high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

information content of slug tests for estimating hydraulic properties in realistic high conductivity aquifer scenarios summary a recently developed unified model for partially penetrating slug tests in unconfined aquifers malama et al in press provides a semi analytical solution for aquifer response at the wellbore in the presence of inertial effects and wellbore skin and is able to model the full range of responses from overdamped monotonic to underdamped oscillatory while the model provides a unifying framework for realistically analyzing slug tests in aquifers with the ultimate goal of determining aquifer properties such as hydraulic conductivity k and specific storage s s it is currently unclear whether parameters of this model can be well identified without significant prior information and thus what degree of information content can be expected from such slug tests in this paper we examine the information content of slug tests in realistic field scenarios with respect to estimating aquifer properties through analysis of both numerical experiments and field datasets first through numerical experiments using markov chain monte carlo methods for gauging parameter uncertainty and identifiability we find that 1 as noted by previous researchers estimation of aquifer storage parameters using slug test data is highly unreliable and subject to significant uncertainty 2 joint estimation of aquifer and skin parameters contributes to significant uncertainty in both unless prior knowledge is available and 3 similarly without prior information joint estimation of both aquifer radial and vertical conductivity may be unreliable these results have significant implications for the types of information that must be collected prior to slug test analysis in order to obtain reliable aquifer parameter estimates for example plausible estimates of aquifer anisotropy ratios and bounds on wellbore skin k should be obtained if possible a priori secondly through analysis of field data consisting of over 2500 records from partially penetrating slug tests in a heterogeneous highly conductive aquifer we present some general findings that have applicability to slug testing in particular we find that aquifer hydraulic conductivity estimates obtained from larger slug heights tend to be lower on average presumably due to non linear wellbore losses and tend to be less variable presumably due to averaging over larger support volumes supporting the notion that using the smallest slug heights possible to produce measurable water level changes is an important strategy when mapping aquifer heterogeneity finally we present results specific to characterization of the aquifer at the boise hydrogeophysical research site specifically we note that 1 k estimates obtained using a range of different slug heights give similar results generally within 20 2 correlations between estimated k profiles with depth at closely spaced wells suggest that k values obtained from slug tests are representative of actual aquifer heterogeneity and not overly affected by near well media disturbance i e skin 3 geostatistical analysis of k values obtained indicates reasonable correlation lengths for sediments of this type and 4 overall k values obtained do not appear to correlate well with porosity data from previous studies

application of vertical radar profiling technique to sendai castle the vertical radar profiling vrp technique is able to explore much deeper than conventional surface ground penetrating radar gpr because it uses boreholes it has been successfully applied at the sendai castle site in japan to investigate the extent of an old stone wall and strata buried by a more recent stone wall the transmitter of a polarimetric radar system was moved within a borehole and the receiver was fixed on the ground surface several meters away from the borehole head cross and copolarization data were measured at a receiver position with a different orientation to the receiver ten data sets were acquired by placing the receiver in five directions the depolarization is strong indicating the subsurface contains a great amount of gravel to get clear and intuitive images of the subsurface we applied data processing techniques including the separation of direct and reflected waves of raw vrp data using f k filtering approach and kirchhoff migration of separated reflected waves by com

field measurements of duration limited growth of wind generated ocean surface waves at young stage of development abstract the issue of duration limited growth of wind generated waves is of importance to wave studies most analytical solutions for wind waves are given in time rather than fetch domain numerical modeling of wave development is also often conducted in temporal evolution mode experimental data of duration limited growth however are rare and do not cover a wide range of the wave development stage as a result theorists and modelers have to rely on fetch limited evolution data converting them into duration limited conditions on the basis of some assumptions during one of the field experiments of wind wave measurements a dataset was obtained that is almost ideal for duration limited wave growth analysis the dataset extends the range of coverage in dimensionless time of the existing database by about one order of magnitude the results of analysis provide strong support for the relation of space time conversion for rendering the fetch limited growth functions to duration limited growth functions qu

growth of surface wind waves in water of finite depth a theoretical approach in order to study the growth of wind waves in finite depth we extend miles theory to the finite depth domain a depth dependent wave growth rate is derived from the dispersion relation of the wind water interface a suitable dimensionless finite depth wave age parameter allows us to plot a family of wave growth curves each family member characterized by the water depth two major results are that for small wave age the wave growth rates are comparable to those of deep water and for large wave age a finite depth wave age limited growth is reached with wave growth rates going to zero the corresponding limiting wave length and limiting phase speed are explicitely calculated in the shallow and in the deep water cases a qualitative agreement with well known empirical results is established and shows the robust consistency of the linear theoretical approach

gnss r nonlocal sea state dependencies model and empirical verification global navigation satellite system reflectometry gnss r is an active bistatic remote sensing technique operating at l band frequencies gnss r signals scattered from a rough ocean surface are known to interact with longer surface waves than traditional scatterometery and altimetry signals a revised forward model for gnss r measurements is presented which assumes an ocean surface wave spectrum that is forced by other sources than just the local near surface winds the model is motivated by recent spaceborne gnss r observations that indicate a strong scattering dependence on significant wave height even after controlling for local wind speed this behavior is not well represented by the most commonly used gnss r scattering model which features a one to one relationship between wind speed and the mean square slope of the ocean surface the revised forward model incorporates a third generation wave model that is skillful at representing long waves an anchored spectral tail model and a gnss r electromagnetic scattering model in comparisons with the spaceborne measurements the new model is much better able to reproduce the empirical behavior

evolution of ocean slicks under a rising wind 1 airborne synthetic aperture radar and high resolution infrared imagery are used to examine the evolution of natural ocean slicks during a period of freshening wind initially the slicks are of the order of 50 m in width and have radar and thermal contrasts of the order of 10 db and several 0 1 c while there can be over time a transient reorganization of surface film material by internal waves the slicks are observed to disperse and are no longer detectible after 5 h the dispersion occurs through the action of langmuir circulation which results in along wind streaks or windrows as well as other effects prominent streaks occur preferentially along a slick s upwind side the downwind side resembling more of a leading edge at least early on over time the leading edge develops a corrugated shape and gaps begin to develop within the slicks the formation of gaps is compared with a conceptual model by dysthe 2006 for the tearing of a surface film in the region of positive surface straining eventually the slicks break into elongated patches that co exist with windrows which is consistent with the effects of advective dispersion

traveltime inversion of offset vertical seismic profiles a feasibility study traveltimes from an offset vertical seismic profile vsp are used to estimate subsurface two dimensional dip by applying an iterative least squares inverse method tests on synthetic data show that inversion techniques are capable of estimating dips in the vicinity of a wellbore by using the traveltimes of the direct arrivals and the primary reflections the inversion method involves a layer stripping approach in which the dips of the shallow layers are estimated before proceeding to estimate deeper dips examples demonstrate that the primary reflections become essential whenever the ratio of source offset to layer depth becomes small traveltime inversion also requires careful estimation of layer velocities and proper statics corrections aside from these difficulties and the ubiquitous nonuniqueness problem the vsp traveltime inversion was able to produce a valid earth model for tests on a real data case modified journal abstract

azimuthal and radial variation of wind generated surface waves inside tropical cyclones abstractfor wind generated waves the wind wave triplets reference wind speed significant wave height and spectral peak wave period are intimately connected through the fetch or duration limited wave growth functions the full set of the triplets can be obtained knowing only one of the three together with the input of fetch duration information using the pair of fetch limited duration limited wave growth functions the air sea energy and momentum exchanges are functions of the wind wave triplets and they can be quantified with the wind wave growth functions previous studies have shown that the wave development inside hurricanes follows essentially the same growth functions established for steady wind forcing conditions this paper presents the analysis of wind wave triplets collected inside hurricane bonnie 1998 at category 2 stage along 10 transects radiating from the hurricane center a fetch model is formulated for any location inside the hurricane applying the fetch model to the 2d hurric

spectral evolution of nearshore wave energy during a sea breeze cycle abstractfrom in situ measurements taken over several sea breeze cycles off a beach in southwest sw australia the evolution of the one dimensional spectrum of wave energy is observed to have a distinctive spectral shape during the land breeze phase of the cycle lower rates of dissipation of wave energy are seen at high frequencies compared to midrange frequencies above the remnant wind sea peak a simulation of waves was performed using the simulating waves nearshore swan model and produced the same spectral evolution by generating longshore modes as seen in the observations the performance of whitecapping schemes available in swan was assessed and the alves banner scheme was found to best simulate the observed growth and decay of the wave spectra during the onshore phase of the sea breeze cycle local wave growth is duration limited and during the offshore land breeze phase wave growth is fetch limited from an examination of the modeled two dimensional spectra it is found that quadruplet in

a comparison of regional phases from underground nuclear explosions at east kazakh and nevada test sites abstract analysis of regional data from east kazakh ussr and nevada test site nts underground nuclear explosions suggests possible mechanisms for the generation of both low and high frequency lg spectral characteristics of pn and lg phases from 25 soviet nuclear shots recorded at the chinese digital seismic network cdsn station wmq are analyzed for their dependence on parameters such as m b generally related to shot depth and spatial location shagan versus degelen test sites the observed results are compared with those from the nevada test site nts where the near source conditions are better known the average amplitude ratio pn lg is found to be stable with m b but to vary strongly with frequency for both shagan and yucca flat explosions of similar yield the reduction in amplitude over the frequency range of about 1 to 5 hz is considerably larger for lg than for pn the low frequency lg appears to be generated by the scattering of explosion generated rg into s especially for the shagan river explosions for which good agreement between observation and theory is observed this mechanism also provides a possible explanation for the stability of lg as an estimator of explosive yields because the scattering should be expected to occur over a large region of the shallow crust another important result supported by theory is that the higher frequency lg is strongly dependent on the source medium velocity at higher frequencies 3 to 7 hz the amplitude ratios pn lg for explosions from shagan degelen pahute mesa and yucca flat test sites show significant differences that appear related to differences in their source medium velocities the observed large differences in the relative spectral content of pn and lg from east kazakh and nts explosions are mainly due to the vast differences in the crustal structure of the two test sites

observations of typhoon waves in a reef lagoon of the south china sea abstractbased on wave measurements lasting three and a half years typhoon wave characteristics in a lagoon of the south china sea are discussed in this paper according to the upper boundaries of

a ten year data set for fetch and depth limited wave growth abstract this paper presents the key results from a ten year data set for lake ijssel and lake sloten in the netherlands containing information on wind storm surges and waves supplemented with swan 40 51 wave model results the wind speeds u 10 effective fetches x and water depths d for the data set ranged from 0 24 m s 1 0 8 25 km and 1 2 6 m respectively for locations with non sloping bottoms the range in non dimensional fetch x g x u 10 2 was about 25 80 000 while the range in dimensionless depth d g d u 10 2 was about 0 03 1 7 land water wind speed differences were much smaller than the roughness differences would suggest part of this seems due to thermal stability effects which even play a role during near gale force winds for storm surges a spectral response analysis showed that lake ijssel has several resonant peaks at time scales of order 1 h as for the waves wave steepnesses and dimensionless wave heights h g h m0 u 10 2 agreed reasonably well with parametric growth curves although there is no single curve to which the present data fit best for all cases for strongly depth limited waves the extreme values of d 0 03 and h m0 d 0 44 at the 1 7 m deep lake sloten were very close to the extremes found in lake george australia for the 5 m deep lake ijssel values of h m0 d were higher than the depth limited asymptotes of parametric wave growth curves the wave model test cases of this study demonstrated that swan underestimates h m0 for depth limited waves and that spectral details enhanced peak secondary humps were not well reproduced from h m0 d 0 2 0 3 on swan also underestimated the quick wave response within 0 3 1 h to sudden wind increases for the remaining cases the new van der westhuysen a j zijlema m and battjes j a 2007 nonlinear saturation based whitecapping dissipation in swan for deep and shallow water coast eng 54 151 170 swan physics yielded better results than the standard physics of komen g j hasselmann s hasselmann k 1984 on the existence of a fully developed wind sea spectrum j phys oceanogr 14 1271 1285 except for persistent overestimations that were found for short fetches the present data set contains many interesting cases for detailed model validation and for further studies into the evolution of wind waves in shallow lakes

vsp traveltime inversion near surface issues p wave velocity information obtained from vertical seismic profiles vsps can be useful in imaging subsurface structure either by directly detecting changes in the subsurface or as an aid to the interpretation of seismic reflection data in the shallow subsurface p wave velocity can change by nearly an order of magnitude over a short distance so curved rays are needed to accurately model vsp traveltimes we used a curved ray inversion to estimate the velocity profile and the discrepancy principle to estimate the data noise level and to choose the optimum regularization parameter the curved ray routine performed better than a straight ray inversion for synthetic models containing high velocity contrasts the application of the inversion to field data produced a velocity model that agreed well with prior information these results show that curved ray inversion should be used to obtain velocity information from vsps in the shallow subsurface

a physical model of sea wave period from altimeter data a physical model for sea wave period from altimeter data is presented physical roots of the model are in recent advances of the theory of weak turbulence of wind driven waves that predicts the link of instant wave energy to instant energy flux to from waves the model operates with wave height and its spatial derivative and does not refer to normalized radar cross section 0 measured by the altimeter thus the resulting formula for wave period does not contain any empirical parameters and does not require features of particular satellite altimeter or any calibration for specific region of measurements a single case study illustrates consistency of the new approach with previously proposed empirical models in terms of estimates of wave periods and their statistical distributions the paper brings attention to the possible corruption of dynamical parameters such as wave steepness or energy fluxes to from waves when using the empirical approaches applications of the new model to the studies of sea wave dynamics are discussed

two faces of enso induced surface waves during the tropical cyclone season abstract the response of the wave climate to tropical cyclones tcs is investigated using the significant wave height swh observed from satellites and the wavewatch iii ww3 model tropical cyclone wind generates local waves wind seas under the tc and longer period waves swells that propagate long distances the genesis location intensity and frequency of tropical cyclones over the global ocean are strongly affected by the phases of the el nino southern oscillation enso it is shown that the interannual variation of global ocean surface waves in the subtropics during summer is dominated by enso related tc activity in particular in the subtropical western north pacific the wind power is stronger in the tc season before an el nino and weaker before a la nina these enso related tc variations are shown through composite and empirical orthogonal function analyses as well as modeling to dominate the spatial distribution and temporal variation of the swh over the western north pacific the model confirms that longer period waves swells are driven into northern south china sea toward japan in mid latitudes and toward the central pacific along the equator due to enso related tc activities the wind power and swh over the subtropical western north pacific lead and regress well with the enso index suggesting that they may potentially serve as useful enso predictors

fetch and duration limited nature of surface wave growth inside tropical cyclones with applications to air sea exchange and remote sensing abstractthe 2d wavenumber spectra collected by an airborne scanning radar altimeter in hurricane hunter missions are used to investigate the fetch and duration limited nature of wave growth inside hurricanes despite the much more complex wind forcing conditions the dimensionless growth curves obtained with the wind wave triplets reference wind velocity significant wave height and dominant wave period inside hurricanes except near the eye region are comparable to the reference similarity counterparts constructed with the wind wave triplets collected in field experiments conducted under ideal quasi steady fetch limited conditions in dimensionless terms the youngest waves are in the back quarter of the hurricane in the northern hemisphere the dimensionless frequency decreases systematically counterclockwise ccw and the most mature waves are in the left hand sector except for those waves near the eye region the dominant wave phase speeds are about 0 32 to 0 71 times of the local wind speed

dimensionally consistent similarity relation of ocean surface friction coefficient in mixed seas abstractapplying wavelength scaling dimensionally consistent expressions of the ocean surface friction coefficient can be developed for both wind sea and mixed sea in the ocean for a wind sea with a monopeak wave spectrum the natural choice of the scaling wavelength is that of the spectral peak component for a mixed sea with a multipeak spectrum the peak component in the wind sea portion of the wave spectrum is not a good reference wavelength a much better scaling wavelength is the weighted average of swell and wind sea following the consideration of equivalent momentum in the wave field the resulting friction coefficient c 2 is referenced to the wind speed at one half of the scaling wavelength u 2 instead of c10 referenced to the neutral wind speed at 10 m elevation u10 although referencing the wind speed at a fixed elevation such as u10 is of practical necessity u 2 is physically significant as the free stream velocity in wave modulated boundary layer flows a simple procedure to apply the s

hydraulic conductivity imaging from 3 d transient hydraulic tomography at several pumping observation densities 1 3 d hydraulic tomography 3 d ht is a method for aquifer characterization whereby the 3 d spatial distribution of aquifer flow parameters primarily hydraulic conductivity k is estimated by joint inversion of head change data from multiple partially penetrating pumping tests while performance of 3 d ht has been studied extensively in numerical experiments few field studies have demonstrated the real world performance of 3 d ht here we report on a 3 d transient hydraulic tomography 3 d tht field experiment at the boise hydrogeophysical research site which is different from prior approaches in that it represents a baseline analysis of 3 d tht performance using only a single arrangement of a central pumping well and five observation wells with nearly complete pumping and observation coverage at 1 m intervals we jointly analyze all pumping tests using a geostatistical approach based on the quasi linear estimator of kitanidis 1995 we reanalyze the system after progressively removing pumping and or observation intervals significant progressive loss of information about heterogeneity is quantified as reduced variance of the k field overall reduced correlation with slug test k estimates at wells and reduced ability to accurately predict independent pumping tests we verify that imaging accuracy is strongly improved by pumping and observational densities comparable to the aquifer heterogeneity geostatistical correlation lengths discrepancies between k profiles at wells as obtained from ht and slug tests are greatest at the tops and bottoms of wells where ht observation coverage was lacking

reduction of wind stress due to swell at high wind conditions 1 wind stress over the ocean depends on the sea surface roughness which is determined by the sea state on one hand underdeveloped wind seas rougher than their fully developed counterpart increase the drag on the other hand the presence of swell can modify wind stress by modifying the wind sea roughness this latter mechanism is believed to have a great impact at high winds whenever underdeveloped local waves coexist with swell detailed measurements of wind stress and wavefield in fetch limited growth conditions were made in an area subjected to strong and persistent winds through the analysis of wavefield observations it is found that the presence of swell dampens the short wind waves the observed attenuation is greater for younger wind seas and decreases as the wind waves become older results obtained from modeling the interaction of wind waves and the air flow above point out that the attenuation of short wind waves causes a reduction of the wave supported stress which in turn decreases the total wind stress

characterizing the heterogeneity and correlation of perchloroethene sorption and hydraulic conductivity using a facies based approach a facies based approach was used to delineate both geochemical and physical aquifer property heterogeneity specifically the parameters considered were the sorption coefficient kd for a model organic contaminant and hydraulic conductivity k inferred from the particle size distribution subfacies sized samples were analyzed for both tetrachloroethene kd and k in a vertical core of the borden aquifer both parameters were correlated with the six sedimentary facies identified within the vertical core as a consequence of their relations to sedimentary facies significant positive correlations between ln k and ln kd which were different from the core scale correlation and different from each other were identified for some facies fades specific correlations generally resulted in improved statistics i e higher correlation coefficients and reduced confidence intervals compared to the core scale correlation the results suggest that a facies based approach can be useful in characterizing the heterogeneity of the transport properties of sedimentary aquifers

water waves excited by near impulsive wind forcing only limited information is currently available on the evolution of waves generated by wind that varies in time and in particular on the initial stages of wind wave growth from rest under a suddenly applied wind forcing the emerging wind wave field varies in time as well as in space detailed knowledge of wave parameter distributions under those conditions contributes to a better understanding of the mechanisms of wind wave generation in the present study the instantaneous surface elevation and two components of the instantaneous surface slope were recorded at various fetches in a small scale experimental facility under nearly impulsive wind forcing numerous independent realizations have been recorded for each selection of operational conditions sufficient data at a number of fetches were accumulated to calculate reliable ensemble averaged statistical parameters of the evolving random wind wave field as a function of the time elapsed from activation of wind forcing distinct stages in the wave evolution process from appearance of initial ripples to emergence of a quasi steady wind wave field were identified the experimental results during each stage of evolution were analysed in view of the viscous instability theory by kawai j fluid mech vol 93 1979 pp 661 703 and the resonance model by phillips j fluid mech vol 2 1957 pp 417 445

smooth inversion of vsp traveltime data vertical seismic profile vsp direct arrivals provide an insitu measurement of traveltime with depth into the earth in this note we describe a weighted damped least squares inversion of vsp traveltimes for a smooth velocity depth function that inherently reveals the resolution of the data smooth velocity depth profiles of this type are suitable for migration or as a starting models for waveform inversion or tomography the application of this inversion is particularly simple requiring only the value of the damping parameter to be determined and this value is determined from residual statistics

the dependence of wind stress on wave height and wind speed three near neutral boundary layer data sets were investigated with the aim of finding a dependence of wind stress on both wind speed and significant wave height the data set most representative of open ocean wave height wind speed and momentum flux conditions was selected and analyzed by means of the least squares method to produce a new parameterization for the wind stress as a function of both wind speed and significant wave height this study shows that the wind stress and consequently the drag coefficient decreases with increasing wave height for a fixed wind speed the study also shows that the curvature of the wind profile decreases with increasing wave height and that the cdn a b 10 form for the drag coefficient parameterization is inadequate a drag coefficient that applies to both smooth and rough flows is proposed these results are more applicable for open ocean deep water conditions and less applicable for sheltered closed shallow water sites

single station spectral discrimination using coda waves spectral discrimination methods applied at regional distances are based on the observation that there is a difference in the frequency content of the seismic waves radiated from the source region of earthquakes and explosions we have investigated a spectral discrimination method that exploits the scattered energy contained in the event codas of seismograms to measure the relative source excitation of earthquakes and explosions as a function of frequency key strengths of the coda method include the following 1 it is not affected by source radiation pattern because the scattering process averages the radiation over the focal sphere 2 path corrections are not required with the coda method because coda waves are scattered throughout a common crustal volume 3 it can be successfully applied using data from only a single station and 4 it can be successfully applied using data with clipped direct arrivals to implement the coda method we first estimate a type curve which represents the average shape of all the individual coda decay curves for a particular frequency band the shape of the type curve as well as the shape of all individual coda decay curves is controlled by the scattering and attenuation properties of the crustal volume sampled by the coda waves a common path effect the amplitude of the type curve is not defined and we arbitrarily adjust it to have a zero mean the amplitude difference between an individual event coda decay curve and the type curve provides a relative measure of the event s source size within the particular frequency band we define this amplitude difference as the relative source factor our approach exploits all of an event s usable coda for each spectral measurement thus providing a more stable measure of relative source size than could be obtained from using a predefined fixed length time window analysis of 27 nevada test site explosions and 15 southern great basin earthquakes 3 1 m 4 7 shows that the source factor difference between the 0 5 to 1 and 2 to 4 hz bands plotted against the 1 to 2 hz source factor is a stable event discriminant the method reliably distinguishes small explosions from small earthquakes 3 0 m 3 5 even if the explosions are overburied because the coda method requires only one seismic station we believe that it would be especially useful in identifying small clandestine underground nuclear tests that occur far from established networks

observations in support of rg scattering as a source for explosion s waves regional and local recordings of the 1997 kazakhstan depth of burial experiment abstract in august and september of 1997 three 25 ton chemical explosions were detonated at nominal depths of 550 300 and 50 m in boreholes at the former soviet test site at balapan kazakhstan one objective of this experiment was to evaluate the effect of differing source depth on the regional wave field analysis of regional seismic phases lead to the observation that regional p s wave amplitude ratios in the 1 to 5 hz band increase as a function of source depth however at frequencies greater than about 5 hz the relative amplitudes of p and s waves remain approximately constant for the differing depth shots similarly regional coda spectra are amplified in the 1 to 5 hz band for the shallow shots at local distances rg is the dominant seismic phase with peak amplitudes in the 0 7 to 5 hz range and rg is strongest for the shallower shots within the short distance spanned by the local stations rg is rapidly attenuated and the attenuation is accompanied by a significant shift in peak amplitude toward lower frequency at regional distances rg is below the noise level the coincident frequency band in which local rg rapidly loses energy and regional s phases are amplified points toward rg scattering as the dominant mechanism causing the discrepancies between p s amplitude ratios in this study these observations are particularly relevant to the understanding of physical processes affecting regional p s discriminants and may lead to improvements in discriminant methods

wave follower field measurements of the wind input spectral function part ii parameterization of the wind input abstract nearly all of the momentum transferred from wind to waves comes about through wave induced pressure acting on the slopes of waves known as form drag direct field measurements of the wave induced pressure in airflow over water waves are difficult and consequently rare those that have been reported are for deep water conditions and conditions in which the level of forcing measured by the ratio of wind speed to the speed of the dominant spectral peak waves is quite weak u10 cp 3 the data reported here were obtained over a large shallow lake during the australian shallow water experiment auswex the propagation speeds of the dominant waves were limited by depth and the waves were correspondingly steep this wider range of forcing and concomitant wave steepness revealed some new aspects of the rate of wave amplification by wind the so called wind input source function in the energy balance equation for wind driven water waves it was found that the exponential growth rate parameter fra

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

ocean surface wave spectra inside tropical cyclones abstractdirectional wave spectra acquired in hurricane reconnaissance missions are compared with wind wave spectral models the comparison result is quantified with two indices of model measurement spectral agreement in the main region of hurricane coverage the indices vary sinusoidally with the azimuth angle referenced to the hurricane heading while showing a weak dependence on the radial distance from the hurricane center the measured spectra agree well with three models evaluated in the back and right quarters and they are underdeveloped in the front and left quarters the local wind and wave directions also show a weak radial dependence and sinusoidal variation along the azimuth the wind and wave vectors are almost collinear in the back and right quarters they diverge azimuthally and become almost perpendicular in the left quarter the azimuthally cyclical correlation between the indices of spectral agreement and the wind wave directional difference is well described by the sinusoidal variations

directional spectra of seas near full development abstract estimates of the directional wave spectrum have been obtained from a data buoy in the southwest approaches to the british isles four years of simultaneous wave and wind data measured at the data buoy were screened for conditions approaching full development the observed frequency spectra were made nondimensional using the similarity law of kitaigorodskii and then averaged over six wind speed classes comparisons are made with the pierson moskowitz spectrum for fully developed seas for wind speeds at the 10 m level below 16 m s 1 the average spectrum lies consistently below the pierson moskowitz form while for higher wind speeds the spectra in the region of the peak have similar values to this spectrum similarly values of the nondimensional wave energy are significantly lower than the pierson moskowitz value for wind speeds less than 16 m s 1 for higher wind speeds the nondimensional wave energy is close to the pierson moskowitz value the directional spread was studied using two parame

traveltime inversion of vertical radar profiles traveltimes of direct arrivals in vertical radar profiles vrps are tomographically inverted to estimate the earth s electromagnetic em velocity between a surface transmitter and a downhole receiver we determine the 1d interval velocity model that best fits the first arrival traveltimes by using a weighted damped least squares inversion scheme we assess the accuracy of the velocity model using synthetic traveltimes from a known velocity distribution model simulating an unconfined aquifer the inverted velocity profile closely matched the velocity profile of the input model in the synthetic examples using vertical radar profile data from an unconfined aquifer near boise idaho we inverted traveltimes to obtain velocity estimates at the well location the velocity change at a depth of 2 0 m corresponds well with the measured depth to the water table of 1 95 m and at depths between 2 and 18 m the velocities ranged between 0 06 and 0 1 m ns our estimates approximately match the velocity distribution determined from neutron derived porosity logs at depths greater than about 2 m an important function of inverse methods is to assess quantitatively and qualitatively the uncertainty of inverted velocity estimates we note that the velocity values in the upper and lower parts of the inverted model are not as well constrained compared to those between the depths of 4 and 13 m from the model resolution and model covariance matrices of the real data inversion we determine theuncertainty in ourvelocity model leading to more reliable interpretations of the subsurface

multivariate analysis of cross hole georadar velocity and attenuation tomograms for aquifer zonation 1 we have investigated the potential of combining cross hole georadar velocity and attenuation tomography as a method for characterizing heterogeneous alluvial aquifers a multivariate statistical technique known as k means cluster analysis is used to correlate and integrate information contained in velocity and attenuation tomograms cluster analysis allows us to identify objectively the major common trends in the tomographic data and thus to reduce the information to a limited number of characteristic parameter combinations the application of this procedure to two synthetic data sets indicates that it is a powerful tool for converting the complex relationships between the tomographically derived velocity and attenuation structures into a lithologically and hydrologically meaningful zonation of the probed region in addition these synthetic examples allow us to evaluate the reliability of further petrophysical parameter estimates we find that although absolute values of the tomographically inferred petrophysical parameters often differ significantly from the actual parameters the clustering approach enables us to reliably identify the major trends in the petrophysical properties finally we have applied the approach to a cross hole georadar data set collected in a well studied alluvial aquifer a comparison of the clustered tomographic section with well log data demonstrates that our approach delineates the hydrostratigraphic zonation

regional source discrimination of small events based on the use of lg wavetrain nuclear monitoring requires identification of small events observed at regional distances for which lg is generally the largest seismic phase recent research including ours has provided significantly better understanding of the generation of lg from explosions but the new concepts have not yet been fully exploited for improving discrimination between low magnitude explosions and earthquakes in different regions of the world our analysis of spectrograms which display spectral energy versus time shows that lg from explosions alone is generally followed by several distinct arrivals with progressively lower frequency contents probably due to the scattering of explosion generated rg into s at several discrete near source locations this promising new discriminant may offer a distinct advantage over other seismic methods of discrimination since it may not require the region of interest to be calibrated with the help of earlier known type seismic events moreover regional discrimination based on the lg wavetrain can be especially useful when signal to noise considerations for a small event preclude the use of other seismic phases

velocity determination from offset vertical seismic profiling data two methods of computing interval velocities from offset vertical seismic profiles are developed based on a horizontally layered earth model the first method is a simple iteration procedure by which layer velocities are sequentially computed for any given layer the take off angle for the ray arriving at the geophone at the bottom of the layer is varied until the velocity computed from travel time differs from the velocity obtained from snell s law by less than some specified value this is similar to the shooting method in ray tracing this method requires as many layers as geophone locations the second method is more general and the only requirements are that the number of layers be equal to or smaller than the number of geophone locations and that the rays arrive at the geophones from above this method is based on the iterative solution of a linearized problem obtained by expanding travel times and horizontal distances in taylor series as functions of velocities and p parameters up to first order in dv s and dp s perturbations in velocities and p parameters respectively and assuming initial estimates vo s and po s close to the optimum solution the resulting linear system is solved using a simplified version of the levenberg marquardt algorithm due to the simple structure of the ensuing matrix of derivatives for each iteration the problem reduces to the solution of an inverse problem for the velocities alone plus the solution of a vector equation for the p parameters this method is fast and convergence is attained even in the case of poor initial estimates

regional magnitude scaling transportability and ms mb discrimination at small magnitudes data sets of mb pn and mb lg measurements are presented for three continental regions in order to investigate scaling relationships with moment magnitude w and event discrimination at small magnitudes compilations of published measurements are provided for eastern north american and central asian earthquakes and new measurements are reported for earthquakes located in western united states statistical tests on w mb relationships show that the mb lg scale of nurru 1973 is transportable between tectonic regions and a single unified w mb lg relationship satisfies observations for m 6 5 in all regions a unified relationship is also developed for nuclear explosions detonated at the nevada test site and test sites of the former soviet union regional mb for explosions scale at higher rates than for earthquakes and of significance is the finding that mb pn for explosions scales at a higher rate than mb lg a model is proposed where differences in scaling rates are related to effects of spectral overshoot and near field rg scattering on the generation of pn and lg waves by explosions for earthquakes mb pn and mb lg scale similarly showing rates near 1 0 or 2 3 log1omo seismic moment

the growth rate of finite depth wind generated waves abstract fetch limited wind wave experiments traditionally investigate the growth of wave energy with distance from shore donelan m skafel m graber h liu p schwab d venkatesh s 1992 on the growth rate of wind generated waves atmos ocean 30 457 478 have however shown that for deep water conditions it is advantageous to investigate the differential growth between points located along the fetch based on the extensive data set collected by young i r verhagen l a 1996a the growth of fetch limited waves in water of finite depth part i total energy and peak frequency coastal eng 28 47 78 this approach has been extended to finite depth conditions the data clearly show that at short fetches the growth rate is comparable to deep water conditions at longer fetches the finite depth influences increase and the growth rate decreases compared to deep water finally the waves approach a depth limited state where the growth rate becomes zero based on the observed differential growth between measurement stations a relationship is developed which can be integrated to yield the development of the total energy with fetch this relationship is significantly more flexible than previous finite depth growth relationships cases in which the water depth and or wind speed vary with fetch can be investigated in particular it is shown that the development of the atmospheric boundary layer with fetch has a significant influence on the observed wave growth by the inclusion of a realistic relationship for the boundary layer development it is shown that apparently anomalous features of the young i r verhagen l a 1996a the growth of fetch limited waves in water of finite depth part i total energy and peak frequency coastal eng 28 47 78 data set can be explained

vertical radar profiling combined analysis of traveltimes amplitudes and reflections abstractvertical radar profiling vrp is a single borehole geophysical technique in which the receiver antenna is located within a borehole and the transmitter antenna is placed at one or various offsets from the borehole today vrp surveying is primarily used to derive 1d velocity models by inverting the arrival times of direct waves using field data collected at a well constrained test site in germany we evaluated a vrp workflow relying on the analysis of direct arrival traveltimes and amplitudes as well as on imaging reflection events to invert our vrp traveltime data we used a global inversion strategy resulting in an ensemble of acceptable velocity models and thus it allowed us to appraise uncertainty issues in the estimated velocities as well as in porosity models derived via petrophysical translations in addition to traveltime inversion the analysis of direct wave amplitudes and reflection events provided further valuable information regarding subsurface properties and architecture the

buoy measurements of wind wave relations during hurricane matthew in 2016 abstractstudies suggested that neutral stability wind speed at 10 m u10 9 m s 1 and wave steepness hs lp 0 020 can be taken as criteria for aerodynamically rough ocean surface and the onset of

vsp interval velocities from traveltime inversion a principal use of the vertical seismic profile vsp is to determine the variation of seismic velocity with depth presented here is a discussion of the errors involved with the time picks of a vsp survey and several methods currently used to calculate a velocity section from these time picks another technique is proposed based on the least squares inversion of the traveltimes to arrive at a better estimate and statistical description of the velocity section this technique uses the levenberg marquardt damped least squares formulation and ray tracing through a horizontally layered medium to iteratively refine the velocity section the accuracy and robustness of the procedure are investigated by inverting noisy traveltime curves and comparing these results to the original model velocity section agreement is found to be good one interesting feature of the inverse procedure is that for certain geometries it can resolve a few velocity layers even though there are no measurements made inside those layers three actual vsp surveys are analyzed and compared to their corresponding sonic logs in two of the surveys it appears that there is some velocity dispersion velocity changes associated with gas saturation are evident on one of the surveys

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

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

estimating porosity with ground penetrating radar reflection tomography a controlled 3 d experiment at the boise hydrogeophysical research site 1 to evaluate the uncertainty of water saturated sediment velocity and porosity estimates derived from surface based ground penetrating radar reflection tomography we conducted a controlled field experiment at the boise hydrogeophysical research site bhrs the bhrs is an experimental well field located near boise idaho the experimental data set consisted of 3 d multioffset radar acquired on an orthogonal 20 30 m surface grid that encompassed a set of 13 boreholes experimental control included 1 1 d vertical velocity functions determined from traveltime inversion of vertical radar profiles vrp and 2 neutron porosity logs we estimated the porosity distribution in the saturated zone using both the topp and complex refractive index method crim equations and found the crim estimates in better agreement with the neutron logs we found that when averaged over the length of the borehole surface derived velocity measurements were within 5 of the vrp velocities and that the porosity differed from the neutron log by less than 0 05 the uncertainty however is scale dependent we found that the standard deviation of differences between ground penetrating radar derived and neutron log derived porosity values was as high as 0 06 at an averaging length of 0 25 m but decreased to less than 0 02 at length scale of 11 m additionally we used the 3 d porosity distribution to identify a relatively high porosity anomaly i e local sedimentary body within a lower porosity unit and verified the presence of the anomaly using the neutron porosity logs since the reflection tomography approach requires only surface data it can provide rapid assessment of bulk hydrologic properties identify meter scale anomalies of hydrologic significance and may provide input for other higher resolution measurement methods

observations of the directional distribution of ocean wave energy in fetch limited conditions abstract directional energy distributions of wind generated waves were observed with a relatively high directional resolution in fairly homogeneous and stationary wind fields in fetch limited conditions using stereophotography of the sea surface in a situation that is traditionally considered as the ideal fetch limited wave generation situation the shapes of the observed distributions were found to agree well with the cos2s 2 model proposed by longuet higgins et al 1963 in non ideal situations in which the wind slanted across the upwind coastline or in which the upwind coastline was irregular the shapes of the directional distributions were strongly influenced by the geometry of the upwind coastline this suggests that the process of wave generation is directionally decoupled

low frequency mean square slopes and dominant wave spectral properties toward tropical cyclone remote sensing spectral properties near the dominant wave region influence significantly the surface roughness relevant to ocean remote sensing employing low frequency microwave sensors the critical parameters characterizing dominant waves are wind speed and dimensionless spectral peak frequency which is the inverse wave age the dimensionless spectral peak frequency can be expressed as an equivalent dimensionless fetch or duration the connection between dominant waves and surface roughness is the spectral slope this paper presents a surface wave spectral model designed for low frequency microwave remote sensing with special emphasis on tropical cyclone tc applications the key elements of the spectral model are 1 a general spectral function with coefficients accommodating a variable spectral slope and 2 a parametric function connecting the spectral slope and wind speed which is established with the mean square slope mss observations obtained inside hurricanes by the global positioning system reflectometry technique in order to make use of the mss observations inside hurricanes parametric models of the spatial distributions of wind speed and dimensionless spectral peak frequency inside tcs are developed the parametric models are based on the wind and wave similarity relationships derived from analyses of hurricane hunter measurements

recognition of units in coarse unconsolidated braided stream deposits from geophysical log data with principal components analysis returns from drilling in unconsolidated cobble and sand aquifers commonly do not identify lithologic changes that may be meaningful for hydrogeologic investigations vertical resolution of saturated quaternary coarse braided stream deposits is significantly improved by interpreting natural gamma g epithermal neutron n and electromagnetically induced resistivity ir logs obtained from wells at the capital station site in boise idaho interpretation of these geophysical logs is simplified because these sediments are derived largely from high gamma producing source rocks granitics of the boise river drainage contain few clays and have undergone little diagenesis analysis of g n and ir data from these deposits with principal components analysis provides an objective means to determine if units can be recognized within the braided stream deposits in particular performing principal components analysis on g n and ir data from eight wells at capital station 1 allows the variable system dimensionality to be reduced from three to two by selecting the two eigenvectors with the greatest variance as axes for principal component scatterplots 2 generates principal components with interpretable physical meanings 3 distinguishes sand from cobble dominated units and 4 provides a means to distinguish between cobble dominated units

interpretation of drill core and georadar data of coarse gravel deposits abstract pollution in the shallow subsurface has led to an increasing need of understanding how to quantitatively characterize both the heterogeneity of gravel aquifers and the influence of heterogeneity on groundwater flow and solute transport models play an important role in decision making processes especially in the context of better characterizing and in forecasting the behavior of a given geological system the objective of the present paper is the derivation of a gradual lithofacies based interpretation of outcrop drill core and ground penetrating radar gpr or georadar data of different quality the presented method allows a probability estimation of drill core layer descriptions and radarfacies types representing defined sedimentary structure types the method includes a determination of initial structure type probabilities for grain size categories and combinations thereof described in drill core layer descriptions as well as a subsequent differentiation of these structure type probabilities in an iterative process considering additional information like main constituent quantity fraction and sorting of single grain size categories color chemical precipitation layer thickness and adjacent layer the radarfacies types are calibrated with drill cores located in the vicinity of georadar sections the calibration process consists of the assignment of the calculated structure type probabilities from the drill core layer descriptions to the corresponding radarfacies types considering the proportion in thickness between drill core layers and georadar structures the structure type probabilities can be given for points along boreholes and a grid with arbitrary mesh size along georadar sections the method is applied to field examples from the rhine wiese aquifer near basel in switzerland the resulting structure type probabilities can be used for conditioning stochastic simulations of geological models however the conditioned stochastic simulation of the rhine wiese aquifer is the topic of another paper the results show the importance of a detailed sedimentological analysis of outcrops and drill cores as well as its significance on the distinction of sedimentary structure types

focused inversion of vertical radar profile vrp traveltime data the reconstruction of the gpr velocity vertical profile from vertical radar profile vrp traveltime data is a problem with a finite number of measurements and imprecise data analogous to similar seismic techniques such as the shallow down hole test used for s wave velocity profiling or the vertical seismic profiling vsp commonly used in deeper exploration the uncertainty in data accuracy and the error amplification inherent in deriving velocity estimates from gradients of arrival times make this an example of an ill posed inverse problem in the framework of tikhonov regularization theory ill posedness can be tackled by introducing a regularizing functional stabilizer the role of this functional is to stabilize the numerical solution by incorporating the appropriate a priori assumptions about the geometrical and or physical properties of the solution one of these assumptions could be the existence of sharp boundaries separating rocks with different physical properties we apply a method based o

geophysical conceptualization of a fractured sedimentary bedrock riverbed using ground penetrating radar and induced electrical conductivity summary bedrock rivers exhibit very different hydraulic and ecological regimes compared to alluvial rivers groundwater surface water interaction in rivers that flow directly on sedimentary bedrock surfaces with exposed fracture and conduit networks is generally based on alluvial river conceptual models however the dual and triple porosity systems of sedimentary rock e g matrix fractures and vugs leads to highly variable hydraulic pathways and groundwater velocities that in turn result in processes that are very different than those derived from alluvial concepts relative to alluvial rivers there has been very little direct examination of dynamic interactions such as fluxes groundwater velocities and mechanisms affecting water quality across the channel interface this is largely because bedrock rivers are difficult to instrument and monitor given their heterogeneous and anisotropic flow systems in this study we evaluate the capacity of non invasive low impact ground penetrating radar and frequency domain electromagnetic induction methods capable of detecting discrete fracture and conduit features mapping complex distributions of lithostratigraphic interfaces and providing information about formation properties along a partially exposed section of the eramosa river located in ontario canada geophysical data are supported by direct hydrogeologic and geologic information obtained from a nearby borehole piezometer cluster and a continuous 15 m rock core valuable insights were gained into the lateral extent and geometry of structurally controlled whydrostratigraphic units e g dissolution enhanced fractures epikarst and karst features which are expected to strongly influence groundwater and surface water interaction along the channel an integrated application of gpr and emi methods was necessary to fully understand the complex geometry of geologic boundaries and karst features within the shallow bedrock aquifer the identification of epikarst below fluvial sediment and its relationship to the formation of dissolution features exposed fracture conduit networks and sinkholes represents the basis for understanding the dynamic hydraulic responses between the surface water and the shallow bedrock aquifer

effective fetch and non linear four wave interactions during wave growth in slanting fetch conditions abstract wave growth in slanting fetch with wind blowing obliquely off a coast is investigated with 7 years worth of routine wave measurements in lake ijssel in the netherlands and with the swan wave model two aspects are considered in particular for this case the validity of the concept of effective fetch and the role of the non linear four wave interactions for slanting and parallel fetch conditions we found some significant deviations from the effective fetch assumption leading to 20 35 mismatch in either the peak period t p or the significant wave height h m0 respectively however the effect of discrepancies between various widely accepted wave growth formulas turned out to be even more important the wave directions during slanting fetch are significantly steered by the coastline especially in the first kilometre s off the coast the role of the non linear four wave interactions is investigated by running the swan version 40 41 wave model with three different quadruplet formulations exact quadruplet methods xnl yielded relatively strong wave steering despite the four wave interactions being relatively weak application of xnl did not lead to better overall agreement with measurements improvements for the mean wave period t m01 were offset by some deterioration for the wave height h m0

velocity variations and water content estimated from multi offset ground penetrating radar the common midpoint cmp processing technique has been shown to be effective in improving the results of ground penetrating radar gpr profiling when radar data are collected with the cmp multioffset geometry stacking increases the signal to noise ratio of subsurface radar reflections and results in an improved subsurface image an important aspect of cmp processing is normal moveout velocity analysis our objectives are to show the effect of multiple velocity analyses on the stacked radar image and particularly to demonstrate that this velocity information can also be used to determine subsurface water content most gpr surveys are very limited in spatial extent and assume that within the survey range radar velocity structure in the shallow subsurface can be adequately approximated by a single velocity function in data processing in this study we show that variation in radar velocity can be quite significant and that the stacked profile improves as the number of velocity analysis locations is increased interval velocities can be calculated from the normal moveout velocities derived in the cmp velocity analysis with some reasonable assumptions about subsurface conditions necessary for radar propagation interval velocity can be converted to an estimate of volumetric water content therefore by collecting gpr data in the multioffset cmp geometry not only is the radar profile improved but it also allows for an interpretation of subsurface variation in water content we show the application of these techniques to multioffset gpr data from the chalk river test area operated by atomic energy of canada limited