radar interferometric mapping of deformation in the year after the landers earthquake although the 1992 landers california earthquake sequence occurred in an area well sampled by geodetic networks1 3 the postseismic deformation in the months following the earthquake has been measured at only 15 geodetic stations4 another shortcoming in the geodetic coverage occurs west of the primary rupture where the existing geodetic observations suggest but cannot resolve sympathetic slip on secondary faults1 such measurements which are needed to place the landers earthquake sequence in the context of a recurring seismic cycle in california can be obtained with the dense spatial coverage provided by satellite radar interferometry5 9 here we present radar maps of the surface deformation field which reveal features that would otherwise have been poorly sampled particularly if the earthquake had occurred in a less accessible area we see triggered slip at the level of several centimetres as far as 100 km from the primary rupture and can resolve the geodetic signal of at least one small magnitude 5 aftershock the amount of surface slip following the main shock is less than a decimetre and is consistent with an exponential decay time of several months for the postseismic deformation

a phase resolving cross shore sediment transport model for beach profile evolution abstract a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the mean undertow and the intra wave sediment concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone even for eroding beaches suggesting that other contributions should not be neglected the present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

coseismic crustal deformations of 1994 northridge california earthquake detected by interferometric jers 1 synthetic aperture radar coseismic deformations of the january 17 1994 northridge california earthquake are mapped using interferometric combination of synthetic aperture radar images acquired by the japanese earth resource satellite jers 1 on april 30 1993 and june 14 1994 we make an interferogram in a rectangular area with a size of 18 6 km n s by 29 9 km e w although coherence is not perfect in some areas fringes in flat and inhabited areas clearly show the coseismic movements to remove ambiguity of the fringes due to inaccurate orbital information we use a least squares adjustment to minimize the difference between the radar and the global positioning system gps measurements the difference between the radar and gps measurements is less than 3 5 cm the observed fringe patterns agree with a gps based theoretical fault model within 10 cm we also find a lobed pattern that suggests up to 20 cm of subsidence within a small area the results suggest that the l band 23 5 cm radar used by jers 1 is more robust to spatial and temporal decorrelation than the c band radar used by the ers 1 and radarsat satellites

cross shore mean flow in the surf zone abstract the seaward mean returnflow or undertow in the surf zone which compensates for the shoreward mass flux above the wave trough level is found to be driven by the force imbalance between the wave momentum flux on the one hand and the set up on the other hand in qualitative agreement with the model of dyhr nielsen and sorensen 1970 a model which quantifies this imbalance is shown to yield theoretical results in good accordance with experiments when the proper boundary conditions are accounted for

the 1994 northridge earthquake sequence in california seismological and tectonic aspects the m w 6 7 northridge earthquake occurred on january 17 1994 beneath the san fernando valley two seismicity clusters located 25 km to the south and 35 km to the north northwest preceded the mainshock by 7 days and 16 hours respectively the mainshock hypocenter was relatively deep at 19 km depth in the lower crust it had a thrust faulting focal mechanism with a rake of 100 on a fault plane dipping 35 to the south southwest and striking n75 w because the mainshock did not rupture the surface its association with surficial geological features remains difficult to resolve nonetheless its occurrence reemphasized the seismic hazard of concealed faults associated with the contractional deformation of the transverse ranges the northridge earthquake is part of the temporal increase in earthquake activity in the los angeles area since 1970 the mainshock was followed by an energetic aftershock sequence eight aftershocks of m 5 0 and 48 aftershocks of 4 m 5 occurred between january 17 and september 30 1994 the aftershocks extend over most of the western san fernando valley and santa susana mountains they form a diffuse spatial distribution around the mainshock rupture plane illuminating a previously unmapped thrust ramp extending from 7 10 km depth into the lower crust to a depth of 23 km no flattening of the aftershock distribution is observed near its bottom at shallow depths above 7 10 km the thrust ramp is topped by a dense distribution of aftershock hypocenters bounded by some of the surficial faults the dip of the ramp increases from east to west the west side of the aftershock zoae is characterized by a dense steeply dipping and north northeast striking planar cluster of aftershocks that exhibited mostly thrust faulting these events coincided with the gillibrand canyon lateral ramp along the east side of the aftershock zone the aftershocks also exhibited primarily thrust faulting focal mechanisms the focal mechanisms of the aftershocks were dominated by thrust faulting in the large aftershocks with some strike slip and normal faulting in the smaller aftershocks the 1971 san fernando and the 1994 northridge earthquakes ruptured partially abutting fault surfaces on opposite sides of a ridge both earthquakes accommodated north south contractional deformation of the transverse ranges the two earthquakes differ primarily in the dip direction of the faults and the depth of faulting the 1971 north northeast trend of left lateral faulting chatsworth trend was not activated in 1994

satellite radar interferometric map of the coseismic deformation field of the m 6 1 eureka valley california earthquake of may 17 1993 interferometric combination of pairs of synthetic aperture radar sar images acquired by the ers 1 satellite before and after the eureka valley california earthquake of may 17 1993 maps the coseismic deformation field the fringes corresponding to contours of equal change in satellite to ground distance can be enhanced by forming the sum of two of such interferograms with altitudes of ambiguity roughly equal in magnitude but opposite in sign the resulting composite interferogram reveals some 10 cm of change in range indicating a coseismic deepening of the eureka valley graben after unwrapping filtering and decimation the range changes are used to estimate the centroid and focal mechanism these estimates indicate normal faulting on a rupture patch compatible with the distribution of aftershocks and mapped quaternary faults the change in elevation produced by this earthquake resembles the current topography scaled by a factor of 20 000

suspended sand concentration models under breaking waves evaluation of new and existing formulations abstract a total of 7 reference concentration c0 models 6 existing and 1 newly proposed were validated against 119 test cases from 4 recently published datasets collected under the lip crosstex sandt pro and sinbad experimental studies these models were evaluated for performance in different cross shore regions the shoaling zone breaking outer surf zone and inner surf zone under regular and irregular breaking wave conditions in almost all existing c0 models substantial under prediction was found particularly around the wave plunging point point at which breaking wave plunges and surface generated turbulent kinetic energy tke is injected into the water column where strong localised increases in c0 were observed this strong increase in concentration was attributed to the large scale breaking generated turbulent vortices invading the wave bottom boundary layer wbbl and entraining dense clouds of sediment near the plunging point models that were directly or indirectly driven by local wave climate such as the local wave height h breaker height hb or local water depth d were found to perform quite poorly in the breaking region under regular and irregular plunging breaker waves formulations that related c0 to the sand pickup rate i e depending on exerted bed shear exceeding critical bed shear for entrainment were adept in regions unaffected by external breaking induced tke e g the shoaling zone but could not account for the high levels of concentration observed at the plunging point this is because these formulations were based on the implicit assumption that sediment entrainment is only induced by the local tke generated by bed shear not taking surface generated breaking induced tke into account this assumption was addressed in more recent studies by including breaking induced tke into sediment pickup rate or reference concentration formulations though latest studies have shown promising relationships between near bed tke kb and reference concentration sediment pickup such formulations also face inherent limitations these formulations are highly dependent on the accuracy of measured or modelled kb and are also sensitive to the magnitude of kb for example the magnitude of measured kb was found to vary by a factor of 1 1 1 3 between regular and irregular wave conditions with kb being smaller under irregular wave conditions this resulted in varied performance between datasets in kb driven reference concentration formulations the froude scaled tke produced smaller deviations in magnitude of tke between datasets suggesting that it may be a more suitable driving parameter for reference concentration models than kb a new reference concentration model l19 was empirically derived from an inverse relationship observed between d and c0 and from the roller energy dissipation rate the newly proposed l19 model shows good agreement with measured c0 with rmse ranging between 0 36 and 1 79 kg m3 over the different datasets in regular and irregular wave conditions even at the plunging point where concentration is highest the modified concentration profile c z equation also performs well generally capturing the vertical concentration profile accurately throughout the whole water column

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

observation of undertow and turbulence in a laboratory surf zone abstract undertow and turbulence in the surf zone have been studied in a wave flume for a spilling breaker and a plunging breaker fluid velocities across a 1 on 35 sloped false bottom were measured using a fiber optic laser doppler anemometer and wave decay and set up were measured using a capacitance wave gage the characteristics of mean flow and turbulence in spilling versus plunging breakers were studied the mean flow is the organized wave induced flow defined as the phase average of the instantaneous velocity while the turbulence is taken as the deviations from the phase average it was found that under the plunging breaker turbulence levels are much higher and vertical variations of undertow and turbulence intensity are much smaller in comparison with the spilling breaker it was also found that turbulent kinetic energy is transported seaward under the spilling breaker and landward under the plunging breaker by the mean flow the study indicates that there are fundamental differences in the dynamics of turbulence between spilling and plunging breakers which can be related to the processes of wave breaking and turbulence production it is suggested that the types of beach profile produced by storm and swell waves may be the results of different relationships between mean flow and turbulence in these waves

transition zone width and implications for modeling surfzone hydrodynamics the surfzone associated with a wave breaking on a plane slope may be subdivided into three regions the transition zone the inner zone and the swash zone the transition zone is the region just shoreward of the point of wave breaking and is characterised by rapid wave decay and also by constant wave setdown and thus constant radiation stress in this paper an empirical expression for the width of this zone is developed from monochromatic wave data two techniques are proposed for the consideration of this phenomenon in the numerical modelling of surfzone hydrodynamics for random waves the implications of a zone of nearly constant radiation stress inside the breakpoint are examined with respect to wave induced current generation both cross shore and longshore and sediment transport prediction comparisons are made to both field and laboratory data from plane and undulating profiles

quasi 3d modelling of nearshore currents abstract existing concepts of wave induced nearshore current models in the cross shore vertical plane 2dv and depth integrated 2dh are combined to a quasi 3d mathematical model this combination is tested for reproducing correct results in 2dv and 2dh situations the importance of the various contributions to the wave induced secondary circulation in the vertical plane is investigated for realistic parameter ranges which leads to the conclusion that both the non breaking and the breaking fraction of a random wave field in the surf zone generate important secondary currents additional computations show the relevance of a 3d approach of nearshore currents even in seemingly simple situations like a plane sloping beach with obliquely incident waves

vertical structure of mean cross shore currents across a barred surf zone mean cross shore currents observed across a barred surf zone are compared to model predictions the model is based on a simplified momentum balance with a turbulent boundary layer at the bed turbulent exchange is parameterized by an eddy viscosity formulation with the eddy viscosity a independent of time and the vertical coordinate mean currents result from gradients due to wave breaking and shoaling and the presence of a mean setup of the free surface descriptions of the wave field are provided by the wave transformation model of thornton and guza 1983 the wave transformation model adequately reproduces the observed wave heights across the surf zone the mean current model successfully reproduces the observed cross shore flows both observations and predictions show predominantly offshore flow with onshore flow restricted to a relatively thin surface layer successful application of the mean flow model requires an eddy viscosity which varies horizontally across the surf zone attempts are made to parameterize this variation with some success the data does not discriminate between alternative parameterizations proposed the overall variability in eddy viscosity suggested by the model fitting should be resolvable by field measurements of the turbulent stresses consistent shortcomings of the parameterizations and the overall modeling effort suggest avenues for further development and data collection

the oak ridge fault system and the 1994 northridge earthquake the 17 january 1994 northridge earthquake moment magnitude m w 6 7 in the san fernando valley in southern california illuminated a hitherto unrecognized blind reverse fault with a moderate southward dip 1 this fault lies beneath the active north dipping santa susana fault system and uplifted both the footwall and the hanging wall of the santa susana fault during the earthquake1 here we argue that footwall uplift on the santa susana fault before the earthquake could have been used to identify the northridge blind thrust as an active fault moreover we propose that the northridge earthquake occurred on a continuation of the oak ridge fault system which reaches the surface in the ventura basin to the west slip rates on the western part of this fault system 2 3 are nearly three times larger than on the northridge blind thrust 4 increasing the probability of a n or t bridge sized earthquake in the heavily populated ventura basin

calibrating interferometric synthetic aperture radar insar images with regional gps network atmosphere models summary interferometric synthetic aperture radar insar technology provides a valuable tool for obtaining earth surface deformation and topography at high spatial resolution for crustal deformation studies similar to global positioning system gps insar measurements are affected by the earth s ionospheric and tropospheric layers as the electromagnetic signals significantly refract while propagating through the different layers while gps signals propagating through the neutral atmosphere are affected primarily by the distribution pressure and temperature of atmospheric gases including water vapour the propagation through the ionosphere is mainly affectedbythenumberoffreeelectronsalongthesignalpath here wepresenttheuseofdense regional gps networks for extracting tropospheric zenith delays and ionospheric total electron content tec maps in order to reduce the noise levels in insar images the results show significant reduction in the root mean square rms values when simultaneously combining the two corrections both at short time periods where no surface deformation is expected and at longer periods where imaging of localized subsidence and fault creep is enhanced

coseismic deformation field of the m 6 7 northridge california earthquake of january 17 1994 recorded by two radar satellites using interferometry interferometric combination of pairs of synthetic aperture radar sar images acquired by the ers 1 and jers 1 satellites before and after the northridge california earthquake of january 17 1994 provide two maps of the coseismic deformation field the fringes corresponding to contours of equal change in satellite to ground distance show the coseismic displacement of the mainshock the fringe patterns remain clear for over a year even in urban areas with structural damage elastic dislocation fault models fitting the two radar interferograms are substantially equivalent despite the different radar wavelengths 56 and 235 mm for ers 1 and jers 1 respectively a single fault model based on surveying measurements using the global positioning system gps fails to account for parts of the fringe patterns observed by radar satellite particularly the effects of several aftershocks and localized ground motion

a quasi 3d phase resolving hydrodynamic and sediment transport model a two dimensional phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the two dimensional sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone two hydrodynamic modules are developed for the calculation of the vertical variation of the eddy viscosity and the currents the intra wave sediment concentrations and sediment transport rates are also calculated the model was verified against several test cases and a sensitivity analysis was performed both hydrodynamic modules produced close results for the mean currents the two models also produced close results for the sediment transport rates with larger differences observed at the locations with a stronger undertow the model results showed that for irregular breaking waves the mean sediment concentration cannot be calculated directly from the mean eddy viscosity

analysis of surf zone turbulence measurements of turbulent kinetic energy k under surf zone waves are analyzed to show how k varies over depth between breaker point and shoreline and how k depends on the beach slope it is found that the variation of k over depth is remarkably weak large values being measured a few percent of the depth above the bottom a simple model for the dissipation mechanism makes it possible to derive an empirical formula for the time averaged k that accurately describes all the data considered reliable

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

an energetics bedload model for a plane sloping beach local transport bagnold s energetics based sediment transport model for streams is used as a basis for the development of a model for the time varying transport of bedload over a plane sloping bed the sediment transport vector is found to consist of two components the velocity induced transport directed parallel to the instantaneous velocity vector and the gravity induced transport vector directed downslope the model is applied to the case of sediment transport within the surf zone for the separate cases of weak and strong longshore currents relative to the wave bore oscillatory water velocity the results suggest the bagnold s oscillatory sediment transport model which forms the basis for a number of longshore sediment transport models is only correct for the special case of weak longshore currents and near normal incident waves for an artibrary strength longshore current v and a local incident wave angle a the longshore transport rate is found to be proportional to sina v 1 sin sup 2 a v sup 3 where u is the wave induced oscillatory water velocity the model also predicts the onshore offshore sediment rate for weak longshore currents and near normal incident waves the predicted equilibrium beach slope is equal to tanf strong longshore currents and or significant local wave angle conditions however cause amore change in this equilibrium beach slope less authors bailard j a inman d l publication date 1981 03 20 osti identifier 6767919 resource type journal article resource relation journal name j geophys res united states journal volume 86 c3 research org scripps institution of oceanography university of california la jolla california 92093 country of publication united states language english subject 58 geosciences shores sedimentation coastal waters gravitation sediments silt velocity water currents currents surface waters 580500 oceanography 1980 1989

the magnitude 6 7 northridge california earthquake of january 17 1994 the most costly american earthquake since 1906 struck los angeles on 17 january 1994 the magnitude 6 7 northridge earthquake resulted from more than 3 meters of reverse slip on a 1 5 kilometer long south dipping thrust fault that raised the santa susana mountains by as much as 70 centimeters the fault appears to be truncated by the fault that broke in the 1971 san fernando earthquake at a depth of 8 kilometers of these two events the northridge earthquake caused many times more damage primarily because its causative fault is directly under the city many types of structures were damaged but the fracture of welds in steel frame buildings was the greatest surprise the northridge earthquake emphasizes the hazard posed to los angeles by concealed thrust faults and the potential for strong ground shaking in moderate earthquakes

surface displacement of the 17 may 1993 eureka valley california earthquake observed by sar interferometry satellite synthetic aperture radar sar interferometry shows that the magnitude 6 1 eureka valley earthquake of 17 may 1993 produced an elongated subsidence basin oriented north northwest parallel to the trend defined by the aftershock distribution whereas the source mechanism of the earthquake implies a north northeast striking normal fault the 3 millimeter accuracy of the radar observed displacement map over short spatial scales allowed identification of the main surface rupture associated with the event these observations suggest that the rupture began at depth and propagated diagonally upward and southward on a west dipping north northeast fault plane reactivating the largest escarpment in the saline range

petrology mineral chemistry and sr nd pb isotopic compositions of granitoids in the central menderes metamorphic core complex constraints on the evolution of aegean lithosphere slab abstract plutonic associations in the central menderes metamorphic core complex are suitable rocks in order to understand the magma forming processes in extended terrains syn extensional salihli and turgutlu granitoids have granodioritic composition and contain monzonitic and monzodioritic microgranular enclaves they are transitional metaluminous peraluminous and high k calc alkaline in character and are located on i and s type transition salihli and turgutlu granodiorites are geochemically similar to each other while their microgranular enclave chemistry is in contrast with low sio2 and high mg values mineral chemistry data from granodiorites and mafic microgranular enclaves confirm their shallow emplacement at about 7 km geochemical modelling suggests that syn extensional granitoids were derived from the mixing of mantle and lower crustal components which were finally modified by a significant amount of upper crustal contamination and fractional crystallization processes at shallow crustal levels early middle miocene syn extensional granitoids across the aegean region form a magmatic belt associated with roll back of the aegean lithosphere slab roll back induced magmatism together with ductile deformation in western turkey ceased after cooling of the salihli granodiorites at 12 2 ma but core complex related magmatism was continuous in the cycladic metamorphic core complex during late miocene and was followed by an active arc volcanism in the southern aegean such abrupt change from ductile to brittle mode of extension in western turkey can be explained by opening of a slab window on the aegean lithosphere slab which would lead to upwelling of fertile subslab asthenospheric mantle forming transitional and finally oib type basalts

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

suspended sediment concentrations under waves abstract a predictive formula is derived for calculation of the magnitude of time averaged suspended sediment concentrations under waves by taking into account the effect of flow contraction near ripple crests the formula applies equally well for rippled beds and sheet flow conditions the formula is in qualitative agreement with the bed load flux formula of madsen and grant 1976

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

cross shore hydrodynamics and profile response modeling abstract the issue of hydrodynamics causing cross shore sediment transport is examined analytically undertow is represented based on recent experimental evidence a relatively complete physicsbased cross shore sediment transport model including mechanisms for suspended and bedload transport is developed with the capacity for onshore and offshore transport effects of turbulence momentum transfer and augmented volumetric flux in the surf zone horizontal wave asymmetry bottom boundary layer intermittent suspension overtopping water levels and gravity are included the model is tested against data from laboratory experiments involving regular and irregular waves and overtopping conditions it is fairly successful in predicting prominent patterns of erosion and deposition sediment overwash and longshore bars the model lacks long term stability

analysis of submerged bar nourishment strategies in a wave dominated environment using a 2dv process based model the present study aims to analyze the effects of different submerged bars nourishment strategies using a 2dv process based morphodynamical model a two barred beach profile typical of the french mediterranean micro tidal storm dominated coastline is chosen as a reference profile two different kinds of modified beach profiles are considered i only the outer bar is nourished the inner bar being unchanged ii both bars are nourished three typical wave forcing regimes are considered the behavior of the natural profile is first investigated under the 3 wave forcing regimes then the behavior of the various nourished profiles is analyzed in terms of wave dynamics and bars behavior on the basis of the model results the outer bar only nourishment strategy appears to be preferable

estimation of an earthquake focal mechanism from a satellite radar interferogram application to the december 4 1992 landers aftershock using the interferometric fringes generated by the phase difference between a pair of synthetic aperture radar sar images acquired by the ers 1 satellite we estimate the focal mechanism of a small shallow thrust earthquake the inversion procedure is an iterative linearized least squares algorithm based on a standard elastic dislocation formulation for coseismic displacements our preferred estimate is a thrust focal mechanism with its hypocenter at n34 35 0 4 km w116 91 0 2 km 2 6 0 3 km depth on a plane dipping southward beneath the san bernardino mountains with a moment magnitude mw of 5 4 the strike dip and rake are n106 e 7 28 4 and 93 4 respectively on a fault 3 1 0 5 km wide and 2 9 0 4 km long the precision of these estimates is competitive with seismological determinations

suspended sediment transport around a large scale laboratory breaker bar this paper presents novel insights into suspended sediment concentrations and fluxes under a large scale laboratory plunging wave measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar covering the complete breaking region from shoaling to inner surf zone with particular high resolution near the bed using an acoustic concentration and velocity profiler wave breaking evidently affects sediment pick up rates which increase by an order of magnitude from shoaling to breaking zone time averaged reference concentrations correlate poorly with periodic and time averaged near bed velocities but correlate significantly with near bed time averaged turbulent kinetic energy the net depth integrated suspended transport is offshore directed and primarily attributed to current related fluxes undertow at outer flow elevations i e above the wave bottom boundary layer the wave related suspended transport is onshore directed and is generally confined to the wave bottom boundary layer cross shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick up and deposition and of cross shore sediment advection suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion leading to local intra wave concentration changes at locations between the breaker bar crest and bar trough intra wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer sediment is entrained in the bar trough during the wave trough phase almost instantly advected offshore and deposited near the bar crest during the wave crest phase finally these results are used to suggest improvements for suspended sediment transport models

analysis of some key parametrizations in a beach profile morphodynamical model abstract a numerical process based model to forecast beach profile morphodynamics has been developed in the present paper an analysis of various modelling approaches and key parametrizations involved in the estimation of the wave driven current and the suspended sediment concentration is carried out several resolution techniques for the 1dv horizontal i e in the x direction perpendicular to coastline momentum equation governing the mean horizontal velocity mhv are analysed in the first kind of techniques the mean horizontal velocity is computed from the momentum equation whereas the mean water level mwl is computed using a parametrization of the depth averaged momentum equation two boundary or integral conditions are thus needed in the second kind both mean horizontal velocity and mean water level gradient in the x direction are the unknowns of the momentum equation thus three boundary or integral conditions are needed various additional conditions are discussed we show that using a technique of the first kind is equivalent to imposing the difference between the surface and the bottom shear stresses in the 1d vertical equation both techniques lead to results that are in good agreement with the delta flume experimental data provided the stokes drift flow discharge is imposed as an additional condition the influence of the breaking roller model and of the turbulent viscosity parametrization are also analysed suspended sediment transport by the mean current and wave induced bedload transport are taken into account in the sediment flux three turbulent diffusivity parametrizations are compared for suspended sediment concentration estimations a linear profile for the turbulent diffusivity taking into account the wave bottom shear stress and the surface wave breaking turbulence production is shown to give the best results using experimental data we put forward the poor estimation of the bottom sediment concentration given by the three implemented parametrizations we thus propose a new parametrization relying on a shields parameter based on the breaking roller induced surface shear stress using this new parametrization the bottom profile used in the tests keeps its two bars which disappear otherwise however the morphodynamical model still overestimates the bars offshore motion a bias already observed in other models

the interaction between the undertow and the boundary layer flow on a beach the theoretical result for undertow in a surf zone found by svendsen 1984a is combined with a boundary layer solution at the bottom and it is shown that in this boundary layer the eddy viscosity is small relative to that produced by the breaking the proper eddy viscosity t between the surface and the bottom boundary layer is determined by comparison with measurements which leads to quite accurate reproduction of the velocity profiles the model also predicts the mean flow in the boundary layer and the mean bottom shear stress and the results are analyzed for sensitivity to inaccuracies in the basic assumptions