the undrained response of sands with additions of particles of various shapes and sizes as a natural deposit sand is rarely found clean that is without fractions of silt or clay the engineering behaviour of two different host sand gradations mixed with additions of particles of various shapes and sizes is compared with that of clean sand anisotropically consolidated specimens are sheared in triaxial compression and extension at their loosest initial state resulting from the same depositional method namely air pluviation additive materials at contents less than 2 5 by weight can dramatically change the undrained behaviour of the host sand the addition of rotund particles e g silt should be distinguished from that of flat or platy particles of different size e g kaolin silt or sand size mica the importance of shape and location of additives in modifying the sand structure is not reflected in measures such as void ratio mixtures of both sands with silt size mica exhibit the most unstable response although these had the lowest values of void or granular void ratio the undrai

seismically active fracture zones and distribution of large accumulations of metals in the central part of andean south america the analysis of the geometry of distribution of earthquake foci in the central part of andean south america between 18 and 34 s made the delineation of several seismically active fracture zones in the continental wedge overlying the subducting nazca plate possible correlation of their position with the distribution of hypogene accumulations of metals revealed that the majority of large mineral deposits and mining districts are situated in the outcrops of these fracture zones we present geometrical documentation map of epicentres vertical and longitudinal cross sections of the most important fracture zones and data on mineralogical composition genetic type and available radiometric ages of mineral deposits sixteen mining districts in chile and 24 in argentina were attributed to the seismically active fracture zones major mining districts and individual large mineral deposits occur in six seismically active fracture zones roughly parallel to the axis of the peru chile trench carachas portillo choquelimpie iquique domeyko rio blanco los bayos and farellones f z in six fracture zones roughly perpendicular to the trench el salvador maricunga jaroma ujina tumbaya and incahuasi leon muerto f z and in two fracture zones oriented at an angle of about 45 in relation to the direction of the presently active andean subduction aconcagua and sierra del volcan f z the occurrences of large mineral deposits of different ages show that these fracture zones were also active in the geological past and represent sites of permanent re opening of paths allowing ore bearing solutions and long term accumulation of large amounts of metals to occur in relatively restricted domains of the earth s crust the mining districts with dated mineral deposits are arranged into four periods of hypogene mineralization upper miocene pliocene upper oligocene middle miocene upper eocene middle oligocene lower paleocene upper eocene these periods of metallogenic activity correlate well with four supposed andean subduction cycles active in the tertiary the occurrence of mineral deposits of different ages in recently active fracture zones can be used as an important evidence in favour of long term spatial permanence and activity of these zones and as a guide for the discovery of further mineral deposits hidden under young sedimentary and volcanic cover in the fracture zones

magmatic anhydrite in plutonic rocks at the el teniente cu mo deposit chile and the role of sulfur and copper rich magmas in its formation anhydrite occurs along with biotite feldspars quartz fe oxides and sulfides in fine grained igneous rocks that form the small porphyry a stock at el teniente these minerals crystallized together in the space generated by the intrusion of this stock and they do not replace preexisting phases planar crystal boundaries between anhydrite and other phases as well as the fact that plagioclase and biotite are fresh and unaltered also suggest that anhydrite is an igneous phase and not the product of secondary hydrothermal alteration plagioclase is unusually na rich ranging from oligoclase in mafic varieties of these rocks with 20 percent biotite to albite in more felsic samples with 20 percent these unusual anhydrite bearing plutonic rocks which contain up to 3 wt percent s and 0 5 wt percent cu are isotopically similar to all other igneous rocks related to the deposit these rocks formed during a late miocene period of regional compressive deformation with no coeval volcanic activity in the area of the deposit which prevented devolitalization of the oxidized parent magma in the large productive magma chamber inferred to have underlain el teniente at 4 km below the paleosurface this allowed igneous fractionation involving the recharge of mantle derived mafic magmas into the base of the chamber as well as volatile transfer and concentration near its roof to produce the cu and s rich magmas that formed the anhydrite bearing intrusive rocks

effects of nonplastic fines on static liquefaction of sands des essais triaxiaux en compression non draines ont ete effectues sur des echantillons reconstitues de sable du nevada et d ottawa avec variation systematique de la teneur en fines particules inferieures a 0 074 mm afin d evaluer l effet de la fraction fine sur le potentiel de liquefaction statique lors d un chargement monotonique les fines etaient non plastiques les resultats indiquent clairement que la presence de fines peut augmenter considerablement le potentiel de liquefaction statique des quatre sables propres etudies lorsqu on utilise la technique du montage a sec avec un entonnoir les fines semblent creer dans le sol une structure particulaire tres compressible ce qui accroit ainsi le potentiel de liquefaction alors meme que la densite augmente accroitre la teneur en fines d un sable propre peut aboutir a l augmentation du potentiel de liquefaction jusqu a un seuil maximum pour lequel les fines dominent le comportement non draine du sol a ce point la le potentiel de liquefaction tend a devenir constant vis a vis de l indice de densite on a trouve que la liquefaction statique complete pouvait intervenir a un indice de densite superieur a 60 pour des teneurs en fines elevees

island wakes and headland eddies a comparison between remotely sensed data and laboratory experiments island wakes and headland eddies in coastal waters are identified from spaceborne and airborne remotely sensed imagery in the visible wavelengths the imagery were obtained for the bristol and english channels united kingdom which are characterized by high tidal currents and levels of turbidity suspended matter in the surface waters is used as a passive tracer for the flow features scaling parameters e g the reynolds ekman and rossby numbers obtained from the depth averaged equation of motion are presented based upon information on oceanographic conditions at the times of the overpasses the parameters are compared then with data obtained from laboratory model investigations presented by other experimenters in the published literature the remotely sensed data demonstrate that in coastal waters with nonuniform obstacles and bathymetry for a given ekman number the flow regimes occur at a lower rossby number than might be expected from laboratory experiments in the absence of a method for the accurate determination of the horizontal eddy viscosity hence the reynolds number it is concluded that an island wake parameter wolanski et al 1984a should be adopted to describe such features in coastal waters

the correlation between surface drifters and coherent structures based on high frequency radar data in monterey bay this paper investigates the transport structure of surface currents around the monterey bay ca region currents measured by radar stations around monterey bay indicate the presence of strong spatial and temporal nonlinear patterns to understand the geometry of the flow in the bay lagrangian coherent structures lcs are computed these structures are mobile separatrices that divide the flow into regions of qualitatively different dynamics they provide direct information about the flow structure but are geometrically simpler than particle trajectories themselves the lcs patterns were used to reveal the mesoscale flow conditions observed during the 2003 autonomous ocean sampling network aosn ii experiment drifter paths from the aosn experiment were compared to the patterns induced by the lcs computed from high frequency radar data we verify that the fate of the drifters can be better characterized based on the lcs than direct interpretation of the current data this property can be exploited to optimize drifter deployment

characterizing frontal eddies along the east australian current from hf radar observations the east australian current eac dominates the ocean circulation along south eastern australia however little is known about the submesoscale frontal instabilities associated with this western boundary current one year of surface current measurements from hf radars in conjunction with mooring and satellite observations highlight the occurrence and propagation of meanders and frontal eddies along the inshore edge of the eac eddies were systematically identified using the geometry of the high spatial resolution 1 5 km surface currents and tracked every hour cyclonic eddies were observed irregularly on average every 7 days with inshore radius 10 km among various forms of structures frontal eddies associated with eac meanders were characterized by poleward advection speeds of 0 3 0 4 m s migrating as far as 500 km south based on satellite imagery flow field kinematics show that cyclonic eddies have high rossby numbers 0 6 1 9 and enhance particle dispersion patches of intensified surface divergence at the leading edge of the structures are expected to generate vertical uplift this is confirmed by subsurface measurements showing temperature uplift of up to 55 m over 24 h and rough estimates of vertical velocities of 10s of meters per day while frontal eddies propagate through the radar domain independently of local wind stress upfront wind can influence their stalling and growth and can also generate large cold core eddies through intense shear such coherent structures are a major mechanism for the transport and entrainment of nutrient rich coastal or deep waters influencing physical and biological dynamics and connectivity over large distances

forewarning of static liquefaction landslides abstractstatic liquefaction failure and the ensuing flow slide of slopes have produced significant damages to structures and even loss of lives based on a very large number 1 632 of laboratory s

on the east australian current variability encroachment and upwelling 1 observations from an intensive oceanographic field program which took place in 1998 1999 about the separation point of the east australian current eac show significant spatial and temporal variability of the eac upstream of the separation point southward flowing currents are strong with subinertial velocities of up to 130 cm s 1 in the near surface waters whereas downstream currents are highly variable in both strength 1 70 cm s 1 and direction upwelling is observed to occur through both wind driven and current driven processes with wind effects playing a lesser role by contrast the encroachment of the eac upon the coast has a profound effect on the coastal waters accelerating the southward alongshore currents and decreasing the temperature in the bottom boundary layer bbl by up to 5 degreesc as the axis of the jet moves onshore negative vorticity increases in association with an increase in nonlinear acceleration during this time bottom friction is increased the burger number is reduced and the bbl shut down time lengthens the observed upwelling is attributed to enhanced onshore ekman pumping through the bbl resulting from increased bottom stress as the southerly flow accelerates when the eac encroaches across the continental shelf

tectonic trigger for the formation of late miocene cu rich breccia pipes in the andes of central chile during the late miocene the decreasing angle of subduction below the andes of central chile caused a reduction in the influx of new magma and heat into the base of magmatic systems that had been active throughout the miocene this led to their cooling and solidification triggering the release of large volumes of metal rich magmatic fluids from middle and upper crustal magma chambers and generating a group of economically significant cu rich breccia pipes the sr and nd isotopic compositions of the magmatic fluids that formed these brecccas determined from breccia matrix minerals were variable implying that these fluids were not exsolved from a specific cu porphyry magma as is often invoked to explain andean cu deposits instead the formation of the late miocene deposits in central chile was tectonically triggered by cooling of a variety of magma types during the last stages of existence of long lived andean magmatic systems as both subduction angle and as a result subarc magma supply decreased

the hydraulics of an evolving upwelling jet flowing around a cape upwelling jets flow alongshore in approximate geostrophic balance with the onshore pressure gradient induced by coastal upwelling observations of such jets have shown that they often move offshore downstream of capes leaving a pool of upwelled water inshore comparisons are made between this behavior and the hydraulic transition of a potential vorticity conserving coastal current as it passes a topographic anomaly at which it is exactly critical to long coastal trapped waves an analytic 1 5 layer model of coastal hydraulics with constant potential vorticity in each layer predicts flow fields i e jet separation in critical situations that resemble observations when scales approximate cape blanco on the oregon coast separation occurs at a jet transport of around 0 76 3 106 m3 s21 similar to observed transports time dependent semigeostrophic calculations suggest that during an upwelling season the jet would evolve from a weak flow which was subcritical everywhere and symmetric about the cape to an exactly critical state that made a transition from subcritical to supercritical structure at the head of the cape the predicted flow field at critical transition consists of a narrow upwelling jet upstream of the cape that moves offshore and broadens at the cape this critical state would be accompanied by a downstream jump back to subcritical conditions further upwelling favorable winds would lead to transient waves that propagated upstream and downstream modifying the upstream and downstream conditions and restoring criticality thus the head of the cape exerts hydraulic control on the flow and prevents the jet transport from increasing above its critical level inherent in the hydraulic approach is the assumption that alongshore scales are large for realistic alongshore scales solutions modified by coastline curvature suggest that the convexity of the head of a cape slightly inhibits the transition to a strongly upwelled downstream state by increasing the required critical transport in the presence of topographic features with finite alongshore scale the hydraulic approach can be used to construct a flow field although this flow field has an inherent error arising from the implicit assumptions regarding scales estimation of this error for topography representing cape blanco suggests that in places the cape is rather abrupt for hydraulic theory to be valid

subduction of the nazca ridge and the inca plateau insights into the formation of ore deposits in peru a large number of ore deposits that formed in the peruvian andes during the miocene 15 5 ma are related to the subduction of the nazea plate beneath the south american plate here we show that the spatial and temporal distribution of these deposits correspond with the arrival of relatively buoyant topographic anomalies namely the nazca ridge in central peru and the now consumed inca plateau in northern peru at the subduction zone plate reconstruction shows a rapid metallogenic response to the arrival of the topographic anomalies at the subduction trench this is indicated by clusters of ore deposits situated within the proximity of the laterally migrating zones of ridge subduction it is accordingly suggested that tectonic changes associated with impingement of the aseismic ridge into the subduction zone may trigger the formation of ore deposits in metallogenically fertile suprasubduction environments c 2005 elsevier b v all rights reserved

effect of the mode of shear on static liquefaction analysis abstractthe current practices for determining the peak yield and postliquefaction critical undrained shear strength of liquefiable cohesionless soils for grounds subject to static shear stress e g sloping grounds or grounds beneath foundations require either a suite of costly laboratory shear tests on undisturbed field samples or empirical correlations with in situ penetration tests which do not account for the effect of the shearing mode on soil behavior improved correlations are developed in this study for estimating the undrained triggering and postliquefaction shear strengths of cohesionless soils which are based on the most reliable field liquefaction data from past cases of liquefaction flow failures and soil shearing behavior observed in a large database of 600 laboratory shear tests for different modes of shear the proposed method accounts for the variations in the mode of shear when providing estimates of the undrained triggering and postliquefaction strengths mobilized in static liqu

frac sand crushing characteristics and morphology changes under high compressive stress and implications for sand pack permeability sand consisting of round quartz grains is widely used as a proppant during hydraulic fracturing to produce natural gas from tight shale formations this paper presents results from sand characteriz

subsurface recirculation and larval retention in the lee of a small headland a variation on the upwelling shadow theme 1 the interaction of alongshore coastal currents with large headlands has been shown to increase the retention of planktonic organisms through the formation of headland eddies or upwelling shadows in their lee this study investigates the circulation within bodega bay in the lee of a small headland in an upwelling region and the potential for retention of plankton during the upwelling season of 2004 time series of temperature and velocity were recorded throughout bodega bay conductivity temperature depth ctd surveys were conducted and surface drifters were released during upwelling downwelling and relaxation conditions postlarval settlement was monitored daily over two periods coinciding with ctd surveys under strong upwelling favorable conditions wind driven surface currents were equatorward both offshore and throughout the bay however there was significant current shear along the eastern shore of the bay where cold bottom waters move poleward counter to the direction of the wind driven surface flow during downwelling and relaxation conditions flow was poleward throughout the water column along the eastern shore of the bay postlarvae settled during all wind conditions but greatest settlement was observed at the onset of upwelling favorable conditions while no typical upwelling shadow is evident in the lee of the bodega headland subsurface recirculation driven by the alongshore flow past bodega head may facilitate the retention of plankton in the bay previous studies have generally focused on large headlands however it is likely that other small embayments in the lee of small headlands may also provide retention opportunities for planktonic organisms in upwelling regions

subinertial currents on the southern califoinia shelf abstract subinertial currents on the southern california shelf are investigated using observations from a current meter array deployed near san diego during the summer fall and winter of 1978 79 this region is characterized by weak winds order 1 2 m s 1 and thus other driving mechanisms for the subinertial currents may be important a simplified depth averaged longshore momentum equation consisting of a balance between current accelerations the adjusted sea level asl gradient and the wind and bottom stress is examined the asl gradient is estimated using sea level and atmospheric pressure observations separated by 350 km a linear parameterization of the bottom stress is used with a drag coefficient of 5 10 4 m s 1 during fall and winter the first order balance of terms in the longshore momentum equation over the inner shelf 15 m depth is between the wind and bottom stress over the outer shelf 60 m the primary balance is between the asl gradient and the bottom stress at midshelf 30 m bo

horizontal spatial and temporal distribution patterns of nearshore larval fish assemblages at a temperate rocky shore there have been no previous studies of the composition of nearshore larval fish assemblages along the coast of portugal we aimed to describe the composition and horizontal distribution patterns of larval fish assemblages and their temporal dynamics near a rocky reef at depths shallower than 13 m inshore and at two miles 3 70 km from shore offshore as well as along transects perpendicular to the shoreline from the reef to 10 miles offshore 18 52 km samples were taken using 5 min sub surface trawls at the rocky shore of the arrabida marine park w portugal a total of 1021 larvae were collected belonging to 61 taxa inshore and to 29 taxa offshore along transects 626 larvae of 52 taxa were collected most larvae belonged to coastal species associated with rocky reefs total larval abundance and diversity were higher from may to july which is consistent with the spawning activity of adults diversity and total larval abundance decreased significantly with increasing distance from shore both in the inshore offshore comparison and in the transects where this decrease was evident at a very small spatial scale within the first mile from the reef species assemblages differed in the pattern of distribution with most species clearly associated to the extreme nearshore the distribution patterns obtained were independent of the spawning mode of species results are discussed in the light of the possible physical mechanisms that can potentially act at the arrabida marine park to facilitate larvae retention and the role of larval behaviour

effect of grain shape and angularity on the undrained response of fine sands the objective of this paper is to discuss the effect of grain shape and angularity on the undrained behaviour of sands four fine to medium d50 0 15 0 29 mm and uniform sands were examined these sands have similar and or identical grading curves but differ with respect to the angularity of their grains under the electron scanning microscope two sands have rounded grains and the other two have subangular to angular grains for sands with rounded grains evidence of undrained behaviour undergoing systematic weakening shear stress reduction after a transient peak deviator stress is provided by torsional hollow cylinder tests however sands with the same grading curve and void ratio but angular grains show stable response with a continuous increase in strength after a transient peak a small variation in the sand gradation i e d50 0 22 0 07 mm does not appear to alter the pattern of undrained response described earlier with the angular sand d50 0 15 exhibiting stable response to she

dem modelling of mini triaxial test based on one to one mapping of sand particles this paper presents a discrete element method simulation of mini triaxial tests on a sand with realistically shaped grains it compares the results with physical experiments at multiple length scal

undrained anisotropy and principal stress rotation in saturated sand this paper describes an investigation carried out in a new hollow cylinder apparatus into anisotropy and the effects of principal stress rotation in a medium loose sand tested under undrained conditions principal stresses have been rotated at a constant shear stress during both monotonie and cyclic loading the experimental observations are described and then explained within a framework based on the concept of state boundary surfaces the over riding importance of initial anisotropy in determining the response of the sand to rotations in principal stress directions is demonstrated pore pressures are shown to be generated by rotation of principal stress directions at constant shear stress and their accumulation during cyclic principal stress rotation can lead to failure l article presente une etude de l anisotropie effectuee dans un nouvel appareil creux cylindrique et decrit les effets de la rotation de la contrainte principale dans un sable moyennement l che teste dans des conditions non drainees l

modis imagery of turbid plumes in san diego coastal waters during rainstorm events abstract data of normalized water leaving radiance nlw obtained from the moderate resolution imaging spectroradiometer modis on the aqua satellite at spatial resolution of 250 m band 1 centered at 645 nm and 500 m band 4 at 555 nm are used to study turbid plumes in coastal waters of southern california during rainstorm events in winter of 2004 2005 our study area includes san diego coastal waters which extend approximately 25 km offshore between point loma and 10 km south of the us mexican border these waters are influenced by terrigenous input of particulate and dissolved materials from san diego and tijuana watersheds and non point sources along the shore optimum threshold values of satellite derived normalized water leaving radiances at both wavebands were established for distinguishing the plume from ambient ocean waters these threshold values were determined by searching for a maximum correlation between the estimates of satellite derived plume area calculated using a broad range of nlw values and the environmental variables characterizing rainfall river discharge wind and tides a correlation analysis involving the amount of precipitated water accumulated during a storm event over the san diego and tijuana watersheds was selected as the basis for final determinations of the optimum threshold nlwthr and subsequent calculations of the plume area by applying this method to a sequence of modis imagery we demonstrate the spatial extent and evolution of the plume during rainstorm events under various conditions of precipitation river discharge wind forcing and coastal currents

particle obstruction and crushing of dredged calcareous soil in the nansha islands south china sea abstract the bearing capacity of the dredged calcareous soil in the nansha islands south china sea typically exceeds that of terrigenous dredger fill furthermore the shear strength of calcareous soil exceeds that of siliceous sand under identical conditions it is mainly caused by the interparticle obstruction between calcareous soil particles to explore the obstruction mechanism of calcareous soil particles a series of triaxial tests were performed on calcareous soils under both consolidated undrained cu and consolidated drained cd conditions respectively particle shape characteristics and particle crushing were also investigated to study the formation mechanism of obstruction force test results indicate that irregular particle shape is the prerequisite for the emergence of particle obstruction in calcareous soils a simple obstruction dilatation model was developed to describe the relationship among particle obstruction dilation and particle crushing the obstruction force varies greatly during the shearing process which is mainly influenced by particle size and stress level under low confining pressure particle obstruction results in dilatation and increases internal friction angle in contrast obstruction causes particle breakage increases the apparent cohesion and ultimately decreases the effective internal friction angle under high confining pressures the particle obstruction of calcareous soil noticeably improves shear strength therefore the effect of particle obstruction on strength should be considered in coral reef engineering design work

observations of divergence and upwelling around point loma california 1 historical records of near surface water temperatures in the southern californian bight often show a preferential cooling in the lee of headlands such as point dume palos verdes and point loma at times this cooler water is associated with an increase in chlorophyll a as is evident in satellite images of ocean color from the region here we combine hydrographic data from a 1 day cruise aboard the rv roger revelle a precursor to the 0304 california cooperative oceanic fisheries investigations calcofi cruise with high frequency hf radar codar measurements satellite images and long term thermistor records of near surface temperature to identify a small scale isolated upwelling in the lee of point loma 32 5 n associated with the more saline water downstream of the headland are higher nutrient concentrations an increase in chlorophyll a concentration and a bloom of chain forming diatoms indicative of a mature upwelling system it is suggested that this upwelling is not primarily due to local or remote wind forcing but rather to the divergence of the prevailing southerly flow as it passes the point loma headland time series of surface vorticity calculated from hf radar measurements of sea surface velocity show that as the flow separates from the headland relative vorticity increases offshore of the cape inshore the time series of divergence convergence shows a tendency toward divergence at the surface indicating a preferential upwelling which appears to raise the thermocline thus resulting in a flux of cold nutrient rich water to the surface in the presence of high nutrients and light photosynthetic organisms bloom in these upwelled waters as they are advected away from the headland and offshore by the prevailing surface currents

ocean response to wind sheltering in the southern california bight 1 a particularly warm surface oceanic wake persisted during the period 6 16 june 1999 in the south eastern part of santa catalina island in the southern california bight from satellite images regional atmospheric model results and hydrographic measurements around catalina island a strong correlation appears between observed sea surface temperature wind stress and surface stratification it is suggested that the warm island wake was probably due to lower turbulent mixing rates associated with wind sheltering effect we argue that the sheltering effect may also account for a portion of the relatively warm sea surface temperature characteristic of the whole bight opposing previous arguments that temperature evolution of the surface ocean in this region is primarily driven by lateral advective fluxes

water mass analysis and alongshore variation in upwelling intensity in the eastern great australian bight 1 a study of climatological and conductivity temperature depth ctd data for 2004 is made to provide a conceptual model of upwelling for the eastern region of the great australian bight in particular the data and other studies provide strong evidence that shelf break upwelling is confined to the southwest kangaroo island region and does not occur farther to the west off the eyre peninsula rather the upwelled water is likely to remain in a kangaroo island pool until subsequent upwelling events draw the water to the shallower and surface coastal regions of the eastern bight in this manner the surface upwelling apparent off the bonney coast kangaroo island and the eastern great australian bight gab can appear to be simultaneous moreover it appears likely that the water within the kangaroo island pool remains nutrient rich support for this model comes from ctd sections collected in 2004 that show that the upwelled signal cool 26 kg m 3 diminishes in width and intensity with increasing distance from kangaroo island the pattern of fluorescence is similar to that for temperature in the upwelled plume and indicates that the kangaroo island pool remains nutrient rich relatively low oxygen concentrations may indicate a previous bloom the warmest water is found near the shelf break along with very low values of fluorescence and relatively higher levels of oxygen suggesting nutrient limited growth of phytoplankton these data also support the notion that the upwelled nutrient rich water is supplied from the kangaroo island pool and not by shelf break upwelling in the eastern gab anomalously salty and fresh water is identified as resulting from evaporation in coastal bays and groundwater aquifer discharge

lagrangian and eulerian characterization of two counter rotating submesoscale eddies in a western boundary current in recent decades high spatial resolution ocean radar and satellite imagery measurements have revealed a complex tangle of submesoscale filaments and eddies in the surface velocity temperature and chlorophyll a fields we use a suite of high resolution data to characterize two counter rotating short lived eddies formed at the front between the warm east australian current eac and temperate coastal waters 308s eastern australia in this region submesoscale filaments and short lived eddies are dynamically generated and decay at time scales of hours to days dominant cyclonic filaments of o 1 rossby number formed along frontal jets and eddy boundaries generating localized ageostrophic circulations at the submesoscale measurements of over ocean wind direction and surface currents from high frequency radars reveal the influence of the short term small scale wind forcing on the surface circulation enhancement of the horizontal shear frontal jet destabilization and the generation and decay of the cyclonic eddy by contrast the anticyclonic eddy formation was most likely associated with eac mesoscale instability and anticyclonic vorticity lagrangian tracks show that surface particles can be temporarily trapped in the eddies and frontal convergent zones limiting their transport mixing between eac derived and coastal waters was increased along the frontal regions and particles starting at the divergent regions around the eddies experienced significant dispersion at submesoscales the cyclonic cold core eddy entrained high chlorophyll a shelf waters on its convergent side suggesting spiral eddy cyclogenesis

chlorophyll variability in eastern boundary currents the first three years of seawifs data 199 2000 provide the most complete quantification to date of chlorophyll seasonal variability along the full latitudinal ex tent of the four major eastern boundary currents ebcs comparisons to previously published chlorophyll seasonal climatologies deduced from the relatively sparse coverage provided by the coastal zone color scanner czcs show significant differences in both southern hemisphere ebcs while northern hemisphere regions are qualitatively simi lar comparisons between chlorophyll and cross shelf ek man transport seasonal cycles calculated from coincident satellite scatterometer data show seasonal maxima have similar phases over most of the california current at higher 32os latitudes in the peru chile and benguela currents 30os and at lowest latitudes 20on in the canary current latitudinal zones within which phases diverge are indicative of alternate and or more distant forcing

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment 2 simulations and comparisons with observations 1 this is the second part of a modeling study of wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code gan and allen 2002 analyzed the shelf flow response to idealized wind stress forcing in a process oriented study the study here applies forcing from observed winds and heat flux for april may 1982 and compares the model results with moored current and temperature measurements the princeton ocean model pom is used in a three dimensional limited area domain with a high resolution curvilinear grid approximately 1 km horizontal spacing 60 vertical levels and realistic coastline and bottom topography the objectives of the study are to simulate the response of the shelf circulation field to time varying observed wind stress and heat flux to compare model results with oceanographic observations to establish confidence in the model and to subsequently analyze the model fields and the model dynamical balances to help understand the behavior of the observed flow the model variables show overall good agreement with corresponding observations similar to the conclusions by gan and allen 2002 it is found that the alongshore variability of upwelling is mainly controlled by the interaction of the wind forced shelf flow with the coastline and bottom topography different dynamical regimes in the regions north and south of the coastal capes formed by pt reyes and pt arena and in the more uniform region between these capes are identified and investigated the results demonstrate that the coastal capes play a dominant role in causing alongshore variability of the upwelling flow including the setup of an alongshore pressure gradient that forces northward currents during relaxation of southward upwelling favorable winds an analysis of the balance of terms in the equation for potential temperature indicates that across shore temperature advection is the major contributor to the cooling of coastal water during upwelling with a larger magnitude to the south of the capes to the north of the capes however alongshore temperature advection is the dominant contributor to the colder water near the coast

relationship between copper tonnage of chilean base metal porphyry deposits and os isotope ratios re os isotopes in pyrite and chalcopyrite from early high temperature hypogene alteration assemblages in chilean porphyry copper deposits identify the source of os and by inference cu in these ore systems typical concentrations for os in both pyrite and chalcopyrite are between 7 and 30 ppt 10 12 g g and for re between 0 200 and 10 ppb 10 9 g g re os isochrons yield ages and initial 187 os 188 os ratios for the sulfides the isotopic data reflect the relative contributions of copper from the mantle and crust in chilean porphyry copper deposits seven ore deposits that reside in different tectonic terranes and represent distinct epochs of mineralization in chile were studied the initial osmium ratios of the first stage of mineralization at each of the deposits range from 0 15 to 5 these values are more radiogenic than the present chondritic mantle 0 13 and indicate significant crustal contributions of os to the magmatic and or hydrothermal systems there is a strong correspondence between the total copper content and initial os isotopic ratios in base metal porphyry deposits the larger deposits have lower initial os ratios than the smaller less significant deposits this relationship implies that larger deposits acquire a greater proportion of os from the mantle the initial os ratio of samples in the central segment of porphyry copper deposits of northern chile also decreases with decreasing age of the deposit a plausible interpretation of the re os data is that the later and larger deposits use regional tectonic and structural features that allow sampling of deeper more primitive magmatic sources

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

the influence of tidal range on the exchange between san diego bay and the ocean the tidal exchange between a bay and the ocean often results from a process termed tidal pumping caused by an asymmetry between the flow during the ebb and flood tides for many bays the ebb flow is concentrated into a jet which occupies the region just offshore from the mouth of the bay while the flood flow is drawn in rather radially from the region all around the mouth a significant variation in tidal exchange with tidal range is based on the notion that the length scale of the ebb jet increases more rapidly than the length scale of the flood withdrawal zone as the tidal range increases exchange between san diego bay and the pacific ocean was quantified using a combination of flow measurements by acoustic doppler current profiling and tracer measurements using a naturally occurring ultraviolet fluorescence tracer we found that variations in exchange with tidal range could be isolated by separately evaluating the ebb and flood tidal transport budgets the tracer transport during the ebb increased rapidly with tidal range while during the flood tide the transport increased more gradually the resulting difference in tidal transport between the ebb and flood accounts for the exchange between the bay and ocean for weak tides the exchange tends to increase rapidly with increasing tidal range while for stronger tides the exchange is more constant an empirical equation for the tidal exchange developed from the measurements is consistent with theoretical tidal pumping models and supports the concept that the exchange at the mouth of san diego bay is dominated by tidal pumping

mechanisms of mid to outer shelf transport of shoreline released tracers abstracttransport of shoreline released tracer from the surfzone across the shelf can be affected by a variety of physical processes from wind driven to submesoscale with implications for shorelin

mapping ocean outfall plumes and their mixing using autonomous underwater vehicles this paper reports on our experiences developing methods to survey an ocean outfall discharge plume using an autonomous underwater vehicle auv the mobility of an auv provides a significant advantage in surveying discharge plumes over traditional boat based methods and when combined with optical and oceanographic sensors provides a capability for both detecting plumes and assessing their mixing in both the near and far fields unique to this study is the optical sensing of of the presence of colored dissolved organic matter cdom in the discharge plume for quantitatively assessing the dilution ratio of the plume water this capability is demonstrated for two publicly operated treatment works potws located offshore san diego california that have significantly different environmental settings and operating parameters the first is the south bay ocean outfall sboo operated by the international boundary water commission ibwc whose discharge is located in approximately 30m deep water at a flow rate of 28 million gallons per day mgd the second discharge is the point loma ocean outfall ploo which discharges at approximately 90m with a nominal volume flow rate of 250 mgd the methodologies for planning the auv missions to sample the discharge plume characterizing the plume using the signals measured by the onboard oceanographic and optical sensors and use of those data in predictive models is outline the results suggest that even in variable oceanic conditions properly planned missions for auvs equipped with appropriate sensors can accurately characterize and track ocean outfall plumes with high spatial resolution more effectively than traditional methods

inversion of an oligocene volcano tectonic basin and uplifting of its superimposed miocene magmatic arc in the chilean central andes first seismic and gravity evidences abstract a new structural model is presented for the cenozoic part of the main range east of santiago a chain made up of thick miocene ignimbrites and andesitic lavas overlying primitive oligocene volcanoclastics deposited on a thin continental crust because the latter coya machali formation locally show tight folding close to the margins of the miocene volcanics they had previously been described as deformed prior to construction of the arc our field observations analysed along two profiles at 33 and 34 15 s however support the conclusion hinted at by ongoing geochronological and geochemical studies deformation of both formations is synchronous and related to late miocene inversion of the coya machali intra arc basin uplift of the rigid arc rocks and part of its volcanoclastic basement took place mainly along two northward shallowing boundary structures that seem to share a lower decollement the eastern fierro out of sequence thrust and a series of western back thrusts that resemble triangle zones seismic data obtained from el teniente porphyry copper mine 34 s rockbursts and two gravimetric profiles at the western end of the southern profile are compatible with a decollement located at that locality 2 3 km under the surface

tidal exchange at the bay ocean boundary for bays and inlets with narrow entrances tidal exchange with the ocean is often characterized by an ebb flood asymmetry in which the ebb flow exits the bay as a jet while the flood flow is drawn in approximately as a radial sink a process often termed tidal pumping in this paper the importance of tidal pumping in controlling the exchange of water at the bay ocean boundary is examined based on observations at the mouth of san diego bay the observations are novel in combining the use of shipboard acoustic doppler current measurements with a unique bay water tracer technique to provide visualization of the exchange as well as exchange budgets visualization of the tidal evolution of flow and tracers suggests that in accordance with the classical tidal pumping model the horizontal dynamics at the mouth of san diego bay are governed by an asymmetry between the jet like nature of the ebb flow and the sink like nature of the flood flow this asymmetry results in strong tidal velocity and phase gradients similar to those observed in previous numerical modeling studies a one dimensional trajectory model based on the observations indicates that the combined influence of the residual circulation and offshore gradients in the tidal velocity and phase provides the mechanism by which water from the bay is exchanged with water from the ocean both bottom friction and thermal gradients affect the dynamics of the vertical exchange the resulting asymmetry in the offshore flow leads to a vertical mode of pumping similar to that observed in the horizontal view this horizontal and vertical pumping of the offshore flow is shown to produce a strong correlation between the sectionally averaged velocity and bay water concentration resulting in a significant net tidal exchange between the bay and ocean

island wakes in shallow waters field laboratory and numerical results suggest that the free shear layer behind flow separation points and the internal circulation generated by rotation in the eddy are important processes in island wakes in shallow coastal waters

energy aspects of particle breakage in drained shear of sands the effect of particle breakage on the shear strength of sand is studied by considering the energy consumption due to particle breakage at the contacts between sand particles a stress dilatancy relationship for sand under a triaxial loading condition is developed adopting rowe s minimum energy ratio principle particle breakage and its relation to the shear strength of a sand can then be evaluated based on this relationship the increment of specific surface of the sand is used as an indication of the amount of particle breakage results of laboratory triaxial compression tests for fulung sand tamsui river sand and a decomposed granite are examined and compared with the stress dilatancy relationship the effect of particle breakage on the shear strength of a sand can be correlated with rate of energy consumption of particle breakage and rate of increment in particle surface area per unit volume of sand as proposed in this study the rate of energy consumption by particle breakage increases with increas

the island mass effect and biological carbon uptake for the subantarctic crozet archipelago marine productivity is often higher downstream than upstream of islands this so called island mass effect was tested and quantified with respect to biological carbon uptake and air sea exchange of carbon dioxide co2 at the crozet plateau between november 2004 and january 2005 during two crozex cruises the remote plateau is situated at 45 5 47 0 s 49 0 53 0 e south of the subantarctic front saf in the polar frontal zone pfz surface waters upstream south of the plateau had high nutrient and low chlorophyll hnlc concentrations the fugacity of carbon dioxide fco2 in surface water was just below the atmospheric value and oceanic co2 uptake was small 0 2 0 1 mol m 2 throughout crozex the mixed layer concentration of dissolved inorganic carbon dic decreased by 15 mol kg 1 from november to january in these hnlc waters indicating significant biological carbon uptake extensive phytoplankton blooms occurred downstream north of the plateau in austral spring these reduced surface water fco2 by 30 70 atm and dic by 30 60 mol kg 1 and created an important oceanic sink for atmospheric co2 of 0 6 0 8 0 4 mol m 2 corresponding to a total uptake of 1 3 0 8 tg c 1 tg 1012 g the reduction of dic in the upper 100 m was much larger downstream 2 3 mol m 2 than upstream 1 mol m 2 of the plateau in january further confirming the existence of the island mass effect for the crozet archipelago an additional finding is the sizeable dic deficit in the hnlc waters upstream south of the plateau suggesting that some hnlc waters of the pfz are more productive than commonly thought deep mixed layers of 60 90 m may hide such sustained modest marine productivity from detection by satellite

local and remote forcing of currents and temperature in the central southern california bight 1 a comprehensive study of the central southern california bight shows that subtidal currents are dominated by relatively long time scales 10 25 days large alongshore scales and significant offshore and upward phase propagation a one dimensional model shows that observed fluctuating poleward propagating speeds 140 260 cm s 1 alongshore pressure gradient disturbances account for a much larger fraction of the alongshore velocity variance than local wind stress at least 40 in both seasons and have the longer periods of the dominant currents with the addition of local wind stress about half the velocity variance can be accounted for and overall about 5 more variance in spring than in summer results are consistent with generation of disturbances by remote wind stress several hundred kilometers equatorward of the bight and alongcoast propagation as low mode coastally trapped waves the large scale remote forcing is also responsible for much of the velocity variance on the adjacent shelf the semienclosed santa monica bay a nonlinear three dimensional model shows that water is pushed into the bay initially as part of a throughflow later becoming an eddy that gradually fills the bay producing counterflow on its shoreward side on the shelf local alongshore wind stress accounts for only 25 of the velocity variance in spring and none in summer the large scale disturbances also produce significant temperature fluctuations throughout the region via lateral advection of the mean alongshore temperature gradient local wind driven coastal upwelling is responsible for temperature fluctuations on the inner shelf during several 2 4 day events in spring but only very near the coastal wall

the role of preexisting geologic architecture in the formation of giant porphyry related cu au deposits examples from new guinea and chile development of giant porphyry related copper and or gold deposits in new guinea and northern and central chile occurred during tertiary magmatic events that overprinted earlier extensional tectonic settings the earlier tectonic settings consisted of a mesozoic passive margin in new guinea a jurassic cretaceous back arc basin in northern chile and an oligocene intra arc basin in central chile the preexisting architecture of the basement rocks the fault systems and the stratigraphic packages associated with these settings played a strong role in controlling development of the giant deposits although the extensional tectonic settings in these terranes were different they share a number of elements that were used during formation of the tertiary ore deposits these were the presence of coupled systems of deeply detached listric synsedimentary faults and steep transverse faults and the presence of a relatively flat lying heterogeneous volcano sedimentary rock package during tertiary collision the deeply detached listric faults were inverted and strongly focused uplift exhumation and associated overpressuring induced failure and fluid flow in addition steep transverse faults were activated to form wrench systems with attendant steep deeply tapping pathways for magma and or fluid associated with dilatant jogs flexures or fault intersections ore deposits are commonly located in the hanging wall of the thrust faults under compression associated with collision the competent units of flat lying stratigraphic packages formed plates overlying the folded weaker units underneath and separated by a detachment or otherwise faulted contact examples of the competent upper units include the darai mendi limestone or equivalents in new guinea and the lavas of the farellones formation in central chile these plates appear to have impeded magma ascent and formed a cap on a magma and or fluid system pressurized by collision and orogenesis this geometry provided an ideal location for focusing of magmas and magmatic hydrothermal fluids from these three example terranes a set of exploration indicators have been constructed to highlight belts that are prospective for giant porphyry cu systems these indicators include 1 the presence of magmatic arcs that migrated into preexisting extensional architectures 2 coupled systems of deeply detached listric synsedimentary faults and steep transverse faults 3 rigid basement blocks that could form regional stress field perturbations and 4 fold belts with a major plate to 50 km wide of competent relatively undeformed or gently folded stratigraphy overlying more complexly folded and faulted parts of the sequence

petrogenetic and metallogenetic responses to miocene slab flattening new constraints from the el indio pascua au ag cu belt chile argentina the eocene miocene volcanic and hypabyssal rocks of the el indio pascua au ag cu belt in the southern central andean flat slab region are medium high k calc alkaline arc suites ranging in composition from andesite to rhyolite a significant transition in magmatic trace element chemistry coinciding with a pronounced reduction in magma output occurred in the late middle miocene as documented by 40ar 39ar geochronology the upper eocene lower middle miocene rocks exhibit low sr y ratios 50 minor heavy ree fractionation with sm yb ratios not exceeding 3 5 and in some cases minor negative eu anomalies in contrast the largely dacitic rocks erupted after ca 13 ma are depleted in y 10 ppm have generally high but variable sr y ratios 30 200 exhibit moderate middle and heavy ree fractionation sm yb 3 7 5 9 and lack negative eu anomalies the latter features are characteristic of adakitic suites i e slab melts but the regional temporal and spatial distribution of arc magmatism precludes a major magma source in the downgoing slab this evolution is interpreted as reflecting a progressive increase in pressure and the availability of water in the lower crustal site of magma generation establishing both garnet and hornblende as major stable phases in the residuum the pressure in the lower crust increased in response to episodic crustal thickening related to the shallowing of the slab a process recorded by the incision of three regional pediplains over the period 17 6 ma elimination of the subarc asthenospheric mantle and much of the lithospheric mantle by ca 10 ma permitted direct incursion of slab derived highly oxidised metal and volatile rich supercritical fluids into the lower crust stimulating melting of mafic garnet amphibolitic and eclogitic assemblages

the donoso copper rich tourmaline bearing breccia pipe in central chile petrologic fluid inclusion and stable isotope evidence for an origin from magmatic fluids the copper rich tourmaline bearing donoso breccia pipe is one among more than 15 different mineralized breccias in the giant 50 million metric tonnes of copper miocene and pliocene rio blanco los bronces copper deposit in the high andes of central chile this breccia pipe bracketed in age between 5 2 and 4 9 ma has dimensions of 500 by 700 m at the current surface 3 670 m above sea level its roots have yet to be encountered and it is 300 m in diameter at the depth of the deepest drill holes the donoso breccia is for the most part monolithic containing clasts of the equigranular quartz monzonite pluton which hosts the pipe it is matrix supported with between 5 and 25 of the total rock volume consisting of breccia matrix minerals which include tourmaline quartz chalcopyrite pyrite specularite and lesser amounts of bornite and anhydrite an open pit mine centered on this breccia pipe has a current production of 50 000 tonnes of ore per day at an average grade of 1 2 copper and copper grade in the breccia matrix is significantly higher measured 18o for tourmaline and quartz from the matrix of the donoso breccia at different levels of the pipe range from 6 9 to 12 0 and measured d in tourmaline ranges from 73 to 95 temperatures of crystallization of these minerals as determined by the highest homogenization temperatures of highly saline fluid inclusions range from 400 to 690 c when corrected for these temperatures the stable isotope data indicate that fluids from which these breccia matrix minerals precipitated were magmatic with 18o between 5 6 to 9 1 and d between 51 to 80 these isotopic data preclude participation of a significant amount of meteoric water in the formation of the donoso breccia they support a model in which brecciation is caused by expansion of magmatic fluids exsolved from a cooling pluton and breccia matrix minerals including copper sulfides precipitated from the same magmatic fluids responsible for brecciation sericitic alteration of clasts in the breccia was also caused by these magmatic fluids different types of fluid inclusions imply that several different magmatic fluids were involved in formation of the donoso breccia these include high temperature highly saline non boiling fluids trapped in inclusions that homogenize by halite dissolution which probably exsolved from a magma cooling under relatively high 1 kbar lithostatic pressure conditions consistent with geologic constraints other high temperature highly saline fluids are trapped in inclusions that homogenize by vapor bubble disappearance and are spatially associated with vapor rich inclusions suggesting either phase separation boiling or simultaneous separation of immiscible brine and vapor from a magma cooling at lower hydrostatic pressure conditions both types of high temperature highly saline fluids circulated intermittently as pressure fluctuated between lithostatic and hydrostatic conditions because of episodes of sealing and rebrecciation

island wakes in shallow coastal waters rattray island northeast australia is 1 5 km long 300 m wide and lies in well mixed water approximately 25 m deep its long axis is inclined at about 60 into the direction of the dominant semidiurnal tidal current the length of the wake in the lee of the island as documented by aerial photographs and satellite imagery appears to equal that of the wake behind a flat plate in a two dimensional flow at a reynolds number of about 10 however current metering drogues measurements and temperature mapping indicate internal wake velocities much greater than would be consistent with such a simple low reynolds number model further estimates of the turbulent eddy coefficient suggest an effective reynolds number more in the vicinity of 103 to reconcile these observational differences and to explain the observed upwelling in the core of the wake an ekman pumping model is proposed it is postulated that the ekman benthic boundary layer driven by rotation in the wake allows the vertical vorticity introduced into the water at the tip of the island at the point of separation to be negated by the vorticity of opposite sign introduced at the bottom further it is shown that a large fraction of the kinetic energy of the upstream flow facing the island is used to drive the wake eddies leading to the conclusions that the trapping of water in the lee of islands greatly increases head losses on continental shelves with numerous islands coral reefs and rock outcrops

effect of soil contraction tendency on static liquefaction triggering analysis static liquefaction failure occurs when the shear stress applied by a monotonic triggering load exceeds the undrained yield peak shear strength of the saturated liquefiable cohesionless soil in this study the effect of soil contraction tendency on static liquefaction failure of cohesionless soils is characterised by an empirical relationship between soil brittleness index and undrained yield strength from a database of 702 laboratory shear tests performed by the author and collected from past literature the application of this relationship for estimating the static liquefaction triggering strength of cohesionless soils is validated by comparison with several cases of liquefaction failures

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

formation and circulation of dense water in the persian arabian gulf 1 the nature and circulation of water masses in the persian arabian gulf hereinafter referred to as the gulf is investigated by examination of a historic database of hydrographic observations the densest water forms in winter at the northern end of the gulf rather than along the warmer southern and western coasts with the exception of small amounts of water directly above the seafloor most water flowing out of the gulf mixes across a density front that separates gulf deep water within the gulf from the indian ocean surface water iosw contrary to previous inferences the seasonally variable incursion of iosw into the gulf peaks in late spring this timing may be due to seasonal changes in sea surface slope driven by variations in evaporation rate in order to explain mooring results published elsewhere that show relatively small seasonal changes in the volume flux through the strait of hormuz hereinafter referred to as the strait we suggest that this flux is driven by the difference between the density of gulf deep water in the interior of the basin and water at comparable depths outside the gulf this density difference varies less than 15 during the year high rates of vertical mixing in the strait extend about 200 km westward in response to topographic constriction of tidal flows by islands and shoals