a joint monte carlo analysis of seafloor compliance rayleigh wave dispersion and receiver functions at ocean bottom seismic stations offshore new zealand teleseismic body wave imaging techniques such as receiver function analysis can be notoriously difficult to employ on ocean bottom seismic data due largely to multiple reverberations within the water and low velocity sediments in lieu of suppressing this coherently scattered noise in ocean bottom receiver functions these site effects can be modeled in conjunction with shear velocity information from seafloor compliance and surface wave dispersion measurements to discern crustal structure a novel technique to estimate 1 d crustal shear velocity profiles from these data using monte carlo sampling is presented here we find that seafloor compliance inversions and p s conversions observed in the receiver functions provide complimentary constraints on sediment velocity and thickness incoherent noise in receiver functions from the moana ocean bottom seismic experiment limit the accuracy of the practical analysis at crustal scales but synthetic recovery tests and comparison with independent unconstrained nonlinear optimization results affirm the utility of this technique in principle

wave field decomposition of ocean bottom seismograms seismograms recorded on the seafloor are affected by reverberations in the overlying ocean layer we examine the feasibility of removing these reverberations through a 1d wave field decomposition based on a reflection transmission formulation of the problem two decomposition schemes are presented the first scheme involves a simple manipulation of the fundamental matrix relating stress and displacement of plane harmonic waves to upgoing and downgoing wavevector coefficients and requires measurement of both ocean bottom displacement and pressure the second approach involves only displacement recordings and knowledge of the water column depth this latter quantity will generally be known a priori from deployment logs or alternatively it may be estimated using vertical displacement and pressure seismograms in a preprocessing step both approaches require prior information on seabed properties in the case of p wave incidence the decomposition depends primarily on the seabed s velocity this quantity can be determined by examining trial decompositions over a range of s and selecting the value that minimizes the energy of the upgoing s wave component at the arrival time of the incident wave we apply this approach to synthetic seismograms for a simple earth structure and to recordings of two large events from the central oregon locked zone array colza on the continental margin of oregon the real data indicate that the wave field decompositions are largely successful at lower frequencies 0 1 hz but that 3d scattering likely originating near the sediment basement contact is manifested at higher frequencies

wavefield decomposition for passive ocean bottom seismological data summary seismic data from ocean bottom stations show strong water layer multiples on the hydrophone and seismometer channels depending on the water depth and the seafloor impedance contrast these multiples can be attenuated by means of a wavefield decomposition wdc into up and downgoing wavefields we apply an elastic decomposition scheme to earthquake recordings in the tyrrhenian sea to demonstrate the potentials for different passive seismological studies a three step decomposition approach has been developed giving optimal results for our earthquake data relative amplification factors between hydrophone and seismometer can be constrained during decomposition in our case factors in between 0 25 and 0 4 have been found we show that water layer multiples on recordings of local deep earthquakes are significantly reduced so that structural phases in the coda of the p phase can be studied the seafloor p wave impedance contrast at two nearby stations is estimated to the orders of 1 3 and 1 5 indicating that the uppermost layer was very muddy and unconsolidated we demonstrate with synthetic data that teleseismic receiver functions are strongly distorted by means of water layer multiples the wdc significantly improves the signal to noise ratio of structural phases in receiver functions a single station application to real data confirms the theoretical predictions we predict the biasing effect of traveltime residuals as estimated by cross correlation of teleseismic recordings from different stations in the order of up to 8 s at waves with a dominant period of 50 s waveform decomposition removes this apparent traveltime residual and enables unbiased estimates the theoretical predictions are verified with real data from two teleseismic earthquakes based on our results we strongly recommend applying an elastic wdc to passive seismological recordings on broad band stations

multivariate spatial analysis of lake sediment geochemical data melville peninsula nunavut canada abstract a multivariate spatial analysis was conducted on a suite of glacial till geochemical data collected over the melville peninsula nunavut canada previous studies demonstrated through the application of multivariate statistical techniques that the composition of the lake sediment geochemistry reflects the underlying geology in northern canada in this study the application of minimum maximum autocorrelation factor analysis maf to glacial till geochemistry has extended the knowledge and description of the underlying geology through the recognition of spatially correlated factors that represent distinct lithologic features and glacial transport processes maps of posterior probabilities for the underlying lithologies were estimated based on the ma factors and compared with those from standard principal component analysis the use of maf provides a measured improvement in predictive mapping irrespective of the choice of lag separation

determining crustal structure beneath seismic stations overlying a low velocity sedimentary layer using receiver functions the receiver function rf technique has been widely applied to investigate crustal and mantle layered structures using p to s converted ps phases from velocity discontinuities however the presence of low velocity relative to that of the bedrock sediments can give rise to strong reverberations in the resulting rfs frequently masking the ps phases from crustal and mantle boundaries such reverberations are caused by p to s conversions and their multiples associated with the strong impedance contrast across the bottom of the low velocity sedimentary layer here we propose and test an approach to effectively remove the near surface reverberations and decipher the ps phases associated with the moho discontinuity autocorrelation is first applied on the observed rfs to determine the strength and two way traveltime of the reverberations which are then used to construct a resonance removal filter in the frequency domain to remove or significantly reduce the reverberations the filtered rfs are time corrected to eliminate the delay effects of the sedimentary layer and applied to estimate the subsediment crustal thickness and vp vsusing a h k stacking procedure the resulting subsediment crustal parameters thickness and vp vs are subsequently used to determine the thickness and vp vs of the sedimentary layer using a revised version of the h k stacking procedure testing using both synthetic and real data suggests that this computationally inexpensive technique is efficient in resolving subsediment crustal properties beneath stations sitting on a low velocity sedimentary layer and can also satisfactorily determine the thickness and vp vs of the sedimentary layer

compositional data analysis in the geosciences from theory to practice since karl pearson wrote his paper on spurious correlation in 1897 a lot has been said about the statistical analysis of compositional data mainly by geologists such as felix chayes the solution appeared in the 1980s when john aitchison proposed to use iogratios since then the approach has seen a great expansion mainly building on the idea of the natural geometry of the sample space statistics is expected to give sense to our perception of the natural scale of the data and this is made possible for compositional data using iogratios this publication will be a milestone in this process this book will be of interest to geologists using statistical methods it includes the intuitive justification of the methodology convincing through case studies and presenting user friendly software which includes a section for those who need to see the proof of the mathematical consistency of the methods used

satellite gravity and the mass balance of the antarctic ice sheet changes in the earth s gravity field with time have important applications to a broad range of disciplines any process that involves a large enough horizontal redistribution of mass either within the earth or on or above its surface is potentially detectable in particular when ice sheets grow or shrink gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets the sources of global sea level rise about 2 mm a 1 over the last century and in particular the contribution of the antarctic ice sheet thereto are not well understood gravity measurements can help to diminish this uncertainty the technology currently exists to measure gravity with high accuracy by a dual satellite mission in which the distance between the satellites is precisely monitored we estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the antarctic ice sheet to a precision corresponding to better than 0 01 mm a 1 of sea level change however the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in antarctic ice postglacial rebound inter annual variability in snowfall and atmospheric pressure trends also need to be evaluated postglacial rebound could be partly separated from ice mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission determination of inter annual ice mass changes will be aided by measurements of moisture flux divergence around the perimeters of the ice sheets and direct observations of inter annual changes by the gravity satellite itself the removal of pressure effects over antarctica will become more effective as the number of automatic weather stations in the interior of the continent increases even after corrections are made for these factors the uncertainties they cause limit the accuracy in the determination of the contribution of the antarctic ice sheet to sea level change to about 0 5 mm a 1 however there is a strong complementarity between gravity measurements and the surface height measurements that will be produced by nasa s laser altimeter mission early next century together they should be able to determine that contribution to an accuracy of about 0 1 mm a 1

evidence for upper crustal anisotropy in the songpan ganze northeastern tibet terrane 1 the radial and transverse receiver functions obtained at several stations located on the songpan ganze terrane tibetan plateau are characterized by strong p to s conversions in the first 4 s after the direct p wave we show that the amplitude variations of these phases with back azimuth can be well explained by a simple model with one or two anisotropic layers the anisotropy we obtained is quite strong about 15 and might be related to the presence of highly deformed flyschs and schists in the first 25 km of the crust this study shows that anisotropy in the crust could be locally high and has to be taken into account when analyzing teleseismic data

paleomagnetism and geochronology of the ecstall pluton in the coast mountains of british columbia evidence for local deformation rather than large scale transport 1 samples for geochronologic geobarometric and paleomagnetic analyses were collected across the northern portion of the ecstall pluton southeast of prince rupert british columbia al in hornblende geobarometry indicates pressures from 740 10 to 840 30 mpa corresponding to crystallization depths of 25 to 30 km u pb analyses of zircons from western central and eastern localities within the pluton yield crystallization ages of 91 5 1 0 ma 90 8 1 0 ma and 90 5 1 0 ma respectively rock magnetic experiments reflected light microscopy and thermal demagnetization behavior suggest that natural remanent magnetism is carried by low ti titanohematite unblocking temperatures of the characteristic remanent magnetization chrm are dominantly in the 560 c to 630 c range with age of magnetization approximated by the 40ar 39ar hornblende ages of 84 2 0 10 ma on the western margin and 76 4 0 6 ma in the center of the pluton site mean chrm directions were isolated for paleomagnetic samples from 23 sites and are distributed along a small circle with subhorizontal axis at 340 azimuth chrm directions from the central portion of the pluton are concordant with the expected cretaceous magnetic field direction while chrm directions from the western margin are discordant by 70 folding of the ecstall pluton either during late cretaceous west directed thrust transport above the convex upward prince rupert shear zone or during younger deformation of the pluton and underlying shear zone can account for the paleomagnetic data and is consistent with the geochronologic geobarometric and structural geologic observations

receiver functions using obs data promises and limitations from numerical modelling and examples from the cascadia initiative the expanding fleet of broadband ocean bottom seismograph obs stations is facilitating the study of the structure and seismicity of oceanic plates at regional scales for continental studies an important tool to characterize continental crust and mantle structure is the analysis of teleseismic p receiver functions in the oceans however receiver functions potentially suffer from several limiting factors that are unique to ocean sites and plate structures in this study we model receiver functions for a variety of oceanic lithospheric structures to investigate the possibilities and limitations of receiver functions using obs data several potentially contaminating effects are examined including pressure reverberations from the water column for various ocean floor depths and the effects of a layer of low velocity marine sediments these modelling results indicate that receiver functions from obs data are difficult to interpret in the presence of marine sediments but shallow water sites in subduction zone forearcs may be suitable for constraining various crustal elements around the locked megathrust fault we propose using a complementary approach based on transfer function modelling combined with a grid search approach that bypasses receiver functions altogether and estimates model properties directly from minimally processed waveforms using real data examples from the cascadia initiative we show how receiver and transfer functions can be used to infer seismic properties of the oceanic plate in both shallow cascadia forearc and deep juan de fuca ridge ocean settings

receiver function study of the hellenic subduction zone imaging crustal thickness variations and the oceanic moho of the descending african lithosphere summary we use data from recently installed broad band seismographs on the islands of crete gavdos santorini naxos and samos in the hellenic subduction zone to construct receiver function images of the crust and upper mantle from south of crete into the aegean sea the stations are equipped with sts 2 seismometers and they are operated by gfz potsdam university of chania and eth zurich teleseismic earthquakes recorded by these stations at epicentral distances between 35 and 95 have been used to calculate receiver functions the receiver function method is a routinely used tool to detect crustal and upper mantle discontinuities beneath a seismic station by isolating the p s converted waves from the coda of the p wave converted p s energy from the oceanic moho of the subducted african plate is clearly observed beneath gavdos and crete at a depth ranging from 44 to 69 km this boundary continues to the north to nearly 100 km depth beneath santorini island because of a lack of data the correlation of this phase is uncertain north of santorini beneath the aegean sea moho depths were calculated from primary converted waves and multiply reflected waves between the moho and the earth s surface beneath southern and eastern crete the moho lies between 31 and 34 km depth beneath western and northern crete the moho is located at 32 and 39 km depth respectively and behaves as a reversed crust mantle velocity contrast possibly caused by hydration and serpentinization of the forearc mantle peridotite the moho beneath gavdos island located south of crete in the libyan sea is at 26 km depth indicating that the crust south of the crete microcontinent is also thinning towards the mediterranean ridge this makes it unlikely that part of the crust in crete consists of accreted sediments transported there during the present day subduction process which began approximately 15 ma because the backstop i e the boundary between the current accretionary wedge of the mediterranean ridge and the crete microcontinent is located approximately 100 km south of gavdos a seismic boundary at 32 km depth beneath santorini island probably marks the crustal base of the crete microcontinent a shallower seismic interface beneath santorini at 20 25 km depth may mark the depth of the detachment between the crete microcontinent and the overlying aegean subplate the moho in the central and northern aegean at naxos and samos is observed at 25 and 28 km depth respectively assuming a stretching factor of 1 2 1 3 crustal thickness in the aegean was 30 35 km at the inception of the extensional regime in the middle miocene

marine multicomponent seismology marine multicomponent seismology has seized the geophysical industry s fancy since its semicommercial emergence in the north sea in the autumn of 1996 the essence of this technology is recording s waves in addition to conventional p waves on the seafloor with sensor packages containing hydrophones and three component geophones new processing algorithms have had to be developed to properly process these data

data driven adaptive decomposition of multicomponent seabed recordings dual sensor hydrophone and three component geophone data recorded on the seafloor allow the elastic wavefield to be decomposed into its upgoing and downgoing p and s wave components most decomposition algorithms require accurate knowledge of the elastic properties of the seafloor in the vicinity of the receivers and properly calibrated sensors in order for the data to be a faithful vector representation of the ground motion we present a multistep adaptive decomposition scheme that provides the necessary information directly from the data by imposing constraints on intermediate decomposition results the proposed scheme requires no a priori information and only a minimal amount of user defined input thus allowing multicomponent data to be decomposed in an automated data driven fashion the performance of the technique is illustrated using seabed data acquired in the north sea with prototype single sensors multicomponent geophones individually sampled realistic seafloor properties and sensor calibration operators are obtained and elastic decomposition of the calibrated data generally yields good results dominant water layer reverberations are successfully attenuated and primary reflections are substantially enhanced in the computed upgoing p wave potential just below the seafloor in contrast the result for the upgoing s wave potential is somewhat less convincing although the energy of water layer multiples is substantially reduced notable amounts of undesired multiple energy remain in this section after decomposition particularly at high offsets these imperfections may point to inaccuracies in the parametrization of the seafloor or remaining inaccuracies in the vector fidelity of the horizontal geophone recordings nevertheless the results obtained with the extended data driven decomposition scheme are at least comparable to previously published results

decomposition of multicomponent sea floor data into upgoing and downgoing p and s waves a method for decomposing multicomponent sea floor measurements into upgoing and downgoing p and s waves is presented we assume that a marine survey employing a marine source in the water layer is conducted over a plane layered medium from recordings of the pressure just above the sea floor and the particle velocity vector just below the sea floor decomposition filters can be determined by plane wave analysis the decomposition filter coefficients depend on the p and s wave velocities and the density at the sea bottom we show how to decompose the multicomponent measurements into upgoing and downgoing p and s vertical traction components vertical particle velocity components and horizontal particle velocity components the decomposition filters are applied with good results to synthetic data modeled in a plane layered medium

glacial isostatic adjustment on a rotating earth summary we extend and complete previous work to compute the influence of perturbations to the rotation vector on a suite of observables associated with glacial isostatic adjustment gia we emphasize observables relevant to present and future geodetic missions for example present day 3 d crustal motions relative sea level change and geoid or absolute sea level variations our calculations adopt spherically symmetric self gravitating maxwell viscoelastic earth models while incorporating realistic mass ice plus ocean load and rotation variations the predicted rotation induced signals are dominated by the influence of true polar wander tpw the spatial geometry of the tpw induced relative sea level geoid and radial velocity fields is primarily that of a degree two order one surface spherical harmonic the spatial variation of the horizontal velocity vectors is given by the gradient of this harmonic the peak radial and horizontal velocities are of the order of 0 5 mm yr 1 however we show that this value is sensitive to the adopted profile of mantle viscosity we also demonstrate that an accurate prediction of tpw induced sea level and 3 d crustal deformation rates requires that a realistic number of glacial cycles be incorporated into the ice load history we conclude that geodetic observations of the gia process should be analysed using a gia theory valid for a rotating planet finally we also consider variations in rotation driven by simple present day polar melting scenarios and predict the influence of these variations on a suite of geophysical observables we find that the rotational feedback associated with greenland melting is capable of significantly perturbing both relative and absolute sea level variations

source scaling of earthquakes in the shumagin region alaska time domain inversions of regional waveforms the scaling of pulse duration to seismic moment is estimated for earthquakes along an interplate thrust zone from digital waveforms recorded by short period and broad band instruments of the east aleutian shumagin seismic network we measure pulse duration using an empirical green s function technique based on damped time domain deconvolution from several thousand events 22 earthquakes with magnitudes 3 0 7 0 and depths 23 56 km are found to give reliable estimates of pulse duration durations are also determined directly from one parameter nonlinear inversions for a variety of simple functional forms of source time functions symmetric source pulses boxcar or triangle shapes fit waveforms better than an asymmetric model t exp 2t d for most 62 per cent of the waveform pairs while the asymmetric model fits best for only 8 per cent of the data pulse duration increases with the size of events from 0 1 to 10s over the seismic moment m0 range of 1014 to 3 1019 nm when normalized by the cube root of seismic moment pulse durations show 8 x variation comparable static stress drop estimates range from 0 2 to 135 mpa contrary to predictions of some laboratory and theoretical studies earthquakes at the deepest part of the thrust zone do not show significantly higher stress drops than do shallower events rupture properties however show a strong dependence on earthquake size the three largest events m0 5 1018nm have the three longest normalized durations on average 3 8 times longer than those for smaller events the durations require smaller events to have 10 100 x larger static stress drops or 4 x faster rupture velocities or some combination of the two possibly the largest events rupture both strong and weak patches while smaller events just rupture strong patches on the fault surface the characteristic dimension that separates large from small events 3 15 km is comparable to characteristic wavelengths of pacific basin bathymetry and may reflect the influence of the subducted sea floor upon fault zone heterogeneity

using surface regolith geochemistry to map the major crustal blocks of the australian continent abstract multi element near surface geochemistry from the national geochemical survey of australia has been evaluated in the context of mapping the exposed to deeply buried major crustal blocks of the australian continent the major crustal blocks interpreted from geophysical and geological data reflect distinct tectonic domains comprised of early archean to recent cenozoic igneous metamorphic and sedimentary rock assemblages the geochemical data have been treated as compositional data to uniquely describe and characterize the geochemistry of the regolith overlying the major crustal blocks across australia according to the following workflow imputation of missing censored data log ratio transformation multivariate statistical analysis multivariate geospatial minimum maximum autocorrelation factor analysis and classification using cross validation techniques the uniqueness of each major crustal block has been quantified the ability to predict the membership of a surface regolith sample to one or more of the major crustal blocks is demonstrated the predicted crustal block assignments define spatially coherent regions that coincide with the known crustal blocks in some areas inaccurate predictions are due to uncertainty in the initial crustal boundary definition or from surficial processes that mask the crustal block geochemical signature in conclusion the geochemical composition of the australian surface regolith generally can be used to map the underlying crustal architecture despite secondary modifications due to physical transport and chemical weathering effects this methodology is however less effective where extensive and thick sedimentary basins such as the eromanga and eucla basins overlie crustal blocks

structure of the oceanic lithosphere and upper mantle north of the gloria fault in the eastern mid atlantic by receiver function analysis receiver functions rf have been used for several decades to study structures beneath seismic stations although most available stations are deployed on shore the number of ocean bottom station obs experiments has increased in recent years almost all obss have to deal with higher noise levels and a limited deployment time 1 year resulting in a small number of usable records of teleseismic earthquakes here we use obss deployed as mid aperture array in the deep ocean 4 5 5 5 km water depth of the eastern mid atlantic we use evaluation criteria for obs data and beam forming to enhance the quality of the rfs although some stations show reverberations caused by sedimentary cover we are able to identify the moho signal indicating a normal thickness 5 8 km of oceanic crust observations at single stations with thin sediments 300 400 m indicate that a probable sharp lithosphere asthenosphere boundary lab might exist at a depth of 70 80 km which is in line with lab depth estimates for similar lithospheric ages in the pacific the mantle discontinuities at 410 km and 660 km are clearly identifiable their delay times are in agreement with prem overall the usage of beam formed earthquake recordings for obs rf analysis is an excellent way to increase the signal quality and the number of usable events

decomposition of multicomponent seismic data into primary p and s wave responses1 inversion of multicomponent seismic data can be subdivided in three main processes 1 surface related preprocessing decomposition of the multicomponent data into primary p and s wave responses 2 prestack migration of the primary p and s wave responses yielding the angle dependent p p p s s p and s s reflectivity of the subsurface 3 target related post processing transformation of the reflectivity into the rock and pore parameters in the target this paper deals with the theoretical aspects of surface related preprocessing which consists of two steps 1 decomposition of the multicomponent data pseudo p and s wave responses into true p and s wave responses 2 elimination of the surface related multiple reflections and conversions

moment and duration of shallow earthquakes from love wave modelling for regional distances abstract love waves from five earthquakes in southwest germany italy yugoslavia greece and algeria as recorded at the broadband grafenberg array in eastern bavaria are modelled in detail using an extended reflectivity method the focal mechanisms are taken from the literature or determined from long period wwnss data the theoretical double couple moment function used for modelling increases smoothly during the risetime t from zero to the seismic moment m0 t and m0 are determined by matching the observed and theoretical love wave seismograms in the long period wwnss frequency band t is approximately equal to the rupture duration values from 1 4 to 20 s are found seismic moments generally agree within a factor of about two with those found by other authors from larger data sets the earthquakes in southwest germany and greece were simple events and can be modelled very well by one double couple in the case of the other earthquakes the theoretical love wave seismograms are too short for these earthquakes there is some independent evidence for a multiple event nature this evidence is condensed into source models consisting of two or three double couples representing separate and complete sub earthquakes which then explain the observations quite well in the case of the algerian earthquake the long love wave duration may also be due to complications in structure along the wavepath across the mediterranean and the alps the present results show that accurate love wave modelling for a single station at regional distance from an epicentre is a reliable method for estimation of seismic moment and rupture duration use of a digitally recording station with large dynamic range allows events over a large magnitude interval to be studied the grafenberg array is well suited for such an investigation of european and north african earthquakes

oceanic lithospheric s wave velocities from the analysis of p wave polarization at the ocean floor our knowledge of the absolute s wave velocities of the oceanic lithosphere is mainly based on global surface wave tomography local active seismic or compliance measurements using oceanic infragravity waves the results of tomography give a rather smooth picture of the actual s wave velocity structure and local measurements have limitations regarding the range of elastic parameters or the geometry of the measurement here we use the p wave polarization apparent p wave incidence angle of teleseismic events to investigate the s wave velocity structure of the oceanic crust and the upper tens of kilometres of the mantle beneath single stations in this study we present an up to our knowledge new relation of the apparent p wave incidence angle at the ocean bottom dependent on the half space s wave velocity we analyse the angle in different period ranges at ocean bottom stations obs to derive apparent s wave velocity profiles these profiles are dependent on the s wave velocity as well as on the thickness of the layers in the subsurface consequently their interpretation results in a set of equally valid models we analyse the apparent p wave incidence angles of an obs data set which was collected in the eastern mid atlantic we are able to determine reasonable s wave velocity depth models by a three step quantitative modelling after a manual data quality control although layer resonance sometimes influences the estimated apparent s wave velocities the apparent s wave velocity profiles are well explained by an oceanic prem model in which the upper part is replaced by four layers consisting of a water column a sediment a crust and a layer representing the uppermost mantle the obtained sediment has a thickness between 0 3 km and 0 9 km with s wave velocities between 0 7 km s 1 and 1 4 km s 1 the estimated total crustal thickness varies between 4 km and 10 km with s wave velocities between 3 5 km s 1 and 4 3 km s 1 we find a slight increase of the total crustal thickness from 5 km to 8 km towards the south in the direction of a major plate boundary the gloria fault the observed crustal thickening can be related with the known dominant compression in the vicinity of the fault furthermore the resulting mantle s wave velocities decrease from values around 5 5 km s 1 to 4 5 km s 1 towards the fault this decrease is probably caused by serpentinization and indicates that the oceanic transform fault affects a broad region in the uppermost mantle conclusively the presented method is useful for the estimation of the local s wave velocity structure beneath ocean bottom seismic stations it is easy to implement and consists of two main steps 1 measurement of apparent p wave incidence angles in different period ranges for real and synthetic data and 2 comparison of the determined apparent s wave velocities for real and synthetic data to estimate s wave velocity depth models

process recognition in multi element soil and stream sediment geochemical data abstract stream sediment and soil geochemical data from the upper and lower coastal plains of south carolina usa were studied to determine relationships between soils and stream sediments from multi element associations characteristic compositions were determined for both media primary associations of elements reflect mineralogy including heavy minerals carbonates and clays and the effects of groundwater the effects of groundwater on element concentrations are more evident in soils than stream sediments a winnowing index was created using ratios of th to al that revealed differing erosional and depositional environments both soils and stream sediments from the upper and lower coastal plains show derivation from similar materials and subsequent similar multi element relationships but have some distinct differences in the lower coastal plain soils have high values of elements concentrated in heavy minerals ce y th that grade into high values of elements concentrated into finer grain size lower density materials primarily comprised of carbonates and feldspar minerals mg ca na k al these gradational trends in mineralogy and geochemistry are inferred to reflect reworking of materials during marine transgressions and regressions upper coastal plain stream sediment geochemistry shows a higher winnowing index relative to soil geochemistry a comparison of the 4 media upper coastal plain soils and stream sediments and lower coastal plain soils and stream sediments shows that upper coastal plain stream sediments have a higher winnowing index and a higher concentration of elements contained within heavy minerals whereas lower coastal plain stream sediments show a strong correlation between elements typically contained within clays it is not possible to calculate a functional relationship between stream sediment soil compositions for all elements due to the complex history of weathering deposition reworking and re deposition however depending on the spatial separation of the stream sediment and soil samples some elements are more highly correlated than others

a sediment mixing process model of till genesis using texture and clay mineralogy data from saginaw lobe michigan usa tills we present a sediment mixing process model of till genesis based on data from surface tills of the saginaw lobe terrain in lower michigan our research uses a spatial approach to understanding glacial landsystems and till genesis we sampled calcareous till at 336 upland sites and at 17 sites in lacustrine sediment of the saginaw lake plain the loamy tills have bimodal grain size curves with a fine texture mode near the silt clay boundary and a sand mode spatial grouping analysis suggests that tills can be divided into six groups each with different textures and clay mineral compositions that vary systematically down ice the similarity among groups with respect to the silt clay mode and clay mineralogy argues for a common origin for the fines illite rich lacustrine sediment of the saginaw lake plain fine textured sediments were probably entrained transported and deposited down ice as till which also becomes sandier and enriched in kaolinite reflecting increasing mixing with shallow sandstone bedrock with distance from the lacustrine clay source clayey tills on the flanks of the saginaw terrain may reflect proglacial ponding against nearby uplands a process model of progressive down ice mixing of preexisting fine lake sediments with crushed abraded sandstone bedrock helps to better explain till textures compared with a purely crushing abrasion process model

seismic wavefield separation by multicomponent tau p polarisation filtering abstract this paper presents a modified form of controlled direction reception cdr filter to separate p and s waves in a multi component seismic profile the aim of cdr is to enhance the clarity of the section the essence of the method in seeking s wave extinction is to perform a dot product between the signal vector and the polarisation slowness vector during projection of the section into tau p space using the p wave velocity along the array alternatively s waves can be enhanced and all other wave types including background noise suppressed by using a conjugate rotation operator and the s velocity profile in forming the slant stack a two dimensional gain function based on the rectilinearity of particle motion is then applied in tau p space as a non linear boost function in order to enhance strongly polarised arrivals synthetic and physical model examples are used to demonstrate the noise rejection properties of the cdr process and to show how p and s wave seismic sections can be separately obtained

statistical analysis of lake sediment geochemical data for understanding surface geological factors and processes an example from amazonian upland lakes brazil abstract statistical evaluation applied to geochemical data of upland lake sediments and their catchment basins rocks from serra dos carajas was used to identify geochemical signatures associated with underlying processes sediment provenances and source sink relationship the lakes are violao amendoim and tres irmas ti1 ti2 and ti3 a centred log ratio transformation clr was used prior to multivariate analyses in order to eliminate closure issues in compositional data due to the similarity between 15n values and organic sources mainly from c3 plants the three lakes were clustered together violao lake receives largest organic contribution from autochthonous sources such as siliceous sponge spicules and algae except for it shallower portion wnw extension which is more similar to ti2 having low 15n values that are similar to the isotopic signature of upland swamps the upper continental crust ucc normalization pattern shows that sediments are mainly enriched in fe p and se which is closely related to the catchment lithology the distribution of elements in ti2 is significantly different from the other lakes because it is dominated by organic carbon while the other lakes are a mix of detritus and organic carbon factor analysis fa using clr transformed data distinguishes several geochemical assemblages in the sediments with the major detritic groups being similar to catchment basin laterites the ti zr hf nb y hrees group corresponds to resistant minerals which remained stable during lateritization the lrees group reflects mobilization and reprecipitation by ree bearing minerals and the al v cr sc association reflects metavolcanic rock the fe p mo as zn cluster in the sediments is attributed to fe oxyhydroxide precipitation while toc so3 hg se group is controlled by organic matter principal component analysis pca further indicates that detritic lake sediments are not directly derived from the parent rocks but from weathered crusts mainly ferruginous laterites and soils which is consistent with their elements ratios

multivariate anomaly modeling of primary geochemical halos by u spatial statistic algorithm development a case study from the sari gunay epithermal gold deposit iran abstract an accurate separation of anomalous areas values in primary geochemical halos with heterogeneous spatial variations requires an appropriate algorithm that considers the complex patterns and multivariate relationships of the input geochemical data there are several problems in multivariate modeling of geochemical compositional data because such data present spurious values of spatial correlation between the variables to address this problem this paper proposes an improved u spatial statistic algorithm for 3d multivariate anomaly modeling of the geochemical dataset with compositional nature at the sari gunay epithermal gold deposit nw iran to perform 3d multivariate modeling isometric logarithmic ratio ilr as an effective method to transform compositional data from the simplex to real space and minimum maximum autocorrelation factor maf as a multivariate geostatistical method were used in an integrated analysis in comparison to the other separation techniques this integrated approach has an advantage to control the heterogeneous spatial variations in the input data in this approach we improved the u spatial statistic method by using the variogram tool theory by using this approach we identified the primary geochemical haloes associated with au as sb hg front halo elements cu ag pb near ore halo elements and ni co tail halo elements at the sari gunay gold depsoit the results were validated by using contrast coefficient and exploratory index tools by examining the 3d multivariate primary anomalous geochemical halos zones of possible hidden epithermal gold and porphyry copper gold mineralizations were recognized at this deposit for future exploration

seismological evidence for a mid mantle discontinuity beneath hawaii and iceland abstract receiver functions derived from body waves recorded in iceland and on the hawaiian islands reveal a seismic velocity discontinuity at about 1050 km depth beneath the two regions of presumed mantle upwelling the waveforms of the converted phases from the mid mantle discontinuity indicate a velocity increase with depth the lack of consistent scattering found in recent systematic searches for seismic boundaries in the middle mantle argues against a globally continuous sub horizontal mineralogical phase transition near 1000 km depth the sense of the velocity change at the mid mantle discontinuity beneath the two hotspots is consistent with geodynamic models in which the mantle has distinct chemical reservoirs and the material beneath the compositional boundary in these areas is more silicon rich than the overlying mantle although the possibility of a yet unknown phase transition particular to mantle plume material cannot be ruled out