modeling ground displacement above reservoirs undergoing fluid withdrawal injection based on an ellipsoidal inhomogeneity model abstract we propose a procedure to efficiently monitor the geomechanical behavior of underground porous reservoirs undergoing fluid withdrawal injection we apply the inhomogeneity problem and invert geodetic data on subsidence uplift to calibrate and specify parameters used for geomechanical models based on pressure changes we first calculate the poroelastic strain of the reservoirs then we test it assuming uniaxial deformation on a three dimensional ellipsoidal inhomogeneity with different semi axes in a full space isotropic elastic domain and finally we apply a simple half space approximation to account for the tractions free ground surface despite its simplicity and the initial full space approximation the semi analytical model derived in this study replicates well poroelastic strains inferred by geodetic data or obtained with other analytical and numerical techniques our model is a good approximation for predicting the profile of surface deformation i e geodetic strain and once calibrated its magnitude

deep sea currents driven by breaking internal tides on the continental slope mooring data collected on the continental slope of the south china sea show that along slope deep sea bottom currents are generated when large spring internal tides internal waves with tidal frequency are observed with the maximum velocity amplitude exceeding 0 15m s the observations are consistent with predictions that near bottom breaking of internal waves can result in generation of along slope flows when these waves obliquely approach the slope a linear internal tide model in one horizontal dimension with realistic topography and stratification is used to show that the breaking of internal tides is likely due to near critical reflection on the slope combining the mooring observations and the model simulation an along slope near bottom transport of similar to 0 5sv is estimated along slope bottom flows caused by breaking internal waves potentially provide a significant way to deform continental slopes and affect deep water exchange between the marginal sea and open ocean

sand dune geometry of large rivers during floods the geometry of lower regime bed forms in several large sand bed rivers is investigated during average and flood conditions the van rijn method is revised because it generally underpredicts the dune height of most large rivers around the world during floods in large sand bed rivers upper regime plane bed is not necessarily obtained when t 25 both parameters describing dune height and dune steepness do not decrease as the transport stage parameter t increases in the range 10 t 25 the analysis of bed form data during large floods on the meuse river and the rhine river branches indicates that both the dune height and length generally increase with discharge while dune steepness remains relatively constant a reasonable approximation of the wavelength is 6 5 h where h is the flow depth the dune height varies as a function of the depth h and median grain size d50 estimates can be obtained by 2 5 h 0 7d0 350

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

geomechanical response to seasonal gas storage in depleted reservoirs a case study in the po river basin italy 1 underground gas storage ugs in depleted hydrocarbon reservoirs is a strategic practice to cope with the growing energy demand and occurs in many places in europe and north america in response to summer gas injection and winter gas withdrawal the reservoir expands and contracts essentially elastically as a major consequence of the fluid gas and water pore pressure fluctuations depending on a number of factors including the reservoir burial depth the difference between the largest and the smallest gas pore pressure and the geomechanical properties of the injected formation and the overburden the porous medium overlying the reservoir is subject to three dimensional deformation with the related cyclic motion of the land surface being both vertical and horizontal we present a methodology to evaluate the environmental impact of underground gas storage and sequestration from the geomechanical perspective particularly in relation to the ground surface displacements long term records of injected and removed gas volume and fluid pore pressure in the lombardia gas field northern italy are available together with multiyear detection of vertical and horizontal west east displacement of the land surface above the reservoir by an advanced permanent scatterer interferometric synthetic aperture radar psinsar analysis these data have been used to calibrate a 3 d fluid dynamic model and develop a 3 d transversally isotropic geomechanical model the latter has been successfully implemented and used to reproduce the vertical and horizontal cyclic displacements on the range of 8 10 mm and 6 8 mm respectively measured between 2003 and 2007 above the reservoir where a ugs program has been underway by stogit eni s p a since 1986 following a 5 year field production life because of the great economical interest to increase the working gas volume as much as possible the model addresses two ugs scenarios where the gas pore overpressure is pushed from the current 103 pi where pi is the gas pore pressure prior to the field development to 107 pi and 120 pi results of both scenarios show that there is a negligible impact on the ground surface with deformation gradients that remain well below the most restrictive admissible limits for the civil structures and infrastructures

monitoring of fluid injection and soil consolidation using surface tilt measurements temporal variations of surface tilt may be used for the noninvasive monitoring of subsurface volume change such volume changes may accompany settlement near structures the response due to fluid injection or withdrawal and excavation related activity we outline a methodology for using tilt data to estimate volume changes within poroelastic media the expressions relating subsurface volume change and surface tilt are simple and compact offering the possibility of real time monitoring the inversion of actual tilt data from a site near raymond calif generates images of fluid withdrawal from a complex fracture zone about 30 m below the surface volume changes are confined to an elongated north south zone in agreement with independent well test data we have also applied the methodology for the inversion of surface tilt to data from a grout injection experiment in los banos the technique enables us to monitor grout migration through a porous gravel

seismicity induced by gas production ii lithology correlated events induced stresses and deformation a 3d relocation technique permits precise locations of induced earthquakes geostatistical processing using the data of 87 boreholes provides the basis of a precise 3d structure with a dome geometry conventional laboratory mechanical tests performed on deep rock samples 1000 m to 5000 m define the rock properties at depths similar to those of the seismic events 1 ml 4 2 that range from 1 to 7 km

nonlinear internal waves in the south china sea observation of the conversion of depression internal waves to elevation internal waves 1 the conversion of depression nonlinear internal solitons to elevation internal waves has been observed twice at the south china sea continental shelf break shipboard x band radar tow yo ctd adcp and high frequency acoustic flow visualization of the process are presented the data focuses on up slope propagation of depression internal solitons from a water depth of 264 m to a water depth of 110 m dissipation by large amplitude shear instabilities was observed the kinetic energy density was found to be a decreasing monotonic function of range with an energy dissipation rate coefficient of 0 063 km 1 the rate of energy dissipation over the 16 5 km soliton propagation path was 0 17 w m m simple numerical models of the waveform evolution are qualitatively compared to the observations the observations extracted scale parameters and dissipation rates should be useful for testing a variety of evolution equation representations of internal soliton propagation

observation of very large and steep internal waves of elevation near the massachusetts coast 1 we report on near bottom waves of elevation with amplitude nearly half the 25 m water column very steep and propagating into a sheared turbulent wave guide the waves contained trapped cores transporting parcels of water shoreward these large waves depart strongly from weakly nonlinear and weakly nonhydrostatic conditions and challenge established paradigms they can also represent an important factor in the across shore transport of plankton and contaminants

investigating transport properties and turbidity dynamics of a karst aquifer using correlation spectral and wavelet analyses in many places throughout the world drinking water is frequently contaminated by turbidity such turbidity however as representative of particle transport can be used as to trace certain features of particle transport properties in order to investigate the relation between particle and dissolved species transport and hydrodynamics in karst systems correlation and spectral analyses were performed on time series of rainfall input signal and water level specific conductance and turbidity output signals at a karst spring system in the chalk aquifer of the lower seine valley france this system is composed of a spring connected to a sinkhole on the chalk plateau where a small creek enters the subsurface the autocorrelation functions for water level and turbidity showed a short memory effect demonstrating the short duration of the influence of flood events on these two parameters whereas specific conductance representing less mineralized storm derived water had a much longer memory effect these results were interpreted as reflecting the rapid reactivity of the spring to rain events with storage of water in the fissured chalk explaining the longer memory effect for specific conductance than for particles energy spectra computed by fast fourier transform of autocorrelation functions showed a strong structure in the output signals whereas the input signal rainfall was random thus allowing assessment and comparison of system behaviour regarding dissolved and solid transport as well as hydraulics cross correlation functions which allow an assessment of impulse response functions confirmed the low inertia of the system for water level and turbidity and the much higher inertia for specific conductance in addition to the main peak two secondary peaks in the cross correlation functions suggest the existence of additional flowpaths that might involve the contribution of other point source recharge and or delayed infiltration through the clayey surficial formation and solution pipes which could act as epikarst analysis using continuous wavelet spectra allowed a better investigation of the rainfall signal structure and highlighted a strong relationship between turbidity and rainfall which could not be deduced from the energy spectra specific spectral components in water level were isolated and a time domain reconstruction using inverse wavelet transform allowed separation of quick flow and slow flow components

parsimonious recharge discharge modeling in carbonate fractured aquifers the groundwater flow in the gran sasso aquifer central italy summary in the carbonate fractured aquifer of the gran sasso central italy numerical simulations have been applied to validate a conceptual model of the recharge discharge cycle at regional scale to identify the effective aquifer features that mostly affect the spring discharges simple parsimonious models based on few key parameters whose effective values are well constrained by previous hydrological geological studies are used input data are represented by infiltration calculated considering rainfall snowmelt and runoff in endorheic basins and effective permeability distribution estimated by geological tectonic and hydrogeological settings of the aquifer discharges of tapped springs and tunnel drainages for the 1999 2009 period have been simulated after estimating the recharge area of each monitored spring by the hydrogeological setting and checking them by mean isotope elevation values discharge monitoring has been compared with the simulations obtaining a good agreement both at seasonal and yearly time basis the simulations will also be useful for previewing discharge in drought period and evaluating protection zones of tapped springs in the territory of a national park

thermal fronts generated by internal waves propagating obliquely along the continental slope abstract rapid temperature falls occurring at semidiurnal periods are observed close to the bottom above the continental slope in the bay of biscay simultaneous current measurements reveal that the abrupt temperature decrease o 0 5 k within one minute is associated with a brief downslope current contrary to previous observations it is suggested that the flow field associated with internal waves propagating obliquely downslope is responsible for advecting denser water higher on the slope than lighter fluid resulting in a gravitationally unstable stratification the collapse of this stratification is observed as a thermal front passing the moored instruments

episodic dynamics of a sand wave field abstract the morphodynamics of a sand wave field in a flood dominant channel inside moriches inlet was monitored for eight weeks during the summer of 2005 bathymetric data show sand waves on average are 15 m long and 39 cm high with shallow slip faces the sand waves remained stationary over the eight week study the maximum peak current speeds recorded during this study only reached 60 cm s this velocity was not sufficient to cause measurable sand wave migration analysis based on work by van rijn suggests that the sand waves of this size would be created when the current velocity exceeds 80 cm s conditions not observed during this study water level data from sandy hook nj and shinnecock inlet ny show that large tidal ranges occur when a drop in barometric pressure increases the elevation of high tide and strong north winds decrease the low tide elevation during these events the current velocity may reach 80 cm s which is predicted to be strong enough to produce these sand waves this study demonstrates that high energy episodic events may control sand wave morphology at moriches inlet

observations of internal wave reflection off sloping bottoms current and temperature spectra exhibit intensification and polarization near sloping bottoms over a band of frequencies centered at the local internal wave critical frequency examples are drawn from a variety of island seamount and continental slope observations waves propagating down from mid depth change energy density wave number and azimuth when they reflect off the bottom providing a natural perturbation to the deep ocean interior internal wave spectrum deviations from linear theory are interpreted as evidence for dissipation through subsequent shear instability and or nonlinear interaction topographic features appear likely to be energy sinks for internal wave energy

the tectonic regime in italy inferred from borehole breakout data abstract in italy the horizontal stress directions are well constrained in many regions but the tectonic regime is not well known because the stress magnitudes are unknown our intention is to improve the knowledge of crustal stress in italy both at shallow depth and in low seismicity areas therefore we inferred the tectonic regime from the comparison between the depth of breakout occurrence and the physical properties of the rocks in 20 boreholes the critical value of the maximum horizontal stress for which the effective tangential stress at the borehole wall overcomes the rock strength to form breakouts could be computed from rock strength and density comparing the theoretical stress distributions for different tectonic regimes with the depth distribution of breakout occurrence it is possible to infer the tectonic regime that fits best to the breakout depth distribution we investigated boreholes up to 6 km deep located in different tectonic environments over the italian peninsula the po plain the apenninic chain the adriatic foredeep and the tyrrhenian quaternary volcanic region these wells are characterised by breakout data of good quality a b and c according to world stress map quality ranking system the results are in general agreement with the style of faulting derived from earthquake focal mechanisms and other stress indicators our results show a predominance of a normal faulting nf regime in the inner apennines and both normal faulting and strike slip faulting ss style in the surrounding regions possibly also associated with changes in the tectonic regime with depth

groundwater balance estimation in karst by using a conceptual rainfall runoff model summary a conceptual rainfall runoff model is proposed for the estimation of groundwater balance components including the influences of time variant catchment boundaries and intercatchment groundwater flows karst underground is considered as a lumped system that contains 1 soil cover 2 epikarst zone and 3 vadose and phreatic zones the soil cover receives an average rainfall in catchment as the input into the system the epikarst zone is composed of a production store and a routing store the production store contributes to the loss of water in process of evapotranspiration the routing store contributes to the retention of percolated water and the lateral distribution of groundwater recharge between internal runoff and diffuse infiltration the vadose and phreatic zones accumulate groundwater in fissures fractures and vertical shafts and produce the vadose seepage vadose flow and shaft flow components of the karst spring discharge the parameter estimation and calculation procedure assemble the moisture balance and the groundwater balance approaches the rainfall runoff model is divided in two sub models the sub model based on the moisture balance of soil cover and epikarst production store calculates effective rainfalls the sub model based on the groundwater balance of vadose and phreatic zone calculates groundwater recharges the difference between the effective rainfalls and the groundwater recharges represents the contribution of epikarst zone and non conservative and time variant components to the groundwater balance the proposed methodology is applied to the jadro spring located near the city of split in croatia the calculated groundwater balance shows that the jadro spring aquifer contains a significant storage capacity in the vadose and phreatic zones during the year the aquifer may accumulate up to 140 millions m 3 the variability of calculated catchment area is explained with the time variant catchment boundary dependent on groundwater levels and the intercatchment groundwater flows from neighboring catchments the average catchment area of 396 km 2 is estimated by using the average monthly effective rainfalls and the average monthly groundwater recharges

seasonal characteristics of internal tides on the continental shelf in the northern south china sea three across shelf acoustic doppler current profiler adcp moorings were deployed on the continental shelf in the northern south china sea in 2006 and 2007 in order to obtain time series of ocean currents during each of the three observational periods in spring autumn and winter seasons the observation was sustained for at least 1 month conductivity temperature depth data were also collected in the vicinity of these adcp moorings the two diurnal baroclinic constituents o 1 and k 1 are found to be more prominent than the semidiurnal baroclinic ones m 2 and s 2 at each mooring site which are different from the barotropic tides the highest diurnal semidiurnal baroclinic kinetic energy density exceeded 10 2 7 kj m 2 during the observational periods in each observational period the vertical structures of baroclinic tidal ellipses indicate mode 1 characteristics for o 1 and k 1 whereas some of the semidiurnal internal tides show mode 2 characteristics in autumn propagation directions of the diurnal and semidiurnal internal tides are basically across shelf and their phase speeds estimated from phase changes and buoyancy frequencies indicate deceleration of internal tides when the internal tidal waves propagate from deeper shelf break to shallower shelf the increased stratification in autumn is favorable for maintaining internal tidal waveform and preserving internal tidal energy while the intensity of the internal tidal flow decreases significantly in winter

internal bores and breaking internal tides on the oregon continental slope abstractobservations of breaking internal tides on the oregon continental slope during a 40 day deployment of 5 moorings along 43 12 n are presented remotely generated internal tides shoal onto the slope steepen break and form turbulent bores that propagate upslope independently of the internal tide a high resolution snapshot of a single bore is captured from lowered acoustic doppler current profilers ladcp ctd profiles in a 25 h time series at 1200 m the bore is cold salty over 100 m tall and has a turbulent head where instantaneous dissipation rates are enhanced e 10 6 w kg 1 and sediment is resuspended at the two deepest slope moorings 1452 and 1780 m similar borelike phenomena are observed in near bottom high resolution temperature time series mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present w kg 1 and m s 1 and observed internal tides are energetic enough to drive these enhanced dissipation rates globally the authors estimate

the morphodynamics of fluvial sand dunes in the river rhine near mainz germany i sedimentology and morphology the dynamics of large isolated sand dunes moving across a gravel lag layer were studied in a supply limited reach of the river rhine germany bed sediments dune geometry bedform migration rates and the internal structure of dunes are considered in this paper hydrodynamic and sediment transport data are considered in a companion paper the pebbles and cobbles d50 of 10 mm of the flat lag layer are rarely entrained dunes consist of well sorted medium to coarse sand d50 of 0 9 mm small pebbles move over the dunes by overpassing but there is a degree of size and shape selectivity populations of ripples in sand d50 0 6 mm and small and large dunes are separated by distinct breaks in the bedform length data in the regions of 0 7 1 m and 5 10 m ripples and small dunes may have sinuous crestlines but primarily exhibit two dimensional planforms in contrast large dunes are primarily three dimensional barchanoid forms ripples on the backs of small dunes rarely develop to maximum steepness small dunes may achieve an equilibrium geometry either on the gravel bed or as secondary dunes within the boundary layer on the stoss side of large dunes secondary dunes frequently develop a humpback profile as they migrate across the upper stoss slope of large dunes diminishing in height but increasing in length as they traverse the crestal region however secondary dunes more than 5 m in length are rare the dearth of equilibrium ripples and long secondary dunes is probably related to the limited excursion length available for bedform development on the parent bedforms large dunes with lengths between 20 m and 100 m do not approach an equilibrium geometry a depth limitation rather than a sediment supply limitation is the primary control on dune height dunes rarely exceed 1 m high in water depths of 4 m dune celerity increases as a function of the mean flow velocity squared but this general relationship obscures more subtle morphodynamics during rising river stage dunes tend to grow in height owing to crestal accumulation which slows downstream progression and steepens the dune form during steady or falling stage an extended crestal platform develops in association with a rapid downstream migration of the lee side and a reduction in dune height these diminishing dunes actually increase in unit volume by a process of increased leeside accumulation fed by secondary dunes moving past a stalled stoss toe a six stage model of dune growth and diminution is proposed to explain variations in observed morphology the model demonstrates how the development of an internal boundary layer and the interaction of the water surface with the crests of these bedload dominated dunes can result in dunes characterized by gentle lee sides with weak flow separation this finding is significant as other studies of dunes in large rivers have attributed this morphological response to a predominance of suspended load transport

seismicity induced by gas production i correlation of focal mechanisms and dome structure from august 1976 to june 1979 more than 220 seismic events were recorded by a 7 station network operating over an active gas field in france 120 earthquakes with magnitudes greater than 1 0 were selected for a detailed study in order to understand the seismic response to a decrease in the gas reservoir pressure of 50 mpa composite focal mechanisms were determined for these events we found that where preexisting fractures were known from well logs faults with the most favorable orientation were reactivated in the part of the gas field where no preexisting faults were known orientation of the fracture planes was close to the orientations of stratigraphic interfaces our kinematic model constrained by the distribution of the earthquakes and their focal mechanisms consists of the downward dropping of a block located close to the top of the gas field the main faults as defined by the spatial density of the seismic activity define the limits of this block the displacements observed along these faults can be either normal or reverse mechanism dependent on the preexisting orientation of each fault another important result is the evidence that the depletion of the gas reservoir exerts the major influence on local seismic displacements obscuring the effect of regional setting

features of spatiotemporal groundwater head variation using independent component analysis abstract the effect of external stimuli on a groundwater system can be understood by examining the features of spatiotemporal head variations however the head variations caused by various external stimuli are mixed signals to identify the stimuli features of head variations we propose a systematic approach based on independent component analysis ica frequency analysis cross correlation analysis well selection strategy and hourly average head analysis we also removed the head variations caused by regional stimuli e g rainfall and river stage from the original head variations of all the wells to better characterize the local stimuli features e g pumping and tide in the synthetic case study the derived independent component ic features are more consistent with the features of the given recharge and pumping than the features derived from principle component analysis in a real case study the ics associated with regional stimuli highly correlated with field observations and the effect of regional stimuli on the head variation of all the wells was quantified in addition the tide agricultural industrial and spring pumping features were characterized therefore the developed method can facilitate understanding of the features of the spatiotemporal head variation and quantification of the effects of external stimuli on a groundwater system

lumped and distributed approaches to model natural recharge in semiarid karst aquifers summary recharge is a key component of the hydrological balance in groundwater systems particularly in arid and semiarid settings recharge often takes place during isolated rainfall episodes as a result pumping might cause groundwater levels to fall continuously for long periods of time even if yearly abstractions remain below the average replenishment rate recharge is naturally difficult to quantify as it depends on a complex variety of factors indirect techniques based on mathematical models have long since been advocated as valuable means to estimate recharge this paper presents a methodology to estimate groundwater recharge in quick response semiarid karst aquifers lumped and distributed models are used to evaluate the fraction of rainfall that ultimately results in aquifer recharge as well as the correlation between the magnitude of rainfall events and infiltration rates modelling results are then compared with direct observations of the recharge processes and discussed to evaluate the implications of time scales this study is demonstrated through a case specific application to the ventos aquifer an intensively exploited carbonate system located in one of the driest areas of peninsular spain overall both approaches perform similarly although the lumped model exhibits a better agreement with field records results reflect the nonlinear nature of the rainfall recharge ratio the fraction of rainfall that ultimately recharges the aquifer seems to increase exponentially with the magnitude of the event

gravity currents facilitate formation of high frequency internal solitons and bores at the base of the fraser delta in the southern strait of georgia

solibore induced sediment resuspension in the faeroe shetland channel 1 high resolution measurements of temperature and current velocity over the seabed in the faeroe shetland channel fsc reveal an intense internal wave train referred to as a solibore propagating up the continental slope in addition to enhancing turbulent mixing a rotor formed at the leading edge of the solibore generates sediment fluxes o 102 greater than background levels the interaction of solibores which appear to evolve from baroclinic bores with the seabed and the resulting rotor provides a dominant mechanism for the upward transport of sediment over continental slopes that may counteract downward avalanching of material by gravity

very large subaqueous sand dunes on the upper continental slope in the south china sea generated by episodic shoaling deep water internal solitary waves abstract very large subaqueous sand dunes were discovered on the upper continental slope of the northern south china sea the dunes were observed along a single 40 km long transect southeast of 21 93 n 117 53 e on the upper continental slope in water depths of 160 m to 600 m the sand dunes are composed of fine to medium sand with amplitudes exceeding 16 m and crest to crest wavelengths exceeding 350 m the dunes apparent formation mechanism is the world s largest observed internal solitary waves which generate from tidal forcing on the luzon ridge on the east side of the south china sea propagate west across the deep basin with amplitudes regularly exceeding 100 m and dissipate extremely large amounts of energy via turbulent interaction with the continental slope suspending and redistributing the bottom sediment while subaqueous dunes are found in many locations throughout the world s oceans and coastal zones these particular dunes appear to be unique for two principal reasons their location on the upper continental slope away from the influence of shallow water tidal forcing deep basin bottom currents and topographically amplified canyon flows and their distinctive formation mechanism approximately 60 episodic extremely energetic large amplitude events each lunar cycle

nonlinear shear instabilities of alongshore currents over barred beaches the nonlinear dynamics of finite amplitude shear instabilities of alongshore currents in the nearshore surf zone over barred beach topography are studied using numerical experiments these experiments extend the recent study of allen et al 1996 which utilized plane beach constant slope topography by including shore parallel sandbars the model involves finite difference solutions to the nonlinear shallow water equations for forced dissipative initial value problems and employs periodic boundary conditions in the alongshore direction effects of dissipation are modeled by linear bottom friction forcing for the alongshore currents is specified using a model formulated by thornton and guza 1986 t g distinct classes of flows develop depending on the dimensionless parameter q the ratio of an advective to a frictional timescale for q greater than a critical value qc the flows are linearly stable for q qc q 0 the flow is unstable for small values of q equilibrated shear waves develop that propagate alongshore at phase speeds and wavelengths that are in agreement with predictions from linear theory for the most unstable mode at intermediate values of q unsteady vortices form and exhibit nonlinear interactions as they propagate alongshore occasionally merging pairing or being shed seaward of the sandbar at the largest values of q examined the resulting flow field resembles a turbulent shear flow a net effect of the instabilities at large aq is to distribute the time averaged alongshore momentum from local maxima of the t g forcing located over the sandbar and near the shore into the region of the trough the across shore structure of the time averaged alongshore current is in substantially better qualitative agreement with observations than that given by a steady frictional balance with t g forcing the results point to the possible existence in the nearshore surf zone of an energetic eddy field associated with instabilities of the alongshore current

rainfall runoff relations for karstic springs part i convolution and spectral analyses karstic basins contain large reserves of subsurface water in this paper three karstic systems located in the pyrenees mountains ariege france are studied long records of rainfall and discharge rates for these karstic springs are available sampled at different rates daily hourly and half hourly this study aims at illustrating and assessing the capabilities and limitations of linear black box methods for analysing rainfall runoff type relationships and reconstructing runoffs from rainfall rate data using such systems in this study precipitation and discharge rates are considered as two autocorrelated and cross correlated stochastic processes a linear and stationary rainfall runoff model is adopted which is used for identification and simulation purposes different versions are analysed including a model based on a convolution integral between the precipitation rate p and a transfer function h t which can be thought of as the unit impulse response of the system it is shown that this linear stochastic model i e the statistical version although accurate in some respects does not represent the hydraulic behaviour of the system very well during low flow episodes and floods it is also shown that the use of fourier analysis alone does not lead to a satisfactory reconstitution of observed runoff sequences for these reasons the use of non linear random process input output models based on volterra integral series is proposed and discussed

intense variable mixing near the head of monterey submarine canyon abstract a microstructure survey near the head of monterey submarine canyon the first in a canyon confirmed earlier inferences that coastal submarine canyons are sites of intense mixing the data collected during two weeks in august 1997 showed turbulent kinetic energy dissipation and diapycnal diffusivity up to 103 times higher than in the open ocean dissipation and diapycnal diffusivity within 10 km of the canyon head were among the highest observed anywhere e 1 1 10 6 w kg 1 k 1 0 10 2 m2 s 1 mixing occurred mainly in an on axis stratified turbulent layer with thickness and intensity increasing from neap to spring tide strain spectra showed a gentler than k 1z rolloff suggesting that critical reflection and scattering may push energy into high wavenumbers dissipation dependence on shear appears to be much weaker in the canyon than in the open ocean with indications that the dependence maybe as low as e s coastal canyons may account for a small but significant fraction of the int

the shaping of continental slopes by internal tides the angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins 2 to 4 degrees intensification of near bottom water velocities and bottom shear stresses caused by reflection of semi diurnal internal tides affects sedimentation patterns and bottom gradients as indicated by recent studies of continental slopes off northern california and new jersey estimates of bottom shear velocities caused by semi diurnal internal tides are high enough to inhibit deposition of fine grained sediment onto the slopes

alongslope current generated by obliquely incident internal gravity waves a simple laboratory experiment in stratified salt water demonstrates that an obliquely incident internal gravity wave generates a mean horizontal current when approaching a sloping boundary from above the alongslope current is in the same direction as the transverse component of wave propagation and coexists with a turbulent bore propagating diagonally up and along the slope mean flow generation is observed for vertical angles of incidence above and below the critical angle as well as for steeper angles in which the viscous dissipation of waves is smaller initially

gis based regionalization of a karst water system in xishan mountain area of taiyuan basin north china summary a clear description of the structural features and path of groundwater flow for a karst water system is a basis for establishing a hydrogeologic conceptual model in a basin in a case study of the karst system of xishan mountain of taiyuan basin typical of hydrogeologic systems in north china and elsewhere in the world we extracted quantitative information of hydrogeologic structure and regionalized the interior structure of the karst water system using a geographic information system gis technique the information extracted from lithofacies paleogeography geology tectonics and hydrogeology includes the isolines of the top of the regional aquiclude the projected section of both planes of a fault and plotting the regional saturated zone the passage zone and the local saturated zone in the karst water system we analyzed the distribution range of karst water aquifers of xishan mountain the permeability of the stratum the boundary characteristics and the relationship between the interior and exterior system it was essential to clarify the interactions among the karst water systems of the mountain area surface water pore water in the caenozoic unconsolidated materials and the deep karst water under the basin this research shows that the study area can be divided into two subsystems 1 lancun spring and jinci spring and 2 xiye spring subsystem 1 includes the regional saturated zone the passage zone and the local saturated zone we demonstrated that lancun spring and jinci spring belong to the same regional karst water system subsystem 2 results from the perched groundwater formed by a local impermeable bed the results show that this type of integrated analysis is a useful method to extract hydrogeologic information and can be applied to a mountain area without much investigated data in particular where carbonate formations or layered permeable rock are the most important aquifers

the cascade of tidal energy from low to high modes on a continental slope abstractthe linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near critical continental slope a theoretical framework for low wavenumber energy transfer is derived from flat bottom vertical modes and evaluated with observations from the oregon continental slope to better understand the observations local tidal dynamics are modeled with a superposition of two idealized numerical simulations one forced by local surface tide velocities and the other by an obliquely incident internal tide generated at the mendocino escarpment 315 km southwest of the study site the simulations reproduce many aspects of the observed internal tide and verify the modal energy balances observed transfer of tidal energy into high mode internal tides is quantitatively consistent with observed turbulent kinetic energy tke dissipation locally generated and incident simulated internal tides are superposed with varying phase shifts to mimic the effects of the temporally

infiltration efficace dans le karst hellenique abstract for the calculation of the coefficient of effective infiltration into the greek karst representative karstic aquifer systems showing simple geological structure and clear boundaries were chosen from the observation of total discharge and precipitation falling on these systems the coefficient of effective percolation was calculated then by extrapolation the specific efficiency module specifique of the greek karst was calculated finally efforts were made for establishing empirical methods adapted properly for the calculation of the infiltration in the karstic areas

basin scale compressibility of the northern adriatic by the radioactive marker technique the paper presents a constitutive model for the one dimensional vertical compressibility mv of the northern adriatic sedimentary basin based on in situ deformation measurements by the radioactive marker technique gas reservoir compaction and expansion occurring during the field production life and after its abandonment have been measured in three deep boreholes of the northern adriatic by fsmt formation subsidence monitoring tool and cmi compaction monitoring instrument developed by schlumberger and western atlas respectively the compressibility values as obtained by relating the shortening of the distance between several pairs of adjacent markers to the pore pressure decline experienced by the productive levels during the monitored time interval are statistically processed to reduce the influence of operational and instrumental errors the method of moving weighted averages is used over clustered depth intervals the compressibility thus derived is related to the in situ vertical effective stre

the formation and fate of internal waves in the south china sea internal oceanic waves are subsurface gravity waves that can be enormous and travel thousands of kilometres before breaking but they are difficult to study here observations of such waves in the south china sea reveal their formation mechanism extreme turbulence relationship to the kuroshio current and energy budget internal waves are the underwater version of more familiar surface waves they can be enormous and travel thousands of kilometres before breaking the south china sea is known to be home to the largest internal waves in the world s oceans but their size generation mechanisms and role in the regional energy budget are unknown matthew alford and colleagues now present the results from the iwise observational campaign and reveal that internal waves more than 200 metres high break in the south china sea and create turbulence that is orders of magnitude larger than in the open ocean and that wave formation is influenced by the kuroshio current these results now allow for a complete energy budget of the south china sea and for a more accurate incorporation of internal waves into climate models internal gravity waves the subsurface analogue of the familiar surface gravity waves that break on beaches are ubiquitous in the ocean because of their strong vertical and horizontal currents and the turbulent mixing caused by their breaking they affect a panoply of ocean processes such as the supply of nutrients for photosynthesis1 sediment and pollutant transport2 and acoustic transmission3 they also pose hazards for man made structures in the ocean4 generated primarily by the wind and the tides internal waves can travel thousands of kilometres from their sources before breaking5 making it challenging to observe them and to include them in numerical climate models which are sensitive to their effects6 7 for over a decade studies8 9 10 11 have targeted the south china sea where the oceans most powerful known internal waves are generated in the luzon strait and steepen dramatically as they propagate west confusion has persisted regarding their mechanism of generation variability and energy budget however owing to the lack of in situ data from the luzon strait where extreme flow conditions make measurements difficult here we use new observations and numerical models to 1 show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena 2 reveal the existence of 200 metre high breaking internal waves in the region of generation that give rise to turbulence levels 10 000 times that in the open ocean 3 determine that the kuroshio western boundary current noticeably refracts the internal wave field emanating from the luzon strait and 4 demonstrate a factor of two agreement between modelled and observed energy fluxes which allows us to produce an observationally supported energy budget of the region together these findings give a cradle to grave picture of internal waves on a basin scale which will support further improvements of their representation in numerical climate predictions

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

from infiltration to recharge use of a parametric transfer function abstract the recharge of a water table aquifer involves transfer of the infiltration effective rainfall through the unsaturated zone in certain areas the depth at which the water table lies and the properties of the unsaturated zone can vary greatly and thus the determination as a function of time of the recharge actually arriving in the saturated aquifer can be rather difficult however we need to know this recharge in order to simulate the true behaviour of the aquifer in transient state in a regional digital model of the aquifer for the purpose of calibration or prediction the resolution of the exact flow equations in the unsaturated zone is possible but seems still to be far too complex for practical applications in this paper we first propose a methodology for the identification of the spatial variability of the infiltration transfer function using common climatic and piezometric data a parametrisation of these transfer functions using gamma distributions as basic functions is then suggested two practical examples make it possible to check the applicability of the procedure

sediment resuspension and mixing by resonantly generated internal solitary waves the observation of internal solitary waves isws propagating upstream along a strongly stratified bottom layer on the california shelf is reported an increased concentration of particulates in the water column accompanies the passage of these isw packets the estimated local richardson number in the bottom vicinity is around 1 4 and a vertical coefficient of eddy diffusivity of order 1022 m2 s21 is associated with the upstream propagating leading isw the leading isw gave rise to reversed flow in an 8 m layer above the bottom it is argued that the upstream propagating isws were generated by resonant flow over bottom topography internal waves generated in this way seem to be frequent in the record of a month long experiment model results suggest that the isws can carry up to 73 of such generated long wave energy the ocean conditions at the site are similar to those of other coastal sites which suggests that the phenomenon described here may be common

sediment resuspension mechanisms associated with internal waves in coastal waters 1 large amplitude vertically trapped internal waves can induce sizable velocities and trigger hydrodynamic instabilities in the bottom boundary layer thereby contributing to the resuspension of sediments and the maintenance of sediment concentration in the water column we discuss numerical simulations of several different situations in which the boundary layer in the wave footprint undergoes hydrodynamic instability with a resultant increase in the incidence of spatiotemporal structures that could facilitate sediment resuspension for the case of internal solitary waves we provide bounds in parameter space separating regions in which internal waves can be expected to efficiently resuspend sediment from those in which the boundary layer in the wave footprint is both laminar and stable a notable finding is that the onset of instability is a strong function of the background current the lagrangian transport of passive particles due to the instability is explored and some quantitative measures of the efficiency of the particle transport process are provided we subsequently discuss the evolution of the power spectra of the bottom shear stress with time and find that while the general characteristics of the instability are robust lowering either the reynolds number or the strength of the background current leads to an increase in the typical length scales associated with the mature instability finally we discuss instabilities during the internal wave generation process and alternative instability mechanisms when the bottom is not flat

global abyssal mixing inferred from lowered adcp shear and ctd strain profiles abstract internal wave wave interaction theories and observations support a parameterization for the turbulent dissipation rate e and eddy diffusivity k that depends on internal wave shear vz2 and strain z2 variances its latest incarnation is applied to about 3500 lowered adcp ctd profiles from the indian pacific north atlantic and southern oceans inferred diffusivities k are functions of latitude and depth ranging from 0 03 10 4 m2 s 1 within 2 of the equator to 0 4 0 5 10 4 m2 s 1 at 50 70 diffusivities k also increase with depth in tropical and subtropical waters diffusivities below 4500 m depth exhibit a peak of 0 7 10 4 m2 s 1 between 20 and 30 latitudes where semidiurnal parametric subharmonic instability is expected to be active turbulence is highly heterogeneous though the bulk of the vertically integrated dissipation e is contributed from the main pycnocline hotspots in e show some correlation with small scale bottom roughness and near bottom flow at sites where st

different origins of seafloor undulations in a submarine canyon system northern south china sea based on their seismic character and relative location abstract high resolution 2d and 3d seismic data are used to investigate the morphology internal architecture and origin of widespread seafloor undulations in the eastern area of a submarine canyon system northern south china sea the seafloor undulations reveal similar seafloor morphologies and three different types types a b and c can be classified based on their relative locations and internal seismic characters types a and b are observed in the canyon areas whereas type c occurs in the canyon heads seismic reflections within types a and c are continuous and have an upslope migrating trend while type b seafloor undulations are separated by listric faults our analysis reveals the origins of these three different types of seafloor undulations type a seafloor undulations are sediment waves formed by turbidity currents flowing through the submarine canyons gravity driven submarine creep resulted in the formation of type b seafloor undulations type c undulations are sediment waves generated by internal waves interacting with the continental slope our results provide information about the origin of widespread seafloor undulations in other submarine canyon systems it is also of great significance to future risk assessments as the study area now is one of the most active regions for hydrocarbon exploration in se asia

a frequency domain approach to groundwater recharge estimation in karst this paper presents an alternative method for determining the values of parameters of a groundwater recharge model the phreatic zone of a karst aquifer is considered as the linear and time invariant filter that transforms the input signal of groundwater recharge rates into the output signal of spring discharges similarities between transfer functions of total rainfall rates and transfer functions of groundwater recharge rates are the basis for developing the parametric periodogram depending on parameters of a groundwater recharge model the values of parameters are estimated by minimizing the differences between the parametric periodogram and a periodogram of spring discharges the approximate whittle log likelihood function is the criterion for determining the optimal values of the parameters by using this frequency domain approach groundwater balance calculations are avoided so the method can be applied on unexplored karst aquifers when groundwater balance cannot be achieved without extensive geologic and hydrogeologic investigations the results of the applications on two springs located in the dinaric karst area in croatia are discussed

poroelastic stressing and induced seismicity near the lacq gas field southwestern france o hundreds of shallow small to moderate earthquakes have occurred near the lacq deep gas field in southwestern france since 1969 these earthquakes are clearly separated from tectonic seismicity occurring in the pyrenees 25 km to the southwest the induced seismicity began when the reservoir pressure had declined by 30 mpa repeated levehng over the field shows localized subsidence reaching a maximum of 60 mm in 1989 segall 1989 suggested that poroelastic stressing associated with volumetric contraction of the reservoir rocks is responsible for induced seismicity associated with fluid extraction to test this model we compare the observed subsidence and hypocentral distributions with the predicted displacement and stress fields we find that the relationship between average reservoir pressure drop and subsidence is remarkably linear lending support to the linear poroelastic model displacements and stresses are computed based on a priori knowledge of the reservoir geometry materim properties and reservoir pressure changes the computed vertical displacements are found to be in excellent agreement with the subsidence observed from leveling stress perturbations accompanying gas extraction computed using the same parameters are found to be 0 2 mpa or less changes in coulomb failure stress are computed assuming that shp occurs on optimally oriented planes the predicted failure zones correlate very well with the spatial distribution of earthquakes if the perturbing stresses are small in comparison to the ambient regional deviatoric stresses and if the minimum regional compresslye stress axis is vertical accurate determination of focal mechanisms of the induced events would allow a more rigorous test of the poroelastic model and could lead to important inferences about the crustal stress state

structure propagation and mixing of energetic baroclinic tides in mamala bay oahu hawaii abstract large semidiurnal vertical displacements 100 m and strong baroclinic currents 0 5 m s 1 several times as large as barotropic currents dominate motions in mamala bay outside the mouth of pearl harbor hawaii during september 2002 the authors sought to characterize them with a 2 month mclane moored profiler deployment and a 4 day intensive survey with a towed ctd adcp and the research vessel r v revelle hydrographic sonar spatial maps and time series of turbulent dissipation rate diapycnal diffusivity k isopycnal displacement velocity u energy e and energy flux f are presented dissipation rate peaks in the lower 150 m during rising isopycnals and high strain and shows a factor of 50 spring neap modulation the largest k values in the western bay near a submarine ridge exceed 10 3 m2 s 1 the m2 phases of and u increase toward the west implying a westward phase velocity cp 1 m s 1 and horizontal wavelength 60 km consistent with theoretical mode 1 values these phase

flow separation and resuspension beneath shoaling nonlinear internal waves 1 laboratory observations are presented showing the structure and dynamics of the turbulent bottom boundary layer beneath nonlinear internal waves nliws of depression shoaling upon sloping topography the adverse pressure gradient beneath the shoaling waves causes the rear face to steepen flow separation to occur and wave induced near bottom vortices to suspend bed material the resuspension is directly attributed to the near bed viscous stress and to near bed patches of elevated positive reynolds stress generated by the vortical structures these results are consistent with published field observations of resuspension events beneath shoaling nliws elevated near bed viscous stresses are found throughout the domain at locations that are not correlated to the resuspension events near bed viscous stress is thus required for incipient sediment motion but is not necessarily a precursor for resuspension resuspension is dependent on the vertical velocity field associated with positive reynolds stress and is also found to occur where the mean wave averaged vertical velocity is directed away from the bed the results are interpreted by analogy to the eddy stress and turbulent bursting resuspension models developed for turbulent channel flows

evidence for enhanced mixing over rough topography in the abyssal ocean the overturning circulation of the ocean plays an important role in modulating the earth s climate but whereas the mechanisms for the vertical transport of water into the deep ocean deep water formation at high latitudes and horizontal transport in ocean currents have been largely identified it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise however measurements of the internal wave field the main source of energy for mixing and of turbulent dissipation rates have typically implied diffusivities across surfaces of equal density of only approximately 0 1 cm2 s 1 too small to account for the return flow here we report measurements of tracer dispersion and turbulent energy dissipation in the brazil basin that reveal diffusivities of 2 4 cm2 s 1 at a depth of 500 m above abyssal hills on the flank of the mid atlantic ridge and approximately 10 cm2 s 1 nearer the bottom this amount of mixing probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry may be large enough to close the buoyancy budget for the brazil basin and suggests a mechanism for closing the global overturning circulation

induced stresses due to fluid extraction from axisymmetric reservoirs earthquakes can be induced by fluid extraction as well as by fluid injection segall 1989 proposed that poroelastic stresses are responsible for inducing earthquakes associated with fluid extraction here i present methods for computing poroelastic stress changes due to fluid extraction for general axisymmetric reservoir geometries the results ofgeertsma 1973 for a thin disk reservoir with uniform pressure drop are recovered as a special case predicted surface subsidence agrees very well with measured leveling changes over the deep lacq gas field in southwestern france the induced stresses are finite if the reservoir pressure changes are continuous computed stress changes are on the order of several bars suggesting that the preexisting stress states in regions of extraction induced seismicity are very close to frictional instability prior to production

internal solitary waves in the coastal mixing and optics 1996 experiment multimodal structure and resuspension 1 observations of internal solitary waves isws and of their role in sediment resuspension during the coastal mixing and optics 1996 cmo 96 experiment are reported the largest resuspension events observed in the experiment can be related to retarded flow under the wave footprint two distinctly different periods of resuspension events could be distinguished based on the prevailing atmospheric conditions a calm period which we consider characteristic of nominal conditions and an energetic period during which two major storms occurred isws arrived at the mooring site from a variety of sources though a common intermodal dynamics seemed to occur repeatedly both mode 1 and mode 2 isws have been observed the present analysis of the month long portion of the cmo 96 data set constitutes the first reported observations insofar as we are aware of mode 2 waves on the continental shelf both mode 1 and mode 2 isws were found to stimulate resuspension the mode 2 waves seem to be generated locally by resonant or topographic interactions with mode 1 isws internal wave fields of the type described here are expected to exist in a variety of other shallow seas as well

role of internal waves in the generation of nepheloid layers on the northwestern alboran slope implications for continental margin shaping 1 the role of internal waves in the sediment dynamics of the northwestern alboran continental slope was investigated in a selected area around the guadiaro submarine canyon nepheloid layer distribution was identified using closely spaced ctd transmissometer profiles collected during two hydrographic surveys a well defined pattern of suspended sediment distribution consisting of surface intermediate and near bottom nepheloid layers was found intermediate and bottom nepheloid layers were always observed within the canyon and on the adjacent continental slope spanning mainly from 200 to 500 m depth in addition a current meter with a turbidimeter was deployed in the lower section of the guadiaro canyon at 600 m depth 25 meters above the seafloor time series analysis indicated that the currents temperature and turbidity within the canyon fluctuate mainly at semidiurnal tidal frequencies suggesting the presence of semidiurnal internal tides affecting the near bottom suspended sediment concentration along the canyon axis high resolution bathymetry from the study area was used to evaluate the internal wave reflection conditions at semidiurnal tidal frequency for the entire continental slope region critical slope conditions were reached on the upper continental slope and along the canyon axis coinciding with the region in which nepheloid layers were observed this region also coincides with a zone of erosion on the upper continental slope of the study area previously identified by hernandez molina 1993 these results indicate that the generation of intermediate and bottom nepheloid layers as well as the erosion and shaping of the northwestern alboran continental slope may result from the interaction of internal waves and the seafloor morphology

a new approach in assessing recharge of highly karstified terrains montenegro case studies the recharge of a karst aquifer in terms of its quantity and spatial distribution depends on various natural factors such as climate topography vegetation soil and geology selection of an adequate method for assessing recharge in karst is often a matter of dispute multi parameter methods using geographical information systems tools have recently been successfully developed and applied in karstic terrains of spain and lebanon specific local conditions such as highly karstified terrains could additionally complicate such an assessment the montenegro karstified terrains in the southern part of the external dinarides are characterized by a very high precipitation rate irregular seasonal distribution and absence of surface waters extremely high infiltration capacity of karst considering such conditions an attempt to apply existing knowledge and experiences to the development of an appropriate multi parameter method for assessing spatial distribution of autogenous recharge has been made the karstlop method has been developed applied and calibrated at catchments of several large karst springs of montenegro obtained results in tested catchment areas confirm that with some further improvements the karstlop method could be a useful tool to support research of karstic aquifers in similar highly karstified terrains

interrelation between induced seismic instabilities and complex geological structure from 1982 to 1989 more than 520 local seismic events were recorded by a permanent network of 9 telemetered stations over an active gas field lacq france the geological data of 46 boreholes coupled to several tens of kilometers of seismic profiles concentrated in a small volume of 15 15 10 km3 allow the development of a very precise velocity structure exhibiting a dome geometry limited by faulted strips the discretized velocity model includes almost 20000 blocks with 500 m 500 m 250 m minimum dimensions a relocation technique using this a priori detailed 3d velocity model allows precise locations of induced earthquakes 351 relocated hypocenters show that of the seismic activity concentrated on geometrical discontinuities of the local dome structure the locations of seismic events are correlated with geomechanical layers of the structure spatial and temporal migration of seismic ruptures mimics the different permeability rings of the reservoir which are progressively depleted by gas extraction most of these events are at present confined close to major thrust planes which limit the dome structure laterally and in depth onto preexisting faults in the basement below the gas field the occurence of these deep clusters demonstrates that fluid manipulation in the sedimentary covers can activate preexisting basement faults this result changes previous assessments of local seismic risk and provides new insights into fault mechanisms in areas with complex geological structure

energy flux and dissipation in luzon strait two tales of two ridges abstractinternal tide generation propagation and dissipation are investigated in luzon strait a system of two quasi parallel ridges situated between taiwan and the philippines two profiling moorings deployed for about 20 days and a set of nineteen 36 h lowered adcp ctd time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals measurements were concentrated on a northern line where the ridge spacing was approximately equal to the mode 1 wavelength for semidiurnal motions and a southern line where the spacing was approximately two thirds that the authors contrast the two sites to emphasize the potential importance of resonance between generation sites throughout luzon strait baroclinic energy energy fluxes and turbulent dissipation were some of the strongest ever measured peak to peak baroclinic velocity and vertical displacements often exceeded 2 m s 1 and 300 m respectively energy fluxes exceeding 60 kw m 1 were measured at spring tide at the wester

contour current driven continental slope situated sandwaves with effects from secondary current processes on the barents sea margin offshore norway abstract seabed data acquired from the southern barents sea continental margin offshore norway reveal detailed morphology of large sandwave fields multibeam echosounder bathymetry and backscatter shallow seismic sediment samples and seabed video data collected by the mareano program have been used to describe and interpret the morphology distribution and transport of the sandwaves the bedforms lie on a slope dominated by relict glacial forms and muddy sandy gravelly sediments sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later the contour parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic norwegian atlantic current nwac demonstrate that the nnw flowing oceanographic circulation is the primary driving current the fields coincide with the depth range at which a transition between warm saline and underlying cooler less saline waters fluctuate across the seabed statistically rigorous measurements of height width and various parameters of slope and symmetry confirm a tendency to downstream nnw sandwave migration but with significant exceptions anomalous bedform symmetry domains within the fields are tuned to meso scale topography along relict glacial debris flow chutes indicating current focusing upstream and upper slope derived winnowed sand transport eroded from the glacial sediments is the supposed source sandwave flank slope values are comparable to the regional slope such that the gravitational vector would have a cumulative downslope migration affect unless balanced by upslope drivers perpendicular cross cutting of stoss face 3 d ripples by linear 2 d ripples in the sandwave troughs and lee faces is evidence for non synchronous episodic current variations though deep ekman transport and internal wave action are unproven here these could explain chute related tuning of bedform symmetry through funneling in the debris flow chutes and favor sand recycling thus contributing to long term maintenance of the sandwave field

recharge and aquifer response northern guam lens aquifer guam mariana islands abstract the northern guam lens aquifer is an island karst aquifer in uplifted young highly conductive limestone calculations of recharge based on differences between daily rainfall and daily pan evaporation suggest that the maximum annual mass of water delivered to the freshwater lens is about 67 of mean annual rainfall hydrographs of daily well level responses plotted against daily rainfall indicate that the rate at which water is delivered to the lens is a function of rainfall intensity and the relative saturation of the vadose zone together these variables determine the degree to which stormwater is shunted into fast flow through preferred pathways that bypass the bedrock matrix rather than percolating slowly through the bedrock matrix data from the 40 year interval from 1956 to 1995 show that some 17 of rainfall on northern guam arrives in small amounts 5 0 cm day which tend to promote fast flow at the expense of percolation rapid recovery of the water table from rapid recharge suggests that the lens either takes such recharge into storage very rapidly discharges it rapidly without taking it into storage or some combination of both significant vadose buffering of recharge to the lens is indicated by the fact that simulations assuming that the recharge from precipitation received in any given month is transmitted to the lens during the same month consistently over predict observed peak mean monthly water levels and under predict the minima

estimating infiltration recharge using a response function model abstract rainfall infiltration influences both the quantity and quality of groundwater systems the knowledge of the process of infiltration recharge is of great importance to the management of groundwater systems and the hydraulically connected streams in this study a response function model is developed to estimate soil water flux at the water table or the process of infiltration recharge from rainfall and evaporation data the gamma probability density function is modified to represent the travel time distribution of infiltrating water by rainfall events the travel time distribution is used to determine the recharge process according to the effective infiltration of a rainfall event the effective infiltration is the amount of soil water pushed down into groundwater by infiltrating water of a rainfall event and is evaluated based on the vadose zone soil water balance superposition is employed to compute the recharge rate produced by a sequence of rainfall events estimations of soil water flux at different groundwater depths are compared with lysimetric observations in the field good agreements between the estimated and observed results confirm the reliability of the response function model for predicting infiltration recharge processes

nonlinear kernel functions for karst aquifers this paper presents a form of kernel function for karst aquifers derived from the time invariant and non anticipatory volterra series the shape of the kernel function depends on the current value of an index of antecedent recharge that is considered as an indicator of groundwater levels and vadose zone saturation the proposed nonlinear form preserves specific characteristics of instantaneous unit hydrographs by using analogies with the conceptual model of nonlinear reservoir it is shown that the second component of the kernel function characterizes the prevailing type of groundwater flow if the second component is positive the free surface flow is dominant whereas the negative value indicates that the flow under pressure prevails groundwater recharge rates are calculated by using a groundwater recharge model based on the palmer s soil moisture balance method the values of parameters of the groundwater recharge model are estimated by the spectral method which is modified to avoid the assumption about exponential forms of autocorrelation functions of input and output time series this paper analyzes also the practical applicability of nonlinear kernels for the preliminary characterization of karst aquifers and the karst springs discharge modeling the results of applications on the springs zones of the rivers krka and krcic are in accordance with previous assumptions that the main krka spring is an ascending karst spring which aquifer is situated deeply inside the karst underground whereas the main krcic spring function as a descending karst spring

variability of internal tides and near inertial waves on the continental slope of the northwestern south china sea structure and variability of internal tides it and near inertial waves niw on the continental slope of the northwestern south china sea were investigated based on 9 month moored current observations from autumn to early summer in 2008 and 2009 the diurnal it kinetic energy dominant over that of semidiurnal tides is found to exhibit apparent seasonal variability strongest in summer and weakest in winter whereas the semidiurnal variance remained nearly uniform throughout the observation period moreover the diurnal it were more coherent i e phase locked to the astronomical forcing than the semidiurnal constituents coherent diurnal variance accounts for about 40 of diurnal motions but semidiurnal tides contain a much smaller fraction 10 of coherent motions further analysis demonstrates that the diurnal it are dominated by the first mode whereas the semidiurnal tides show a variable multimodal structure the second mode is dominant in summer and comparable to the first mode in spring and autumn but the first mode predominates in winter multimodal semidiurnal it are more influenced by varying stratification structures and background currents and thus exhibit highly incoherent and intermittent behavior which may wash out seasonal variability during their long propagation from the generation source the observed niw are seasonally independent and comparable to the semidiurnal motions during the passage of typhoon hagupit however the niw became the most energetic component of the inertia gravity waveband motions niw energy and shear were significantly enhanced and exceeded tidal counterparts by a factor of 2 to 3 in the upper layer

statistical analyses and modeling approaches to hydrodynamic characteristics in alluvial aquifer this study is aimed at quantifying the difference in aquifer s response to recharge between some different locations in a fan aquifer and a delta aquifer for a preliminary study of revealing mechanisms of water transport in alluvial aquifer the aquifer s response to recharge is statistically quantified with the two viewpoints 1 timing and volume of recharge and 2 time length of aquifer s holding water for the first point a statistical model that links precipitation and groundwater level is introduced and its parameters are identified using correlation analysis our results show that the recharge rate at the toe is higher than that at the apex and at the delta for the second point the concept of memory effect of aquifer is adopted and quantified using the autocorrelation and spectral analyses our results show that the memory effect is longer at the toe of fan than at the apex and thus a temporary increase of water level has about five times as long term influence on subsequent water levels at the toe of the fan as at the apex this study demonstrates that the statistical analyses and modeling of hydrological data are useful for characterizing aquifer s hydrodynamics copyright 2012 john wiley sons ltd

estimating groundwater recharge for an arid karst system using a combined approach of time lapse camera monitoring and water balance modelling groundwater is the principal water resource in semi arid and arid environments therefore quantitative estimates of its replenishment rate are important for managing groundwater systems in dry regions karst outcrops often show enhanced recharge rates compared with other surface and sub surface conditions areas with exposed karst features like sinkholes or open shafts allow point recharge even from single rainfall events using the example of the as sulb plateau in saudi arabia this study introduces a cost effective and robust method for recharge monitoring and modelling in karst outcrops the measurement of discharge of a representative small catchment 4 0 middle dot 104 m2 into a sinkhole and hence the direct recharge into the aquifer was carried out with a time lapse camera during the monitoring period of two rainy seasons autumn 2012 to spring 2014 four recharge events were recorded afterwards recharge data as well as proxy data about the drying of the sediment cover are used to set up a conceptual water balance model the model was run for 17 years 1971 to 1986 and 2012 to 2014 simulation results show highly variable seasonal recharge precipitation ratios between 0 and 0 27 in addition to the amount of seasonal precipitation this ratio is influenced by the interannual distribution of rainfall events overall an average annual groundwater recharge for the doline sinkhole catchment on as sulb plateau of 5 1 mm has estimated for the simulation period copyright c 2015 john wiley sons ltd c 2016 john wiley sons inc

analysis of rainfall recharge relationships abstract understanding the recharge process and its relationship with rainfall is of critical importance to the management of groundwater systems and enormous effort has been made to estimate the amount and process of recharge by infiltration using precipitation data in the present research in situ lysimeter experiments and numerical simulations were used to study the relationships between rainfall and recharge by infiltration at different groundwater depths four lysimeters 1 5 3 4 5 and 5 m deep were installed in the field to measure the infiltration recharge rates under conditions of fixed water tables at the bottoms of the soil columns annual infiltration recharges at different groundwater depths were obtained through the lysimeter measurements the effect of rainfall pattern and annual rainfall distribution on infiltration recharge was simulated at various groundwater depths using a numerical model based on soil water dynamics and comparisons of the simulated and observed recharges showed very good agreement relationships between rainfall and infiltration recharge at different groundwater depths were investigated using the lysimeter measurements and computer simulations groundwater systems were classified into three categories i e shallow water table intermediate water table and deep water table based on the relationship between rainfall and infiltration recharge at different groundwater depths

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th

a review of internal solitary wave dynamics in the northern south china sea abstract the current research into internal solitary waves isws and the related dynamic processes in the northern south china sea scs are reviewed in this paper this unique wave phenomenon did not draw much interest until about one decade ago and is now one of the hot topics in the field of wave dynamics three methods of investigation are summarized in the paper namely remote sensing images in situ measurements and numerical simulations previous works have primarily been based on one or two of these methods and have provided great insights into such wave phenomena the lifetime of an isw in the northern scs from its origin in the luzon strait ls through to its formation and evolution in the deep basin and its transformation near the shelf break up until its dissipation on the continental shelf is summarized with the illustration of different investigation approaches various factors that can affect the wave generation processes are summed up as well such factors as are barotropic tides in the ls kuroshio intrusion temporal and spatial variation of stratification and the modulation of the western ridge in the ls can significantly alter the wave fields and are extensively discussed

propagation of low mode internal waves through the ocean abstract the baroclinic tides play a significant role in the energy budget of the abyssal ocean although the basic principles of generation and propagation are known a clear understanding of these phenomena in the complex ocean environment is only now emerging to advance this effort a ray model is developed that quantifies the effects of spatially variable topography stratification and planetary vorticity on the horizontal propagation of internal gravity modes the objective is to identify baroclinic shoals where wave energy is spatially concentrated and enhanced dissipation might be expected the model is then extended to investigate the propagation of internal waves through a barotropic mesoscale current field the refraction of tidally generated internal waves at the hawaiian ridge is examined using an ensemble of mesoscale background realizations derived from weekly ocean topography experiment topex poseidon altimetric measurements the path of mode 1 is only slightly affected by typical cur

temporal scaling of groundwater discharge in dual and multicontinuum catchment models this paper presents a multicontinuum approach to model fractal temporal scaling of catchment response in hydrological systems the temporal scaling of discharge is quantified in frequency domain by the transfer function h x which is defined as the ratio between the spectra of catchment response and recharge time series the transfer function may scale with frequency x as h x x2b while the classical linear and dupuit models predict exponents of b52 and b51 observations indicate scalings with noninteger exponents b such behaviors have been described by multifractal models which however often lack a relation to the medium characteristics we revisit and extend the classical linear dupuit aquifer models and discuss their physical meanings in the light of the resulting aquifer dynamics on the basis of these classical models we derive a multicontinuum approach that provides physical recharge models which are able to explain fractal behaviors with exponents 1 2 b 2 furthermore this approach allows to link the fractal dynamics of the discharge process to the physical aquifer characteristics as reflected in the distribution of storage time scales we systematically analyze the catchment responses in the proposed multicontinuum models and identify and quantify the time scales which characterize the dynamics of the catchment response to recharge

the role of internal waves in the late quaternary evolution of the israeli continental slope abstract internal waves are widely present in world s oceans propagating in stratified ocean layers such as the seasonal pycnocline at continental shelves and slopes breaking of internal waves may create turbulence of sufficient energy to erode and transport sediments in this study we investigate the late pleistocene to recent impact of internal waves on the morphology of the israeli mediterranean continental slope based on mooring data we show that the internal wave spectrum on the upper slope contains significant energy at near inertial and semidiurnal tidal frequencies sediment subbottom profiler data show two fields of nearly contour parallel sediment waves located in water depths of 80 m 130 m and 190 m 350 m respectively a zone of flat seafloor morphology and remarkably constant slope inclination of 1 0 1 2 separates both sediment wave fields the entire stretch of seafloor between 80 m and 350 m corresponds to depths of major ocean density stratification supporting the propagation of internal waves in addition this area is critically inclined with respect to semidiurnal internal tides and supercritically inclined with respect to near inertial waves two scenarios previously related to internal wave breaking we propose that breaking internal waves control the inclination of the israeli continental slope and contribute to sediment starvation within the zone of flat seafloor morphology the formation of sediment waves is attributed to high frequency trailing internal waves of similar wavelengths as sediment waves observed within a seismic image of the water column we correlate subbottom profiler data to a radiocarbon dated sediment core no sediment waves formed from 16 cal ka 8 cal ka indicating that the seafloor impact of internal waves ceased during a time of rapid sea level rise and fresh water input in the eastern mediterranean realm the end of this period coincides with the formation of sapropel s1

simulated effect of vadose infiltration on water levels in the northern guam lens aquifer regional scale hydrology of the fresh water lens in the northern guam lens aquifer has been simulated in the past using a finite element sharp interface computer model swig2d systematic differences exist between observed and computed water levels computed seasonal peak water levels are higher and the computed seasonal lows are lower than the respective observed levels it is hypothesized that vadose storage must store a substantial amount of water during the wet season and release it gradually into the lens during the dry season flow through the vadose zone was simulated with a one dimensional finite element unsaturated flow program unsat1d in which the van genuchten model is used to characterize unsaturated diffuse flow through the matrix of the vadose zone an additional parameter sink was added to the van genuchten set to account for rapid infiltration down open pathways fractures associated with the closed depressions of the karst terrain a global optimization technique shuffled complex evolution or sce ua method was used to obtain the parameters that minimized the difference between simulated and observed water levels simulations incorporating the van genuchten model were accomplished by combining the two programs unsat1d and swig2d into a single program the sum of squared errors sse between computed and observed water levels in four observation wells was minimized using sce ua reducing the arithmetically averaged sse of the four wells by 30 compared with the sse obtained when the vadose zone was not modeled these results suggest that vadose storage is significant on the other hand the fact that the best fit obtained with an optimum parameter set was able to reduce the sse by no more than 30 suggests that additional phenomena have yet to be accounted for to more fully explain differences between simulated and observed well water levels

footprints of obliquely incident internal solitary waves and internal tides near the shelf break in the northern south china sea a mooring system and two sites of bottom currents were deployed over the slope and near the shelf break on the propagating paths of internal solitary waves isws west off dongsha atoll in the northern south china sea data indicated that energetic isws obliquely shoaled onto the shelf west off dongsha atoll in an approximately 290 degrees direction causing strong reversing currents some exceeding 80 cm s near the bottom two types of sandwaves and short scour channels are discernible on the seafloor near the shelf break which have reasonable correlations with the obliquely incident isws and internal tides type 1 sandwaves featured by isws at the depths of 130 150 m have flat crests interacting with the isobaths at an angle of nearly 45 degrees which slightly incline and migrate upslope type 2 sandwaves are associated with internal tides which have crests parallel to the isobaths and distinctly incline and migrate downslope short channels are parallel to the depth contours and truncate the strata which could be formed and maintained by along slope currents that are probably produced by the obliquely isws on a large gradient gamma 0 8 degrees the isws can move coarse grains or suspend fine grains but do not change the long term trend of sediment transport on the seabed with larger gradients gamma c 1 which is dominated by internal tides these features are likely widespread near the shelf break in the northern south china sea and other seas but are limited on mild slopes where isws do not break

quantification of temporal distribution of recharge in karst systems from spring hydrographs the estimation of the temporal distribution of recharge in karst aquifers is a challenge due to large heterogeneities in geometric and hydraulic parameters of the vadose and phreatic zone this article provides a time continuous approach for the estimation of inflow into the conduit system of a karst aquifer which consists of the sum of direct recharge and flow from the fissured matrix blocks into the conduit system the approach employs the first time derivative of the spring hydrograph and the recession coefficient of the conduit system for the determination of this function the first time derivative of the hydrograph describes the rate of change in spring discharge it reflects the ratio of inflow to and outflow from the conduit system the recession coefficient depends on the hydraulic diffusivity which controls the velocity of the signal transmission through the system as shown in parameter studies with a simplified serial two reservoir model direct recharge into the conduit system clearly dominates the early hydrograph response during recharge events even if the fraction of direct recharge represents just a few percent of total recharge this behaviour is caused by a large contrast in recession coefficients between conduit system and fissured matrix blocks the direct recharge component can therefore be separated from the estimated total inflow into the conduit system estimation of inflow into the conduit system of the gallusquelle spring swabian alb germany after a storm event yields similar results as those obtained from parameter studies the separation of the direct recharge component is in agreement with information from an independent isotope study the methodology has been further applied to a recharge event initiated by snowmelt as a result of daily variations of the air temperature a clearly diurnal cycle of inflow into the conduit system is estimated that is not easily recognizable from the spring hydrograph the applicability of the proposed methodology requires knowledge about the magnitude of the recession coefficient of the conduit system the characteristics of the conduit system become also apparent in the rapid transport of tracers the recession coefficient of the conduit system can for example directly be estimated from the reciprocal of the mean tracer travel time however for this type of analysis only tracer experiments covering the extent of the catchment should be taken into account for the gallusquelle catchment the recession coefficient obtained from the tracer experiment corresponds to that obtained from hydrograph recession analysis the estimated inflow into the conduit system and interpretation of temporal distribution of recharge is therefore based on a plausible and physically based parameter

alongshore currents over variable beach topography the nonlinear dynamics of unstable alongshore currents in the nearshore surf zone over variable barred beach topography are studied using numerical experiments these experiments extend the recent studies of allen et al 1996 and slinn et al 1998 which utilized alongshore uniform beach topographies by including sinusoidal alongshore variation to shore parallel sandbars the model involves finite difference solutions to the nonlinear shallow water equations for forced dissipative initial value problems and employs periodic boundary conditions in the alongshore direction effects of dissipation are modeled by linear bottom friction forcing for the alongshore currents is provided by gradients in the radiation stress which are specified using linear theory and the dissipation function for breaking waves formulated by thornton and guza 1983 distinct flows develop depending on the amplitude and wavelength of the topographic variability and the dimensionless parameter q the ratio of an advective to a frictional timescale for q greater than a critical value qc the flows are linearly stable for q qc q 0 the flow can be unstable for small values of q the effect of increasing is to stabilize or regularize the flows and to cause the mean flow to approximately follow contours of constant depth equilibrated shear waves develop that propagate along the mean current path at phase speeds and wavelengths that are close to predictions for the most unstable mode from linear theory applied to alongshore averaged conditions at intermediate values of q unsteady vortices form and exhibit nonlinear interactions as they propagate along the mean current path occasionally merging pairing or being shed seaward of the sandbar eddies preferentially form in the mean current when approaching alongshore troughs of the sandbar and break free from the mean current when approaching alongshore crests of the sandbar at the largest values of q examined the resulting flow fields resemble a turbulent shear flow and are less strongly influenced by the alongshore variability in topography as the amplitude of the alongshore topographic variability increases alongshore wavenumber frequency spectra of the across shore velocity show a corresponding increase in energy at both higher alongshore wavenumbers and over a broader frequency range with significant energy at wavenumbers of topographic variability and harmonics across shore fluxes of mass and momentum generally increase with increasing topographic amplitude and increasing q time and space lagged correlations of the across shore velocity show that correlation length scales decrease as topographic perturbation amplitudes increase terms from the vorticity equation show that the alongshore variation of the radiation stresses and the value of q are of importance to the flow behavior hybrid experiments separating effects of spatially variable forcing and the dynamic influence of topography on time averaged currents show that the effects are generally comparable with the relative importance of each effect a function of q the results show that topographic variability has a significant influence on nearshore circulation

evidence of short internal waves trailing strong internal solitary waves in the northern south china sea from synthetic aperture radar observations abstract sea surface signatures of short internal waves trailing strong internal solitary waves isws have been detected on several synthetic aperture radar sar images acquired by the advanced synthetic aperture radar asar onboard the european envisat satellite over the northern south china sea scs such configurations were found recently by vlasenko et al 2010 in numerical simulations carried out with the mit general circulation model mitgcm they showed that the short internal waves which have wavelengths of 1 5 km and amplitudes of 20 m ride on second mode isws the existence of these short internal waves which follow a first mode isw can be explained in terms of the taylor goldstein equation that includes a shear in the background current associated with a second mode isw the simulations predict that the short internal waves occur in two distinct areas one close to the luzon strait ls and the other further west in the first area they are generated by the disintegration of a baroclinic bore which is generated by the interaction of the tidal current with the steep two ridged topography in the ls in the second area they are generated when the faster first mode isw overtakes the second mode isw of the previous tidal cycle we have screened the asar archive of the european space agency esa and found many sar images acquired over the northern scs showing sea surface signatures of such short internal waves trailing a much longer first mode strong isw the detailed analysis of six of these sar images shows good correlation between modeled and observed internal wave fields

direct breaking of the internal tide near topography kaena ridge hawaii abstract barotropic to baroclinic conversion and attendant phenomena were recently examined at the kaena ridge as an aspect of the hawaii ocean mixing experiment two distinct mixing processes appear to be at work in the waters above the 1100 m deep ridge crest at middepths above 400 m mixing events resemble their open ocean counterparts there is no apparent modulation of mixing rates with the fortnightly cycle and they are well modeled by standard open ocean parameterizations nearer to the topography there is quasi deterministic breaking associated with each baroclinic crest passage large amplitude small scale internal waves are triggered by tidal forcing consistent with lee wave formation at the ridge break these waves have vertical wavelengths on the order of 400 m during spring tides the waves are nonlinear and exhibit convective instabilities on their leading edge dissipation rates exceed those predicted by the open ocean parameterizations by up to a factor of 100 with the disparity in

temporal and spatial scaling of hydraulic response to recharge in fractured aquifers insights from a frequency domain analysis quantification of the recharge in fractured aquifers is particularly challenging because of the multiscale heterogeneity and the range of temporal scales involved here we investigate the hydraulic response to recharge of a fractured aquifer using a frequency domain approach transfer functions are calculated in a range of temporal scales from 1 day up to a few years for a fractured crystalline rock aquifer located in ploemeur s brittany france using recharge and groundwater level fluctuations as input and output respectively the spatial variability of the response to recharge characteristic response time amplitude temporal scaling is analyzed for 10 wells sampling the different compartments of the aquifer some of the transfer functions follow the linear reservoir model behavior on the contrary others display a temporal scaling at high frequency that cannot be represented by classic models large scale hydraulic parameters estimated from the low frequency response are compared with those estimated from hydraulic tests at different scales the variability of transmissivity and storage coefficient tends to decrease with scale and the average estimates converge toward the highest values at large scale the small scale variability of diffusivities which implies the existence of a range of characteristic temporal scales associated with different pathways is suggested to be at the origin of the unconventional temporal scaling of the hydraulic response to recharge at high frequency

source and propagation of internal solitary waves in the northeastern south china sea 1 large amplitude internal solitary waves isws observed near dongsha island in the south china sea originate in tide topography interactions at luzon strait their arrival times at two moorings s7 at 117 17 e 21 37 n and y at 117 13 2 e 21 2 8 n are investigated with respect to model predicted barotropic tidal currents over lan yu ridge at luzon strait each isw packet can be associated with a westward tidal current peak the time lags between the isws and the barotropic tidal currents are 57 6 0 9 hours at s7 and 55 1 1 0 hours at y consistent with the mode one internal waves propagating nondispersively through the region s bathymetry and climatological stratification larger isws usually arrive earlier than smaller ones consistent with the theoretical relation between nonlinear wave speed and wave amplitude the observation that the isws are associated with westward tidal currents with without the presence of earlier eastward tidal currents suggests that they are generated by nonlinear steepening of internal tides rather than by the lee wave mechanism an idealized nonlinearization distance over which the isws are generated in internal tide troughs is estimated to be 260 40 km from luzon strait

temporal variability of karst aquifer response time established by the sliding windows cross correlation method summary we study the temporal variability of water transfer through the infiltration zone of a karst aquifer by estimating the impulse response of the system using cross correlogram analyses between rainfall and piezometric level time series we apply a sliding window cross correlation method which calculates cross correlograms on partially superposed short time series windows we apply this method for rainfall and piezometric level time series at six boreholes in a fractured karstic aquifer located in burgundy france based on cross correlogram functions we obtain a time series of response time at most of the boreholes the cross correlation functions change over time and the response times vary seasonally being shorter during the summer this unusual structure can be partly explained by the seasonal variability in rainfall intensity which is higher during the summer may september inducing the seasonal behaviour of the epikarst during the summer when rainfall intensity is higher the epikarst is more easily and quickly saturated this induces an increase in lateral water transfer within the epikarst and an increase in concentrated fast flows we also show that the response time seems to tend towards a limit which represents the maximum saturation of the epikarst