effects of groundwater level on seismic response of soil foundation systems abstracta set of dynamic centrifuge experiments was performed to assess the effect of the depth of the groundwater table on the seismic site response and kinematic interaction of a foundation on un

relations between thrust belt evolution grain scale deformation and metamorphic processes cape smith belt northern canada abstract an important step towards understanding how continental thrust belts evolve is to study the relationship between the map scale structures and the associated grain scale deformation mechanisms and metamorphic processes this relationship is examined in the early proterozoic cape smith thrust belt in the context of the belt s p t t history and fluid rock interactions overprinting deformation metamorphism relationships allow the thrust belt s evolution to be described in terms of four events 1 1 piggyback thrusting above a basal decollement localized at the basement cover contact 2 2 greenschist to amphibolite grade metamorphism and development of a ductile basal shear zone 3 3 re imbrication out of sequence faulting of the internal zone at pre to syn thermal peak conditions 4 4 post thermal peak out of sequence thrusting and retrograde metamorphism out of sequence thrusting was accommodated by the development of ductile shear zones in general relatively broad ductile shear zones developed adjacent to thrusts during prograde metamorphism while relatively narrow shear zones developed adjacent to thrusts during retrograde metamorphism the width of the shear zones was controlled by factors such as the competition between softening and hardening processes prograde shear zones and the extent of fluid influx retrograde shear zones four processes were primarily responsible for accomplishing penetrative deformation and accommodating thrust faulting during the belt s history 1 1 partitioning of strain into pre existing weak zones or into relatively weak layers in a compositionally stratified sequence 2 2 growth and or rotation of metamorphic products into orientations of maximum resolved shear stress 3 3 transitions in dominant deformation mechanism from brittle or semi brittle to crystal plastic 4 4 retrograde metamorphism involving fluid influx and hydration reactions producing weaker products than reactants

in situ estimates of net sediment flux per swash reply to discussion by te baldock of measurement of wave by wave bed levels in the swash zone abstract this paper replies to te baldock s discussion coastal eng 56 2009 380 381 of measurement of wave by wave bed levels in the swash zone by turner et al coastal eng 55 2008 1237 1242 we address and extend the comparison and discussion of ultrasonic bed level sensors and buried pressure transducers to obtain estimates of the beach face elevation within the swash zone we demonstrate the use of the former method to obtain many and continuous every time the beach face is exposed in situ estimates of net sediment flux per swash

the role of bore collapse and local shear stresses on the spatial distribution of sediment load in the uprush of an intermediate state beach abstract spatial variations in sediment load in the swash uprush and textural properties of sediment in transport were evaluated to investigate the mechanisms responsible for sediment transport during wave uprush four streamer traps were deployed at 2 0 m intervals across the swash zone of a sheltered microtidal sandy beach at port beach western australia over a 4 day period during these trapping experiments offshore significant wave heights were 0 3 0 5 m and wave periods were about 10 s the average width of the uprush zone was 6 9 m and the average uprush duration was 5 9 s cross shore distributions of sediment load for 70 uprush events reveal a maximum in sediment load landward of the base of the swash at about 20 of swash width during single events and a maximum closer to mid swash at about 40 of swash width during multiple events characterized by swash interactions settling velocity distributions of trap samples during individual uprush events are similar to distributions found on the beach surface with the lowest settling velocities finest sediments near the base of the swash zone and maximum settling velocities coarsest sediments around the mid swash position it was found that sediment transport during wave uprush occurs through two distinct mechanisms 1 sediment entrainment during bore collapse seaward of the base of the swash zone and subsequent advection of this bore entrained sediment up the beach by wave uprush and 2 in situ sediment entrainment and transport induced by local shear stresses during wave uprush both mechanisms are considered important but the first mechanism is considered most significant during the early stages of wave uprush when sediment is transported mainly in suspension while the second mechanism is likely to dominate the mid to later stages of wave uprush when sediment is transported mainly by sheet flow the relative importance of the two mechanisms will vary between different beaches with the morphodynamic state of the beach reflective versus dissipative expected to play a major role

numerical modelling of tide induced beach water table fluctuations field studies have shown that the elevation of the beach groundwater table varies with the tide and such variations affect significantly beach erosion or accretion in this paper we present a bem boundary element method model for simulating the tidal fluctuation of the beach groundwater table the model solves the two dimensional flow equation subject to free and moving boundary conditions including the seepage dynamics at the beach face the simulated seepage faces were found to agree with the predictions of a simple model turner 1993 the advantage of the present model is however that it can be used with little modification to simulate more complicated cases e g surface recharge from rainfall and drainage in the aquifer may be included the latter is related to beach dewatering technique the model also simulated well the field data of nielsen 1990 in particular the model replicated three distinct features of local water table fluctuations steep rising phase versus flat falling phase amplitude attenuation and phase lagging

strain softening induced ductile flow in the sarv thrust sheet scandinavian caledonides abstract the external zone of the scandinavian caledonides is characterized by thrust sheets composed of sedimentary rocks derived from the continent baltica the sarv thrust sheet is unique amongst them because the 4 5 6 km thick flat lying tossasfjallet group clastics were intruded by a sub vertical tholeiitic dike swarm prior to thrusting the sarv thrust sheet is a large horse 100 km long and 80 km wide with a classical ramp flat geometry the original intrusive relationships of the dikes are preserved throughout most of the thrust sheet and deformation is concentrated at the base in a mylonite zone several tens of meters thick in this zone meter thick dikes rotate into parallelism with the basal thrust and concordant mylonites of both lithologies are intercalated on a centimeter to millimeter scale the overall rigid block geometry of the sarv thrust sheet and the intense strain gradient recorded by the rotation of the dike swarm and the concurrent development of mylonites in the thrust zone suggest that thrust emplacement took place by ductile yield and on going pseudoplastic flow continual strain softening localized ductile flow in this zone by means of grain size reduction reaction enhanced ductility and grain boundary sliding processes inferred from the microstructures

swash zone moisture dynamics and unsaturated infiltration in two sandy beach aquifers the intertidal zone of coastal aquifers is a dynamic region of mixing between saline surface water and fresh groundwater groundwater circulation in this zone is affected by complex forcing mechanisms that operate on a range of timescales and can regulate chemical fluxes to marine environments we evaluated wave swash induced infiltration and associated flow dynamics in the unsaturated region of two sandy beach aquifers with differing wave conditions and beach morphologies moisture and pressure sensors were used to measure fluctuations in water content water table elevation and hydraulic gradients at high frequencies 5 hz in the swash zone at mean lower low water mean sea level and mean higher high water water content in the unsaturated region of the swash zone responded to wave overtopping and swash infiltration with a rapid rise in water content followed by a slower decline swash induced unsaturated infiltration rates calculated from water content response were lowest near low tide and increased up the beachface with inflow highest near high tide at both sites consistent with an increase in water table depth up the beach unsaturated infiltration was 1 6 m 3 m per tidal cycle at the wavedominated beach and 0 4 m 3 m per tidal cycle at the tide dominated beach saturated pore pressure measurements show that a water table mound formed as a consequence of swash infiltration that migrated up the beach during rising tide leading to divergent seaward landward groundwater flow the results demonstrate the significant and spatially variable effects of wave swash on moisture dynamics in the unsaturated zone of beach aquifers and show that these effects depend on wave conditions and beach characteristics results have implications for understanding transport and reaction of solutes in this biogeochemically active zone

on the role of infiltration and exfiltration in swash zone boundary layer dynamics boundary layer dynamics are investigated using a 2 d numerical model that solves the volume averaged reynolds averaged navier stokes equations with a vof tracking scheme and a k turbulence closure the model is validated with highly resolved data of dam break driven swash flows over gravel impermeable and permeable beds the spatial gradients of the velocity bed shear stress and turbulence intensity terms are investigated with reference to bottom boundary layer bl dynamics numerical results show that the mean vorticity responds to flow divergence convergence at the surface that result from accelerating decelerating portions of the flow bed shear stress and sinking injection of turbulence due to infiltration exfiltration hence the zero up crossing of the vorticity is employed as a proxy of the bl thickness inside the shallow swash zone flows during the uprush phase the bl develops almost instantaneously with bore arrival and fluctuates below the surface due to flow instabilities and related horizontal straining in contrast during the backwash phase the bl grows quasi linearly with less influence of surface induced forces however the infiltration produces a reduction of the maximum excursion and duration of the swash event these effects have important implications for the bl development the numerical results suggest that the bl growth rate deviates rapidly from a quasi linear trend if the infiltration is dominant during the initial backwash phase and the flat plate boundary layer theory may no longer be applicable under these conditions

field observations of the fluid granular boundary layer under near breaking waves numerous synchronized time series from video cameras pressure sensors current meters and hot film anemometers on natural beaches show that boundary layer development under the crest of near breaking waves can be idealized as a process composed of three distinct regimes here referred to as streaking roiling and pluming the roiling and pluming regimes fail to develop under the trough as a consequence there is a pronounced asymmetry in instantaneous sand transport and boundary layer phenomena between the wave crest and trough however laboratory waves with field scale periods and wave heights over thin sand beds do not exhibit this crest trough boundary layer asymmetry indicating that a critical element of similitude is absent in laboratory experiments we suggest that wave induced boundary ventilation is responsible

groundwater level changes in a coastal dune sea level fluctuations and shoreline movement on a sandy beach abstract it has been suggested earlier 1 that groundwater conditions may contribute to low frequency shoreline fluctuations with recurrence intervals of 0 5 10 years that proposition has been examined by comparison of a 7 year record of groundwater levels from coastal dune lands with mean sea level fluctuations and shoreline changes from the adjacent coast in an original analysis of western australian records 2 the annual cycles of sea level and shoreline change were observed to respond in an inverse manner such that a 1 0 cm rise in sea level approximately corresponds with a 1 0 m decrease on each profile in the present analysis the ratio ranges from 110 1 to 125 1 for oscillations in the annual to triennial band the ratio is less approximately 80 1 for the 0 5 year cycle these results are close to those reported from the original analysis in other respects however the sea level effect may be in dispute there is better agreement between time series describing the groundwater and shoreline fluctuations than between sea level and beach change the annual oscillation of the groundwater table is within 2 of being the inverse of that for the shoreline in the annual cycle sea level reaches its maximum in early winter during may june whereas the groundwater peak is highest during september october at a time when the beach is in its most depleted state

surge zones in the moine thrust zone of nw scotland abstract the caledonian thrust zones of assynt show several examples of large fault bounded structures surge zones up to 8 km 2 in extent which have moved further than adjacent rocks extensional faults can be traced into strike slip faults and then to contractional imbricate faults there are also zones of extensional and contractional flow as shown by strained bioturbation marks in the cambrian pipe rock several other low angle extensional fault zones have been recognized along the length of the moine thrust zone notably in the kinlochewe district recognition of these extensional faults and local surge zones has solved several local problems such as the lack of continuity of the glencoul thrust and the out of sequence character of some of the large low angle faults though the thrust propagation direction was generally from east to west in the transport direction several of the eastern faults have been reactivated later and locally cut down as extensional faults the so called moine thrust shows extensional fault movement at several localities along its length the extensional structures and the surge zones suggest that body forces have been important in driving the faults rather than just a push from the rear the moines and moine thrust zone were presumably driven to the wnw by gravity spreading and thinning of the main scottish caledonides

the capillary fringe and its effect on water table response abstract shallow water tables are often observed to respond in a highly disproportionate manner to precipitation events that is the magnitude of the response is often much greater than would be predicted on the basis of the specific yield of the geologic material and the amount of rainfall physical arguments are presented to show that if the capillary fringe the zone of tension saturation extends to ground surface then the addition of a very small amount of water can result in an immediate and large rise in the water table the arguments are supported by a field experiment in which the addition of 0 3 cm of water caused the water table to rise 30 cm in 0 25 min thus demonstrating the large and highly transient influence of the capillary fringe on the position of the water table the evidence in this study as well as recent work of others suggests that the capillary fringe effect could have a major influence on the process of stream flow generation contaminant transport to surface waters and contaminant transport in hydrogeologic regimes having shallow water tables it is further shown that calculations of groundwater recharge and consumptive use based on water table response and an assumed specific yield could be substantially in error

mechanical stratigraphy and fault fold interaction absaroka thrust sheet salt river range wyoming abstract a distinct contrast in deformation style from tightly folded and faulted cambrian through ordovician strata to broadly folded and faulted mississippian and younger strata is displayed in the hanging wall of the absaroka thrust salt river range wyoming based on style the paleozoic section can be divided into two main structural lithic units each unit is characterized by a relatively weak ductile anisotropic lower section and a relatively strong brittle more isotropic upper section where the two units were stacked within the thrust sheet inverted fault propagation folds formed in the center of each unit and the overall transition upward from close to wide spaced folds and imbricate faults developed in the multilayer where the upper unit was isolated deformation was dominated by imbricate faulting with little associated folding and inverted fault propagation folds did not form observations illustrate that the mechanical interaction between the two units and boundary conditions imposed on them were significant to defining the deformation response it is note worthy that the boundary between the two structural lithic unts in part defined by the roof thrust of the stewart passive roof duplex occurs within a dolostone rather than in overlying shale of the darby formation i propose that the roof thrust and other detachments in dolostone reflect the relatively low frictional strength of dolostone under shallow crustal conditions cross cutting relations suggest that the absaroka sheet was cut by large imbricate faults during late stage movement over a major dip ramp a high deviatoric and low mean compressive stress state just beyond the upper ramp flat corner promoted break back imbrication and allowed tectonic thickening of the thrust wedge necessary to reestablish critical taper and for forward translation

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

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

coupled surface subsurface hydrologic measurements reveal infiltration recharge and discharge dynamics across the swash zone of a sandy beach swash groundwater interactions affect the biogeochemistry of beach aquifers and the transport of solutes and sediment across the beachface improved understanding of the complex coupled dynamics of surface and subsurface flow processes in the swash zone is required to better estimate chemical fluxes to the sea and predict the morphological evolution of beaches simultaneous high frequency measurements of saturation water table elevation and the cross shore locations of runup and the boundary between the saturated and unsaturated beachface surface saturation boundary were collected on a sandy beach to link groundwater flow dynamics with swash zone forcing saturation and lysimeter measurements showed the dynamic response of subsurface saturation to swash events and permitted estimation of infiltration rates surface and subsurface observations revealed a decoupling of the surface saturation boundary and the intersection between the water table and the beachface surface measurements alone were insufficient to delineate the infiltration and discharge zones which moved independently of the surface saturation boundary results show for the first time the motion and areal extent of infiltration and recharge zones and constrain the maximum size of the subaerial discharge zone over swash and tidal time scales the width of the infiltration zone was controlled by swash processes and subaerial discharge was controlled primarily by tidal processes these dynamics reveal the tightly coupled nature of surface and subsurface processes over multiple time scales with implications for sediment transport and fluid and solute fluxes through the hydrologically and biogeochemically active intertidal zone of sandy beaches

reply to the comments by alsop and holdsworth on evidence for non plane strain flattening along the moine thrust loch strath nan aisinnin north west scotland

characteristics of sediment in transport in the swash zone of a steep estuarine foreshore cross shore grading of sediment has been observed on the surface of estuarine beaches but the swash zone processes responsible for this grading have not been measured this study was conducted to provide an explanation for the cross shore grading of sediment on a predominantly sandy estuarine foreshore data on wave and swash characteristics and sediment trapped in the uprush and backwash during 25 swash events were gathered from mid rising to mid falling tide on a small transgressive barrier in delaware bay new jersey usa sediment is predominantly quartz and feldspar medium to coarse sands with a gravel fraction of granules and pebbles wave energies increased with tidal rise the percentage of gravel in transport in the uprush and backwash is similar 11 and 13 during the rising tide when the swash zone is at mid foreshore decreases in the uprush 9 and increases in the backwash 18 when the swash zone is on the upper foreshore when the swash zone is at mid foreshore on the falling tide the quantity of gravel in the backwash 30 is greater than in the uprush 24 the low proportion of gravel within the foreshore prior to trapping and the increase in the percentage of gravel when the waves and swash are on the upper foreshore suggests that the step is the primary source of gravel high on the foreshore the size of the step increases as wave heights increase with tidal rise the rate of delivery of gravel into the swash is enhanced by sediment entrained during wave breaking and interaction of the uprush with the previous backwash the lag in the rate of step migration relative to breaker migration during the falling tide increases the likelihood of mining gravel from the step and subsequent transport in the uprush and backwash these findings are important for low energy estuarine beaches sensitive to small changes in tidal range and wave energy that cause sedimentological change across the foreshore

dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters in this study field data are presented that show for the first time the influence of a period of intensified wave conditions wave event on nearshore groundwater flows and geochemistry in a sandy beach field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines e g tides pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations the groundwater flows were simulated in feflow using a phase averaged wave setup approach to represent waves acting on the sediment water interface comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave induced perturbations in groundwater flows while prior studies have shown sharp ph and redox spatial zonations in nearshore aquifers this study reveals rapid temporal variations in conductivity ph and redox orp in shallow sediments up to 0 5 m depth in response to varying wave conditions comparison of head gradients with calculated conductivity and ph mixing ratios indicates the controlling effect of the wave induced water exchange and flows in driving the observed geochemical dynamics while we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes the ph and orp variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers

laboratory study on a beach drainage system abstract in recent years beach drainage systems bds have been considered as an innovative approach to stabilize the beachface even if it still has to be proven to what extent they are effective in stabilizing the beach or causing accretion this paper describes tests carried out at the grosser wellenkanal in hannover aimed at improving the knowledge of the hydrodynamic and morphodynamic behaviour of a beach containing a buried drainage system scale effects that affected previous bds laboratory experiments are minimized by the large scale the morphodynamic response of the undrained beach compared to a beach drained under the same type of wave action is reported experiments were undertaken using a set of multiple drains up to three working simultaneously located below the beach and at variable distances from the shoreline the experimental program was organized in a series of tests with variable wave energy while a positive effect was observed under low energy conditions for medium and high energy conditions the benefit of having the drains operative was not always clear in any case it was evident that any positive effect of the drains on the beachface was limited to the position of the cone of depression represented by the lowering of the hydraulic head

deformation of shale and dolomite in the lewis thrust fault zone northwest montana u s a the lewis thrust fault zone at marias pass northwest montana is an example of a fault zone in which hanging wall dolomite and footwall shale deformed at relatively shallow levels 7 km fabric in the fault zone depends on the rock type deformation of dolomite involved coalescence and widening by cataclasis of fractures formation of anastomosing cataclasite zones that isolate less deformed clasts and rounding and reduction in size of clasts to produce random fabric cataclasite whereas dolomite deformed by progressive widening of cataclasite zones shale deformation localized along ultracataclasite zones and slip surfaces that bound shale duplexes fault rocks that include both footwall shale and hanging wall carbonate are characterized by isoclinal intrafolial folds and a foliation that is defined by alternating shale and carbonate rich bands elongate lenses of carbonate and preferred orientation of phyllosilicates calcitization and subsequent solution of hanging wall rocks incorporated in the

measurement of wave by wave bed levels in the swash zone abstract a technique is described to observe and quantify wave by wave bed level changes in the swash zone the ultrasonic instrument system is non contact with the beach face surface being measured and the sensors remain outside of the fluid flows causing sediment movement sensor resolution combined with the electronic noise inherent within a digital network data logging system results in a conservative measurement accuracy of 1 mm equating to a couple of sand grain diameters in height illustrative field results demonstrate the practical use of the instrumentation and a simple data pre processing method to separate swashes and intervening bed level events is discussed these example data reveal rather complex fluctuations of the bed observed over time periods of minutes to hours rather strikingly gross bed level changes per wave are revealed to be up to many orders of magnitude larger than the observed net rate of beach face evolution it is outlined how observations of successive bed level changes at multiple locations within a dense grid combined with a consideration of sediment continuity will now enable the total net sediment transported per uprush backwash to be quantified

deformation within foreland thrust sheets by populations of minor faults the dominant deformation mechanism within foreland thrust sheets is the displacement of blocks of weakly deformed rock on discrete mineral coated minor faults in highly deformed layers at the bases of three southern appalachian foreland sheets such minor faults are members of families or populations of consistently oriented structures the deformation style is similar in all three sheets rock nearest each thrust was shortened in the direction of sheet transport and thickened by a family of faults oriented at low angles to the thrusts rock further above each thrust experienced only the first of these two deformation stages statistical analyses of fault populations from these three sheets demonstrate that their deformation is quantitatively as well as qualitatively similar deformation due to movement on minor faults is statistically homogeneous at the scale of an outcrop in one of these sheets strain due to minor faults can be measured in that sheet a strain profile across this sheet is similar to strain profiles across continuously deformed sheets from internal portions of mountain belts suggesting that their responses to emplacement are similar

cataclasites along the saltville thrust u s a and their implications for thrust sheet emplacement abstract cataclasis and frictional wear are the primary bulk deformation mechanisms along steeply dipping portions of the saltville thrust in the southern appalachian foreland zone u s a fault character ranges from a single discrete sliding surface with negligible gouge to a zone of several discrete sliding surfaces or a zone up to 0 3 m thick of pervasive cataclasite marked fracturing occurs up to 20 m above the fault whereas minimal deformation is found in the footwall rocks hanging wall dolomites range from crush breccias less than 5 matrix to ultracataclasites with 90 matrix although cataclasites 50 70 matrix are predominant foliated cataclasites occur where dolomite is thrust over shale progressive development of cataclastic fabrics is due to comminution by fracturing and grinding along intersecting fractures continued frictional grinding results in complete disruption of the original fabric to produce cataclasite and minor ultracataclasite grain alignment occurs by rigid body rotation with subsequent local enhancement by pressure solution microstructural relations of the fault gouge suggest periodic fluctuations in fluid pressure where v ratio of fluid to overburden pressure probably ranged between 0 45 and 1 the saltville thrust sheet emplacement must have occurred in a caterpillar like fashion involving aseismic and seismic shear shear stresses accompanying fault motion as determined from dolomite twin lamellae are in the order of 65 mpa

rapid water table fluctuations within the beach face implications for swash zone sediment mobility abstract to incorporate groundwater infiltration exfiltration in the description of swash zone sediment transport it is required that the details of groundwater dynamics within the beach face be clarified field measurements of the vertical pore pressure structure within the bed identify capillarity effects as the primary mechanism driving rapid and relatively large magnitude water table fluctuations within the swash zone when the upper extent of the fully saturated capillary fringe coincides with the beach face surface wave runup produces near instantaneous increase in pore pressures across the capillary fringe corresponding to a rapid rise of the phreatic surface i e the surface where pore pressure atmospheric pressure to the sand surface therefore counter to previous conclusions in the literature the rapid rise and fall of the water table under the swash zone do not equate to regions of the beach face alternating between states that favor sediment deposition unsaturated and erosion saturated similar reports that rapid fluctuations of the water table within the beach face correspond to rapid rates of vertical flow and hence bed fluidization are also a misinterpretation field measurements and a careful consideration of saturation and pore pressure characteristics within the beach face demonstrate that rapid water table rise is associated with minute downwards swash infiltration rather than rapid upwards groundwater exfiltration the cause of the pressure fluctuations and phreatic surface oscillations is the alternating appearance and disappearance of meniscuses at the sand surface which generate pressure head fluctuations of decimeters due to the addition of millimeters of water

swash groundwater dynamics in a sandy beach laboratory experiment abstract experiments are carried out in a wave basin in order to study the swash groundwater interaction a set of wave gages and pressure sensors are used to monitor the free surface and groundwater dynamics the study is based on the comparison of two selected cases which differ by the gravity and infragravity forcing conditions the features of wave breaking in the surf zone the presence of a standing wave attached to the beach face and the wave setup at the shoreline significant differences are observed in the response of the swash groundwater system the water table overheight appears to be controlled by the amount of infragravity energy available at the shore cyclic beach drainage processes can be observed when the water table is low significant time averaged and time resolved flows are observed into the sand depending on the swash hydrodynamics the presence of a gravity standing wave modulation attached to the shore is shown to affect swash and groundwater dynamics most of the pressure gradients observed under the swash zone are related to infiltration flows and are thus related to moderate increase of the sediment relative weight

suspended sediment transport mechanisms in high energy swash abstract measurements of suspended sediment concentration at three heights above the bed and cross shore velocity at a single height were obtained using miniature optical backscatter sensors and a miniature electromagnetic current meter from the swash zone of a high energy macrotidal dissipative beach time series from relatively low h s 0 8 m and high h s 2 2 m energy conditions were chosen for analysis possible onshore and offshore sediment transport mechanisms are identified as a sudden offshore to onshore velocity transition and turbulence in the swash front leading to subsequent onshore advection by the uprush and b low frequency high velocity backwashes exceeding a certain threshold for sediment suspension these mechanisms are related to the velocity field through skewness and asymmetry an increase in negative infragravity skewness in high energy conditions suggests a potential shift towards offshore net transport time averaged vertical profiles of cross shore suspended sediment flux were calculated from the velocity and concentration time series these show a tendency towards offshore transport in high energy conditions particularly at low levels in the water column the actual sediment fluxes are believed to be more offshore than those calculated one reason for this discrepancy is the inability of the instruments to detect swash activity at very low levels in the water column

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

capillary effects on groundwater response to earth tides author s wang cy zhu ay liao x manga m wang lp abstract 2019 american geophysical union all rights reserved the response of unconfined aquifers to earth s solid tides earth tides has been used to study a number of hydrogeological environmental and ecological processes the traditional interpretation of such responses has been based on a model that assumes free flow of groundwater to the water table even though capillary effects have long been recognized to influence the response of coastal aquifers to ocean tides here we study the capillary effect on the response of unconfined aquifers to earth tides using a numerical procedure that couples groundwater flow and poroelastic strain in both the saturated and the unsaturated zones we show that when the water table rises to the surface and the capillary zone disappears the predicted tidal response is identical to that predicted by the traditional model but when the capillary zone is present when the water table falls below the surface the predicted amplitude ratio and phase shift depart notably from those predicted by the traditional model we apply the model to a field case where large seasonal changes of tidal response have been documented we show that the large seasonal changes in the tidal response may be due to the change of the water table from a capillary affected state to a capillary free state when the water table rises annually to the ground surface thus the omission of the capillary effects in the interpretation of the response of unconfined aquifers to earth tides may lead to incorrect inference of subsurface processes and properties

variable swash motions associated with foreshore profile change variations in swash motions over a temporally changing foreshore surface are examined over the first tidal cycle following the onset of a storm using high resolution video observations obtained at duck north carolina a dramatic example of profile adjustment was observed where nearly 1 m of vertical change occurred over a 4 hour time period swash edge excursion measurements during this study compare favorably with predictions from standard equations describing ballistic motions of an object on a plane slope under quadratic friction and showed no strong asymmetries between uprush and backwash that might explain the profile adjustment instead these unique observations showed a tendency toward a predictable equilibrium between swash motions and profile response where the stability condition relates foreshore slope to incident wave period and initial uprush velocity using the ballistic equations under these conditions the foreshore adjusts to minimize the difference between swash duration and incident wave period on the basis of this finding a simple morphodynamic model for changes in foreshore slope as a function of swash and surf conditions is presented and allows prediction of the transition from an erosive to stable condition

measurements and modeling of swash induced pressure gradients in the surface layers of a sand beach field measurements of swash induced hydraulic pressure gradients in the surface layers of a sand beach are presented and compared to a one dimensional diffusion model the model provides a description of flow through a porous quasi saturated sediment and is driven by the time varying swash depth on the beach surface the field measurements broadly show four different types of pressure propagation behavior which appear dependent on cross shore position in the swash zone the hydraulic gradients within the surface layers of the beach are typically found to be much greater than those likely to be generated by tidally induced groundwater flow in these instances the diffusion model generally provides a good description of the data however very large hydraulic gradients are frequently observed just below the beach surface and these cannot be adequately described by the diffusion model a mechanism is proposed through which these large hydraulic gradients could be generated

suspended sediment transport and beach dynamics induced by monochromatic conditions long waves and wave groups abstract this study presents the analysis of the water surface elevation velocity and suspended sediment concentration measurements obtained at a large wave flume under mobile bed conditions the wave reproduced erosive and accretive conditions and included monochromatic short waves perturbed with a free long wave bichromatic and random conditions each tested condition started from a handmade 1 15 slope and lasted for an approximate time period of 2 4 h 6 runs of the selected wave condition to compare the different beach profile developments and in particular the events that control sediment transport in the swash and surf zones all erosive tested conditions produced a shoreline retreat and a bar at the breaking area whose development in time is directly correlated to the length of the breaking area on the other hand not all accretive conditions present a shoreward transport and random conditions do not seem to alter the initial profile the processed data show the suspended sediment event control produced by the existence or absence of wave backwash interactions in the swash zone the existence of these interactions and their number within the wave group will be a key parameter in controlling the sediment stirring water velocity magnitudes and therefore the suspended sediment fluxes in the inner surf and outer swash

tidal water table fluctuations in a sandy ocean beach tidal water table fluctuations observed for 27 days in a gently sloped ocean beach are predicted well by numerical models based on the boussinesq equation driven with the observed 10 min averaged shoreline ocean beach intersection motion diurnal and semidiurnal water table fluctuations are almost completely damped 100 m landward of the mean shoreline location on this fine grained sand beach but fluctuations at spring neap periods 14 days are attenuated less comparison of the observations with the predictions suggests that the asymmetries in the water table level time series measured in this study result from nonlinearity owing to the large relative to the wavelength horizontal shoreline excursions rather than from nonlinearity owing to finite amplitude water table fluctuations cross shore variations of the aquifer depth are predicted to have a small effect on the landward decay rate of the water table fluctuations the seepage face width is predicted accurately and depends on the nonplanar beach profile in general the development of a seepage face is predicted to have little effect on the water table level landward of the intertidal region

efficacy of beach dewatering alassio italy abstract the goal of this study is to estimate the efficiency of dewatering operations in alassio beach north italy by following an integrated approach which included beach volume calculations daily mapping of the shoreline position examination of specific beach widening events and daily comparisons of morphodynamic characteristics of the drained beach versus a control section which included wave run up bar patterns rip migration evolution of the berm and cusp morphology alassio beach was documented by a daily time lapse photography by repeated dgps profile measurements and by an hourly wave and sea level monitoring following one year of draining the shoreline position and the beach volume of the drained beach and the control section showed little differences i e accumulation of 0 28 m 3 m 2 and a shoreline advance of 1 1 m on the drained beach whereas on the control beach the volume change was 0 03 m 3 m 2 and the shoreline retreated 1 2 m short episodes of beach widening 1 7 days long which coincided with onshore bar movement and a relative low sea level occurred simultaneously on the drained and the control sector this data indicated the inefficiency of the draining operation an improved resolution for determining the draining effect was attained by the sequential snap shot photography which showed many systematic morphological differences between the drained beach and the reference segment the drained beach developed a berm crest and a linear often scarped foreshore with a narrow swash zone no such cumulative morphologies were observed on the non drained control beach which commonly displayed cusps that were usually absent on the drained foreshore the wave data showed recurrent medium wave events of hs 1 2 m which repeatedly interrupted the calms thus cutting off the beach evolution the draining in alassio was unable to promote beach accumulation by counteracting the erosive effect of the medium interrupting storms

validation of a boussinesq model of beach ground water behaviour abstract a numerical solution to the 1 d boussinesq ground water equation is used to predict water table response to tidal and wave forcing we argue that the solution presented here offers considerable advantages over other solutions to the 1 d boussinesq ground water equation and is simpler to apply than 2 d ground water models the main assumption in using the boussinesq equation is that ground water flow in a shallow aquifer can be described using the dupuit forchheimer approximation in which it is assumed that changes in hydraulic head with depth below the water table are negligible the predictive ability of the solution was tested against field data from ten wells and ten piezometers on a microtidal sandy beach two model runs were carried out in the first the effect of tides only was considered in the second setup due to waves was also considered the arithmetic mean of independently measured values of hydraulic conductivity was used to describe sediment characteristics the piezometer data show that changes in hydraulic head with depth are negligible for much of the beach suggesting that the use of the boussinesq equation is appropriate the correspondence between model predictions of water table elevations and field observations is good for both the tide only and the tide plus setup model runs with the latter giving the better predictions

from fine sand to boulders examining the relationship between beach face slope and sediment size abstract it is a long standing maxim that coarser sediment sizes are associated with steeper beach face slopes but because most work has focused on sandy beaches few data are available for the pebble cobble or boulder size ranges little is known therefore about how beach morphology and grain size relate at the coarser size grades we compiled data from the literature 2144 measurements of beach face slope with associated grain sizes covering the range from very fine sand to boulders this meta analysis shows that beach faces do tend to steepen as average grain size increases at least up to the cobble size range but the trend is not simple although previous studies suggested a simple power law relationship between grain size and beach face slope in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens and may trend downward for boulders fine and medium sands have the greatest range of reported slopes and the data support the importance of effective weight modification and boundary layer dynamics as primary controls on beach face steepness at these fine size grades around the very coarse sand size grade a plateau marks a shift in beach dynamics as hydraulic conductivity increases beaches switch to being infiltration dominated the trend toward steeper slopes continues but at a lower and steady rate from granules through cobbles there appears to be a falloff in slope for the coarsest boulder deposits but we note that this is based on very few locations so should be considered preliminary the overall data distribution is described by a power law function tan a d 50 0 125 b c the broadness of each transition zone also shows that a range of factors other than grain size governs where that tipping point occurs in the cobble and boulder size ranges there are two deposit categories boulder beaches and supratidal boulder ridges although not commonly thought of as beaches boulder ridges record long term storm deposition and reworking on the highest energy coasts supratidal ridges and boulder beaches seem to show different slope grain size relationships with the steepest slopes occurring in boulder ridges and with boulder beaches showing more gentle gradients than other coarse clastic beaches but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum and invites further work to investigate the sedimentology of cobble and boulder dominated systems

post emplacement extension within a thrust sheet from the central pyrenees secondary faults and related veins in a small thrust sheet the pic de port vieux thrust sheet in the footwall of the gavarnie thrust in the central pyrenees are used to infer the deformation sequence that accompanied its emplacement initial deformation was characterized by distributed bedding parallel simple shear this was superseded by localized deformation involving arrays of extensional faults the first faults to form were x shears and were succeeded first by conjugate faults x x9 shears and then arrays of r shears that locally cut the thrust i e developed subsequent to its emplacement extension veins are used to infer the orientation of the ambient stress system during the deformation sequence a forward rotation of the stress sytem towards the vertical was associated with the x and x x9 shears and is considered to reflect loading of the 4 km thick overlying gavarnie thrust sheet a later backward rotation of the stress system then occurred returning 1 to 45 obliquity to the pic de port vieux thrust and was associated with the r shear development this later event produced extensional shearing of the thrust sheet and is equated with a proposed episode of spreading gliding within the overlying thrust pile a model for this spreading gliding relates it to the active tectonics of the developing south pyrenean thrust belt

periodic seepage face formation and water pressure distribution along a vertical boundary of an aquifer detailed measurements of the piezometric head from sand flume experiments of an idealised coastal aquifer forced by a simple harmonic boundary condition across a vertical boundary are presented the measurements focus on the pore pressures very close to the interface view the mathml source and throw light on the details of the boundary condition particularly with respect to meniscus suction and seepage face formation during the falling tide between the low and the mean water level the response is consistent with meniscus suction free models in terms of both the vertical mean head and oscillation amplitude profiles and is consistent with the observation that this area of the interface was generally within the seepage face above the mean water level the influence of meniscus formation is significant with the mean pressure head being less than that predicted by capillary free theory and oscillation amplitudes decaying faster than predicted by suction free models the reduced hydraulic conductivity in this area due to partial drainage of pores on the falling tide also causes a delay in the response to the rising tide the combined influence of seepage face formation meniscus suction and reduced hydraulic conductivity generate higher harmonics with amplitudes of up to 26 of the local main harmonic to model the influence of seepage face formation and meniscus suction a numerical solution of the richards equation was developed and evaluated against the data the model data comparison shows a good agreement with the behaviour high above the water table sensitive to the choice of moisture retention parameters

thrust fault mechanics and dynamics during a developmental stage of a foreland belt abstract studies of continental seismogenic zones indicate that deformation during an orogenic stage is episodic and spasmodic down to mid crustal depths and that seismic as well as aseismic modes of deformation need to be incorporated in quantitative theories of foreland belts such a theory is developed here it includes a method to help decipher the development of structures such as imbricate fans frontal ramps and ramp anticlines as illustrated for the hogsback frontal ramp and its ramp anticline in the kemmerer region of the wyoming salient the structure of the hogsback ramp is consistent with a shear fracture origin limit equilibrium mechanics indicate that shear failure would have proceeded incrementally possibly in response to recurring fault slip on the basal decollement contrasts in elastic constants and rock strength are critical e g current data indicate that shear failure development of the ramp would have begun 1 fourth fifth s distance down the ramp in competent madison carbonates if they compared in strength with the marianna limestone or 2 higher in the section if the madison compared in strength with the hasmark or blair dolostones whether the initial development of the ramp anticline involved seismic modes is not clear yet but elastic stiffness data indicate that subsequent imbrication of the anticline did involve seismic as well as aseismic modes of deformation

microstructures of cataclasites in a limestone on shale thrust fault implications for low temperature recrystallization of calcite abstract the hunter valley thrust hvt a low temperature foreland thrust fault in the valley and ridge province southern appalachians produced two distinct cataclasites a limestone cataclasite derived predominantly from the hanging wall limestone and a shale cataclasite derived predominantly from the footwall shale the limestone cataclasite consists of fragments of calcite limestone pre existing limestone cataclasite quartz and quartz aggregates in a fine grained

secondary cleavages in ductile shear zones abstract secondary cleavages developed at late stages in ductile shear zones show several features that are inconsistent with progressive simple shear in the zone these are the orientation of a single secondary cleavage oblique to the shear zone boundaries conjugate sets with opposite senses of shear and multiple sets with the same sense of shear these features can be explained if the bulk flow is partitioned into slip along discrete failure planes parallel to the primary foliation s coaxial stretching along the foliation and spin

groundwater waves in a coastal aquifer a new governing equation including vertical effects and capillarity groundwater waves that is water table fluctuations are a natural phenomenon in coastal aquifers they represent an important part of the interaction between the ocean and aquifer and affect the mass exchange between them this paper presents a new groundwater wave equation because it includes the effects of vertical flows and capillarity the new equation is applicable to both intermediate depth aquifers and high frequency waves compared with the wave equation derived by nielsen et al 1997 the present equation provides a closer representation of groundwater waves in particular it predicts high frequency water table fluctuations as observed in the field a validation of the new equation has been carried out by comparing the analytical solutions to it with predictions from direct simulations using the numerical model sutra the effects of various physical parameters and their relative importance are also discussed

infiltration effects on sediment mobility under waves sediment mobility measurements with a horizontal sand bed under non breaking waves are reported conditions include no seepage and steady downward seepage corresponding to head gradients up to 2 5 the results indicate that infiltration tends to inhibit sediment mobility for a horizontal bcd of 0 2 mm quartz sand exposed to moderated wave induced bed shear stresses the effect is weak for the parameter range of the present study the two opposing effects of shear stress increase due to boundary layer thinning and the stabilizing downward drag are successfully accounted for through the modified shields parameter of nielsen nielsen p 1997 coastal groundwater dynamics proc coastal dynamics 97 plymouth asce dp 546 555 using coefficients derived from independent studies that is from the shear stress experiments of conley conley d c 1993 ventilated oscillatory boundary layers phd thesis university of california san diego 74 pp and the slope stability experiments of martin and aral martin c s and m m aral 1971 seepage force on interfacial bed particles j hydraulics div proc asce vol 97 no hy7 pp 1081 1100 c 2001 elsevier science b v all rights reserved

plasticity and diffusion creep of dolomite abstract natural and synthetic dolomites have been shortened in triaxial compression experiments at temperatures of 400 850 c equilibrium co2 pore pressures effective confining pressures of 50 400 mpa and strain rates of 10 4 to 10 7 s 1 at low temperatures t 600 mpa both for coarse grained 240 m and fine grained 2 m and 12 m samples differential stresses vary little with strain rate or temperature and microstructures of coarse grained samples are dominated by f twins and undulatory extinction an exponential relation o exp 1 3 between strain rate and differential stress 1 3 describes the crystal plasticity of dolomite at a fixed pe and t with 0 079 0 01 mpa 1 and 0 023 07 03 mpa 1 for coarse and fine grained materials respectively however measured values of 1 3 increase with increasing temperature a trend that has been observed for dolomite single crystals but cannot be described by an arrhenius relation at high temperatures t 800 c for coarse t 700 c for fine dolomite strengths are reduced with increasing temperature and decreasing strain rate but the mechanisms of deformation differ depending on grain size high temperature flow strengths of coarse grained dolomite can be described by a power law o 1 3 nexp h rt with a large value of n 5 and a ratio of parameters h n 60 6 kj mol microstructures of coarse grained samples deformed at t 800 c show evidence of dislocation creep with little mechanical twinning high temperature flow strengths of fine grained synthetic dolomite fit a thermally activated newtonian law where the effective n 1 28 0 15 and h 280 45 kj mol consistent with diffusion creep the change in mechanical response of coarse grained natural dolomite with increasing temperature represents a transition from twinning and slip with little or no recovery to dislocation creep while the change in response of fine grained synthetic dolomite represents a transition from crystal plasticity to diffusion creep the combined results for coarse and fine grained dolomites define a deformation mechanism map with fields of crystal plasticity dislocation creep and diffusion creep strengths of coarse grained dolomite in the crystal plastic and dislocation creep fields are much larger than strengths of calcite rocks deformed by similar mechanisms in contrast strengths of fine grained dolomite deformed by diffusion creep are more comparable to those of fine grained calcite suggesting little contrast in rheology

evaluation of a small beach nourishment project to enhance habitat suitability for horseshoe crabs abstract this field study evaluates the effect of nourishing an estuarine beach with gravel to enhance spawning rates by horseshoe crabs a total of 564 m 3 of coarse sand and gravel were emplaced in two 90 m long treatment segments at bowers beach delaware usa from 9 to 11 april 2002 field data were gathered between 6 april and 24 may 2002 to characterize the two fill segments and the un nourished segments between them as well as two control segments at the adjacent ted harvey beach sediment samples were taken from the foreshore surface and at depth before and after the nourishment bay water levels wave heights and beach ground water characteristics were monitored over a 12 hour tidal cycle at one of the nourished 15 may 2002 and the unnourished segment 16 may 2002 at bowers beach and at one of the control segments at ted harvey beach 21 may 2002 using piezometers and pressure transducers inserted in wells the beaches were cored to estimate the density of horseshoe crab eggs deposited during the spawning season horseshoe crab eggs were buried in pouches at 0 15 to 0 20 m depth for 30 to 40 days to evaluate their survival in developing into embryo or larval stage bulk sediment samples were taken to evaluate moisture characteristics near locations where egg pouches were buried density of spawning females at bowers beach was 1 04 m 2 in 2001 and 1 20 m 2 in 2002 these rates are lower than at ted harvey beach but reveal an increase in spawning while ted harvey beach underwent a considerable decrease 2 63 m 2 to 1 35 m 2 sediments low on the foreshore remained nearly saturated throughout the tidal cycle at both beaches the average hydraulic conductivity on the upper foreshore at the non treatment section at bowers beach 0 19 cm s 1 was less than at ted harvey beach 0 27 cm s 1 and the finer better sorted sediments at depth at bowers beach resulted in a higher porosity creating greater moisture retention potential egg development was greatest at mid foreshore at all sites eggs at the lower foreshore elevation remained viable but did not develop to the embryo stage between beach differences were limited to high elevations where higher mortality occurred at ted harvey beach due to desiccation adding small amounts of gravel to a sand beach may change the appearance of the surface but may not appreciably increase mean grain size and sorting at depth or the hydraulic conductivity over the spawning season the pebble fraction may be important for site selection but finer sizes may be more important for egg survival because of moisture retention

beach groundwater dynamics abstract an understanding of the interaction between surface and groundwater flows in the swash zone is necessary to understand beach profile evolution coastal researchers have recognized the importance of beach watertable and swash interaction to accretion and erosion above the still water level swl but the exact nature of the relationship between swash flows beach watertable flow and cross shore sediment transport is not fully understood this paper reviews research on beach groundwater dynamics and identifies research questions which will need to be answered before swash zone sediment transport can be successfully modelled after defining the principal terms relating to beach groundwater the behavior measurement and modelling of beach groundwater dynamics is described research questions related to the mechanisms of surface subsurface flow interaction are reviewed particularly infiltration exfiltration and fluidisation the implications of these mechanisms for sediment transport are discussed

thrust related strain gradients and thrusting mechanisms in a chevron folded sequence southeastern australia an e directed imbricate fan thrust system within a chevron folded monotonous quartz rich turbidite succession shows marked gradients in strain from the upper to lower parts of individual thrust sheets upper parts of thrust sheets show low to moderate strains xz strains 30 1 tight inclined chevron folds ila 30 with predominantly w dipping axial surfaces intense phyllitic cleavage with a strong down dip mineral stretching lineation and long curved tapering quartz pressure shadows on pyrite such differences in fold geometry the intensity of the cleavage and the geometry of quartz fibres in pressure shadows require thrust sheet emplacement to be synchronous with the internal deformation of sheets thrust sheets show a change from an approximately constant volume plane strain coaxial deformation in their upper parts to non coaxial high strain deformation with incremental i between those expected for pure shear and simple shear i e 0 i 5 45 in their basal parts observed geometries and intensities reflect partitioning of strain and deformation mechanisms within individual thrust sheet volumes both during the initiation and propagation of subsurface detachment faults and with their emplacement to shallower crustal levels strain softening related to chevron folding and more intense cleavage development within a 500 m basal zone has controlled the emplacement of these turbidite dominated thrust sheets transport and internal deformation of the thrust sheets did not involve gravitationally induced spreading but required either a push from the rear or some form of underthrusting

turbulence in the swash and surf zones a review this paper reviews mainly conceptual models and experimental work in the field and in the laboratory dedicated during the last decades to studying turbulence of breaking waves and bores moving in very shallow water and in the swash zone the phenomena associated with vorticity and turbulence structures measured are summarised including the measurement techniques and the laboratory generation of breaking waves or of flow fields sharing several characteristics with breaking waves the effect of air entrapment during breaking is discussed the limits of the present knowledge especially in modelling a two or three phase system with air and sediment entrapped at high turbulence level and perspectives of future research are discussed

incipient extension along the active convergent margin of nubia in sicily italy cefalu etna seismic zone 1 recent geodetic data are compatible with nne ssw tectonic extension at a rate of 5 mm yr in sicily southern italy within a broader region of net active compression along the nubian plate margin northern africa the structures that accommodate such extensional regime and its cause are still unknown from field structural surveys and seismological analyses the geometry kinematics structural architecture and seismic potential of an extensional seismic zone linking cefalu and mount etna in central eastern sicily are defined the zone includes high angle wnw striking normal and right lateral strike slip faults and subordinate north and nne striking strike slip faults either right or left lateral the occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage the ongoing seismic activity possibly reactivates preexisting faults instrumentally and historically recorded earthquakes are lower than about 6 in magnitude and destructive events are historically unknown since at least 1300 a d this apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms which all together suggest a value between 6 and 6 5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area lateral extension on preexisting faults and upwelling of melt mantle material beneath mount etna are considered viable processes to explain at least in part the active extensional tectonics along the cefalu etna seismic zone strike slip seismic faulting beneath mount etna may be part of a previously proposed diffuse transfer zone affecting northeastern sicily and including the tindari fault

influence of infiltration on suspended sediment under waves the effect of percolation through a permeable bed on sediment suspension under regular waves was examined in a laboratory wave tank 28 in x i in x 1 in using acoustic backscatter sensors to make rapid 3 hz suspended sand profile measurements 0 005 m vertical resolution waves of 1 7 s period and heights ranging from 0 14 to 0 185 m were used over sand with a d 50 of 255 mum infiltration velocities of 0 5 0 x 10 4 m s 1 were used with percolation through an initially flat bed ripple development was suppressed particularly at lower wave heights ripples took longer to form and were more three dimensional suspension was also suppressed the total suspended load was correlated with shields number at the 1 significance level when the shields number was modified to take account of both the infiltration nielsen p 1997 coastal groundwater dynamics proceedings of coastal dynamics american society of civil engineers pp 546 555 and ripple steepness coastal eng 1986 23 the ripple steepness was found to be the most important factor relating to the reduction in the total suspended loads the influence of infiltration on time averaged concentration profiles over equilibrium ripples was investigated by switching the percolation on and off for 5 min periods the total suspended loads were reduced by up to 50 with percolation on these results suggest that fluctuation of the water table and drainage within a beach will affect sediment transport and ripple dynamics and that for sand of 0 25 mm percolation will tend to reduce suspension and transport c 2002 elsevier science b v all rights reserved

partitioning of deformation within several external thrust zones of the appalachian orogen mesoscopic contractional and extensional faults dominate many external thrust zones the fault arrays occur in the hanging walls of some thrusts and in the footwalls of others in a thrust zone from the little mountains fold thrust belt of new york state mesoscopic faults cut and offset a major thrust contact and involved rocks from the thrust s hanging wall and its footwall simultaneously the little mountains exposure indicates that minor faults were active during thrust slip and are not early formed features which were passively translated with the remainder of a sheet when both contractional and extensional mesoscopic faults occur in thrust zones foreland dipping extensional faults overprint contractional faults contractional and extensional microfaults with r 1 and r 2 riedel shear geometries are common in external thrust zone cataclasites and resemble the mesoscopic fault patterns though the evolution of cataclasite layers differs from that of mesoscopic fault arrays contraction and ext

a numerical empirical approach for evaluating morphodynamic processes on gravel and mixed sand gravel beaches abstract pedrozo acuna et al pedrozo acuna a simmonds d j otta a k and chadwick a j 2006 on the cross shore profile change of gravel beaches coastal engineering 53 4 335 347 presented a numerical empirical investigation of the processes that control sediment transport in the swash zone on steep gravel beaches this was based on a sensitivity analysis of a sediment transport profile model driven by a highly non linear boussinesq model lynett p j wu t r and liu l f p 2002 modelling wave run up with depth integrated equations coastal engineering 46 89 107 which was compared to near full scale measurements performed in the gwk flume in hanover in this paper we have extended our analysis to compare these earlier results with those relating to a mixed sediment gravel and sand beach the parametric sensitivity analysis also incorporates a discussion of the effects of acceleration about which there is much debate the sensitivity analysis suggests that fluid acceleration can contribute to the onshore movement of sediment that causes steepening of initially flat beach faces composed of coarse sediment however acceleration alone cannot be the cause of the observed berm growth during the gwk tests instead a complex balance of processes is responsible for the profile evolution of coarse grained beaches with no single dominant process

paleostresses associated with faults of large offset abstract in order to test empirically the limitations of paleostress analysis we used etchecopar s computer program to compute the orientations and relative magnitudes of paleostress principal values in two southern appalachian u s a thrust zones from minor fault and slickenside attitudes in both thrust zones faults are closely spaced many faults have offsets whose magnitudes exceed the distance to adjacent faults of comparable size and deformation was strongly non coaxial while even in the less deformed thrust zone bulk strains due to fault movement have axial ratios as high as 10 1 nearly 75 of the fault slickenside pairs in each thrust zone conform with paleostress tensors that indicate 1 sequential transport parallel compression transport parallel extension and extension oblique to transport and 2 low resolved shear stresses on the thrusts finite strains measured in one thrust zone share a principal plane with the first two tensors and the inclinations of the paleostress and finite strain principal directions in that plane are consistent with thrust parallel shearing relative magnitudes of paleostress and strain principal values do not correlate well moreover the locations and inferred origins of fault slickenside pairs inconsistent with paleostress tensors suggest that stresses in rocks between faults were not as is assumed in paleostress analyses uniform this complexity may also occur in faulted rocks where bulk strains are small paleostress tensors from rocks with large bulk strains may be viable but they must be interpreted cautiously

evidence for non plane strain flattening along the moine thrust loch srath nan aisinnin north west scotland we report quartz c axis patterns grain shape fabrics and microstructures for 11 mylonitic quartzites and quartz phyllosilicate schists from a transect across the moine thrust at loch srath nan aisinnin north west scotland in the footwall samples collected more than 42 m normal distance from the thrust surface quartz c axis textures indicate a general flattening strain i e 0 k 1 samples within 19 m normal distance of the thrust are completely recrystallized and exhibit asymmetric c axis patterns recrystallized hanging wall fault rocks exhibit random c axis patterns on the scale of a standard thin section relict footwall grains provide the closest approximation of finite strain they have octahedral shear strains s between 1 10 and 1 47 and exhibit general flattening k values 0 0524 0 659 the long axis of the mean relict grain shape trends parallel to the regional transport direction and plunges gently to the ese in contrast recrystallized footwall grains have a mean grain shape with the longest axis oriented nearly perpendicular to the transport direction furthermore these samples have grain shape k value ranges from 0 157 to 0 295 recrystallized hanging wall grain shapes exhibit the lowest octahedral shear strains s 0 532 0 733 and largest mean k values 0 351 0 961 of this sample set the long axes of the mean recrystallized hanging wall grain shapes are parallel to transport similar to that of relict footwall grains unrecrystallized quartz overgrowths about opaque mineral grains suggest concurrent elongation in all directions within the mylonitic foliation and support the inference of general flattening deformation the mylonitic foliation and penetrative lineation are consistent with a wnw shearing direction however both were folded during later deformation increments recrystallized grains in footwall quartzites suggest a 305 320 azimuth for the shearing direction the best fit axis of the poles to the foliation is 18 145 close to the mean trend plunge of mesoscopic fold hinges at this site 18 151 both suggest a nnw azimuth for the shearing direction thus structural microstructural and fabric indicators suggest a change in the azimuth of the shearing direction from 286 to 331

interaction of cataclasis and pressure solution in a low temperature carbonate shear zone the mineralogical and elemental variations across the main shear zone of the saltville thrust at sharp gap in knoxville tennessee u s a were studied in a suite of deformed and undefromed carbonate rock samples using x ray diffraction and electron microprobe methods an examination of the samples for deformation effects at mesoscopic scale and under the optical microscope reveals familiar cataclastic deformation features including foliated cataclasites and microbreccias occurring in a well defined 1 2 m wide zone of intense deformation plus evidence of hydrofracturing and extensive syndeformational pressure solution there exists a clear correlation between the observed cataclastic deformation and mineral and elemental distribution which we interpret to result from a deformation induced dolomite to calcite transformation in the shear zone the transformation has resulted in removal of mg from the shear zone selective deposition of calcite as an intergranular cement in cataclasite microbreccia units and a relative increase in the concentration of detrital quartz and feldspars the compositional difference between the shear zone and wall rocks is explained in connection with cataclastic deformation features in terms of a model in which a dual pressure solution cataclastic flow mechanism leads to a gradual cementation hardening of segments of the shear zone instabilities could occur via permeability reduction and increased pore pressure within these segments hydrofracturing of the hardened segments along with high strain rate reordering of the shear zone materials reset the ruptured zone back to the dual deformation mechanism regime as a long term effect the compositional transformation of the shear zone is expected to prolong periods of creep and cause smaller coseismic stress drops since under the imposed conditions calcite is more ductile and soluble than dolomite

strain hardening and strain softening in fault zones from foreland thrusts the movement of thrust sheets is accomplished in part by deforming the rocks adjacent to thrust faults in foreland fold and thrust belts emplacement generates an array of mesoscopic faults in a thick layer along the base of a sheet ductile deformation of rocks in the layer occurs by displacing fault bounded blocks relative to one another in a kind of mesoscopic grain boundary sliding analyses of data from three southern appalachian thrust sheets indicate that this block sliding is first accompanied by strain hardening then by strain softening and it is accommodated by intra block fractures small faults and veins the density of accommodation features increases near thrusts and where these features become sufficiently numerous a layer of cataclastic rocks forms along the thrust we describe foliated cataclasites from two thrusts the microstructures of which indicate that the cataclasites exhibited extreme ductility interrupted occasionally by brittle processes deformation of the cataclasites was accompanied by strain softening strain softening deformation in fault arrays near thrusts is genetically related to strain softening deformation in cataclasites during the formation of the cataclasite rocks in the sheet are impelled to cross a strain energy hump after which they deform at either higher rates or lower stresses

heat transport dynamics at a sandy intertidal zone 1 intertidal zones are spatially complex and temporally dynamic environments coastal groundwater discharge including submarine groundwater discharge may provide stabilizing conditions for intertidal zone permeable sediments in this study we integrated detailed time series temperature observations porewater pressure measurements and two dimensional electrical resistivity tomography profiles to understand the coupled hydraulic thermal regime of a tropical sandy intertidal zone in a fringing coral reef lagoon rarotonga cook islands we found three heating patterns across the 15 m study transect over tidal and diel periods 1 a highly variable thermal regime dominated by swash infiltration and changes in saturation state in the upper foreshore with net heat import into the sediment 2 a groundwater supported underground stable cool region just seaward of the intertidal slope break also importing heat into the subsurface and 3 a zone of seawater recirculation that sustained consistently warm subsurface temperatures that exported heat across the sediment water interface simple calculations suggested thermal conduction as the main heat transport mechanism for the shallow intertidal sediment but deeper and or multidimensional groundwater flow was required to explain temperature patterns beyond 20 cm depth temperature differences between the distinct hydrodynamic zones of the foreshore site resulted in significant thermal gradients that persisted beyond tidal and diel periods the thermal buffering of intertidal zones by coastal groundwater systems both at surface seeps and in the shallow subsurface can be responsible for thermal refugia for some coastal organisms and hotspots for biogeochemical reactions

lattice preferred orientation development in experimental and natural fine grained dolomite shear zones abstract we compare microstructures and lattice preferred orientations lpo in shear zones formed in two experimentally deformed and two naturally deformed dolomites experimental samples were deformed at 900 c and laboratory strain rates and naturally deformed dolomites were collected from the pioneer landing thrust and town knobs thrust of the southern appalachians deformed at 300 c and 240 c respectively at tectonic strain rates coarse grained host dolomite in all samples exhibits undulatory extinction subgrains recrystallized grains and in the naturally deformed dolomites fractures two types of fine grained shear zones are characterized in experimentally deformed dolomites 1 a fine grained zone of recrystallized dolomite generated during axial shortening of coarse grained dolomite that initially deformed by dislocation creep with strain localization initiated by grain size sensitive deformation processes and 2 a synthetic fine grained dolomite layer placed between coarse grained dolomite shear pistons microstructures and lattice preferred orientations of the experimentally sheared dolomite reflect the concomitant operation of dislocation creep diffusion creep and grain boundary sliding microstructures including subgrains recrystallized grains and four grain junctions and lattice preferred orientations that consist of weak c axis maxima in the natural shear zones are similar to the experimental shear zones however a slightly stronger lpo more common subgrains and the lack of four grain junctions indicate that dislocation creep dominates within dolomites deformed at lower temperatures 240 c

pollutant advective spreading in beach sand exposed to high energy tides abstract this paper presents field measurements in which dye solute was injected into coastal sand to investigate contaminant advection in intertidal beach sand the measurements show the pathways of a contaminated plume in the unsaturated zone during both the flood and ebb tides a prescribed amount of dye tracer solution was directly injected through the topsoil with average porosity 0 3521 0 01 at predetermined locations of the river mersey s outer estuarial beach during ebb tide the injected dye was monitored sampled and photographed over several tidal cycles the distinctive features of the plume full two dimensional cross sections sediments and water table depth were sampled in situ close to the injection point differing from previous contaminant monitoring tests in aquifers the advective movement is attributed to tidal impact which is different from contaminant transport in aquifers the experimental results show that plumes have significantly large spatial variability diverging upwards and converging downwards with a conical geometric shape which is different from the usual spherical elliptical shape reported in literature the mean vertical motion of the plume reaches three times the top width within ten tidal cycles exceeding the narrow bottom width by a factor of order 2 the observed transport features of the plume within the beach sand have significant relevance to saltwater intrusion surface water and groundwater quality the field observations are unique and can serve as a valuable benchmark database for relevant numerical studies

stratal extension in thrust footwalls makran accretionary prism implications for thrust tectonics small scale stratal extension is commonly associated with thrust faults in the makran accretionary prism of southwest pakistan low angle normal faults dipping in the direction of transport relative to the thrust are common in gouge zones and duplexes and may also cut the footwall and hanging wall where they cause stratal extension these faults are probably riedel shears we have studied a broad zone of more complex extensional deformation beneath one bedding parallel thrust the zone disrupts earlier compressional structures and affects a significant volume of the footwall normal faults initiating in a rearward sequence branch off the thrust and cut down into the footwall merging at a lower stratigraphic level part of the thrust displacement was thereby transfe red to that level and fragments of the footwall were detached and transferred southward beneath the hanging wall the latter remained undeformed and accommodation structures are confined to the footwall these effects may have been caused by variations in sliding resistance along the fault if a thrust transfers part or all of its displacement down section along normal faults in this way before eventually cutting back up toward the surface it will detach a rootless fragment of footwall rocks from a position forward of the initial ramp through that horizon this process can be referred to as footwall plucking it can explain rootless basement slices along thrusts for example and it has important implications for section restoration techniques and the interpretation of thrust belts

the subsidence of the williston basin a detailed comparison between the pre cretaceous stratigraphic record in the williston basin and the available information about phanerozoic sea level changes indicates that most stratigraphic breaks in the basin reflect eustatic control the basin appears to have been subsiding continuously and steadily about the same centre for most of the phanerozoic above a thick 55 km continental crust deposition kept up with subsidence and most of the sedimentary record was laid down close to sea level erosional breaks in the stratigraphic record may represent periods of removal of strata during episodes of low sea level a possible explanation of this essentially steady nonexponential subsidence record is that a mafic subcrustal body is undergoing transformation to eclogite

swash infiltration exfiltration and sediment transport field measurements of vertical pore pressure gradients within the bed are used to quantify instantaneous 8 hz rates of swash infiltration exfiltration across the beach face cyclic infiltration exfiltration is associated with individual swash events with observed vertical flow rates o 10 3 m s rates of net swash groundwater exchange i e through bed flow integrated over several swash cycles are two orders of magnitude smaller at the timescale of individual swashes vertical pore pressure gradients within the beach face are much greater than horizontal pore pressure gradients this permits application of the numerical solution of darcy s law for one dimensional vertical flow to model fluctuating pore pressures and hence vertical through bed flow vertical flow through a porous bed modifies sediment mobility in at least two ways 1 seepage forces change the effective weight of surficial sediments and 2 boundary layer thickening or thinning result in altered bed shear stresses by considering these two opposing effects separately a new shields parameter is derived that incorporates terms for through bed flow simulation of time varying seepage force and bed stress effects over an uprush backwash cycle suggests that the effect of altered bed stresses dominates over the change in effective weight and that infiltration exfiltration effects are most important during uprush simulated transport rates are increased by up to 40 of the peak transport rate during uprush and reduced by 10 during backrush in summary swash infiltration exfiltration across a saturated beach face enhances the net upslope transport of sediment

a numerical study of swash flows generated by bores abstract article history received 10 october 2007received in revised form 15 march 2008accepted 4 april 2008available online 4 june 2008keywords swash zonetsunami runupdam breakborenon linear shallow water equationsreynolds averaged navier stokes equationnon linear k model the dynamic processes of bore propagation over a uniform slope are studied numerically using a 2 dreynolds averaged navier stokes rans solver coupled to a non linear k turbulence closure and avolume of uid vof method the dam break mechanism is used to generate bores in a constant depthregion present numerical results for the ensemble averaged ow eld are compared with existingexperimental data as well as theoretical and numerical results based on non linear shallow water nsw equations reasonable agreement between the present numerical solutions and experimental data isobserved using the numerical results small scale bore behaviors and ow features such as the bore collapseprocess near the still water shoreline the mini collapse during the runup phase and the back wash bore inthe down rush phase are described in the case of a strong bore the evolution of the averaged turbulencekinetic energy tke over the swash zone consists of two phases in the region near the still water shoreline the production and the dissipation of tke are roughly in balance in the region farther landwards of the still water shoreline the tke decay rate is very close to that of homogeneous grid turbulence on the other hand in the case of a weak bore the bore collapse generated turbulence is con ned near the bottom boundarylayer and the tke decays at a much slower rate 2008 elsevier b v all rights reserved

swash aquifer interaction in the vicinity of the water table exit point on a sandy beach the coupling of sandy beach aquifers with the swash zone in the vicinity of the water table exit point is investigated through simultaneous measurements of the instantaneous shoreline swash front location pore pressures and the water table exit point the field observations reveal new insights into swash aquifer coupling not previously gleaned from measurements of pore pressure only in particular for the case where the exit point is seaward of the observation point the pore pressure response is correlated with the distance between the exit point and the shoreline in that when the distance is large the rate of pressure drop is fast and when the distance is small the rate decreases the observations expose limitations in a simple model describing exit point dynamics which is based only on the force balance on a particle of water at the sand surface and neglects subsurface pressures a new modified form of the model is shown to significantly improve the model data comparison through a parameterization of the effects of capillarity into the aquifer storage coefficient the model enables sufficiently accurate predictions of the exit point to determine when the swash uprush propagates over a saturated or a partially saturated sand surface potentially an important factor in the morphological evolution of the beach face observations of the shoreward propagation of the swash induced pore pressure waves ahead of the runup limit shows that the magnitude of the pressure fluctuation decays exponentially and that there is a linear increase in time lags behavior similar to that of tidally induced water table waves the location of the exit point and the intermittency of wave runup events is also shown to be significant in terms of the shore normal energy distribution seaward of the mean exit point location peak energies are small because of the saturated sand surface within the seepage face acting as a rigid lid and limiting pressure fluctuations landward of the mean exit point the peak energies grow before decreasing landward of the maximum shoreline position

geoelectrical signals of geologic and hydrologic processes in a fringing reef lagoon setting summary coastal groundwater may discharge into nearshore and offshore waters forced by terrestrial fluxes controlled by local geology and modulated by the hydrodynamics of littoral water we investigated the electrical signature of these features with a dense multiscale network of electrical resistivity tomography ert surveys in the muri lagoon of rarotonga cook islands the ert surveys spanned from onshore to 400 m into the lagoon and used standard electrodes on land and across the foreshore submerged electrodes in the shallow subtidal zone and floating electrodes towed throughout the reef lagoon by a boat ert surveys on land mapped a typical freshwater lens underlain by a saltwater wedge but with possible deviations from the classical model due to an adjacent tidal creek further inland ert surveys imaged a layer of lava flow deposits that is potentially a confining hydrogeologic unit this unit was used to constrain the expected electrical resistivity of these deposits below the lagoon ert surveys across the intertidal zone and into the lagoon indicated fresh groundwater and porewater salinity patterns consistent with previous small scale studies including the seaward extension of fresh groundwater pathways to the lagoon electrical resistivity er variations in the lagoon subsurface highlighted heterogeneities in the lagoon structure that may focus submarine groundwater discharge sgd through previously unknown buried lava flow deposits in the lagoon a transition to higher er values near the reef crest is consistent with the er signature of porosity reduction due to ongoing differential cementation of reef deposits across the lagoon the imaged coastal hydrostratigraphic heterogeneity may thus control terrestrial and marine porewater mixing support sgd and provide the pathways for groundwater and the materials it transports into the lagoon this hydrogeophysical investigation highlighted the spatial heterogeneity of submarine coastal geology and its hydrogeologic control in a reef lagoon setting but is likely to occur in many similar coastal settings ignoring geologic complexity can result in mischaracterization of sgd and other coastal groundwater processes at many spatial scales

fault scaling laws and the temporal evolution of fault systems abstract through an analysis of the temporal evolution of duplex fault systems this contribution shows that it is unlikely that all faults in a deformed area will conform to a single frequency size scaling relationship the development of a duplex leads to different size frequency relationships for the faults that compose the duplex and those confined to individual horses the faults that compose the duplex define segments with relatively steep stopes on a log n number of faults i e frequency vs log d displacement magnitude i e size plot faults within individual horses define segments with relatively shallow slopes on a log n vs log d plot the distinction between these two types of faults in a duplex is akin to the distinction between large active faults which cut the entire seismogenic layer and small active faults which do not extend across the seismogenic layer if as is often the case the faults that compose a duplex do not extend across the seismogenic layer the stepped nature of the resulting log n vs log d plot may make it particularly difficult to assess the contribution of these small faults to regional deformation since duplex geometries result in part from anisotropies present in deforming rocks the anisotropy present in nearly all crustal rocks will affect the size frequency relationship observed for systems of faults different parts of a deforming rock mass are likely to have different initial anisotropies combining data on fault systems from markedly different portions of a deforming region may then obscure the unique characteristics of the size frequency relationship in either area and may lead to inaccurate assessments of the relative contributions of small and large faults to regional fault accommodated strains

duplex structures and imbricate thrust systems geometry structural position and hydrocarbon potential duplexes and imbricate thrust systems form some of the most complex hydrocarbon traps in overthrust belts the geometry of a duplex is controlled by the ramp angle thgr and height hr the final spacing between adjacent thrusts a prime and the relative displacements on them d1 d2 for constant thgr and hr three different classes are recognized 1 independent ramp anticlines and hinterland sloping duplexes 2 true duplexes and 3 overlapping ramp anticlines imbricate thrust systems consist of several thrust faults each of which loses displacement upsection and eventually dies out by progressively transferring its displacement to a fold at its tip or by distributing it among several splays hybrid duplexes are ormed from systems of fault propagation folds that are subsequently carried over ramps so they have a more complex geometry and a greater structural relief these different types of thrust systems occur as outcrops and prospect scale structures and they define the regional structural styles of most fold and thrust belts second and third order duplexes and imbricate thrust systems occur in specific structural positions such as footwalls hanging walls and frontal zones of major thrust ramps and in cores of major anticlines several types of duplexes and imbricate thrust systems form important hydrocarbon traps examples include the system of independent anticlines of the turner valley and highwood oil and gas fields the hinterland sloping duplex consisting of the chestnut ridge sandy ridge system of the ben hur oil field the partly overlapping anticlines of the waterton and savanna creek gas fields and the completely overlapping anticlines of the rose hill oil field