influence of grain fabric and lamination on the anisotropy of hydraulic conductivity in unconsolidated dune sands in local scale groundwater flow problems like for instance in contaminated groundwater studies it becomes increasingly important for proper prediction of contaminant migration to incorporate small scale geological and associated parameter heterogeneity in groundwater flow models of the micro scale geological heterogeneities the effect of grain fabric and lamination in unconsolidated sediments on the vertical anisotropy of effective hydraulic conductivity has received relatively little attention this is mainly due to the low conductivity contrast between laminae in combination with the friable nature of unconsolidated sediment which makes it sensitive to disturbances during experimental procedures as an alternative digital image analysis of sediment thin sections was applied to separate and quantify both causes of anisotropy the effective value of vertical anisotropy ratio of unconsolidated eolian dune sand as determined experimentally on distributed orientated core plugs ranges between 1 10 and 1 50 this wide range is partly caused by artificial noise introduced by distributed sampling in a heterogeneous medium and assuming thereby that the sampled material is homogeneous by applying digital image analysis of thin sections high resolution logs of hydraulic conductivity were generated simple upscaling of these values to effective conductivity parallel and perpendicular to sedimentary laminae provided quantitative estimates of the vertical anisotropy caused by lamination anisotropy values range between 1 0 and 1 075 the anisotropy ratio due to grain fabric ranges in value between 1 05 and 1 45 assuming that both anisotropy due to grain fabric and lamination are orientated identically if this is not the case the effective anisotropy is the weighted mean of anisotropies of the constituent layer types this study shows that for eolian sands the anisotropy owing to grain fabric dominates the effective value of anisotropy if conductivity contrast between laminae increases the contribution of anisotropy caused by grain fabric to the effective value of anisotropy decreases

upper mantle structure under western europe from fundamental and higher mode surface waves using the nars array summary a generalized inversion of a new data set consisting of surface wave phase velocities and sn traveltimes has resulted in a new shear velocity and density model for the west european platform wepl 2 the surface wave phase velocity data set consists of fundamental and higher mode mode 1 6 measurements from 25 to 70mhz using the network of autonomously recording stations nars array which was specifically designed for higher mode surface wave measurements the sn traveltime data set consists of isc readings for selected european events major features of wepl 2 are a high velocity lid of 80 140 km depth underlain by a pronounced low velocity zone between 160 and 220 km depth the transition zone 400 650 km depth is characterized by high shear velocities with respect to prem the density shows a positive gradient from 60 to 140 km depth followed by an approximately constant value down to 400 km depth a model for the baltic shield scsh 2 is obtained by combination of nolet s 1977 higher mode phase velocity data set for western europe including the baltic shield and the present phase velocities for the platform this shield model shows an absence of the low velocity layer and low shear velocities in the top of the transition layer with respect to wepl 2 density although less well resolved shows lower values for the shield structure between 200 and 350 km depth

tomographic images of the iberian subcrustal lithosphere and asthenosphere the s wave velocity structure of the lithopheric mantle and asthenosphere beneath iberia is displayed by means of tomographic images obtained from dispersion data of rayleigh waves propagating across the iberian region we have used long period data recorded at the broadband stations of the network of autonomously recording seismographs nars installed in the iberian peninsula on the occasion of the iberian lithosphere heterogeneity and anisotropy iliha project a total of 64 teleseismic events provided by the iliha array and 143 seismic paths have been studied surface wave dispersion analysis is carried out using various methods from methods for a correct acquisition of data and subsequent two station surface wave velocity measurements to inversion methods for velocity structure and methods for verifying the reliability of the inversion results the phase and group velocity dispersion curves of the fundamental mode rayleigh waves are the basic information from which we have obtained several earth models represented by shear wave velocity distributions with depth using these inversion results we display the most conspicuous features of the velocity stnicture of the iberian lithosphere asthenosphere system and propose a new regional model the iberian lithosphere asthenosphere ila model for the deep structure of the iberian peninsula down to a depth of 200 km we use a representation technique based on an iterative laplacian interpolation method for obtaining tomographic images of the subcrustal lithosphere and asthenosphere of iberia we find significant lateral velocity variations in the peninsula though these differences vary with depth interval a low velocity channel in the lithosphere 41 51 km appears with nonuniform velocity structure in contrast at the greatest lithospheric depths 51 81 km almost the entire peninsula shows a rather uniform velocity structure the asthenosphere 81 181 km is clearly a nonhomogeneous gross layer both laterally and with depth the relatively higher velocities span the shallower depths within the asthenosphere whereas the lower ones span the deeper part

multi level slug tests in highly permeable formations 1 modification of the springer gelhar sg model a multi level slug test model and a method for the evaluation of vertical profiles of hydraulic conductivity in highly permeable formations are developed a double packer system is employed to estimate local hydraulic conductivity depending on the formation and double packer system parameters the water level recovery in the tested well can exhibit a monotonic or oscillatory response to discern information on aquifer properties from artifacts introduced by the measurement system the theory of flow in an aquifer and a double packer system is developed the mathematical model incorporates features of the springer and gelhar 1991 model and reduces to the bouwer and rice 1976 model in a special case the model involves equations of momentum and mass conservation for the double packer system with quasi steady well aquifer interaction equations the method is uniformly applicable for both monotonic and oscillatory well responses and can produce profiles of hydraulic conductivity for the tested well the criterion is given to determine the type of well response for given slug test conditions

creation of a digital database for xxth century historical earthquakes occurred in the iberian area the problems of recovering the seismic information contained in the old seismograms through their digitization and processing by computer methods are discussed we present the main principles of a simple manual technique for digitization of early seismic records of the wiechert seismograph detrending of the zero line slope circular arc removal smoothing and interpolation treatment of the digital data are made the accuracy of the digitizing process is assessed and its reliability is tested by a comparison with automatically obtained digital data and their spectral amplitudes the deconvolution of the seismograph response has allowed us to obtain the time variation of ground motion which is then contrasted with direct measurements of ground motion displacement amplitudes given in the old time bulletins we have created a digital database for historical earthquakes which occurred in the iberian area during the period 1912 1940 and recorded by the wiechert seismograph at the geophysical observatory of toledo spain it contains the following output data the digitized original records the geometrically corrected and interpolated data the time variation of ground motion maximum amplitudes and corresponding periods total duration of the seismic oscillations and amplitude spectra we carry out magnitude estimates and give formulae for magnitude classification based on the signal duration and on the maximum ground displacement amplitude we also perform seismic moment determinations by spectral analysis of waveforms and propose a new seismic moment magnitude relation

shear velocity structure beneath the iberian massif from broadband rayleigh wave data abstract up to a few years ago dispersion analyses of surface waves across the iberian peninsula and adjacent zones were based on analog data recorded at the long period iberian stations the installation of the nars array on iberian territory for a period of one year has provided a greater station density than was previously available with the very few permanent long period seismological stations installed on the peninsula the nars array also provided quality digital records and increased the path coverage for two station surface wave velocity measurements fundamental mode rayleigh waves recorded at broadband stations belonging to this array have been analyzed to produce phase and group velocity dispersion curves for the period range 10 90 s with the dataset now available the elastic structure beneath the iberian massif has been investigated in terms of the shear velocity distribution as a function of depth time variable filtering is employed to remove higher mode interference efficiently and to improve isolation of the fundamental mode rayleigh wave from the seismograms multiple filtering is then used to compute group velocities at each station the interstation rayleigh wave group velocity can thus be easily calculated frequency domain wiener deconvolution is used to determine the interstation phase velocity we perform inversion of velocity dispersion data containing both rayleigh wave phase velocities and group velocities according to the generalized inversion theory by means of the stochastic inverse operator the theoretical models for the lower crust and uppermost mantle beneath the iberian massif obtained by joint inversion show a continental lithosphere with a thickness of 81 km the crustal and subcrustal velocities are greater than in other areas of the iberian peninsula the asthenosphere appears as a layer 100 km thick defined by very low velocities when compared with the rest of the peninsular area both the lithosphere and the asthenosphere exhibit a low velocity channel in the lithosphere a subcrustal low velocity channel has velocity constrained between 4 33 and 4 62 km s 1 in the asthenosphere the low velocity channel is constrained between 4 13 and 4 36 km s 1

characterization of meter scale spatial variability of riverbed hydraulic conductivity in a lowland river aa river belgium abstract an improved general understanding of riverbed heterogeneity is of importance for all groundwater modeling studies that include river aquifer interaction processes riverbed hydraulic conductivity k is one of the main factors controlling river aquifer exchange fluxes however the meter scale spatial variability of riverbed k has not been adequately mapped as of yet this study aims to fill this void by combining an extensive field measurement campaign focusing on both horizontal and vertical riverbed k with a detailed geostatistical analysis of the meter scale spatial variability of riverbed k in total 220 slug tests and 45 standpipe tests were performed at two test sites along the belgian aa river omnidirectional and directional variograms along and across the river were calculated both horizontal and vertical riverbed k vary over several orders of magnitude and show significant meter scale spatial variation horizontal k shows a bimodal distribution elongated zones of high horizontal k along the river course are observed at both sections indicating a link between riverbed structures depositional environment and flow regime vertical k is lognormally distributed and its spatial variability is mainly governed by the presence and thickness of a low permeable organic layer at the top of the riverbed the absence of this layer in the center of the river leads to high vertical k and is related to scouring of the riverbed by high discharge events variograms of both horizontal and vertical k show a clear directional anisotropy with ranges along the river being twice as large as those across the river

spatial variability of hydraulic conductivity of an unconfined sandy aquifer determined by a mini slug test abstract the spatial variability of the hydraulic conductivity in a sandy aquifer has been determined by a mini slug test method the hydraulic conductivity k of the aquifer has a geometric mean of 5 05 10 4 m s 1 and an overall variance of 1n k equal to 0 37 which corresponds quite well to the results obtained by two large scale tracer experiments performed in the aquifer a geological model of the aquifer based on 31 sediment cores proposed three hydrogeological layers in the aquifer concurrent with the vertical variations observed with respect to hydraulic conductivity the horizontal correlation length of the hydraulic conductivity has been determined for each of the three hydrogeological layers and is found to be small 1 2 5 m the asymptotic longitudinal dispersivity of the aquifer has been estimated from the variance in hydraulic conductivity and the horizontal correlation length to be in the range of 0 3 0 5 m compared with a value of 0 42 m obtained in one of the tracer tests performed

processing and inversion of long period surface wave data collected in the iberian peninsula summary several filtering techniques have been used to remove the effects of multipathing and modal contamination and to isolate the fundamental mode from rayleigh wavetrains group velocity data are obtained by means of the multiple filter technique a time variable filter has allowed the influence of noise as well as the interference produced by higher modes to be removed multiple filtering is then used again to compute group velocities at each station the interstation group velocity for the fundamental mode rayleigh wave is estimated according to the velocities at two stations frequency domain wiener deconvolution is used to compute the phase velocity between two stations the well known three station method is applied to correct the distances travelled by the waves across the array and therefore to determine interstation phase and group velocities in a more accurate manner on the other hand lateral refraction at the atlantic continental edge of the peninsula is also studied phase velocities are corrected for the anelastic effect inversion of the interstation rayleigh wave phase velocities is then made in accordance with generalized inversion theory to obtain theoretical 2 d layered earth models in this paper these methods are applied to rayleigh waves generated by teleseismic events propagating across the iberian peninsula and recorded at wwssn stations as a consequence new and principal features for the iberian lithosphere asthenosphere system are obtained a very interesting feature of the the iberian lithosphere was found a low velocity layer directly under the moho between 39 and 64 km depth with shear velocities ranging from 4 12 to 4 37 km s 1 the iberian asthenosphere which lies between 100 and 180km depth is not an homogeneous layer and shows a negative velocity gradient from top to bottom together with a sudden increase in shear velocity beneath the low velocity zone

measurement of anisotropic hydraulic conductivity in unconsolidated sands a case study from a shoreface deposit oyster virginia in this study an integrated field and laboratory method which can be used to evaluate the magnitude and distribution of anisotropic hydraulic conductivity at the scale of bedding structures in unconsolidated sediment is demonstrated undisturbed sediment cores 10 16 cm in diameter and 18 25 cm long are obtained using a split barrel core sampler two undisturbed 5 72 cm diameter 7 90 cm long subcores oriented parallel and perpendicular to the primary bedding structures are then obtained from each field core the hydraulic conductivities of the subcores are then measured with a constant head permeameter the sampling and experimental procedures are designed to minimize potential sources of error sixty four 10 16 cm cores were sampled in a coastal sand outcrop located 300 m from a subsurface injection experiment near oyster virginia four distinct lithologies were sampled in horizontal transects with a spacing of 0 5 m between core locations in addition iron oxide bands which were prevalent throughout the exposure were sampled from both ends of the outcrop the average hydraulic conductivity values are consistent with the observable geologic features grain size sorting and iron oxide banding hydraulic conductivity is greater in the parallel oriented subcore for 90 of the core pairs and mean hydraulic conductivity ratios of parallel to perpendicular oriented subcores k k for the different lithologies ranged from 1 33 to 1 57 the major control on the anisotropy in this sediment is interpreted to be preferential grain orientations resulting from depositional processes with additional influences from the prominence of the bedding structures and secondary features such as hydrous iron oxide banding

partitioned waveform inversion and two dimensional structure under the network of autonomously recording seismographs nonlinear optimization methods are very effective in finding models that predict optimal waveform fits to observed seismograms provided the number of model parameters is small to reduce the size of the large scale two or three dimensional seismic modelling problem path integrals over seismic velocities may be defined as model parameters instead of the seismic velocities themselves this partitions the large scale optimization problem into a number of independent small scale problems and reduces the computational effort by several orders of magnitude the path integral parameters are transformed such that their correlation matrix becomes diagonal a linear inversion performs the mapping from the space of path integral parameters into the model space of seismic velocities and makes backus gilbert resolution analysis possible the method has been applied to body wave and surface wave data from the broadband portable network of autonomously recording seismographs nars in western europe using a surface wave ray approximation to generate synthetics by mode summation waveforms were fitted for frequencies as high as 50 mhz variations in s velocity as large as 6 1 have been established with a vertical resolution of 100 150 km and a horizontal resolution as small as 400 km in parts of the model although a low velocity layer is present under the southern part of the nars array such layer is very weak or absent north of the paris basin horizontal velocity gradients are well resolved down to 400 km depth

shear wave velocity tomography of the lithosphere asthenosphere system beneath the mediterranean area abstract the purpose of this study is deriving a 3d tomographic image of the shear wave velocity structure of the lithosphere asthenosphere system of the mediterranean region from rayleigh wave fundamental mode dispersion data the database consists of almost 200 wavetrains corresponding to regional events recorded at the mednet very broad band stations placed in the mediterranean area on the basis of the path averaged group velocities derived for each epicentre station trajectory local group velocities over the area covered by the seismic paths have been obtained for the 10 90 s period range by means of yanovskaya s formulation for laterally heterogeneous media according to the resolution of these local velocities a grid of 1 of latitude per 1 of longitude has been defined over the mediterranean area and a local group velocity dispersion curve has been then assigned to each gridpoint the stochastic inversion of almost 450 local dispersion curves permits deriving the respective 1d shear velocity structures from which the elaboration of a 3d tomographic image of the lithosphere asthenosphere system of the mediterranean region is straightforward as expected taking into account the complexity of this area the shear velocity model reveals significant lateral changes in the crust and uppermost mantle elastic structure as a main feature low shear velocities are deduced for most part of the central and eastern mediterranean basin at shallow depths down to 35 40 km whereas significantly higher velocities are obtained for the basins of the western mediterranean at this depth range this velocity pattern suggests a thicker crust in the centraleastern part with a greater thickness of sedimentary layers on account of the lower velocities deduced for the uppermost levels on the contrary for depths 80 km low shear velocities are obtained towards the west while the highest shear velocities are derived for the eastern mediterranean sea the aegean sea greece the centre and the south of the italian peninsula and the adriatic sea sicily and tunisia the velocity pattern at this depth range suggests a deeper beginning of the asthenosphere varying between 100 and 150 km under these areas while a shallower top around 70 km depth is found beneath the western mediterranean sea the areas where a thicker lithosphere has been deduced depict the main contact between the eurasian and african plates this feature being related to the collision and subduction processes linked to the convergence of both lithospheric plates

crust and upper mantle structure of the central iberian meseta spain summary quarry blasts recorded along three lines on the central iberian meseta are used in an attempt to interpret the crustal structure the results of the interpretation of the data together with published surface wave and earthquake data suggest a layered structure of the crust having the following features the basement in some areas covered by up to 4 km of sediments has a p velocity of 6 1 km s 1 a low velocity layer between 7 and 11 km depth seems to exist on the basis of both p and s interpretation of seismic data a thick middle crust of 12 km has a p velocity of 6 4 km s 1 and overlies a lower crust with a mean p velocity of 6 9 km s 1 and a possible slight negative gradient the mean vp vs ratio for the crust is about 1 75 the moho is reached at about 31 km depth and consists of a transition zone at least 1 5 km thick the p velocity of the upper mantle is close to 8 1 km s 1 and the s velocity about 4 5 km s 1 which gives a vp vs ratio of 1 8 for the uppermost mantle a tentative petrological interpretation of the velocities and composition of the layers is given

deep structure of the iberian peninsula determined by rayleigh wave velocity inversion summary a rigorous study of velocity dispersion of surface waves generated by teleseismic events propagating across the iberian peninsula and traversing main geological units has been carried out from a set of selected analogue data as digital records have only become available recently dispersed seismic signals have been obtained over a period of 16 years between 1967 and 1982 at the five iberian stations having long period instruments in our study we have considered many earthquakes thus obtaining a fairly good path coverage of most of the peninsula for two station rayleigh wave velocity measurements in all cases the approach azimuths of the wavefronts were carefully checked several digital filtering techniques have been employed to remove the effects of multipathing and modal contamination and to isolate the fundamental mode from rayleigh wavetrains thus we have obtained good estimates for both phase and group velocities a time variable filter has reduced the influence of noise and removed higher mode interference multiple filtering is then used to compute group velocity frequency domain wiener deconvolution is used to compute the interstation phase velocity the determined average rayleigh wave velocities reveal differences in the propagation conditions of the seismic energy across the peninsula a mapping of velocities for various periods of reference together with a mapping of errors in velocity are the basis for obtaining the rayleigh wave velocity distribution in the peninsula theoretical 2 d layered earth models are obtained by joint inversion of phase and group velocity dispersion curves using the stochastic inverse operator in our inversion scheme we use velocities corrected for anelastic effects finally a 3 d mapping of s velocity is performed this study shows important regional features of the deep structure of iberia we see small lateral inhomogeneities and also two low velocity layers one with shear velocities usually ranging from 4 23 to 4 31 km s 1 directly under the moho and another the asthenosphere with a negative velocity gradient for depths between 81 and 181 km terminated at the bottom by a sharp discontinuity

first two station rayleigh wave velocity measurements for the northern iberian region abstract up to now dispersion analysis of surface waves across the iberian peninsula and adjacent zones has been based on analog data recorded at the long period iberian stations also the northern region of the peninsula has never been investigated due to the lack of seismological stations with the iliha data set now available it is possible to investigate the northern part of iberia from quality digital records to efficiently remove higher mode interference and to improve isolation of the fundamental mode rayleigh wave from the seismograms time variable filtering is employed once the signal is filtered multiple filtering is then used to compute group velocities at each station the interstation rayleigh wave group velocity can thus be easily calculated frequency domain wiener deconvolution is used to determine the interstation phase velocity we carried out inversion of velocity dispersion data containing both rayleigh wave phase velocities and group velocities according to the generalized inversion theory by means of the stochastic inverse operator the theoretical 2 d earth models determined by joint inversion allow us to obtain for the first time the distribution of the shear wave velocity both laterally and with depth for the northern iberian region and to emphasize the main features of the crust mantle structure of this area

upper mantle anelasticity and tectonic evolution of the western united states from surface wave attenuation rayleigh wave phase and group velocities and attenuation coefficients in the period range 18 to 120 s have been determined for three regions along nine paths across the western united states using a two station technique the attenuation coefficients were found to increase from east to west between the rocky mountains and the pacific coast rayleigh wave group and phase velocities were inverted using a differential procedure to obtain shear wave velocity models for three regions these velocity models were then used in an inversion process where q 1 as a function of depth was obtained from observations of rayleigh wave attenuation the inversion results show that q values in the upper mantle of the western united states are lowest for the coastal regions and westernmost basin and range and highest for the rocky mountains and western great plains intermediate q values appear to occur in the upper mantle beneath the basin and range province and the columbia and colorado plateaus although uncertainties in the data prevent a clear separation between that region and coastal regions low values of q occur in the upper crust higher values in the lower crust and highest values in the uppermost 20 km of the mantle of all these regions these overlie an upper mantle low q zone in which q values decrease from east to west lowest values 15 20 being similar to those observed above descending slabs in the western pacific the regional pattern of upper mantle shear wave q values is similar to that observed for upper crustal shear wave q values inferred from surface wave studies and for lg coda q values the patterns of upper crustal and upper mantle q variations correlate with the temporal sequence of tectonic and magmatic activity in the western united states lowest q values in both depth ranges occurring where tectonic activity has been most recent partial melting and or enhanced dislocation motion in the mantle and variations in the volume of interstitial hydrothermal fluids in cracks in the upper crust may both be ultimately due to processes which occurred during plate consumption and interaction near the western margin of the united states

seismic imaging of the western iberian crust using ambient noise boundaries and internal structure of the iberian massif abstract we present new rayleigh wave dispersion maps of the western iberian peninsula for periods between 8 and 30 s obtained from correlations of seismic ambient noise following the recent increase in seismic broadband network density in portugal and spain group velocities have been computed for each station pair using the empirical green s functions generated by cross correlating one day length seismic ambient noise records the resulting high path density allows us to obtain lateral variations of the group velocities as a function of period in cells of 0 5 0 5 with an unprecedented resolution as a result we were able to address some of the unknowns regarding the lithospheric structure beneath sw iberia the dispersion maps allow the imaging of the major structural units namely the iberian massif and the lusitanian and algarve meso cenozoic basins the cadiz gulf gibraltar strait area corresponds to a strong low velocity anomaly which can be followed to the largest period inverted although slightly shifted to the east at longer periods within the iberian massif second order perturbations in the group velocities are consistent with the transitions between tectonic units composing the massif

aragonite saturation state dynamics in a coastal upwelling zone 1 coastal upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state ar waters to the surface that are further suppressed by anthropogenic co2 ar was calculated with ph pco2 and salinity derived alkalinity time series data from autonomous ph and pco2 instruments moored on the oregon shelf and shelf break during different seasons from 2007 to 2011 surface ar values ranged between 0 66 0 04 and 3 9 0 04 compared to an estimated pre industrial range of 1 0 0 1 to 4 7 0 1 upwelling of high co2 water and subsequent removal of co2 by phytoplankton imparts a dynamic range to ar from 1 0 to 4 0 between spring and autumn freshwater input also suppresses saturation states during the spring winter ar is less variable than during other seasons and is controlled primarily by mixing of the water column

a test of the great circle approximation in the analysis of surface waves a new way of reconstructing wave fronts is de veloped for testing the validity of the great circle approxima tion in dispersion analysis of surface waves phase and time delays between pairs of stations of an array are used to re construct the wave fronts or surfaces of equal phase this techque is applied to fundamental mode rayleigh waves recorded at the nars stations dudlag the iliha iberian lithosphere heterogeneity and anisotropy project the re sulting wave fronts are compared with the theoretical ones i e calculated assuming that the waves have traveled along the great circle path with a constant phase velocity and the angle between both fronts is calculated waves traveling mosfiy through a laterally homogeneous oceanic path before arriving to the iberian peninsula are analyzed for the fre quency range of 10 to 60 mhz these show angles up to 8 degrees between the theoretical wave fronts and the wave fronts reconstructed using the delay data this implies that we make a relative error less than 1 when calculating path averaged phase velocities ignoring the deviation of the ar rival of the wave from the great circle direction

large scale dispersion experiments in a sandy aquifer in denmark observed tracer movements and numerical analyses a large scale natural gradient dispersion experiment was carried out in a sandy aquifer in the western part of denmark using tritium and chloride as tracers for both plumes a marked spreading was observed in the longitudinal direction while the spreading in the transverse horizontal and transverse vertical directions was very small the horizontal transport parameters of the advection dispersion equation were investigated by applying an optimization model to observed breakthrough curves of tritium representing depth averaged concentrations no clear trend in dispersion parameters with travel distance for distances between 50 and 200 m could be found suggesting that the asymptotic stage was reached within a short distance from the point of injection a three dimensional numerical model for flow and transport was applied to the aquifer in order to quantify the dispersivity parameters more closely the following best fit dispersivity parameters were identified longitudinal horizontal 0 45 m transverse horizontal 0 001 m and transverse vertical 0 0005 m

shear wave velocity structure below the iberian peninsula as obtained by a detailed analysis of surface waves abstract a tentative tomography of iberia based on broadband surface wave data is performed for the first time in this paper we have complemented a previous study of the northern half of the iberian peninsula with a study of the southern half of the peninsula based on a detailed analysis of rayleigh wave dispersion now we present the first shear velocity contour maps at different subcrustal depths quality digital records provided by the nars array have been used standard techniques as multiple filtering and time variable filtering are employed to efficiently remove higher mode interference and improve isolation of the fundamental mode rayleigh wave from the seismograms and thus to calculate the interstation rayleigh wave group velocity frequency domain wiener deconvolution is used to determine the interstation phase velocity we perform simultaneous inversion of phase and group velocity dispersion data by means of the stochastic inverse operator the inversion results previously reported for the northern iberian region together with the results obtained here are used for 3 d mapping of shear wave velocity over the iberian peninsula lateral variation in velocity at five depth intervals chosen in agreement with the theoretical earth models determined by joint inversion is displayed for the lithosphere and asthenosphere of iberia

deep structure of pyrenees range sw europe imaged by joint inversion of gravity and teleseismic delay time we present a new model of the lithosphere and asthenosphere structure down to 300 km depth beneath the pyrenees from the joint inversion of recent gravity and teleseismic data unlike previous studies crustal correction was not applied on teleseismic data in order i to preserve the consistency between gravity data which are mainly sensitive to the density structure of the crust lithosphere and traveltime data and ii to avoid the introduction of biases resulting from crustal reductions the density model down to 100 km depth is preferentially used here to discuss the lithospheric structure of the pyrenees whereas the asthenospheric structure from 100 to 300 km depth is discussed from our velocity model the absence of a high density anomaly in our model between 30 and 100 km depth except the labourd density anomaly in the northern part of the pyrenees seems to preclude eclogitization of the subducted iberian crust at the scale of the entire pyrenean range local eclogitization of the deep pyrenean crust beneath the western part of the axial zone west of andorra associated with the positive central density anomaly is proposed the pyrenean lithosphere in density and velocity models appears segmented from east to west no clear relation between the along strike segmentation and mapped major faults is visible in our models the pyrenees lithosphere segments are associated with different seismicity pattern in the pyrenees suggesting a possible relation between the deep structure of the pyrenees and its seismicity in the upper crust the concentration of earthquakes localized just straight up the central density anomaly can reflect the subsidence and or delamination of an eclogitized pyrenean deep root the velocity model in the asthenosphere is similar to previous studies the absence of a high velocity anomaly in the upper mantle and transition zone i e 125 to 225 km depth seems to preclude the presence of a detached oceanic lithosphere beneath the european lithosphere

from unthinned continent to ocean the deep structure of the west iberia passive continental margin at 38 n abstract the crustal and lithospheric mantle structure at the south segment of the west iberian margin was investigated along a 370 km long seismic transect the transect goes from unthinned continental crust onshore to oceanic crust crossing the ocean continent transition oct zone the wide angle data set includes recordings from 6 obss and 2 inland seismic stations kinematic and dynamic modeling provided a 2d velocity model that proved to be consistent with the modeled free air anomaly data the interpretation of coincident multi channel near vertical and wide angle reflection data sets allowed the identification of four main crustal domains i continental east of 9 4 w ii continental thinning 9 4 w 9 7 w iii transitional 9 7 w 10 5 w and iv oceanic west of 10 5 w in the continental domain the complete crustal section of slightly thinned continental crust is present the upper ucc 5 1 6 0 km s and the lower continental crust lcc 6 9 7 2 km s are seismically reflective and have intermediate to low p wave velocity gradients the middle continental crust mcc 6 35 6 45 km s is generally unreflective with low velocity gradient the main thinning of the continental crust occurs in the thinning domain by attenuation of the ucc and the lcc major thinning of the mcc starts to the west of the lcc pinchout point where it rests directly upon the mantle in the thinning domain the moho slope is at least 13 and the continental crust thickness decreases seaward from 22 to 11 km over a 35 km distance stretched by a factor of 1 5 to 3 in the oceanic domain a two layer high gradient igneous crust 5 3 6 0 km s 6 5 7 4 km s was modeled the intra crustal interface correlates with prominent mid basement 10 15 km long reflections in the multi channel seismic profile strong secondary reflected pmp phases require a first order discontinuity at the moho the sedimentary cover can be as thick as 5 km and the igneous crustal thickness varies from 4 to 11 km in the west where the profile reaches the madeira tore rise in the transitional domain the crust has a complex structure that varies both horizontally and vertically beneath the continental slope it includes exhumed continental crust 6 15 6 45 km s strong diffractions were modeled to originate at the lower interface of this layer the western segment of this transitional domain is highly reflective at all levels probably due to dykes and sills according to the high apparent susceptibility and density modeled at this location sub moho mantle velocity is found to be 8 0 km s but velocities smaller than 8 0 km s confined to short segments are not excluded by the data strong p wave wide angle reflections are modeled to originate at depth of 20 km within the lithospheric mantle under the eastern segment of the oceanic domain or even deeper at the transitional domain suggesting a layered structure for the lithospheric mantle both interface depths and velocities of the continental section are in good agreement to the conjugate newfoundland margin a 40 km wide oct having a geophysical signature distinct from the oct to the north favors a two pulse continental breakup

a mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer abstract a new and efficient mini slug test method for the determination of local hydraulic conductivities in unconfined sandy aquifers is developed the slug test is performed in a small diameter 1 inch driven well with a 0 25 m screen just above the drive point the screened drive point can be driven from level to level and thereby establish vertical profiles of the hydraulic conductivity the head data from the test well are recorded with a 10 mm pressure transducer and the initial head difference required is established by a small vacuum pump the method described has provided 274 spatially distributed measurements of a local hydraulic conductivity at a tracer test site at vejen denmark the mini slug test results calculated by a modified dax slug test analysing method applying the elastic storativity in the dax equations instead of the specific yield are in good accordance with the results from two natural gradient tracer experiments performed at the test site the original dax the bouwer and rice and the chirlin analysing methods all led to an underestimation of the effective hydraulic conductivity by a factor of more than 2 when compared with the tracer tests in contrast the spherical flow model of karasaki et al overestimated the results of the tracer tests by approximately a factor 1 4 the dax and the cooper et al methods assuming only radial flow to the partially screened well yielded a better approximation of the horizontal hydraulic conductivity than the chirlin method which also considers axial flow this fact is suggested to be a result of aquifer anisotropy as a significant higher horizontal than vertical hydraulic conductivity may suppress the significance of the axial flow component