data driven modeling of multiple longshore bars and their interactions abstract long term bathymetric surveys at a coastal segment of the southern baltic coast were investigated with empirical orthogonal functions eof to determine the characteristic evolution patterns of multiple longshore bars and with canonical correlation analysis cca to evaluate the importance of interactions among them the investigated beach is located at lubiatowo on the polish coast and is mildly sloping with multiple usually four bars and a median grain size of 0 22 mm being typical for the coast in the southern baltic sea data on bed topography have been collected at lubiatowo since 1987 predominantly twice a year to record changes in the seabed along 27 lines covering a longshore cross shore area of 2600 m 1000 m the eof analysis revealed three persistent long term cross shore patterns accounting for about 2 3 of the overall signal variance and describing key elements of the evolution of multiple bars moreover it detected subsystems of two inner and outer bars the cca study demonstrated that more that 60 of the evolution of inner bars can be explained by the variability of outer bars the two subsystems thus display significant interactions they can be largely attributed to vertical variations of the whole nearshore zone expressed through changes in the equilibrium dean type profiles such changes can only be produced by large scale phenomena e g sequences of extreme events affecting the whole nearshore topography hence part of the variability of inner bars not related to the evolution of outer bars should stem from changes occurring during calm periods when small waves pass over outer bars unaffected the paper demonstrates usefulness of the cca method in coastal engineering and a more general strategy of data driven investigations with more than one method in order to make use of synergy generated with such a complex approach the benefit of such a synergy is that results from both investigations can be critically intercompared so more accurate joint interpretations become feasible

use of numerical models to study land based sedimentation and subsequent nearshore morphological evolution a beach sedimentation problem is presented this problem involves assessing the impact and importance of land based sediment sources erosion from gullies during intense rainfall and directly from cliffs by wave action on morphodynamic changes at a beach the site motivating the study is la barrosa beach spain the location is described and a discussion of possible approaches presented a schematized representation of a gully and beach is used a hybrid approach is adopted in which sediment deposition by run off and to a lesser extent cliff erosion is modelled using wave resolving hydrodynamic models it is found that significant amounts of sediment can be supplied by gully run off during storms for small run offs the swash can be involved in determining the region of deposition within the gully area with longer period motions favouring increased sediment deposition at gully sides simulations also show that swash motions can erode gully sides and the presence of a cross shore jet associated with the swash and gullies can also impact on sediment movement longer term wave averaged morphodynamic modelling without a swash zone indicates that run off deposits subsequently diffuse laterally whether under normal or oblique incidence these simulations also reveal the possibility of underlying crescentic bar shedding dynamics that may pertain during changes of wave conditions

a ground motion predictive model for iran and turkey for horizontal pga pgv and 5 damped response spectrum investigation of possible regional effects we present a ground motion prediction equation gmpe for turkey and iran to investigate the possible regional effects on ground motion amplitudes in shallow active crustal earthquakes the proposed gmpe is developed from a subset of the recently compiled strong motion database of the earthquake model of the middle east region project see data and resources 1 a total of 670 turkish and 528 iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration peak ground velocity and 5 damped elastic pseudospectral acceleration ordinates of 0 01 s t 4 s the moment magnitude range of the model is 4 m w 8 and the maximum joyner boore distance is r jb 200 km the functional form considers three major fault mechanisms strike slip normal and reverse the nonlinear soil behavior is a function of v s 30 average shear wave velocity in the upper 30 m of soil profile our observations from empirical and estimated ground motion trends advocate regional differences in the territories covered by iran and turkey that originate from the differences in q factors kappa and near surface velocity profiles these factors eventually affect the magnitude and distance dependent scaling of spectral amplitudes in iran and turkey in essence the ground motion amplitudes of these two neighboring countries would draw patterns different than the ground motion estimates of gmpes developed from the strong motion databases of shallow active crustal earthquakes from multiple countries online material matlab code and regression coefficients for computing the response spectrum and distance scaling 1 sec 7

ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

hydration and uplift of the oceanic crust on the mid atlantic ridge associated with hydrothermal activity evidence from boron isotopes boron isotope systematics of vent fluids from the mid atlantic ridge mar and the faster spreading east pacific rise epr reveal that at the mar 50 of seawater boron is removed from circulating fluids on the downwelling limb of the hydrothermal convection cell whereas little boron is removed at epr sites geophysical and petrographic studies suggest that downwelling fluids on the mar penetrate deep in the oceanic crust and upper mantle where boron is removed during serpentinization of peridotite the associated hydration of the oceanic crust reduces its density and modelling of the data suggests that this results in uplift leading to significant elevation of the median valley walls in the vicinity of active hydrothermal systems

nourishing the shoreface observations and hindcasting of the egmond case the netherlands abstract although beach nourishment policy in the netherlands is generally successful in maintaining the 1990 shoreline the efficiency of nourishments at several locations along the north sea coast is unacceptably low these locations are identified as erosion hotspots egmond aan zee is such a hotspot the bathymetric longshore irregularities make this coastal stretch highly susceptible to rip currents and horizontal circulations which transport large volumes of nourished sand to the sea in 1999 an alternative nourishment design was implemented this consisted of a shoreface nourishment at the outer bar at 7 5 m depth combined with a nourishment of the beach behind it high resolution bathymetric surveys carried out with the wesp revealed that the shoreface nourishment resulted in a significant shoreward migration of the outer bar during 1999 2001 after 2 years the system started to return to its natural dynamic equilibrium and lost the positive influence of the shoreface nourishment area shoreward movement of bars and increase of bar height which forms the first defense line of the mainland against the sea and positive contribution to the sand budget which increased as a result of the nourishment after 3 years may 1999 to april 2002 the sediment volume still had an increase of 477 500 m3 45 of the applied sand relative to may 1999 the shoreface nourishment area did not have a direct effect on the beach the shoreface nourishment area probably will have to be maintained to retain the sediment on the beach in the long run in egmond the shoreface nourishment started to disappear before the sediment could reach the beach the time scale of sediment feed to the beach zone probably is of the order of 5 10 years the shoreface nourishment seems to function as a reef creating a lee side effect that influences both cross shore and longshore sediment transport resulting in two main hypotheses firstly the longshore effect in which large waves break at the shoreface nourishment cause a calmer wave climate shoreward of the shoreface nourishment area and a reduction of the longshore current the shoreface nourishment partially blocks the wave driven longshore current secondly the cross shore effect in which shoaling waves generate onshore transport these hypotheses are supported by generated model results with both a process based profile model unibest tc and a process based coastal area model delft3d mor the unibest tc model was able to predict the detachment of the outer bar from the shoreface nourishment and to some extent the shoreward bar movements in the lee of the shoreface nourishment area the model found an increase in sediment confirming the shielding effect of the shoreface nourishment area the delft3d model found as a result of the shoreface nourishment area a decrease of the flow velocity and the wave height just shoreward of the shoreface nourishment area the model was able to predict the similar trend in sedimentation erosion pattern although the intensities were smaller in the lee of the shoreface nourishment area a clear sedimentation was found erosion was found south and seaward of the shoreface nourishment area the modeled profiles did not follow the measured profile changes the separation of the shoreface nourishment from the outer bar and the shoreward migration of the bars could not be accurately modeled because the cross shore transport caused by wave asymmetry is not taken into account in the standard version of delft3d these results were in line with the expectations

lithium boron and lead isotope and trace element systematics of quaternary basaltic volcanic rocks in northeastern japan mineralogical controls on slab derived fluid composition abstract across arc li b pb isotope systematics together with trace element geochemistry and phase relationships in subducting slabs are used to understand the petrogenesis of lavas from the northeastern japan arc pb nb ratios and pb isotope compositions of the arc lavas decrease with depth to slab whereas li y u nb th nb and la sm show an upward profile across the arc with peaks at 180 km depth to the wadati benioff zone wbz the peaks in these profiles may reflect the influence of lawsonite breakdown in the slab at 180 km depth b nb ratios of the arc lavas do not show clear across arc variation and the 11b values show a concave upward across arc profile with minimum values at around 180 km in depth of the wbz these results possibly reflect the decomposition of tourmaline at 180 km our results suggest that accessory minerals and minor phases in the subducting slab play important roles in determining the chemical compositions of fluid released by dehydration and the resulting trace element and isotope composition of arc lavas li isotope compositions of the lavas are morb like and do not show systematic across arc variation contrasting with izu arc lavas which show maximum 7li values at the volcanic front and a systematic decrease towards the back arc the strikingly different results for the northeastern japan arc and the izu arc are likely to be caused by differing extents of li isotope fractionation due to differing subduction zone physical characteristics such as thermal structure of the subducting slab and subduction angle thus not only chemical characteristics of the subducting slab but also the physical as well as chemical characteristics of the subduction zone could affect the li isotope compositions of subducting slabs producing heterogeneity in the li isotope composition of the mantle

subevent analysis for the tabas earthquake of september 16 1978 using near field accelerograms we analyze the strong motion accelerograms of the large magnitude mb 6 4 ms 7 7 mw 7 4 m0 1 32 10 20 tabas earthquake of september 16 1978 the earthquake occurred due to a unilaterally propagating complex rupture process on a thrust fault system the imprints of rupture of four and possibly five asperities sub faults have been identified on the accelerograms using derived sh wave records the locations of these asperities which lie on the main causative fault and the relative times of their occurrence have been determined a foreshock that occurred about 6 s prior to the main shock has also been identified and located further using sh wave spectral data we provide near field estimates of the strike dip and slip of these asperities as well as their seismic moment moment magnitude fault area released shear wave energy and average stress drop the spectra of the sub events conform to the 2 brune spectra the total seismic energy of the sub events is consistent with the radiated energy estimated from teleseismic observations the fault plane solutions show generally wnw ese strike which is sub parallel to the regional strike of the geological fault system existing in the area the stress drops are in the range of 7 30 bar with the exception of the main sub event that showed a stress drop of 100 bar overall the sub events show self similarity the average shear wave quality factor qs which in the near field is quite sensitive to the local site geology has been found to lie between 600 and 1200 the decay of pga with distance is found to be compatible with niazi and bozorgnia s niazi m bozorgnia y 1992 the 1990 manjil iran earthquake geology and seismological overview pga attenuation and observed damage bull seism soc am 82 774 799 attenuation relation for the region 2005 elsevier b v all rights reserved

record in metamorphic tourmalines of subduction zone devolatilization and boron cycling boron concentrations and isotope compositions of fluids and lavas from subduction zone settings show great potential for elucidating mass flux at earth s modern convergent margins however the fluid mineral melt behaviorof b and its two stable isotopes remains relatively poorly understood boron isotope analyses of tourmaline in metasedimentary rocks subducted to 15 90 km depths 1 demonstrate the ability of this mineral to retain information regarding prograde devolatilization history in even highly retrograded rocks and 2 indicate the importance of tourmaline in affecting whole rock b loss and b isotope evolution during subduction zone metamorphism the b lost from micas during metamorphism of subducting sedimentary rocks and altered oceanic crust is isotopically more enriched in 1 1 b than the b retained in the micas beneath forearcs and volcanic arcs the b from micas is either removed from the subduction zone rocks via metamorphic fluids or sequestered by growing tourmaline in which the b can be entrained to even greater depths here we demonstrate that these metamorphic fluids could contribute to the relatively high 811b signatures observed in most arc lavas and the across arc trends of decreasing 1 1 b observed in several arcs

the b isotopic composition of arc lavas from martinique lesser antilles island arc samples from martinique lesser antilles are enriched in b relative to oceanic crust or the mantle with b contents varying between 5 and 54 ppm and have 11b falling in a range between 1 8 and 5 3 less than the 11b of altered oceanic crust the combination of these results indicates that both sediments and altered oceanic crust must have been involved in the generation of those magmas since the abundance of b in the mantle is too low to produce such low 11b values with such high b concentrations b content and 11b are not correlated showing that the amount of b added to the arc magma was decoupled from its isotopic composition by the mixing of at least three distinct components boron concentrations considered in conjunction with 87sr 86sr 143nd 144nd 18o and 11b data show that variable amounts of b were added by a b enriched fluid to different batches of mantle derived magma the b sr and nd isotopic compositions of these samples are consistent with a two stage process in which enriched magma is produced in the mantle wedge by the addition of an aqueous fluid derived from dehydrating subducting lithosphere and then modified during ascent by assimilation of variable amounts of sediment and altered oceanic crust most of the b contained in the fluid was probably derived from altered oceanic crust plus as little as 3 sediment while the material involved in assimilation was apparently largely continentally derived sediment a two stage process like this also explains the distribution of 18o within the context of the b sr and nd isotopic compositions of martinique arc lavas

medium term 2dh coastal area modelling the state of the art in depth averaged mathematical modelling of 3 d coastal morphology is described for the medium term morphodynamic model type in which constituent models of waves currents and sediment transport based on first physical principles are linked together to describe the time evolution of the bed topography various aspects of the combined system of equations are discussed such as its mathematical character its inherent stability and its equilibrium state the results of an intercomparison of different models are shown for two test cases and the potentials and limitations of the model concept are discussed

a morphological stability analysis for a long straight barred coast a morphological stability analysis is carried out for a long straight coast with a longshore bar the situation with oblique wave incidence and a wave driven longshore current is considered the flow and sediment transport are described by a numerical modelling system the models comprise i a wave model with depth refraction shoaling and wave breaking ii a depth integrated model for wave driven currents and iii a sediment transport model for the bed load transport and the suspended load transport in combined waves and current the direction of the sediment transport is taken to be parallel to the depth integrated mean current velocity neglecting the effects of a bed slope and secondary currents an instability is found to develop around the bar crest the instability is periodic in the alongshore direction and tends to form rip channels and to steepen the offshore face of the bar between the rip channels the alongshore wave length of the most unstable perturbation is determined for different combinations of the wave conditions and the geometry of the profile

empirical stochastic ground motion prediction for eastern north america an alternative approach based on a hybrid empirical model is utilized to predict the ground motion relationship for eastern north america ena in this approach a stochastic model is first used to derive modification factors from the ground motions in western north america wna to the ground motions in ena the ground motion parameters are then estimated to develop an empirical attenuation relationship for ena using empirical ground motion relationships from wna w e develop an empirical stochastic source model for both regions to obtain ground mo tions at different magnitude distance range of interest at short distances r 30 km and large magnitudes mw 6 4 an equivalent point source model is carried out to consider the effect of finite fault modeling on the ground motion parameters source focal depth and brune stress drop are assumed to be magnitude dependent we choose three well defined empirical attenuation relationships for wna to com pare the empirical ground motion processes between the two regions a composite functional attenuation form is defined and in turn a nonlinear regression analysis is performed by using a genetic algorithm ga for a wide range of magnitudes and distances to develop an empirical attenuation relationship from the stochastic ground motion estimates in ena the empirical stochastic attenuation relationship for hor izontal peak ground acceleration and spectral acceleration are applicable to earth quakes of mw 5 0 8 2 at distances of up to 1000 km the resulting attenuation model developed in this study is compared with those used in the 2002 national seismic hazard maps derived in the 2003 electric power research institute studies and re corded in ena the comparison of the results to the other attenuation functions and the available ena data show a reasonable agreement for the ena ground motions

beach face evolution in the swash zone we investigate swash on an erodible beach using the one dimensional shallow water equations fully coupled to a bed evolution exner equation in particular the dam break bore collapse initial condition of shen meyer j fluid mech vol 16 1963 pp 113 125 and peregrine williams j fluid mech vol 440 2001 pp 391 399 is investigated using a numerical model based on the method of characteristics a sediment transport formula cubic in velocity u au 3 is used here this belongs to a family of sediment transport formulae for which pritchard hogg coastal engng vol 52 2005 pp 1 23 showed that net sediment transport under the shen meyer 1963 bore collapse is offshore throughout the swash zone when a non erodible bed is considered it is found that full coupling with the beach although still resulting in the net offshore transport of sediment throughout the swash zone leads to a large reduction in the net offshore transport of sediment from the beach face this is particularly true for the upper third of the swash zone moreover in contradistinction to swash flows over non erodible beds flows over erodible beaches are unique to the bed mobility and porosity under consideration this has very important implications for run up predictions the conclusion is that it is essential to consider full coupling of water and bed motions i e full morphodynamics in order to understand and predict sediment transport in the swash regardless of other physical effects e g turbulence infiltration pre suspended sediment etc

bbe systematics in subduction related metamorphic rocks characterization of the subducted component the mobility of b and be in h2o rich fluids and felsic silicate liquids produced during metamorphism of subducted oceanic slab and sediments has been investigated through analysis of subduction zone metamorphic rocks of the catalina schist california in metasedimentary rocks b be and the range in b be decrease with increasing metamorphic grade mean 72 std dev 41 for lowest grade lawsonite albite fades rocks mean 21 std dev 11 for higher grade greenschist and epidote amphibolite facies equivalents this decrease to more uniformly low b be may be attributed to the preferential removal of b in h2o rich fluids produced by devolatilization reactions over the approximate temperature interval of 350 600 c metamafic rocks do not show pronounced decrease in b be with increasing metamorphic grade however all metamafic samples have b be 30 lower than values for many altered seafloor basalts in amphibolite grade exposures felsic leucosomes and pegmatites reflecting partial melting have low b be similar to their metasedimentary and metamafic hosts which presumably experienced prior reduction in b be during lower temperature devolatilization this evidence for b and be mobility during high p t metamorphism complements studies of b be systematics in arc volcanic rocks in further characterizing mechanisms by which slab derived elements can be added to the source regions of arc lavas before subducted mafic and sedimentary rocks reach wadati benioff zone depths beneath arcs 80 150 km the b be of these rocks is likely to have decreased to 30 thus highly fractionated slab derived hydrous fluids may be necessary to generate the high b be signatures observed in many arcs b be of up to 200 the b be data together with previously presented stable isotope data for the catalina schist demonstrate that subduction zone metamorphic processes are capable of homogenizing presubduction variability in the concentrations of particularly fluid mobile elements in rocks and may through mixing produce fluids which trend toward uniform trace element and isotopic compositions these homogeneous fluids could infiltrate parts of the mantle wedge and contribute to the characteristic trace element and isotopic signatures of arc magma source regions in hotter subduction zones e g involving subduction of young hot oceanic lithosphere silicate melts derived from previously devolatilized sedimentary and mafic rocks may contribute relatively low b be signatures to arc source regions thus significant variations among arcs in the ranges of b be observed in front rank volcanoes e g for the bismarck arc b be 20 190 for the cascades arc b be 5 may be related in part to varying thermal structure which could govern both the b be of hydrous fluids and the relative proportions of hydrous fluid and silicate melt derived from the subducted slab and sediments

partially nonergodic empirical ground motion models for predicting horizontal and vertical pgv pga and 5 damped linear acceleration response spectra using data from the iranian plateau we present new ground motion prediction equations gmpes to estimate horizontal and vertical strong ground motion intensity measures gmims generated by shallow active crustal earthquakes occurring within the iranian plateau to this end a dataset containing 688 records from 152 earthquakes with moment magnitudes ranging from 4 7 to 7 4 and joyner boore distances up to 250 km has been used the effects of the local site condition are taken into account using the time averaged shear wave velocities in the upper 30 m v s 30 we decided not to include the style of faulting term in the final functional form because the total standard deviation is reduced 10 by removing this term from the functional form we used a nonlinear mixed effects regression to determine the coefficients of the functional form and to separate out the between event and between station standard deviations from the total standard deviation significant standard deviation of site to site variability demonstrates that the ergodic assumption is not able to account for the spatial variability of ground motions we introduced random effects coefficients to capture regional variations between different tectonic regions of the iranian plateau such as alborz and zagros in the regression analysis to investigate the effects of regionalization on gmpes the results showed that although the effects of regional variations for considered regions are negligible at close distances they are significant at longer distances the complexity and performance of the final functional form is justified by comparing akaike and bayesian information criteria values over many trial functional forms moreover the distribution of between event site to site and event station corrected residuals demonstrates that no trends are evident implying satisfactory performance of the proposed gmpes therefore the derived gmpes can be employed to predict gmims and to do seismic hazard assessments within the iranian plateau electronic supplement 1 lists of the events and stations considered in the final dataset and derived coefficients of the functional form 1 http www bssaonline org lookup suppl doi 10 1785 0120160205 dc1

the systematics of boron isotopes in izu arc front volcanic rocks the process of fluid release from the subducting slab beneath the izu arc volcanic front izu vf was examined by measuring b concentrations and b isotope ratios in the neogene fallout tephra odp site 782a both were measured by secondary ion mass spectrometry in a subset of matrix glasses and glassy plagioclase hosted melt inclusions selected from material previously analyzed for major and trace elements glasses and radiogenic isotopes sr nd pb bulk tephra these tephra glasses have high b abundances 10 60 ppm and heavy 11b values 4 5 to 12 0 extending the previously reported range for izu vf rocks 11b 7 0 to 7 3 the glasses show striking negative correlations of 11b with large ion lithophile element lile nb ratios these correlations cannot be explained by mixing two separate slab fluids originating from the subducting sediment and the subducting basaltic crust respectively model a two alternative models models b and c are proposed model b proposes that the inverse correlations are inherited from altered oceanic crust aoc which shows a systematic decrease of b and lile with increasing depth from basaltic layer 2a to layer 3 paralleled by an increase in 11b from 1 to 10 to 24 in this model the contribution of sedimentary b is insignificant 4 of b in the izu vf rocks model c explains the correlation as a mixture of a low 11b 1 composite slab fluid a mixture of metasediment and metabasalt derived fluids with a metasomatized mantle wedge containing elevated b 1 2 ppm and heavy 11b 14 the mantle wedge was likely metasomatized by 11b rich fluids beneath the outer forearc and subsequently down dragged to arc front depths by the descending slab pb b isotope systematics indicate that at arc front depths 53 of the b in the izu vf is derived from the wedge this implies that the heavy 11b values of izu vf rocks are largely a result of fluid fractionation and do not reflect variations in slab source provenance i e subducting sediment vs basaltic crust since the b content of the peridotite at the outer forearc 7 58 ppm b mean 24 16 ppm is much higher than beneath the arc front 1 2 ppm b the hydrated mantle wedge must have released a b rich fluid on its downward path this wedge flux can explain 1 the across arc decrease in b and 11b e g izu kuriles without requiring a progressive decrease in fluid flux from the subducting slab and 2 the thermal structure of volcanic arcs as reflected in the b and 11b variations of volcanic arc rocks

a mechanism for the generation of wave driven rhythmic patterns in the surf zone the coupling between topographic irregularities and wave driven mean water motion in the surf zone is examined this coupling occurs because the topographic perturbations produce excess gradients in the wave radiation stress that cause a steady circulation this circulation in turn creates a sediment transport pattern that can reinforce the bottom disturbance and may thereby lead to the growth of large scale bed forms to investigate this coupling mechanism the linearized stability problem with an originally plane sloping beach and normal wave incidence is solved in two different cases first the breaking line is considered to be fixed and second the perturbations in water depth that produce a displacement of the breaker line are accounted for the first case shows that the basic topography can be unstable with respect to two different modes a giant cusp pattern with shore attached transverse bars that extend across the whole surf zone and a crescentic pattern with alternate shoals and pools at both sides of the breaking line showing a mirroring effect in the second case the varying breaker line may have a strong influence on the circulation this is clear for the giant cusp topography whose growth is totally inhibited in contrast the morphology and the growth of the crescentic pattern remains almost unchanged

attenuation of strong ground motion in canada from a random vibrations approach abstract theoretical relations are developed for the attenuation of horizontal peak ground acceleration pga and velocity pgv in canada with emphasis on eastern canada the theoretical basis is a composite of several approaches at intermediate epicentral distances results from random vibration theory hanks and mcguire 1981 boore 1983 which can be used to describe pga and pgv in terms of shear radiation implied by brune9s 1970 source model are applied to canadian earthquakes motions are extended into the near source region using arguments concerning magnitude scaling joyner and boore 1981 at distances greater than two crustal thicknesses ground motions are attributed largely to the lg phase and are attenuated accordingly nuttli 1982 the resulting attenuation relations for pga and pgv in eastern canada are in excellent agreement with strong motion data from moderate eastern canadian and central united states earthquakes compared to empirical attenuation relationships based on modified mercalli intensity the theoretical model predicts a stronger dependence of peak ground motions on magnitude in other respects amplitude levels and distance decay empirical and theoretical predictions are similar the model predicts that eastern events will have higher peak accelerations but similar peak velocities in comparison to their western counterparts of the same moment magnitude this arises from the relative enrichment of eastern earthquakes in higher frequencies

boron isotopic composition of mud volcano fluids implications for fluid migration in shallow subduction zones abstract mud volcanoes are important conduits for deep fluids to migrate upward providing an important window to study fluid sediment interactions at depth in accretionary prisms fluids emitting from mud volcanoes in southern and eastern taiwan were analyzed for dissolved chemical composition and b isotopes to delineate the sources and chemical alteration occurring during fluid migration concentrations of dissolved major elements cl na k ca mg and so4 in most of the mud volcano fluids were lower than seawater concentrations except for the high ca samples in eastern taiwan which were probably affected by fluids igneous rock interactions the high concentrations of b ba and li in the mud volcano fluids are consistent with a scenario that involves intense sediment alteration and clay dehydration at depth the reaction temperatures estimated using chemical thermometers fall within the range of 70 170 c with some variation by location in nearby mud volcano sites the concentration of dissolved major elements varied little but the b stable isotope compositions varied by as much as 20 supporting the argument that dissolved b concentrations were over printed with effects of sediment adsorption this explains the occurrence of b enriched and heavy 11b fluids at moderate depths in subduction zones it is probable that the fluids in mud volcanoes in taiwan originated from 2 to 5 km depth and are influenced by processes involving tectonic shortening sediment alteration and clay dehydration and subsequent retrograde adsorption during fluid migration

the development of small scale sandy alluvial fans at the base of a modern coastal cliff process observations and implications abstract the development of a series of small scale alluvial fans has been studied at the base of a sandy coastal cliff on the torre del loro beach near huelva southwestern spain these fans are small enough to permit the experimental modification of flow sediment load and morphology elongate sandy debris flow deposits are also present the fans are related to sources with perennial discharges and are fed by solitary shifting distributary channels the fans have radial morphologies and grow by localized lobe building at the intersection point in a mid fan or fan toe position and or by bulk aggradation due to overflow sheet flow sediment dispersal is by channelized or unconfined water flow but also involves slugs of hyperconcentrated flows and occasionally sandy debris flows the radial fans channelized flow dominated have surface slopes of up to 20 their medial segments are often the steepest and sediment at their toes and lateral flanks can be coarser than in the inner zones the elongated sandy debris flow deposits are related to sources with ephemeral discharges and are mass flow dominated these deposits are smaller and are built chiefly by sandflows finger like sandy debris flows their surface slopes are rather uniform but only up to 6 and there is no obvious downfan variation in grain size when regarded as small scale analogues for larger alluvial fans these fans deviate from the textbook models particularly in grain size distribution simultaneity of quiet and energetic processes and longitudinal gradient profile our study indicates that the relationship between fan morphometry and depositional processes still requires a better knowledge

mean bed friction of combined wave current flow abstract bijker s model for evaluating the wave period mean bed friction of combined wave current flow has been modified to account for the current velocity reduction as well as the wave boundary layer near the sea bed a method of estimating the bed frictional dissipation rate of the combined flow is also presented the results obtained by the present approach are compared with several sets of experimental data and confirm its accuracy and usefulness

spatial variability and attenuation of arias intensity during the 1999 chi chi mw 7 6 earthquake taiwan arias intensity is a measure of earthquake intensity that captures the potential destructiveness of an earthquake using the strong ground motion records of the m w 7 6 chi chi earthquake taiwan we analyze the spatial distribution of the vertical horizontal fault parallel and fault normal components of the arias intensity we investigate the effects of the hanging wall and footwall on ground motions and develop a relationship between arias intensity and peak ground acceleration pga incorporating the influence of local site conditions we also evaluate the applicability of some widely used arias intensity attenuation relationships by comparing the observed values with empirical estimates our results show the vertical arias intensity is generally lower than the horizontal component with nearly 90 of the vertical to horizontal ratios between 0 1 and 0 6 during this typical reverse mechanism earthquake the fault normal component of the arias intensity is approximately 20 higher than the fault parallel component for sites within 40 km of the fault arias intensities on the hanging wall are systematically higher than those on the footwall indicating clear hanging wall effects site conditions influence the correlation between arias intensity and pga arias intensity shows a good correlation with pga and v s 30 arias intensity increases with increasing pga and decreasing v s 30 the arias intensities observed within 40 km of site class c locations and within 80 km of site class d locations are generally lower than the mean estimates from empirical predictions in contrast at distances of 80 km from site class d locations the observed arias intensities are much larger than the empirical predictions as a result of site amplification considering the variability of ground motion between earthquakes the attenuation model of travasarou et al 2003 model 4 of stafford et al 2009 and the model of lee et al 2012 provide a good fit with observations from the chi chi earthquake online material table of station coordinates fault distances footwall hanging wall indicator site classes v s 30 and measured arias intensities

morphodynamic modelling of rip channel growth the morphological evolution of a rip channel system due to normally incident waves has been investigated using two different approaches the first approach is a state of the art commercial 2dh coastal area model whereas the second approach is a linear stability analysis the results of the two different approaches have been compared and both models predict rip channel spacings and initial growth rates of similar magnitudes

self organization mechanisms for the formation of nearshore crescentic and transverse sand bars the formation and development of transverse and crescentic sand bars in the coastal marine environment has been investigated by means of a nonlinear numerical model based on the shallow water equations and on a simplified sediment transport parameterization by assuming normally approaching waves and a saturated surf zone rhythmic patterns develop from a planar slope where random perturbations of small amplitude have been superimposed two types of bedforms appear one is a crescentic bar pattern centred around the breakpoint and the other herein modelled for the first time is a transverse bar pattern the feedback mechanism related to the formation and development of the patterns can be explained by coupling the water and sediment conservation equations basically the waves stir up the sediment and keep it in suspension with a certain cross shore distribution of depth averaged concentration then a current flowing with against the gradient of sediment concentration produces erosion deposition it is shown that inside the surf zone these currents may occur due to the wave refraction and to the redistribution of wave breaking produced by the growing bedforms numerical simulations have been performed in order to understand the sensitivity of the pattern formation to the parameterization and to relate the hydro morphodynamic input conditions to which of the patterns develops it is suggested that crescentic bar growth would be favoured by high energy conditions and fine sediment while transverse bars would grow for milder waves and coarser sediment in intermediate conditions mixed patterns may occur

stochastic prediction of ground motion and spectral response parameters at hard rock sites in eastern north america empirical predictions of ground motions from large eastern north american earthquakes are hampered by a lack of data for such events for this reason most prediction techniques have been based at least in part on data from the seismically active and well instrumented western north america concentrating on the prediction of response spectra on hard rock sites we have used a relatively new theoretical technique that does not require western data to make ground motion predictions for eastern north america this method often referred to as the stochastic model has its origins in the work of hanks and mcguire who treat high frequency motions as filtered random gaussian noise for which the filter parameters are determined by a seismological model of both the source and the wave propagation the model has been successfully applied to the predictions of ground motions in the western united states and to short period magnitudes from large to great earthquakes worldwide for our application the essential parameters of the model are estimated by using existing data from small to moderate eastern north american earthquakes a crucial part of the model is the relation between seismic moment and corner frequency the relation proposed in 1983 by nuttli for mid plate earthquakes leads to predictions of ground motions that are lower than available data by a factor of about 4 on the other hand a constant stress parameter of 100 bars gives model predictions in good accord with the data to aid in applications the ground motion predictions are given in the form of regression equations for earthquakes of magnitude 4 5 to 7 5 at distances within 100 km of the source the explanatory variables are hypocentral distance and moment magnitude m because predictions are often required in terms of m g rather than m we have used the theoretical model to establish a relation between the two magnitudes the predicted relation agrees with the sparse data available although the large uncertainties in the observed magnitudes for the larger events as well as the sensitivity of the theoretical magnitude to the attenuation model make it difficult to discriminate between various source scaling models

the fate of subducted oceanic slabs in the shallow mantle insights from boron isotopes and light element composition of metasomatized blueschists from the mariana forearc abstract serpentine muds from south chamorro seamount scs drilled during odp leg 195 at site 1200 contain metamafic clasts that experienced blueschist facies metamorphism including the critical mineral assemblage pumpellyite na amphibole epidote these schists represent fragments from the actual slab mantle interface at 27 km depth their heterogeneous lithology with a metasomatic character indicates significant mobility of major elements in the mariana forearc a region of melange formation as it can also be observed in onland exposures such as the catalina schist as the mariana forearc blueschists show no late stage alteration they permit the direct study of material transfer during the subduction processes at an active convergent margin this study presents the first data of detailed b isotope 11 b and light element variations in blueschist facies minerals from the mariana arc system the primary foci are b and li concentrations and 11 b values analyzed by sims and tof sims techniques minerals such as na rich amphibole phengite and chlorite are found to be strongly enriched in li up to 70 g g be up to 8 g g and b up to 35 g g and with 11 b values of 6 4 these new data are consistent with isotopically heavy b being released into the mariana forearc mantle wedge serpentinization of dry mantle peridotite after interaction with b rich slab released high ph fluids and confirm models of significant b loss and b isotope fractionation during forearc shallow slab dehydration the elevated li be and b concentrations in minerals that comprise the bulk of the rocks namely amphibole phengite and chlorite bear a strong potential to further transport li and b as well as the isotopically light component of b to greater depths in the mantle where ongoing metamorphism is responsible for further isotope and elemental fractionation and the formation of distinct mantle reservoirs e g volcanic arc and oceanic intra plate oib magmas

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

on beach cusp formation a system of shallow water equations and a bed evolution equation are used to examine the evolution of perturbations on an erodible initially plane beach subject to normal wave incidence both a permeable under darcy s law and an impermeable beach are considered it is found that alongshore periodic morphological features reminiscent of swash beach cusps form after a number of incident wave periods on both beaches on the permeable impermeable beach these patterns are accretional erosional in both cases flow is horn divergent spacings of the cusps are consistent with observations and are close to those provided by a standing synchronous linear edge wave an analysis of the processes leading to bed change is presented two physical mechanisms are identified concentration gradient and flow divergence which are dominant in the lower and upper swash respectively and their difference over a wave cycle leads to erosion or deposition on an impermeable beach infiltration enters this balance in the upper swash a bed wave of elevation is shown to advance up the beach at the tip of the uprush with a smaller wave of depression on the backwash it is found that cusp horns can grow by a positive feedback mechanism stemming from decreased increased backwash on positive negative bed perturbations

an efficient solver for nearshore flows based on the waf method abstract we describe an efficient and robust flow solver for the integration of the classic nonlinear shallow water equations nswe on a beach of arbitrary topography on the basis of the shock capturing weighted average flux waf method a numerical code is implemented which employs a space splitting technique to integrate the nswe over a horizontally two dimensional domain 2dh special care is put in handling the moving shoreline and a new efficient formulation of the shoreline boundary conditions is presented this is based on the hydrodynamic equivalent of the cavitation condition used in gas dynamics model capabilities are illustrated by means of a number of tests both 1dh and 2dh these reveal that though primarily conceived for modelling nearshore hydrodynamics the solver can be successfully adopted even for studying the run up of large tsunami waves

secular boron isotope variations in the continental crust an ion microprobe study abstract tourmalines of various chemical compositions hosted in magmatic rocks with ages ranging from 3 8 ga to the present were analysed for 11 b by ion microprobe a large range of 11 b values from 2 to 30 1 5 was observed the 11 b values are correlated with the chemical composition of the tourmalines the li rich tourmalines being enriched in 11 b compared to fe and or mg rich tourmalines this may reflect mixing in the continental crust between a marine reservoir characterized by high li contents and 11 b values and a continental reservoir characterized by low li contents and 11 b values no relationship between the age and the 11 b values is observed for the fe or for the mg rich tourmalines in contrast the 11 b values of the li rich tourmalines show a tendency to regularly decrease with increasing age this pattern is consistent with a simple model of constant boron isotopic fractionation between seawater and the continental crust during the progressive extraction of the continents a variation in the mean 11 b value of the continental crust from 20 ga ago to 7 at present is predicted by the model the largest variation occurred during the first 2 5 ga

boron isotope insights into the origin of subduction signatures in continent continent collision zone volcanism abstract we present the first boron abundance and 11 b data for young 1 5 0 ma volcanic rocks formed in an active continent continent collision zone the 11 b of post collisional volcanic rocks 5 to 2 from the armenian sector of the arabia eurasia collision zone are heavier than mid ocean ridge basalts morb confirming trace element and isotope evidence for their derivation from a subduction modified mantle source based on the low b nb 0 03 0 25 vs 0 2 90 in arc magmas as well as low ba th and pb ce this source records a subduction signature which is presently fluid mobile element depleted relative to most arc settings the heavier than morb 11 b of post collision volcanic rocks argues against derivation of their subduction signature from a stalled slab which would be expected to produce a component with a lighter than morb 11 b due to previous fluid depletion instead the similarity of 11 b in plio pleistocene post collision to 41 ma alkaline igneous rocks also from armenia and also presented in this study suggests that the subduction signature is inherited from mesozoic paleogene subduction of neotethys oceanic slabs the slab component is then stored in the mantle lithosphere in amphibole which is consistent with the low b in both armenian volcanic rocks and metasomatic amphibole in mantle xenoliths based on trace element and radiogenic isotope systematics this slab component is thought to be dominated by sediment melts or supercritical fluids previously published 11 b of metasediments suggests a sediment derived metasomatic agent could produce the b isotope composition observed in armenian volcanic rocks the lack of evidence for aqueous fluids preserved over the 40 myr since initial collision supports observations that this latter component is transitory while the lifetime of sediment melts supercritical fluids can be extended to 40 myr

attenuation relations of strong ground motion in japan using site classification based on predominant period a spectral acceleration attenuation model for japan is presented in the present study the data set includes a very large number of strong ground motion records up to the 2003 off tokach main and aftershocks site class terms instead of individual site correction terms are used the site classes of recording stations are from a recent study on site classification for strong motion recording stations in japan according to a classification scheme that has been used in japanese engineering design the use of site class terms enables tectonic source type effects to be identified and accounted for in the present model the effects of a faulting mechanism for crustal earthquakes also are accounted for for crustal and interface earthquakes a simple form of an attenuation model with respect to distance is able to capture the main strong motion characteristics and achieves unbiased estimates for subduction slab events a simple distance modification factor is employed to achieve plausible and unbiased predictions the effects of source depth tectonic source type and faulting mechanism of crustal earthquakes are significant the need for magnitude squared terms is evaluated and the use of magnitude squared terms reduces the interevent error further

ground motion attenuation relationship for east central iran predictive attenuation relationships have been developed for peak ground acceleration and spectral coordinates based on observed and simulated records for east central iran first the predictive relationships are derived based on observed records the observed data set which was considered includes a total of 258 records from 109 earthquakes with a magnitude range of 5 0 7 4 on rock site then a suite of ground motions has been simulated for a range of magnitude and distances based on the stochastic finite fault ground motion model the theoretical empirical attenuation relationship which has been developed for the horizontal component of peak ground acceleration and spectral acceleration is applicable to earthquakes of m w 5 0 7 4 at a distance up to 100 km online material earthquake catalog

source composition and distribution of the fluid in the kurile mantle wedge constraints from across arc variations of b nb and b isotopes b and nb concentrations and b isotope composition were determined for lavas covering the entire length of the kurile arc b nb and 11b of these lavas show clear across arc variations in which both are highest at the trench side and continuously decrease as the slab depth increases b nb in the volcanic front lavas 8 25 is significantly higher than those of morb and oib indicating that the mantle wedge is extensively metasomatized by b rich fluid derived from the subducting slab the frontal 11b values are also out of the range of morb and oib and systematic difference exists between northern kurile nk 5 4 0 5 and central and southern kurile csk 4 3 0 3 however these two parameters approach or coincide with mantle values at the most back arc side the 11b and 87sr 86sr linearly correlate with nb b suggesting control by simple mixing of two isotopically homogeneous components that is slab derived fluid and mantle wedge the estimated 11b and 87sr 86sr of the fluid are 7 0 0 6 and 0 70326 0 00005 for nk and 6 3 0 3 and 0 7033 for csk respectively these fluid compositions are consistent with a source constituted by 95 altered oceanic crust and 5 oceanic sediment with the slight difference between nk and csk resulting from the different lithologies of subducting sediments the mantle wedge beneath the kurile arc has b sr and nd isotope compositions identical with morb but shows significantly higher b nb the above trends bear a close resemblance to those observed in the izu arc strongly suggesting their universality in the arc system the across arc decline of b nb observed both in kurile and izu implies that the fluid flux from the slab continuously decreases as the slab depth increases however this relates only to a final stage of slab dehydration since most of the volatile components are lost at the fore arc region in contrast to b k is uniformly enriched across the arc this requires control by a k bearing mineral phase either in the slab phengite or the mantle wedge phlogopite although such a mineral is responsible for only a small part of the whole fluid transport

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

investigation of a self organization model for beach cusp formation and development a recent numerical investigation of self organization werner and fink 1993 suggests that the feedback process between currents and sediment response can result in self organized patterns and can be used to predict beach cusp formation and spacing a similar model based on self organization is tested here in order to understand the processes occurring during beach cusp formation and development to evaluate the sensitivity toward the parameters used and to examine how the model might relate to field observations results obtained confirm the validity of the self organization approach and its capacity to predict beach cusp spacing with values in fair agreement with the available field measurements with most of the input parameters primarily affecting the rate of the process rather than the final spacing however changes in the random seed and runs for large numbers of swash cycles reveal a dynamical system with significant unpredictable behavior cusp spacing tends to change with time and cusp regularity shows large long term variations cusps are found to be accretionary in the swash zone and in agreement with most observations mean flows are horn divergent over developed topography simulations over nonplanar slopes characterized by the presence of preexisting nonrhythmic or cuspate features have been performed results indicate that preexisting large amplitude cusps are destroyed if their spacing is substantially different from that expected under self organization and that the final spacing is consistent with that predicted by the model for an equivalent plane beach these findings support the hypothesis that self organization is a robust mechanism for beach cusp formation

modelling morphological processes in the vicinity of shore parallel breakwaters abstract a coastal area morphological modelling system is used to investigate the planform development tombolo or salient behind a single surface piercing detached breakwater a quasi three dimensional q3d description of the flow and the sediment transport together with a revised bed level update scheme were incorporated recently in the morphological modelling suite applied in the present investigation the q3d sediment transport formulation used allows simulating beach profile evolution and planform development simultaneously several breakwater layouts were investigated in a series of tests in which the incident wave condition was taken as constant in time the investigation was done for surface piercing shore parallel breakwaters in a non tidal environment the morphological simulation results for the planform shape agree qualitatively with field observations and predictions from empirical rules using the simulation results simple design curves for surface piercing breakwaters are derived the importance of properly accounting for the influence of wave diffraction when modelling sediment transport and morphology in the vicinity of shore parallel structures is also investigated the present paper summarises much of the work performed at dhi water environment over the past 10 years within the field of coastal area morphological modelling

isotopic and elemental partitioning of boron between hydrous fluid and silicate melt the fractionation of b and its isotopes between aqueous fluid and silicate melt has been studied from 550 to 1100 c and 100 500 mpa fluid melt partition coefficients are 1 for rhyolite melt this shows that b is not always strongly extracted from melts into hydrous fluids boron isotopic fractionation is large compared with the carbon and oxygen stable isotopic systems especially at high t and is most simply explained by differences in coordination trigonal vs tetrahedral among coexisting phases combined with earlier measurements on illite water 300 350 c b isotopic fractionation defines a temperature dependent trend from 300 to 1100 c because of the large magnitude and apparent low sensitivity to bulk composition b isotopic fractionation can be readily applied to studies of diagenesis hydrothermal alteration of planetary bodies subduction zone processing and arc magma generation and magma chamber evolution

rip current review rip currents are shore normal narrow seaward flowing currents that originate within surf zone extend seaward of the breaking region rip head and can obtain relatively high velocities within the last decade there have been a significant number of laboratory and field observations within rip current systems an overview of rip current kinematics based on these observations and the scientific advances obtained from these efforts are synthesized rip current flows are partitioned into mean infragravity very low frequency vorticity and tidal contributions and it is found that each contributes significantly to the total data from the laboratory and the field suggest that the rip current strength increases with increasing wave energy and decreasing water depths the maximum mean current occurs inside the surf zone where the maximum forcing is present owing to the dissipation of waves

a 2d numerical model of wave run up and overtopping a two dimensional 2d numerical model of wave run up and overtopping is presented the model called ott 2d is based on the 2d nonlinear shallow water nlsw equations on a sloping bed including bed shear stress these equations are solved using an upwind finite volume technique and a hierarchical cartesian adaptive mesh refinement amr algorithm the 2d nature of the model means that it can be used to simulate wave transformation run up overtopping and regeneration by obliquely incident and multi directional waves over alongshore inhomogeneous sea walls and complex submerged or surface piercing features the numerical technique used includes accurate shock modeling and uses no special shoreline tracking algorithm or shoreline coordinate transformation which means that noncontiguous flows and multiple shorelines can easily be simulated the adaptivity of the model ensures that only those parts of the flow that require higher resolution such as the region of the moving shoreline receive it resulting in a model with a high level of efficiency the model is shown to accurately reproduce analytical and benchmark numerical solutions existing wave flume and wave basin datasets are used to test the ability of the model to approximate 1d and 2d wave transformation run up and overtopping finally we study a 2d dataset of overtopping of random waves at off normal incidence to investigate overtopping of a sea wall by long crested waves the data set is interesting as it has not been studied in detail before and suggests that in some instances overtopping at an angle can lead to more flooding than at normal incidence

boron partitioning in the upper mantle an experimental and ion probe study piston cylinder experiments were performed on two natural spinel lherzolites from lherz french pyrenees and kilbourne hole usa in order to determine the distribution coefficients of boron between minerals and melt for upper mantle conditions additionally a morb glass and its phenocrysts were taken as a low pressure analogue boron concentration measurements were made by ion probe the only technique suitable for in situ 10 m boron concentration measurements in the range 0 1 1 ppm the two starting peridotites samples have low bulk boron concentrations of 0 96 and 0 81 ppm boron distribution coefficients were determined from 1 direct measurement of melt and crystals in contact and 2 calculations from profiles of several tens of measurements made using 10 m diameter spots containing variable proportions of crystals and melt distribution coefficients between minerals and melt decrease in the following order dcpx melt 0 117 dsp melt 0 08 dol melt 0 034 dopx melt 0 027 the limited ranges of composition pressure and temperature investigated mimic natural conditions for basalt genesis but sharply limit the present data for determining variations of partition coefficients with p t and x however boron behavior seems to follow roughly that of aluminum since the al richest minerals are the ones with the highest boron distribution coefficients the dol melt values increase with pressure which is similar to what has been observed for the distribution coefficient of aluminum between olivine and melt boron is therefore strongly incompatible during partial melting in the mantle using these distribution coefficients and assuming that morb have been produced by 5 20 partial melting the depleted mantle source of morb is estimated to contain 0 05 0 3 ppm b these values correspond to the lower limit for the mean boron content of chondrites 0 55 0 3 ppm but are in accordance with a simple budget of boron between mantle crust and seawater in fact a simple mass balance calculation where all the boron hosted in the crust and in seawater is presumed to have been extracted from an upper mantle of chondritic original boron content yields a boron content for the depleted upper mantle of 0 3 ppm at present because in situ boron concentration measurements under the ppm level at the m scale are now possible with the ion probe and because of its strong partitioning in melts and possible partitioning in fluids boron is a potentially very powerful geochemical tracer for the study of mantle processes such as basalt genesis or metasomatism

numerical simulation of wave overtopping of coastal structures using the non linear shallow water equations a one dimensional high resolution finite volume model capable of simulating storm waves propagating in the coastal surf zone and overtopping a sea wall is presented the model amazon is based on solving the non linear shallow water nlsw equations a modern upwind scheme of the godunov type using an hll approximate riemann solver is described which captures bore waves in both transcritical and supercritical flows by employing a finite volume formulation the method can be implemented on an irregular structured boundary fitted computational mesh the use of the nlsw equations to model wave overtopping is computationally efficient and practically flexible though the detailed structure of wave breaking is of course ignored it is shown that wave overtopping at a vertical wall may also be approximately modelled by representing the wall as a steep bed slope the amazon model solutions have been compared with analytical solutions and laboratory data for wave overtopping at sloping and vertical seawalls and good agreement has been found the model requires more verification tests for irregular waves before its application as a generic design tool

landscapes on the edge examining the role of climatic interactions in shaping coastal watersheds using a coastal terrestrial landscape evolution model incised coastal gullies icgs are dynamic features found at the terrestrial coastal interface their geomorphic evolution is driven by the interactions between processes of fluvial knickpoint migration and coastal cliff erosion under scenarios of future climate change the frequency and magnitude of the climatological drivers of both terrestrial fluvial and hillslope and coastal cliff erosion processes are likely to change with an adjunct impact on these types of coastal features here we explore the response of an incised coastal gully to changes in both terrestrial and coastal climate in order to elucidate the key process interactions which drive icg evolution we modify an extant landscape evolution model child to incorporate processes of soft cliff erosion this modified version termed the coastal terrestrial child ct child model is then employed to explore the interactions between changing terrestrial and coastal driving forces on the future evolution of an icg found on the south west isle of wight uk it was found that the magnitude and frequency of storm events will play a key role in determining the future trajectory of icgs highlighting a need to understand the role of event sequencing in future projections of landscape evolution furthermore synergistic positive and antagonistic negative interactions were identified between coastal and terrestrial parameters such as wave height intensity and precipitation duration which act to modulate the impact of changes in any one parameter of note was the role played by wave height intensity in driving coastal erosion which was found to play a more important role than sea level rise in determining rates of coastal erosion this highlights the need for a greater focus on wave height in studies of soft cliff erosion this article is protected by copyright all rights reserved

melt production beneath mt shasta from boron data in primitive melt inclusions most arc magmas are thought to be generated by partial melting of the mantle wedge induced by infiltration of slab derived fluids however partial melting of subducting oceanic crust has also been proposed to contribute to the melt generation process especially when young and hot lithosphere is being subducted the isotopic composition of boron measured in situ in olivine hosted primitive melt inclusions in a basaltic andesite from mt shasta california is characterized by large negative values that are also highly variable delta 11 b 21 3 to 0 9 per mil the boron concentrations from 0 7 to 1 6 parts per million are lower than in most other arc lavas the relation between concentration and isotopic composition of boron observed here supports a hypothesis that materials left after dehydration of the subducting slab may have contributed to the generation of basaltic andesite lavas at mt shasta

process based modelling of a shoreface nourishment abstract a state of the art process based model is applied to hindcast the morphological development of a shoreface nourishment along the barrier island of terschelling the netherlands the applied morphodynamic model is delft3d for fully three dimensional flow and sediment transport in coastal environments owing to a complex geomorphological setting of the study area the curvi linear model includes adjacent tidal inlets and covers 40 70 km with an increasing grid size resolution towards the nourishment site in the center of the island in 1993 a total of 2 mm3 of sand was supplied to the nearshore bar zone off terschelling filling up the trough between the middle and outer bar by spring 1994 most of the nourished sediment had been redistributed onshore and welded onto the middle bar where it remained in the following years the morphodynamic model is applied to the prediction of this rapid nearshore profile behaviour the calibration of the model against an extensive set of full scale hydrodynamic data at several locations throughout the nearshore bar zone shows a good representation of the measured hydrodynamics morphodynamic results show a dependency on spatial scale on the scale of precise bed level evolution with respect to bar migration and growth model predictions are poor as the nearshore bars are predicted to flatten out resorting to bulk volumes integrated over larger spatial scales the model clearly has skill in predicting the overall effects of the nourishment the lack of phase shift between sediment transport and bathymetry is identified as the key controlling factor for the poor sandbar predictions

an investigation into earthquake ground motion characteristics in eastern north america abstract a random vibration model of the hanks mcguire type is used to predict peak ground motions at rock sites in eastern north america the assumed geometric decay and distance dependent duration approximate the propagation of direct body waves at short distances and lg waves at regional distances the model predicts peak acceleration and velocities as well as response spectra and magnitude for a given seismic moment and corner frequency to predict ground motions for a given lg magnitude m lg the model is first used to calculate the seismic moment corresponding to that magnitude assuming a source scaling law then knowing the moment and corner frequency the model is used to calculate peak ground motions available data from strong motion recordings and from the ectn and lrsm networks modified to estimate horizontal ground motions on rock where appropriate are used to verify the model9s assumption and predictions modified mercalli intensity data are also used ground motions predicted by the model with a stress drop of 50 to 200 bars agree with the ground motion data but the m lg values computed by the model for given seismic moments do not agree with nuttli9s 1983 moment versus m lg data for large earthquakes resolution of the latter disagreement awaits the collection of instrumental data from large events in eastern north america

bed load sediment transport on steep longitudinal slopes the results of new experiments on bed load transport on steep longitudinal slopes are presented the experiments were carried out in a large tilting duct with a fine sand median grain diameter of 208 micro m covering the range of slope angles beta of angle of repose for the sand phi sub s of 32 deg 0 56 rad measurements included bed shear stress flow discharge and the sediment pickup rate on slopes the results suggest that existing theories for bed load transport on slopes are not adequate for all bed slopes and the new data are used to formulate a semiempirical relation that satisfactorily predicts the transport rate on horizontal as well as mild and steep slopes the following are two important findings correcting the threshold term for slope in the meyer peter and muller formula adequately describes the transport rate on positive slopes elevation increasing in direction of flow and on small negative slopes while on steeper negative slopes an extra correction term is required although the value of beta phi sub s at which this term becomes necessary is a function of shear stress and the influence of slope vanishes at high shear stresses

attenuation of high frequency p and s waves in the crust of the east central iran summary we simultaneously estimated qp 1 and qs 1 by applying the extended coda normalization method at 39 stations of three local networks in the east central iran we measured frequencydependent attenuation of both p and s waves for the frequency range of 1 5 3 0 6 0 12 and 24 hz we have analysed 266 three component seismograms of 53 local earthquakes having focal depths less than 25 km which occurred from 2003 december 28 to 2005 april 11 by fitting power law frequency dependence to the estimated values over the whole stations we obtained qp 1 25 3 10 3 f 0 99 0 04 and qs 1 19 2 10 3 f 1 02 0 06 in the upper crust of the east central iran where f is frequency in hz our results are in the range of those estimated for qp 1 and qs 1 of the other seismically active regions

boron isotopic composition of subduction zone metamorphic rocks abstract many arc lavas contain material derived from subducted oceanic crust and sediments but it remains unresolved whether this distinctive geochemical signature is transferred from the subducting slab by aqueous fluids silicate melts or both boron isotopic measurements have the potential to distinguish between slab transfer mechanisms because 11 b fractionates preferentially into aqueous fluids whereas little fractionation may occur during partial melting previous studies have shown that 11 b values of island arc lavas 6 to 7 overlap the range of 11 b values for altered oceanic crust 5 to 25 and pelagic sediments and turbidites 7 to 11 secondary ion mass spectrometry sims analyses of minerals in subduction zone metamorphic rocks yield 11 b 11 to 3 suggesting that slab dehydration reactions significantly lower the 11 b values of subducted oceanic crust and sediments in order to explain the higher 11 b values reported for arc lavas as compared to subduction zone metamorphic rocks the b bearing component derived from the metamorphosed slab must be enriched in 11 b relative to the slab favoring an aqueous fluid as the slab transfer mechanism