semi numerical simulation of groundwater flow induced by periodic forcing with a case study at an island aquifer summary this paper presents an efficient method to analyze the aquifer response to periodic forcing a complex transformation is used to change the time dependent linear aquifer model into an equivalent time independent problem of a complex function referred to as the complex amplitude hereafter the magnitude of the complex amplitude represents the amplitude of the sinusoidal fluctuation of the groundwater level and the argument of the complex amplitude the phase shift of the fluctuation different iterative methods can be used to obtain the numerical solution a semi analytical numerical solution of the groundwater level which is numerical for the spatial variables and analytical for the time variable can be obtained by implementing a simple inverse complex transform to the complex amplitude the advantages of the time independent method include ruling out of initial conditions direct outputs of the amplitude and phase shift of different sinusoidal components of the water level fluctuations on the contrary the numerical solutions of the time dependent model need further computational efforts for the analyses of the amplitudes and phase shifts of different sinusoidal components and have to consider an initial condition whose impacts on the periodicity have to be eliminated by running sufficiently great number of tidal circles a case study at an unconfined aquifer formed by fill materials near lam chau island hong kong sar pr china shows the applicability of the semi numerical solution to analyze tide induced watertable fluctuations the aquifer parameters were estimated by minimizing a least squares objective function to fit the complex amplitude of semidiurnal and diurnal components of the observed water level fluctuations compared with the parameter estimations of some of the previous analytical solutions the numerical method gives not only better fitting to the water level observations but also more aquifer parameters

numerical modeling of tidal effects on groundwater dynamics in a multi layered estuary aquifer system using equivalent tidal loading boundary condition case study in zhanjiang china this paper presents a numerical modeling study of tidal effects on groundwater dynamics of a multi layered estuary aquifer system in this study to generalize the tidal loading effects on the confined aquifer we used equivalent tidal loading boundary condition based on existing analytical solutions for the confined aquifer in a three dimensional numerical model and then good simulated result was obtained using the numerical model the tide induced groundwater level and confined groundwater discharge dynamics were discussed and the following conclusions were obtained the combined action of sea tide and river tide can enhance the tidal response of groundwater level in the aquifer system especially for the confined groundwater the river tidal effect is more significant in the areas away from coastline although the confined aquifer is separated by a layer of clay from the ocean because of the tidal loading effects the confined groundwater discharge also changes periodically displaying a negative correlation with the tide level fluctuations like the unconfined groundwater discharge using linear functions that express the relationship between the mean confined groundwater flux and sea tide level the confined groundwater flux through the tidal loading boundaries can be approximately estimated when the sea tide level is higher than 4 4 m there would be a risk of seawater intrusion into the confined aquifer in the study area this case study is useful for numerical studying of tidal effects on groundwater resource dynamics in a coastal multi layered estuary aquifer system

tide induced groundwater head fluctuation in a coastal aquifer system with a submarine outcrop covered by a thin silt layer we present an analytical solution of groundwater head response to tidal fluctuation in a coastal multilayered aquifer system consisting of an unconfined aquifer a leaky confined aquifer and a semi permeable layer between them the submarine outcrop of the confined aquifer is covered by a thin silt layer a mathematical model and the analytical solution of this model are given the silt layer reduces the amplitude of the hydraulic head fluctuation by a constant factor and shifts the phase by a positive constant time lag both of which depend on the leakances of the silt layer and the semi permeable layer the time lag is less than 1 5 h and 3 0 h for semi diurnal and diurnal sea tides respectively when the leakance of the semi permeable layer or the silt layer assumes certain special values the solution becomes the existing solutions derived by previous researchers the amplitude of the hydraulic head fluctuation in the confined aquifer increases with the leakance of the silt layer and decreases with the leakance of the semi permeable layer whereas the phase shift of the fluctuation decreases with both of them a hypothetical example shows that neglecting the silt layer may result in significant parameter estimation discrepancy between the amplitude attenuation and the time lag fittings copyright 2007 john wiley sons ltd

tide induced head fluctuations in a confined aquifer with sediment covering its outlet at the sea floor 1 a confined coastal aquifer usually extends under the sea for some distance with its submarine outlet covered by a thin layer of sediment with properties dissimilar from the aquifer previous theoretical studies neglected this outlet capping in this paper an analytical solution is derived for a confined aquifer subject to tidal fluctuations with a leaky boundary condition at the outlet capping for the cases that offshore length of the aquifer and or the leakance of the outlet capping are either zero or infinity existing solutions in literature are obtained it is shown that our analytical solution can also be used to describe the tidal wave propagation in a confined aquifer extending infinitely under a tidal river the full solution agreed well with the observations in a piezometer in the jahe river basin in china 200 m inland from the coastline where the tide induced head fluctuations without delay were observed but cannot be explained using previous analytical and numerical solutions ignoring the effect of the outlet capping the sensitivity analysis showed that the combined actions of the tidal loading and outlet capping lead to complex dependency of the head fluctuation on the outlet capping s leakance when the offshore confined aquifer is short the inland head fluctuation increases with the outlet capping s leakance in this case significant negative phase shift occurs if the leakance is small for offshore aquifer length greater than a threshold value the inland head fluctuations are independent of this length and the outlet capping s leakance

a deep seismic sounding investigation of lithospheric heterogeneity and anisotropy beneath the iberian peninsula abstract the dimensions of the iberian peninsula the facility of firing large charges in the surrounding waters the well known and relatively uniform geology and prior knowledge of the crustal structure resulted in it being chosen as a study area for the investigation of the seismic structure of the lower lithosphere via refraction wide angle reflection seismic profiling the iberian lithosphere heterogeneity and anisotropy experiment iliha with a star shaped arrangement of six long range dss profiles was carried out in october 1989 the models derived from a first interpretation of the recorded data are presented three crustal profiles cover the same western and central part of the hercynian massif as the mantle profiles the resulting interpretations all include a middle as well as a lower crustal layer above the mantle the velocities of the layers in all three models are similar however the layer depths vary beneath the profiles interpretation of the mantle derived data suggests a layered lower lithosphere one reversed line and an intersecting unreversed line indicate the layering penetrates to at least 90 km depth the homogeneity of these layers contrasts strongly with the heterogeneous hercynian surface geology velocities derived from reflected data from the deep layers suggest the constituent materials are either anisotropic or that the layers suffer a slight regional dip

deep structure of fennoscandia from fundamental and higher mode dispersion of rayleigh waves abstract surface wave dispersion for the baltic shield area has been investigated through analysis of phase velocities up to periods of about 250 s for the fundamental rayleigh mode and about 80 s for the first two higher modes this has enabled investigation of the lithosphere asthenosphere system and deeper regions down to about 400 km the shear wave velocitydepth relationship obtained from the inversion of dispersion data for the paths cop kev cop krk can be considered as representative of an average model for the baltic shield moreover the inversion of dispersion data supplemented by previous results from the scandinavian area suggest the presence of significant lateral heterogeneity down to depths of about 350 km moving from the older precambrian shield cop kev cop krk to the peripheral area nur cop models with small if any differences in average shear velocity are consistent with the data in the depth range 350 450 km for the regions studied

tide induced ground water flow in deep confined aquifer water elevation variation in rivers can be large due to tides even far away from the coastline for deep confined aquifers the possibility of leakage from rivers is small nevertheless the fluctuation of river elevation can induce a stress change in soil and in turn can induce ground water flow below the present study focuses on the effect of the fluctuation assuming the time scale for consolidation is much larger than that of the ground water the total stress change in the deep confined aquifer affects the water pressure head through deformable soil medium if the subsurface profile contains only one dominant confined aquifer a vertically averaged one dimensional problem with periodic total stress change and constant line pumping is examined the governing equation is a linear diffusion equation with time varying forcing terms laplace transform and fourier transform are invoked the response distribution in space is of the error function type the pumping effect can be superimposed due to linearity away from the loading deeper aquifers rather than those close to the ground surface are affected by the dynamic loading pressure peaks appear earlier for location farther away from the loading field data support the model

impacts of evaporation on subsurface flow and salt accumulation in a tidally influenced beach we coupled a mass transfer formulation of evaporation to the density dependent variably saturated finite element model marun to predict the salinity under realistic conditions in a beach in the gulf of mexico the results showed that evaporation almost doubled the pore water salt concentration in the intertidal zone in comparison to the case with no evaporation the results also showed that for the relatively wet atmospheric conditions the maximum evaporation did not occur from the supratidal zone rather from the intertidal zone and it was due to the difference in moisture between pore water and atmosphere the highest salinity occurred during the spring tide period and extended into the neap tide period when the atmospheric condition was assumed to be constant and conducive to large evaporation high temperature and low air humidity the maximum salinity region shifted to the supratidal zone and persisted there due to low mixing the maximum salinity value in the intertidal zone for this case was not larger than that of the variable atmospheric condition case however the maximum was more landward than the more realistic variable atmospheric condition case which suggests that accurate characterization of pore water salinity in tidally influenced beaches requires accurate knowledge of atmospheric conditions in addition to beach and hydraulic properties the constant atmospheric condition simulations suggest that antecedent extreme conditions greatly affect the salinity in the supratidal zone but they are dampened in the intertidal zone

tidal groundwater level fluctuations in l shaped leaky coastal aquifer system this paper presents an analytical solution to describe tidal groundwater level fluctuations in a coastal leaky aquifer system bounded by water land boundaries that form a right angle referred to as l shaped coastlines the system consists of an unconfined aquifer a confined aquifer and a leaky layer between them previously published analytical solutions that discuss only single aquifer constitute a special case of the new solution when the permeability of leaky layer approaches zero a simple approximate solution without integral is presented error analysis and hypothetical example show that the approximate solution has adequate accuracy for both groundwater level prediction and parameter estimation for an l shaped leaky aquifer system q 2002 elsevier science b v all rights reserved

high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield

a two dimensional analytical solution for groundwater flow in a leaky confined aquifer system near open tidal water groundwater in coastal areas is commonly disturbed by tidal fluctuations a two dimensional analytical solution is derived to describe the groundwater fluctuation in a leaky confined aquifer system near open tidal water under the assumption that the groundwater head in the confined aquifer fluctuates in response to sea tide whereas that of the overlying unconfined aquifer remains constant the analytical solution presented here is an extension of the solution by sun for two dimensional groundwater flow in a confined aquifer and the solution by jiao and tang for onedimensional groundwater flow in a leaky confined aquifer the analytical solution is compared with a two dimensional finite difference solution on the basis of the analytical solution the groundwater head distribution in a leaky confined aquifer in response to tidal boundaries is examined and the influence of leakage on groundwater fluctuation is discussed copyright 2001 john wiley sons ltd

tidal dynamics of the water table in beaches tidal motions of the water table height inside a sloping beach are investigated via field measurements and theoretical considerations only the movements forced by the tide are considered so a beach with negligible wave activity was chosen for the field measurements the data show that even in the absence of precipitation the time averaged inland water table stands considerably above the mean sea level also the water table at a fixed point inside the beach is far from sinusoidal even though its variation is forced by an essentially sinusoidal tide this latter effect is due to the boundary condition along the sloping beach face which acts as a highly nonlinear filter the observed behavior of the water table is explained in terms of perturbation extensions to the classical deep aquifer solution one extension deals with the nonlinearity in the interior the other with the boundary condition at the sloping beach face

recording marine airgun shots at offsets between 300 and 700 km this paper demonstrates that under favorable conditions by using multichannel recording and subsequent stacking of adjacent records marine airgun shots have been detected at offset distances up

a two dimensional analytical solution of groundwater response to tidal loading in an estuary a two dimensional transient groundwater flow equation for a confined nonleaky aquifer is solved analytically with an estuary tidal loading boundary condition the amplitude and phase of the tide varies with position and time respectively these variations called the damping coefficient for amplitude and separation constant for phase along the coastline are considered in the analysis the solution presented is more advanced than the traditional one dimensional analytical solution with a one dimensional tidal loading boundary condition the damping coefficient and separation constant in the application study are obtained from the harmonic analysis of the observed tidal level in apalachicola bay florida the analytical solution is compared to a two dimensional finite difference solution a numerical simulation illustrates the response of piezometric head to tidal loading the piezometric head and phase from both solutions match closely the analytical and numerical solutions show that a piezometric head along both sides of the estuary can be predicted given a tidal elevation at the entry of an estuary the fluctuation of piezometric head in response to tidal loading diminishes rapidly inland and diminishes slowly along the coastline of an estuary there are also obvious phase shifts associated with spatial variations as the wave propagates

heterogeneity in the mantle its creation evolution and destruction abstract small scale seismic heterogeneity exists at different levels in the lower mantle and is detected by methods that analyze scattered not direct energy from natural and artificial sources its vertical distribution association with subduction and its 10 km characteristic scale length strongly suggest that it is chemical petrological in nature and originally created by melting and differentiation during mid ocean ridge formation what is of interest is that the scale lengths of both upper and lower mantle seismic heterogeneity are similar which supports the view of a common origin explored here unlike the lower mantle however which is broadly homogeneous in structure the upper mantle contains things that trap and impede the dispersal and re mixing of heterogeneity continental crust lithosphere and cratonic roots these probably control the depths the longevity and the age of heterogeneities at shallow mantle levels and suggest that heterogeneities observed in continental mantle lithosphere are probably old trapped by the process that grows continental roots alternatively if crustal heterogeneity is controlled by the details of a magmatic process it must either be somehow continually renewed for which there is no recognizable surface expression or it must be depleted over time and the present is a time when by luck we may still witness it

crustal structure and composition of the oslo graben norway abstract although more than 250 my old the oslo graben has retained a distinctive distribution of p wave velocities associated with rifting intrusion and underplating of the thinned crustal section we calculate poisson s ratio values from crustal p and s wave velocities along an 400 km long profile across the southern scandinavian peninsula with a focus on the oslo graben plutonic rocks are now exposed at the surface in the graben due to post rifting erosion and the corresponding low 5 5 km s p wave velocities extend to depths of 3 km the p wave velocity and poisson s ratio between depths of 6 and 34 km are 5 higher inside than outside the rift boundaries which together with thickening of the 7 km s lower crust beneath the rift indicate magmatic intrusions poisson s ratio of 0 27 and high 7 1 7 4 km s velocities indicate a heterogeneous composition lower crust the thickened high velocity lower crust is 1 5 times wider than the surface expression of the rift and extends to both the east and west of the main rift axis depth dependant extension may have occurred within the rift and may account for the significant volumes of volcanic output despite the small surface extension observed the added volume of intrusive material may explain why the moho up warp is small as little as 2 km at the rift based on the new p wave velocities poisson s ratio measurements and the thickness of the magmatic underplate apparent values for the rift are estimated to be 1 5 but when intrusion within the crust is included could be as high at 2 3

scales of heterogeneities in the continental crust and upper mantle a seismological characterization of crust and upper mantle can refer to large scale averages of seismic velocities or to fluctuations of elastic parameters large is understood here relative to the wavelength used to probe the earth in this paper we try to characterize crust and upper mantle by the fluctuations in media properties rather than by their average velocities as such it becomes evident that different scales of heterogeneities prevail in different layers of crust and mantle although we cannot provide final models and an explanation of why these different scales exist we believe that scales of inhomogeneities carry significant information regarding the tectonic processes that have affected the lower crust the lithospheric and the sublithospheric upper mantle we focus on four different types of small scale inhomogeneities 1 the characteristics of the lower crust 2 velocity fluctuations in the uppermost mantle 3 scattering in the lowermost lithosphere and on 4 heterogeneities in the mantle transition zone

deep seismic probing of the continents and their margins abstract application of deep seismic methods to studies of the crust and lithospheric mantle receives considerable interest and the methods are constantly refined and new methods are developed which allows the extension of studies to new subjects and regions deep seismic methods are applied to a long range of geoscientific subjects in research on the formation and development of crust and lithosphere in continental and oceanic environments from being an experimental discipline some 30 40 years ago a series of methods can now be applied almost routinely to research on the lithosphere however in many applications the methods are used up to their limits at the present technological state therefore development of methods has high priority in the seismic community this volume provides an overview of recent development of deep seismic techniques and their application to the imaging and probing of the continents and their margins

resolving a low velocity zone with surface wave data summary the main purpose of seismic inversion is the retrieval of seismic velocities and densities in the earth inversion of body wave traveltimes cannot uniquely determine the seismic velocities as a function of depth when a low velocity layer is present it is generally assumed that surface waves do not suffer from the same non uniqueness the issue is addressed whether it is possible to remove the non uniqueness of traveltime inversions with a realistic set of surface wave data this requires the exact determination of the velocity distribution within and around the low velocity zone waveforms phase velocities as well as group velocities are investigated qualitatively synthetic love wave phase and group velocities are actually inverted waveforms are shown to be sensitive to the exact velocity distribution of a low velocity layer but it is concluded that the removal of the non uniqueness with the use of waveforms is difficult because the differences of the waveforms are generally small and because complications such as lateral heterogeneity and poorly known source parameters reduce the accuracy of waveform inversions the inversions of love phase and group velocities indicate that it is difficult to determine the velocity distribution of a low velocity layer in a statistically significant way with a realistic set of dispersion data group velocities are shown to be more sensitive to the low velocity structure than phase velocities unfortunately group velocity data suffers from a practical non uniqueness because in general only fundamental mode group velocities can be measured it is concluded that the non uniqueness in the detailed structure caused by a low velocity layer cannot readily be resolved by using surface wave dispersion data

2 d image of seismic attenuation beneath the deep seismic sounding profile quartz russia we present a 2 d image of the upper mantle attenuation using nuclear explosion data from the ultra long refraction reflection profile quartz our analysis is based on a modified common spectrum technique followed by least squares inversion for q and iterative ray tracing in the velocity structure obtained earlier the resulting attenuation structure corroborates the earlier model for northern eurasia as well as our recent estimate based on the analysis of the long range p n phase and provides significantly more detail than the existing models the resulting upper mantle attenuation structure is characterised by q values ranging from 400 to 1800 down to the depths of 150 190 and probably 400 km the attenuation increases horizontally in se direction away from the baltic shield our model exhibits strong 2 d vertical and horizontal attenuation contrasts a high attenuation layer in the depth range of 120 150 to 160 180 km can apparently be associated with the presence of a partial melts within the base of the lithosphere

lower lithospheric structure beneath the trans european suture zone from polonaise 97 seismic profiles abstract the large scale polonaise 97 seismic experiment investigated the velocity structure of the lithosphere in the trans european suture zone tesz region between the precambrian east european craton eec and palaeozoic platform pp in the area of the polish basin the p wave velocity is very low vp 8 25 km s in the palaeozoic platform and 8 1 km s in the precambrian platform good quality record sections were obtained to the longest offsets of about 600 km from the shot points with clear first arrivals and later phases of waves reflected refracted in the lower lithosphere two dimensional interpretation of the reversed system of travel times constrains a series of reflectors in the depth range of 50 90 km a seismic reflector appears as a general feature at around 10 km depth below moho in the area independent of the actual depth to the moho and sub moho seismic velocity ringing reflections are explained by relatively small scale heterogeneities beneath the depth interval from 90 to 110 km qualitative interpretation of the observed wave field shows a differentiation of the reflectivity in the lower lithosphere the seismic reflectivity of the uppermost mantle is stronger beneath the palaeozoic platform and tesz than the east european platform the deepest interpreted seismic reflector with zone of high reflectivity may mark a change in upper mantle structure from an upper zone characterised by seismic scatterers of small vertical dimension to a lower zone with vertically larger seismic scatterers possible caused by inclusions of partial melt

frequency dependence of q in the mantle underlying the shield areas of eurasia part iii the q model summary a large set of teleseismic body wave data covering a broad range in frequency was analysed to determine the frequency arid depth dependence of q for p and s waves under the northern shield areas of eurasia based on numerous f estimates for p and s waves covering the seismic band between 0 02 and 8 hz a q model of the eurasian shield was constructed the data require a model in which q increases with frequency and which is characterized by q values in the upper mantle that are generally higher than those of global average models the model with the best fit includes a minimum in q between about 100 and 200 km depth and high q values on the order of thousands throughout most of the deeper mantle these results are generally consistent with proposed models of attenuation as a thermally activated process which is influenced by the temperature and pressure in the earth preliminary results suggest that t under tectonic regions is higher than t under shield regions for all frequencies over the 0 02 to 8 hz frequency range suggesting that q varies regionally as well as with frequency and depth

seismic models of the lower lithosphere beneath the southern baltic sea between sweden and poland abstract based on recordings from the northern part of the baltic sea black sea profile and eugeno s profile 4 2 d seismic models have been constructed for a profile across the southwestern part of the east european platform from southern sweden to northern poland the thickness of the crust along the profile varies from 33 to 47 km the moho p wave velocity is 8 0 8 3 km s the uppermost mantle has a fine structure with alternating layers of higher and lower velocities down to a depth of about 120 km three alternating high and low velocity layers have been modelled the velocities vary between 8 2 and 8 7 km s in the high velocity layers and 8 0 and 8 5 km s in the low velocity layers a tendency of the depth of the moho and the depth of the uppermost mantle seismic boundaries to increase towards the southeast is observed

analysis of waves converted from s to p in the upper mantle beneath the baltic shield teleseismic data recorded by broadband stations of the swedish national seismic network have been used in a study of waves converted from s to p in the uppermost mantle s to p converted waves are recorded as precursors to the direct s arrival this enables us to study seismic discontinuities at depths of 100 300 km where the traditional receiver function technique based on p to s conversion fails due to disturbances from crustal reverberations clear signals of s to p conversion are seen for several horizons in the 50 200 km depth range this is interpreted as a layered lithosphere with alternating high and low velocity bodies a sharp contrast is imaged at depths around 160 km and continuous for almost 1000 km in the southern part of the profile this structure coincides with the velocity contrast interpreted by several authors as the lower limit of a prominent low velocity zone in the 95 to 160 km depth range a feature which we identify as the lithosphere asthenosphere boundary is clearly imaged at depths around 200 km

a new model of upper mantle p wave velocity below the baltic shield indication of partial melt in the 95 to 160 km depth range abstract the subcrustal mantle to about a depth of 160 km below the baltic shield can be divided seismically into two main intervals the upper interval between ca 45 and 100 km is characterized by refracted waves with velocities between 8 0 and 8 6 km s interpreted as a sandwich layered model of intermixed high and low velocity layers the lower interval is a ca 40 km thick zone of relatively low average velocity at a depth increasing from 95 km in the southern part to 120 km in the northern part of the shield seismic sections show that isolated bodies in this interval generate scattered reflections with substantial amplitude variation over short distance the maximum velocity difference at the reflectors is 1 0 km s which is larger than in the upper main interval our model is based on a general gap in correlation of seismic arrivals at offsets between 800 and 1100 km at larger offsets we observe continuous linear first arrivals indicating a relatively homogenous layer of high 8 6 km s velocity below a depth of 160 km petrologically the lower reflective interval is explained by partially melted small bodies with patches of carbonatitic or kimberlitic magma of horizontal extent less than 20 km this new model of the upper mantle is based on seismic data from the baltic shield and there is clear indication that it is equally valid for other shield and platform areas

test of the upper mantle low velocity layer in siberia with surface waves abstract the existence of the upper mantle low velocity layer lvl below 100 km depth in cratonic areas is tested with surface waves dispersion curves given the ambient noise we find that a pronounced lvl 80 km thick and 2 velocity reduction or 40 km thick and 5 velocity reduction can be distinguished from a constant velocity model by comparison of the fundamental mode group velocities whereas a thin lvl less than 40 km thick with small velocity contrast less than 2 cannot be resolved the fundamental modes of love and rayleigh waves have similar properties and in general the phase velocity differences are smaller than the standard error phase velocity alone cannot discriminate between the models and the group velocity is in general more sensitive to the velocity structure than the phase velocity the higher modes at short periods could potentially determine a lvl but in reality it is difficult to obtain sufficiently accurate measurements we invert the synthetic dispersion curves by the non linear hedgehog inversion method a pronounced lvl more than 40 km thick and with a strong velocity contrast of about 5 is detectable by the non linear inversion but for a thin lvl with a strong velocity contrast it is not possible to resolve both velocity and thickness in the inversions all solutions include a lvl for models with a pronounced lvl whereas the solution space includes models with and without a lvl for models with a zero or positive gradient velocity depth structure we invert also real data with travel path across the siberian craton with the hedgehog method almost all solutions include a lvl in the depth range of 80 150 km with a velocity contrast up to 2 to the surrounding intervals hence the lvl appears to be a common feature of the siberian upper mantle although a constant velocity at the same depth range cannot be totally excluded despite low resolution at large depth a pronounced asthenospheric lvl below a depth of about 225 km is a constant characteristic of the set of solutions

the deep structure of the scandes and its relation to tectonic history and present day topography abstract we review the results of the toposcandiadeep project a component of the topoeurope project in which we have studied the crustal and upper mantle structures of southern norway in relation to its high topography the scandinavian mountain chain the scandes is an intracontinental mountain chain at the western edge of the baltic shield and has its southern part located in southern norway the timing as well as the processes causing the formation of the scandes are disputed we bring new geophysical constraints to this issue by providing crustal and mantle seismic models for the area and by integrated modeling of the lithosphere and its potential deformation new maps of moho depth and crustal seismic velocities have been compiled using data from refraction lines p receiver functions and noise cross correlation these results show a thickening of the crust from southwest to northeast and a small crustal root not directly located below the topographic high p s and surface wave tomography infer seismic mantle velocities lower than in normal shield structure with a possible sharp boundary close to the oslo graben these low velocities are imaged in the lithosphere and in the underlying mantle down to the 410 km discontinuity integrated modeling of seismic models and gravity data shows that the low velocities below southern norway are compatible with a change in lithosphere thickness from c 100 km under southern norway to nearly 200 km under southern sweden with possible additional differences in composition the study also indicates that the topography can be isostatically sustained by the density distribution in the crust and lithospheric mantle we argue that the lithospheric lateral variation has been present for at least 300 my and has had a significant influence on the localization of the topography independently of the mechanism for uplift

application of genetic algorithm technique to inverse modeling of tide aquifer interaction modeling of tide aquifer interaction plays a vital role in the management of coastal aquifer systems a novel and robust methodology is presented in this paper for estimating aquifer parameters of coastal aquifers from tide aquifer interaction data using tide aquifer interaction model and genetic algorithm ga two stand alone computer programs were developed to optimize hydraulic diffusivities of unconfined and confined coastal aquifers at multiple sites using ga technique and tide aquifer interaction model and considering two approaches lumped tidal component approach and multi tidal component approach five sets of real world tide aquifer interaction data at two sites of an unconfined aquifer and one set of tide aquifer interaction data at three sites of a confined aquifer were used to demonstrate the efficacy of the methodology the analysis of the ga based inverse modeling results indicated that the multi tidal component approach yields more accurate and reliable hydraulic diffusivities for the unconfined aquifer rmse 0 0129 0 0521 m nse 0 70 0 97 and d1 0 91 0 99 as well as for the confined aquifer rmse 0 0204 0 0545 m nse 0 95 0 97 and d1 0 99 compared with the lumped tidal component approach a comparative evaluation of data size revealed that the short duration datasets of the unconfined aquifer provide more reliable estimate of hydraulic diffusivity than the long duration datasets further it was found that the spring and neap tidal data yield unreasonable values of hydraulic diffusivity with considerably high values of rmse and very low values of r 2 nse and d1 thereby suggesting that spring and neap tidal data are not suitable for aquifer parameter estimation overall it is concluded that the ga based tide aquifer interaction model following multi tidal component approach is the most efficient tool for estimating aquifer parameters of unconfined and confined aquifers from tide aquifer interaction data the developed methodology is also applicable to other coastal basins of the world irrespective of hydrogeological settings

upper mantle models and the thickness of the continental lithosphere summary analysis of the early rise traveltimes in the united states shows that on several of the profiles there are features which can be interpreted as indicating a low velocity zone above 200km i e that the continental lithosphere thickness is less than 200 km the explosion data from the nevada test site gnome and early rise are all consistent with lehmann s suggestion that there is a discontinuity at a depth of about 200 km comparison of the observed data between 15 and 23 with model calculations shows that the major differences between the western and centraleastern united states upper mantles occur above 200 km it appears that the only reasonable explanation for the 200 km discontinuity is that it represents the termination of a zone of partial melting

observations of the electrical asthenosphere beneath scandinavia the recent recognition that long period i e of the order of hours electromagnetic induction studies could play a major role in the detection of the asthenosphere has led to much interest amongst the geophysical and geological communities of the geomagnetic response functions derived for differing tectonic environments experiments carried out on the ocean bottom have met with considerable success in delineating the electrical asthenosphere i e a local maximum in electrical conductivity minimum in electrical resistivity in the upper mantle in this paper observations of the time varying magnetic field recorded in three regions of scandinavia northern sweden kiruna kir northern finland northeastern norway kevo kev and southern finland sauvamaki sau are analysed in order to obtain estimates of the inductive response function c for each region the estimated response functions are compared with one from the centre of the east european platform eep and it is shown that the induced eddy currents at periods of the order of 103 104 s in the three regions flow much closer to the surface than under the platform centre specifically at a period of 3000 s these currents are flowing at depths of the order of kev 120 km kir 180 km sau 210 km eep 280 km implying that the transition to a conducting zone of 0 2 s m occurs at around these depths one dimensional inversion of ckev and ckir shows that there must exist a good conducting zone of 0 1 1 0 s m under each of the two regions of 40 km minimum thickness at depths of kev 105 115 km kir 160 185 km this is to be contrasted with eep where the d profile displays a monotonically decreasing resistivity with depth reaching 0 1 s m at 300 km finally a possible temperature range for the asthenosphere consistent with the deduced conducvitity is discussed it is shown that at present there is insufficient knowledge of the conditions water content melt fraction etc likely to prevail in the asthenosphere to narrow down the probable range of 900 1500 c

numerical simulation of the effect of the sloping submarine outlet capping on tidal groundwater head fluctuation in confined coastal aquifers the submarine outlet of a coastal confined aquifer is usually covered by less permeable material such as silt and fine sand which forms a sloping or almost flat seabed previous analytical studies of the tide induced head fluctuation usually assumed a vertical interface between the outlet capping and the seawater and neglected the effects of the outlet capping s slope here we conducted a series of numerical simulations to investigate the effect of the slope of the outlet capping on the tide induced head fluctuations in a coastal confined aquifer the numerical simulations demonstrated that when the hydraulic diffusivity slope and or the outlet capping leakance are large the tidal loading effect is relatively weak and the leakance dominates in this case the analytical solution applies in general the joint actions of the outlet capping leakance and the tidal loading effects result in complicated 2 dimensional flow in the aquifer near the shoreline for aquifers with small hydraulic diffusivity small slope and or small outlet capping leakance the outlet acts approximately as a no flow boundary condition and the tidal loading dominates in this case negative phase shifts time advance may occur near the coastline the study provides potential guide to infer the aquifer s submarine structure and parameter from tidal head fluctuation observations in inland wells

an analytical solution and case study of groundwater head response to dual tide in an island leaky confined aquifer 1 this paper presents an analytical solution of groundwater head response to dual tide fluctuation in the transect of an island leaky aquifer system comprising a confined aquifer and its overlying semipermeable confining layer both layers terminate at the coastlines on two sides of the island solution analysis indicates that the tidal waves from the two sides of the island transect interfere at the middle of the island and the interference decreases to zero as the horizontal length of the aquifer increases to infinity the leakage of the overlying confining layer enhances the landward attenuation of the tidal head fluctuation and shortens the time lag between the head and tide fluctuations the solution agreed well with the observations in eight piezometers in garden island on the continental shelf of western australia reported by trefry and bekele 2004

results of lithospheric studies from long range profiles in siberia several long range seismic profiles obtained during the last ten years in siberia show the complicated lithospheric structure of the siberian platforms the three component observations conducted at distances up to 3000 km made it possible to obtain information on p and s velocities in the crust on p velocity and q factor for the upper mantle and on the seismic boundaries responsible for reflected refracted and converted waves down to a depth of 400 700 km the crustal models are typical of old platforms of eurasia the average thickness of 40 km three layers with p velocities 6 2 6 5 7 0 km s and thicknesses of 10 15 km are distinguished the depth to the m discontinuity varies from 45 50 km beneath the old tunguss depression to 35 40 km beneath the younger vilyui basin the most complicated moho structure is observed in the boundary between the west siberian and the siberian platforms a strong inhomogeneity of p velocity models was revealed for the upper mantle the horizontal inhomogeneities are more larger in the uppermost mantle to depths of 80 100 km where p velocities vary from 8 0 8 2 km s beneath the young west siberian plate to 8 4 8 6 km s beneath some blocks of the siberian craton the fine vertical inhomogeneity was studied with reflections correlated after computer processing of seismograms they outlined several low velocity layers 20 50 km thick the layers were characterized by low q as well intensive waves were recorded from the transition zone between the upper and lower mantle the top of the zone is nearly horizontal in the area its depth is 400 25 km the bottom of the zone lies at about 700 km

tide induced groundwater level fluctuation in a u shaped coastal aquifer summary the prediction of groundwater level fluctuation due to tidal waves propagation in coastal aquifers is important for the planning and management of water resources in coastal areas a two dimensional 2 d analytical solution is derived to describe the tidal groundwater fluctuation in an aquifer bounded by three water land boundaries that form a u shaped coastline two opposite sides represent estuary land boundaries on which the amplitude attenuation and phase shift of the tidal movement in the estuary are considered while the third side is an ocean land boundary the effects of wave interaction due to the propagation of oscillating oceanic tides in the cross shore direction inland and the transmission of the two opposite estuarine tides in the along shore direction are investigated three existing head fluctuation solutions can be considered as special cases of the present solution one is for one dimensional flow and the other two are for 2 d flow a transition distance ranging from 10 to 15 times of tidal propagation length along the shoreline can be estimated based on the solution this distance can be used to judge whether the interaction among tides is significant the influences of hydraulic properties on the tidal fluctuations within the aquifer can therefore be assessed quantitatively based on sensitivity analyses one can conclude that the tidal head is most sensitive to the transmissivity and storativity of the aquifer and least to the damping coefficient of tidal amplitude and wave number along the estuary the sensitivities of head fluctuation to the changes of transmissivity and storativity depend on the shoreline length and whether the interaction among waves is significant on the other hand the sensitivities of head fluctuation to the changes of damping coefficient and wave number increase with diagonal distance from the entry of estuary and reach the largest magnitude near the estuary far away seashore

upper mantle velocity structure beneath the siberian platform summary we present a new velocity model for the continental upper mantle beneath central siberia based on observations of the 1982 rift deep seismic sounding dss profile three peaceful nuclear explosions pne were detonated to provide energy for the 2600 km long profile that extends from the yamal peninsula to the mongolian border se of lake baikal in this paper we model seismic recordings from the northernmost explosion since data from that shot shows unambiguous arrivals from the mantle transition zone discontinuities the analysis combines forward traveltime modelling and waveform matching using reflectivity synthetic seismograms our model for the lithosphere has velocities of 8 25 8 20 km s from the moho to 117km depth between 117 and 123km depth a strong velocity gradient 8 30 8 53 km s is required while a moderate gradient 8 53 8 55 km s l exists between 123 and 136km depth a low velocity zone from 136 to 210km depth terminates this phase arrival branch the gradient again rises between 210 and 233 km and depth culminating in a high gradient zone 8 63 8 80 km s between 233 and 235 km depth below the high gradient zone more moderate gradient 8 80 8 85 km s is required from 235 to 253 km depth terminating in a zone of lower velocity 8 62 8 64 km s from 253 to 400 km depth the upper mantle transition zone consists of two high gradient zones separated by a more moderate gradient the upper zone is best modelled as a 35 km thick velocity gradient 8 64 9 45 km s from 400 to 435 km depth the existence of the velocity gradient is based on the observation that arrivals from this feature can be identified starting at 1580 km range and rapidly become prominent with increasing distance a model with a first order discontinuity predicts significant arrivals at ranges closer than 1580 km our observations contain no compelling evidence for a 520 km discontinuity although a small discontinuity cannot be ruled out the lower transitionzone discontinuity is modelled as a 4 km thick gradient zone 10 25 10 62 km s i from 655 to 659 km depth

groundwater response to tidal fluctuation in a two zone aquifer summary a coastal aquifer may consist of two zones of distinctly different hydraulic properties with the coastal zone of limited width and the inland zone of infinite width the analytical solutions for groundwater level response to tidal fluctuation in such a two zone aquifer are derived and the underlying physical meanings are discussed a dimensionless zone contrast parameter r is introduced which is controlled by ratio between the product of the transmissivity and storativity of the inland zone and that of the coastal zone in the coastal zone the amplitude of groundwater head fluctuation attenuates more quickly when r becomes greater the amplitude declines exponentially with distance from the coastline and the phase lag increases linearly only when r 1 in the inland zone however the head fluctuation always exhibits an exponential attenuation of the amplitude and a linear increase of the phase lag for any value of r thus the diffusivity of the inland zone can be readily assessed with measurements of fluctuation amplitudes or lags as are frequently used when estimating aquifer parameters in homogeneous aquifers compared with jacob 1950 solution for a semi infinite homogeneous aquifer the existence of the coastal zone reduces the amplitude in the inland zone by a spatially constant coefficient and increases the phase lag by a spatially constant shift inverse estimation of aquifer parameters are discussed based on the analytical solutions the analytical solutions are used to estimate the aquifer parameters in a coastal two zone aquifer located in the west part of dongzhai harbor hainan province china

upper mantle structure beneath southern african cratons from seismic finite frequency p and s body wave tomography abstract we present a 3d high resolution seismic model of the southern african cratonic region from teleseismic tomographic inversion of the p and s body wave dataset recorded by the southern african seismic experiment sase utilizing 3d sensitivity kernels we invert traveltime residuals of teleseismic body waves to calculate velocity anomalies in the upper mantle down to a 700 km depth with respect to the ak135 reference model various resolution tests allow evaluation of the extent of smearing effects and help defining the optimum inversion parameters i e damping and smoothness for regularizing the inversion calculations the fast lithospheric keels of the kaapvaal and zimbabwe cratons reach depths of 300 350 km and 200 250 km respectively the paleo orogenic limpopo belt is represented by negative velocity perturbations down to a depth of 250 km implying the presence of chemically fertile material with anomalously low wave speeds the bushveld complex has low velocity down to 150 km which is attributed to chemical modification of the cratonic mantle in the present model the finite frequency sensitivity kernels allow to resolve relatively small scale anomalies such as the colesberg magnetic lineament in the suture zone between the eastern and western blocks of the kaapvaal craton and a small northern block of the kaapvaal craton located between the limpopo belt and the bushveld complex

inferring time varying recharge from inverse analysis of long term water levels 1 water levels in aquifers typically vary in response to time varying rates of recharge suggesting the possibility of inferring time varying recharge rates on the basis of long term water level records presumably in the southwestern united states arizona nevada new mexico southern california and southern utah rates of mountain front recharge to alluvial aquifers depend on variations in precipitation rates due to known climate cycles such as the el nino southern oscillation index and the pacific decadal oscillation this investigation examined the inverse application of a one dimensional analytical model for periodic flow described by lloyd r townley in 1995 to estimate periodic recharge variations on the basis of variations in long term water level records using southwest aquifers as the case study time varying water level records at various locations along the flow line were obtained by simulation of forward models of synthetic basins with applied sinusoidal recharge of either a single period or composite of multiple periods of length similar to known climate cycles periodic water level components reconstructed using singular spectrum analysis ssa were used to calibrate the analytical model to estimate each recharge component the results demonstrated that periodic recharge estimates were most accurate in basins with nearly uniform transmissivity and the accuracy of the recharge estimates depends on monitoring well location a case study of the san pedro basin arizona is presented as an example of calibrating the analytical model to real data

two dimensional flow response to tidal fluctuation in a heterogeneous aquifer aquitard system in alluvial coastal aquifers finer sediments are preferentially deposited along the downstream direction so the hydraulic conductivity is generally heterogeneous and changes with distance from the coastline to investigate the influence of aquifer heterogeneity on seawater groundwater interaction a new two dimensional model characterising groundwater flow in an aquifer aquitard system was developed assuming that the hydraulic conductivity of the aquifer linearly increases with the distance from the coastline along the inland direction a closed form analytical solution was derived using the separation of variables method comparing the new solution with the numerical solution by comsol multiphysics sweden based on the finite element method one can see that the new solution agreed with the numerical solution very well except at the early time we found that both aquitard leakance and the heterogeneity factor b could result in the propagation bias the propagation bias represents the inconsistency between the theoretical calculation and the observed strong attenuation and small time lag between the head and tide fluctuations the attenuation decreased with perpendicular distance from the coastline x axis whereas the time lag increased with distance along the x axis the relationship between the time lag and the distance along the x axis seemed to be linear when b was 0 001 m 1 whereas it obeyed a power function when b was greater than 0 01 m 1 copyright 2014 john wiley sons ltd

mantle heterogeneities and their significance results from lithoprobe seismic reflection and refraction wide angle reflection studiesthis article is one of a series of papers published in this special issue on the theme lithoprobe parameters processes and the evolution of a continent lithoprobe contribution 1486 within lithoprobe s 10 transects data from more than 20 000 km of multichannel seismic mcs reflection profiling and 12 refraction wide angle reflection r war surveys were acquired while the

geostatistical inverse modeling of the transmissivity field of a heterogeneous alluvial aquifer under tidal influence summary the record of the head fluctuations of an alluvial aquifer connected to the estuary of a river submitted to tidal influence can be used to reconstruct the transmissivity field of the aquifer a markov chain monte carlo mcmc sampler is used to invert the transmissivity field at a set of pilot points our approach is first successfully benchmarked on a synthetic case study then we present a real case study in which both a semi confined aquifer and a shallow unconfined aquifer are connected to the estuary of the seine river in the western north of france these aquifers experience strong tidal variations up to 8 4 m this test site is equipped with a series of seventeen wells in which the temporal fluctuations of water heads associated with megatidal forcing were recorded during several years in addition to the use of the pilot points method a zoning parameterization with 45 zones is used to determine the vertical leakage coefficient from the semi confined aquifer into the shallow unconfined aquifer the distribution of the vertical leakage coefficient is determined by inverting the hydraulic head at a set of wells localized in the semi confined aquifer we determine jointly the distribution of the hydraulic transmissivity and the vertical leakage from the semi confined into the unconfined aquifer using 72 pilot points the storage coefficient is assumed to be constant over the whole domain its value is determined from three pumping tests that show a consistent value for this parameter log10s 5 and 0 11 as a variance in our approach there are 119 model parameters 72 transmissivity values at the pilot points 45 values of the vertical leakage coefficient and two parameters sill and range for the isotropic variogram the spatial distribution of the hydraulic transmissivity agrees qualitatively with the soil texture variations observed in the semi confined aquifer and core samples analysis

lithospheric thermal regimes in europe abstract the heat flow pattern of europe derived from more than 8000 observations is dominated by a general northeast to southwest increase in geothermal activity which is the consequence of the tectonic evolution of the whole continent this paper reviews the history of the geothermal mapping of europe and describes the recently compiled set of geothermal maps of europe surface heat flow is correlated with the age of the last tectonothermal event with the near surface heat production and with the crustal thickness deep temperature distributions within the crust lithosphere are calculated for 1 d 2 d and simple 3 d models characteristic temperature depth curves are given for some of the major tectonic provinces and the results of various techniques are compared the value of the crustal heat contribution is assessed and a regional moho heat flow pattern is proposed the mohorovicic discontinuity is clearly not an isothermal surface neither is the heat flow from below the crust constant

spatial and temporal deformation characteristics of marine alluvial deposits due to land reclamation implications from insar observation and geotechnical estimate ground deformation of reclaimed land is a key issue for reclamation design construction and sustainable development in coastal areas as this consolidation process of the underlying compressible marine sediment sequences over very long time periods could lead to damage of both ground constructions and underground facilities in this case study we have investigated the spatial and temporal characteristics of residual reclamation settlement of chek lap kok airport hong kong one of the largest land reclamation projects worldwide a total of 25 time series envisat asar datasets acquired between december 2003 and october 2008 were used to retrieve settlement rates and deformation history at high resolution and accuracy by means of advanced synthetic aperture radar interferometry insar the insar derived results show a fairly homogenous and stable pattern in the sectors of the airport site corresponding to the two original islands of chek lap kok and lam chau in contrast a relatively high spatial settlement variability ranging from moderate 3 7 mm yr to strong 10 mm yr settlement rates was discovered within the majority of the reclaimed portion of the airport a joint analysis of insar observations and geological materials indicates that the variability of the recorded residual settlement was highly correlated with the variations of thickness and pre consolidation state of alluvial deposits below the reclamation a quantitative comparison analysis also has been carried out between time series insar observations and theoretical estimates of residual settlement modelled by geotechnical investigations the results imply that a primary consolidation process in alluvial deposits below the reclamation might be delayed with respect to the predicted results and may still have been occurring in most reclaimed areas during the investigation period 2003 2008 the time to complete it could stretch to decades depending on hydraulic conductivity and natural drainage conditions copyright 2010 john wiley sons ltd

an analytical solution of groundwater response to tidal fluctuation in a leaky confined aquifer an analytical solution is derived to investigate the influence of leakage on tidal response in a coastal leaky confined aquifer system the analytical solution developed here is more general than the traditional solution obtained by ferris 1951 which can be regarded as a special case of the solution presented in this paper this solution is based on a conceptual model under the assumption that the groundwater level in the confined aquifer fluctuates in response to sea tide while that of the overlying unconfined aquifer remains constant this conceptual model is supported by numerous field studies by previous researchers which have demonstrated that the tidal response in an unconfined aquifer may be negligible compared to that in a confined aquifer the leakage has a significant impact on the tidal behavior of the confined aquifer hypothetical studies indicate that both tidal amplitude of groundwater head in the aquifer and the distance over which the aquifer can be disturbed by the sea tide will be considerably reduced because of the existence of leakage this analytical solution is used to investigate the tidal and piezometer data at the chek lap kok airport hong kong special administrative region people s republic of china

heterogeneity of the uppermost mantle beneath russian eurasia from the ultra long range profile quartz the 3850 km long deep seismic sounding profile quartz crosses six major geologic provinces in eurasia and is sourced by 3 nuclear and 48 chemical explosions we present the first interpretation of the entire data set using two dimensional 2 d ray tracing and inversion resolution analysis and 1 d amplitude modeling our interpretation shows a 42 km thick high velocity crust under the baltic shield a 29 km thick crust and high velocity upper mantle under the mezenskaya depression 52 km thick crust with high velocity lower crust and uppermost mantle under the urals and 40 km thick crust under the west siberian basin deepening to 45 km under the altay sayan fold belt high velocity 8 4 km s uppermost mantle is found under the mezenskaya depression and under the east flank of the urals one almost continuous upper mantle boundary occurs at 65 to 80 km depth and another with an approximately 40 km thick lvz occurs at 120 to 140 km depth the shallow upper mantle blocks and the two extensive interfaces indicate strong upper mantle heterogeneity resolution analysis based on direct multivariate model perturbations artificial neural network and principal component analysis indicate the depth uncertainty of the 410 km discontinuity within 6 km and also its trade off with dip and velocities above and below the discontinuity decreased near critical amplitudes of reflections from the 410 km and 660 km discontinuities indicate that these boundaries are most likely represented by gradient zones about 15 20 km thick lithosphere thins asthenospheric velocity decreases and the 410 km discontinuity dips to the se approaching the himalayan orogenic belt

on the negative phase shift of groundwater tides near shallow tidal rivers the gouderak anomaly abstract during a site investigation at gouderak the netherlands the observation was made that groundwater tides in several piezometers near the shallow tidal river hollandsche jsse were running ahead of the river tide by more than an hour although the current theory of groundwater flow does not account for this effect the phenomenon can be explained by means of well known elementary mechanisms the superposition principle is adopted to derive formulae for the phase shift and the attenuation in case of a single aquifer covered by an aquitard it is shown that for this simple system the maximum negative phase shift at the river bank amounts to 1 4 radians corresponding to 1 1 2 hour for the semidiurnal tidal component

a data driven approach for analyzing dynamics of tide aquifer interaction in coastal aquifer systems analysis of tidal effects on aquifer systems plays an important role in coastal aquifer management owing to various hydrological engineering and environmental problems in coastal areas using the real world data of unconfined and confined aquifers a data driven approach is presented in this study for the analysis of tide aquifer interaction in coastal aquifers six analytical tide aquifer interaction models were selected which take into account the effects of vertical beach sloping beach tidal loading aquifer leakage outlet capping and combined leakage and outlet capping on tide induced groundwater fluctuations the tide aquifer interaction datasets were obtained from the konan groundwater basin unconfined aquifer of japan and the dridrate groundwater basin confined aquifer of morocco the analysis of the results obtained by the sloping beach model revealed that for a given beach slope the amplitude of groundwater level increases with an increase in aquifer diffusivity and a decrease in aquifer thickness however no significant effect of beach slope was observed in this study at unconfined sites for all the datasets the influence of tidal loading was found to be considerably less for all the three confined sites further the analysis of the results of the leakage model indicated that with an increase in leakage into the aquifer the amplitude of groundwater level as well as the phase shift time lag decreases of all the confined and unconfined datasets only two confined sites were found to be affected by outlet capping overall it is concluded that the coastal beach bordering the konan basin is not significantly sloping the contribution of tidal loading to tide induced groundwater fluctuations in the dridrate aquifer is not appreciable and that the aquifer leakage and outlet capping do not exist at the unconfined sites under investigation

lithospheric boundaries and upper mantle heterogeneity beneath russian eurasia evidence from the dss profile quartz abstract a combined interpretation of seismic data from the 3850 km long russian seismic profile quartz using chemical and nuclear explosions reveals complex structure of the lithosphere related to the regional tectonics our analysis is focused on the structure of the uppermost mantle and based on 2d ray tracing and inversion of the data from all 51 shots along the profile on 2d attenuation measurements and on the results of an analysis of the long range pn phase three groups of reflectors within the lithosphere are associated with regional to global boundaries previously recognized in stable continental environments one almost continuous upper mantle boundary occurs at 65 to 80 km depth and another with an approximately 40 km thick low velocity zone lvz occurs at 120 140 km depth the shallow upper mantle blocks and the extensive interfaces indicate strong upper mantle heterogeneity imaged by this unique profile the thickness of the lithosphere varies from 220 km under the baltic shield to about 120 130 km under the tectonically active himalayan altay sayan fold belt within the lower part of the lithosphere a zone of lower velocity increased attenuation and varying thickness might be related to hydration and partial melting large structural differences related to tectonic ages and histories are characteristic for the entire lithosphere and extend 200 400 km into the asthenosphere analysis of quartz data gives confident indication of seismic heterogeneity from crustal to regional mantle scales indicating strong involvement of the mantle in tectonic processes

structure of the lithospheric mantle beneath the trans hudson orogen canada abstract refraction and wide angle reflection seismic data collected in northern saskatchewan and manitoba in 1993 by lithoprobe provide new glimpses of the deep structure of the lithospheric mantle beneath the trans hudson orogen velocity models obtained through ray tracing modelling techniques revealed the presence of complicated mantle structures down to a depth of 160 km beneath the orogen like the crust the lithospheric mantle appears to show a seismically transparent upper and a highly reflective lower part suggesting that the rheological environment responsible for development of reflections in the lithospheric mantle and of that in the crust are similar this appears to be consistent with the observation that the strong and brittle upper 30 km of the mantle contain remnants of former tectonic processes in a form of velocity anisotropy and the lower more ductile zone seems highly reflective and isotropic the suspected beginning of the lithosphere asthenosphere transition zone at a depth of 160 km imaged as gradual disappearance of mantle reflections coincides well with models established using other geophysical methods

tide induced groundwater level fluctuation in coastal aquifers bounded by l shaped coastlines 1 this paper presents an analytical solution to describe tidal groundwater level fluctuations in an aquifer bounded by two water land boundaries that form a right angle the aquifer configuration can represent the situation of a right angle corner in an island when the tidal boundaries are the same along both boundaries or the estuary situation if the amplitude damps with distance along one boundary river and the amplitude along the other boundary sea does not change spatially the two dimensional flow equation subject to periodic boundary conditions is changed into a time independent elliptic problem using complex transform the elliptic problem is then solved using the green s function method li et al 2000 obtained a nonperiodic solution to the same problem with an additional hypothetical initial condition their solution includes a time dependent integral the solution presented here is a significant improvement over theirs in the sense that the solution is periodic and computationally efficient since the integral involved is independent of time an approximate solution without integral is also derived an error analysis and a case study in hong kong demonstrate that the approximate solution is adequate for most field problems index terms 1829 hydrology groundwater hydrology 1832 hydrology groundwater transport 1899 hydrology general or miscellaneous 3384 meteorology and atmospheric dynamics waves and tides keywords periodic groundwater flow analytical solution coastal aquifer sea tide l shaped coastline

groundwater monitoring at a building site of the tidal flood protection system mose in the lagoon of venice italy to protect venice against tidal flooding the mose system experimental electro mechanic module has been under construction since 2003 this safeguarding system is composed of four batteries of mobile barriers at the lagoon s inlets lido malamocco chioggia which will be lifted before the occurrence of exceptional high tides 1 10 m above the mean sea level isolating the venetian lagoon from the sea the end of the construction work is foreseen by 2016 in this paper the results of the groundwater monitoring at the building site of punta sabbioni at the lido inlet are described a large dewatered basin tura formerly occupied by the sea and close to the shoreline was used for the precasting of the mobile barriers and the impact of groundwater control was therefore monitored in the phreatic and shallow confined aquifers although a slurry wall barrier was excavated to isolate the tura a drawdown cone in the confined aquifer was observed extending to 1 km from the construction site in contrast the phreatic aquifer was only influenced by tides rainfall and evapotranspiration and the slurry wall of the tura had a positive effect of decreasing the groundwater salinity by limiting the seawater intrusion as confirmed by the electrical conductivity profiles measured inside the piezometers the monitoring activity was successful in assessing the impacts of the construction work on the aquifer system and in distinguishing them from the effects of natural driving forces

tide induced groundwater fluctuation in a coastal leaky confined aquifer system extending under the sea this paper presents the analytical solution of groundwater response to tidal fluctuation in a coastal multilayer aquifer system consisting of a leaky confined aquifer a semipermeable layer and an unconfined aquifer the semipermeable layer or the roof of the leaky confined aquifer extends under the sea comparisons are made with solutions derived previously which considered only a single aquifer zero extension of the roof or infinite roof length and demonstrate that the previous solutions are special cases of the solution presented here a hypothetical example is used to discuss the impact of the dimensionless roof length dimensionless leakage and tidal efficiency on the groundwater level fluctuations in the inland part of the confined aquifer the fluctuation decreases significantly with the roof length when the roof length is small but is insensitive to the change of roof length when the roof length is greater than a threshold the impacts of leakage from the offshore and inland portions of the confining unit are different leakage from the offshore portion tends to increase the fluctuation of the groundwater level while leakage from the inland portion tends to decrease the fluctuation the fluctuation increases as the tidal efficiency increases this fact is significant only when the roof length is great and leakage is small

one dimensional airflow in unsaturated zone induced by periodic water table fluctuation the amplitude of p0 t increases with the frequency of the head fluctuation the upper layer s thickness and the unconfined aquifer s air filled porosity and decreases with the upper layer s permeability the phase shift of p0 t ranges from 0 to p 2 indicating a time advance particularly p0 t is approximately proportional to the temporal derivative of the head for sufficiently thin or permeable upper layer and to the head itself for sufficiently thick or less permeable one the fluctuation amplitude of the water table is always less than that of the head and can be only one tenth of the latter if the upper layer is sufficiently thick or less permeable which may slow significantly the landward attenuation speed of the tide induced head fluctuation in a coastal air confined aquifer the analytical solution was used to estimate the value range of the air permeability of the marine sand fill at a coastal reclamation area of hong kong

intraplate earthquakes and a seismically defined lateral transition in the upper mantle we show that the lateral transition in the upper mantle between the cratonic central eastern and the tectonically active western regions of north america is narrow and deep reaching by travel time analysis of early rise explosion seismic data a concentration of enigmatic intraplate earthquakes coincides with the transition differential potential energy from density changes across the transition may generate a high compressional stress level which locally exceeds the shear strength of the lithosphere the resultant deformation is ductile in most parts of the lithosphere but in the brittle upper crust it explains the enigmatic intraplate earthquakes around the lateral transition in the upper mantle

receiver function analysis of the crust and upper mantle in fennoscandia isostatic implications abstract the mountains across southern norway and other margins of the north atlantic ocean appear conspicuously high in the absence of recent convergent tectonics we investigate this phenomenon with receiver functions calculated for seismometers deployed across southern fennoscandia these are used to constrain the structure and seismic properties of the lithosphere and primarily to measure the thickness and infer the bulk composition of the crust such parameters are key to understanding crustal isostasy and assessing its role or lack thereof in supporting the observed elevations our study focuses on the southern scandes mountain range that has an average elevation 1 0 km above mean sea level the crust mantle boundary moho is ubiquitously imaged and we occasionally observe structures that may represent the base of the continental lithosphere or other thermal chemical or viscous boundaries in the upper mantle the moho resides at 25 30 km depth below mean sea level in southeastern coastal norway and parts of denmark 35 45 km across the southern scandes and 50 60 km near the norwegian swedish border that section of thickest crust coincides with much of the transscandinavian igneous belt and often exhibits a diffuse conversion at the moho which probably results from the presence of a high wave speed mafic lower crust across inner fennoscandia a zone of thinned crust

on the nature of mantle heterogeneities and discontinuities evidence from a very dense wide angle shot record abstract a seismic survey with a receiver spacing of 50 m provided one of the most densely sampled wide angle seismic reflection images of the lithosphere this unique data set recorded by an 18 km long spread reveals that at wide angles the shallow subcrustal mantle features high amplitude reflectivity which contrasts with a lack of reflectivity at latter travel times this change in the seismic signature is located at approximately 120 150 km depth which correlates with the depth estimates of the lithosphere asthenosphere boundary lab of previous dss studies this seismic signature can be simulated by two layer mantle model both layers with similar average velocities differ in their degree of heterogeneity the shallow heterogeneous layer and the deeper and more homogeneous one correlate with the lithosphere and the asthenosphere respectively studies involving surface outcrops of ultramafic massifs and mantle xenoliths infer that the upper mantle is a heterogeneous mixture of ultramafic rocks lherzolites harzburgites pyroxenites peridotites dunites and small amounts of eclogites laboratory measurements of physical properties of these mantle rocks indicate that compositional variations alone can account for the wide angle reflectivity a temperature increase would homogenize the mixture decreasing the seismic reflection properties due to melting processes it is proposed that this would take place below 120 150 km 1200 c the lab

implications of seismic scattering below the 8 discontinuity along pne profile kraton abstract strong scattered arrivals are observed in the 800 1400 km offset range of the four peaceful nuclear explosion pne seismic sections along the 3500 km long e w trending russian profile kraton they give evidence of an 85 km thick inhomogeneous scattering layer in the upper mantle which has a slightly reduced 1 average p wave velocity compared to the layers above and below the top of the anomalous zone is the 8 discontinuity at 100 km depth which is constrained by a clear travel time delay of up to 2 s consistently observed at 900 1000 km 8 offset in the four pne seismic sections we model the inhomogeneous zone below the 8 discontinuity by random velocity fluctuations the full waveform seismic response of a suite of stochastic velocity models is calculated using a two dimensional finite difference scheme the calculated seismic sections resemble the pne data for models where the random fluctuations have a horizontal correlation length of 5 10 km a vertical correlation length not greater than 5 km and a standard deviation of about 2 of the average background velocity fluctuations with significantly larger correlation lengths give rise to coherent scattered arrivals and considerably shorter correlation lengths lead to significantly weaker scattering none of which resemble the observed data the preferred seismic velocity model is in agreement with an upper mantle model in which the low velocity zone below the 8 discontinuity may contain small amounts of partially molten material alternatively the combined effects of rheological weakening and small scale anisotropy may also account for the low velocity scattering layer

upper mantle structure of the baltic shield below the swedish national seismological network snsn resolved by teleseismic tomography summary upper mantle structure under the baltic shield is studied using non linear high resolution teleseismic p phase tomography observed relative arrival time residuals from 52 teleseismic earthquakes recorded by the swedish national seismological network snsn are inverted to delineate the structure of the upper mantle the network consists of 47 currently working three component broad band stations located in an area about 450 km wide and 1450 km long in order to reduce complications due to possible significant three dimensionality of earth structure events chosen for this study lay close to in line with the long axis of the array 30 results indicate p wave velocity perturbations of 3 per cent down to at least 470 km below the network the size of the array allows inversion for structures even at greater depths and lateral variations of velocity at depths of up to 680 km appear to be resolved below the central part of the array 60 64 n where ray coverage is best the data reveals a large region of relatively low velocity at depths of over about 300 km at depths less than about 250 300 km the models include a number of features including an apparent slab like structure dipping gently towards the north

deformation exhumation and topography of experimental doubly vergent orogenic wedges subjected to asymmetric erosion we explore the effect of asymmetric erosion and dip angle of the indenter on the internal kinematics deformation and exhumation of an experimental doubly vergent orogenic wedge during transient and steady state flux conditions we calculate displacement fields and derive strain and exhumation for several erosion and non erosion cases using particle image velocimetry piv analysis we apply calculated displacement fields to a simple heat equation to explore virtual evolution of thermal structure erosion exerts a primary control in the internal kinematics of the experimental wedge in non erosion cases early formed fore shears rotate toward the indenter such that the shear bands become steeper this effect is more pronounced in prowedge erosion cases where shear bands become very steep and even overturned conversely retrowedge erosion results in back rotation of early formed fore shears and the shear bands evolved to gently dipping structures wedge erosion in combination with the condition of flux and topographic steady state increases density of fore shears and controls size width and topographic divide migration steeply dipping indenters produce overall gentle particle trajectories and gently dipping indenters favor steep trajectories particle velocity with respect to isotherms increases where erosion is concentrated and near active fore shears