involved evaluating azimuthal anisotropy parameters from s wave vsps recorded on three wells and from a surface seismic line the latter in order to monitor any lateral variations in the parameters in this paper we present results which indicate in particular that for the two wells in which oil production has been established the anisotropy rate appears to be proportional to production figures this seems to confirm the hypothesis that variations in production are asociated with the presence of subvertical fractures which cause s wave birefringence by processing the reflected converted p s waves of a surface seismic line it is possible to monitor lateral variations in the anisotropy parameters and well ties effectively confirm differences revealed by the s wave vsp data

infrasound associated with 2004 2005 large sumatra earthquakes and tsunami 1 large earthquakes that occurred in the sumatra region in 2004 and 2005 generated acoustic waves recorded by the diego garcia infrasound array the progressive multi channel correlation pmcc analysis is performed to detect the seismic and infrasound signals associated with these events the study is completed by an inverse location procedure that permitted reconstruction of the source location of the infrasonic waves the results show that ground motion near the epicenter and vibrations of nearby land masses efficiently produced infrasound the analysis also reveals unique evidence of long period pressure waves from the tsunami earthquake m9 0 of december 26 2004

fracture characterization from near offset vsp inversion a global optimization method incorporating a ray tracing scheme is used to invert observations of shear wave splitting from two near offset vsps recorded at the conoco borehole test facility kay county oklahoma inversion results suggest that the seismic anisotropy is due to a non vertical fracture system this interpretation is constrained by the vsp acquisition geometry for which two sources are employed along near diametrically opposite azimuths about the well heads a correlation is noted between the time delay variations between the fast and slow split shear waves and the sandstone formations

shear wave polarizations and subsurface stress directions at lost hills field 2 2 s wave data matrix accomplished by computationally rotating sources and receivers although polarization directions obtained by assuming a homogeneous subsurface were moderately consistent with depth considerable improvement in consistency resulted from analytically stripping off a thin near surface layer whose fast s wave polarization direction was about n 6 e s wave birefringence for vertical travel averaged 3 percent in two zones 200 700 ft and 1200 2100 ft 60 210 m and 370 640 m which had closely similar s wave polarizations between those zones the polarization direction changed and the birefringence magnitude was not well defined s wave polarizations from two concentric rings of offset vsps were consistent in azimuth with one another and with polarizations of the near offset vsp this consistency argues strongly for the robustness of the s wave polarization technique as applied in this area the s wave polarization pattern in offset data fits a model of vertical cracks striking n 55 e

infrasound from earthquakes 1 infrasonic signals have been observed from 31 earthquakes by arrays of microphones operated by the los alamos national laboratory between 1983 and 2003 the properties of the signals are presented signal amplitudes corrected for propagation and distance show a relation with seismic magnitude the variance in the relation is understood primarily in terms of the uncertainties or errors in the ground motion deduced from an independent data set and the stratospheric winds which strongly influence signal propagation signal durations can extend over many minutes a relation is found between signal duration and magnitude to understand this we propose a model in which regions distant from the epicenter are excited by seismic surface waves the surface motion of these regions in turn produces signals which precede or follow the signals from the epicenter analysis failed to detect signals from 56 earthquakes during the observation period predicted signal to noise ratios for these earthquakes indicated that the signals would have been too weak for detection

travel time analysis of borehole seismic data a method is presented for reducing travel time data from multiple offset borehole seismic experiments to velocity depth structure the technique which treats simultaneously data from any number of depths in the borehole in addition to surface data is based on the linear inversion scheme of dorman and jacobson 1981 given the parameters p t p px p and p t p px p the method solves for depth to specified slownesses assuming linear gradients in velocity between slowness values a practical limitation on the use of surface travel time measurements to resolve velocity depth structure is the necessity of assuming a surface velocity this is not necessary for the case of borehole data for a borehole receiver the velocity at the depth of the receiver can be obtained from the slope of the inflection point of the travel time curve thus a direct measure of the uppermost velocity of a section can be obtained from the travel time data of a shallow borehole receiver estimation of velocities from the inflection points of deeper receivers improves the resolution of the velocity depth function which would be obtained from surface data alone the technique is applied to data from three borehole seismic experiments in oceanic crust the experiments were carried out in the western atlantic crustal age 110 m y the gulf of california crustal age 1 m y and the costa rica rift area crustal age 6 m y all three experiments show relatively high upper crustal velocities 4 0 km s suggesting that layer 2a is not present even in the very young crust all sites had over 100 m of sediment thickness and it is postulated that sediment thickness and sediment permeability not merely age govern the velocity of the upper crust by accelerating the cementation of fractures and cracks

a potential barrier to deep antarctic circumpolar flow until the late miocene the central scotia sea located between the south american and antarctic plates is an integral part of the marine conduit that permits eastward deep water flow from the pacific ocean to the atlantic ocean the geologic history of the central scotia sea is therefore critical for a full understanding of the initiation and subsequent evolution of the complete deep antarctic circumpolar current widely believed to have been a key factor in the history of antarctic glaciation here we present new evidence on the nature and age of the central scotia sea floor multibeam surveys and the first dredged samples indicate that a now submerged remnant volcanic arc may have formed a barrier to deep eastward oceanic circulation until after the mid miocene climatic optimum inception and development of a full deep antarctic circumpolar current may therefore have been important not in the drop in global temperatures at the eocene oligocene boundary as long surmised but in the subsequent late miocene global cooling and intensification of antarctic glaciation

interpreting data matrix asymmetry in near offset shear wave vsp data poor experimental control in shear wave vsps may contribute to unreliable estimates of shear wave splitting and possible misinterpretation of the medium anisotropy to avoid this the acquisition and processing of multicomponent shear wave data needs special care and attention measurement of asymmetry in the recorded data matrix using singular value decomposition svd provides a useful way of examining possible acquisition inaccuracies and may help guide data conditioning and interpretation to ensure more reliable estimates of shear wave polarization azimuth three examples demonstrate how variations in shear wave polarization and acquisition inaccuracies affect the svd results in different ways in the first example analysis of synthetic seismograms with known depth changes in the polarization azimuth show how these may be detected in the second example a known source re orientation and polarity reversal is detected by applying svd to near offset shear wave vsp data recorded in the romashkino fiel

seismic imaging of the shallow subsurface shear wave case histories obtaining high resolution images of the geology and hydrogeology of the subsurface in the depth range from ground level to 50 m is one of the major challenges of modern geophysics the methods which are commonly used such as compressional wave surveys and ground penetrating radar often suffer from adverse effects caused by the near surface conditions changes in water saturation and various sources of noise this paper demonstrates some of the advantages offered by the use of shear wave seismology and by the combination of shear and compressional wave seismic methods in shallow subsurface investigations multicomponent shallow seismic tests were carried out at four different sites to examine the effectiveness of different acquisition geometries under a variety of near surface geological conditions near surface conditions encountered at the sites included thick clays clay sand sequences overlying chalk mudstone overlying granodiorite bedrock and landfill material under all conditions shear wave data acquisition was found to have advantages over compressional wave acquisition for the investigation of the shallow subsurface shear head waves being unaffected by water saturation achieved penetration to greater depths at a site in crewkerne dorset where compressional head wave penetration was limited to the near surface layers better vertical resolution was achieved at shallow depths using shear wave reflection energy at a landfill site shear wave reflections from shallow interfaces were in some cases less affected by noise compared with the equivalent compressional wave reflections combinations of shear and compressional wave data recording allowed the measurement of a poisson s ratio log and gave indications of seismic anisotropy at two sites where dipping clay layers were present

evolution of atlantic thermohaline circulation early oligocene onset of deep water production in the north atlantic the flow of deep water masses is a key component of heat transport in the modern climate system yet the role of deep ocean heat transport during periods of extreme warmth is poorly understood the present mode of meridional overturning circulation is characterized by deep water formation in both the north atlantic and the southern ocean however a different mode of meridional overturning circulation operated during the extreme greenhouse warmth of the early cenozoic during which time the southern ocean was the dominant region of deep water formation the combination of general global cooling and tectonic evolution of the atlantic basins over the past 55 m y ultimately led to the development of a mode of overturning circulation characterized by both southern ocean and north atlantic deep water sources the change in deep water circulation mode may in turn have affected global climate however unraveling the causes and consequences of this transition requires a better understanding of the timing of the transition new nd isotope data from the southeastern atlantic ocean indicate that the initial transition to a bipolar mode of deep water circulation occurred in the early oligocene ca 33 ma the likely cause of significant deep water production in the north atlantic was tectonic deepening of the sill separating the greenland norwegian sea from the north atlantic

neodymium isotopic composition and concentration in the western north atlantic ocean results from the geotraces ga02 section the neodymium nd isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation the modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete here we present new observational data for nd isotopes and concentrations from twelve seawater depth profiles which follow the flow path of north atlantic deep water nadw from its formation region in the north atlantic to the northern equatorial atlantic samples were collected during two cruises constituting the northern part of the dutch geotraces transect ga02 in 2010 the results show that the different water masses in the subpolar north atlantic ocean which ultimately constitute nadw have the following nd isotope characteristics upper labrador sea water ulsw end 14 2 0 3 labrador sea water lsw end 13 7 0 9 northeast atlantic deep water neadw end 12 5 0 6 northwest atlantic bottom water nwabw end 11 8 1 4 in the subtropics where these source water masses have mixed to form nadw which is exported to the global ocean upper nadw is characterised by end values of 13 2 1 0 2sd and lower nadw exhibits values of end 12 4 0 4 2sd while both signatures overlap within error the signature for lower nadw is significantly more radiogenic than the traditionally used value for nadw end 13 5 due to the dominance of source waters from the nordic seas nwabw and neadw comparison between the concentration profiles and the corresponding nd isotope profiles with other water mass properties such as salinity silicate concentrations neutral densities and chlorofluorocarbon cfc concentration provides novel insights into the geochemical cycle of nd and reveals that different processes are necessary to account for the observed nd characteristics in the subpolar and subtropical gyres and throughout the vertical water column while our data set provides additional insights into the contribution of boundary exchange in areas of sediment resuspension the results for open ocean seawater demonstrate at an unprecedented level the suitability of nd isotopes to trace modern water masses in the strongly advecting western atlantic ocean

towards explaining the nd paradox using reversible scavenging in an ocean general circulation model abstract the isotopic composition of the rare earth element neodymium nd has the potential to serve as water mass tracer because it is naturally tagged by continental sources with distinct ages and lithologies however in order to understand the limitations of this approach we need to know more about the physical and biogeochemical processes controlling the distribution of nd in the modern ocean for example nd isotope ratios behave quasi conservatively while concentrations in the water column generally increase with depth showing a broadly nutrient like behaviour we define this decoupling of nd concentrations and isotopic compositions as the nd paradox for the first time we model nd concentrations and isotopic compositions simultaneously and address the hypothesis that the nd paradox can be explained by a combination of lateral advection and reversible scavenging we impose a reversible scavenging model of nd removal from the ocean on the ocean circulation fields from the mit general circulation model using the transport matrix method we conclude that reversible scavenging is an active and important component in the cycling of nd in the ocean in the absence of an adequate alternative explanation reversible scavenging should be considered a necessary component in explaining the nd paradox

nd isotopic composition in the central north pacific three vertical profiles of seawater concentration and isotopic composition of nd were determined for the western to central north pacific ocean in the subarctic oceanic region at depths greater than 500 m one vertical profile of nd isotopic composition was indistinguishable from most previously reported profiles from here the data indicate a rather homogeneous nd isotopic composition in the subarctic oceanic region at middle to deep depths 500 m two stations in the subtropical oceanic region exhibited similar nd isotopic composition profiles to those previously reported the maxima end values at depths of 800 1000 m end 3 4 to 2 7 which correspond to the north pacific intermediate water npiw are found at both subtropical stations this implies a ubiquitous distribution of npiw showing a radiogenic end value in the north pacific the subsurface minimum at a depth of 200 m which indicates the penetration of the north pacific tropical water nptw with an unradiogenic nd isotopic signal was observed at one station in the western pacific this station had much lower end than the central station at depths around 5000 m suggesting the greater prominence of antarctic bottom water aabw in the western subtropical pacific than in the central to eastern subtropical pacific results of a model calculation assuming boundary exchange indicate that the hawaiian islands play an important role in supplying radiogenic nd to the central pacific similar to some continental margins we show that nd isotopic composition is a versatile tracer for ocean circulation and the geochemical cycle of nd in the north pacific further studies on the distribution of nd isotopic composition in the pacific ocean including the southern pacific will better elucidate the circulation and geochemical cycle of nd in the pacific

tracing the history of submarine hydrothermal inputs and the significance of hydrothermal hafnium for the seawater budget a combined pb hf nd isotope approach secular variations in the pb isotopic composition of a mixed hydrogenous hydrothermal ferromanganese crust from the bauer basin in the eastern equatorial pacific provide clear evidence for changes in hydrothermal contributions during the past 7 myr the nearby galapagos rise spreading center provided a strong hydrothermal flux prior to 6 5 ma after 6 5 ma the pb became stepwise more radiogenic and more similar to equatorial pacific seawater reflecting the westward shift of spreading to the presently active east pacific rise epr a second previously unrecognized enhanced hydrothermal period occurred between 4 4 and 2 9 ma which reflects either off axis hydrothermal activity in the bauer basin or a late stage pulse of hydrothermal pb from the then active but waning galapagos rise spreading center hafnium isotope time series of the same mixed hydrogenous hydrothermal crust show invariant values over the past 7 myr hafnium isotope ratios as well as nd isotope ratios obtained for this crust are identical to that of hydrogenous equatorial pacific deep water crusts and clearly indicate that hydrothermal hf similar to nd does not travel far from submarine vents therefore we suggest that hydrothermal hf fluxes do not contribute significantly to the global marine hf budget

tropical sea temperatures in the high latitude south pacific during the eocene sea surface temperature sst estimates of 30 c from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the canterbury basin new zealand support paleontological evidence for a warm subtropical to tropical climate in the early eocene high latitude 55 s southwest pacific such warm ssts call into question previous estimates based on oxygen isotopes and present a major challenge to climate modelers even under hypergreenhouse conditions 2240 ppm co2 modeled summer ssts for the new zealand region do not exceed 20 c

a case example of near surface correction for multicomponent vsps a deterministic near surface correction procedure is developed for multicomponent vsp data shot using directional sources and recorded using three component receivers the method is capable of removing unwanted effects of acquisition such as unequal source strengths or misorientations but may also remove near surface multiples and anisotropy this is of considerable benefit for obtaining accurate and consistent estimates of subsurface anisotropy from different source combinations application of the technique is illustrated using a dataset from the romashkino reservoir in russia where three or four different directional sources are used at the same source locations the technique corrects for the large discrepancies which exist between the estimates obtained using different source combinations application of the technique to three wells in the survey region reveals a nearly isotropic subsurface except for a few isolated zones of moderate to high 2 to 8 anisotropy which lie close to the expected depth for the reservoir although there is no significant correlation with the production figures for each well the qs1 polarization azimuth within the reservoir does vary at each well location suggesting that this may be a more sensitive indicator of reservoir drocess

computer processing of vertical seismic profile data vertical seismic profiles vsp are a powerful tool in a variety of seismic exploration situations only after extensive computer processing of the raw field data however can the full value of this tool be realized with the help of processing relations between important rock parameters and acoustic properties can sometimes be established and highly reliable ties from well logs to surface seismic profiles can usually be obtained the basic theory of the processing techniques is well known however the techniques used in processing standard surface seismic profiles usually must be modified to adapt them to the unique conditions associated with vsps processing procedures and their relevance to the interpretation of vsp and surface seismic profile data are described

neodymium isotopic variations in north pacific modern silicate sediment and the insignificance of detrital ree contributions to seawater the neodymium isotopic composition of the silicate fraction of holocene pelagic sediments from the north pacific define two provinces a central north pacific province characterized by unradiogenic and remarkably homogeneous end 10 2 0 5 and a narrow circum pacific marginal province characterized by more radiogenic and variable end 4 2 3 8 the silicate fraction in the central north pacific is exclusively eolian based on prevailing wind patterns meteorological data and neodymium isotopic data the only significant sediment source is chinese loess leaching experiments on chinese loess confirm that leachable nd is isotopically indistinguishable from bulk and residual silicate nd silicates in the circum north pacific marginal province comprise eolian loess volcanic ash and hemipelagic sediments derived from volcanic arcs a compilation of pacific seawater and mn nodule end data shows no clear spatial variation except for a general decrease from surface to deep waters from 3 to 4 and slightly lower end in bottom waters along the western north pacific due to the incursion of antarctic bottom water the relative homogeneity of bottom water end which contrasts sharply with the distinctive variation in sediment end plus the large difference between the average end of bottom waters and the central north pacific eolian silicates 4 vs 10 suggests that any contribution of ree to seawater from eolian materials is insignificant furthermore leaching of ree from eolian particles as they sink though the water column must be insignificant because nd in shallow waters is more radiogenic than nd in deeper waters that there is no contrast in the nd isotopic composition of bottom waters that overlie the central and marginal sediment provinces suggests that the ash and hemipelagic sediments derived from pacific rim volcanic arcs also contribute minimal ree to seawater the elimination of eolian ash and hemipelagic sediments leaves only near shore riverine particulates as a possibly significant particulate source of ree to seawater

convection of north pacific deep water during the early cenozoic the history of deep water formation and abyssal flow is poorly known but important to establish in order to develop a better understanding of changes in oceanic mass heat salt and nutrient transport north atlantic high latitude regions currently are the dominant deep water producers but paleogeographic constraints proxy interpretations and physical models have suggested other modes for the past such as those characterized by high latitude pacific sources subtropical sources or widespread nonlocalized sources here we present new north pacific late cretaceous paleogene nd isotope data from fossil fish debris and detrital silicates combined with results of coupled climate model simulations to test these hypothesized circulation modes the data and model simulations support a circulation mode characterized by high latitude bipolar pacific convection deep convection in the north pacific and likely the south pacific was most intense during the relatively cool portion of the late cretaceous paleocene and waned prior to the peak global warmth of the early eocene ca 52 ma

velocity determination from offset vertical seismic profiling data two methods of computing interval velocities from offset vertical seismic profiles are developed based on a horizontally layered earth model the first method is a simple iteration procedure by which layer velocities are sequentially computed for any given layer the take off angle for the ray arriving at the geophone at the bottom of the layer is varied until the velocity computed from travel time differs from the velocity obtained from snell s law by less than some specified value this is similar to the shooting method in ray tracing this method requires as many layers as geophone locations the second method is more general and the only requirements are that the number of layers be equal to or smaller than the number of geophone locations and that the rays arrive at the geophones from above this method is based on the iterative solution of a linearized problem obtained by expanding travel times and horizontal distances in taylor series as functions of velocities and p parameters up to first order in dv s and dp s perturbations in velocities and p parameters respectively and assuming initial estimates vo s and po s close to the optimum solution the resulting linear system is solved using a simplified version of the levenberg marquardt algorithm due to the simple structure of the ensuing matrix of derivatives for each iteration the problem reduces to the solution of an inverse problem for the velocities alone plus the solution of a vector equation for the p parameters this method is fast and convergence is attained even in the case of poor initial estimates

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

antarctic climate southern ocean circulation patterns and deep water formation during the eocene we assess early to middle eocene seawater neodymium nd isotope records from seven southern ocean deep sea drill sites to evaluate the role of southern ocean circulation in long term cenozoic climate change our study sites are strategically located on either side of the tasman gateway and are positioned at a range of shallow 500 m to intermediate deep 1000 2500 m paleowater depths unradiogenic seawater nd isotopic compositions reconstructed from fish teeth at intermediate deep indian ocean pelagic sites ocean drilling program odp sites 738 and 757 and deep sea drilling project dsdp site 264 indicate a dominant southern ocean sourced contribution to regional deep waters end t 9 3 1 5 iodp site u1356 off the coast of adelie land a locus of modern day antarctic bottom water production is identified as a site of persistent deep water formation from the early eocene to the oligocene east of the tasman gateway an additional local source of intermediate deep water formation is inferred at odp site 277 in the sw pacific ocean end t 8 7 1 5 antarctic proximal shelf sites odp site 1171 and site u1356 reveal a pronounced erosional event between 49 and 48 ma manifested by 2 end unit negative excursions in seawater chemistry toward the composition of bulk sediments at these sites this erosional event coincides with the termination of peak global warmth following the early eocene climatic optimum and is associated with documented cooling across the study region and increased export of antarctic deep waters highlighting the complexity and importance of southern ocean circulation in the greenhouse climate of the eocene

bottoms up sedimentary control of the deep north pacific ocean s end signature the ability to reconstruct past ocean currents is essential for determining ocean circulation9s role in global heat transport and climate change our understanding of the relationship between circulation and climate in the past allows us to predict the impact of future climate driven circulation changes one proposed tracer of past ocean circulation is the neodymium isotope composition e nd of ancient water masses however ambiguities in what governs the e nd distribution in the modern ocean hamper interpretations of this tracer here we present e nd values for marine pore fluids sediments and the overlying water column for three sites in the north pacific we find that ocean bottom water e nd e nd bw in the northeast pacific lies between the value expected for the water mass 3 3 and the measured e nd of sediment pore fluid e nd pw 1 8 moreover e nd pw resembles the e nd of the sediment combined these findings are consistent with recent assessments that sediment pore fluids may be a major source of rare earth elements to the ocean and suggest that the benthic flux of nd from pore fluids exerts the primary control over the deep ocean distribution of e nd

evidence for deep water production in the north pacific ocean during the early cenozoic warm interval the deep ocean circulation is responsible for a significant component of global heat transport in the present mode of circulation deep waters form in the north atlantic and southern oceans where surface water becomes sufficiently cold and dense to sink polar temperatures during the warmest climatic interval of the cenozoic era approximately 65 to 40 million years myr ago were significantly warmer than today and this may have been a consequence of enhanced oceanic heat transport however understanding the relationship between deep ocean circulation and ancient climate is complicated by differences in oceanic gateways which affect where deep waters form and how they circulate here i report records of neodymium isotopes from two cores in the pacific ocean that indicate a shift in deep water production from the southern ocean to the north pacific approximately 65 myr ago the source of deep waters reverted back to the southern ocean 40 myr ago the relative timing of changes in the neodymium and oxygen isotope records indicates that changes in cenozoic deep water circulation patterns were the consequence not the cause of extreme cenozoic warmth

extracting foraminiferal seawater nd isotope signatures from bulk deep sea sediment by chemical leaching the seawater radiogenic neodymium 143nd 144nd isotope signature is an invaluable tool for the reconstruction of past deep water provenance sedimentary foraminifera or fish teeth are among the most reliable archives known for nd isotope based reconstructions of past seawater as the distribution and preservation of these archives are limited the extraction of hydrogenetic ferromanganese oxyhydroxides from bulk sediments provide an easily applicable alternative this method however implies the risk of generating artefacts due to the possible release of non seawater derived nd during the extraction procedure here we revisit and further investigate the reliability of the extraction of seawater derived nd isotope signatures via leaching of bulk deep sea sediments with two commonly used buffered acetic acid and acid reductive mix solutions repeated application of such stepwise leaching procedures to different non decarbonated sediments from distinct settings across the deep atlantic ocean shows pronounced elemental and nd isotope trends during the leaching process in the laboratory our results show that seawater nd isotope compositions are extracted together with carbonates and manganese oxides only at the beginning of the leaching series during chemical extraction the carbonates effectively work as a buffer preventing acid induced mobilisation of fe oxides and volcanogenic material once this buffer is consumed potentially present volcanogenic phases are considerably attacked leading to shifts in the extracted nd isotope signal of up to 12 epsilon units such volcanogenic phases are a significant source of contaminant nd reflected by markedly elevated al nd signatures we consequently propose a revised weak leaching protocol for carbonate bearing deep sea sediments which is simple to use provides excellent agreement with data obtained from uncleaned foraminifera and can be easily screened for contamination

constraints on the magnitude of the deglacial migration of the itcz in the central equatorial pacific ocean abstract accurate paleo latitudinal reconstructions of the intertropical convergence zone itcz are necessary for understanding tropical hydroclimate and atmospheric circulation paleoclimate models and records suggest that as global temperatures increase the itcz should migrate towards the warmer hemisphere many uncertainties remain regarding the magnitude of this migration and few studies have focused on the central equatorial pacific cep here we use eolian dust records recovered from three locations in the cep to address changes in dust provenance across the paleo itcz since the last glacial maximum lgm radiogenic isotope compositions of nd and pb show that dust delivered to the cep was sourced mainly from two regions east asia and south america from these data we deduced that since marine oxygen isotope stage 2 mis2 the itcz has migrated north to its modern position being displaced by as much as 7 to as little as 2 5 we find that the itcz migrated further north during the early holocene 9 kyr reaching its position furthest north during the mid holocene warm interval 7 kyr based on an increase in south american dust at the northernmost sites

evolution of nd and pb isotopes in central pacific seawater from ferromanganese crusts abstract hydrogenetic ferromanganese crusts incorporate elements from ambient seawater during their growth on seamounts by analysing nd pb and be isotope profiles within crusts it is possible to reconstruct seawater tracer histories depth profiles of 10be 9be ratios in three pacific ferromanganese crusts have been used to obtain growth rates which are between 1 4 and 3 8 mm ma nd and pb isotopes provide intact records of isotopic variations in pacific seawater over the last 20 ma or more there were only small changes in pb isotope composition in the last 20 ma this indicates a constant pb composition for the erosional sources and suggests further that erosional nd inputs may have been uniform too end values vary considerably with time and most probably reflect changes in ocean circulation the end values of the crusts not only vary as a function of age but also as a function of water depth from 25 to 0 ma crust va13 2 from 4 8 km water depth has a similar pattern of end variation to the two shallower crusts from 1 8 and 2 3 km but about 1 0 to 1 5 units more negative this suggests that end stratification in pacific seawater as demonstrated for the present day has been maintained for at least 20 ma each crust shows a decrease in end from 3 5 ma to the present which is interpreted in terms of an increase in the nadw component present in the pacific from 10 to 3 5 ma ago the crusts show an increase in end this suggests a decreasing role for a deep water source with end less than circum pacific sources in this regard the panamanian gateway restriction from 10 ma with final closure at 3 5 ma may have played an important role in reducing access of atlantic derived nd to the pacific

processing of a nine component near offset vsp for seismic anisotropy a convolutional sequence of matrix operators is offered as a convenient deterministic scheme for processing a multicomponent vertical seismic profile vsp this sequence is applied to a nine component near offset vsp recorded at the conoco borehole test facility kay county oklahoma these data are corrected for tool spin and near surface anisotropy together with source coupling or imbalance after wave field separation using a standard f k filter each source and receiver pair for the upgoing waves is adjusted to a common reference depth using a matrix operator based on the downgoing wavefield the up and downgoing waves are then processed for anisotropy by a similarity transformation to separate the qs1 and qs2 waves from which the anisotropic properties are estimated these estimates reveal a strong apparent vertical birefringence in the near surface but weak or moderate values for the majority of the subsurface the target zone consists of a thin sandstone and deeper shale layer both of which possess a strong vertical birefringence the sandstone corresponds to a zone of known fluid flow an observed qs2 attenuation and polarization change in the shale suggest it contains large fractures

neodymium isotopic characterization of ross sea bottom water and its advection through the southern south pacific since the inception of the international geotraces program studies investigating the distribution of trace elements and their isotopes in the global ocean have significantly increased in spite of this large scale effort the distribution of neodymium isotopes 143nd 144nd end and concentrations nd in the high latitude south pacific is still understudied specifically north of the antarctic polar front apf here we report dissolved nd isotopes and concentrations from 11 vertical water column profiles from the south pacific between south america and new zealand and across the antarctic frontal system results confirm that ross sea bottom water rsbw is represented by an endvalue of 7 and for the first time show that these nd characteristics can be traced into the southeast pacific until progressive mixing with ambient lower circumpolar deep water lcdw dilutes this signal north of the apf that is endbehaves conservatively in rsbw opening a path for studies of past rsbw behavior neodymium concentrations show low surface concentrations and a linear increase with depth north of the apf south of the apf surface nd is high and increases with depth but remains almost constant below 1000m this vertical and spatial nd pattern follows the southward shoaling density surfaces of the southern ocean and hence suggests supply of nd to the upper ocean through upwelling of nd rich deep water low particle abundance due to reduced opal production and seasonal sea ice cover likely contributes to the maintenance of the high upper ocean nd south of the apf this suggests a dominant lateral transport component on nd and a reduced vertical control on nd concentrations in the south pacific south of the apf

cenozoic climate changes a review based on time series analysis of marine benthic δ18o records the climate during the cenozoic era changed in several steps from ice free poles and warm conditions to ice covered poles and cold conditions since the 1950s a body of information on ice volume and temperature changes has been built up predominantly on the basis of measurements of the oxygen isotopic composition of shells of benthic foraminifera collected from marine sediment cores the statistical methodology of time series analysis has also evolved allowing more information to be extracted from these records here we provide a comprehensive view of cenozoic climate evolution by means of a coherent and systematic application of time series analytical tools to each record from a compilation spanning the interval from 4 to 61 myr ago we quantitatively describe several prominent features of the oxygen isotope record taking into account the various sources of uncertainty including measurement proxy noise and dating errors the estimated transition times and amplitudes allow us to assess causal climatological tectonic influences on the following known features of the cenozoic oxygen isotopic record paleocene eocene thermal maximum eocene oligocene transition oligocene miocene boundary and the middle miocene climate optimum we further describe and causally interpret the following features paleocene eocene warming trend the two step long term eocene cooling and the changes within the most recent interval miocene pliocene we review the scope and methods of constructing cenozoic stacks of benthic oxygen isotope records and present two new latitudinal stacks which capture besides global ice volume also bottom water temperatures at low less than 30 and high latitudes this review concludes with an identification of future directions for data collection statistical method development and climate modeling

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

preservation of seawater sr and nd isotopes in fossil fish teeth bad news and good news abstract we analyzed 87sr 86sr ratios in foraminifera pore fluids and fish teeth for samples ranging in age from eocene to pleistocene from four ocean drilling program sites distributed around the globe site 1090 in the cape basin of the southern ocean site 757 on the ninetyeast ridge in the indian ocean site 807 on the ontong java plateau in the western equatorial pacific and site 689 on the maud rise in the southern ocean sr isotopic ratios for dated foraminifera consistently plot on the global seawater sr isotope curve for sites 1090 757 and 807 sr isotopic values of the pore fluids are generally less radiogenic than contemporaneous seawater values as are values for fossil fish teeth in contrast pore fluid 87sr 86sr values at site 689 are more radiogenic than contemporaneous seawater and the corresponding fish teeth also record more radiogenic values thus sr isotopic values preserved in fossil fish teeth are consistently altered in the direction of the pore fluid values furthermore there is a correlation between the magnitude of the offset between the pore fluids and the seawater curve and the associated offset between the fish teeth and the seawater curve these data suggest that the hydroxyfluorapatite of the fossil fish teeth continues to recrystallize and exchange sr with its surroundings during burial and diagenesis therefore sr chemostratigraphy can be used to determine rough ages for fossil fish teeth in these cores but cannot be used to fine tune age models in contrast to the sr isotopic system our nd concentration data combined with published isotopic and rare earth element data suggest that fish teeth acquire nd during early diagenesis while they are still in direct contact with seawater the concentrations of nd acquired at this stage are extremely high relative to the concentrations in surrounding pore fluids as a result nd isotopes are not altered during burial and later diagenesis therefore fossil fish teeth from a variety of marine environments preserve a reliable and robust record of deep seawater nd isotopic compositions from the time of deposition

observations of infrasound and subsonic disturbances related to severe weather summary during the past 10 years the geoacoustics group of noaa s wave propagation laboratory studied travelling low frequency pressure variations related to thunderstorms and severe weather two general categories of waves were associated with severe weather conditions subsonic pressure disturbances and infrasonic waves with acoustic velocities the low frequency pressure variations were measured at the earth s surface using microphone arrays located at times thousands of kilometres from the severe weather disturbance the radiated infra sound was related to thunderstorms penetrating the tropopause and spectral analyses were performed on several signals possible practical applications to storm warning and classification are discussed for both infrasound and subsonic pressure disturbances past measurements of these signals are reviewed

timing and climatic consequences of the opening of drake passage age estimates for the opening of drake passage range from 49 to 17 million years ago ma complicating interpretations of the relationship between ocean circulation and global cooling secular variations of neodymium isotope ratios at agulhas ridge southern ocean atlantic sector suggest an influx of shallow pacific seawater approximately 41 ma the timing of this connection and the subsequent deepening of the passage coincide with increased biological productivity and abrupt climate reversals circulation productivity linkages are proposed as a mechanism for declining atmospheric carbon dioxide these results also indicate that drake passage opened before the tasmanian gateway implying the late eocene establishment of a complete circum antarctic pathway

acoustic detection tracking and characterization of three tornadoes acoustic data recorded at 1000 samples per second by two sensor arrays located at ranges of 1 113 km from three tornadoes that occurred on 24 may 2011 in oklahoma are analyzed accurate bearings to the tornadoes have been obtained using beamforming methods applied to the data at infrasonic frequencies beamforming was not viable at audio frequencies but the data demonstrate the ability to detect significant changes in the shape of the estimated power spectral density in the band encompassing 10 hz to approximately 100 hz at distances of practical value from the sensors this suggests that arrays of more closely spaced sensors might provide better bearing accuracy at practically useful distances from a tornado additionally a mathematical model based on established relationships of aeroacoustic turbulence is demonstrated to provide good agreement to the estimated power spectra produced by the tornadoes at different times and distances from the sensors the results of this analysis indicate that qualit

inversion for seismic anisotropy using genetic algorithms1 a general inversion scheme based on a genetic algorithm is developed to invert seismic observations for anisotropic parameters the technique is applied to the inversion of shear wave observations from two azimuthal vsp data sets from the conoco test site in oklahoma horizontal polarizations and time delays are inverted for hexagonal and orthorhombic symmetries the model solutions are consistent with previous studies using trial and error matching of full waveform synthetics the shear wave splitting observations suggest the presence of a shear wave line singularity and are consistent with a dipping fracture system which is known to exist at the test site application of the inversion scheme prior to full waveform modelling demonstrates that a considerable saving in time is possible whilst retaining the same degree of accuracy

seawater nd isotope variation in the western pacific ocean since 80 ma odp 807 ontong java plateau abstract this study reports neodymium isotopic end variability at a time resolution of 0 5 to 3 ma since the late cretaceous as recorded in a marine sedimentary core from the western pacific odp 807 3 36 n 156 3 e ontong java plateau our core is mainly fine grained and composed of continuous sequences of nannofossil oozes the end measured in the carbonate fraction was used as a proxy of end of seawater of the western pacific on a long term our results indicate a general increase in end of seawater by 4 5 end units from the late cretaceous end 6 to modern times end 1 7 this pattern was related to the emergence of the west pacific margin and the progressive isolation of the pacific ocean from the other oceanic basins resulting in its progressive shift to more radiogenic values through the cenozoic this long term pattern is in accordance with previously published fe mn crusts data from the same study area nonetheless by being at higher time resolution our data records additional sharp and pseudo cyclic variations 7 11 ma periods superimposed on this long term pattern from 40 ma to modern times these oscillations might reflect the alternating dominance of the two main deep water masses npdw and ucdw bathing our study area in the same core we also measured the end in the detrital fraction in order to trace back the local terrigenous inputs the terrigenous record shows a significant variability up to 12 end units this was linked to the emergence of the west pacific subduction zone 50 ma ago causing a higher input of radiogenic isotopes in conclusion the large variability observed in both seawater and detrital end records most probably result from a major tectonic and oceanic circulation reorganization of the pacific ocean