wave attenuation over coastal salt marshes under storm surge conditions salt marshes protect coastlines against waves wave flume experiments show that marsh vegetation causes substantial wave dissipation and prevents erosion of the underlying surface even during extreme storm surge conditions

revisiting the nd 142 deficits in the 1 48 ga khariar alkaline rocks india the 146sm 142nd system plays a central role in tracing the silicate differentiation of the earth prior to 4 1 ga after this time given its initial abundance the 146sm can be considered to be extinct upadhyay et al 2009 reported unexpected negative 142nd anomalies in 1 48 ga rocks of the khariar nepheline syenite complex india and inferred that an early enriched low sm nd reservoir must have contributed to the mantle source rocks of the khariar complex as 146sm had been effectively extinct for about 2 6 billion years before the crystallisation of the khariar samples this nd signature should have remained isolated from the convective mantle for at least that long it was thus suggested that the source rock of khariar samples had been sequestered in the lithospheric root of the indian craton using a different chemical separation method and a different thermal ionization mass spectrometry tims analysis protocol the present study attempted to replicate these negative 142nd anomalies but none were found to determine which data set is correct we investigated three possible sources of bias between them imperfect cancellation of faraday collector efficiencies during multidynamic tims analysis rapid sample fractionation between the sequential measurement of 146nd 144nd and 142nd 144nd and non exponential law behaviour resulting from so called domain mixing incomplete cancellation of collector efficiencies was found unlikely to cause resolvable biases at the estimated level of variation among collector efficiencies even in the case of highly variable efficiency and resolvable biases there is no reason to suspect that they would reproducibly affect only four rocks out of 10 analysed by upadhyay et al 2009 although domain mixing may explain apparent reverse fractionation trends observed in some tims analyses it cannot be the cause of the apparent negative anomalies in the study of upadhyay et al 2009 it was determined that rapid mass fractionation during the course of a multidynamic tims analysis can bias all measured nd ratios after applying an approximate correction for this effect only one rock from upadhyay et al 2009 retained an apparent negative 142nd anomaly this in conjunction with our new anomaly free data set measured at fractionation rates too low to cause bias leads to the conclusion that the anomalies reported by upadhyay et al 2009 are a subtle and reproducible analytical artefact the absence of negative 142nd anomalies in these rocks relaxes the need for a mechanism other than crust formation that can isolate a nd reservoir from the convective mantle for billions of years

seismic velocity and attenuation structures of the queen charlotte basin from full waveform tomography of seismic reflection data abstractwe applied viscoacoustic waveform tomography to four seismic reflection lines from the central and northern part of the queen charlotte sedimentary basin and using frequencies of 7 12 hz we estimated the compressional velocity and attenuation above a depth of approximately 1 2 km we refined our previously published inversion strategy by alternating between phase only and amplitude plus phase velocity inversion for the first two pairs of frequencies used and added a second step in which we inverted for attenuation from the lowest frequency using the final recovered velocity model and an initial homogeneous qp model our recovered velocity and attenuation models demonstrated an overall good correlation with the available sonic and gamma ray logs modeled seismic data matches the field data well and 1d velocity and attenuation profiles extracted at line intersections show a good correlation thus demonstrating the robust nature of the results recovered velocities aid in interpreting shallow str

experimental study on vegetation flexibility as control parameter for wave damping and velocity structure abstract vegetation can contribute to coastal defence by damping incoming waves however prior studies have shown that attenuation varies greatly among plant species plant flexibility is a mechanical property that is commonly omitted but varies considerably between shrubs and grasses on salt marshes therefore we present an experimental study in a laboratory wave flume with artificial vegetation that differs in flexibility only we measured wave attenuation and water particle velocities around rigid and flexible salt marsh vegetation waves were measured using a series of gauges and particle image velocimetry piv was used to measure spatio temporal variations of water particle velocities in the x z plane around the vegetation our results show that flexible vegetation attenuates waves up to 70 less than rigid vegetation due to swaying of flexible plants furthermore we find that rigid vegetation modifies the velocity structure whereas flexible vegetation does not specifically a mean current in the direction of wave propagation develops around the canopy and the horizontal particle velocities are amplified directly above the canopy these results indicate that plant flexibility is a key parameter in the wave vegetation interaction that controls wave damping and velocity structure

geometrical and mechanical properties of four species of northern european brown macroalgae abstract aquatic vegetation interacts with the flow by posing an obstruction and in return experiences drag and is reconfigured by acting forces it is suggested that plant buoyancy and stiffness affect these bio physical interactions and hence should be considered when including vegetation in physical and numerical hydrodynamic models however data on these parameters is either lacking for many species or existing information is insufficient to model flexible aquatic vegetation correctly previous studies have focused on plant stems but did not take plant foliage into account the present study extends the existing knowledge base by providing data for four northern european brown macroalgae and also provides a comparison between the mechanical properties of stem and blade tissue for these species specimens of alaria esculenta laminaria digitata fucus serratus and fucus vesiculosus were collected from a small tidal inlet in norway other than f serratus the macroalgae were positively buoyant and all stems showed bending moduli in agreement with previous studies with respect to their order of magnitude only l digitata exhibited a significant difference between bending moduli for stems and blades and also between the tip and the base of the blades however there were differences in flexural rigidities product of bending modulus and second moment of cross sectional area of both stems and blades and the tip and the base of blades of all but f serratus this highlights the important influence of cross sectional area and cross sectional shape on stiffness

crustal seismic imaging from multifold ocean bottom seismometer data by frequency domain full waveform tomography application to the eastern nankai trough 1 in offshore surveys the deep crust is generally investigated by traveltime tomography applied to sparse ocean bottom seismometer data the inferred velocity models are of limited resolution precluding a quantitative analysis of deep tectonic discontinuities if dense arrays of ocean bottom seismometers can be deployed the resulting data sets become amenable to full waveform processing which should lead to a significant improvement in the resolution of structures such acquisition and processing were achieved on the eastern nankai subduction zone full waveform inversion is entirely implemented in the frequency domain enabling efficient finite difference wave modeling and allowing to limit the inversion to a few discrete frequencies of increasing value such a hierarchical procedure defines a multiresolution approach to seismic imaging the data set was recorded by 93 instruments deployed along a 105 km long profile thirteen frequencies ranging from 3 to 15 hz were inverted sequentially wavelengths imaged by the full waveform inversion typically range between 0 5 and 8 km full waveform tomography reveals an intense compression in the upper prism and underlying backstop as evidenced by several thrusts the frontal ones still active corresponding to negative velocity anomalies the subducting paleo zenisu ridge is also reconstructed above which stands the decollement velocities in the upper mantle beneath the ridge are rather low 7 5 km s 1 suggesting partially serpentinized mantle beneath the ridge this paper demonstrates the feasibility of full waveform tomography based on dense ocean bottom seismometer data sets and its ability to quantitatively image the entire crust with a significantly improved resolution compared to what is usually achieved through traveltime tomography

wave dissipation by flexible vegetation 1 dissipation of waves propagating through natural salt marsh vegetation was about half the dissipation expected for rigid vegetation this low dissipation was predicted by a theoretical model that accounts for bending of vegetation motions a transect of 3 pulse coherent acoustic doppler profilers recorded water velocity and pressure at 8 hz within the dense 650 stems m2 canopy of semi flexible single stem vegetation schoenoplectus americanus most wave energy 56 81 was dissipated within 19 m of the marsh edge two dissipation models the first assuming rigid vegetation and the second simulating wave forced vegetation motion using the theory for bending of linearly elastic beams were tested after choosing optimal drag coefficients both models yielded a good fit to the observed dissipation skill score 0 96 0 99 however fitted drag coefficients for the rigid model 0 58 0 78 were below the range 0 98 2 2 expected for the observed reynolds numbers 13 450 and canopy densities accounting for interactions between stem wakes whereas drag coefficients for the flexible model 0 97 1 6 were nearer the expected range indicating that prediction of wave dissipation was improved by simulating vegetation motion

high resolution seismic attenuation imaging from wide aperture onshore data by visco acoustic frequency domain full waveform inversion summary here we assess the potential of the visco acoustic frequency domain full waveform inversion fwi to reconstruct p wave velocity vp and p wave attenuation factor q from surface onshore seismic data first we perform a sensitivity analysis of the fwi based upon a grid search analysis of the misfit function and several synthetic fwi examples using velocity and q models of increasing complexity subsequently we applied both the acoustic and viscoacousticfwitorealsurfacewide apertureonshoreseismicdatafromthepolishbasin wherea strongattenuationoftheseismicdataisobserved thesensitivityanalysisofthevisco acoustic fwi suggests that the fwi can jointly reconstruct the velocity and the attenuation factor if the signatureoftheattenuationissufficientlystronginthedata asyntheticexamplecorresponding to a homogeneous background model with an inclusion shows a reliable reconstruction of vp and q in the inclusion when q is as small as 90 and 50 in the background model and in the inclusion respectively a first application of acoustic fwi to real data shows that a heuristic normalization of the data with offset allows us to compensate for the effect of the attenuation in the data and reconstruct a reliable velocity model alternatively we show that visco acoustic fwi allows us to reconstruct jointly both a reliable velocity model and a q model from the true amplitude data we propose a pragmatical approach based upon seismic modelling and source wavelet estimation to infer the best starting homogeneous q model for visco acoustic fwi we find the source wavelet estimation quite sensitive to the quality of the velocity and attenuation models used for the estimation for example source to source wavelets are significantly more consistent when computed in the final fwi model than in the initial one a good kinematic and amplitude match between the early arriving phases of the real and time domain synthetic seismograms computed in the final fwi model provides an additional evidence of the reliability of the final fwi model we find the recovered velocity and attenuation models consistent with the expected lithology and stratigraphy in the study area we link high attenuation zones with the increased clay content and the presence of the mineralized fluids

large scale 3 d experiments of wave and current interaction with real vegetation part 2 experimental analysis abstract this paper assesses the influence of different flow and vegetation parameters on the wave attenuation provided by two contrasting salt marsh species puccinellia maritima and spartina anglica different water depths and wave parameters height and period are considered for both regular and irregular waves with and without an underlying uniform current coming from different directions the study of the submergence ratio h h v influence shows that wave damping coefficient rapidly decreases as the plant submergence ratio increases the high nonlinearities found in the wave current interaction lead to different wave damping patterns in comparison to wave only conditions a smaller wave damping is found for waves and current acting in the same direction and an increase in the wave damping rate is obtained for waves and current flowing in the opposite direction these wave and current tests allow for the studying of the energy dissipation produced by the vegetation increasing our knowledge about flow and plant interaction in estuarine conditions the biomechanical properties of the two real salt marshes used in the experiments are also evaluated and related to wave damping revealing a higher attenuation for stiffer vegetation both the vegetation density and the biomass strongly influence wave damping higher density and biomass values lead to higher attenuation rates for both species

flow structure in canopy models dominated by progressive waves summary laboratory experiments were carried out to study the flow structure both inside and above different canopy models which were dominated by progressive waves a set of experimental conditions were considered in a laboratory flume three vegetation models submerged rigid submerged flexible and emergent rigid three plant densities 128 640 and 1280 stems m 2 and three wave frequencies f 0 8 1 and 1 4 hz the progressive waves followed the second order stokes theory in the intermediate depth range the observations revealed that submerged and emergent rigid vegetation models modified the wave induced velocities i e both mean current and wave velocity the submerged rigid vegetation model for plant densities higher than 640 plants m 2 and wave frequency higher than 1 hz acted akin to a false floor confining the mean current to above the plant bed a penetration depth around 2 cm below the top of submerged rigid vegetation was found for the other runs the vertical profile of mean current did not present changes with respect to runs without plants the emergent rigid vegetation model reversed the direction of the induced mean current with the highest velocity corresponding to the highest plant density in contrast the submerged flexible vegetation model had a weak effect on the mean current with the vertical velocity profile similar to that found in experiments without vegetation the wave velocities inside the vegetation for the densest submerged rigid vegetation were found to be reduced by 20 when compared to the wave velocities without vegetation while in emergent rigid vegetation this reduction was of 45

plant stiffness and biomass as drivers for drag forces under extreme wave loading a flume study on mimics abstract moving water exerts drag forces on vegetation the susceptibility of vegetation to bending and breakage determines its flow resistance and chances of survival under hydrodynamic loading to evaluate the role of individual vegetation parameters in this water vegetation interaction we conducted drag force measurements under a wide range of wave loadings in a large wave flume artificial vegetation elements were used to manipulate stiffness frontal area in still water and material volume as a proxy for biomass the aim was to compare i identical volume but different still frontal area ii identical stiffness but different still frontal area and iii identical still frontal area but different volume comparison of mimic arrangements showed that stiffness and the dynamic frontal area i e frontal area resulting from bending which depends on stiffness and hydrodynamic forcing determine drag forces only at low orbital flow velocities did the still frontal area dominate the force velocity relationship and it is hypothesised that no mimic bending took place under these conditions mimic arrangements with identical stiffness but different overall material volume and still frontal area showed that forces do not increase linearly with increasing material volume and it is proposed that short distances between mimics cause their interaction and result in additional drag forces a model based on effective leaf length and characteristic plant width developed for unidirectional flow performed well for the force time series under both regular and irregular waves however its uncertainty increased with increasing interaction of neighbouring mimics

imaging high resolution seismic velocity from walkaway vertical seismic profile data in a carbonate reservoir using acoustic waveform tomography abstracthigh resolution seismic velocity was obtained using acoustic full waveform tomography of walkaway vertical seismic profile vsp data from an oil field dominated by carbonate rocks offshore abu dhabi in the united arab emirates the data were collected in a deviated borehole with receivers located from 521 to 2742 m depth the inversion was performed in the frequency domain the success of the inversion was determined by three important factors the starting model the preconditioning of the input data and the inversion strategy which included an appropriate selection of a damping term in the laplace fourier transformation the inversion was performed between the frequencies of 4 and 50 hz and a logarithmic data residual was used the extracted 1d velocity profiles from the final high resolution velocity model correlate well with the sonic log and estimated vertical incidence vsp velocities the predicted data obtained by the final velocity model indicate a generally good fit with the field

three dimensional seismic refraction tomography a comparison of two methods applied to data from the faeroe basin this paper presents a comparison of two tomographic methods for determining three dimensional 3 d velocity structure from first arrival travel time data the first method is backprojection in which travel time residuals are distributed along their ray paths independently of all other rays the second method is regularized inversion in which a combination of data misfit and model roughness is minimized to provide the smoothest model appropriate for the data errors both methods are nonlinear in that a starting model is required and new ray paths are calculated at each iteration travel times are calculated using an efficient implementation of an existing method for solving the eikonal equation by finite differencing both inverse methods are applied to 3 d ocean bottom seismometer obs data collected in 1993 over the faeroe basin consisting of 53 479 travel times recorded at 29 obss this is one of the most densely spaced large scale 3 d seismic refraction experiments to date different starting models and values for the free parameters of each tomographic method are tested a new form of backprojection that converges more rapidly than similar methods compares favorably with regularized inversion but the latter method provides a simpler model for little additional computational expense when applied to the faeroe basin data bounds on two model features are assessed using regularized inversion with combined smoothness and flatness constraints an inversion of synthetic data corresponding to 100 data recovery from the real experiment shows a marked improvement in lateral resolution at deeper depths and demonstrates the potential of currently feasible 3 d refraction experiments to provide well resolved long wavelength velocity models the similarity of the final models derived from the two tomographic methods suggests that the results from the new form of backprojection can be relied on when limited computational resources rule out regularized inversion

building starting models for full waveform inversion from wide aperture data by stereotomography building an accurate initial velocity model for full waveform inversion fwi is a key issue to guarantee convergence of full waveform inversion towards the global minimum of a misfit function in this study we assess joint refraction and reflection stereotomography as a tool to build a reliable starting model for frequency domain full waveform inversion from long offset i e wide aperture data stereotomography is a slope tomographic method that is based on the inversion of traveltimes and slopes of locally coherent events in a data cube one advantage of stereotomography compare to conventional traveltime reflection tomography is the semi automatic picking procedure of locally coherent events which is easier than the picking of continuous events and can lead to a higher density of picks while conventional applications of stereotomography only consider short offset reflected waves we assess the benefits provided by the joint inversion of reflected and refracted arrivals introduction of the refracted waves allows the construction of a starting model that kinematically fits the first arrivals a necessary requirement for full waveform inversion in a similar way to frequency domain full waveform inversion we design a multiscale approach of stereotomography which proceeds hierarchically from the wide aperture to the short aperture components of the data to reduce the non linearity of the stereotomographic inversion of long offset data this workflow which combines stereotomography and full waveform inversion is applied to synthetic and real data case studies for the valhall oil field target the synthetic results show that the joint refraction and reflection stereotomography for a 24 km maximum offset data set provides a more reliable initial model for full waveform inversion than reflection stereotomography performed for a 4 km maximum offset data set in particular in low velocity gas layers and in the deep part of a structure below a reservoir application of joint stereotomography full waveform inversion and reverse time migration to real data reveals that the fwi models and the reverse time migration images computed from the stereotomography model shares several features with fwi velocity models and migrated images computed from an anisotropic reflection traveltime tomography model although stereotomography was performed in the isotropic approximation implementation of anisotropy in joint refraction and reflection stereotomography of long offset data is a key issue to further improve the accuracy of the method

wave attenuation by flexible idealized salt marsh vegetation abstract wave attenuation by vegetation is a highly dynamic process and its quantification is important for understanding shore protection potential and modeling coastal hydrodynamics data documenting the interactions of spartina alterniflora represented by polyolefin tubing and single and double peaked irregular waves were collected in a large scale laboratory flume the laboratory provided a controlled environment to evaluate wave attenuation including the parameters of stem density submergence wave height and peak period wave attenuation appeared to be most dependent on stem density and the ratio of stem length to water depth wave attention increased slightly with wave height while no clear trend with respect to wave period was seen treating double peaked spectra as superimposed wave systems revealed a preferential dissipation of the higher frequency wave system relative to the lower frequency wave system under emergent conditions wave energy loss occurred at all frequencies of both spectral types with dissipation increasing with frequency above the spectral peak parameterizing the spectral equilibrium range as a function of frequency showed a steepening of the spectral tail compared to the 4 power law under emergent conditions an empirical relationship defining the bulk drag coefficient for s alterniflora as a function of the stem reynolds number is found to serve as a first estimate for engineering applications

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

misfit functionals in laplace fourier domain waveform inversion with application to wide angle ocean bottom seismograph data in seismic waveform inversion non linearity and non uniqueness require appropriate strategies we formulate four types of l2 normed misfit functionals for laplace fourier domain waveform inversion i subtraction of complex valued observed data from complex valued predicted data the conventional phase amplitude residual ii a conventional phase only residual in which amplitude variations are normalized iii a logarithmic phase amplitude residual and finally iv a logarithmic phase only residual in which the only imaginary part of the logarithmic residual is used we evaluate these misfit functionals by using a wide angle field ocean bottom seismograph obs data set with a maximum offset of 55 km the conventional phase amplitude approach is restricted in illumination and delineates only shallow velocity structures in contrast the other three misfit functionals retrieve detailed velocity structures with clear lithological boundaries down to the deeper part of the model we also test the performance of additional phase amplitude inversions starting from the logarithmic phase only inversion result the resulting velocity updates are prominent only in the high wavenumber components sharpening the lithological boundaries we argue that the discrepancies in the behaviours of the misfit functionals are primarily caused by the sensitivities of the model gradient to strong amplitude variations in the data as the observed data amplitudes are dominated by the near offset traces the conventional phase amplitude inversion primarily updates the shallow structures as a result in contrast the other three misfit functionals eliminate the strong dependence on amplitude variation naturally and enhance the depth of illumination we further suggest that the phase only inversions are sufficient to obtain robust and reliable velocity structures and the amplitude information is of secondary importance in constraining subsurface velocity models

nature based flood protection the efficiency of vegetated foreshores for reducing wave loads on coastal dikes this paper analyses the effect of vegetation on wave damping under severe storm conditions based on a combination of field measurements and numerical modelling the field measurements of wave attenuation by vegetation were performed on two salt marshes with two representative but contrasting coastal wetland vegetation types cordgrass spartina anglica and grassweed scirpus maritimus the former is found in salty environments whereas the latter is found in brackish environments the measurements have added to the range with the highest water depths and wave heights presented in the literature so far a numerical wave model swan has been calibrated and validated using the new field data it appeared that the model was well capable of reproducing the observed decay in wave height over the salt marsh the model has been applied to compute the reduction of the incident wave height on a dike for various realistic foreshore configurations and hydraulic loading conditions additionally the efficiency of vegetated foreshores in reducing wave loads on the dike has been investigated where wave loads were quantified using a computed wave run up height and wave overtopping discharge the outcomes show that vegetated foreshores reduce wave loads on coastal dikes significantly also for the large inundation depths that occur during storms and with the vegetation being in winter state the effect of the foreshore on the wave loads varies with wave height to water depth ratio on the foreshore the presence of vegetation on the foreshore extends the range of water depths for which a foreshore can be applied for effective reduction of wave loads and prevents intense wave breaking on the foreshore to occur this research demonstrates that vegetated foreshores can be considered as a promising supplement to conventional engineering methods for dike reinforcement

hydrodynamics induced by wind waves in a vegetation field the wave induced kinematics and dynamics of a submerged or emerged vegetation field is analyzed using potential flow and an eigenfunction expansion the problem is solved considering regular as well as irregular incident waves the model takes into account the vegetation motion and solves for the complete wave system on the vegetation field and in its vicinity the model is validated against experimental laboratory data obtained by other authors showing a much better agreement than previous theoretical models in this paper the model is used to evaluate wave height evolution damping vegetation and fluid motion and forces and moments on the vegetation furthermore the inclusion of irregular waves provides force and moment distributions on the vegetation field depending on the wave climate statistics

applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early arrival windows a recently developed time domain multiscale waveform tomography mwt method is applied to synthetic and field marine data although the mwt method was already applied to synthetic data the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging this hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2d seg eage salt model in the application of mwt to the field data the inversion process is carried out using a multiscale method with a dynamic early arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects with the modified mwt method reasonably accurate results as verified by comparison of migration images and common image gathers were obtained the hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation however we believe it is applicable to field data applications