stage discharge assessment in compound meandering channels discharge measurements for overbank flow were carried out in a two stage meandering channel with various bed slopes sinuosities and water depths the effect of bed slope and sinuosity on discharge was found to be significant a simple design equation for the conveyance capacity based on dimensional analysis is proposed this equation may be used to estimate the stage discharge curve in a meandering channel with overbank flow predictions of discharge using existing methods and the proposed method are compared and tested against the new measured discharge data and other available overbank data the strengths and weaknesses of the various methods are discussed

the effect of floodplain grass on the flow characteristics of meandering compound channels abstract laboratory experiments were conducted in a large scale meandering compound channel to investigate the effect of floodplain grass on the main flow field in the channel three dimensional velocity fields turbulences and reynolds shear stresses were measured along half a meander the experiments revealed that flexible artificial grass planted on a floodplain can significantly reduce the conveyance capability of the entire channel two parallel stage discharge curves increased with increasing flow depth the additional resistance of the floodplain grass increased the streamwise velocity and conveyance in the main channel along a meander an analysis of the generation mechanism of secondary flows in the main channel indicated that the secondary current consisted of an enhanced original secondary cell that was strengthened by the centrifugal force and a component of the upstream floodplain flow the relative dominance of these two components in the secondary flows was primarily determined by the angle between the floodplain flow and the main channel ridge and also the floodplain roughness at the same flow depth the secondary flow in cases with grass on the floodplain was generally stronger than that in the case of a smooth meander bend although it was weaker near the middle cross over section floodplain grass enhanced the intensity of the lateral turbulence above the bankfull level and significantly modified the turbulence structure although it had a negligible effect on the vertical turbulence except at the bend entrance floodplain grass also affected the reynolds shear stresses in the main channel generating stronger lateral shear stresses at a low flow depth in contrast at a high flow depth the distribution of the interface shear stresses changed entirely while its magnitude remained the same when the floodplains were grassed the vertical shear stress that was induced by secondary flows was greater at the apexes but reduced at the cross over sections these observations highlight the important effects of floodplain grass on the main channel flow

pacific interdecadal variability in this century s sea surface temperatures analysis of this century s sea surface temperatures over the pacific ocean reveals an interdecadal oscillation with a period of 15 20 years our results show that the well known 1976 77 climate regime shift is not unique but represents one of several phase transitions associated with this interdecadal oscillation also found around 1924 25 1941 42 and 1957 58 the oscillation s striking north south symmetry across the equator implies strong interactions between tropics and extratropics a mode with a period of approximately 70 years and an apparently different spatial pattern is also identified tentatively but has to be evaluated further using longer time series

decadal biogeochemical changes in the subtropical indian ocean associated with subantarctic mode water within the subantarctic mode water samw density level we study temporal changes in salinity nutrients oxygen and ttd transit time distribution ages in the western w and eastern e subtropical gyre of the indian ocean io from 1987 to 2002 additionally changes in total alkalinity ta and dissolved inorganic carbon dic are evaluated between 1995 and 2002 the mechanisms behind the detected changes are discussed along with the results from a hindcast model run community climate system model the increasing salinity and decreasing oxygen trends from 1960 to 1987 reversed from 1987 to 2002 along the gyre in the w io a decreasing trend in ttd ages points to a faster delivery of samw thus less biogenic matter remineralization explaining the oxygen increase and noisier nutrients decrease in the e io samw no change in ttd ages was detected therefore the trends in oxygen and inorganic nutrients relate to changes in the antarctic surface water transported into the e io samw formation area in the w io between 1995 and 2002 the dic increase is equal or even less than the anthropogenic input as the reduction in remineralization contributes to mask the increasing trend in the e io between 1995 and 2002 dic decreases slightly despite the increase in the anthropogenic input differences in the preformed e io samw conditions would explain this behavior trends in the w and e io samw are decoupled and related to different forcing mechanisms in the two main sites of samw formation in the io at 40 s 70 e and 45 s 90 e respectively

a two dimensional morphodynamic model of gravel bed river with floodplain vegetation artificially straight river channels tend to be unstable and ultimately develop into river meanders through bank erosion and point bar deposition in this paper account is taken of the effects of riparian and floodplain vegetation on bank strength floodplain flow resistance shear stress partitioning and bedload transport this is incorporated into an existing 2d hydrodynamic morphological model by applying the new model to an initially straight and single threaded channel the way that its planform and cross sectional geometry evolve for different hydraulic and floodplain vegetation conditions is demonstrated the results show the formation and upstream migration of gravel bars confluence scouring and the development of meandering and braiding channel patterns in cases where the channel becomes unstable the instability grows out of bar formation the resulting braiding patterns are similar to analytical results the formation of a transition configuration requires a strong influence from vegetation copyright 2010 john wiley sons ltd

spatial and temporal deformation along the northern san jacinto fault southern california implications for slip rates the san timoteo badlands is an area of uplift and erosional dissection that has formed as a result of late quaternary uplift along a restraining bend in the san jacinto fault of the san andreas fault system in southern california this bend currently is located in a region where late quaternary deposits and associated surfaces have formed in lower san timoteo canyon we have used morphometric analysis of these surfaces in conjunction with computer modeling of deformational patterns along the san jacinto fault to reconstruct spatial and temporal variations in uplift along the bend morphometric techniques used include envelope subenvelope map ping a gradient length index along channels and denudation values age control is determined using a combination of thermoluminescence tl and near infrared op tical simulation luminescence dating irosl and correlation of soil development indices these approaches are combined with an elastic half space model used to determine the deformation associated with the fault bend the region of modeled uplift has a similar distribution as that determined by morphometric techniques luminescence dates and soil correlation age estimates generally agree based on soil development surfaces within the study area were stabilized at approximately 300 700 ka for q3 43 67 ka for q2 and 27 5 67 ka for q1 luminescence ages both tl and irosl for the formation of the younger two surfaces are 58 to 94 ka for q2 and 37 to 62 ka for q1 ages reported to 1r uncertainty periods of uplift were determined for the surfaces in the study area resulting in approximate uplift rates of 0 34 to 0 84 m ka for the past 100 ka and 0 13 to 1 00 m ka for the past 66 ka comparison of these rates of uplift to those generated by the model support a higher rate of lateral slip along the san jacinto fault than commonly assumed greater than 20 mm yr as compared to 8 12 mm yr commonly cited this higher slip rate supports the proposal that a greater amount of slip has transferred from the san andreas fault to the san jacinto fault than generally held the san jacinto fault may have accommodated a significant portion of the plate boundary slip during the past 100 ka

seismotectonics of the san andreas fault system between point arena and cape mendocino in northern california implications for the development and evolution of a young transform the northernmost and relatively youthful segment of the san andreas fault system is situated within a 100 km wide zone of northwest trending strike slip faults that includes from west to east the san andreas maacama and bartlett springs faults although the san andreas fault is the principal strike slip fault in this system it has been virtually aseismic since the 1906 earthquake moderate levels of seismicity locate to the east along the maacama fault and to a lesser extent the bartlett springs fault at focal depths typical of other strike slip faults within the san andreas fault system in central california north of the san andreas fault system within the cape mendocino area earthquakes occur at depths of up to 40 km and primarily reflect internal deformation of the subducting gorda slab and slip along the mendocino fracture zone seismicity along the maacama and bartlett springs faults is dominated by right lateral to oblique reverse slip along fault planes that dip 50 75 to the northeast the northern extent of seismicity along these faults terminates near the surface projection of the southern edge of the gorda slab the onset of seismicity along these faults may be related to the abrupt change in the elastic thickness of the north american plate as it enters the asthenospheric window the maacama and bartlett springs faults are strike parallel with active reverse faults within the forearc region of the cascadia subduction zone this preexisting structural fabric of northwest trending reverse faults in the forearc area appears to have strongly influenced the initial slip and complexity of these faults continuation of the moderately dipping maacama fault to the southeast along the steeply dipping healdsburg and rodgers creek fault zones and the near vertical hayward and calaveras fault zones in the san francisco bay area suggests that these faults evolve toward a more vertical dip to minimize the shear stresses that tend to resist plate motion

velocity distribution characteristics in meandering compound channels with one sided vegetated floodplains abstract to discuss the effects of asymmetrically vegetated floodplains on the velocity distribution characteristics and discharge capacity of a meandering main channel in this paper continuous river bend models with smooth floodplains and one sided vegetated floodplains were designed in a generalized way three dimensional instantaneous velocity data were obtained with an acoustic doppler velocimeter adv and the velocity distribution characteristics and discharge capacities of the generalized models were compared compared with the smooth floodplain conditions the one sided vegetated floodplain conditions are associated with lower cross sectional average velocities lower ratios of main channel discharge to total discharge near the bending apexes with minimal extension of vegetated floodplain but higher ratios near the bending apex with maximal extension of vegetated floodplain the deflection degrees of depth averaged velocities in the meandering main channel are related to the cross sectional position relative depth and floodplain vegetation the depth averaged velocities near the bending apexes are inclined towards the main channel concave sides those in the upstream crossover area are generally inclined towards the vegetated side and those in the downstream crossover area are obviously inclined towards the smooth side for a given relative depth the deflection degrees near the bending apexes are smaller than those in the crossover areas the deflection degrees near the bending apexes with minimal extension of vegetated floodplain are smaller than those under smooth floodplain conditions but the deflection degrees near the bending apex with maximal extension of vegetated floodplain are obviously larger than the corresponding values under smooth floodplain conditions near the bending apexes the longitudinal depth averaged velocities are higher close to the main channel convex side and lower adjacent to the concave side when the relative depth is small one sided vegetated floodplain conditions feature larger transverse gradients of the cross sectional longitudinal depth averaged velocities near the bending apexes with minimal extension of vegetated floodplain when the relative depth is large the transverse gradients near the bending apexes with minimal extension of vegetated floodplain are all much smaller than the corresponding values of the smooth floodplain conditions however near the bending apex with maximal extension of vegetated floodplain there are no significant differences concerning the transverse gradients of the cross sectional longitudinal depth averaged velocities under the both floodplain conditions one sided vegetated floodplain conditions significantly influence the longitudinal velocity distributions in the meandering main channel for a given relative depth the longitudinal velocities at the cross sectional positions under one sided vegetated floodplain conditions are lower than those under smooth floodplain conditions to varying extents

flood plain and main channel flow interaction experimental results are presented concerning the discharge characteristics the boundary shear stress and boundary shear force distributions in a compound section comprising of one rectangular main channel and two symmetrically disposed flood plains equations are presented giving the shear force on the flood plains as a percentage of the total shear force in terms of two dimensionless parameters the experimental shear force results are used to derive ancillary equations for the lateral and vertical transfer of momentum within the cross section the apparent shear force acting on the vertical interface between one flood plain and the main channel is shown to increase rapidly for low relative depths and high flood plain widths equations are also presented giving the proportion of the total flow which occurs in the various sub areas the division of flow based on linear proportion of the areas is shown to be inadequate on account of the interaction between the flood plain and main channel flows

flood plain filling by a monoclinal flood wave theoretical equations are derived to estimate the flood wave celerity and the volume of lateral flow leaving the main channel and entering the flood plain for a two dimensional monoclinal wave the equations are based on conservation of water mass assuming an idealized compound channel the parameters that affect the lateral flow volume are the ratio of flood plain depth to the depth in the main channel at the peak discharge the ratio of the flood plain width to the main channel width and the ratio of the flood plain roughness to the main channel roughness the percentage of flood plain volume filled up by lateral flow from the main channel increases as the width ratio decreases the roughness ratio increases or as the depth ratio decreases

evolution of fault systems at a strike slip plate boundary a viscoelastic model a viscoelastic model of crustal deformation suggests that the formation and evolution of strike slip fault systems are strongly influenced by rheologic contrasts between the upper and lower crust when deformation is driven by a narrow zone of high shear in the mantle the presence of a low viscosity lower crustal layer underlying a primarily elastic upper crust widens the deformation zone with time and promotes the formation of a broadly distributed network of interacting faults within the upper crust in contrast the deformation zone in a primarily elastic crust is narrow encompassing a single plate bounding fault patterns of surface strain rate and seismicity are thus significantly more complex in the presence of a low viscosity lower crust due to interactions between faulting in the upper crust at short time scales and viscous behavior in the lower crust at long time scales

evidence in hydrography and density fine structure for enhanced vertical mixing over the mid atlantic ridge in the western atlantic received 24 august 2001 revised 22 february 2002 accepted 25 march 2002 published 15 october 2002 1 anomalous conditions exist in the salinity oxygen and nutrient fields over the western flank of the northern hemisphere mid atlantic ridge we examine possible advective sources for this anomaly but determine that vertical mixing is the most likely cause we proceed to use knowledge gained from the brazil basin tracer release experiment in the south atlantic where microstructure and fine structure were obtained to explore the intensity spatial distribution and mechanisms of mixing in the deep ocean to interpret density fine structure from common conductivity temperature depth data in the north atlantic these data support the hypothesis that the anomalous hydrographic conditions are associated with enhanced levels of vertical mixing the inferred levels of vertical diffusivity over the northern hemisphere mid atlantic ridge are as high as in the south atlantic 1 10 10 4 m 2 s index terms 4532 oceanography physical general circulation 4536 oceanography physical hydrography 4568 oceanography physical turbulence diffusion and mixing processes keywords diapycnal mixing fine structure recirculation mid atlantic ridge mar hydrography silicate

mechanical deformation model of the western united states instantaneous strain rate field summary we present a relationship between the long term fault slip rates and instantaneous velocities as measured by global positioning system gps or other geodetic measurements over a short time span the main elements are the secularly increasing forces imposed by the bounding pacific and juan de fuca jdf plates on the north american plate viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods and steady slip along creeping portions of faults in the context of a thin plate system in detail the physical model allows separate treatments of faults with known geometry and slip history faults with incomplete characterization i e fault geometry but not necessarily slip history is available creeping faults and dislocation sources distributed between the faults we model the western united states strain rate field derived from 746 gps velocity vectors in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding pacific and jdf plates relaxation following major earthquakes m 8 0 strongly shapes the present strain rate field over most of the plate boundary zone equally important are lateral shear transmitted across the pacific north america plate boundary along 1000 km of the continental shelf downdip forces distributed along the cascadia subduction interface and distributed slip in the lower lithosphere post earthquake relaxation and tectonic forcing combined with distributed deep slip constructively interfere near the western margin of the plate boundary zone producing locally large strain accumulation along the san andreas fault saf system however they destructively interfere further into the plate interior resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone much of the rightlateral strain accumulation along the saf system is systematically underpredicted by models which account only for relaxation from known large earthquakes this strongly suggests that in addition to viscoelastic cycle effects steady deep slip in the lower lithosphere is needed to explain the observed strain rate field

estimation of flow direction in meandering compound channels abstract the flow in the main channel of a meandering compound channel does not occur in the ridge direction because of the effect of the upstream floodplain flows this study proposes a model for estimating the flow direction in the depth averaged two dimensional domain depth averaged flow angles between the entrance and the apex sections detailed velocity measurements were performed in the region between the meander entrance section and apex section in a large scale meandering compound channel the vertical size of the secondary current cell is highly related to the depth averaged flow angle thus the means of the local flow angles above the secondary current cell and within the cell are separately discussed the experimental measurements indicate that the mean local flow angle above the cell is equal to the section angle whereas the mean local flow angle within the cell is equal to zero the proposed model is validated using published data from five sources good agreement is obtained between the predictions and measurements indicating that the proposed model can accurately estimate the depth averaged flow direction in the meandering compound channels finally the limitations and application ranges of the model are discussed

flow resistance and momentum flux in compound open channels new formulations are presented for flow resistance and momentum flux in compound open channels as implemented in the st venant equations these formulations facilitate a physically enhanced approach to evaluating conveyance roughness stage discharge relationship and unsteady flood routing in compound open channels an analysis using steady flow data from the well controlled experiments at the large scale flood channel facility hr wallingford demonstrates the ability of the present approach to properly resolve the discontinuity of overall roughness across the main channel bankfull level also the proposed formulations are shown to be conducive to obviating the long standing computational difficulty in unsteady flood routing due to small flow depths over flat and wide floodplains the present work should find general applications in one dimensional computation of river flows

three dimensional numerical model for flow through natural rivers this paper presents a three dimensional numerical model for simulating flow through natural river reaches the model solves the reynolds averaged navier stokes rans equations closed with the standard ik e turbulence model large scale roughness and multiple islands are directly resolved by employing boundary fitted curvilinear coordinates in conjunction with a multiblock approach small scale bed roughness is accounted for using a two point wall functions approach calculations are carried out for flow through a 4 km stretch of the columbia river downstream of the wanapum dam for which detailed field and laboratory measurements were collected for a range of power plant operating conditions measurements at one operating discharge are employed to calibrate the small scale roughness distribution in the numerical model subsequently the calibrated model is validated by comparing the computed results with laboratory and field measurements for other discharge combinations these comparisons demonstrate the ability of the model to capture most experimental trends with remarkable accuracy

flow distribution in compound channels the performances of four of the most commonly used methods for discharge calculation in compound channels of varying roughness were assessed by comparison with laboratory data the four methods are based on splitting the section into main channel and floodplain subdivisions using either horizontal or vertical interfaces the accuracy of the four methods in calculating overall section discharge generally increases at greater floodplain depth and with smoother floodplains however the distribution of flow within the section is generally poorly modelled which leads to very erroneous values for momentum and kinetic energy flux

the velocity field along the san andreas fault in central and southern california the velocity field within a 100 km broad zone centered on the san andreas fault between the mexican border and san francisco bay has been inferred from repeated surveys of trilateration networks in the 1973 1989 interval the velocity field has the appearance of a shear flow that remains parallel to the local strike of the fault even through such major deflections as the big bend of the san andreas fault in the transverse ranges of southern california across strike profiles of the fault parallel component of velocity exhibit the expected sigmoidal shape whereas across strike profiles of the fault normal component of velocity are flat and featureless no significant convergence upon the fault is observed even along the big bend sector of the fault simple dislocation models can explain most of the features of the observed velocity field but those explanations are not unique about 35 mm yr of relative plate motion is accounted for within the span of the trilateration networks geologic studies indicate that the secular slip rate on the san andreas fault is about 35 mm yr the agreement between these two estimates implies that most of the strain accumulation is elastic and will be recovered in subsequent earthquakes the relative motion observed across the san andreas fault 35 mm yr plus that observed across the eastern california shear zone 8 mm yr accounts for most 43 mm yr of the observed north america pacific relative plate motion 47 mm yr

simple spatially distributed models for predicting flood inundation a review abstract in this paper we review recent progress in the use of reduced complexity models for predicting floodplain inundation we review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one dimensional shallow water equations we then review how such schemes can be applied in practice and consider issues of space discretization time discretization and model parameterisation before going on to consider model assessment procedures we show that a key advantage of reduced complexity codes is that they force modellers to think about the minimum process representation necessary to predict particular quantities and act as a check on any tendency to reductionism at the same time however the use compared to standard hydraulic codes of strong simplifying assumptions requires us to also address the question how simple can a model be and still be physically realistic we show that by making explicit this debate about acceptable levels of abstraction reduced complexity codes allow progress to be made in addressing a number of long standing debates in hydraulics

the effects of seasonal changes to in stream vegetation cover on patterns of flow and accumulation of sediment abstract in stream macrophytes are typically abundant in nutrient rich chalk streams during the spring and summer months and modify the in stream environment by altering river flows and trapping sediments we present results from an inter disciplinary study of two river reaches in the river frome catchment dorset uk the investigation focused on how ranunculus water crowfoot the dominant submerged macrophyte in the study reaches modified patterns of flow and sediment deposition measurements were taken on a monthly basis throughout 2003 to determine seasonal patterns in macrophyte cover associated changes in the distributions of flow velocities and the character and amount of accumulated fine sediment within stands of ranunculus maximum in stream cover of macrophytes exceeded 70 at both sites flow velocities were less than 0 1 m s 1 within the stands of ranunculus and accelerated to 0 8 m s 1 outside the stands during the early stages of the growth of ranunculus fine sediment mostly accumulated within the upstream section of the plant but the area of fine sediment accumulation extended into the downstream trailing section of the plant later in the growing season the fine sediment accumulations were dominated by sand 63 1000 m with silts and clays 0 37 63 m comprising

computer simulations of california tectonics confirm very low strength of major faults recent improvements in the technique of modeling fault networks with thin plate finite elements yield full convergence of the solutions without any compromise in the representation of the frictional rheology of the upper crust or the transition to dislocation creep in the lower crust we apply these techniques to model the california region incorporating all faults with estimated slip rate over 1 mm yr as well as variations in elevation heat flow and crustal thickness velocity boundary conditions on the model sides are based on the nuvel 1 plate model and an approximation of deformation in the great basin the frictional and dislocation creep rheologic constants of the crust are calibrated to reproduce the observed variations in the maximum depth of seismicity which occurs at model temperatures of 350 410 c this leaves two free parameters the time averaged coefficient of friction on faults and the apparent activation energy for creep in the lower crust these parameters are systematically varied in three sets of 10 81 and 64 experiments respectively the predictions of each model are tested against three published data sets a set of 79 geologic limits on average slip rate on faults a set of 221 principal stress directions and a set of 841 secular rates of geodetic baselines both trilateration and vlbi very long baseline interferometry the patterns of model scores indicate that the time averaged friction coefficient of major faults is only 0 17 0 25 or only 20 30 of the value 0 85 that is assumed for the friction in the intervening blocks the laser trilateration data taken alone would indicate a preference for a high stress model but this model is one with very little fault slip and seismicity which can be rejected on other grounds in the final three parameter set of 64 models we test whether the anomalous weakness of faults is uniform or proportional to net slip with slip dependent weakening there is a general reduction in prediction errors which supports the hypothesis the geologic data and geodetic data agree in implying that fault weakness that is friction of 0 17 is general with an additional 30 slip dependent weakening of the san andreas to friction of 0 12 or 14 of normal the stress data however are fit best if all weakness is slip dependent effectively only the san andreas is weak thus the hypothesis that all weakening is slip dependent should not be rejected the best models predict all available data with rms root mean square mismatch of as little as 3 mm yr 6 of the relative plate velocity so their predictions may be useful for seismic hazard estimation at least along faults where no data are available this study extends the finding of very low friction from subduction zones where it was previously documented to a dominantly strike slip system in which underthrusting of wet sediment is not widespread return of previously subducted water from the mantle and its chemical or physical binding in fine grained gouge are possible explanations for the very low friction

late pleistocene to holocene slip rates for the gurvan bulag thrust fault gobi altay mongolia estimated with 10be dates 1 we surveyed morphotectonic markers along the central part of the gurvan bulag thrust a fault that ruptured with the bogd fault during the gobi altay earthquake 1957 m 8 3 to document climatic and tectonic processes along the fault for the late pleistoceneholocene period the markers were dated using 10 be produced in situ two major periods of alluviation ended at 131 20 and 16 4 8 ka these appear to be contemporaneous with global climatic changes at the terminations of marine isotope stages mis 6 and 2 the vertical slip rates determined from offset measurements and surfaces ages are 0 14 0 03 mm yr over the late pleistocene holocene and between 0 44 0 11 and 1 05 0 25 mm yr since the end of the late pleistocene the higher of these slip rates for the last 16 kyr is consistent with paleoseismic investigations along the fault prentice et al 2002 and suggests that at the end of late pleistocene the fault evolved from quiescence to having recurrence intervals of 4 0 1 2 kyr for surface ruptures with 4 m vertical offset similar to that of 1957 the inferred recurrence interval is comparable to that of the bogd fault 3 7 1 3 kyr suggesting that the two faults may have ruptured together also earlier during the last 16 kyr index terms 7221 seismology paleoseismology 1208 geodesy and gravity crustal movements intraplate 8110 1824 hydrology geomorphology 1625 7230 seismology seismicity and seismotectonics 8107 tectonophysics continental neotectonics keywords late pleistocene holocene thrust fault slip rate 10be dating mongolia

velocity distribution in compound channel flows by numerical modeling the paper examines the problem of prediction of uniform turbulent flow in a compound channel with the nonlinear k e model this model is capable of predicting the secondary currents caused by the anisotropy of normal turbulent stresses that are important features of the flow in compound channels as they determine the transverse momentum transfer the model is applied to reproduce experimental runs available in the literature the comparison shows that the model predicts with accuracy the distribution of the primary velocity component the secondary circulation and the discharge distribution the numerical results are used to search a subdivision surface between main channel and floodplain on the basis of the flow field and to compare different subdivision surfaces on the basis of the discharge distribution by a simple uniform flow formula the better subdivision surfaces as predicted by the model are the diagonal surface going from the corner between main channel and floodplain to the free surface on

inter book normal fault related shear heating in brittle bookshelf faults abstract this work models shear heat related temperature rise due to inter book dip slip normal faults by a bookshelf mechanism such faults are characterized by temporally changing the dip of the inter book fault planes considerable temperature can be produced by such faulting although the effects of high temperature have not yet been reported around such fault planes this may mean that fluids flowing through such planes do not allow shear heating to accumulate

a simple raster based model for flood inundation simulation in this paper the development of a new model for simulating flood inundation is outlined the model is designed to operate with high resolution raster digital elevation models which are becoming increasingly available for many lowland floodplain rivers and is based on what we hypothesise to be the simplest possible process representation capable of simulating dynamic flood inundation this consists of a one dimensional kinematic wave approximation for channel flow solved using an explicit finite difference scheme and a two dimensional diffusion wave representation of floodplain flow the model is applied to a 35 km reach of the river meuse in the netherlands using only published data sources and used to simulate a large flood event that occurred in january 1995 this event was chosen as air photo and synthetic aperture radar sar data for flood inundation extent are available to enable rigorous validation of the developed model 100 50 and 25 m resolution models were constructed and compared to two other inundation prediction techniques a planar approximation to the free surface and a relatively coarse resolution two dimensional finite element scheme the model developed in this paper outperforms both the simpler and more complex process representations with the best fit simulation correctly predicting 81 9 of inundated and non inundated areas this compares with 69 5 for the best fit planar surface and 63 8 for the best fit finite element code however when applied solely to the 7 km of river below the upstream gauging station at borgharen the planar model performs almost as well 83 7 correct as the raster model 85 5 correct this is due to the proximity of the gauge which acts as a control point for construction of the planar surface and the fact that here low lying areas of the floodplain are hydraulically connected to the channel importantly though it is impossible to generalise such application rules and thus we cannot specify a priori where the planar approximation will work simulations also indicate that for this event at least dynamic effects are relatively unimportant for prediction of peak inundation lastly consideration of errors in typically available gauging station and inundation extent data shows the raster based model to be close to the current prediction limit for this class of problem q 2000 elsevier science b v all rights reserved

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

the motion of crustal blocks driven by flow of the lower lithosphere and implications for slip rates of continental strike slip faults geodetic measurements in actively deforming areas of the continents reveal the pattern of deformation in the lithosphere if the dominant forces acting on crustal blocks are tractions at their bases then the long term motion of each block will be given by the average velocity of the underlying lithosphere slip rates between blocks estimated in this way from recent geodetic measurements across fault zones in the south island of new zealand and southern california are in good agreement with slip rates estimated geologically

application of a roughness length representation to parameterize energy loss in 3 d numerical simulations of large rivers 1 recent technological advances in remote sensing have enabled investigation of the morphodynamics and hydrodynamics of large rivers however measuring topography and flow in these very large rivers is time consuming and thus often constrains the spatial resolution and reach length scales that can be monitored similar constraints exist for computational fluid dynamics cfd studies of large rivers requiring maximization of mesh or grid cell dimensions and implying a reduction in the representation of bedform roughness elements that are of the order of a model grid cell or less even if they are represented in available topographic data these subgrid elements must be parameterized and this paper applies and considers the impact of roughness length treatments that include the effect of bed roughness due to unmeasured topography cfd predictions were found to be sensitive to the roughness length specification model optimization was based on acoustic doppler current profiler measurements and estimates of the water surface slope for a variety of roughness lengths this proved difficult as the metrics used to assess optimal model performance diverged due to the effects of large bedforms that are not well parameterized in roughness length treatments however the general spatial flow patterns are effectively predicted by the model changes in roughness length were shown to have a major impact upon flow routing at the channel scale the results also indicate an absence of secondary flow circulation cells in the reached studied and suggest simpler two dimensional models may have great utility in the investigation of flow within large rivers

flow and velocity distribution in meandering compound channels an investigation of flow and velocity distribution in meandering compound channels with over bank flow is described equations concerning the three dimensional variation of longitudinal transverse and vertical velocity in the main channel and floodplain of compound section in terms of channel parameters are presented the flow and velocity distributions in meandering compound channels are strongly governed by interaction between flow in the main channel and that in the floodplain the proposed equations take adequate care of the interaction affect results from the formulations simulating the three dimensional velocity field in the main channel and in the floodplain of meandering compound channels are compared with their respective experimental channel data obtained from a series of symmetrical and unsymmetrical test channels with smooth and rough sections the aspect ratio of the test channels varies from two to five the equations are found to be in good agreement with the experimental data the formulations are verified against the natural river and other meandering compound channel data the power laws used for simulating the three dimensional velocity structure are found to be quite adequate

the flux of bio and lithogenic material associated with sinking particles in the mesopelagic twilight zone of the northwest and north central pacific ocean abstract as part of the vertigo program we collected and analyzed sinking particles using tethered and neutrally buoyant sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 this effort represented the first large scale use of neutrally buoyant traps and represents a significant step forward in the study of the marine biological pump in this paper we present the results of mass macronutrient biominerals and phytoplankton pigment determinations made on these samples the impact of a variety of potential collection biases were examined including those from in trap particle degradation zooplankton swimmers and poisons though these factors have been observed to affect results in other programs we found them to have relatively little impact on measured fluxes in this study there was evidence however that the neutrally buoyant traps performed better than the tethered traps in terms of flux accuracy during one deployment possibly because of improved large particle collection efficiency fluxes of material exhibited three different patterns through the mesopelagic increasing decreasing and constant with depth decreasing fluxes with depth were observed for all biogenic material formed in the euphotic zone the attenuation of flux with depth was not the same for all components however with phytoplankton pigments exhibiting the greatest degradation with depth and particulate inorganic carbon the least organic carbon and nitrogen showed a very high correlation in these samples with little evidence of different attenuation length scales increasing fluxes with depth were observed for particulate ba at both sites and al at k2 the increases in ba are attributed to the formation of barite in degrading particles while increasing al at k2 was the result of lateral inputs from a continental shelf slope constant fluxes with depth were observed for al at aloha where fluxes appeared to be in steady state with atmospheric dust deposition the mesopelagic zone at k2 was observed to attenuate particle flux less than at aloha and with a higher poc pic rain ratio these two factors combine to imply that the subarctic province had a much more efficient biological pump than had the subtropical gyre during our occupations this could be the result of either faster sinking particles generated from grazing by large zooplankton or inherently slower particle degradation rates

application of two and three dimensional computational fluid dynamics models to complex ecological stream flows complex flow patterns generated by irregular channel topography such as boulders submerged large woody debris riprap and spur dikes provide unique habitat for many aquatic organisms numerical modeling of the flow structures surrounding these obstructions is challenging yet it represents an important tool for aquatic habitat assessment in this study the ability of two 2 d and three dimensional 3 d computational fluid dynamics models to reproduce these localized complex flow features is examined the 3 d model is validated with laboratory data obtained from the literature for the case of a flow around a hemisphere under emergent and submerged conditions the performance of the 2 d and 3 d models is then evaluated by comparing the numerical results with field measurements of flow around several boulders located at a reach of the smith river a regulated mountainous stream obtained at base and peak flows close agreement between measured values and the velocity profiles predicted by the two models is obtained outside the wakes behind the hemisphere and boulders however the results suggest that in the vicinity of these obstructions the 3 d model is better suited for reproducing the circulation flow behavior at both low and high discharges application of the 2 d and 3 d models to meso scale stream flows of ecological significance is furthermore demonstrated by using a recently developed spatial hydraulic metric to quantify flow complexity surrounding a number of brown trout spawning sites it is concluded that the 3 d model can provide a much more accurate description of the heterogeneous velocity patterns favored by many aquatic species over a broad range of flows especially under deep flow conditions when the various obstructions are submerged issues pertaining to selection of appropriate models for a variety of flow regimes and potential implication of the 3 d model on the development of better habitat suitability criteria are discussed the research suggests ways of improving the modeling practices for ecosystem management studies

chlorofluorocarbons in the sea of okhotsk ventilation of the intermediate water 1 ventilation of the intermediate layer in the sea of okhotsk is studied with regard to the ventilation of north pacific intermediate water npiw measurements of chlorofluorocarbons cfcs from 1998 to 2000 reveal that the okhotsk intermediate water is ventilated in two ways the first consists of dense water formation in the polynyas that form on the northern shelves during winter measurements show that on the northwestern shelf because of atmospheric cooling and brine rejection the cold water that forms is dense enough to enter the intermediate layer the cfc concentration in this dense shelf water dsw is high and almost saturated with respect to atmospheric cfcs indicating that the dsw experiences active air water gas exchange during its formation away from the shelves the cfc distribution shows that the dsw directly ventilates the upper level of the okhotsk sea intermediate water osiw the second ventilation process is driven by the strong tidal mixing around the bussol strait the observed distribution of cfcs at the 27 4 level suggest that diapycnal mixing around the strait transports cfcs from the surface to this deeper layer ventilating the osiw combination of both processes means that the osiw is more ventilated than pacific water at the same density levels

discharge assessment in compound channel flow a series of laboratory tests were performed to measure the boundary shear stresses in a compound channel consisting of a main channel and associated shallow floodplains four different floodplain roughnesses were used from these results apparent shear stresses across three different assumed main channel floodplain interface planes vertical horizontal and diagonal were calculated the data was used with data from previous studies to derive a statistical relationship between the apparent shear stress on the vertical interface and several easily calculated parameters of the channel geometry and hydraulic characteristics the accuracies of different methods of discharge calculation were shown to be dependent upon the assumptions they make regarding the magnitude of the apparent shear stress on the particular interface chosen an apparent shear stress ratio was proposed which was found to be a useful yardstick in selecting the best method of discharge calculation for particular channel and flow conditions generally it was found that at low floodplain depths using the horizontal or diagonal interfaces gave better discharge results than the vertical

turbulent structure in compound open channel flows an investigation of three dimensional 3 d turbulent structure including turbulence driven secondary currents in compound open channel flows is a very important topic in hydraulic and river engineering as well as in fluid mechanics in this study accurate measurements in fully developed compound open channel flows are conducted by means of a fiber optic laser doppler anemometer flda secondary velocities can be measured very accurately with the present 3 d measurement system the characteristics of compound open channel flows are recognized in the junction region between the main channel and flood plain whereas the characteristics of rectangular open channel flows are observed in a region near the sidewall of the main channel strong inclined secondary currents which are associated with a pair of longitudinal vortices are generated in the junction region between the main channel and the flood plain the primary mean velocity field is directly influenced by these secondary currents turbulence i

turbulent flow across a natural compound channel 1 the measurements and primary analysis of turbulent flow across a compound channel river severn england are presented the velocity was measured using a three dimensional acoustic doppler velocimeter in combination with a directional current meter the statistical flow structure is examined against existing analytical formulations derived for single channel flows based on laboratory studies the existence of a vertically two layer structure around the interface between the main channel and the floodplain is demonstrated indicating 1 a vertical shear dominated flow zone near the bed and 2 away from the bed a transverse shear dominated flow zone with enhanced turbulent mixing the temporal spectra clearly reveal the occurrence of anisotropic turbulence both in the main channel and over the floodplain the present findings necessitate the resolution of both transverse and vertical structures for advanced modeling of compound channel flows the measured data can be used to assess the performance of mathematical river models

modelling floods in hydrologically complex lowland river reaches abstract this paper considers the modelling of lowland river reaches which contain complex within reach hydrological interactions it is clear that river and floodplain flow are the most important processes in terms of flood modelling in lowland systems although there are often important lateral inflows from catchments and hillslopes bounding the floodplain and from interactions between the river and the floodplain which can all affect the propagation of the flood wave previous models have often either considered a complex representation of the fluvial processes with no representation of the hydrological inflows into the reach bates p d anderson m g price d a hardy r j smith c n 1996 analysis and development of hydraulic models for floodplain flows in anderson m g walling d e bates p d eds floodplain processes wiley chichester pp 215 254 or have simulated a range of catchment processes with a poor representation of the river and floodplain abbot m b bathurst j c cunge j a o connell p e rasmussen j 1986 an introduction to the european hydrological system systeme hydrologique europeen she 2 structure of a physically based distributed modelling system journal of hydrology 87 61 77 hence this paper develops a modelling approach based on a two dimensional finite element hydraulic model of river and floodplain flow which is linked to a series of simple hydrological models that simulate catchment runoff surface and subsurface hillslope runoff and floodplain infiltration simulations show that the model is able to predict flood hydrographs for a series of flood events under a range of different hydrological conditions down a reach of the river severn uk furthermore the comparison of results from simulations using hydrological representations of different degrees of complexity suggest that there are restrictions on the necessary complexity of the hydrological components depending on the application of the model and the available validation data simple approaches to the reach scale hydrology may be sufficient if only the bulk outflow hydrograph is required by the user however more complex spatially and temporally distributed models appear to be required if predictions of the flood inundation extent are desired the simulations raise the issue of the application of distributed models and attempt to provide a framework for future research the results suggest that there is a need for the validation of the internal predictions of distributed models of flood flow and suggests a need for field data of river and floodplain interactions within long lowland river reaches

late holocene slip rate and recurrence of great earthquakes on the san andreas fault in northern california the slip rate of the san andreas fault 45 km north of san francisco at olema california is determined by matching offset segments of a buried late holocene stream channel stream deposits from 1 800 plus minus 78 yr b p are offset 42 5 plus minus 3 5 m across the active 1906 fault trace for a minimum late holocene slip rate of 24 plus minus 3 mm yr when local maximum coseismic displacements of 4 9 to 5 5 m from the 1906 earthquake are considered with this slip rate the recurrence of 1906 type earthquakes on the north coast segment of the san andreas fault falls within the interval of 221 plus minus 40 yr both comparable coseismic slip in 1906 and similar late holocene geologic slip rates at the olema site and a site 145 km northwest at point arena prentice 1989 suggest that the north coast segment behaves as a coherent rupture unit

geometry and evolution of the san andreas fault zone in northern california the evolution of the san andreas fault system is controlled by thermal mechanical processes associated with the development and evolution of a narrow slabless window formed beneath the western edge of north america this fault zone evolution begins after initiation of transform motion along the plate boundary with the northward migration of the mendocino triple junction as a consequence of initial lithospheric structure and the shallow emplacement of asthenospheric mantle the plate boundary separating the north american and pacific plates follows a complex three dimensional geometry which varies through time seismic velocity structure heat flow seismicity surface deformation uplift and fault development are controlled by the evolving thermal structure in the region after triple junction passage thermal mechanical models have been used to evaluate the fault system s time varying three dimensional dynamical behavior simulating the principal processes involved in the thermal mechanical evolution of the san andreas fault system results from this modeling indicate that the fault system has essentially a three stage history 1 in the vicinity of the mendocino triple junction the san andreas fault maps the eastern edge of the pacific plate with a broad 100 km zone of asthenospheric mantle separating the pacific and north american plates in the 25 to 90 km depth range 2 between 37 n and 39 n the plate boundary within the mantle separating the pacific and north american plates has developed approximately 40 60 km east of the surface trace of the san andreas fault and lies beneath the hayward calaveras faults and associated faults the surface trace of the plate boundary appears to be connected to the mantle segment via a lower crust subhorizontal detachment surface this fault zone orientation produces the surface deformations observed geodetically in the region 3 south of 37 n the surface fault again overlies the deeper plate boundary apparently as a result of an eastward jump in the surface fault

present tectonic motion across the coast ranges and san andreas fault system in central california geodetic results from very long baseline interferometry vlbi satellite laser ranging slr and the global positioning system gps are used to estimate angular velocities between the sierran microplate pacific plate and north american plate the sierra pacific pole of rotation lies nearer to the san andreas fault than does the pacific north america pole of rotation and leads to different tectonic implications than if the latter is used the angular velocities show that the san andreas fault system and central california coast ranges accommodate motion of 39 2 mm yr mainly by strike slip faulting all confidence limits following signs in this paper are 95 confidence limits fault normal motion is small is mainly convergent at rates up to 3 3 1 0 mm yr and varies along the coast but is divergent at 2 6 1 2 mm yr across san pablo bay and associated topographic lows across which the sierran and central valley watershed drains to the pacific ocean the mountain ranges tend to be larger where the fault normal convergence rates are larger the low convergence rate 0 5 1 8 mm yr normal to the san andreas fault in the carrizo plain differs sharply from that previously inferred 8 2 1 2 mm yr and 4 9 1 6 mm yr by feigl et al 1993 the difference is due to differences between their and our elastic strain accumulation models and between how their and our pacific plate reference frames are defined the ranges in most places require a minimum of 4 2 1 m y of fault normal convergence at the present rate to attain their present cross sectional area if erosion is neglected more if it is not the amount of convergence previously estimated from a balanced cross section across the diablo range in central california requires 10 8 3 m y of convergence at the present rate the former is consistent with widely held views about the onset of the coast range orogeny but the latter is not both are consistent however with the recent plate reconstructions by s cande j stock and colleagues which indicate that pacific plate motion relative to north america changed to a more convergent direction 20 25 clockwise of its prior direction at ca 8 to 6 ma and not at 3 5 ma as had been previously inferred the inferred change in direction of plate motion is large compared with the present angle of convergence across the straight and narrow segment of the san andreas fault of 0 7 4 7 from which we infer that the sierran microplate changed motion relative to north america at the same time ca 8 to 6 ma as did the pacific plate we further infer that the motion accommodated across the great basin must also have changed at the same time we also examine the hypothesis that stable sliding occurs along the san andreas fault and other northwest striking strike slip faults in central california where the fault normal convergence rate is low or negative and that these faults are unstable where the fault normal convergence rate is high such a relationship appears to hold in general but fails in detail in particular there are substantial sections of fault with small inferred rates of fault normal convergence across which the san andreas fault is locked moreover the creeping section of the san andreas fault i e the section between parkfield and the calaveras junction is the locus of greater fault normal convergence 3 2 1 4 mm yr than is the locked part of the fault 0 5 1 8 mm yr south of parkfield thus this hypothesis is at best a partial explanation for the observed distribution of locked and nonlocked sections of the fault

three dimensional numerical simulation and analysis of flows around a submerged weir in a channel bendway to improve navigation conditions for barges passing through river channels many submerged weirs sws have been installed along the bendways of many waterways by the u s army corps of engineers this paper presents results from three dimensional numerical simulations that were conducted to study the helical secondary current hsc and the near field flow distribution around one sw the simulated flow fields around a sw in a scale physical model were validated using experimental data the three dimensional flow fields around a sw the influence of the sw on general hsc and the implication of effectiveness of submerged weirs to realign the flow field and improve navigability in bendways were analyzed the numerical simulations indicated that the sw significantly altered the general hsc its presence induced a skewed pressure difference cross its top and a triangular shaped recirculation to the downstream side the over top flow tends to realign toward the inner bank and therefore improves conditions for navigation

mechanical relation between crustal rheology effective fault friction and strike slip partitioning among the xiaojiang fault system southeastern tibet the north south trending xiaojiang fault system accommodates 10 12 mm yr sinistral motions between southeastern tibet and south china in the south segment the fault system composes mainly of four parallel strike slip faults namely from west to east the luzhijiang fault the yimen fault the puduhe fault and the xiaojiang fault geological and seismological observations have shown that these strike slip faults are all of active while the slip rates of the luzhijiang the yimen and the puduhe faults are much less than that of the xiaojiang fault we use finite element modeling to explore the mechanical relation between crustal rheology effective fault friction and long term slip rate partitioning among the four parallel faults the individual faults are simplified as vertical discontinuities embedded in the crust as geophysical explorations have predicted a large number of models are tested associating with variations of the crustal rheolohy and the effective fault friction of individual faults result shows that if crust bounding the faults trends to behave like rigid blocks and decoupled mechanically from underlying layer the modeled result is hard to approximate slip rates of the individual faults to better fit slip rates of the individual faults viscous deformation of the lower crust should be included with a heterogeneously viscous lower crust model that is built upon thermal structure of the heat flow data associating with relatively low effective friction of the xiaojiang fault the modeled results fit the geological slip rates well with 1 1 5 mm yr for the luzhijiang the yimen and the puduhe faults and 6 6 5 mm yr for the xiaojiang fault thus in the southward movement of the tibetan plateau around the eastern himalayan syntaxis slip partitioning among the xiaojiang fault system should be related to viscous deformation of the lower crust associated with different strength of the individual faults highlighting that deformation of this fault system is coupled mechanically between the frictional upper crust and the viscous lower crust

multiprofile discharge estimation in the tidal reach of yangtze estuary abstractwith the advent of acoustic doppler current profiler adcp the velocity profile method or index velocity method based on a single profile or a fixed depth cell has been recommended for estimating discharge in tidal reaches however in large tidal reaches with a width of nearly 6 km and cross sectional variability of flow such as yangtze estuary these methods are not accurate enough for the discharge estimation therefore an improved method named the multiprofile method is proposed in this paper the method includes four main steps 1 calculating the cross sectional area a with stage data by considering the transverse slope 2 calculating the depth mean velocity u at each fixed adcp 3 establishing the u u model with the multiprofile us and estimating the cross sectional mean velocity u 4 estimating the final discharge through u multiplied by a the proposed method was tested at the xuliujing section of the yangtze estuary the result shows that the multiprofile method averagely imp

grouping and migration of surface faulting and variations in slip rates on faults in the great basin province abstract nonuniformity of the occurrence of large slip events producing surface ruptures on seismogenic faults and variations in slip rate probably characterize seismogenic faulting in the great basin province western united states examples include the grouping of faulting events along the lost river fault idaho changes in tilt rates of the east range and cortez mountains nevada extension of slip along a fault on the northwest flank of the humboldt range nevada and migration or shifting of slip back and forth from one fault to another along subparallel range front faults in dixie valley nevada

turbulence modeling of flood plain flows a numerical model capable of predicting flow characteristics in a compound channel is described the model solves the continuity and momentum equations along with the transport equations of kinetic energy of turbulence and the dissipation rate closure is achieved with the aid of algebraic relations for turbulence stresses the model is capable of treating compound channels formed by regular geometrical sections of main channel and flood plain segments the width of the main channel the width of the total section the depth of flow in flood plain the total depth channel slope and boundary roughness of main channel section and flood plain section can all be varied the model predictions of total flow rate shear stress distributions around the wetted perimeter and the percentage of flow and shear force carried by the different sections were compared with published experimental data reasonable agreement between data and predictions was obtained

can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence 1 many ood events involving water and sediments have been characterized using classic hydraulics principles assuming the existence of critical ow and many other simplications in this paper hyperconcentrated ow discharge was evaluated by using paleo ood reconstructions based on paleostage indicators psi combined with a detailed hydraulic analysis of the critical ow assumption the exact location where this condition occurred was established by iteratively determining the corresponding cross section so that specic energy is at a minimum in addition all of the factors and parameters involved in the process were assessed especially those related to the momentum equation existing shear stresses in the wetted perimeter and nonhydrostatic and hydrostatic pressure distributions the superelevation of the hyperconcentrated ow due to the ow elevation curvature was also estimated and calibrated with the psi the estimated peak discharge was established once the iterative process was unable to improve thet between the simulated depth and the depth observed from the psi the methodological approach proposed here can be applied to other higher gradient mountainous torrents with a similar geomorphic conguration to the one studied in this paper likewise results have been derived with fewer uncertainties than those obtained from standard hydraulic approaches whose simplifying assumptions have not been considered

rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock mechanics based yield criteria for the inelastic deformations at the top and base at mid plate depths stresses are likely to be supported elastically because bending strains and elastic stresses are low the collisional tectonic regime however is far more complex because very large permanent strains are sustained at mid plate depths and this requires us to include the broad transition between brittle and ductile flow moreover important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid plate depths two specific contributions of laboratory rock rheology research are considered in this paper first the high temperature steady state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere the thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm tc above which at geologic strain rates the high temperature ductile strength falls below some arbitrary strength isobar e g 100 mpa for olivine tc is about 700 800 c but for other crustal silicates tc may be as low as 400 600 c suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the moho as suggested by a number of workers on independent grounds put another way the moho is a rheological discontinuity a second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant strain rate tests or as an accelerating creep rate stage at constant differential stress a number of physical mechanisms have been identified that may be responsible for ductile faulting including the onset of dynamic recrystallization phase changes hydrothermal alteration and hydrolytic weakening microscopic evidence for these processes as well as larger scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere

estimation of effective roughness for water worked gravel surfaces abstractthere is no accepted standard equation for predicting flow resistance in gravel rivers this is mainly because of the lack of an effective approach for describing the roughness of the gravel surface this paper aims at describing the roughness of gravel surfaces based on characteristics of the elevation field rather than conventionally used grain size distribution a new parameter the coarseness parameter in addition to the steepness parameter and standard deviation of the elevation field is proposed for characterizing the roughness of gravel surfaces two groups of rough surfaces a and b were generated using unconditional gaussian simulation to study the influence of the coarseness and steepness parameters on effective roughness the effective roughness of groups a and b was calculated by a two equation turbulence model and a quantitative relationship between the effective roughness and proposed parameters was derived the resulting relationship derived from groups a and b was validated using

factors affecting conveyance in meandering compound flows this paper brings together recent data from the large scale flood channel facility wallingford england with other model studies to investigate the main parameters affecting conveyance in meandering compound river channels parameters investigated include sinuosity boundary roughness main channel aspect ratio width of meander belt and flow depth above bank full level as well as the cross sectional shape of the main channel the effect of each parameter is quantified through a nondimensional discharge coefficient if n possible scale effects in modeling such flows are also investigated

bed morphological changes around a finite patch of vegetation for the appropriate management and restoration of rivers isolated vegetation is often a practical means for improving stream habitat and ecology the effect of a finite vegetation patch on flow and bed morphology in an open channel was investigated using laboratory experiments the patch containing emergent and submerged vegetation was modeled using circular cylinders and located mid channel along a side wall several configurations of the patch and submergence ratio i e water depth to the height of vegetation and two flow conditions i e below and above the sediment motion threshold were considered for flows below the sediment motion threshold erosion occurred primarily on the opposite side of the patch and near the leading edge of the patch the degree of scouring depth observed in both these regions was affected by the submergence ratio and it increased with the non dimensional flow blockage i e the product of the patch density and width in contrast for flows above the sediment motion threshold sediment accumulated within and around the patch due to a reduction in bed shear stress which was strongly influenced by the flow blockage and the obstruction ratio i e the ratio of patch width to channel width the eroded area observed within the patch was consistent with the interior adjustment region where the deceleration and diversion of flow occurred through the patch as the flow blockage increased or as the obstruction ratio decreased the deposition rate within and behind the patch decreased furthermore the deposition rate increased with an increase in the ratio of flow rate through the patch to total flow rate regardless of the submergence ratio copyright 2014 john wiley sons ltd

bidecadal variability in the intermediate waters of the northwestern subarctic pacific and the okhotsk sea in relation to 18 6 year period nodal tidal cycle 1 on the basis of historical oceanographic data we investigated the long term variations of the intermediate waters in the four regions in the northwestern subarctic pacific oyashio okhotsk sea mode water upstream oyashio and east kamchatka current we found bidecadal oscillations in these water properties that are synchronized with the 18 6 year period nodal cycle in periods when the diurnal tide is strong the following characteristics are found apparent oxygen utilization and phosphate are low in oyashio and okhotsk sea mode water the thickness of the intermediate layers is large and thus potential vorticity is correspondingly low in oyashio okhotsk sea mode water and upstream oyashio around the mesothermal temperature maximum water isopycnal potential temperature are low in the areas on the pacific side and high in the intermediate layer of okhotsk sea mode water the mixing ratio of okhotsk sea mode water in the upstream oyashio water is high these bidecadal oscillations can be explained by changes in the vertical mixing around the kuril straits induced by the diurnal tide whose amplitude is modulated with the 18 6 year nodal cycle higher sea surface salinity water around the kuril straits caused by stronger tidal mixing is possibly transported northward along the cyclonic okhotsk sea gyre and possibly enhances the formation of the dense shelf water this makes apparent oxygen utilization phosphate and potential vorticity lower in okhotsk sea mode water and oyashio

bidecadal variability in the bering sea and the relation with 18 6 year period nodal tidal cycle 1 bidecadal variations are investigated in the bering sea especially in the southeastern basin adjacent to the aleutian passes where vertical mixing may be strong because of the diurnal tide those variations found in this region are synchronized with the 18 6 year period nodal tidal cycle and the temporal patterns are similar to ones around the northwestern subarctic pacific near the kuril straits reported by a previous study salinity and density in the upper layer are high in the periods when the diurnal tide is strong in the intermediate layer layer thickness is large and isopycnal potential temperature and apparent oxygen utilization are low in the same periods it is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing and a simple two dimensional model assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer

distribution of displacement on and evolution of a young transform fault system the northern san andreas fault system california this paper presents a working model for the spatial and temporal distribution of dextral slip on the northern san andreas fault system of coastal california based primarily on field relations in the san francisco bay area and offers insight into the evolution of a young transform fault system a fundamental difference between this and previous models of slip distribution is that this model assigns negligible slip to the pilarcitos fault which has been suggested to have 120 to 250 km of post early miocene dextral slip in previous models because separation on the san francisco peninsula reach of the san andreas fault is about 25 km and displacement on the san andreas fault in central california is 310 to 320 km more than 250 km of late cenozoic dextral slip must be accommodated east of the san francisco peninsula the distribution of this dextral slip is constrained by offset late cenozoic and basement units slip distribution combined with ages of offset features and plate boundary kinematic constraints show that the distribution of slip rates on groups of faults along the transform boundary has changed in an irregular fashion through time in contrast to existing models that propose progressive eastward migration of active faulting in the san andreas system in addition to the shifting patterns of displacement a migrating transition zone connecting the eastern faults of the strike slip system to the mendocino triple junction may have resulted in distributed dextral faulting and shortening in the northernmost and youngest part of the transform fault system

climate variability in the north pacific thermocline diagnosed from oxygen measurements an update based on the u s clivar co2 repeat hydrography cruises 1 new observations of oxygen variability in the north pacific ocean are reported on the basis of comparison of the u s climate variability and predictability and carbon clivar co2 repeat hydrography sections conducted along 30 n 2004 and 152 w 2006 with the earlier world ocean circulation experiment woce data and other cruises along these sections the largest changes in apparent oxygen utilization aou continue to occur as found in earlier north pacific repeat section analyses within the thermocline on 26 6 kg m 3 which is the densest isopycnal to outcrop in the open north pacific in climatological data in the northeastern north pacific along 152 w where a total of five cruises 1980 1984 1991 1997 and 2006 spanning a period of 26 years are available the aou changes correspond to an overall increase in aou on 26 6 kg m 3 from the 1980s early 1990s to 2006 however from 1997 to 2006 a decrease in aou is observed within the boundary region between the subtropical and subpolar gyres at 40 45 n along the center axis of the subtropical gyre at 30 n where two cruises are available 1994 and 2004 aou has also substantially increased on 26 6 kg m 3 from 1994 to 2004 in the eastern part of the section the repeat section data along 152 w and 30 n are consistent with a pattern of decadal scale ventilation anomalies that originate in the northwestern pacific possibly through variability including cessation of the 26 6 kg m 3 outcrop travel eastward along the subtropical subpolar gyre boundary and enter the northern portion of the subtropical gyre along the way for the 152 w aou data within the gyre boundary region 40 45 n good agreement exists with the close by time series data from ocean station p 50 n 145 w where a bidecadal cycle in aou has been observed in contrast a sensible correlation with the pacific decadal oscillation could not be found

interdecadal variations in the alaska gyre abstract climatic dynamic topography variations in the alaska gyre during the period 1968 1990 are described with an objective analysis of more than 12000 std and xbt stations and coads wind stress data interannual dynamic height and sst variations were correlated and were consistent with recently described large scale climatic shifts in the north pacific the gyre was cantered more to the east circulation appeared stronger and sst was lower during the early to mid 1970s than during the 1980s the aleutian low np and pna indices intensified during the interim but the response did not appear as a gyre spinup instead the associated wind stress anomalies forced a slowly varying dynamic height anomaly across the eastern and northern part of the gyre through ekman convergence which had the effect of displacing the gyre s low somewhat to the wsw in the 1980s the wind curl spectrum was white and the slow oceanic response was modelled as stochastic forced climate variability with a simple first order m

three dimensional hydrodynamics of meandering compound channels the velocity field in meandering compound channels with overbank flow is highly three dimensional to date its features have been investigated experimentally and little research has been undertaken to investigate the feasibility of reproducing these velocity fields using computer models if computer modeling were to prove successful in this context it could become a useful prediction technique and research tool to enhance our understanding of natural river dynamics in particular an accurate computer prediction of the velocity field could benefit studies of channel morphology and pollution transport in this paper a meandering channel experiment from the u k flood channel facility is simulated using computational fluid dynamics and the predicted velocities compared with the experimental data particular attention is paid to the reproduction of the secondary velocities and the helical motion of the water flowing within the main channel sensitivity tests of mesh design discretization scheme and roughness height are reported together with the turbulence characteristics of the flow

formation and subduction of central mode water based on profiling float data 2003 08 abstract temperature and salinity data from argo profiling floats in the north pacific during 2003 08 have been analyzed to study the structure of winter mixed layer north of the kuroshio extension and the subsurface potential vorticity distribution in the subtropical gyre in relation to the formation and subduction of the central mode water cmw in late winter two zonally elongated bands of deep mixed layer extend at 33 39 and 39 43 n from the east coast of japan to 160 w these correspond to the formation region of the lighter variety of cmw l cmw and that of the denser variety of cmw d cmw and the recently identified transition region mode water trmw respectively in the western part of the l cmw and d cmw trmw formation regions west of 170 e the winter mixed layer becomes deeper and lighter to the east i e to the downstream as a result the formed mode water is reentrained into the mixed layer in the farther east in the following winter and modified to the lighter water and is thus

estimating the distribution of suspended sediment concentration in submerged vegetation flow based on gravitational theory abstract vegetation plays a significant role in river ecosystem which has a great influence on hydraulic structures and sediment transport understanding the vertical distribution of suspended sediment concentration ssc in canopy flow is helpful to study the process of riverbed erosion and deposition in vegetated channels aiming at the sediment laden flow in open channel covered with submerged vegetation this study divides the water depth into two layers along the vertical direction with the vegetation height as the boundary and then proposes a new ssc distribution model based on gravitational theory to estimate the vertical distribution of relative ssc in the free water layer and vegetation layer respectively in the meanwhile a new formula is also proposed to evaluate the reynolds shear stress below the submerged vegetation height which has been successfully applied in the derivation of the new ssc distribution model the validation results of the simplified velocity model the new reynolds shear stress formula and the new ssc model compare well with the collected experimental data series on top of that it is found that the uniformity of ssc distribution profile progressively decreases with the increasing sediment particles diameters besides according to the validation results and discussion it is believed that the controversy point about gravitational theory would not have obvious influence on the estimation of ssc distribution so that the gravitational theory can be adopted to investigate suspended sediment transport in vegetation flow that would be benefit for river ecological restoration and better management

bed evolution in channel bends a numerical model for simulation of temporal bed evolution in channel bends with fixed walls is constructed and verified with laboratory experiments the model is based on governing equations of flow and sediment motion with some simplifying assumptions numerical experiments are conducted using the model to investigate influences of various factors on bed evolution it is found that the process of bed evolution in channel bends with steady discharge and uniform sediment can be approximated by a complementary exponential decay function of a time parameter a regression equation is established for the coefficient as a function of flow condition bend geometry and sediment size these relations the numerical model or both may be applied to evaluate evolution of bed topography in river bends numerical results are also verified with laboratory experiments

kinematics of the pacific north america plate boundary zone northern california we measured motions of 54 sites in an east west transect across northern california at 38 40 north by global positioning system gps observations over a 4 year we estimate the total slip rate on the san andreas fault system to be 39 6 0 6 1 5 mm yr 68 6 upper and lower confidence intervals from a nonlinear inversion are indicated by superscripts and subscripts slip rates on the individual faults are determined less precisely due to the high correlations between the estimated parameters our best fitting model fits the fault parallel velocities with a mean square error of 1 04 and the following estimated fault slip rates all in mm yr san andreas 17 4 3 1 2 5 ma acama 13 9 2 8 4 1 and bartlett springs 8 2 1 9 2 1 the data are fit best by models in which the san andreas fault is locked to 14 9 7 1 12 5 km the ma acama fault locked to 13 4 4 8 7 4 km except for shallow creep in the upper 5 km and the bartlett springs fault creeping at all depths the ma acama fault most likely poses a significant seismic hazard as it has a high slip rate and has accumulated a slip deficit large enough to generate a magnitude 7 earthquake we find little evidence for contraction across coast ranges except at western edge of great valley where 1 3 mm yr of shortening is permitted by the data no strain is observed within the great valley or sierra nevada except that associated with right lateral strike slip on the san andreas fault system this is consistent with models of the pacific north america plate boundary zone in which the relative plate motion is partitioned into two domains one strike slip and one dominantly extensional separated by the elastically deforming sierra nevada great valley block

flow and bed profile in meandering sand silt rivers mathematical models for defining three dimensional flow and bed topography in sinuous channels with suspendable bed material are presented it is shown theoretically that the secondary flow in sinuous channels shows a reduction in its magnitude below that of a uniformly curved channel and also displays a phase lag relative to the channel plan form the model for bed topography is derived by considering the sediment balance for bed load and suspended load the transport rate and direction all of which are governed by the three dimensional flow a laboratory test supports the model the present study has made it possible to predict the large scale bed topography of meandering sand silt rivers including such features as the magnitude and the location of local scour and point bar deposits

tropical forcing of north pacific intermediate water distribution during late quaternary rapid climate change abstract evidence is presented demonstrating intermediate water 500 m temperature variability at odp hole 893a in santa barbara basin during submillennial climate change 11 60 ka benthic 18 o oscillations are considered to result primarily from shifts in intermediate water temperature at the site detailed comparison of both benthic and planktonic records from the basin provide crucial evidence for differing surface and intermediate water mass temporal responses to rapid climate change gradual warming of intermediate water compared to abrupt cooling suggests mechanistic differences between processes controlling north pacific intermediate water expansion and contraction relative to southern component intermediate waters comparisons suggest intermediate water warming preceded by 60 200 years the most rapid interval of surface warming inferred to be associated with north pacific atmospheric reorganization tropical forcing of sea level anomalies in the eastern pacific via trade wind strength may control california undercurrent flow 300 500 m and be the cause of early intermediate water warming in santa barbara basin

interdecadal variability in dissolved oxygen in the intermediate water layer of the western subarctic gyre and kuril basin okhotsk sea using dissolved oxygen do concentration at isopycnal surfaces we have observed an oscillation in the intermediate water layer of the western subarctic gyre wsg and the kuril basin of the okhotsk sea with a period of about 20 years the interdecadal oscillation in do is strongly correlated with the intensity of the aleutian low pressure cell with a 2 year time lag the interdecadal variations in do in the intermediate water layer of the wsg and the okhotsk sea may be a result of oscillation in the atmospheric forcing leading to variations in the isopycnal fluxes of do at the boundaries of the okhotsk sea western subarctic gyre subtropical region the isopycnal surface replacement in the wsg and in changes in the intermediate water formation rate in the okhotsk sea

a model for phase lag of secondary flow in river meanders abstract the phase lag in a meandering channel is the phase difference between the development growth and decay of secondary flow and the channel curvature the secondary flow is predominantly driven by the channel curvature its phase lag behind downstream of the channel pattern is an important feature in the mechanics of flow and the migration pattern of meander bends this paper presents an analytical solution for the phase lag derived based on the mechanics of secondary flow the physical process for this approach is the growth and decay of secondary flow which has a basis different from flow instability used in previous approaches the analytical approach employs simplifying assumptions to focus on the role of secondary flow its limitations in application are described major variables affecting the phase lag are identified to be channel roughness suspended sediment concentration flow depth and meander arc length it is very interesting to note that similar variables for the phase lag have been identified based on different physical processes the results of this study are compared with previous studies as well as laboratory and field data they suggest that phase lags in tight meandering channels are pronounced

flow interaction of meandering river with floodplains a series of laboratory test results are presented concerning the boundary shear stress shear force and discharge characteristics of compound meandering river sections composed of a rectangular main channel and one or two floodplains disposed off to its sides five dimensionless parameters are used to form equations representing the total shear force percentage carried by floodplains a set of smooth and rough sections is studied with an aspect ratio varying from 2 to 5 apparent shear forces on the assumed vertical diagonal and horizontal interface plains are found to be different from zero at low depths of flow and change sign with an increase in depth over the floodplain a variable inclined interface is proposed for which apparent shear force is calculated as zero equations are presented giving proportion of discharge carried by the main channel and floodplain the equations agree well with experimental and river discharge data using the variable inclined interface the error between the measured and calculated discharges for the meandering compound sections is found to be the minimum when compared with that using other interfaces

3d mechanical modeling of the gps velocity field along the north anatolian fault the north anatolian fault naf extends over 1500 km in a complex tectonic setting in this region of the eastern mediterranean collision of the arabian african and eurasian plates resulted in creation of mountain ranges i e zagros caucasus and the westward extrusion of the anatolian block in this study we investigate the effects of crustal rheology on the long term displacement rate along the naf heat flow and geodetic data are used to constrain our mechanical model built with the three dimensional finite element code adeli the fault motion occurs on a material discontinuity of the model which is controlled by a coulomb type friction the rheology of the lithosphere is composed of a frictional upper crust and a viscoelastic lower crust the lithosphere is supported by a hydrostatic pressure at its base representing the asthenospheric mantle we model the long term deformation of the surroundings of the naf by adjusting the effective fault friction and also the geometry of the surface fault trace to do so we used a frictional range of 0 0 0 2 for the fault and a viscosity varying between 10 19 and 10 21 pa s one of the most striking results of our rheological tests is that the upper part of the fault is locked if the friction exceeds 0 2 by comparing our results with geodetic measurements mcclusky et al j geophys res b 105 2000 5695 5719 and tectonic observations we have defined a realistic model in which the displacement rate on the naf reaches v17 mm yr for a viscosity of 10 19 pa s and a fault friction of 0 05 this strongly suggests that the naf is a weak fault like the san andreas fault in california adding topography with its corresponding crustal root does not induce gravity flow of anatolia rather it has the counter intuitive effect of decreasing the westward anatolian escape we find a poor agreement between our calculated velocity field and what is observed with gps in the marmara and the aegean regions we suspect that the simple lithosphere model is responsible for this discrepancy taking into account the weaknesses of these deforming regions should allow us to build a more realistic model that would match ground observations more appropriately on the other hand our results fit well gps measurements in central anatolia setting the basis of modeling crustal strain in turkey b 2003 elsevier science b v all rights reserved

mean and turbulent velocity fields near rigid and flexible plants and the implications for deposition 1 the transport of fine sediment and organic matter plays an important role in the nutrient dynamics of shallow aquatic systems and the fate of these particles is closely linked to vegetation we describe the mean and turbulent flow near circular patches of synthetic vegetation and examine how the spatial distribution of flow is connected to the spatial distribution of suspended sediment deposition patches of rigid emergent and flexible submerged vegetation were considered with two different stem densities for the rigid emergent vegetation flow adjustment was primarily two dimensional with flow deflected in the horizontal plane horizontal shear layers produced a von karman vortex street flow through the patch shifted the vortex street downstream resulting in a region directly downstream of the patch in which both the mean and turbulent velocities were diminished net deposition was enhanced within this region in contrast for the flexible submerged vegetation flow adjustment was three dimensional with shear layers formed in the vertical and horizontal planes because of strong vertical circulation turbulent kinetic energy was elevated directly downstream of the patch consistent with this deposition was not enhanced at any point in the wake this comparison suggests that morphological feedbacks differ between submerged and emergent vegetation further enhanced deposition occurred only in regions where both turbulent and mean velocities were reduced relative to the open channel reduced deposition indicating enhanced resuspension occurred in regions of high turbulence kinetic energy regardless of local mean velocity these observations highlight the importance of turbulence in controlling deposition

sinking fluxes of minor and trace elements in the north pacific ocean measured during the vertigo program as part of the vertical transport in the global ocean vertigo program we collected and analyzed sinking particles using sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 in this paper we present the results of minor and trace element determinations made on these samples minor and trace elements in the sinking material showed 2 trends in flux with depth increasing and constant the sinking particulate phase of some elements al fe mn was dominated by material of lithogenic origin and exhibited flux that was constant with depth and consistent with eolian dust inputs aloha or increasing in flux with depth as a result of lateral inputs from a shelf k2 this shelf derived material also appears to have been confined to very small particles whose inherent sinking rates are slow and residence time within the mesopelagic twilight zone would be consequently long furthermore the flux of this material did not change with substantial changes in the rain of biogenic material from the surface k2 suggesting mechanistic decoupling from the flux of organic carbon and macronutrients micronutrient fe co zn and cu fluxes examined in a 1 d mass balance suggest widely differing sources and sinks in the water column as well as impacts from biological uptake and regeneration for example total fe fluxes into and out of the euphotic zone appeared to be dominated by lithogenic material and far exceed biological requirements the export flux of fe however appeared to be balanced by the eolian input of soluble fe for zn and cu the situation is reversed with atmospheric inputs insufficient to support fluxes and the cycling therefore dominated by the draw down of an internal pool for co the situation lies in between with important but ultimately insufficient atmospheric inputs

paleoseismic evidence of clustered earthquakes on the san andreas fault in the carrizo plain california exposures we have excavated across the san andreas fault contradict the hypothesis that part of the fault in the carrizo plain is unusually strong and experiences relatively infrequent rupture the exposures record evidence of at least seven surface rupturing earthquakes which have been approximately dated by accelerated mass spectrometry radiocarbon analysis of detrital charcoal and buried in situ plants five large earthquakes have occurred since 1218 a d the most recent earthquake event a was the 1857 fort tejon earthquake which we have associated with 6 6 10 m of dextral slip along the main fault trace the penultimate earthquake event b most likely occurred within the period a d 1405 1510 slip from either events b and c combined or from event b alone totals 7 11 m three earthquakes events c d and e occurred in a temporal cluster prior to event b and after approximately a d 1218 the average recurrence interval within this cluster is 73 116 years depending on assumptions events f and g occurred after 200 years b c a depositional hiatus between events e and f may hide evidence of additional earthquakes events b and d within the carrizo cluster of a d 1218 1510 may correlate with events t a d 1329 1363 and v a d 1465 1495 at pallett creek on the mojave segment of the fault this suggests two fault ruptures similar in length to that of 1857 events c and e apparently did not rupture the mojave section which suggests that the carrizo segment has ruptured independently or in combination with segments to the north irregular repeat times of large earthquakes suggest a pattern of clustered events at the end of seismic supercycles

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

interannual variability of the kuroshio extension system and its impact on the wintertime sst field altimetry data from the first 7 yr topex poseidon t p mission october 1992 september 1999 are analyzed to investigate the interannual variability in regions of the kuroshio extension and its southern recirculation gyre large scale interannual changes of the kuroshio extension system are characterized by the oscillation between an elongated state and a contracted state in the elongated state the kuroshio extension has a larger eastward surface transport a greater zonal penetration and a more northerly zonal mean path all these characteristics are closely connected to the presence of an intense zonally elongated southern recirculation gyre in its contracted state the kuroshio extension has a smaller eastward surface transport a more southerly mean path and is accompanied by a weaker southern recirculation gyre during the t p period the kuroshio extension changed from the elongated state in 1992 93 to the contracted state in 1996 97 and back to the elongated state since late 1997 in addition to these large scale changes the mesoscale eddy field also exhibited prominent interannual changes in the kuroshio extension region in the upstream region between the izu ridge and the shatsky rise the eddy kinetic energy level was generally low while the kuroshio extension was in its elongated state and high while in the contracted state downstream of the shatsky rise on the other hand the eke level was high low when the kuroshio extension was in the elongated contracted state the large scale interannual changes in the kuroshio extension system have a significant impact on the regional wintertime sst anomaly field the warm cold wintertime sst anomalies tend to persist in years when the kuroshio extension is in its elongated contracted state a diagnostic analysis of the surface ocean heat balance indicates that the nonseasonal geostrophic advection by the ocean circulation works to reduce increase the wintertime sst anomalies when the kuroshio extension changes from an elongated contracted state to a contracted elongated state the sst anomalies associated with the large scale changes of the kuroshio extension have an area averaged peak topeak amplitude of 18c and appear independent of the interannual sst changes in the tropical pacific ocean

analytical solution of the depth averaged flow velocity in case of submerged rigid cylindrical vegetation a new model for the depth averaged velocity for flow in presence of submerged vegetation is developed the model is based on a two layer approach where flow above and through the vegetation layer is described separately vegetation is treated as a homogeneous field of identical cylindrical stems and the flow field is considered stationary and uniform it is demonstrated that scaling considerations of the bulk flow field can be used to avoid complications associated with smaller scale flow processes and that still the behavior of depth averaged flow over vegetation is described accurately the derived scaling expression of the average flow field is simple in form it follows fundamental laws of fluid flow and it shows very good agreement with laboratory flume experiments the new model can be used for quick evaluation of a river s hydraulic response in cases where vegetated floodplains are inundated

orientation of the stress field surrounding the creeping section of the san andreas fault evidence for a narrow mechanically weak fault zone we determine how the orientations of the principal stresses change with distance from the creeping section of the san andreas fault saf our data are 2392 earthquake focal mechanisms which are grouped according to distance from the saf into 33 bins parallel to fault strike the width of the bins are dictated by the spatial organization and density of the seismicity only events with m 1 5 depth 2 km and well constrained focal mechanisms are used the focal mechanisms are inverted simultaneously for the orientations and relative amplitudes of the principal stresses using two different inversion programs a bootstrap resampling method provides confidence limits on the stress orientations our general result is that the maximum horizontal compression lies mostly at high angles to the saf except in a narrow zone on the fault no wider than 1 3 km in which it appears to lie at a smaller angle 45 from the fault strike in particular the maximum horizontal compression lies at a high angle to the saf trend immediately adjacent to the fault this stress state is most readily interpreted as due to a narrow mechanically weak saf in this region the narrowness of this zone contrasts with the region wider than 20 30 km of rotated stresses found surrounding the saf in southern california hardebeck and hauksson 1999 suggestive of different mechanical behaviors of the saf in these two regions this approach may provide a way to define the width of the mechanically weak part of faults

persistently declining oxygen levels in the interior waters of the eastern subarctic pacific abstract fifty years of measurements at ocean station papa osp 50 n 145 w show trends in the interior waters of the subarctic pacific that are both impacted by short term few years to bi decadal atmospheric or ocean circulation oscillations and by persistent climate trends between 1956 and 2006 waters below the ocean mixed layer to a depth of at least 1000 m have been warming and losing oxygen on density surfaces found in the depth range 100 400 m 26 3 27 0 the ocean is warming at 0 005 0 012 c y 1 whereas oxygen is declining at 0 39 0 70 mol kg 1 y 1 or at an integrated rate of 123 mmol m 2 y 1 decrease of 22 over 50 years during this time the hypoxic boundary defined as 60 mol o 2 kg 1 has shoaled from 400 to 300 m in the alaska gyre the 26 2 isopycnal occasionally ventilates whereas at osp 26 0 has not been seen at the ocean surface since 1971 as the upper ocean continues to stratify to interpret the 50 year record at osp the isopycnal transport of oxygenated waters within the interior of the subarctic pacific is assessed by using a slightly modified no parameter broecker w 1974 no a conservative water mass tracer earth and planetary science letters 23 100 107 the highest nitrate oxygen signature in interior waters of the north pacific is found in the bering sea gyre western subarctic gyre and east kamchatka current region as a consequence of winter mixing to the 26 6 isopycnal by mixing with low no waters found in the subtropics and okhotsk sea this signature is diluted as waters flow eastward across the pacific evidence of low no waters flowing north from california is seen along the coasts of british columbia and se alaska oxygen in the subsurface waters of the alaskan gyre was supplied 60 by subarctic and 40 by subtropical waters during woce surveys whereas such estimates are shown to periodically vary by 20 at osp other features discernable in the osp data include periods of increased ventilation of deeper isopycnals on an 18 year cycle and strong short term few month variability caused by passing mesoscale eddies the potential impacts of declining oxygen on coastal ecosystems are discussed

secondary current and river meander formation a small perturbation stability analysis is developed for investigation of the role of the secondary current accompanying channel curvature in the initiation and early development of meanders of alluvial and ice or rock incised streams a small sinusoidal perturbation in the channel alignment of an initially straight prismatic channel is introduced the velocity of the secondary flow is calculated for uniform quasi steady flow conditions by application of the equation of the conservation of moment of momentum the formulation is then closed by introducing the assumption that the differential between the outer and inner banks rate of boundary erosion dissolution or melting for incised channels or sediment discharge for alluvial channels is proportional to the strength of the secondary flow this formulation leads to a linear differential equation which is solved for its orthogonal components which give the rates of meander growth and downstream migration it is shown that the amplitude of the meanders tends to increase and that the meanders migrate downstream the dominant wavelength and the corresponding phase shift between channel meandering and the velocity of the spiral motion are calculated as those corresponding to the fastest growth rate the results are found to be in good agreement with data reported by others

turbulent open channel flows with variable depth across the channel the flow of water in straight open channels with prismatic complex cross sections is considered lateral distributions of depth mean velocity and boundary shear stress are derived theoretically for channels of any shape provided that the boundary geometry can be discretized into linear elements the analytical model includes the effects of bed generated turbulence lateral shear turbulence and secondary flows experimental data from the science and engineering research council serc flood channel facility are used to illustrate the relative importance of these three effects on internal shear stresses new experimental evidence concerning the spatial distribution of reynolds stresses yx and zx is presented for the particular case of compound or two stage channels in such channels the vertical distributions of zx are shown to be highly nonlinear in the regions of strongest lateral shear and the depth averaged values of yx are shown to be significantly different from the depth mean apparent shear stresses the importance of secondary flows in the lateral shear layer region is therefore established the influence of both reynolds stresses and secondary flows on eddy viscosity values is quantified a numerical study is undertaken of the lateral distributions of local friction factor and dimensionless eddy viscosity the results of this study are then used in the analytical model to reproduce lateral distributions of depth mean velocity and boundary shear stress in a two stage channel the work will be of interest to engineers engaged in flood channel hydraulics and overbank flow in particular

double averaging concept for rough bed open channel and overland flows applications the paper briefly outlines the double averaging methodology for studying environmental rough bed flows it focuses on the applications of this methodology in environmental hydraulics by providing several examples illustrating advantages of this methodology over conventional approaches examples include 1 identification of specific flow layers and flow types 2 vertical distribution of the double averaged velocity between the roughness tops and troughs 3 vertical distribution of momentum fluxes and sinks for typical roughness types due to turbulence mean flow heterogeneity secondary currents form drag and viscous drag 4 estimates of form induced dispersive stresses and evaluation of their structure using quadrant analysis and 5 closure development for mass transfer uptake processes for stream periphyton these examples illustrate the advantages of the double averaging methodology over conventional approaches as well as highlight its potential for studying flows over very rough beds hig