a different perspective on glauconite as a chronometer for geologic time scale studies there are advocates of the use of glauconite as a chronometer for geologic time scale studies who insist that if the geohistory of the sample in question is known in detail one can ascertain before hand that the sample will yield a radiometric result that is accurate in the geological sense examples are presented indicating that while some glauconite samples may yield the correct age within their assigned analytical uncertainties when compared to high temperature minerals others clearly do not and are too young by varying degrees the outright acceptance of published results on glauconite can result in erroneous age estimates of various biostratigraphic levels and stage or epoch boundaries

the interaction of the s wavefield with upper mantle heterogeneity summary many methods for the analysis of long period and broad band s waveforms depend on a representation of the seismic wavefield in terms of a sum of modes of a reference structure in addition it is frequently assumed that the propagation of the modal contributions from source to receiver may be regarded as independent this assumption may not be warranted if there is significant heterogeneity in seismic properties along the propagation path the interaction between modal components in different styles of heterogeneity model for the upper mantle is examined using a coupled mode propagation technique kennett 1984 which allows direct construction of reflection and transmission matrices with full allowance for intermode interactions for 2 d heterogeneity structures the first type of structure considered has been proposed to explain amplitude and traveltime anomalies in body wave studies of upper mantle phases this heterogeneity has an amplitude of about 1 per cent and is distributed with a horizontal scale of around 300 400km and a vertical scale which increases from 70km in the uppermost mantle to 200 km at 900 km depth horizontally travelling s waves are hardly affected by this class of heterogeneity for frequencies less than 0 07 hz the second heterogeneity model was based on the wepl3 model proposed by nolet 1990 from waveform inversion for the structure under the nars array in western europe the heterogeneity reaches 5 per cent deviation from the reference model premc in organized regions 700 km or more in length for this structure surface wave modes with group velocity below 4 2kms can be regarded as propagating independently up to 0 020hz the body wave group of modes with higher group velocity succumbs to significant interaction above 0 040 hz the frequency limit for largely independent propagation for the body wave group of modes can be extended to about 0 05 hz for a velocity model with up to 1 per cent additional variability superimposed on wepl3 such a composite heterogeneity model would be consistent with both body wave and surface wave behaviour the errors introduced into the analysis methods by ignoring mode interactions above these frequency limits will depend on the distribution of energy across the modes imposed by the source and the criterion used for waveform matching between observed and theoretical seismograms theoretical seismograms for the heterogeneity structures based on wepl3 including full allowance for intermode coupling show a distinct phase shift for the fundamental mode when compared with the corresponding calculations for the reference model premc as is indeed observed at the nars stations the parts of the seismograms which show the largest influence from the presence of lateral heterogeneity are those which depend on interference phenomena such as su the disruption of the phase patterns can have a profound influence on the appearance of the waveforms the presence of small scale heterogeneity has very little influence on the seismograms below 0 035 hz but becomes more important as the frequency increases especially for the body wave phases

seismic wavefield calculation for laterally heterogeneous earth models ii the influence of upper mantle heterogeneity summary there is increasing evidence that the earth s mantle is laterally heterogeneous on a broad range of scales but the character of smaller scale heterogeneity has to be deduced indirectly the aim of the present paper is to examine the influence of a variety of stochastic representations of heterogeneity on seismic wave behaviour to help constrain the nature of the variations in seismic properties in the upper mantle for each of the models the seismic wavefield is simulated using a pseudospectral method in a 2 d cylindrical coordinate system the presence of stochastic heterogeneity is particularly important for those parts of the seismic wavefield where a significant portion of the propagation path in the upper mantle is close to horizontal such as the pp and ss phases and fundamental mode and higher mode surface waves the effects are noticeable traveltime anomalies and waveform changes for the body waves particularly associated with phase triplications and significant phase shifts for rayleigh waves a variety of styles of stochastic heterogeneity models are compared for the same source and station configurations using wavefield snapshots and the character of the calculated seismograms the influence of heterogeneity on body waves and on longer period rayleigh waves increases as the scale length increases compared to the wavelength of the seismic waves the aspect ratio of the heterogeneity has a pronounced effect on the coherence and amplitude of traveltime fluctuations and waveform changes across stations at the surface which depend on the structures encountered along the propagation paths to the specific receivers the effect of nearly isotropic heterogeneity is to induce small short scale variations in traveltime fluctuations and waveform changes as the heterogeneity becomes more plate like the fluctuations are on a broader scale and of larger amplitude because the individual patches of heterogeneity have a stronger influence the effects of broad scale and stochastic heterogeneity are compared for a model built from a slice through a tomographic model derived from delay time inversion for the himalayan region as would be expected the influence of the deterministic heterogeneity derived from the tomography study has the result of introducing systematic traveltime variations for body waves and noticeable phase shifts for surface waves when compared with the results for the background reference model the addition of a moderate level of small scale stochastic heterogeneity which could not be resolved in the tomography study has a limited effect on the seismic wavefield at longer periods but is much more significant for periods of less than 4 s when the heterogeneity scale is of the order of 40 km

joint earthquake source inversions using seismo geodesy and 3 d earth models a joint earthquake source inversion technique is presented that uses insar and long period teleseismic data and for the first time takes 3 d earth structure into account when modelling seismic surface and body waves ten average source parameters moment latitude longitude depth strike dip rake length width and slip are estimated hence the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets unwrapped interferograms and long period seismic data are jointly inverted for the location fault geometry and seismic moment using a hybrid downhill powell monte carlo algorithm while the insar data are modelled assuming a rectangular dislocation in a homogeneous halfspace seismic data are modelled using the spectral element method for a 3 d earth model the effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude mw 6 0 6 6 synthetic tests highlight the improvement in the constraint of fault geometry strike dip and rake and moment when insar and seismic data are combined tests comparing the effect of using a 1 d or 3 d earth model show that long period surface waves are more sensitive than long period body waves to the change in earth model incorrect source parameters particularly incorrect fault dip angles can compensate for systematic errors in the assumed earth structure leading to an acceptable data fit despite large discrepancies in source parameters three real earthquakes are also investigated eureka valley california 1993 may 17 mw 6 0 aiquile bolivia 1998 february 22 mw 6 6 and zarand iran 2005 may 22 mw 6 5 these events are located in different tectonic environments and show large discrepancies between insar and seismically determined source models despite the 40 50 km discrepancies in location between previous geodetic and seismic estimates for the eureka valley and aiquile earthquakes the seismic data are found to be compatible with the insar location a 30 difference in strike between insar and seismic derived source models is also resolved when taking 3 d earth structure into account in the analysis of the eureka valley earthquake the combination of both insar and seismic data further constrains the dip for the zarand earthquake and in all cases the seismic moment is more robustly constrained in the joint inversions than in the individual data set inversions unmodelled lateral heterogeneities in earth and the models could partly explain some of the observed source parameter discrepancies related to the seismic data the authors 2014 published by oxford university press on behalf of the royal astronomical society

on regional s the character of regional s wave trains is quite complex and consists of two major elements sn waves which principally travel in the upper mantle and lg waves guided in the earth s crust the effect of lateral heterogeneity is to modify the signals for these phases compared with the predictions for horizontally stratified models however complete synthetic seismogram calculations for simple stratified crustal models for a suite of distances out to 950 km including both sn and lg provide a range of insights into the nature of the s wave train in particular late picks of sn arrivals are likely to arise because the actual s onset has been missed in the p coda and a higher amplitude surface multiple phase with an extra crustal delay has been picked instead such a effect was first recognized by lapwood 1955 in a study of the iss readings for a sequence of japanese events recorded at regional distances but has usually not been taken into consideration in studies using regional networks lateral heterogeneity along the propagation path has the effect of inducing interconversion between sn and lg energy and thus alters the character of the s wave train the lower attenuation for s in the uppermost mantle compared with the crust frequently leaves sn as the most prominent phase at ranges greater than 1000 km long range propagation of high frequency lg requires a relatively undisturbed crust

the velocity structure and heterogeneity of the upper mantle abstract in a particular region a smoothed and averaged representation of the velocity structure in the upper mantle can be derived from long period body wave and higher mode surface wave observations the vertical resolving power of such techniques is limited by the relatively long wavelengths used in contrast short period studies show considerable complexities in postulated one dimensional models which are unresolvable in the long period band however these may be associated with the mapping of lateral heterogeneity into a vertical profile to assess the extent to which lateral heterogeneity in the mantle can be resolved we have attempted to model the features seen on recordings of earthquakes in the indonesia new guinea region at large aperture 400 1000 km arrays of portable seismic recorders with horizontal heterogeneity scales of the order of 300 500 km and velocity perturbations up to 2 the amplitude deviations from those predicted for a stratified model can be considerable and fit in well with the pattern of observations for long period waves such laterally heterogeneous structures have only a modest effect with weak inter mode coupling resulting from the heterogeneity as a result a one dimensional model may still be a useful approximation for long period studies but will not be adequate for broad band or short period work

seismic wavefield calculation for laterally heterogeneous whole earth models using the pseudospectral method summary a method for simulating seismic wave propagation in a laterally heterogeneous whole earth model is presented by solving the elastodynamic equations in 2 d cylindrical coordinates using the pseudospectral method psm the psm is an attractive timedomain technique that uses the fast fourier transform for an accurate diierentiation of eld variables in the equations since no dispersion error arises in fourier diierentiation even when using a large grid spacing computer memoryand time are reduced by several orders of magnitude compared to traditional nite diierence methods in order to examine body wave phases with current computing resources a slice through the sphere is approximated with a 2 d cylindrical model an irregular grid spacing is used in the vertical coordinate to improve the treatment of the various structural boundaries appearing in the earth model by matching the heterogeneity in the model synthetic seismograms obtained by the psm calculation are compared with those calculated from an exact simulation method for a spherically homogeneous 1 d earth model and achieve good agreement the psm method is illustrated by constructing the seismic p sv wave eld for strongly heterogeneous earth models including a shield structure near the free surface and velocity perturbations just above the core mantle boundary the visualization of the evolution of seismic p and s waves in time and space is tracked using a sequence of snapshots and synthetic seismograms these displays allow direct insight into the nature of the complex seismic wave behaviour in the earth s interior

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

modeling tracer transport at the made site the importance of heterogeneity 1 we examine three stochastic transport models of the macrodispersion experiment made site using high resolution conductivity fields derived from a new geostatistical interpretation of the flowmeter data evaluation of the spatial continuity of the hydraulic conductivity data revealed a hole effect structure indicating the occurrence of periodic structures i e clustered lenses or facies alternatively we examine geostatistical models based on indicator variables and found a similarity to bivariate gaussian properties tritium transport was simulated in kriged fields and in random fields generated using different geostatistical models at a grid spacing equal to the vertical support scale of the flowmeter measurements to explicitly represent small scale heterogeneity only those simulations obtained using the hole effect model resulted in a subset of realizations which reproduced the strong anomalous tracer spreading neglecting the hole effect structure of the spatial model in the gaussian simulations resulted in a reduced tailing of the tracer illustrating the importance of preferential flow on anomalous solute transport at the columbus aquifer furthermore we found that a multivariate gaussian random function is adequate to model the spatial distribution of hydraulic conductivity at the made site based on the results of the indicator transport simulations and the univariate and bivariate normality detected in the analysis of the flowmeter data we conclude that when small scale variability of hydraulic conductivity is correctly modeled at the flowmeter measurement support scale the ade is capable of reproducing the tracer spreading results suggest that the main contributor to the operational memory function used in previous successful mass transfer models is mostly a reflection of the suppressed spatial variation of hydraulic conductivity at the model scale

on the formation of breakthrough curves tailing during convergent flow tracer tests in three dimensional heterogeneous aquifers 1 anomalous transport in advection dominated convergent flow tracer tests can occurs due to small scale heterogeneities in aquifer hydraulic properties these result in fluctuations of the groundwater velocity field and complex connectivity patterns between injection and extraction wells while detailed characterization of heterogeneity is often not possible in practice a proper understanding of what fundamental physical mechanisms can give rise to macroscopic behaviors that are measurable is essential for proper upscaling of solute transport processes we analyze here how heavy tailed breakthrough curves can arise in radially convergent flow to a well the permeability fields are three dimensional multi gaussian fields with varying statistical geometry and degrees of heterogeneity we consider transport of conservative tracers from multiple injection locations by varying distance and angle from the extraction well anomalous power law tailing in breakthrough curves is attributed to a variety of features including the initial vertical stratification of the solute that arises due to a flux weighted injection the injection distance to the well relative to the depth of the aquifer and the statistics of the heterogeneity field as defined by the correlation length and variance of the permeability when certain conditions cooccur for a given injection such as strong connectivity contrasts between aquifer layers injection distances comparable to the horizontal heterogeneity integral scales and large global variances breakthrough curves tend to scale as a pl with unit slope at late time these findings offer new insights to understand what physical processes must be understood to develop and choose appropriate upscaling approaches that might reproduce such anomalous transport in heterogeneous advection dominated systems

evolution of sealing efficiency for co2 geological storage due to mineral alteration within a hydrogeologically heterogeneous caprock in co2 geological storage cgs context the evolution of the caprock sealing capacity has received increasing attention particularly on a geological time span thousands of years at this time scale geochemical reactions may enhance or weaken the caprock quality it is widely recognized that for the reservoir geological heterogeneities affect the concentration and spatial distribution of co2 and then affect the extent of gas water rock interactions which in turn alters the hydrogeological properties of the reservoir however much less attention of these effects has been paid to the caprock in this study we presented and applied a novel approach to evaluate the effects of permeability and porosity heterogeneities on the alteration of minerals the associated evolution of the caprock sealing efficiency and the containment of supercritical co2 scco2 within the caprock even though this is a generic study several conditions and parameters such as pressure permeability and mineral composition were extracted from a caprock layer of the shiqianfeng formation in the ordos basin demonstration site in china for the sake of simplification a 2 dimensional model was designed to represent the caprock domain we firstly generated an appropriate heterogeneous random field of permeability with the average permeability taken from the uppermost mudstone layer of the shiqianfeng formation and then the heterogeneity in porosity was incorporated using a joint normal distribution method based on the available data homogeneous mineral compositions of the reservoir and caprock were used in all simulations simulations of three cases were performed including a homogeneous case a case with only permeability heterogeneity and a case with both permeability and porosity heterogeneities the results demonstrate dramatic influences of permeability and porosity heterogeneities on the migration of scco2 within the caprock the alteration of minerals and therefore the evolution of the caprock sealing quality specific to the data used in this study hydrogeological heterogeneities facilitated the overall penetration of scco2 within the caprock and promoted the alteration of minerals thereby weakening the caprock sealing efficiency over the simulation time

super diffusion affected by hydrofacies mean length and source geometry in alluvial settings dissolved phase contaminants experiencing enhanced diffusion i e super diffusion with a pronounced leading plume edge can pose risk for groundwater quality the drivers for complex super diffusion in geological media however are not fully understood this study investigates the impacts of hydrofacies mean lengths and the initial source geometry motivated by a hydrofacies model built recently for the well known made aquifer on the spatial pattern of super diffusion for two dimensional alluvial aquifer systems monte carlo simulations show that the bimodal velocity distribution whose pattern is affected by the hydrofacies mean lengths leads to super diffusion of solutes with a bi peak plume snapshot in alluvial settings where advection dominates transport a larger longitudinal mean length i e width for hydrofacies with high hydraulic conductivity k enhances the connectivity of preferential pathways resulting in higher values in the bimodal velocity distribution and an enhanced leading front for the bi peak plume snapshot while the opposite impact is identified for the hydrofacies vertical mean length i e thickness on the bi peak super diffusion a multi domain non local transport model is then proposed extending upon the concept of the distributed order fractional derivative to quantify the evolution of bi peak super diffusion due to differential advection and mobile mobile mass exchange for solute particles moving in hydrofacies with distinct k results show that the bi peak super diffusion identified for the made site and perhaps the other similar aquifers which is affected by the initial source geometry at an early stage and the thickness and width of high k hydrofacies during all stages can be quantified by the mobile mobile fractional derivative model porous medium dimensionality and stochastic model comparison are also discussed to further explore the nature of bi peak super diffusion in alluvial systems

joint seismic tomography for bulk sound and shear wave speed in the earth s mantle high quality p and s travel times are now available from careful reprocessing of data reported to international agencies a restricted data set has been extracted for which comparable ray coverage is achieved for p and s and used for a joint inversion to produce a three dimensional model for shear and bulk sound velocities represented in terms of 2 2 cells and 18 layers in depth through the mantle about 106 times for each of p and s are combined to produce 312 549 summary rays for each wave type linearizing about the ak135 reference model 583 200 coupled tomographic equations are solved using an iterative partitioned scheme clear high resolution images are obtained for both bulk sound speed and shear wavespeed the bulk and shear moduli have differing sensitivity to temperature and mineral composition and so the images of the two velocity distributions help to constrain the nature of the processes which produce the variations different heterogeneity regimes can be recognised in the upper mantle the transition zone most of the lower mantle and the lowermost mantle in the upper mantle many features can be explained by thermal effects but in some orogenic zones e g western north america the opposite sense of the bulk sound and shear wave speed variation requires compositional effects or volatiles to outweigh any thermal effects in the lower mantle pronounced narrow structures which may represent remnant subduction are most marked in shear the level of large scale variations in bulk sound speed compared to shear diminishes with depth in the lower mantle reaching a minimum near 2000 km below this depth the variability of both wave speeds increases near the core mantle boundary the variations of the two wave speeds show little concordance suggesting the presence of widespread chemical heterogeneity

geological modeling of submeter scale heterogeneity and its influence on tracer transport in a fluvial aquifer 1 we developed a new model of aquifer heterogeneity to analyze data from a single well injection withdrawal tracer test conducted at the macrodispersion experiment made site on the columbus air force base in mississippi usa the physical heterogeneity model is a hybrid that combines 3 d lithofacies to represent submeter scale highly connected channels within a background matrix based on a correlated multivariate gaussian hydraulic conductivity field the modeled aquifer architecture is informed by a variety of field data including geologic core sampling geostatistical properties of this hybrid heterogeneity model are consistent with the statistics of the hydraulic conductivity data set based on extensive borehole flowmeter testing at the made site the representation of detailed small scale geologic heterogeneity allows for explicit simulation of local preferential flow and slow advection processes that explain the complex tracer response from the injection withdrawal test based on the new heterogeneity model advective dispersive transport reproduces key characteristics of the observed tracer recovery curve including a delayed concentration peak and a low concentration tail importantly our results suggest that intrafacies heterogeneity is responsible for local scale mass transfer

field study of dispersion in a heterogeneous aquifer 4 investigation of adsorption and sampling bias the declining mass balance trend observed for bromide and three fluorobenzoate tracers during a natural gradient experiment at a site near columbus mississippi prompted investigations related to the reactivity of the tracers and the representativeness of the tracer samples obtained from multilevel samplers a laboratory soil column study indicated that adsorption of bromide during the field experiment was of the order of 20 and that up to 10 of the three fluorobenzoates was adsorbed the presence of iron oxides and kaolinite in the alluvial aquifer combined with the low groundwater ph of 4 8 produced geochemical conditions conducive to adsorption of the anionic tracers multilevel samplers mls used in the field experiment were evaluated by comparing bromide concentrations from the mls with water samples extracted from adjacent soil cores vertically averaged bromide concentrations for the mls were 21 lower than those for the cores a matrix diffusion process in conjunction with a natural tendency for preferential sampling from permeable regions in the heterogeneous alluvial sediments is proposed as an explanation for the apparent bias in the mls sample concentrations this process is shown to be qualitatively consistent with the tracer mass balance observed during the natural gradient experiment 14 refs 11more figs 8 tabs less

multiscale solute transport upscaling for a three dimensional hierarchical porous medium a laboratory generated hierarchical fully heterogeneous aquifer model fhm provides a reference for developing and testing an upscaling approach that integrates large scale connectivity mapping with flow and transport modeling based on the fhm three hydrostratigraphic models hsms that capture lithological static connectivity at different resolutions are created each corresponding to a sedimentary hierarchy under increasing system lnk variances 0 1 1 0 4 5 flow upscaling is first conducted to calculate equivalent hydraulic conductivity for individual connectivity or unit of the hsms given the computed flow fields an instantaneous conservative tracer test is simulated by all models for the hsms two upscaling formulations are tested based on the advection dispersion equation ade implementing space versus time dependent macrodispersivity comparing flow and transport predictions of the hsms against those of the reference model hsms capturing connectivity at increasing resolutions are more accurate although upscaling errors increase with system variance results suggest 1 by explicitly modeling connectivity an enhanced degree of freedom in representing dispersion can improve the ade based upscaled models by capturing non fickian transport of the fhm 2 when connectivity is sufficiently resolved the type of data conditioning used to model transport becomes less critical data conditioning however is influenced by the prediction goal 3 when aquifer is weakly to moderately heterogeneous the upscaled models adequately capture the transport simulation of the fhm despite the existence of hierarchical heterogeneity at smaller scales when aquifer is strongly heterogeneous the upscaled models become less accurate because lithological connectivity cannot adequately capture preferential flows 4 three dimensional transport connectivities of the hierarchical aquifer differ quantitatively from those analyzed for two dimensional systems

a pseudo genetic model of coarse braided river deposits a new method is proposed to produce three dimensional facies models of braided river aquifers based on analog data the algorithm consists of two steps the first step involves building the main geological units the production of the principal inner structures of the aquifer is achieved by stacking multiple point statistics simulations of successive topographies thus mimicking the major successive flooding events responsible for the erosion and deposition of sediments the second step of the algorithm consists of generating fine scale heterogeneity within the main geological units these smaller scale structures are generated by mimicking the trough filling process occurring in braided rivers the imitation of the physical processes relies on the local topography and on a local approximation of the flow this produces realistic cross stratified sediments comparable to what can be observed in outcrops the three main input parameters of the algorithm offer control over the proportions the continuity and the dimensions of the deposits calibration of these parameters does not require invasive field measurements and can rely partly on analog data

sedimentology and hydrogeology of two braided stream deposits abstract two approaches were used to quantify the spatial distribution of hydrofacies in braided stream deposits one approach involved mapping a 50 by 60 by 3 3 m section of a proximal braided stream deposit in a second study we generated a 400 by 400 by 2 6 m section of a medial braided stream deposit using a computer model in both cases we produced three dimensional images showing connected hydrofacies with high permeabilities that form preferential flow paths this information was input to a groundwater flow model and flow paths were analyzed by following the transport of imaginary particles in both systems particles that were uniformly distributed at the up gradient end of the model clustered along preferential flow paths during transport showing that connection among high permeability facies is a critical factor in hydrogeological investigations involving assessment of contaminant movement and remediation

finite difference simulations of seismic scattering implications for the propagation of short period seismic waves in the crust and models of crustal heterogeneity synthetic seismograms produced by the finite difference method are used to study the scattering of elastic and acoustic waves in two dimensional media with random spatial variations in seismic velocity the results of this study provide important insights about the propagation of short period 5 the self similar medium is characterized by a scattering q that is constant with frequency whereas theory predicts that the apparent q in an exponential medium is proportional to frequency these alternative models of crustal heterogeneity can thus be tested by improved measurements of the frequency dependence of crustal q at frequencies greater than about 1 hz assuming that scattering is responsible for most of the attenuation at these frequencies measurements of the time decay of the synthetic coda waves clearly show that the single scattering model of coda decay is not appropriate in the presence of moderate amounts of scattering attenuation scattering q 200 in these cases q values derived from the coda decay rate using the single scattering theory do not correspond to the transmission q of the medium the cross correlation of synthetic waveforms observed for an array of receivers along the free surface is observed to be dependent on the correlation distance of the medium the self similar random medium proposed here for the crust produces waveform variations at high frequencies 15 30 hz similar to those reported for actual small scale seismic arrays with apertures of hundreds of meters

shear wave velocity variations in the upper mantle beneath central europe summary a new model eur s91 of shear wave velocity variations in the upper mantle beneath central europe and surrounding regions down to a depth of 670km is presented the model is derived from the inversion of the waveforms of 217 seismograms using the partitioned waveform inversion method for the seismogram in the time window from the s wave arrival to the fundamental mode of the rayleigh wave the seismograms were mostly assembled from digitally recording long period and broad band stations in europe the resulting 3 d model accurately predicts most of the observed waveforms in a wide band of frequencies body waves were fit for frequencies up to 60mhz the fundamental rayleigh mode which at high frequencies is more prone to scattering and multipathing was generally low passed at 25 mhz the resolving power of the data set depends strongly on the density of available wave paths and varies as a function of geographical position small scale heterogeneities like the subducted lithosphere in the hellenic collision zone were imaged in the region with the highest density of wave paths which indicates an optimum resolution of better than 200 km the main new results of this study pertain to the transition between east and central europe we present new information about the structure below the tornquist teisseyre zone ttz the ttz is generally regarded as the boundary between the precambrian crust of the baltic shield russian platform and the younger crust of central europe our 3 d s velocity model reveals that below this line a sharp lateral boundary extends down to at least 140 km depth with high velocities beneath the baltic shield and russian platform contrasting to the low velocities beneath the younger regions of europe the observed velocity contrast across the ttz is largest between the pannonian basin and the russian platform where it is equal to 12 per cent at 80 km depth at depths of 300 400 km the ttz is underlain by a zone of low s velocity which indicates a local thinning of the deeply rooted high velocity structure or tectosphere that underlies most of eastern europe in addition to these new results on the transition region between east and central europe a number of features that are present in other tomographic results have been confirmed the precambrian provinces of europe are characterized by high s velocities low velocities are found beneath the pannonian basin the western mediterranean northern aegean sea turkey and a small region south west of the massif central the lithosphere beneath the paris basin has a positive s velocity anomaly the resolution of all these anomalies has been established with sensitivity tests

tomogram based comparison of geostatistical models application to the macrodispersion experiment made site we propose a new framework to compare alternative geostatistical descriptions of a given site multiple realizations of each of the considered geostatistical models and their corresponding tomograms based on inversion of noise contaminated simulated data are used as a multivariate training image the training image is scanned with a direct sampling algorithm to obtain conditional realizations of hydraulic conductivity that are not only in agreement with the geostatistical model but also honor the spatially varying resolution of the site specific tomogram model comparison is based on the quality of the simulated geophysical data from the ensemble of conditional realizations the tomogram in this study is obtained by inversion of cross hole ground penetrating radar gpr first arrival travel time data acquired at the macro dispersion experiment made site in mississippi usa various heterogeneity descriptions ranging from multi gaussian fields to fields with complex multiple point statistics inferred from outcrops are considered under the assumption that the relationship between porosity and hydraulic conductivity inferred from local measurements is valid we find that conditioned multi gaussian realizations and derivatives thereof can explain the crosshole geophysical data a training image based on an aquifer analog from germany was found to be in better agreement with the geophysical data than the one based on the local outcrop which appears to under represent high hydraulic conductivity zones these findings are only based on the information content in a single resolution limited tomogram and extending the analysis to tracer or higher resolution surface gpr data might lead to different conclusions e g that discrete facies boundaries are necessary our framework makes it possible to identify inadequate geostatistical models and petrophysical relationships effectively narrowing the space of possible heterogeneity representations

aspherical earth structure from fundamental spheroidal mode data free oscillation data reveal heterogeneity in the earth s mantle whose geographical pattern is dominated by spherical harmonics of angular degree two and correlates well with the hydrostatically referenced geoid the heterogeneity can be modelled as localized in the transition zone 420 670 km depth and may be related to a large scale component of mantle convection

spatial connectivity in a highly heterogeneous aquifer from cores to preferential flow paths 1 this study investigates connectivity in a small portion of the extremely heterogeneous aquifer at the macrodispersion experiment made site in columbus mississippi a total of 19 fully penetrating soil cores were collected from a rectangular grid of 4 m by 4 m detailed grain size analysis was performed on 5 cm segments of each core yielding 1740 hydraulic conductivity k estimates three different geostatistical simulation methods were used to generate 3 d conditional realizations of the k field for the sampled block particle tracking calculations showed that the fastest particles as represented by the first 5 to arrive converge along preferential flow paths and exit the model domain within preferred areas these 5 fastest flow paths accounted for about 40 of the flow the distribution of preferential flow paths and particle exit locations is clearly influenced by the occurrence of clusters formed by interconnected cells with k equal to or greater than the 0 9 decile of the data distribution 10 of the volume the fraction of particle paths within the high k clusters ranges from 43 to 69 in variogram based k fields some of the fastest paths are through media with lower k values suggesting that transport connectivity may not require fully connected zones of relatively homogenous k the high degree of flow and transport connectivity was confirmed by the values of two groups of connectivity indicators in particular the ratio between effective and geometric mean k on average about 2 and the ratio between the average arrival time and the arrival time of the fastest particles on average about 9 are consistent with flow and advective transport behavior characterized by channeling along preferential flow paths

broad band trajectory mechanics author s vasco dw nihei k abstract 2019 published by oxford university press on behalf of the royal astronomical society we present a trajectory based solution to the elastodynamic equation of motion that is valid across a wide range of seismic frequencies that is the derivation of the solution does not invoke a high frequency assumption or require that the medium have smoothly varying properties the approach adopted from techniques used in quantum dynamics produces a set of coupled ordinary differential equations for the trajectory the slowness vector and the elastic wave amplitude along the ray path the trajectories may be determined by a direct solution of the governing equations or derived as the by product of a numerical wavefield simulation synthetic tests with interfaces and layers containing increasingly narrow transition zones indicate that the conventional high frequency trajectories associated with the eikonal equation bend too sharply into high velocity regions as the wavelength exceeds the transition zone width tests in a velocity model based upon mapped structural surfaces from the geysers geothermal field in california indicate that discrepancies between high frequency and broad band trajectories can exceed several hundred metres at wavelengths of 1 hz an application to a crosswell tomographic imaging experiment demonstrates that the technique provides a basis for the seismic monitoring of fluid flow along narrow features such as fracture zones

modeling heterogeneity of gravel sand braided stream alluvial aquifers at the facies scale abstract the coarse grained alluvial aquifers are recurrently considered as almost homogeneous and isotropic media nevertheless water flow through these sediments is controlled by internal architecture therefore a better knowledge is necessary to understand the effects of facies heterogeneity on the conductivity magnitude and anisotropy within these aquifers in this work we search interactions at the facies scale within a glacio fluvial aquifer among sedimentary heterogeneity distribution of permeability and anisotropy the case study concerns pleistocene sequences of the ticino basin northern italy where three model blocks dug into real sediments at a quarry site have been investigated at the meter scale these model blocks represent the most diffuse facies associations 1 sand gravel dunes 2 gravel bedforms and 3 poorly sorted mass gravity deposits facies maps with 2 cm resolution were obtained for each block and used to condition 3d geostatistical simulation of the sediment volumes with a hierarchical modification of sisim conductivities of samples were either measured with laboratory tests or estimated with empirical formulas conductivity values were finally introduced as input data into the numerical flow model to compute the upscaled tensor of equivalent conductivity at the model block scale the results of field infiltration tests were used to verify the outcomes of upscaling experiments which identified the primary influence on the most permeable facies open framework gravel on both conductivity magnitude and anisotropy ratio the latter property is unrelated to the abundance of this facies but is controlled by its spatial distribution within the blocks as the connectivity of open framework gravel increases model blocks become more anisotropic on the other hand the low permeable sand facies of dunes do not produce significant anisotropy at the block scale these results show the importance of introducing the hierarchical assemblage of different rank depositional units in conceptual aquifer models in addition we identified the most significant depositional units to forecast the spatial distribution of aquifer heterogeneity at different scales

a tomographic image of mantle structure beneath southern california we determined the variations in seismic structure beneath southern california by using a tomographic method of inversion on teleseismic p delays recorded with the southern california array the algorithm employed was a modified form of an algebraic reconstruction technique art used in medical x ray imaging deconvolution with an empirically estimated point spread function was also used to help in focusing the image the inversion reveals two prominent features beneath the region the first is a thin vertical wedge directly beneath the transverse ranges that is 2 3 faster than the surrounding region this feature deepens to the east attaining a maximum depth of about 250 km beneath the san bernardino mountains the second feature is a major zone of low velocity material that is 2 4 slow under the salton trough rift valley extending to a depth of about 125 km two possible explanations for the spatial association of the transverse ranges with the velocity anomaly below are lithospheric subduction or small scale sublithospheric convection in the region of the big bend of the san andreas fault the low velocity anomaly beneath the salton trough is consistent with convective upwelling there

inner core boundary topography explored with reflected and diffracted p waves abstract the existence of topography of the inner core boundary icb can affect the amplitude phase and coda of body waves incident on the inner core by applying pseudospectral and boundary element methods to synthesize compressional waves interacting with the icb these effects are predicted and compared with waveform observations in pre critical critical post critical and diffraction ranges of the pkikp wave reflected from the icb these data sample overlapping regions of the inner core beneath the circum pacific belt and the eurasian north american and australian continents but exclude large areas beneath the pacific and indian oceans and the poles in the pre critical range pkikp waveforms require an upper bound of 2 km at 1 20 km wavelength for any icb topography higher topography sharply reduces pkikp amplitude and produces time extended coda not observed in pkikp waveforms the existence of topography of this scale smooths over minima and zeros in the pre critical icb reflection coefficient predicted from standard earth models in the range surrounding critical incidence 108 130 this upper bound of topography does not strongly affect the amplitude and waveform behavior of pkikp pkikp at 1 5 hz which is relatively insensitive to 10 20 km wavelength topography height approaching 5 km these data however have a strong overlap in the regions of the icb sampled by pre critical pkikp that require a 2 km upper bound to topography height in the diffracted range 152 topography as high as 5 km attenuates the peak amplitudes of pkikp and pkpcdiff by similar amounts leaving the pkpcdiff pkikp amplitude ratio unchanged from that predicted by a smooth icb the observed decay of pkpcdiff into the inner core shadow and the pkikp pkpcdiff differential travel time are consistent with a flattening of the outer core p velocity gradient near the icb and iron enrichment at the bottom of the outer core

travel times and station corrections for p waves at teleseismic distances approximately 3300 shallow focus earthquakes and 1000 seismic stations have been used in a study of p wave travel times and station residuals including azimuthal effects the events were selected from a catalog containing 160 000 earthquakes and those having uniform distance and azimuthal coverage were systematically relocated and used to refine p wave travel times and station corrections station corrections are provided for 994 seismic stations the station corrections involve three terms the static effect and two cosine terms with appropriate phase shifts they exhibit general consistency over broad geographic areas and where coverage is dense often show abrupt changes from one geological province to another the cos 2 terms appear to be due to upper mantle anisotropy and they correlate with the stress direction in the crust

a comparative study of three dimensional hydraulic conductivity upscaling at the macro dispersion experiment made site columbus air force base mississippi usa simple averaging simple laplacian laplacian with skin and non uniform coarsening are the techniques investigated in this comparative study of three dimensional hydraulic conductivity upscaling the reference is a fine scale conditional realization of the hydraulic conductivities at the macro dispersion experiment site on columbus air force base in mississippi usa this realization was generated using a hole effect variogram model and it was shown that flow and transport modeling in this realization at this scale can reproduce the observed non fickian spreading of the tritium plume the purpose of this work is twofold first to compare the effectiveness of different upscaling techniques in yielding upscaled models able to reproduce the observed transport behavior and second to demonstrate and analyze the conditions under which flow upscaling can provide a coarse model in which the standard advection dispersion equation can be used to model transport in seemingly non fickian scenarios specifically the use of laplacian based upscaling technique coupled with a non uniform coarsening scheme yields the best results both in terms of flow and transport reproduction for this case study in which the coarse blocks are smaller than the correlation ranges of the fine scale conductivities

influences of depositional environment and diagenesis on geophysical log response in the south carolina coastal plain effects of sedimentary fabric and mineralogy abstract interpretations of depositional environments and hydrologic units are made routinely from the study of geophysical well logs spontaneous potential sp and resistivity logs can be used as indicators of textural parameters gamma ray logs denote lithologic zones based on the presence of radioactive material particularly in fine grained sediments on the south carolina coastal plain surficial fluvially derived cobbles sands and clays are characterized by very low radioactivity weathered paleosurfaces enriched in hydroxy interlayered vermiculite hiv and associated mica produce higher gamma ray responses at discrete intervals the underlying sequence of siliciclastic shelf sands deposited under conditions of eustatic sea level rise has high concentrations of smectite and low gamma ray signatures small scale variability of gamma radiation reflects temporal changes of sub environments higher values are recorded in finer grained organic rich nearshore sediments calcareous ecocene sediments are characterized by highly variable signals on the gamma ray sp and resistivity logs phospharic material smectite and disseminated organic matter produced very high gamma ray values corresponding low sp readings are a function of low macro to microscale porosity resulting from the fine grain size and authigenic pore filling cement intervals that resemble massively bedded chalks at the macroscale are characterized by low gamma ray and resistivity values and high sp readings high sp values result from microposity preserved in biogenic tests rather than intergranular porosity that would be expected for a permeable sand these observations indicate the importance of incorporating sedimentologic techniques with well log data for a comprehensive evaluation of subsurface lithologic units

robust inversion of iasp91 travel time residuals for mantle p and s velocity structure earthquake mislocations and station corrections using both p and s arrival time information 41 108 events in the international seismological centre isc catalog for the years 1964 to 1987 are relocated relative to the iasp91 velocity model the mean absolute horizontal relocation is 7 7 km and the mean absolute depth relocation is 9 1 km the mean absolute origin time shift is 1 2 s the relocation procedure increased the p residual standard deviation slightly from 2 3 s to 2 5 s while decreasing the s residual standard deviation from 6 8 s to 6 1 s when plotted as bottoming point averages the resulting iasp91 p and s arrival time residuals show coherent patterns as a function of geographic location an iterative lp residual norm minimization algorithm is used to estimate the set of p and s velocity variations as well as the earthquake relocation and seismographic station parameters which best explain the travel time residuals the procedure is robust in that extremely large travel time residuals which are common in the isc data do not unduly influence the velocity estimates both the p and s models of lateral heterogeneity contain prominent circum pacific low velocities 1 to 2 perturbations underlying the back arc basins between 35 and 200 km depth this ring of negative deviations continues into the depth interval 200 400 km the continental cratons are underlain by high velocity anomalies with maximum amplitudes of 2 iceland and the azores are underlain by low velocity mantle material that extends down to at least 400 km the benioff zones are only intermittently imaged as 1 2 high velocity regions in the uppermost 400 km they are best resolved in the p velocity variations both the p and s velocity models contain a circum pacific ring beneath the benioff zones of 1 2 positive velocity deviations in the depth range 660 870 km coherent high velocity features are seen below south america borneo tonga fiji the marianas and the northern kuriles the anomalies beneath south america and borneo extend into the 870 1070 km depth range below depths of 1270 km for p variations and 1070 km for s variations the amplitude of the heterogeneity has decreased significantly it is only in the lowermost mantle 2670 km to the core mantle boundary that the level of p heterogeneity rises significantly above the estimated noise level in this depth range a partial ring around the pacific basin is observed although this

3 dimensional structure of the indian ocean inferred from long period surface waves to improve the lateral resolution of the first global 3 dimensional models of seismic wave velocities regional studies have to be undertaken the dispersion of rayleigh waves along 86 paths across the indian ocean and surrounding regions is investigated in the period range 40 300 s the regionalization of group velocity according to the age of the sea floor shows an increase of velocity with age up to 150 s only similar to the results in the pacific ocean but here this relationship vanishes more quickly at long period therefore the correlation of the deep structure with surface tectonics seems to be shallower in the indian ocean than in the pacific ocean a tomographic method is applied to compute the geographical distributions of group velocity and azimuthal anisotropy and then the 3 d structure of s wave velocity horizontal wavelengths of 2000 km for velocity and 3000 km for azimuthal anisotropy distribution can be resolved except for the central part of the south east indian ridge which displays high velocities at all depths the inversion corroborates a good correlation between lithospheric structure down to 120 km and surface tectonics low velocities along the central and southeast indian ridges velocity increasing with the age of the sea floor high velocities under african indian and australian shields at greater depths the low velocity zones under the gulf of aden and the western part of the southeast indian ridges hold but the low velocity anomaly of the central indian ridge is offset eastward the low velocity anomalies suggest uprising material and complex plate boundary

whole mantle p wave travel time tomography abstract a method of tomographic inversion to obtain three dimensional velocity perturbations in the earth s whole mantle has been developed and applied to more than two million p wave arrival time data reported by international seismology center isc the model is parameterized with 32 768 blocks the divisions in latitude longitude and radius are 32 64 and 16 respectively horizontal cell size is 5 6 5 6 the layer thicknesses vary with depth 29 km just below the surface and 334 km just above the core mantle boundary starting from a spherically symmetric earth model we obtained a three dimensional model using the following iterative procedures first we relocated all the events second we backprojected the residual into the whole mantle third we refined the spherically symmetric earth model the solutions have been converged in five iterations we adopted the following techniques in the backprojection procedure the first order smoothness was introduced as a damping which makes the solution independent of the starting model and its apparent fluctuation minimal the basic equations for delay times and smoothness are solved using the conjugate gradient method an iterative method which guarantees the convergence of solution into the exact least squares solution the weight on the smoothness i e the damping factor was objectively determined by a simplified cross validation technique the final solution was obtained as an average of the ten solutions each of which was derived from one tenth of the total data set the reliability of the solution is examined in two ways 1 mapping the resolution given by the reconstruction of checkerboard patterns and 2 mapping the variance given from the gaussian noise input this is the first result which delineates the whole mantle structure with its reliability mapping the longest wavelength anomalies of the lower mantle are similar to those of previous studies by dziewonski 1984 and hager and clayton 1989 however the shorter wavelength patterns have many discrepancies the fast anomalies of the uppermost mantle beneath the shield and the slow anomalies beneath the active tectonic regions are clearly seen we also revealed the l 2 pattern at the transition zone reported by the previous surface wave and free oscillation studies the most striking feature is that of the fast anomalies lying along the extension of the large subducting plate up to depths of about 1000 km or more the resolving powers in these regions are generally good

reply to comment by f molz et al on investigating the macrodispersion experiment made site in columbus mississippi using a three dimensional inverse flow and transport model

tomographic inversions for mantle p wave velocity structure based on the minimization of l 2 and l 1 norms of international seismological centre travel time residuals we use international seismological centre isc p arrival data 1964 1987 and iterative algorithms which minimize the l1 and l2 residual norms to solve simultaneously for three dimensional p velocity variations in earth s mantle source mislocations and station corrections we find that the maximum velocity perturbations produced by the l1 minimization approximately 4 in our final model are relatively insensitive to smoothing and damping constraints therefore using an l1 norm criterion allows us to keep the bias introduced to the inversion to a minimum among the well resolved features contained in both the l1 and the l2 velocity models are a fast anomaly in the lower mantle beneath the tonga new hebrides subduction zone to a depth of 1670 km and another fast anomaly beneath the japanese island arc and eastern asia continuity between these anomalies and shallower fast anomalies is not clear a fast anomaly extending from 670 km to 2070 km depth appears beneath eastern north america the caribbean and north central south america a broad fast anomaly appears beneath eastern asia just above the core mantle boundary as well as several slow anomalies under the pacific basin of comparable size both models contain a circum pacific ring of 2 lower velocities in the depth range 0 200 km associated with back arc basins high velocities over 2 associated with the continental shields tend to disappear below 400 km though a significant region of high velocity remains beneath the siberian platform in the 400 to 670 km depth interval

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

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

impact of upscaling on solute transport traveltimes scale dependence of dispersivity and propagation of uncertainty 1 efficiency constraints in applying numerical models to real problems force the use of a coarse discretization of the domain compared with the detailed scale required for the most adequate description of the system upscaling encompasses the methods that transfer small scale information to the computational scale the loss of small scale information by upscaling aquifer properties to construct a numerical model largely modifies the true heterogeneous structure of the aquifer compromising the final predictions of solute transport we present extensive monte carlo solute transport simulations in heterogeneous porous media to investigate 1 the impact of upscaling on the evolution of solute plumes and 2 the propagation of uncertainty through upscaling in doing this we analyze the benefits of using enhanced block dispersion tensors in the advection dispersion equation to compensate for the loss of information it is shown that upscaling does not affect the median traveltimes of particles reaching a control location but the tail of breakthrough curves is largely underestimated it is also observed that normal upscaled transport models can largely underestimate the spreading of solute plumes even if block dispersivities are calculated as being representative of within block heterogeneity discrepancies are mainly attributed to the mass transfer interaction between grid blocks of the numerical model and the use of a simplistic representation of the block hydraulic conductivity tensor using the small perturbation stochastic approach we found that mass transfer effects are still significant even for block sizes of the numerical model greater than 30 correlation scales moreover upscaling is shown to have a substantial impact on the uncertainty predicted by solute transport models which is not compensated by the use of enhanced block dispersion tensors for very heterogeneous media simulation results showed the inability of the classical advection dispersion equation to simultaneously reproduce the tail of the breakthrough curve and its uncertainty in the upscaled model in those cases results indicated that either a mass transfer model allowing solute mass exchange between high and low conductivity zones encountered within a grid block of the numerical model or the continuous time random walk model expressing the retardation of solute particles passing through low conductivity regions inside a grid block by means of a transition time distribution function might suppose a better upscaled transport model

eocene biostratigraphy of south carolina and its relationship to gulf coastal plain zonations and global changes of coastal onlap an assimilation of mega invertebrate assemblages in south carolina with gulf coast biozones allows for the subdivision of the middle and late eocene into four regional zonations that can be compared with proposed global sequences controlled by eustatic changes of sea level the middle eocene can be divided in ascending stratigraphic order into the cubitostrea perplicata zone c lisbonensis zone and c sellaeformis zone the late eocene is represented by the crassatella alta chlamys cawcawensis zone these zones are separated by type 1 or type 2 unconformities that bracket global sequence boundaries unconformity types after vail and todd 1981 the following sequences are proposed for the middle and upper eocene te2 1 cubitostrea perplicata zone followed by a type 2 unconformity te2 2 c lisbonensis zone followed by a type 2 unconformity te2 3 c sellaeformis zone followed by a type 1 unconformity and te3 crassatella alta chlamys cawcawensis zone followed by a type 2 unconformity although not recognized in the downdip areas of south carolina the te3 sequence can be further subdivided into a te3 1 sequence and te3 2 sequence separated by a type 2 unconformity this regional break lies at the gosport sand lower moodys branch formation upper moodys branch formation contact in the gulf coastal plain and at the base of the tivola tonque in georgia

regional 3 d heterogeneities by waveform inversion application to the atlantic area the waveform inversion method described in woodhouse dziewonski 1984 was modified to retrieve regional scale 3 d heterogeneities by using the minor arc part of seismograms the lateral heterogeneities are expanded horizontally into blocks 10 10 and radially into legendre polynomials up to order 3 0 670 km and thus the results show much fine details of lateral variation than previous global scale studies we assumed that the heterogeneities produce the perturbation of eigenfrequencies which are the minor arc average of local eigenfrequency shift we applied the method to the upper mantle beneath the atlantic ocean and its environments care was taken about the weighting of the data set we found that the fit of each seismogram became better when the weighting of each seismogram is proportional to the inverse of initial data residuals resolution is good in the triangular region surrounded by south america europe and north america resolution is not good in the south atlantic because of the poor path coverage depth resolution is not clear because of the use of legendre polynomials though the results suggest a broad half width of the order of 200 km or more we found some similarities between previous global studies and our results for example low velocities beneath the east pacific rise chile rise and azores triple junction and a high velocity canadian shield are obtained however there are also differences the high velocity zone beneath the brazilian shield at shallow depth is not a prominent feature in this study instead we found a somewhat unexpected feature near the romanche and vema fracture zones where shallow positive anomalies exist smoothed results calculated by the spherical harmonic expansion are also shown for the purpose of comparison with global studies

observational and theoretical constraints on crustal and upper mantle heterogeneity abstract the effects of crustal and mantle heterogeneity are reflected in the relative complexity of short period seismograms at regional to teleseismic distances observations of events at regional ranges from indonesia and new guinea at the warramunga array in northern australia allow a separation of the propagation through the mantle by concentrating on the coherent signal across the medium aperture array most of the incoherent features on the seismograms arise from signal generated noise in the general vicinity of the array with scale lengths of the order of 1 2 km or smaller partially coherent phases with relatively rapid changes in waveform across the array are to be associated with organised heterogeneity this is most likely to arise from features in the crust or at the crust mantle boundary near the receiver but could in some cases be due to structural effects near the source the coherent signals show considerable complexity for phases travelling large portions of their path above 80 km as the depth of sources increases this coherent portion of the seismic field tends to become simpler which suggests that the scale length of heterogeneity is larger at depth the use of horizontally stratified models has provided a convenient framework for the understanding of many seismic wave phenomena via the calculation of synthetic seismograms however further development is needed for calculating the response of the laterally heterogeneous earth the convenience of physical interpretation provided by working with the reflection and transmission properties of the medium can be retained if the structure can be split into a stratified reference model with superimposed heterogeneity with a plane wave decomposition of the wavefield the effect of lateral variations can be introduced by forcing mixing of wavenumber components a wide variety of phenomena can be simulated by varying the statistical description of the heterogeneity field in the wavenumber domain this varies the cross coupling between wavenumber components and so changes the nature of the resulting theoretical seismograms such an approach allows a quantitative study of the degradation of the major seismic phases compared to the predictions for stratified models and also the characterisation of the codas of these phases

how deep can we see the high velocity anomalies beneath the japan islands high velocity anomalies are found in the lower mantle beneath the japan islands and their vicinity through an analysis of detailed three dimensional p wave velocity structure based on a tomographic inversion of isc data beneath the sea of japan the high velocity anomalies in the lower mantle are slab like and appear to extend below the deep focus earthquakes of the high velocity pacific slab descending from the japan trench this slab like high velocity body extending into the lower mantle steepens below a depth of 500 600 km resolution analyses confirms the existence of a slab like high velocity region in the lower mantle though the depth extent is not well resolved on the other hand the pacific slab descending from the izu bonin trench seems to be fingering that is high velocity anomalies are penetrating into the lower mantle beneath latitude 26 n and not penetrating but horizontally bending in the deeper portion of the upper mantle around 29 n

three dimensional velocity map of the upper mantle beneath the pacific ocean as determined from rayleigh wave dispersion abstract a three dimensional shear wave velocity model of the upper mantle beneath the pacific is determined from rayleigh wave phase velocities at periods 60 200 s without any a priori regionalization the results clearly indicate that the velocity distribution in the uppermost 150 km is correlated with the surface tectonics the seismic velocities of the young regions such as the east pacific rise and the west coast of north america are lower than the average pacific structure by 2 5 and those of the old regions such as the northwest pacific are higher by 2 4 as the depth increases the low velocity region in the southeast pacific seems to move to the northwest a wide area of the central pacific shows low velocity below depths of 200 250 km an area off the coast of western canada exhibits a velocity lower by 4 5 above 200 km but changes to a velocity higher by 4 5 below that depth cross sections of the marginal sea regions around the pacific the tasman sea the philippine sea the sea of japan the okhotsk sea and the bering sea have quite different features from each other the bering sea has a velocity lower by 1 2 above 100 km and below 300 km and higher by 1 at depths 150 250 km the philippine sea and the sea of japan have a velocity lower by 1 2 at depths 50 150 km and a velocity higher by 1 2 at depths 200 400 km the bismark islands region and the south fiji basin show similar velocity changes at a depth of about 250 km and 150 km respectively the tasman sea is characterized by low velocity in the upper 400 km there is a good correlation between high velocity and seismicity below 150 km in the marginal sea regions

recognition and hydrologic significance of passive margin updip sequences an example from eocene coastal plain deposits u s a abstract sequence stratigraphic interpretations are extended to a passive margin updip setting using sedimentological observations from cores and well to well correlations in eocene coastal plain strata of south carolina in the succession studied formation contacts tend to follow sequence boundaries even as lithologies vary within individual sequences sequence boundaries at the base of the congaree formation and near the top of the tinker formation formed during relative sea level fall associated with second order global cycles these boundaries can be recognized clearly in both downdip and updip areas of the passive margin three other sequence boundaries which occur at the base and top of the warley hill formation and within the tinker formation are interpreted as formed during relative sea level fall associated with third order global cycles hydrostratigraphic units in the strata studied conform to depositional patterns that were controlled by changes in sea level and sediment influx sand of the gordon aquifer comprises a thick aggradational succession deposited predominantly in the nearshore shelf environment as accommodation increased during relative rise in sea level because of high rates of sedimentation in the proximal setting aggradational stacking of nearshore sands may be common to other updip marine strata in accommodation dominated regimes the overlying gordon confining unit consists of marine shelf clay and carbonate sediment deposited in response to maximum transgression during subsequent relative sea level fall accumulation of shoreface deposits produced a progradational succession that is represented by the lower part of the upper three runs aquifer unlike formation contacts boundaries between the clastic aquifers and confining units do not follow the third order sequence boundaries because of lithologic variations within the sequences an increasing degree of breaching through the gordon confining unit which results in downward contaminant migration into the gordon aquifer occurs in the updip direction because of nearly continuous sand deposition near the base of the interval studied contaminants migrate locally through the crouch branch confining unit because of erosional breaches formed by scour during sea level lowstand in this example and in other strata deposited in an updip passive margin setting the extent to which confining units are breached at sequence boundaries decreases in the downdip direction resulting in better protection of the adjacent aquifer

field study of dispersion in a heterogeneous aquifer 3 geostatistical analysis of hydraulic conductivity observations of the spatial variability of hydraulic conductivity at a tracer test site located at columbus air force base in mississippi are presented direct measurements of hydraulic conductivity of the heterogeneous alluvial aquifer at the site were made using borehole flowmeter logging slug tests and a laboratory permeameter to test undisturbed soil cores indirect methods estimating hydraulic conductivity were also evaluated including soil grain size analyses surface geophysical surveys and mapping of sediment facies the spatial covariance of the 2187 hydraulic conductivity values obtained with the borehole flowmeter method was examined the log hydraulic conductivity variance ln2k and the horizontal and vertical correlation scales h and v of 4 5 12 8 m and 1 6 m respectively were estimated assuming second order stationarity of the conductivity field the covariance parameters are uncertain with bounding values that are 24 76 above or below the estimate covariance parameters estimated with more limited nonflowmeter data were within the same magnitude as those obtained using the extensive flowmeter data suggesting that data from a variety of methods may be used to provide approximate values of the autocovariance parameters nonstationarity of the ln k field was examined by removing three dimensional polynomial trend surfaces and calculating variograms of the residuals significantly lower estimates for ln2k h and v of 2 7 4 8 m and 0 8 m respectively were obtained from the third order log conductivity residuals after trend removal the bounding parameter values differ 15 44 from the estimated values accounting for unsteady flow and the uncertainty in the covariance parameters of the third order log conductivity residuals the calculated longitudinal and horizontal transverse macrodispersivities ranged from 1 5 m to 1 8 m and 0 3 m to 0 6 m respectively

geodynamical implications from the correlation of surface geology and seismic tomographic structure abstract we have investigated the relationship between the lateral seismic structure in the mantle and the geological features associated with major mantle upwellings the oceanic ridge system and hotspots using the technique of correlation analysis we have identified that these features extend quite deeply into the mantle to a depth of around 1300 km this finding is surprising for the ridges because it indicates that the style of upwelling is rather active and is somewhat two dimensional in character the confidence level of the correlation between ridges and slow seismic regions is maintained at a level of greater than 90 to a depth of 1300 km this is followed by a sharp decrease to 50 at 1700 km a similar correlation pattern is found for the hotspots in both cases the correlation maxima lie close to a depth of 1000 km where remnants of old slabs have recently been revealed by correlation analysis these findings suggest that dynamical processes at a depth of around 1000 km can be linked with surface tectonic activity this correlation disappears at a depth of around 1500 1700 km certain features of the surface tectonic pattern can again be recognized around a depth of 2000 km and in the deepest mantle where major hotspot plumes and the remnant old lithosphere are the dominant features there may be some dynamical relationship between the ridge system and the two megaplumes we have proposed a physical mechanism based on viscous heating within megaplumes to explain the two peaks in the correlation between the hotspots and the seismic heterogeneities

solute transport in aquifers of arbitrary variability a time domain random walk formulation solute transport in three dimensional aquifers with spatially varying hydraulic conductivity of arbitrary point distribution is investigated the basis of our study is a multiindicator model mim representation of the heterogeneity combined with a self consistent approximation for groundwater flow and particle transport a time domain random walk tdrw approach is presented for computing the expected mass arrival along the longitudinal transport direction that is simple and honors the hydrodynamics of flow for any variability using hydraulic conductivity measurements at the made site and the mim it is shown that the travel time distribution for large variability cannot be well reproduced by the common distributions used for modeling hydrological transport such as the log normal distribution or the inverse gaussian distribution the proposed tdrw approach directly relates to the lagrangian trajectory formulation and is appropriate for applications where occurrence of negative flow velocities is small these results open new possibilities for modeling solute transport in aquifers of arbitrary variability by the time domain random walk that can readily account for a wide range of mass transfer reactions

aspherical heterogeneity of the mantle from phase velocities of mantle waves long period surface waves are used to map the lateral heterogeneity of the upper 100 600 km of the mantle there is good correlation of velocity with surface tectonics and heat flow convergence regions are generally slow for love waves and fast for rayleigh waves back arc basins have slower than average shallow mantle some island arcs show evidence of fast material at greater depth deep seated slow anomalies underlie the red sea afar region of north east africa western north american northern east pacific rise indian ocean triple junction and the tasman sea campbell plateau regions the fastest regions are in the north central australia new guinea and the south atlantic

upper mantle beneath southeast asia from s velocity tomography 1 we present a three dimensional s velocity model of the se asian western pacific upper mantle with 400 km lateral resolution using the novel automated multimode inversion technique we processed 4038 vertical component seismograms and extracted 22 708 linear equations with uncorrelated uncertainties that constrain upper mantle structure we used time frequency windows to select signal with negligible proportion of scattered energy the windows included the fundamental rayleigh mode and s and multiple s waves the observed range of s velocity variations is the widest 17 18 in the upper 150 km of the mantle high velocity continental roots can reach beyond the present extent of the overlying archean proterozoic crust by 500 km beneath some precambrian units the roots are absent which can be attributed to deformation and gradual destruction of the ancient lithosphere at 120 150 km s velocity beneath some cratons reaches 4 8 km s this can be accounted for by thermal and compositional effects beneath the hainan island area a low velocity anomaly is observed from near the surface to the bottom of our model the hot spot type volcanism here may be caused by the deep mantle hainan plume a low velocity mantle domain underlies the south central sea of japan surrounded on the surface by intraplate volcanoes a deep seismicity gap is present near 40 n in the pacific slab subducting below and may result from a plume slab interaction a high velocity anomaly is present in the transition zone beneath the northern boundary of the yangtze craton we propose that the anomaly corresponds to subducted continental lithosphere stagnant atop the 660 km discontinuity

whole earth structure estimated from seismic arrival times the arrival times of 10 compressional and shear phases p s pp pcp ss scs pk pab pk pbc pk pdf sk sac and two sets of differential times ss s410s and ss s660s are used to infer the earth s three dimensional structure with the exception of ss sds the raw data are composed of arrival times from the international seismological centre isc catalogue the isc events have been relocated using p and s phases and the ak135 radial earth model a total of 818 655 summary arrival times constrain lateral velocity variations in the crust mantle and core we also determine relocation parameters for all events stations corrections for each phase boundary topography 410 km 660 km core mantle boundary inner core boundary and inner core anisotropy variations our model of p and s velocity variations in the crust and mantle contains the general features observed in other body wave inversions a low velocity ring around the pacific ocean basin in the depth range 35 400 km high velocity anomalies associated with subducting slabs most prominent in the depth range 660 1070 km and high velocity anomalies surrounding the pacific basin just above the core mantle boundary in the outer core there is evidence of a latitudinal variation in velocity approaching 0 6 in magnitude with lower p velocities at the poles and higher velocities near the equator this pattern is observed throughout the outer core but is most prominent in the depth range 3671 4071 km and near the inner core boundary synthetic tests indicate that outer core features are moderately resolvable and inversions of random arrival times indicates that the anomalies are a factor of 2 above the estimated parameter noise level lateral heterogeneity in the inner core trades off with anisotropy resulting in poor resolution of isotropic velocity variations anisotropy in the inner core is predominantly subparallel to the earth s axis and of the order of 3 but this value can decrease if more inner core isotropic lateral heterogeneity is allowed a comparison of structure above and below the core mantle boundary cmb indicates that velocity heterogeneity is uncorrelated across the cmb but there is a moderate correlation between cmb topograpy and outer core heterogeneity an inversion in which the pk pdf residuals were absent indicates that the latitudinal pattern of outer core velocity variations is not due to the influence of inner core velocity structure

comment on investigating the macrodispersion experiment made site in columbus mississippi using a three dimensional inverse flow and transport model by heidi christiansen barlebo mary c hill and dan rosbjerg

estimation of the 3d correlation structure of an alluvial aquifer from surface based multi frequency ground penetrating radar reflection data knowledge about the stochastic nature of heterogeneity in subsurface hydraulic properties is critical for aquifer characterization and the corresponding prediction of groundwater flow and contaminant transport whereas the vertical correlation structure of the heterogeneity is often well constrained by borehole information the lateral correlation structure is generally unknown because the spacing between boreholes is too large to allow for its meaningful inference there is however evidence to suggest that information on the lateral correlation structure may be extracted from the correlation statistics of the subsurface reflectivity structure imaged by surface based ground penetrating radar measurements to date case studies involving this approach have been limited to 2d profiles acquired at a single antenna centre frequency in areas with limited complementary information as a result the practical reliability of this methodology has been difficult to assess here we extend previous work to 3d and consider reflection ground penetrating radar data acquired using two antenna centre frequencies at the extensively explored and well constrained boise hydrogeophysical research site we find that the results obtained using the two ground penetrating radar frequencies are consistent with each other as well as with information from a number of other studies at the boise hydrogeophysical research site in addition contrary to previous 2d work our results indicate that the surface based reflection ground penetrating radar data are not only sensitive to the aspect ratio of the underlying heterogeneity but also albeit to a lesser extent to the so called hurst number which is a key parameter characterizing the local variability of the fine scale structure

measurements of mantle wave velocities and inversion for lateral heterogeneities and anisotropy 3 inversion lateral heterogeneity in the earth s upper mantle is investigated by inverting dispersion curves of long period surface waves 100 330 s models for seven different tectonic regions are derived by inversion of regionalized great circle phase velocity measurements from our previous studies we also obtain a representation of upper mantle heterogeneities with no a priori regionalization from the inversion of the degree 6 spherical harmonic expansion of phase and group velocities the data are from the observation of about 200 paths for love waves and 250 paths for rayleigh waves for both the regionalized and the spherical harmonic inversions corrections are applied to take into account lateral variations in crustal thickness and other shallow parameters these corrections are found to be important especially at low spherical harmonic order the trench region and fast velocities down to 250 km under shields below 200 km under the oceans both s velocity and s anisotropy support a model of small scale convection in which cold blobs detach from the bottom of the lithosphere when its age is large enough the spherical harmonic models clearly demonstrate a posteriori the relation between surface tectonics and s velocity heterogeneities in the first 250 km all shields are fast most ridges are slow below 300 km a belt of fast mantle follows the pacific subduction zones however at greater depths large scale heterogeneities that seem to bear no relationship to surface tectonics are observed the most prominent feature at 450 km is a fast velocity region under the south atlantic ocean smaller scale heterogeneities that are not related to surface tectonics are also mapped at shallower depths an anomalously slow region centered in the south central pacific is possibly linked to intense hot spot activity a very fast region southeast of south america may be related to subduction of old pacific plate between 200 and 400 km a belt of sv sh anisotropy follows part of the ridge and subduction systems indicating vertical mantle flow in these regions the spherical harmonic results open new horizons for the understanding of convection in the mantle perspectives for the improvement of the models presented are discussed

three dimensional velocity structure and resolution of the core mantle boundary region from whole mantle inversions of body waves the nature of the core mantle boundary cmb has important implications for deep earth processes particularly those which have their origin in the lower mantle or outer core the possibility of the existence of lateral p wave velocity variations in the outermost core is explored here by obtaining models of three dimensional cmb region velocity structure using an inversion of waveform data the numerical inversions involve determination of the three dimensional structure of the earth s outermost core and lower mantle using over 5000 long period seismic waveforms collected from global digital seismic networks spheroidal modes with periods between 33 and 100 s were selected to model the body wave portion of seismograms recorded from global earthquakes first order perturbations in s wave velocities in 11 mantle layers 200 350 km thick and p wave velocities in one outermost core layer comprise the least squares solutions to the inverse problem although the statistical f test supports the additional layer in the inversions this layer is not required by the f ratio to occur in the outermost core pattern retrieval resolution tests in which synthetic data constructed from an initial synthetic earth model are inverted for model parameters are used to compare parameters for one region to those of another in which some coefficient power smearing is suspected depth resolution tests indicate that the best radial resolution at the cmb is 500 km thus this method does not produce the resolution required for outermost core lateral velocity variation analysis an examination of the limitations of this approach demonstrates the need for waveform inversion techniques which more accurately predict raypaths in the deep mantle improvements in radial resolution are needed before whole mantle velocity models can begin to distinguish whether significant heterogeneity related to core mantle interactions occurs in the cmb region

subtropical to temperate facies from a transition zone mixed carbonate siliciclastic system palaeogene north carolina usa palaeogene passive margin sediments on the us mid atlantic coastal plain provide valuable insight into facies interaction and distribution on mixed carbonate siliciclastic shelves this study utilizes well cuttings outcrop core and seismic data to document temporal and spatial variations in admixed bryozoan rich skeletal carbonates and sandy siliciclastic units that were deposited on a humid passive margin located in the vicinity of a major marine transition zone this zone was situated between north flowing warm waters of the ancestral gulf stream carbonate dominated settings and south flowing cold waters of the ancestral labrador current siliciclastic dominated settings some degree of mixing of carbonates and siliciclastics occurs in all facies however siliciclastic prone sediments predominate in nearshore settings while carbonate prone sediments are more common in more open marine settings of the inner shelf break and deep shelf a distinctive dual break shelf depositional profile originated following a major late cretaceous to palaeocene transgression that drowned the earlier shallow platform this profile was characterized by prominent mid shelf break dividing the shallow shelf from the deep shelf and a major continental shelf slope break incomplete filling of available accommodation space during successive buildup of the shallow shelf preserved the topographic break on this passive margin storm wave base also contributed to the preservation of the dual break shelf geometry by beveling shallow shelf sediments and transporting them onto and seaward of the mid shelf break sediment fines in deep shelf facies were produced in place transported downdip from the shallow shelf by storm ebb currents and boundary currents and reworked from adjacent areas of the deep shelf by strike parallel boundary currents regional climate and boundary currents controlled whether carbonate or siliciclastic material was deposited on the shelf with warmer waters and more humid climates favouring carbonate deposition and cooler more arid conditions favouring glaucony and siliciclastic dominated deposition continuous wave and current sweeping of the shallow shelf favoured deposition of mud lean facies across much of the shallow shelf skeletal components in much of the carbonate rich strata formed in warm nutrient rich subtropical waters as indicated by widespread occurrences of larger benthic foraminifera and molluscan assemblages these indicators of warm water deposition within the bryozoan mollusk rich carbonate assemblage on this shelf provide an example of a warm water bryomol assemblage such facies generally are associated with cooler water depositional settings

rate limited mass transfer or macrodispersion which dominates plume evolution at the macrodispersion experiment made site we present a model of solute transport that explains the large scale behavior of the solute tracer test plumes at the macrodispersion experiment made site as the result of advection and rate limited mass transfer between mobile and small scale immobile domains this model does not consider the process of dispersion and yet provides an alternative explanation of the evolution of the observed concentration profiles compared to the macrodispersion model the mass transfer model better represents the change in mobile dissolved mass with time the peak of the concentration profile and the profile asymmetry specifically unlike the macrodispersion model the mass transfer model explains the facts that the observed mass of the plume was greater than the injected mass in early snap shots of the plume and less than the injected mass at late times we suggest that the injected mass advects through the mobile domain and diffuses into and out of the immobile domain the immobile domain consists of a combination of low permeability zones on the scale of centimeters to decimeters the darcy scale immobile domain and intragranular porosity dead end pores and surface sorption the pore scale immobile domain we suggest that the mobile domain was sampled preferentially when water was extracted therefore at early times relatively clean water in the immobile domain was not sampled and incorrectly assumed to contain high solute concentrations similarly the mass at late times was underestimated because solute trapped in the pore scale immobile domain was not extracted during sampling and therefore ignored the combination of advection and slow mass transfer is consistent with the fact that the peak of the plume migrated only 5 m by the termination of the experiment as well as the different behavior of bromide and tritium tracers

characterization of alluvial hydrostratigraphy with indicator semivariograms current trends in hydrogeology seek to enlist sedimentary concepts in the interpretation of permeability structures however depositional models tend to account insufficiently for heterogeneities caused by complex controls on sediment preservation conversely geostatistical methods empirically describe both random and structured attributes this paper presents comparative indicator semivariograms for proximal medial and distal alluvial fan settings in santa clara valley california hydrostratigraphic structures revealed by a binary textural indicator are consistent within each setting yet differ from one setting to another in the bedrock bounded proximal setting buried channel deposits exhibit a small nugget effect and a zonal anisotropy with correlation ranges up to 900 m in the distal setting deposits display relatively weak hydrostratigraphic correlation with a relative nugget effect of 50 and a correlation range of 80 m in the medial setting the correlation range is similar to the proximal area but with a large nugget effect similar to the distal area

source scaling of contained chemical explosions as constrained by regional seismograms quantification of source coupling and characterization parameters for contained single fired chemical explosions observed at a regional seismic array are quantified the explosions were conducted in a mine in northeast wyoming where delay fired explosions occur regularly the primary observational data sets consist of close in measurements in the mine and regional observations at the international monitoring system primary array at pinedale wyoming pdar the single fired explosions ranged in size from 5500 to 50 000 lb and were separated from one another from 30 m to over 4 km peak amplitude measures at a single element of the regional array are well matched with a power law dependence on explosive weight similar scaling constants were determined for each of the dominant regional phases p n 0 84 0 14 p g 0 84 0 09 and l g 0 91 0 08 peak amplitudes across pdar show a factor of 3 variation for an individual explosion across all array elements this amplitude variation is accompanied by a decrease in spatial correlation with increasing station separation indicating the importance of near receiver structure the regional signals were further characterized by computing frequency dependent envelope functions at each array element consistent source scaling factors at a single array element were obtained from the envelope functions a high degree of spatial variability as a function of frequency was documented for the envelope functions spectral ratios are used to investigate source scaling relations for the different explosions four similarly prepared shots with total explosive weights between 5500 and 6000 lb were detonated to investigate source repeatability spectral ratio analysis identified two of the four shots as only partially detonating resulting in a reduction of long period spectral level by factors of 10 and 50 these long period reductions were accompanied by increases in source corner frequency consistent with a smaller source size spectral ratios of waveforms from the larger explosions that fully detonated illustrate that p g and l g source functions are similar the empirical source ratio is well modeled with a mueller murphy source model these experiments and the resulting data analysis suggest that simple single fired explosions of modest explosive weight can be used to calibrate regional seismic arrays networks and individual stations

spectra of mantle shear wave velocity structure summary we applied the stochastic method of gudmundsson davies clayton 1990 which was applied to isc p wave data to teleseismic isc s wave data to obtain an independent estimate of mantle structure we inverted the variance of s wave traveltime residuals of bundles of rays to obtain a description of the spectrum of lateral heterogeneity as a function of depth through the mantle the technique yields robust estimates of the traveltime scattering power the product of a characteristic scalelength of heterogeneity and the mean square of slowness perturbations we can estimate the characteristic scalelength half width from the autocovariance which can be reconstructed from the spectra hence by division we can estimate the root mean square slowness by extrapolating the variance of bundles of rays to bundles of zero cross sectional area we can also estimate the scale incoherent signal which is a plausible estimate of the noise in the data which is removed from the data we find that most of the structure generating shear wave traveltime residuals is located in the uppermost mantle about half of the structure is short scale harmonic degree 1 50 the large scale structure 1 50 has a half width of about 500 km in the upper half of the mantle this s wave half width is consistent with the p wave half widths determined by gudmundsson et al 1990 the s wave half width in the lower half of the mantle is poorly constrained it varies from 500 to 3000km which spans the better constrained value of 1200 km found by gudmundsson et al 1990 for p waves the incoherent scatter suggests that the signal to noise ratio of the s wave data set is around 1 5 assuming that the compressional and shear wave velocity variations are correlated then the signal weighted value of the ratio d in y ld in y is 2 as also found in normal mode studies this is much larger than the value of 0 8 1 4 suggested by laboratory experiments undertaken at atmospheric pressure there is no evidence of periodicity in the traveltime autocovariance this suggests little or no periodicity in the underlying convection the short half width through most of the mantle suggests high rayleigh number convection with its attendant small scale structures the power decreases by an order of magnitude or more in going from the upper mantle to the lower mantle the same as found by gudmundsson et al 1990 for p waves this large difference suggests either a change in convective regime and or a difference in the temperature sensitivity of elastic constants in both layers the increased short scale structure at the top of the mantle suggests that a large part of the seismic signature at this boundary is compositional since one would expect a red spectrum for a thermal boundary layer the derived spectra between 1 10 and i 50 are similar in shape to spectra from the mantle convection simulations of glatzmaier 1988 with a rayleigh number of 106 107 which would suggest layered convection if the comparison is valid

hierarchical geostatistics and multifacies systems boise hydrogeophysical research site boise idaho 1 the geostatistical structure of a heterogeneous coarse fluvial aquifer is investigated with porosity data derived from neutron logs at a research well field boise hydrogeophysical research site or bhrs that was designed in part to support three dimensional geostatistical analysis of hydrologic and geophysical parameters recognizing that the coarse fluvial deposits include subdivisions units between bounding surfaces we adopt a hierarchical approach and examine the porosity geostatistics of the aquifer at three scales at the bhrs the saturated fluvial deposits as a whole maximum interwell spacing 80 m thickness 16 18 m are at hierarchical level 1 five subhorizontal units within these deposits four cobble dominated units and a channel sand can be traced across the central area of the bhrs and are at hierarchical level 2 and subunits patches or lenses in one of the level 2 units unit 4 are at hierarchical level 3 we use variography and porosity statistics to recognize nonstationarity at hierarchical level 1 and in one of the level 2 units unit 4 where the means and variances of porosity differences as a function of lag are not constant between distinct units and subunits respectively the geostatistical structure at level 1 is modeled with different horizontal and vertical structures that have different sills vertical sill greater than horizontal sill the difference in sills can be explained quantitatively by the summing of weighted sills from all individual units and combined units i e a given pair of different units where the weights are the proportions of data pairs contributing to the sills at each lag from the individual and combined units extension of this analysis leads to a weighted multistructure form of the variogram function whereby a global experimental variogram in a hierarchical system can be decomposed quantitatively into weighted component individual and combined unit or facies structures for any number of units or hierarchical levels such decomposition of the global horizontal variogram from the bhrs indicates that short range periodicity in that structure is due to both 1 combined unit structures associated with patches or lenses at hierarchical level 3 in unit 4 and 2 variations in thickness of unit 2 for hierarchical multifacies systems structure models fit to global horizontal and vertical experimental variograms may not be useful for subsequent stochastic modeling if the system on which the structure models are based is nonstationary

field study of dispersion in a heterogeneous aquifer 1 overview and site description results are presented for a large scale natural gradient tracer experiment conducted in a heterogeneous alluvial aquifer at a site near columbus mississippi the study was initiated with a 48 hour pulse injection of 10 m3 of groundwater containing bromide and three organic tracers pentaflourobenzoic acid o trifluoromethylbenzoic acid and 2 6 diflourobenzoic acid over a 20 month period seven comprehensive samplings of the tracer plume were performed at approximately 1 to 4 month intervals using an extensive three dimensional sampling well network the dominant feature of the tracer plume that evolved during the study was the highly asymmetric concentration distribution in the longitudinal direction this asymmetry was produced by accelerating groundwater flow along the plume travel path that in turn resulted from an approximate 2 order of magnitude increase in the mean hydraulic conductivity between the near field and far field regions of the site the columbus study is distinct from previous natural gradient experiments because of the extreme heterogeneity of the aquifer the large scale spatial variations in groundwater velocity and the extensive set of hydraulic conductivity measurements for the aquifer

mapping the lower mantle determination of lateral heterogeneity in p velocity up to degree and order 6 the data from the international seismological centre bulletins for the years 1964 1979 are used to derive a three dimensional model of lateral variations of the p velocity in the lower mantle unlike previous studies in which such perturbations were represented by a blocklike parameterization we seek the solution in the form r k 0k l 0l m 0l k r kalm cos m kblm sin m plm cos some 500 000 travel time residuals for teleseismic distances from 5000 earthquakes are used in an iterative procedure to derive the coefficients a and b the maximum k and l used are 4 and 6 respectively in each iteration in addition to solving for the three dimensional structure we also relocate all the earthquakes perturb the average travel time curve and determine station corrections for over 1000 stations particular attention is given to the problem of weighting the individual observations in order to avoid as much as possible the bias due to the uneven distribution of sources and receivers the resulting model shows a high level of perturbations just below the 670 km discontinuity and just above the core mantle boundary where the maximum perturbations reach 1 1 5 of the average velocity even for this highly smoothed model at a depth of 2000 km the rms perturbations are some 3 to 4 times lower than at either of the two boundaries the model predicts well the large scale pattern of observed travel time residuals for various source regions except for the distinct effects of the subduction zones the most striking large scale three dimensional feature of the model is a ring of high velocities circumscribing the pacific basin within a depth range from 1000 km to the core mantle boundary if the proportionality between perturbations in the velocity and temperature is assumed the derived pattern of anomalies could be consistent with a two boundary layer model of convection in the lower mantle some caution however should be exercised in interpreting the results near the 670 km discontinuity where the resolving power of our data set is limited by the lack of adequate control of the upper mantle structure at the same time a significant global increase in the level of perturbations in the lowermost mantle is established beyond question the results of dziewonski et al 1977 on the correlation between the equivalent geoid and the observed geoid for the angular order numbers 2 and 3 is confirmed but there is no significant correlation for degrees from 4 to 6 these calculations are made for the rigid earth richards and hager this issue show that introduction of finite viscosity can change the sign of a geoid anomaly in addition recent studies of lateral variations in the shear velocity reveal the presence of large scale anomalies in the upper mantle thus while the inferences made here with respect to the origin of the gravest orders of the geopotential field are not conclusive they point the way in which results from seismology can be used to address some of the basic questions of geodynamics

transport upscaling in highly heterogeneous aquifers and the prediction of tracer dispersion at the made site we thank daniel fernandez garcia for sharing the data for the two concentration snapshots of the made 2 experiment and alraune zech and aldo fiori for sharing the made 1 data with us the authors acknowledge the financial support of the european research council through the project mhetscale grant agreement no 617511 and the spanish ministry of science and innovation through a severo ochoa project no cex2018 000794 s and the project hydropore pid2019 106887gb c31 juan j hidalgo acknowledges the support of the spanish ministry of science and innovation through a ramon y cajal fellowship no ryc 2017 22300 alessandro comolli acknowledges support through the prodex grant chypi

mantle structure beneath indonesia inferred from high resolution tomographic imaging we investigated mantle structure beneath the indonesian region by means of tomographic inversions of traveltime residuals of direct p and the surface reflected depth phases pp and pwp the hypocentres and phase data used in the inversions were derived from the reprocessing of data reported to international data centres which include data from the australian skippy project we used more than 6 0 10 data from more than 50 000 globally distributed earthquakes recorded at a subset of nearly 3000 seismological stations worldwide the use of depth phases improved the sampling of the upper mantle structure in particular beneath the back arc regions the mapping of distant aspherical mantle structure into the study region was minimized by combining a high resolution regional with a low resolution global inversion the inversion was linearized around the ak135 reference velocity model and a combination of minimum norm and gradient damping was applied to constrain the solution inversion of different subsets of the data and test inversions of synthetic data indicate that resolution is sufficient to substantiate the conclusions pertinent to the complex large scale structure of the subducted slab beneath the indonesian archipelago the tomographic images confirm previous evidence for regional slab penetration into the upper part of the lower mantle but suggest a more complex trajectory of mantle flow beneath indonesia the implied lateral variation in the shape of the upper mantle slab is generally in good agreement with inferences from seismicity the data reveal a seismic anomaly beneath the sunda arc which is detected to at least 1500 km in depth and forms the eastern end of a deep anomaly associated with the past subduction of lithosphere of the mesozoic tethys ocean below java the lithospheric slab is probably continuous from the earth s surface to the lower mantle but beneath sumatra the deep slab seems to be detached from the seismogenic slab the high resolution images suggest that the subducted slab is deflected in the transition zone beneath the banda arc and that the descending slabs form a spoon shaped structure north of the banda sea we detect the two opposing subducted slabs of the molucca sea plate this is consistent with previous studies but our images suggest that the westward subduction has a significantly steeper dip than the eastward subduction slab structure beneath the banda and molucca seas is explained in the context of the continent arc collision between australia and the southeast indonesian island arc and the arc arc collision between sangihe and halmahera inversion of traveltime residuals of direct s phases a novelty for this region largely confirms the inferences from the p wave data even though less detail is resolved

sedimentology and depositional environments of middle eocene terrigenous carbonate strata southeastern atlantic coastal plain usa abstract basin margin sediments of middle eocene age in the savannah river site area consist of five terrigenous carbonate lithofacies quartz sand calcareous quartz sand sandy carbonate muddy carbonate and a transitional lithofacies that ranges from sandy muddy carbonate to calcareous mud the middle eocene sediment package which includes calcareous parts of the upper congaree warley hill and santee formations dips southeast at 4 7 m km and thickens from 2 m at its updip edge to 95 m downdip the presence of glauconite and a diverse faunal assemblage in all lithofacies suggests deposition in clear well oxygenated open marine waters of normal salinity on the inner to middle shelf with periods of marginal marine nearshore and deltaic influence coarse grained terrigenous sand and calcareous sand deposited in higher energy nearshore environments occur near the updip limit fine grained terrigenous mud calcareous mud and sandy and muddy carbonate are located downdip and accumulated in quieter water conditions on the inner and middle shelf the transition from terrigenous to carbonate sediment occurs near the updip limit in a narrow zone less than 5 km wide three depositional sequences which contain transgressive and highstand system tracts are recognized within the middle eocene calcareous interval one is assigned to the upper congaree formation ta 3 5 3 6 cycles the main control on areal distribution hill formation ta3 4 cycle and one to the santee formation ta 3 5 3 6 cycles the main control on areal distribution of facies was depositional environment which was controlled primarily by sea level eustasy and the amount rate and locus of terrigenous influx in updip areas however sediment distribution and thickness were also influenced by middle eocene growth faulting diagenetic pathways vary with facies type but generally include 1 marine phreatic boring of skeletal fragments by algae and fungi grain micritization and radially fibrous cementation and 2 freshwater phreatic inversion of high mg calcite to low mg calcite dissolution of aragonitic allochems formation of moldic porosity precipitation of syntaxial calcite overgrowths on echinoderms formation of calcite spar and isopachous calcite cement neomorphism of micrite to microspar and pseudospar precipitation of opal ct lepispheres replacement of mollusk shells by chalcedony and precipitation of zeolites within secondary moldic pores quartz rich facies have high interparticle porosity and excellent permeability mud rich facies have low to moderate porosity and permeability owing to the isolation of moldic and vug pores

the spectrum of tomographic earth models summary the properties of mantle convection are expected to generate characteristic signatures in the spectrum of mantle heterogeneities and in its dependence on depth the investigation of present tomographic models and the associated spectra of seismic velocity perturbations can provide insight into this problem the characterization of heterogeneities in the mantle at all scales involves combining and comparing tomographic models at both global and regional scales the former are expanded into the spherical harmonics domain while the latter are expanded into the fourier domain the comparison of both types of expansions is possible if we consider power spectral density per unit surface such a comparison should be carried out with great care and the scaling factors are derived to make it meaningful the method is applied to recent global and regional tomographic models it is shown that contrary to previous assertions there is an overall agreement between both kinds of models

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 1 experimental design and observed tracer movement a large scale natural gradient tracer experiment was conducted on cape cod massachusetts to examine the transport and dispersion of solutes in a sand and gravel aquifer the nonreactive tracer bromide and the reactive tracers lithium and molybdate were injected as a pulse in july 1985 and monitored in three dimensions as they moved as far as 280 m down gradient through an array of multilevel samplers the bromide cloud moved horizontally at a rate of 0 42 m per day it also moved downward about 4 m because of density induced sinking early in the test and accretion of areal recharge from precipitation after 200 m of transport the bromide cloud had spread more than 80 m in the direction of flow but was only 14 m wide and 4 6 m thick the lithium and molybdate clouds followed the same path as the bromide cloud but their rates of movement were retarded about 50 relative to bromide movement because of sorption onto the sediments

a lithofacies approach for modeling non fickian solute transport in a heterogeneous alluvial aquifer stochastic realizations of lithofacies assemblage based on lithological data from a relatively small number of boreholes were used to simulate solute transport at the well known macrodispersion experiment made site in mississippi usa with sharp vertical contrasts and lateral connectivity explicitly accounted for in the corresponding hydraulic conductivity fields experimental results from a large scale tracer experiment were adequately reproduced with a relatively simple model based on advection and local dispersion the geologically based model of physical heterogeneity shows that one well interconnected lithofacies with a significantly higher hydraulic conductivity and accounting for 12 of the total aquifer volume may be responsible for the observed non fickian transport behavior indicated by the asymmetric shape of the plumes and by variations of the dispersion rate in both space and time this analysis provides a lithological basis to the hypothesis that transport at made site is controlled by a network of high conductivity sediments embedded in a less permeable matrix it also explains the calibrated value of the ratio of mobile to total porosities used in previous modelling studies based on the dual domain mass transfer approach the results of this study underscore the importance of geologically plausible conceptualizations of the subsurface for making accurate predictions of the fate and transport of contaminants in highly heterogeneous aquifers these conceptualizations may be developed through integration of raw geological data with expert knowledge interpretation and appropriate geostatistical methods