working models for spatial distribution and level of mars seismicity 1 we present synthetic catalogs of mars quakes intended to be used for performance assessments of future seismic networks on the planet we have compiled a new inventory of compressional and extensional tectonic faults for the planet mars comprising 8500 faults with a total length of 680 000 km the faults were mapped on the basis of mars orbiting laser altimeter mola shaded relief hence we expect to have assembled a homogeneous data set not biased by illumination and viewing conditions of image data updated models of martian crater statistics and geological maps were used to assign new maximum ages to all faults on the basis of the fault catalog spatial distributions of seismicity were simulated using assumptions on the available annual seismic moment budget the moment frequency relationship and a relation between rupture length and released moment we have constructed five different models of martian seismicity predicting an annual moment release between 3 42 1016 nm and 4 78 1018 nm and up to 572 events with magnitudes greater than 4 per year as upper limit end member case most events are expected on the tharsis shield but minor seismic centers are expected south of hellas and north of utopia planitia

core formation and geophysical properties of mars abstract the chemical and physical properties of the interiors of terrestrial planets are largely determined during their formation and differentiation modeling a planet s formation provides important insights into the properties of its core and mantle and conversely knowledge of those properties may constrain formational narratives here we present a multi stage model of martian core formation in which we calculate core mantle equilibration using parameterizations from high pressure temperature metal silicate partitioning experiments we account for changing core mantle boundary cmb conditions composition dependent partitioning and partial equilibration of metal and silicate and we evolve oxygen fugacity fo2 self consistently the model successfully reproduces published meteorite based estimates of most elemental abundances in the bulk silicate mars which can be used to estimate core formation conditions and core composition this composition implies that the primordial material that formed mars was significantly more oxidized 0 9 1 4 log units below the iron wustite buffer than that of the earth and that core mantle equilibration in mars occurred at 42 60 of the evolving cmb pressure on average at least 84 of accreted metal and at least 40 of the mantle were equilibrated in each impact a significantly higher degree of metal equilibration than previously reported for the earth in agreement with previous studies the modeled martian core is rich in sulfur 18 19 wt with less than one weight percent o and negligible si we have used these core and mantle compositions to produce physical models of the present day martian interior and evaluate the sensitivity of core radius to crustal thickness mantle temperature core composition core temperature and density of the core alloy trade offs in how these properties affect observable physical parameters like planetary mass radius moment of inertia and tidal love number k 2 define a range of likely core radii 1620 1870 km seismic velocity profiles for several combinations of model parameters have been used to predict seismic body wave travel times and planetary normal mode frequencies these results may be compared to forthcoming martian seismic data to further constrain core formation conditions and geophysical properties

mars interior structure and excitation of free oscillations based on available chemical models of the planet philos trans r soc london 349 1994 285 supply and loss of volatile constituents during the accretion of terrestrial planets in s k attreya j b pollack m s matthews eds origin and evolution of planetary and satellite atmospheres univ arizona press pp 268 288 icarus 126 1997 373 phys earth planet inter 112 1999 43 space sci rev 92 2000 34 a new set of global models of the martian interior has been constructed a model comprises four submodels a model of the outer porous layer a model of the crust a model of the mantle and a model of the core the first 10 11 km layer is considered as an averaged transition from regolith to consolidated rock the mineral composition of the crustal basaltic rock varies with depth because of the gabbro eclogite phase transition as a starting point for mantle modeling the experimental data obtained by bertka and fei j geophys res 102 1997 525 earth planet sci lett 157 1998 79 along the areotherm have been used iron content of the mantle being varied the measured or estimated up to now elastic properties for a set of mantle minerals are used seismic velocities determined from new high p t data on elastic properties are 2 3 lower than the velocities calculated earlier new high p t measurements of the density of fe fe fes and feh enable us to refine the core model taking into account available chemical models and the fact that noticeable amount of hydrogen could enter the martian core during its formation solar syst res 30 1996 456 such parameters as a ferric number of the mantle fe sulfur and hydrogen content in the core are varied the following tendency is seen the presence of hydrogen leads to the increase of the fe si ratio and decreases fe in the mantle due to the increase of the core radius the higher sulfur and hydrogen content in the core and the smaller mantle fe the less likely a perovskite layer exists the modeling shows that to obtain the fe si ratio up to the chondrite ratio of 1 71 more than 50 mol of hydrogen should be incorporated into the core in the second part of the paper based on the available estimates of the martian seismic activity and the sensitivity of current instruments the amplitudes for different types of free oscillations have been estimated it is found down to what depth the normal modes can sound the planetary interiors a marsquake with a seismic moment of 10 25 dyn cm is required for spheroidal oscillations with 17 to be detected these spheroidal modes are capable sounding the outer layers of mars down to a depth of 700 800 km

hindered settling of sand grains the sedimentation rate of sand grains in the hindered settling regime has been considered to assess particle shape effects the behaviour of various particulate systems involving sand has been compared with the widely used richardson zaki expression the general form of the expression is found to hold in as much as remaining as a suitable means to describe the hindered settling of irregular particles the sedimentation exponent n in the richardson zaki expression is found to be significantly larger for natural sand grains than for regular particles the hindered settling effect is therefore greater leading to lower concentration gradients than expected the effect becomes more pronounced with increasing particle irregularity at concentrations around 0 4 the hindered settling velocity of fine and medium natural sands reduces to about 70 of the value predicted using existing empirical expressions for n using appropriate expressions for the fluidization velocity and the clear water settling velocity a simple method is discussed to evaluate the sedimentation exponent and to determine the hindered settling effect for sands of various shapes

vertical fluxes of sediment in oscillatory sheet flow time series of vertical sediment fluxes are derived from concentration time series in sheet flow under waves while the concentrations c z t vary very little with time for z 10d50 the measured vertical sediment fluxes qzs z t vary strongly with time in this vertical band and their time variation follows to some extent the variation of the grain roughness shields parameter 2 5 t thus sediment distribution models based on the pickup function boundary condition are in some qualitative agreement with the measurements however the pickup function models are only able to model the upward bursts of sediment during the accelerating phases of the flow they are so far unable to model the following strong downward sediment fluxes which are observed during the periods of flow deceleration classical pickup functions which essentially depend on the shields parameter are also incapable of modelling the secondary entrainment fluxes which sometimes occur at free stream velocity reversal the measured vertical fluxes indicate that the effective sediment settling velocity in the high 0 3 c z t 0 4 concentration area is typically only a few percent of the clear water settling velocity while the measurements of richardson and jeronimo chem eng sci 34 1979 1419 from a different physical setting lead to estimates of the order 20 the data does not support gradient diffusion as a model for sediment entrainment from the bed that is detailed modelling of the observed near bed fluxes would require diffusivities that go negative during periods of flow deceleration an observed general trend for concentration variability to increase with elevation close to the bed is also irreconcilable with diffusion models driven by a bottom boundary condition

numerical models of martian mantle evolution induced by magmatism and solid state convection beneath stagnant lithosphere 1 numerical models of magmatism in a convecting mantle are presented to understand martian mantle evolution the viscosity is strongly temperature dependent and the lithosphere is stagnant magmatism is modeled as a permeable flow of basaltic magma generated by decompression melting when the initial mantle temperature is sufficiently high a magma ocean develops to generate a thick basaltic crust and create a compositionally layered mantle the upper layer of the mantle consists of compositionally buoyant residue of the basaltic crust while the lower layer consists of compositionally denser materials that are not as depleted in the basaltic component hot plumes grow from the lower layer making it thinner with time by erosion the hot plumes also induce magmatism which extracts heat producing elements hpes from the mantle the hpe extraction regulates plume magmatism activity and controls the duration of plume magmatism plume magmatism also keeps the mantle temperature below the solidus by efficiently extracting heat as soon as the mantle temperature exceeds the solidus the martian mantle is likely to have evolved as a relaxation from a compositionally layered state formed by the magma ocean and plume magmatism has probably played a crucial role in the relaxation process

asymmetric thermal evolution of the moon 1 the moon possesses a clear dichotomy in geological processes between the nearside and farside hemispheres the most pronounced expressions of this dichotomy are the strong concentration of radioactive heat sources on the nearside in a region known as the procellarum kreep terrane pkt and the mare basaltic lava flows that erupted in or adjacent to this terrane we model the thermochemical evolution of the moon using a 3 d spherical thermochemical convection code in order to assess the consequences of a layer enriched in heat sources below the pkt on the moon s global evolution we find that in addition to localizing most of the melt production on the nearside such an enriched concentration of heat sources in the pkt crust has an influence down to the core mantle boundary and leaves a present day temperature anomaly within the nearside mantle moderate gravitational and topographic anomalies that are predicted in the pkt but not observed may be masked either by crustal thinning or gravitational anomalies from dense material in the underlying mantle our models also predict crystallization of an inner core for sulfur concentrations less than 6 wt

estimates of seismic activity in the cerberus fossae region of mars 1 the 2016 nasa insight lander is the first planetary mission designed to study the deep interior of mars insight s seismic experiment for interior structure seis package will quantify global and regional seismic activity and determine parameters like core properties mantle composition and martian lithospheric thickness an improved understanding of the location magnitude and frequency of potential seismic sources is essential for optimization of instrument design sampling strategy and interpretation of mission data we focus on forecasting seismic activity for the cerberus fossae of the elysium planitia chosen for their proximity to the proposed landing site and their recent formation and assuming these are active tectonic grabens the minimum age we determine for the units around the fossae using context camera and high resolution imaging science experiment imagery for crater density surveying is 10 ma placing them in the late amazonian we are able to determine the rate of motion from measurements of observed throw assuming that the faults remain active digital terrain models made from stereo image pairs from the high resolution stereo camera hrsc are used to determine the maximum throw on four graben systems using these measured throws to estimate a length averaged slip and assuming an inferred slip rate from surface age we estimate an annual moment release of 1 58 1 03 2 35 1017nm from this we calculate an annual size frequency distribution of events using the gutenberg richter relationship we estimate that between 1 5 100and 1 9 105events per year will have an amplitude greater than the peak band noise and so will be detectable at the insight landing site

ferrous oxide in mercury s crust and mantle mercury has widespread plains deposits proposed to be volcanic in origin in a mariner 10 color derived parameter image sensitive to feo and maturity these volcanic plains have a value equivalent to or slightly elevated above the hemispheric average thus implying feo equivalent to or slightly less than the hemispheric average 3 wt feo since feo has a solid liquid distribution coefficient 1 during partial melting we estimate the mantle of mercury to have an feo abundance equal to the lava flows this is consistent with models that predict mercury was assembled from planetesimals formed near the planet s current position this new estimate of mercury s bulk feo 3 wt is consistent with data for the other terrestrial planets that suggest there was a radial gradient in feo in the solar nebula

hindered settling of silt abstractsediment particles smaller than 64 m with a noncohesive base mineral are referred to as silt the settling velocity of suspended sediment decreases with increasing concentration due to hindered settling effects compared with clay and sand hindered settling of silt is poorly documented and understood a formulation is proposed for the hindered settling of silt water mixtures derived from physical reasoning the effect of silt on the mixture s viscosity is addressed in particular the formulation compares favorably with laboratory experiments on the settling of silt sized sediment this study shows that effective settling velocities can be derived from a single concentration time series measured within the settling mixture provided that the sediment is initially homogeneously distributed

sediment pick up functions experimental research has been performed to determine the sediment pick up by a uniform flow without initial sediment load a sediment lift was designed by which the sediment particles were moved upwards at a constant rate through a circular opening in the flume bottom five types of bed material sand have been used with d d5 d0 values in the range 130 1500 m the mean flow velocities were in the range 9 5 1 0 m s the experimental results have been used to derive an empirical pick up function the results have also been used to evaluate several existing pick up functions finally the proposed empirical pick up function has been applied to predict the bed load and suspended load transport in the latter application the proposed function has been used as a bed boundary condition in a mathematical model for suspended sediment transport

internal structure and early thermal evolution of mars from mars global surveyor topography and gravity topography and gravity measured by the mars global surveyor have enabled determination of the global crust and upper mantle structure of mars the planet displays two distinct crustal zones that do not correlate globally with the geologic dichotomy a region of crust that thins progressively from south to north and encompasses much of the southern highlands and tharsis province and a region of approximately uniform crustal thickness that includes the northern lowlands and arabia terra the strength of the lithosphere beneath the ancient southern highlands suggests that the northern hemisphere was a locus of high heat flow early in martian history the thickness of the elastic lithosphere increases with time of loading in the northern plains and tharsis the northern lowlands contain structures interpreted as large buried channels that are consistent with northward transport of water and sediment to the lowlands before the end of northern hemisphere resurfacing

the current martian cratering rate abstract the discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at mars we use a subset of 44 of these new craters that were imaged before and after impact by mars reconnaissance orbiter s context camera a thoroughly searched data set that minimizes biases from variable image resolutions we find the current impact rate is 1 65 10 6 craters with an effective diameter 3 9 m km2 yr with a differential slope power law exponent of 2 45 0 36 this results in model ages that are factors of three to five below the hartmann hartmann w k 2005 icarus 174 294 320 and neukum et al neukum g ivanov b a hartmann w k 2001 space sci rev 96 55 86 ivanov ivanov b a 2001 space sci rev 96 87 104 model production functions where they overlap in diameter the best fit production function we measure has a shallower slope than model functions at these sizes but model function slopes are within the statistical errors more than half of the impacts in this size range form clusters which is another reason to use caution when estimating surface ages using craters smaller than 50 m in diameter

linkage between turbulent kinetic energy waves and suspended sediment concentrations in the nearshore zone abstract knowledge about the tradeoffs among turbulent kinetic energy tke waves and suspended sediment concentrations sscs in the nearshore zone is relevant for understanding beach morphodynamics at different temporal and spatial scales a field measurement lasting for nearly three tidal cycles was conducted to holistically discern couplings between tke waves and sscs with further evaluation of the relative significance of tke and waves on sscs under various wave conditions over a meso macro tidal beach yintan to the north of beibu gulf china the results showed a dramatic increase in wave groupiness intensity from the shoaling wave condition to the breaking wave condition and a clear decrease further into the surf bore condition the near bed tkes under the surf bore condition were an order of magnitude larger than those under the breaking and shoaling wave conditions at the measurement position the averaged sscs in the near bed approximately 10 cm under the surf bore condition were 1 5 and 4 5 times larger than those under breaking and shoaling wave conditions respectively the variations in relative wave height were a decisive indicator for the differences in tke intensities among different wave conditions while the occurrence of peak tkes at the wave front within the intrawave cycle was associated with flow acceleration regardless of wave conditions mean sscs were well correlated with waves in terms of both incident wave scale and wave group scale which was limited to the shoaling wave condition and the occurrence of near bed intrawave peak sscs was always related to the offshore wave phase further tke contributed more effectively to sediment suspension at the wave group scale than at the incident wave scale especially under broken wave condition among the hydrodynamic factors tke played the most important role in the variations in sscs for all wave conditions flow acceleration served as the second most important factor under the broken wave condition while wave group single wave and advection were equivalent and less important factors for sscs

sediment transport in oscillatory sheet flow motivated by an interest in high rates of sediment transport an experimental investigation was conducted to examine sediment motion in conditions of intense sediment transport fluid velocity and sediment concentration were measured simultaneously in a sheet flow regime generated in a u shaped oscillatory water tunnel for two types of noncohesive sediments a probe was developed to measure the instantaneous variations in sediment concentration based on the electrical conductivity of the fluid grain mixture unlike previous concentration devices this probe is nonintrusive and is capable of measuring a wide range of sediment concentrations from extremely dense concentrations within the bed to low concentration suspended load well above the moving layer of sediment horizontal fluid velocities were measured simultaneously using laser doppler anemometry in backscatter mode the sediment concentration measurements provide a comprehensive data set for sediment transport in sheet flow and near sheet flow regimes the temporal variation of sediment transport over the half cycle of oscillation was examined most of the sediment was transported within the moving bed layer with the total transport occurring between the stationary bed height and a distance about twice the thickness of the moving bed layer the temporal variation in sediment transport was found to be proportional to cos t the magnitude of the sediment transport increased with increasing bottom shear stress fluid velocity and sediment concentration measurements were used to calculate instantaneous and mean rates of sediment transport which were compared with predictions from existing models

field observations of turbulence sand suspension and cross shore transport under spilling and plunging breakers measurements of wave orbital velocity near bed turbulence levels and sediment suspension were obtained under plunging and spilling breakers in the outer surf zone on the beach at vejers denmark for the same range of relative wave heights and indicators of wave nonlinearity we observed significantly larger suspended sediment concentrations and onshore directed rates of suspended sediment transport under long period plunging breakers compared to short period spilling breakers this is consistent with the long held understanding that for a given beach slope onshore transport and beach accretion are associated with longer period waves and offshore transport and erosion are associated with shorter period waves an intra wave analysis of hydrodynamics and sediment suspension revealed that the main reason for the larger suspended sediment transport rates under plunging waves was i larger time averaged suspended sediment loads under plunging waves and ii a larger difference in cumulated sediment load under the wave crest phase compared to the wave trough phase for plunging breakers this latter difference was due to an earlier arrival at the seabed of higher levels of turbulent kinetic energy under plunging waves compared to spilling waves hence both magnitude and timing within the wave cycle of turbulent kinetic energy production are important in a quantification of sediment transport under breaking waves for ensemble averaged intense suspension events contributing roughly 50 of the total sediment suspension during individual records we found that instantaneous near bed sediment load was linearly related to instantaneous levels of froude scaled turbulent kinetic energy

density profile of an snc model martian interior and the moment of inertia factor of mars the density profile of an snc model martian interior is calculated from the results of previous experimental work that determined the modal mineralogy of the model mantle up to martian core mantle boundary pressures the moment of inertia factor of mars is calculated as a function of core composition and crustal thickness using the snc model mantle density profile as a constraint two sets of calculations are performed in the first the bulk composition of the planet is not constrained to a c1 chondrite composition assuming a martian crust density of 2 7 3 0 g cm3 a crust thickness of 25 150 km and the core composition proposed by dreibus and wanke fe 14 wt s the calculated moment of inertia factor ranges from 0 367 to 0 357 these models include a perovskite bearing zone in the martian interior considering core compositions ranging from pure fe to pure fes changes the moment of inertia factor by only 0 001 but at higher s abundances core size increases such that the depth of the core mantle boundary is shallower than the depth of perovskite stability in the second set of calculations the bulk composition of the planet is constrained to a c1 composition requiring a crust thickness of 180 320 km assuming a crust density of 2 7 3 0 g cm3 the calculated moment of inertia factor is 0 354 and a perovskite bearing layer is absent from the martian interior as it is unlikely that the thickness of the martian crust is greater than 100 km the bulk composition of mars cannot be constrained to a c1 chondrite composition as proposed by the dreibus and wanke model g dreibus h wanke meteoritics 20 1985 367 382 in order to determine if the martian mantle is more iron rich than the earth s mantle we may need not only an improved estimate of the moment of inertia factor of mars but also tighter constraints on martian crust thickness and density the absolute degree of iron enrichment however cannot be specified without also knowing the size of the martian core a moment of inertia factor of less than 0 342 is not geochemically feasible because it requires that the mantle of mars contains no iron

a two phase approach to wave induced sediment transport under sheet flow conditions a numerical model for the general description of the sediment transport under oscillatory sheet flow conditions is developed based on a two fluid representation of the two phase turbulent flows the governing equations of the model are the reynolds averaged continuity equations and equations of motion for both the fluid and the sediment phases the two phases are coupled by the interphase forces including the resistance force the inertia force and the lift force turbulence closure of the fluid phase is based on a slightly modified k epsilon model while an algebraic particle turbulence model is applied to the sediment phase the numerical method is based on the modified simple scheme and an improved time stepping technique the model is validated by the published data for the symmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at the university of tokyo and for both the symmetrical and the asymmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at university of aberdeen the numerical results on the temporal and spacial variation of the sediment concentration the horizontal velocities of the two phases the horizontal and vertical fluxes of the sediment phase as well as the thickness of the sheet flow layer all show satisfactory agreement with the laboratory data the model is also shown to predict the net sediment transport rate with a reasonably good accuracy c 2011 elsevier b v all rights reserved

seismological implications of a lithospheric low seismic velocity zone in mars most seismological models for the interior of mars lack an upper mantle low velocity zone however there is expected to be a large thermal gradient across the stagnant conductive lid lithosphere of mars this gradient should tend to decrease elastic wave velocities with increasing depth with this effect dominating the opposing tendency caused by increasing pressure with depth because mars has low gravity an upper mantle lithosphere with a low velocity zone lvz beneath a thin high velocity seismic lid is thus predicted the upcoming nasa insight mission includes a three component seismometer which should provide the first opportunity to directly detect any lithospheric lvz in mars seismic wavefields expected for mars mantle velocity structures with or without a strong lvz are very distinct the lvz models predict shadow zones for high frequency seismic body wave phases such as p s pp and ss etc the most diagnostic waves that can be used to evaluate presence of a lithospheric lvz given a single seismometer are intermediate period global surface waves which travel along the great circle from a seismic source to the seismometer an lvz produces distinctive dispersion with a rayleigh wave airy phase around 100 s period and very different surface wave seismograms compared to a model with no lvz even a single observation of long period surface waves from a known range can be diagnostic of the lithospheric structure

complex empirical orthogonal functions analysis of ers 1 and topex poseidon combined altimetric data in the region of the algerian current maps of sea level anomalies sla relative to the 1993 annual mean sea level combine the data from the two altimetric missions ers 1 and topex poseidon during the overlap period october 1992 to december 1993 these regular maps in space and time of residual sea level every 10 days on a 0 2 regular grid are used in the region of the algerian current where the mesoscale eddies are of primary importance to the circulation of all the mediterranean water masses they are first compared with ers 1 along track scanning radiometer sea surface temperature images to get information on two anticyclonic eddies produced by instabilities of the algerian current and visible in both infrared and altimetric data sets then an analysis of complex empirical orthogonal functions ceofs is performed on the sla data set to see the correlation of the different dynamic features of the observed variability the ceof analysis is applied to the complex time series formed from the original sla time series and their hubert transforms to separate the variability into spatially coherent modes the spatially correlated signal in the study area 0 15 e and 35 40 n was found to be dominated by the first two ceofs these first two modes explain nearly 85 of the variability with 80 of the total variance for the first one and 5 of the total variance for the second one the temporal phase of the first mode indicates that a constant frequency of one cycle per year is clearly dominant corresponding to the seasonal signal the strongest amplitude is obtained in the southern part of the channel of sardinia and south of the strait of sicily the temporal amplitude and the temporal phase of the second mode show a periodicity of about 6 months which appears to be associated with the variability of the algerian current as the phase isolines are parallel to the mean current path along the algerian coast the strongest amplitude of the second mode is located near the african coast at 4 e and 8 e these two points of high variability could correspond to eddy detachments from the main current

parameterization of intrawave ripple averaged sediment pickup above steep ripples near bed sediment pickup is critical for predictions of intrawave suspension and in turn net sediment transport in coastal models in the present study numerical results from a two dimensional reynolds averaged navier stokes model are used to assess the functional relationship of intrawave ripple averaged sediment pickup above steep ripples the numerical model provides intrawave time histories of ripple averaged near bed velocities and turbulence which are qualitatively interrogated to determine pickup functional relationships several specific sediment pickup formulations are implemented within the numerical model expressions relating pickup to near bed velocity or near bed turbulent kinetic energy via the bed shear stress and expressions relating pickup to near bed shear production of turbulent kinetic energy these are then tested via model data comparisons of near bed suspended sediment concentration the results show that the traditional functions relating sediment pickup to near bed velocity cannot lead to reasonable intrawave suspension predictions above vortex ripples under a ripple averaged framework instead relating sediment pickup to near bed turbulence quantities such as turbulent kinetic energy or shear production of turbulent kinetic energy significantly improves the numerical predictions for these conditions this article is protected by copyright all rights reserved

breaker turbulence and sediment suspension in the surf zone field measurements of fluid velocities and suspended sediment concentrations were used to investigate the relative role of coherent vortices related to wave breaking in suspended sediment dynamics the measurements were obtained from a barred intermediate type beach and the instrument rig was exposed to a range of wave types during the experiment including shoaling waves and both spilling and plunging breakers the time scale of the observed breaker vortices was 5 hz and thus in the frequency range of wave orbital motion coherent breaker vortices were separated from wave orbital motions and incoherent higher frequency turbulence using a threshold magnitude for the vertical velocity component plunging breakers displayed the largest root mean square rms and maximum vertical velocities the latter reaching approximately 1 m s 1 these measurements were made at an elevation of 0 15 m above the bed given the observed scale of the breaker vortices and the phase match between suspended sediment concentrations and fluid velocities the turbulence injected into the water column by the plunging breakers played a significant role in suspending bed sediment on the other hand the role of coherent vortex structures in suspending sediment under spilling breakers and shoaling waves is more limited rms vertical velocities under the spilling breakers and shoaling waves in this experiment were respectively a factor 2 and 4 smaller than for plunging breakers different phase relationships were observed between the horizontal fluid velocity and vortex induced sediment suspension for each of the wave types which may contribute to an explanation of net offshore and onshore sediment transport observed during episodes of beach erosion and recovery respectively

geodesy constraints on the interior structure and composition of mars abstract knowledge of the interior structure of mars is of fundamental importance to the understanding of its past and present state as well as its future evolution the most prominent interior structure properties are the state of the core solid or liquid its radius and its composition in terms of light elements the thickness of the mantle its composition the presence of a lower mantle and the density of the crust in the absence of seismic sounding only geodesy data allow reliably constraining the deep interior of mars those data are the mass moment of inertia and tides they are related to mars composition to its internal mass distribution and to its deformational response to principally the tidal forcing of the sun here we use the most recent estimates of the moment of inertia and tidal love number k2 in order to infer knowledge about the interior structure of the mars we have built precise models of the interior structure of mars that are parameterized by the crust density and thickness the volume fractions of upper mantle mineral phases the bulk mantle iron concentration and the size and the sulfur concentration of the core from the bulk mantle iron concentration and from the volume fractions of the upper mantle mineral phases the depth dependent mineralogy is deduced by using experimentally determined phase diagrams the thermoelastic properties at each depth inside the mantle are calculated by using equations of state since it is difficult to determine the temperature inside the mantle of mars we here use two end member temperature profiles that have been deduced from studies dedicated to the thermal evolution of mars we calculate the pressure and temperature dependent thermoelastic properties of the core constituents by using equations state and recent data about reference thermoelastic properties of liquid iron liquid iron sulfur and solid iron to determine the size of a possible inner core we use recent data on the melting temperature of iron sulfur within our model assumptions the geodesy data imply that mars has no solid inner core and that the liquid core contains a large fraction of sulfur the absence of a solid inner is in agreement with the absence of a global magnetic field we estimate the radius of the core to be 1794 65 km and its core sulfur concentration to be 16 2 wt we also show that it is possible for mars to have a thin layer of perovskite at the bottom of the mantle if it has a hot mantle temperature moreover a chondritic fe si ratio is shown to be consistent with the geodesy data although significantly different value are also possible our results demonstrate that geodesy data alone even if a mantle temperature is assumed can almost not constrain the mineralogy of the mantle and the crust in order to obtain stronger constraints on the mantle mineralogy bulk properties like a fixed fe si ratio have to be assumed

a two phase numerical model for sediment transport prediction under oscillatory sheet flows to predict sediment transport under oscillatory sheet flow condition especially for fine sand is still a challenging research subject in coastal engineering this paper describes a newly developed numerical model based on two phase theory with the use of a one equation turbulence closure and its applications in predicting fine sediment suspension in near prototype oscillatory sheet flow conditions model results were compared with comprehensive laboratory measurements of flow velocity and sediment concentration under both symmetrical and asymmetrical oscillatory sheet flows from a large scale water tunnel good agreements between the model results and measurements were achieved and the results demonstrated that the model is capable of reproducing detailed characteristics of sediment entrainment process in the sheet flow regime the comparisons also revealed the fact that the concentration peaks at flow reversal is associated with the strong vertical sediment transport flux in the pickup layer which has been widely observed in many laboratory experiments the effects of flow reversal events on total sediment transport were also discussed

recent advances in observing the physical oceanography of the western mediterranean sea the mediterranean sea has been investigated intensively since the early nineties using modern techniques and collaborative approaches this overview summarizes some of the resulting advances that were made concerning the physical oceanography of the western mediterranean the water mass formation processes are now much better understood and have been quantified to a large extent the boundary conditions of the system in terms of surface fluxes and strait transports can be determined with improved accuracy thus enabling future investigation of interannual variability the dynamics of the surface and intermediate layers have revealed a variety of eddy and mesoscale processes that are important for the circulation and spreading of water masses the deep circulation is being investigated with lagrangian techniques tracers and floats first results show a large component of the deep water originating from the tyrrhenian sea and intense cyclonic and anticyclonic eddy flows

interior structure of terrestrial planets modeling mars mantle and its electromagnetic geodetic and seismic properties 1 we present a new procedure to describe the one dimensional thermodynamical state and mineralogy of any earth like planetary mantle with mars as an example the model parameters are directly related to expected results from a geophysical network mission in this case electromagnetic geodetic and seismological processed observations supplemented with laboratory measurements we describe the internal structure of the planet in terms of a one dimensional model depending on a set of eight parameters for the crust the thickness and the mean density for the mantle the bulk volume fraction of iron the olivine volume fraction the pressure gradient and the temperature profile and for the core its mass and radius currently available geophysical and geochemical knowledge constrains the range of the parameter values in the present paper we develop the forward problem and present the governing equations from which synthetic data are computed using a set of parameter values among all martian models fitting the currently available knowledge we select eight candidate models for which we compute synthetic network science data sets the synergy between the three geophysical experiments of electromagnetic sounding geodesy and seismology is emphasized the stochastic inversion of the synthetic data sets will be presented in a companion paper

settling velocity of sediments at high concentrations new data on the settling velocity of artificial sediments and natural sands at high concentrations are presented the data are compared with a widely used semiempirical richardson and zaki equation trans inst chem eng 32 1954 35 which gives an accurate measure of the reduction in velocity as a function of concentration and an experimentally determined empirical power n here a simple method of determining n is presented using standard equations for the clear water settling velocity and the seepage flow within fixed sediment beds the resulting values for n are compared against values derived from new and existing laboratory data for beach and filter sands for sands the appropriate values of n are found to differ significantly from those suggested by richardson and zaki for spheres and are typically larger corresponding to a greater reduction in settling velocity at high concentrations for fine and medium sands at concentrations of order 0 4 the hindered settling velocity reduces to about 70 of that expected using values of n derived for spheres at concentrations of order 0 15 the hindered settling velocity reduces to less than half of the settling velocity in clear water these reduced settling velocities have important implications for sediment transport modelling close to and within sheet flow layers and in the swash zone

a geophysical perspective on the bulk composition of mars we invert the martian tidal response and mean mass and moment of inertia for chemical composition thermal state and interior structure the inversion combines phase equilibrium computations with a laboratory based viscoelastic dissipation model the rheological model which is based on measurements of anhydrous and melt free olivine is both temperature and grain size sensitive and imposes strong constraints on interior structure the bottom of the lithosphere defined as the location where the conductive geotherm meets the mantle adiabat occurs deep within the upper mantle 250 500 km depth resulting in apparent upper mantle low velocity zones assuming an fe fes core our results indicate 1 a mantle with a mg molar mg mg fe of 0 75 in agreement with earlier geochemical estimates based on analysis of martian meteorites 2 absence of bridgmanite and ferropericlase dominated basal layer 3 core compositions 13 5 16 wt s core radii 1640 1740 km and core mantle boundary temperatures 1560 1660 c that together with the eutectic like core compositions suggest the core is liquid and 4 bulk martian compositions that are overall chondritic with a fe si wt ratio of 1 63 1 68 we show that the inversion results can be used in tandem with geodynamic simulations to identify plausible geodynamic scenarios and parameters specifically we find that the inversion results are reproduced by stagnant lid convection models for a range of initial viscosities 1019 1020 pa s and radioactive element partitioning between crust and mantle around 0 001 the geodynamic models predict a mean surface heat flow between 15 25 mw m2

mineralogy of the martian interior up to core mantle boundary pressures in order to determine the mineralogy of the martian interior along a high temperature areotherm multianvil experiments have been performed with a model martian mantle composition up to 23 5 gpa the dreibus and wanke 19851 martian mantle composition yields an upper mantle that consists of olivine clinopyroxene orthopyroxene garnet at pressures up to 9 gpa above 9 gpa orthopyroxene is no longer present the transition zone is marked by the appearance of spinel at 13 5 gpa up to 15 gpa clinopyroxene and majorite coexists with phase and or spinel by 17 gpa clinopyroxene is entirely replaced by majorite and the modal abundance of spinel increases at the expense of phase the dominant assemblage throughout most of the transition zone is spinel majorite two experiments completed in the perovskite stability field indicate that the lower mantle consists of mg fe silicate perovskite magnesiowustite and majorite casio 3 perovskite is not present in these experiments both the presence of a martian lower mantle i e an mg fe silicate perovskite bearing zone and the phase assemblage stable in the martian lower mantle are very sensitive to the temperature profile of the interior a low temperature profile may stabilize stishovite in the lower mantle or it may lead to the absence of the lower mantle because of the higher transition pressure required for forming perovskite at lower temperatures regardless of the temperature profile assumed the martian upper mantle and transition zone will account for a larger proportion of the planet s interior than is the case for the earth s interior because of the smaller size of mars

long period seismology on europa 2 predicted seismic response 1 previous studies have documented the potential for using relatively short period body waves and intermediate period surface waves to explore the structure and tectonics of europa we show that long period measurements 0 001 to 0 1 hz may have large amplitudes of displacement millimeters to centimeters and are potentially measurable from orbit without requiring a lander to accurately model the long period response of europa we use normal modes calculated from physically self consistent models of europa s structure developed in part 1 cammarano et al 2007 on the basis of the geometry of observed faults we estimate that faulting events of magnitude 5 or larger may occur regularly synthetic seismograms show that long period displacement measurements with millimeter accuracy could detect current tectonic activity and determine the thickness of europa s ice shell and confirm the presence of a subsurface ocean determination of deeper structure with seismic measurements however is more challenging in the presence of a global liquid ocean which acts to decouple deeper seismic energy from the surface

modelling cross shore intensive sand transport and changes of bed grain size distribution versus field data abstract the study is focused on the cross shore transport of size graded sediment under combined wave current flow in the intensive flow regime the mathematical method for the description of hydrodynamic processes and sediment transport is adapted from the approach of kaczmarek and ostrowski coast eng 45 2002 1 for non graded sediment the theoretical model of vertical structure of sediment concentration as well as vertical mixing and sorting is presented the model of transport of graded sediment accounts for two directional cross shore sand flux the first component of this flux is directed onshore and results from wave asymmetry effects while the second one is directed seawards and is caused by undertow the vertical structure of this two directional sediment flux and its variability along a cross shore profile is a reason for segregation of grains in a horizontal direction this horizontal sorting of sand is theoretically modelled using the present approach a concept of the carpet of sorted sediments is implemented to reproduce the segregation of sediment in time and to assess the influence of grain size changes on short term evolution of the cross shore profile the results of computations are compared with the large scale laboratory data from the literature and with field measurements carried out by the authors the agreement between the model results and the experimental data is found to be very good particularly it has been theoretically shown that the observed in situ bimodal grain size distributions result from two directional sediment fluxes on the cross shore profile

the age of the inner core abstract the energy conservation law when applied to the earth s core and integrated between the onset of the crystallization of the inner core and the present time gives an equation for the age of the inner core in this equation all the terms can be expressed theoretically and given values and uncertainties of all relevant physical parameters the age of the inner core can be obtained as a function of the heat flux at the core mantle boundary and the concentrations in radioactive elements it is found that in absence of radioactive elements in the core the age of the inner core cannot exceed 2 5 ga and is most likely around 1 ga in addition to have an inner core as old as the earth concentrations in radioactive elements needed in the core are too high to be acceptable on geochemical grounds

dissipation at tidal and seismic frequencies in a melt free anhydrous mars 1 the measured inward motion of phobos provides a constraint on the tidal dissipation factor q within mars we model viscoelastic dissipation inside a convective mars using a modified burgers model based on laboratory experiments on anhydrous melt free olivine the model tidal q is highly sensitive to the mantle potential temperature and grain size assumed but relatively insensitive to the bulk density and rigidity structure q thus provides a tight constraint on the martian interior temperature by fitting the observed tidal q and tidal love number k2 values and requiring present day melt generation we estimate that for a grain size of 1 cm the current mantle potential temperature is 1625 75 k similar to that of the earth this estimate is consistent with recent petrologically derived determinations of mantle potential temperature but lower than estimates in some thermal evolution models the presence of water in the martian mantle would reduce our estimated temperature our preferred mantle grain size of 1 cm is somewhat larger than that of the earth s upper mantle the predicted mantle seismic q is about 130 and is almost independent of depth the martian lithosphere represents a high seismic velocity lid which should be readily detectable with future seismological observations

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

onshore offshore sediment transport on beaches abstract the onshore offshore transport of sediment on beaches in analyzed by considering the time averaged behaviour of a control volume bounded by the wave breaking zone and by the beach face interactions are determined between the wave radiation stress the wave set up the shear stress on the beach face and the beach permeability simple theoretical relationships are derived which specify beach slope in terms of incident wave attack and beach material properties these relationships indicate that coarser sediment beaches are steeper because of the higher beach permeability it is also shown that any particular beach will decrease its slope as the wave attack increases according to an inverse function of the wave height not only the beach permeability but also the sediment grading curve is shown to be a key factor in determining beach slope the theory is used to discuss and explain some observed behaviour on real beaches and the possible implications for beach failure under storm attack

observation of a deep convection regime with acoustic tomography in the winter of 1991 1992 a convection experiment was conducted in the western mediterranean gulf of lions combining a variety of observational techniques an essential component was an acoustic tomography array consisting of six moorings designed to observe the time evolution of the large scale processes believed to be relevant in a convection regime here two dimensional slice inversions in three directions from the central mooring are used to estimate the volume of convected water and the mean convection depth and to observe the preconditioning and restratification processes before and after the convection the near surface layer is well sampled by the acoustics which show cooling and subsequent entrainment of the warmer levantine intermediate water liw from below in agreement with mixedlayer calculations during the 2 months prior to the main convection event the total heat loss of the large scale field is in approximate agreement with the surface heat fluxes showing that little net warm water advection takes place from outside the convection region the implied confinement of water by the local circulation should be an important factor in setting the location and extent of the deep convection patch the volume of water modified by convection in this winter is estimated to correspond to an area of order 60 km radius and 1500 m depth it is argued that the homogenized area implies an annual mean deep water replenishment of 0 3 sv the restratification by the return of less dense water in the surface and liw layers occurs first by rapid capping in the near surface region thereafter the southern and eastern parts of the region restratify in the deeper layers on a 40 day timescale while a dense core of 50 60 km diameter remains in the northwest until the end of the experiment

surface circulation variability in the balearic basin the balearic basin is defined as a wide region of the western mediterranean located in between the liguro provencal and algerian basins the dynamics of the liguro provencal basin in the north is dominated by the dense water formation process associated with a permanent circulation along the continental slope the northern current the algerian basin in the south is dominated by intense mesoscale eddies and their interactions with the unstable algerian current the balearic basin is a transition region between these two different dynamic regimes it includes the catalan sea located between the balearic islands and the iberian peninsula and the wide gulf of valencia in the south of this sea some new ideas about the surface circulation variability have been inferred from a series of noaa satellite advanced very high resolution radiometer images taken mainly from the autumn winter period during 1981 1988 and also from various in situ data the northern current which flows southward along the iberian peninsula slope is covered in summer by a warm surface layer spreading over the whole catalan sea this local warming creates one of the most intense thermal fronts in the western mediterranean the pyrenees front near the balearic islands the flow through the sills of recent atlantic water partially deflected by anticyclonic eddies from the algerian current creates the balearic front and contributes to its mesoscale variability this variability appears to be much more intense than previously described the balearic front is clearly recognized as the westward continuation of the north balearic front already defined in the open sea as the northern limit of the recent atlantic water reservoir finally the gulf of valencia is frequently influenced by water entering from the algerian basin which appears to be important in the disruption of the northern current and the formation of the balearic current the geostrophic flow associated with the balearic front

two phase flow modelling of sediment motions in oscillatory sheet flow in this paper a two phase flow model is presented which simulates the fluid and sediment motions in the sheet flow regime on a flat bed under oscillatory flow conditions the model is developed based on the continuity equations and linearised momentum equations for the fluid and sediment phases respectively all major forcing terms such as the intergranular stresses and the turbulent stress are included in the model from the detailed computations and comparison with the available laboratory data it has been demonstrated that the model is capable of predicting fairly accurately both flow kinematics and sediment concentrations in particular the model predicts that the well known phenomenon of fluid velocity over shoot that exists in clear water also appears in the case of lighter sediments but vanishes when the materials are heavier which is in perfect accord with the experimental observations considered

sand transport beneath waves the role of progressive wave streaming and other free surface effects recent large scale wave flume experiments on sheet flow sediment transport beneath stokes waves show more onshore directed sediment transport than earlier sheet flow experiments in oscillating flow tunnels for fine sand this extends to a reversal from offshore tunnels to onshore flumes directed transport a remarkable hydrodynamic mechanism present in flumes with free water surface but not in tunnels rigid lid is the generation of progressive wave streaming an onshore wave boundary layer current this article investigates whether this streaming is the full explanation of the observed differences in transport in this article we present a numerical model of wave induced sand transport that includes the effects of the free surface on the bottom boundary layer with these effects and turbulence damping by sediment included our model yields good reproductions of the vertical profile of the horizontal mean velocities as well as transport rates of both fine and medium sized sediment similar to the measurements the model reveals the reversal of transport direction by free surface effects for fine sand a numerical investigation of the relative importance of the various free surface effects shows that progressive wave streaming indeed contributes substantially to increased onshore transport rates however especially for fine sands horizontal gradients in sediment advection in the horizontally nonuniform flow field also are found to contribute significantly we therefore conclude that not only streaming but also inhomogeneous sediment advection should be considered in formulas of wave induced sediment transport applied in morphodynamic modeling we propose a variable time scale parameter to account for these effects

a prediction of mars seismicity from surface faulting the shallow seismicity of mars has been estimated by measurement of the total slip on faults visible on the surface of the planet throughout geologic time seismicity was calibrated with estimates based on surface structures on the moon and measured lunar seismicity that includes the entire seismogenic lithosphere results indicate that mars is seismically active today with a sufficient number of detectable marsquakes to allow seismic investigations of its interior

the interior structure of mars implications from snc meteorites two end member models of mars present interior structure are presented the first model is optimized to satisfy the geochemical data derived from the snc meteorites in terms of the bulk chondritic ratio fe si 1 71 while the second model is optimized to satisfy the most probable maximum value c 0 366 x m p r p 2 of the polar moment of inertia factor hydrostatic equilibrium and stationary heat transfer are assumed and the basic differential equations for the mechanical and thermal structure are solved numerically together with an isothermal murnaghan birch type equation of state truncated in eulerian strain at forth order we obtain the radial distribution of mass hydrostatic pressure gravity temperature and heat flow density along with the corresponding density stratification viscosity profiles and the global seismic velocity structure of model mars the first model being consistent with the geochemical requirement produces c 0 357 x m p r p 2 whereas the second model commensurate with the geophysical constraint gives fe si 1 35 the calculated central pressure is about 40 gpa in both models and the central temperature is in the 2000 to 2200 k range the model calculations suggest a fe ni fes core a little less than one half of the planetary radius in size surrounded by a silicate mantle subdivided into lower spinel and upper olivine layers and overlain by a 100 to 250 km thick basaltic crust and a surface heatflow density of 25 to 30 mw m 2 in both models the pressure in the mantle is not sufficient for the spinel to perovskite transition to occur the present thermal lithosphere is estimated to be about 500 km thick and to be subdivided into a 300 km thick outermost rheological lithosphere and an underlying thermal boundary layer of mantle convection given the core sulfur content of 14 wt as derived from snc meteorites the martian core is found to be entirely molten implying the nonoperation of a self sustained dynamo due to the absence of sufficiently vigorous convection

seismic detection of meteorite impacts on mars abstract meteorite impacts provide a potentially important seismic source for probing mars interior it has recently been shown that new craters can be detected from orbit using high resolution imaging which means the location of any impact related seismic event could be accurately determined thus improving the constraints that could be placed on internal structure using a single seismic station this is not true of other seismic sources on mars such as sub surface faulting which require location using multiple seismic stations this study aims to determine the seismic detectability of meteorite impacts and assess whether they are a viable means of probing deep internal structure first we derive a relation between crater diameter and equivalent seismic moment based on observational data compiled from impact tests controlled explosions and earthquake seismology second this relation was combined with updated cratering rates based on newly observed craters to derive the impact induced seismicity on mars which we estimate to total 10 13 10 14 n m per year finally seismic waveform modelling was used to determine the detectability of these impacts based on reasonable assumptions about likely seismometer performance and background noise levels for our nominal noise instrument case we find that detectable impacts at teleseismic distances source receiver offsets greater than 60 are very rare and occur approximately once every 10 years for our most optimistic noise instrument case approximately one such event occurs each year this suggests that using solely meteorite impacts is not a reliable way of probing the martian interior although local impacts are more frequently detectable and could provide important constraints on near surface seismic properties

nonlinear signal comparison and high resolution measurement of surface wave dispersion abstract in surface wave dispersion measurement we use cross correlation to compare the recorded signals at different stations to measure their phase difference however the measurement resolution is poor at low frequencies and the poor resolution was often incorrectly interpreted as large measurement errors here we propose a new nonlinear signal comparison nlsc approach to achieve a uniform high resolution measurement across a wide frequency band furthermore we can control the overall resolution in nlsc by an adjustable parameter the traditional cross correlation is a special case of nlsc we use both synthetic and recorded seismic data to demonstrate the effectiveness of nlsc by extracting surface rayleigh wave phase velocity dispersion curves for different datasets including synthetic multimode rayleigh wave data synthetic global rayleigh waves of a martian seismic model and a real ambient noise correlation data processed from the usarray

shear stress and sediment transport calculations for swash zone modelling it is shown that the observed difference in sediment transporting efficiency by the swash uprush compared with the downrush could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush the bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead phi tau of the bed shear stress compared with the free stream velocity at the peak frequency with this approach the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula without the need for different uprush and downrush coefficients while the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre suspended sediment in the uprush nevertheless the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre suspended sediment to the onshore sediment transport in swash zones c 2002 published by elsevier science b v

thermal evolution of the martian core implications for an early dynamo mars is thought to have possessed a dynamo that ceased 0 5 b y after the formation of the planet a possible but ad hoc explanation is an early episode of plate tectonics which drove core convection by rapid cooling of the mantle we present an alternative explanation that the martian core was initially hotter than the mantle after core formation providing an initial high heat flux out of the core a core initially 150 k hotter than the mantle can explain the early dynamo without requiring plate tectonics recent experimental results suggest that potassium is likely to partition into the martian core potentially providing an extra source of energy to power a dynamo we find that the radioactive decay of 40 k cannot explain the inferred dynamo history without the presence of a hot core our results also suggest that core solidification is unlikely to have occurred because this process would have generated a long lived 1 b y dynamo if as we conclude the core is entirely liquid it must contain at least 5 wt sulfur an initially hot core is consistent with geochemical evidence for rapid core formation and incomplete thermal equilibration with the mantle thus the early history of planetary dynamos provides constraints on the processes of accretion and differentiation