structure of the upper ocean in the western equatorial pacific the western equatorial pacific has an important role in the el nino southern oscillation climate cycle1 2 and sea surface temperature anomalies in this area are known to affect the global atmospheric circulation3 little is known however about the factors that control the response of the upper ocean and hence sea surface temperature to changes in atmospheric conditions here we present observations of the density and current structure of the upper layers of the western equatorial pacific ocean we observed frontal features with temperature differences of 1 c extending from the surface down to a depth of 150 m a strong salinity front associated with a surface convergence and interleaving of high and low salinity waters in 10 m thick layers that extended for several hundred kilometres in the north south direction the large spatial and temporal variability in temperature and salinity observed must influence heat transport and hence the ocean response to atmospheric forcing in particular the response to westerly wind bursts which are thought to be precursors to an el nino we estimate the horizontal diffusion coefficient of the interleaving which indicates that the observed layering may con tribute to horizontal mixing within the thermocline

late eocene to early miocene ice sheet dynamics and the global carbon cycle paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial pacific ocean drilling program site 1218 the records include the two largest abrupt 1 myr increases in the cenozoic benthic oxygen isotope record oi 1 in the earliest oligocene 34 ma and mi 1 in the earliest miocene 23 ma the paired mg ca and oxygen isotope records are used to calculate seawater 18o w calculated w suggests that a large antarctic ice sheet formed during oi 1 and subsequently fluctuated throughout the oligocene on both short 0 5 myr and long 2 3 myr timescales between about 50 and 100 of its maximum earliest oligocene size the magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy the transient expansion of the antarctic ice sheet at mi 1 is marked in the benthic 18o record by two positive excursions between 23 7 and 22 9 ma each with a duration of 200 300 kyr bottom water temperatures decreased by 2 c over the 150 kyr immediately prior to both rapid 18o excursions however the onset of each of these phases of ice growth is synchronous within the resolution of the records with the onset of a 2 c warming over 150 kyr we suggest that the warming during these glacial expansions reflect increased greenhouse forcing prompted by a sudden decrease in global chemical weathering rates as antarctic basement silicate rocks became blanketed by an ice sheet this represents a negative feedback process that might have operated during major abrupt growth phases of the antarctic ice sheet

scaling wind stirring effects in an oceanic bulk mixed layer model with application to an ogcm of the tropical pacific the mixed layer depth mld plays an important role in the climate system through its influences on sea surface temperature sst the kraus turner niiler hereafter referred to as ktn bulk mixed layer ml model is designed for describing the mld and has been adopted widely by many ocean modeling however large biases exist in the mld simulation using the original ktn model in the tropical pacific this is partly due to the uncertainties in representing wind stirring effect in the model which is scaled by a parameter m 0 traditionally m 0 is taken as a constant uniformly in space in this study the m 0 is estimated as spatially and seasonally varying through its inverse calculation from a balance equation describing the turbulent kinetic energy tke budget of the ml it is illustrated that the m 0 is spatially varying over the tropical pacific the derived m 0 fields are then embedded into an ocean general circulation model ogcm compared with the observations and the global ocean data assimilation system godas analyses the mld simulations in the ogcm with varying m 0 are substantially improved in the tropical pacific ocean on seasonal and interannual time scales additionally the pacific subtropical cells stcs become intensified accompanied with the strengthening of upwelling in the eastern equatorial pacific thus more realistic simulations are obtained in spatially and seasonally varying m 0 case compared with the constant m 0 case as the related cooling effect from the upwelling is enhanced the simulated sst is slightly cooled down in the eastern equatorial pacific further applications and implications are also discussed

a method for evaluating the stability of an unsaturated slope in natural terrain during rainfall abstract the stability of an unsaturated slope in natural terrain was evaluated based on the variation in the suction stress in the soil layer induced by rainfall a field monitoring site where landslides have occurred in the past was selected as the study area to apply the concept of slope stability analysis considering the suction stress in unsaturated soil the soil water characteristic curve swcc and the suction stress characteristic curve sscc of the unsaturated soil obtained from the study area were estimated using the van genuchten 1980 model and the lu and likos 2006 model respectively the phenomenon of ground saturation induced by the infiltration of rainfall into unsaturated soil is similar to the wetting path of the swcc the curve fit parameters estimated from the swcc wetting path were therefore used to determine the matric suction and suction stress in the unsaturated soil the amount of rainfall and the volumetric water content of the soil were measured using a rain gauge and time domain reflectometer tdr sensors respectively at the monitoring site an infinite slope was chosen as representative of the slope of the natural terrain in the study area because the slope length is very long but the depth of the soil layer over the rock is very shallow the stability of this unsaturated slope in natural terrain was evaluated based on the safety factor of an infinite slope considering the suction stress in the unsaturated soil layer the safety factor of the slope suddenly decreased during and just after a rainfall and then recovered notably the safety factor of this natural slope exhibited continuous fluctuations because of changes in the suction stress caused by the evaporation and infiltration of water in the unsaturated soil layer the variation in the suction stress in unsaturated soil induced by rainfall can be estimated from the results of laboratory tests performed to estimate the wetting process based on the swcc and sscc in combination with field monitoring data collected by sensors to measure the volumetric water content or matric suction in the soil therefore the infinite slope stability of a slope in natural terrain can be evaluated in real time by estimating the suction stress in the unsaturated soil due to rainfall when the volumetric water content or matric suction in the soil is being monitored in the field

model test study on the hydrological mechanisms and early warning thresholds for loess fill slope failure induced by rainfall abstract under rainfall conditions the characteristics of hydraulic changes related to the failure evolution of fill slopes are critical to the early warning of slope failure in this study a series of model tests are carried out on loess fill slopes with different slope types the matric suction volumetric moisture content pore water pressure and deformation of the slope are monitored in real time during the rainfall process meanwhile the development of cracks and the failure modes of the slope are analyzed and then the early warning strategy of fill slope failure induced by rainfall is studied the results show that loess landslides induced by rainfall exhibit a hysteresis however the volumetric water content and the matrix suction respond earlier than the pore water pressure the slope failure is produced when the volumetric water content and the matrix suction are respectively at their maximum and minimum values the evolution mechanism of cracks on the slope starts when tensile cracks are first generated near the leading edge surface and then extend backwards in the next stage shear fracture is produced near the flanking of the slope and finally the trailing edge produces a transfixion tensile crack from the top to toe of the fill slope which not only provides the advantage of an infiltration channel to control the hydrological process but also evolves into the trailing edge boundary of each failure of fill slope with the increase of rainfall duration the filling slope presents different failure characteristics revealing the hydraulic behavior of a partially saturated slope in addition combined with the infinite slope stability analysis in mohr coulomb soil the matrix suction and volumetric water content thresholds of the fill slopes with different slope angle are determined the early warning threshold model for rainfall induced slope instability is proposed and a new framework of early warning is provided

unsaturated hydro mechanical behaviour of rainfall induced mass remobilization in post earthquake landslides abstract clarifying the hydro mechanical characteristics of the mechanism associated with mass remobilization is a major step towards landslide early warning but this clarification is usually hampered by a lack of in situ evidence in this study shallow rainfall triggered slope failures under partially saturated conditions were documented by combining instrumental evidence from field experiments on a natural co seismic landslide and hydro mechanical slope stability analysis in an earthquake affected region the results revealed the transient processes and unsaturated conditions associated with mass movement in response to rainfall and preferential flow paths were found to dominate the hydrological processes during rainfall infiltration in the landslide deposit the results also demonstrated the importance of certain hydrological parameters including soil matric suction and moisture content in landslide early warning this study reveals a partially saturated hydro mechanical behaviour to predict the initiation of rainfall induced landslides during post earthquake disaster relief

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

effect of planetary rotation on oceanic surface boundary layer turbulence abstracta large eddy simulation les model is configured to investigate the effect of the horizontal northward component of earth s rotation on upper ocean turbulence the focus is on the variab

steep slope monitoring in unsaturated pyroclastic soils based on monitoring results the paper describes the hydrological response of a steep hillslope covered by unsaturated pyroclastic soils the instrumented site is located just beside an area which experienced a catastrophic flowslide two years prior to the survey monitoring involved rainfall and matric suction measured at different locations and depths investigations focused on the hydrological response of the slope so as to model the effects of rainfall and then predict the onset of slope failure triggered by critical rainfall

transient deterministic shallow landslide modeling requirements for susceptibility and hazard assessments in a gis framework abstract application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall topography and the distribution and properties of hillside materials we survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore pressure response to rainfall infiltration with an infinite slope stability calculation pore pressures and factors of safety are computed on a cell by cell basis and can be displayed or manipulated in a grid based gis input data are high resolution 1 8 m topographic information derived from lidar data and simple descriptions of initial pore pressure distribution and boundary conditions for a study area north of seattle washington rainfall information is taken from a previously defined empirical rainfall intensity duration threshold and material strength and hydraulic properties were measured both in the field and laboratory results are tested by comparison with a shallow landslide inventory comparison of results with those from static infinite slope stability analyses assuming fixed water table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses moreover results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area

boundary effect on the hydraulic characteristics of gravelly soil slopes in physical model tests abstract the stability of a residual gravelly soil slope during heavy rainfall is closely related to the seepage field which is directly affected by the seepage boundaries of the slope to examine the boundary effect a novel model flume that can implement permeable and impermeable boundary conditions was designed with this flume hydraulic model tests of a gravelly soil slope considering those two seepage boundaries were carried out the results show that distinct spatial morphology of seepage fields is reflected by the hydraulic characteristics of the slope models with different seepage boundaries the slope with permeable boundaries generally exhibits a larger average infiltration rate as well as a relatively smaller moving speed of wetting front in the lower part compared to the slope with impermeable boundaries the residual moisture content in the deep lower part of the slope with permeable boundaries is 6 6 cm3 cm3 smaller than that of the slope with impermeable boundaries nevertheless the maximum pore water pressure in the middle part of the slope with permeable boundaries is 1 2 kpa higher than that in the corresponding part of the slope with impermeable boundaries it is noted that regional pore water pressures in the shallow lower and shallow middle parts of the slope with impermeable boundaries exhibit large fluctuations with an amplitude over 0 5 kpa the seepage field in the slope with permeable boundaries presents a multi dimensional development which may lead to a local failure of the slope the results are of great significance in studying the similarity of seepage boundary condition in the field of similarity theory on landslide model tests and provide an experimental basis for establishing rainfall induced landslide theory

flume tests to study the initiation of huge debris flows after the wenchuan earthquake in s w china abstract in the wenchuan area in the southwest of china a huge amount of loose co seismic landslide material was deposited on slopes during the wenchuan earthquake of may 2008 these loose deposits formed the source material for rainfall induced debris flows or shallow landslides in the years after the earthquake on august 13 2010 about 20 large debris flows were triggered by heavy rainfall in the area around the epicenter of the wenchuan earthquake field reconnaissance revealed that the initiation of these post earthquake debris flows was closely related to severe erosion of the loose deposits flume tests were carried out to study the initiation mechanism of these post earthquake debris flows and the related influencing factors the flume was instrumented with ten combination sets of suction and pore pressure sensors these sensors were accompanied by tdr probes to measure the soil water content the flume has a length of 2 5 m and a width of 1 5 m a series of 26 tests was conducted to study the influence of slope gradient and discharge on the initiation mechanism and scale of the debris flows the amount of debris flow discharge was obtained by collecting the washed out deposits every 20 s the experimental results showed that the initiation mechanism of debris flows for gentle slopes and steep slopes was different on steeper slope incision by run off water was very rapid initiating directly the start of a debris flow the debris flow volume increased rapidly by a chain of subsequent cascading processes starting with collapses of the side walls damming and breaching leading to a rapid widening of the erosion channel at gentler slopes less intensive run off incision caused an accumulation of material down slope which after saturation failed as shallow slides transform in a second stage into debris flows it was demonstrated that the slope was the dominant factor in controlling the scale of the debris flows while the effect of discharge on erosion and the size of the debris flows was less clear

spatial variation of saturated hydraulic conductivity of a loess slope in the south jingyang plateau china abstract water infiltration in loess soils is an important trigger causing landslides in which the hydraulic conductivity of the loess plays an important role by analyzing a soil trench and soil samples from the south jingyang plateau northwest china a loess slope was investigated a horizontal adit in a lishi loess layer was also analyzed using variable head permeability tests the saturated horizontal hydraulic conductivity k h and saturated vertical hydraulic conductivity k v of the loess samples were measured results showed that the majority of the k h values are larger than the k v values indicating that the loess exhibits permeability anisotropy lilliefors test was used to determine the normality of the k h and k v results test results indicate that k h and k v measurements of the loess samples collected in the trench and adit all show log normal distribution while a number of the k h and k v values also reflect a normal distribution geo statistical analysis shows that the spherical model and the gaussian model provide the best fit variograms of k h and k v values along the trench analysis along the adit indicated the opposite results the variogram range values suggest that the spatial correlation of loess k v is greater in the vertical direction in a horizontal plane while the spatial correlation of k h in the adit is greater than that in the vertical direction loess structure rather than randomness decides the spatial variation of k h and k v measurements except for k h variation along the adit which depends on both structural factor and randomness k h and k v values of loess tend to decrease with depth results which can be described by an exponential decay model

unsaturated soil mechanics in rainfall induced flow landslides abstract rainfall induced flow landslides in coarse grained soils pose significant threats to populations and structures due to their high velocities long travel distance and the absence of definite warning signs during the pre failure stage the triggering phase of these phenomena is frequently related to rainfall events which significantly reduce matric suction in the shallower soil layers in this paper the processes leading to the onset of such phenomena are illustrated and some observations on their modelling are briefly recalled the failure stage at different scales is then modelled with reference to a case study from southern italy which draws on high quality experimental data sets from extensive in situ and laboratory investigation

the mechanisms behind shallow failures in slopes comprised of landslide deposits in areas hit by the 2008 wenchuan earthquake that occurred in sichuan province china debris flows are often generated from landslide deposits during heavy rainstorms the broadly graded and unconsolidated landslide deposits respond to rainfall in very complex mechanical and hydraulic manners an artificial rainfall test was conducted to simulate the rainfall infiltration and surface runoff processes occurring on the landslide deposit slope at the wenjiagou gully china with heavy rainfall rates 140 mm h incorporated an innovative flume was designed to collect the slope interflow and surface runoff separately sensors to monitor the pore water content pwp and volumetric water content vwc were deployed the results indicated that there were four stages in the hydrological response of landslide deposits during the artificial rain event infiltration a slow increase in interflow surface runoff begins a rapid increase in interflow surface runoff slowly increases and a steady state bed gradient increase will lead to pwp rapidly ascending and regressive failure happening concomitant with the observed increases in pwp and vwc the shear strength of the landslide deposits decreased and led to the occurrence of small scale shallow failures surface runoff interflow and fine particle migration effects are presented to interpret the process of shallow failure and although shallow slope failure is the result of interaction with the above three factors induced by rainfall the key underlying factor is the characteristically loose structure of landslide deposits c 2014 elsevier b v all rights reserved

wind direction and equilibrium mixed layer depth in the tropical pacific ocean abstract the normal equilibrium state of the tropical pacific mixed layer is explained by the steady state solution for the maximum vertical penetration of oceanic turbulence generated by local atmospheric forcing the previously overlooked interaction between planetary rotation and the zonal wind stress is believed to increase the vertical turbulent kinetic energy causing the deep mixed layer in the central and western equatorial pacific ocean the unique conditions of the tropical pacific provide a test for a revision to the basic equilibrium theory for turbulent mixing in stable oceanic planetary boundary layers

hydrological factors affecting rainfall induced shallow landslides from the field monitoring to a simplified slope stability analysis abstract rainfall induced shallow landslides can seriously affect cultivations and infrastructures and cause human losses a continuous monitoring of unsaturated soil hydrological properties is needed to understand the effects of pore water pressure and water content on shallow landslides triggering and slope safety factor in this work the impact of water content pore water pressure and hydrological hysteresis on safety factor reconstruction is analyzed by applying two different models lu and godt s and slip models to a monitored slope located in oltrepo pavese northern italy a shallow landslide event in the studied slope during the monitoring allowed for identifying the triggering mechanism and modeling the safety factor changes the conditions of instability mechanism develop in periods with frequent rainfalls the uprising of a perched water table in the soil profile gets nil or positive pore water pressure which linked with the nil effective soil cohesion of some soil horizons allows for the shallow landslide triggering the safety factor trends correctly predicted unstable conditions safety factor 1 0 in correspondence of the shallow landslide triggering time on the basis of both water content and pore water pressure a better prediction gets when the safety factor is modeled considering the hysteresis effects modeling the safety factor on the basis of water content can make a good assessment of shallow failures triggering conditions only for failures in unsaturated soils and for completely saturated soils instead considering pore water pressure it is possible estimating safety factor changes linked with the development of positive pore water pressures which can be linked in some cases to shallow landslide development

estimating the timing and location of shallow rainfall induced landslides using a model for transient unsaturated infiltration 1 shallow rainfall induced landslides commonly occur under conditions of transient infiltration into initially unsaturated soils in an effort to predict the timing and location of such landslides we developed a model of the infiltration process using a two layer system that consists of an unsaturated zone above a saturated zone and implemented this model in a geographic information system gis framework the model links analytical solutions for transient unsaturated vertical infiltration above the water table to pressure diffusion solutions for pressure changes below the water table the solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone this scheme though limited to simplified soil water characteristics and moist initial conditions greatly improves computational efficiency over numerical models in spatially distributed modeling applications pore pressures computed by these coupled models are subsequently used in one dimensional slope stability computations to estimate the timing and locations of slope failures applied over a digital landscape near seattle washington for an hourly rainfall history known to trigger shallow landslides the model computes a factor of safety for each grid cell at any time during a rainstorm the unsaturated layer attenuates and delays the rainfall induced pore pressure response of the model at depth consistent with observations at an instrumented hillside near edmonds washington this attenuation results in realistic estimates of timing for the onset of slope instability 7 h earlier than observed landslides on average by considering the spatial distribution of physical properties the model predicts the primary source areas of landslides

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

insights from the talysh of azerbaijan into the paleogene evolution of the south caspian region the age and mode of formation of the south caspian basin are disputed an 10 km thick predominantly middle eocene clastic and volcanic succession is exposed in the talysh mountains of azerbaijan at its western margin here high k alkali basalts pass laterally to the east and southeast into volcanogenic sandstone dominated turbidity current and debris flow deposits these southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western south caspian basin new ar ar ages cluster around 39 ma with an upper 1400 m thick volcanic interval being deposited in 2 2 0 2 m y we interpret that this rapid deposition and magmatism records a major back arc extensional transtensional event in the talysh north of the north dipping neotethyan subduction zone this event is recognized across much of southwest asia and may indicate a period of significant basin formation within the adjacent south caspian basin a transition into upper eocene lower oligocene strata dominated by fine grained turbidity current and hemipelagic sediments with slope instability features is interpreted to mark the end of rifting and volcanism in the talysh and the start of the arabia eurasia collision overlying oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the talysh region