sea level budget in the bay of bengal 2002 2014 from grace and altimetry sea level rise is perceived as a major threat to the densely populated coast of the bay of bengal addressing future rise requires understanding the present day sea level budget using a novel method and data from the gravity recovery and climate experiment grace satellite we partition altimetric sea level rise 6 1 mm a over 2002 2014 into mass and steric components we find that current mass trends in the bay of bengal are slightly above global mean while steric trends appear much larger 2 2 3 1 mm a if we disregard a residual required to close the budget and 4 3 4 6 mm a if as an upper bound we attribute this residual entirely to steric expansion our method differs from published approaches in that it explains altimetry and grace data in a least squares inversion while mass anomalies are parameterized through gravitationally self consistent fingerprints and steric expansion through eofs we validate our estimates by comparing to argo and modeling for the indian ocean and by comparing total water storage change twsc for the ganges and brahmaputra basins to the conventional grace approach we find good agreement for twsc and reasonable agreement for steric heights depending on the ocean region and argo product we ascribe differences to weaknesses of the argo data but we also find the inversion to be to some extent sensitive with respect to the eofs finally combining our estimates with cmip5 simulations we estimate that bay of bengal absolute sea level may rise for additional 37 cm under the rcp4 5 scenario and 40 cm under rcp8 5 until 2050 with respect to 2005

low frequency currents from deep moorings in the southern bay of bengal abstracthigh resolution currents and hydrographic fields were measured at six deep water moorings in the southern bay of bengal bob by the naval research laboratory as part of an international effort focused on the dynamics of the indian ocean currents temperature and salinity were sampled over the upper 500 m for 20 months between december 2013 and august 2015 one of the major goals is to understand the space time scales of the currents and physical processes that contribute to the exchange of water between the bob and the arabian sea the observations captured southwest and northeast monsoon currents seasonally varying large eddies including a cyclonic eddy the sri lanka dome sld and an anticyclonic eddy southeast of the sld the observations further showed intraseasonal oscillations with periods of 30 70 days near inertial currents and tides monthly averaged velocities commonly exceeded 50 cm s 1 near the surface and extreme velocities exceeded 150 cm s 1 during the southwest monsoon ti

observations of energetic high wavenumber internal waves in the kuroshio abstract intense and spatially coherent shear layers were detected in and under the kuroshio in an april 2000 survey in the east china sea the sloping layers revealed by shipboard doppler sonars on the r v roger revelle appeared to cross isopycnal surfaces except in a small region near the kuroshio shelfbreak front the rms finescale shear associated with the layers significantly exceeded the geostrophic shear an april 2002 follow on cruise was organized to establish whether these motions were propagating internal waves shipboard and lowered adcps were both operated from the r v melville in addition to ctd sonar transects a 30 h time series of currents and shear was obtained in the core of the kuroshio near the island of kyushu japan the shear structures were indeed found to be propagating with both up and down going internal wave motions present in comparison with the nearby open ocean the finescale 160 m vertical shear variance is increased by a factor of 3 in the kuroshio and by a fact

satellite observations of a western boundary current in the bay of bengal satellite infrared observations of the bay of bengal during the latter part of february 1985 reveal the existence of two bands of warm water that resemble western boundary currents along the east coasts of india and sri lanka a recently formed elliptical warm core eddy with a major axis of nearly 150 km appears at longitude 90 e and latitude 19 n at the end of the axis of the current color infrared images of sea surface temperature are used to illustrate the sea surface temperature patterns and to estimate their displacements with time

statistics of microstructure patchiness in a stratified lake 1 statistics of microstructure patches in a sheared strongly stratified metalimnion of lake banyoles catalonia spain which occupied 40 of the total lake depth of 12 m are analyzed light winds 0 25 m the ratio ltp hp depends on the patch richardson and mixing reynolds numbers following the parameterization of lozovatsky and fernando 2002 analysis of the dynamics of mixing reveals that averaged vertical diffusivities ranged between 1 10 4 m2 s 1 and 5 10 5 m2 s 1 depending on the phase of the internal waves episodic wind gusts wind speed above 6 m s 1 transfer 1 6 of the wind energy to the metalimnion and 0 7 to the hypolimnion generating large microstructure patches with hp of several meters

meteorological and internal wave forcing of seiches along the sri lanka coast regularly observed seiches from tide gauge records around the sri lanka coast have been analysed to determine the forcing mechanisms the seiche periods range from a few tens of minutes to 2 hr fortnightly and seasonal variations of seiche amplitudes are clearly visible on the east coast these seiche amplitudes are particularly large approximately 6 8 days after spring tides with maximum seiche amplitudes observed during march april and october november suggesting that the seiche variation could be related to stratification and internal wave activity there is no visible fortnightly and seasonal variation of seiche amplitudes in west coast records instead they show a daily pattern with relatively larger seiches around 10 00 hrs local time suggesting that the seiches on the west coast could result from diurnal atmospheric forcing barotropic and 2 layer models have been developed to investigate the influence of atmospheric forcing and internal wave activity on the seiches a barotropic model applied to the west coast shows that the daily seiche amplitude variation could be simulated with cyclic diurnal meteorological forcing two layer model runs for trincomalee bay and the adjacent east coast shelf suggest that seiche amplitudes are proportional to vertical stratification and mixed layer depths therefore the observed seiches there could be excited by internal waves which originate as far away as the andaman sea during spring tides and have a travel time of 6 8 days to the sri lankan east coast however further studies including direct measurements of internal wave activity within the region are required to confirm this hypothesis

how unusual is the long runout of the earthquake triggered giant luanshibao landslide tibetan plateau china abstract in the tibetan plateau active tectonic deformation triggers frequent earthquakes and giant landslides associated with active faults produce serious consequences a study of the characteristics and mechanism of a historical long runout landslide in luanshibao lsb tibetan plateau china finds a maximum sliding distance l of 3 83 km with an elevation drop h of 820 m the landslide volume v was 0 64 0 94 10 8 m 3 and it produced a long runout h l 0 21 recent surface offset along the sinistral strike slip litang dewu fault passes through the middle part of the landslide which initiated on the hanging wall of the fault geological mapping geophysical prospecting trenching and 14 c dating together indicate that the lsb landslide occurred in jointed granite ca 1980 30 ybp probably triggered by a large earthquake compilation of volume and runout distance data for this landslide and other previously published data for volcanic and nonvolcanic long runout landslides yields a composite runout length volume relation l 12 52 v 0 37 that closely predicts runout of the lsb landslide although substantial variation is noted in runout length around the central tendency

freshwater export pathways from the bay of bengal abstract observations from surface drifters and argo floats elucidate details of two upper ocean pathways through which freshwater from the bay of bengal bob is advected into the tropical indian ocean and arabian sea as the western route is located along the east coast of india and feeds into the westward northeast monsoon current nmc south of sri lanka during the winter monsoon whereas the eastern path is located along the western margin of sumatra reaching at times as far south as the indonesian throughflow plume near 10 s while the former pathway is highly seasonal and affected by mesoscale variability the latter is a year round feature and may be dominant from an annual perspective the observations do not support the notion of a continuous current system comprised of the nmc and the west india coastal current around the laccadive high in boreal winter that can directly export surface freshwater from the bob to the as further the observations indicate an occasional leakage of low salinity water by a westward coastal current between the eastward southwest monsoon current smc and sri lanka in boreal summer that may be caused by equatorial wave processes the smc which exhibits considerable ekman contributions in contrast to its geostrophically balanced nmc counterpart in boreal winter facilitates the transport of saltier as water into the bob with subsequent spreading into the upper thermocline of the bob setting up an estuary like circulation pattern

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

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

spatial and temporal occurrence of rainfall induced shallow landslides of flow type a case of sarno quindici italy article i nfo rainfall induced shallow landslides of flow type provide unstable masses which often travel long run out distances with high velocities thus posing a high societal risk when they affect large areas therefore analysis of their spatial and temporal occurrence is relevant to landslide hazard assessment as the first step of the risk analysis in order to address this issue this paper outlines a multidisciplinary procedure that is applied to the may 1998 sarno quindici landslides southern italy whose spatial and temporal occurrence is not satisfactorily addressed in current literature the spatial occurrence of the landslides is analysed using heuristic models for both the source and propagation areas the temporal occurrence of the landslides is firstly compiled and then related to the cumulated rainfall stratigraphy and hydraulic boundary conditions finally the spatial and temporal occurrence of the main landslide triggering mechanism is modelled over the whole affected area by analysing the groundwater regime and slope stability conditions the obtained results show that the spatial and temporal occurrence is strongly related to stratigraphy and hydraulic boundary conditions at both the slope and massif scales they also highlight a suitable procedure for assessing the spatial and temporal occurrence of complex landslides over large areas

investigation of the generation and propagation of low frequency internal waves a case study for the east coast of india sar synthetic aperture radar images in the northwest bay of bengal indicate the existence of internal waves and their occurrence and intensity is topography dependent as indicated by in situ data and satellite information to complement and comprehend the observations a three dimensional princeton ocean model is applied to study the generation and propagation of internal waves the model domain is configured with a variable curvilinear grid and the input fields comprise bathymetry initial temperature and salinity wind stress air sea heat flux and tidal information the numerical investigation indicated a predominant activity of internal waves in the north and the rationale is three fold the first one could be the stable stratification due to fresh water discharge from head bay major river system secondly the significant magnitude range of the tides and finally the bathymetry in the coastal waters off paradip is about 12 shallower compared to that of visakhapatnam and further south the cumulative effect of these causes the predominance of internal waves in the north the core of the energy is essentially in the low frequency range and the model is able to simulate semi diurnal and diurnal components reasonably well up to 6 h frequency 0 162 cph

shear strain and richardson number variations in the thermocline part i statistical description abstract quasi continuous depth time observations of shear 5 5 m 6 min resolution and strain z 2 m 2 1 min resolution obtained from the r p flip are applied to a study of richardson number ri statistics data were collected off the coast of central california in the 1990 surface waves processes experiment observations are presented in eulerian and in isopycnal following frames in both frames shear variance is found to scale as n2 in the thermocline in agreement with previous findings of gargett et al the probability density function for squared shear magnitude is very nearly exponential strain variance is approximately uniform with depth the magnitude of the fluctuations is sufficient to influence the ri field significantly at finescale to model the richardson number the detailed interrelationship between shear and strain must be specified two contrasting hypotheses are considered one h i holds that fluctuations in the cross isopycnal shear are independent of isopycnal separat

behaviour of recompacted residual soils in a constant shear stress path the significance of studying soil behaviour in a constant shear stress path to understand rain induced slope failures and debris flows has long been recognized studies with constant shear tests have however been limited and some past results from undisturbed soils appear to show stress path dependent volume change behaviour the present study systematically investigates the behaviour of recompacted residual soils in a constant shear stress path using a comprehensive experimental program it is shown that the results of this test program and previously published data can be interpreted using the concepts of critical state soil mechanics

monitoring the process of ground failure in repeated landslides and associated stability assessments abstract field monitoring of two repeated landslide areas namely the sodechi and the yonaihata landslide areas on the island of honshu japan has revealed that the spread of ground failure occurred as in normal landslide even though these landslide events were repeated slides in clayey material a rapid increase in surface displacement the beginning of third stage creep occurred simultaneously with an increase in strain in the ground the cause of local failure along the sliding surface resulting in large continuous landslide movements thus an entire slope began to collapse when the full length of the failure surface became connected ring shear tests of landslide clay were conducted to determine three kinds of shear strength parameters 1 fully softened strength parameter parameter for peak strength of remolded clay 2 specimen separated strength parameter ss newly proposed in this study and 3 residual strength parameter r stability analysis revealed that ss was the most appropriate shear strength parameter to express slope stability in the ground failure transmission stage thus this result provides a first step in applying the mechanism of ground failure transmission to the problem of slope stability by defining the specimen separated strength parameter ss

δ 18 o and salinity variability from the last glacial maximum to recent in the bay of bengal and andaman sea abstract oxygen isotopes of surface thermocline and bottom dwelling foraminifera were analysed from two well dated andaman sea cores and combined with nine previously published records from the bay of bengal bob and andaman sea to create a transect spanning 20 n to 5 n combined with temperature estimates and the observed seawater 18 o salinity relationship these data are used to estimate past changes in bob salinity structure compared to modern mid holocene 9 6 cal ka bp surface waters in the northern bob were 2 5 ps 8 fresher andaman sea were 3 8 ps 12 fresher and southern bob were 1 2 ps 3 5 fresher conversely during the last glacial maximum lgm surface waters in the northern bob were 2 9 ps 9 more saline while andaman sea were essentially unchanged and southern bob were 1 7 ps 4 9 more saline compared to modern the relative freshness of the andaman during the last glacial maximum is likely the result of basin morphology during sea level low stand resulting in reduced surface water mixing with the open bob as well as shelf emergence causing increased proximity of the core locations to river outflow sensitivity experiments using a regional ocean model indicate that the increased mid holocene north to south 20 n to 5 n salinity gradient can be achieved with a 50 increase in precipitation runoff while the decreased glacial age gradient can be achieved with a 50 reduction in precipitation runoff during the deglaciation both surface and thermocline dwelling species in the andaman and northern bob exhibit depleted 18 o within the younger dryas yd indicating colder and or more saline conditions none of the records from the southern bob site have clear yd structure possibly due to the combined effects of bioturbation and low sedimentation rates

eddies and currents in the bay of bengal during summer monsoons abstract the southwest monsoon current smc in the bay of bengal bob and prominent eddies surrounding it in particular an anticyclonic eddy ae to the southeast and a cyclonic eddy sri lanka dome sld to the east of sri lanka were investigated using field observations numerical simulations satellite imagery laboratory experiments and theoretical studies the field campaigns were conducted in 2015 and 2018 respectively in conjunction with the air sea interactions in the northern indian ocean asiri and monsoon intra seasonal oscillations in bay of bengal miso bob research initiatives ship observations confirmed the presence of a annually recurring ae about 500 km southeast of sri lanka with surface velocities up to 1 m s 1 size in the meridional direction 200 km and penetration approximately to the depth of the thermocline 150 m satellite observations and coamps model simulations show that the ae and the sld are formed following the appearance of the smc in early summer and both evolve during july august and disappear in september this result is at odds with the prevailing notion that the ae is a result of the interaction between the smc and rossby waves arriving from the southeast of the bob carrying energy of a blocked wyrtki jet at the sumatra coast such waves do not arrive in the southwestern bob until august september simultaneous appearance of ae and sld is inconsistent with a recently proposed mechanism in which sld is formed due to separation of the smc from the sri lanka coast a new hypothesis is proposed wherein the ae and the sld are generated by topographically trapped rossby wave response of the smc to perturbations by the sri lankan coast observations of the size location and origins of the ae were broadly consistent with this hypothesis so were the results of a laboratory experiment designed to mimic natural flow in the bob by creating an eastward jet smc on a simulated plane sea surface temperature sst observations show that the smc carries colder upwelled water from the southern sri lankan and indian coasts and distributes it within the surface waters of the ae and beyond thus the surface waters of the ae are colder than that of the sld notwithstanding perceived local upwelling in the sld suggesting that smc may play a controlling role in the air sea interactions of the southern bob

probability distributions for maximum wave and crest heights the paper discusses short and long term probability models of ocean waves the gaussian theory is reviewed and nonlinear short term probability distributions are derived from a narrow band second order model the nonlinearity has different impact on different measurement techniques and this is further demonstrated for wave data from the wavemod crete measurement campaign and laser data from the north sea finally we give some examples on how the short term statistics may be used to estimate the probability distributions for the maximum waves during individual storms as well as in a wave climate described by long term distributions

the dynamics of the southwest monsoon current in 2016 from high resolution in situ observations and models abstractthe strong stratification of the bay of bengal bob causes rapid variations in sea surface temperature sst that influence the development of monsoon rainfall systems this stratification

numerical modelling of tidally generated internal wave radiation from the andaman sea into the bay of bengal abstract semi diurnal internal waves generated by tides in a high resolution numerical model that includes the andaman sea archipelago are found to propagate into the central bay of bengal and reach the coasts of india and sri lanka the waves are also present in subsurface temperature records from rama moorings and their propagation speed across the bay of bengal agrees well with satellite remote sensing from modis imagery in spite of the hydrostatic nature of the model the internal waves are simulated by a fully coupled ocean atmosphere prediction system exchanging surface fluxes between the air and sea at high frequency and at high resolution for the ocean a hydrostatic model including diurnal and semi diurnal tides provides a 2 km resolution representation of the entire bay of bengal in the ocean model simulations the semi diurnal internal waves interact with the mesoscale circulation and surface waves and modify the flow and the stratification by comparing coupled ocean wave model runs with tides and without tides but forced by identical surface fluxes from the atmosphere it is demonstrated that the inclusion of diurnal and semi diurnal tides act to cool the core of the thermocline while increasing the temperature above and below it along the pathway of the internal waves a result that likely is due to vertical mixing by the waves

residual state of sands abstractthe uniqueness and form of the critical state line for sands have been widely debated in the literature when particles crush in this paper the large displacement behaviors of two clean sands and a silty sand are studied using ring shear and triaxial compression shear tests significant particle damage occurred in the shear bands of the ring shear tests at very large shear displacements 10 m in the ring shear tests particle damage and rearrangement reorientation were complete in the ring shear tests and a state of constant shear stress constant effective stress and constant volume was achieved in the crushed sand accordingly a new definition is proposed for the residual state of damaged crushed sands which is reached only within the shear band it is shown that the critical state of the original sand without particle crushing and the residual state with particle crushing are independent of sand fabric moist tamping and air pluviation and consolidation stress 29 770 kpa and

reactivation mechanism of ancient giant landslides in the tectonically active zone a case study in southwest china the reactivation mechanism and stability of ancient landslides are the major concerns in the tectonically active zone a detailed case study has been conducted to examine the reactivation mechanism of ancient landslides in southwest china by investigating the reactivation process shear strength and stability field investigation suggests that the reactivation of ancient giant slides such as the luosiwan slide is attributed to the cumulative effect of adverse geological structural condition and intensive artificial processes however long term observation has shown that the ancient giant landslides usually remain stable in the remote area in spite of such adverse conditions ring shear tests also indicate high peak shear strength of the sliding zone soils however the shear strength decreases significantly once displacement occurs at the toe of giant landslide due to engineering construction the construction process could be considered as the critical triggering factor for the reactivation of ancient giant landslide which exerts sudden changes in the forces acting on the slope both long term adverse geological evolution and sudden change in the strength lead to the reactivation of giant landslide this study also suggests that liquefaction plays an important role in the failure behavior of reactivated ancient landslide an effective drainage system has to be set up during engineering construction so as to reduce the probability of reactivation of ancient landslides

downslope volume enlargement of a debris slide debris flow in the 1999 hiroshima japan rainstorm abstract following a heavy rainstorm on 29 june 1999 hundreds of slope failures occurred in granitic mountains in hiroshima prefecture japan among these events a highly mobile landslide termed the kameyama landslide in this paper which occurred in kameyama area of hiroshima city was the most catastrophic and was investigated in detail the displaced soil mass from the source area of this landslide traveled about 300 m and deposited a volume more than 10 times as great as that in the source area the landslide originated in and traversed a valley shaped concave slope covered by pre existing colluvial debris deposits in addition a spring was visible in the source area and very shallow ground water was observed in an observation pit dug in the source area thus it is inferred that the ground water table rose quickly during the rainfall and that this rise triggered the slope failure in the source area based on a field survey along the landslide cross section a possible explanation for the mechanism of the landslide was obtained the displaced soil mass from the source area impacted the debris deposit in the path of the landslide thus triggering liquefaction failure of the saturated part of debris the original landslide and the liquefied debris then moved downslope as a single mass to examine this assumption ring shear tests were performed on samples taken from the source area undrained ring shear tests on the saturated samples showed that the sample is highly liquefiable and liquefaction failure could have been triggered in the debris deposits by a very small impact from the displaced soil mass of the initial failure in addition laboratory tests simulating the impacts on the debris deposits at natural water content i e unsaturated at the survey time 2 days after the failure showed that although shear failure could be caused by the assumed impact force the displaced soils stopped after a few centimeters displacement indicating that existence of a saturated zone in debris deposits is prerequisite for this kind of failure

impact of internal waves on sound propagation off bhimilipatnam east coast of india internal waves iws are identified off bhimilipatnam east coast of india from the time series ctd hourly interval and thermistor chain data 2 minute interval collected during 23 25 feb 2007 the measurements were carried out at 94 m water depth on the continental shelf edge these data sets are used to describe the characteristics of iws and their impact on acoustic fields garrett and munk gm model has been used to predict the characteristics of low frequency lf iws with space and time active iws are seen in the layer 54 m 94 m with a velocity of 0 548 km hr 1 and the wavelengths of the order of 0 03 km to 21 8 km the model could capture the iw features in the thermocline region accurately than at the bottom this could be due to the limitation of the model which considers linearity high frequency iws observed at the bottom could be due to the advection of tidal currents over the shallow irregular bottom in the presence of stratification the study emphasizes linear iws rather than transient non linear waves induced by tidal interaction with topography acoustic simulation results for low frequency iw field reveal that the intensity loss anomaly of eigenrays was found to be 2 86 db to 15 59 db in the water column and maximum 38 48 db was observed at the bottom due to the bottom interaction our results are well compared with those reported earlier from simulation and acoustic field experiments in the northern indian ocean

powder x ray diffraction analysis of homogeneous and heterogeneous sedimentary dolostones abstract the ca molar ca ca mg 100 in sedimentary dolomite which ranges from 48 ca to 62 5 ca can be determined by atomic absorption spectrometry electron microprobe analysis or powder x ray diffraction analysis the latter procedure which relies on the fact that the position of the d104 reflection depends linearly on the ca content offers an easy and relatively inexpensive method of determining ca in dolomite to date such analyses have assumed that the dolostone is homogeneous with respect to the ca content of its constituent dolomite crystals herein the xrd technique is extended to compositionally heterogeneous dolostones a considerable amount of important information can be derived from x ray diffractograms of dolostones if they are analyzed with peak fitting techniques pf xrd specifically this technique allows 1 determination of the ca with an accuracy of 0 5 ca 2 identification of heterogeneous dolostone samples formed of more than one population of dolomite crystals as defined by their ca content and 3 derivation of the proportion of each population of dolomite crystals with an accuracy of 10 the pf xrd technique is a powerful analytical tool that provides valuable information on the major element composition of low fe dolomite compared to other techniques the pf xrd technique is accurate rapid relatively inexpensive and easy to use

on the dynamics of the sri lanka dome in the bay of bengal east of sri lanka in the northern indian ocean a cold dome known as the sri lanka dome sld develops during southwest monsoon season june september the sld first forms around may matures in july and decays around september in association with the strong cyclonic wind stress curl in this study the structure and dynamics of sld in response to the climatic events such as the indian ocean dipole iod are examined our results reveal that these climatic events modulated the subsurface temperature variability in the thermocline at 100 m depth whose signature was also evident in the satellite derived sea surface height ssh anomaly in the sld region we find that the mechanisms for the formation of sld are consistent with previous research and there is year to year variability in the sld dynamics this study also reveals that the atmospheric parameters including vertical wind shear and mid tropospheric relative humidity are high over the sld region and adjacent southern bay of bengal and show an upward increasing trend over the decades this has impacted the atmospheric parameters over the northern bay of bengal over the decades and as a consequence the total number of monsoon depressions june september decreased over the decades from 1980 to 2015 as reported by the india meteorological department new delhi thus the new insight emerged from this study is the variability in the cyclogenesis and the occurrence of total number of monsoon depressions over northern bay of bengal over the decades are much related to the sld dynamics

the mechanism of high speed motion and damming of the tangjiashan landslide abstract understanding the mechanisms of landslide failure and resulting damming processes is crucial for constraining the hazard chain associated with landslide damming events on may 12 2008 the wenchuan earthquake caused a large number of secondary hazardous events such as landslides and collapses most of which occurred in high mountain gorges in these areas the sliding distance of landsides is often very short and the landslides are often characterized by high speed short distance and damming using the tangjiashan landslide damming events induced by the wenchuan earthquake as a model this paper reconstructs the three dimensional failure and associated damming caused by the landslide based on a detailed geological investigation of the landslide area and using the dynamic finite element technique the study proposes a four stage model for the failure and damming process of the tangjiashan landslide earthquake induction and progressive destruction of the slide body destruction and high speed sliding of the slide body slide body impact disintegration and river blockage for the formation of a damming body and vibration compression the average speed of the tangjiashan landslide reached a maximum value of 22 m s about 30 s after the earthquake and the landslide reached stability about 60 s later

geochemistry and petrology of a middle tithonian limestone marl rhythmite in the neuquen basin argentina depositional and burial history

physical and mechanical properties of loess discharged from the yellow river into the bohai sea china abstract chinese loess is unique in having great scientific value whilst also playing an important role in societal development large volumes of loess are continually carried by the yellow river from the chinese loess plateau to the bohai sea northeast china forming the yellow river delta the physical and mechanical properties of this loess vary during transportation and these characteristics have been investigated in detail using several samples of estuarine loess collected from tidal flats with different depositional ages the wet densities natural moisture contents specific gravities atterberg limits grain size distributions microstructures and mineral compositions of these samples have been determined our results show that the estuarine loess is classified as silty loess and that its specific gravity plasticity and grain size characteristics were very similar to land derived loess its unit weight and water content increasd during discharge into the sea and its plastic index decreased the estuarine loess also had fewer large pores that were more closely connected than those in land loess as a result of these changes in index properties and pore water chemistry estuarine loess is less susceptible to liquefaction than land derived loess in addition these physical and mechanical properties show strong correlations to the long term depositional history of the delta with older deposits typically having a lower dry density and higher void ratio than younger deposits the results of this study have implications for hazard mitigation and improving our understanding of the mechanisms responsible for loess related geological disasters

sedimentology of rock avalanche deposits case study and review abstract detailed sedimentological studies concerning different facies types and the factors influencing their development such as lithology topography substrates etc were carried out at the carbonate tschirgant rockslide rock avalanche deposit in the eastern alps of austria several depositional facies and sub facies have been identified at this and other sites by many researchers these facies are found throughout the debris regardless of depth or travel distance and result from highly heterogeneous stress distributions in time and space during emplacement one of the most important recent observations in terms of emplacement dynamics is that shear is not confined to the base but is distributed throughout the debris except the coarse carapace due to the preservation of source stratigraphy in these non turbulent mass movements any horizontal facies or grain size variations need to be regarded in context since they strongly depend on source stratigraphy and hence the spatial distribution of lithologies i e geological units of different mechanical properties for example some lithologies do not form a boulder carapace due to absence of large in situ blocks in the source rock mass however at tschirgant slight facies maturation with distance within the same lithology is observed i e clast fragmentation progresses to create the distinct facies characteristic grain size distribution only after some distance travelled these details are revealed through facies based sampling and analysis studies based on bulk sampling in some cases observed progressively reduced grain sizes with distance and depth which might be a function of added variations within different facies sampled together in this paper the wealth of observations on rockslide and rock avalanche sedimentology of the past decades is combined with a detailed case study of a lithologically relatively simple deposit to outline global and site specific depositional structures and facies with the aim to summarize review and refine the current state of knowledge on rock avalanche and rockslide emplacement processes

basinal marine dolomicrite from the pennsylvanian wolfcampian horquilla formation new mexico abstract a 6 m thick sequence of black dolomicrite occurs within a shaley basinal portion of the pennsylvanian wolfcampian horquilla formation new mexico deep water lithologic associations absence of hypersaline and freshwater indicators elevated na and sr contents and marine derived 18o values all indicate that the dolomite precipitated from marine derived water during burial beneath the sediment water interface trace and major element contents and oxygen isotopic compositions of the dolomites exhibit significant covariance sr na and 18o all covary positively with excess ca in the dolomite structure and fe and mn covary negatively with excess ca in the dolomite structure such variations are suggestive of a diagenetic alteration trend ranging from primary marine compositions preserved in calcian dolomite to diagenetic compositions in more stoichiometric dolomite moreover dolomite which preserves primary 18o values exhibits only minor variation in 13c this is in contrast to the highly variable 13c values observed in tertiary deep water dolomites where sulfate reduction during organic diagenesis plays a key role in promoting dolomitization thus depletion of sulfate was not a prerequisite for dolomitization of basinal carbonates of the hor uilla formation rather dolomitization was promoted by the metastability of the precursor mineralogy while such a mechanism has been postulated for dolomitization of marginal slope facies of oceanic atolls this study extends its application to burial marine dolomitization of deep water micritic sequences

energy of nonlinear internal waves in the south china sea 1 four sets of adcp measurements were taken in the south china sea scs these results were combined with previous satellite observations and internal tide numerical model results analysis suggests that strong internal tides are generated in luzon strait propagate as a narrow tidal beam into the scs are amplified by the shoaling continental slope near tungsha island become nonlinear and evolve into high frequency nonlinear internal waves niw internal waves in the scs have geographically distinct characteristics 1 west of luzon strait the total internal wave energy eiw is 10 that predicted by garrett munk spectra egm levine 2002 there is no sign of niw 2 near tungsha island eiw 13 egm strong nonlinear and high harmonic tides are present repetitive trains of large amplitude niw appear primarily at a semidiurnal periodicity with their amplitudes modulated at a fortnightly tidal cycle the rms vertical velocity of niw shows a clear spring neap tidal cycle and is linearly proportional to the barotropic tidal height in luzon strait with a 1 85 day time lag consistent with the travel time of internal tides from luzon strait to tungsha island 3 at the northern scs shelfbreak eiw 4 egm single depression waves are found but no multiple waves packets are evident 4 on the continental shelf eiw 2 egm both depression and elevation niw exist

arabian sea and bay of bengal exchange of salt and tracers in an ocean model exchanges of mass and salt between the mixed layers in the arabian sea and the bay of bengal are examined in a model of the indian ocean using passive tracers as a tool to map the pathways inflow of high salinity water from the arabian sea into the bay of bengal is significant and occurs after the mature phase of the southwest monsoon freshwater transport out of the bay of bengal is southward throughout the year along the eastern boundary of the indian ocean low salinity water transport into the arabian sea occurs in the somali current during the southwest monsoon closing a clockwise path of water mass transport only a small fraction of low salinity water is advected into the eastern arabian sea from the bay of bengal

a kinematic model of the hsiaolin landslide calibrated to the morphology of the landslide deposit abstract this paper presents results of a case study on the hsiaolin catastrophic landslide including its kinematic process and the geometry of deposition based on geomorphologic analysis the landslide initiated in thick multi aged colluvium soils at the headwaters of a small stream upslope of hsiaolin village a 3d discrete element program pfc3d was used to model the kinematic process that led to the landslide and destruction of hsiaolin village the landslide advanced from debris slide to debris avalanche during the kinematic process assuming a friction coefficient of each particle of 0 1 the predicted maximum velocity was about 70 m s a velocity which permits the debris to cross qishanxi stream and deposit on the opposite bank based on simulation results hsiaolin village was inundated in 60 to 65 s after failure initiation and at 112 s after the event the debris avalanche came to rest forming a landslide dam

episodes of nonlinear internal waves in the northern east china sea 1 episodes of high frequency internal waves which lasted approximately 3 hours were detected in the northern east china sea during a specific phase of the barotropic tide i e low tide at 32 n 125 e the observed internal waves influenced the whole water column the wave packets were presumably generated near the ocean shelf break approximately 200 km to the southeast of the test site during several internal wave episodes which coincided with the neap tide large amplitude solitary wave like features emerged preceding higher frequency internal waves shear instability of tidal currents is explored as a possible mechanism for sustaining or regenerating internal waves in the packets during the course of their propagation it is suggested that rotating velocity field of tidal current supports sufficient vertical shear within wave packets to cause outbreaks of k h instability these instabilities may gradually transition to more symmetric holmboe waves following the increase of the bulk richardson number

fast shearing of pre existing shear zones in soil the paper presents results from a laboratory investigation into the influence of fast rates of displacement on the residual strength of soil this influence was studied in the ring shear apparatus shear zones were formed by slow drained shearing and then tested at alternately fast and slow rates of displacement results from a wide range of natural soils are presented all soils show initially an increase in strength when resheared at fast rates of displacement the strength then tends to decrease with fast displacement to a minimum value the fast residual strength three types of rate effects on the residual strength are identified a positive rate effect in soils showing a fast residual strength higher than the slow residual a neutral rate effect in soils showing a constant fast residual strength equal to the slow residual irrespective of rate of displacement and a negative rate effect in soils showing a significant drop in fast residual strength below the slow residual when sheared at rates higher

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

modelling the hysteresis in the velocity pattern of slow moving earth flows the role of excess pore pressure this paper describes the velocity pattern of a slow moving earth flow containing a viscous shear band and a more or less rigid landslide body on top in the case of small groundwater fluctuations bingham s law may describe the velocity of these slow moving landslides with velocity as a linear function of excess shear stress many authors have stated that in most cases a non linear version of bingham s law best describes the moving pattern of these earth flows however such an exponential relationship fails to describe the hysteresis loop of the velocity which was found by some authors these authors showed that the velocity of the investigated earth flows proved to be higher during the rising limb of the groundwater than during the falling limb to explain the hysteris loop in the velocity pattern this paper considers the role of excess pore pressure in the rheological behaviour of earth flows by means of a mechanistic model it describes changes in lateral internal stresses due to a change in the velocity of the earth flow which generates excess pore pressure followed by pore pressure dissipation model results are compared with a hysteresis in the velocity pattern which was measured on the valette landslide complex french alps copyright 2005 john wiley sons ltd

experimental study on the shearing behavior of saturated silty soils based on ring shear tests the shearing behavior of saturated silty soils has been examined extensively by performing undrained and partially drained the upper drainage valve of the shear box was open during shearing ring shear tests on mixtures of a sandy silt with different loess contents by performing tests at different initial void ratios the shear behavior of these silty soils at different initial void ratios is presented and discussed undrained shear test results showed that the liquefaction phenomena in ring shear tests were limited within the shear zone for a given void ratio or interfine void ratio both the peak and steady state shear strengths decreased with increase of loess content the partially drained shear tests revealed that a great reduction in the shear strength could result after the shear failure due to the buildup of excess pore water pressure within the shear zone the magnitude of reduction in shear strength after failure was affected by the initial void ratio the shear speed after failure as well as the loess content in the sample for a given void ratio or interfine void ratio with increase of loess content the drained peak shear strength became smaller while the brittleness index became greater it was also found that due to localized shearing the permeability of the soil within the shear box after drained shearing could be three orders of magnitude smaller than before shearing

evidence for the existence of persian gulf water and red sea water in the bay of bengal the high salinity water masses that originate in the north indian ocean are arabian sea high salinity water ashsw persian gulf water pgw and red sea water rsw among them only ashsw has been shown to exist in the bay of bengal we use ctd data from recent cruises to show that pgw and rsw also exist in the bay the presence of rsw is marked by a deviation of the salinity vertical profile from a fitted curve at depths ranging from 500 to 1000 m this deviation though small of the order of similar to 0 005 psu and therefore comparable to the ctd accuracy of 0 003 psu is an order of magnitude larger than the similar to 0 0003 psu fluctuations associated with the background turbulence or instrument noise in this depth regime allowing us to infer the existence of rsw throughout the bay pgw is marked by the presence of a salinity maximum at 200 450 m in the southwestern bay pgw can be distinguished from the salinity maximum due to ashsw because of the intervening arabian sea salinity minimum this salinity minimum and the maximum associated with ashsw disappear east and north of the south central bay 85a degrees e 8a degrees n owing to mixing between the fresher surface waters that are native to the bay bay of bengal water or bbw with the high salinity ashsw hence ashsw is not seen as a distinct water mass in the northern and eastern bay and the maximum salinity over most of the bay is associated with pgw the surface water over most of the bay is therefore a mixture of ashsw and the low salinity bbw as a corollary we can also infer that the weak oxygen peak seen within the oxygen minimum zone in the bay at a depth of 250 400 m is associated with pgw the hydrographic data also show that these three high salinity water masses are advected into the bay by the summer monsoon current which is seen to be a deep current extending to 1000 m these deep currents extend into the northern bay as well providing a mechanism for spreading ashsw pgw and rsw throughout the bay

a summer monsoon pump to keep the bay of bengal salty the bay of bengal receives a large influx of freshwater from precipitation and river discharge outflow of excess freshwater and inflow of saltier water is required to prevent the bay from freshening relatively fresh water flows out of the bay along its boundaries and inflow of saltier water occurs via the summer monsoon current smc which flows eastward from the arabian sea into the bay this saltier water however slides under the lighter surface water of the bay maintaining the salt balance of the bay therefore demands upward mixing of this saltier subsurface water here we show that an efficient mechanism for this mixing is provided by upward pumping of saltier water in several bursts during the summer monsoon along the meandering path of the smc advection by currents can then take this saltier water into the rest of the basin allowing the bay to stay salty despite a large net freshwater input

speed and evolution of nonlinear internal waves transiting the south china sea abstract in the south china sea scs 14 nonlinear internal waves are detected as they transit a synchronous array of 10 moorings spanning the waves generation site at luzon strait through the deep basin and onto the upper continental slope 560 km to the west their arrival time speed width energy amplitude and number of trailing waves are monitored waves occur twice daily in a particular pattern where larger narrower a waves alternate with wider smaller b waves waves begin as broad internal tides close to luzon strait s two ridges steepening to o 3 10 km wide in the deep basin and o 200 300 m on the upper slope nearly all waves eventually develop wave trains with larger steeper waves developing them earlier and in greater numbers the b waves in the deep basin begin at a mean speed of 5 greater than the linear mode 1 phase speed for semidiurnal internal waves computed using climatological and in situ stratification the a waves travel 5 10 faster than b waves until they reach

southern bay of bengal currents and salinity intrusions during the northeast monsoon shipboard velocity and hydrographic profiles collected in december 2013 along with drifter observations satellite altimetry global ocean nowcast forecast products and coupled model simulations were used to examine the circulation in the southern bay of bengal as part of ongoing international research efforts in the region the observations captured the southward flowing east india coastal current eicc off southeast india and east of sri lanka the eicc was approximately 100 km wide with speeds exceeding 1 m s 1 in the upper 75 m east of the eicc a subsurface intensified 300 km wide northward current was observed with maximum speeds as high as 1 m s 1 between 50 m and 75 m the eicc moved low salinity water out of the bay and the subsurface northward flow carried high salinity water into the bay during typical northeast monsoon conditions during a time period when the central equatorial indian ocean was experiencing a westerly wind burst related to the madden julian oscillation mjo event while the northward subsurface high salinity flow has previously been observed during the southwest monsoon it was observed during the northeast monsoon the observations are consistent with northward high salinity subsurface flow in numerical model solutions the analysis suggests that direct forcing along the equator may play a significant role for high salinity intrusions east of sri lanka

mechanism of a long runout landslide triggered by the august 1998 heavy rainfall in fukushima prefecture japan abstract heavy rainfall from 26 to 31 august 1998 triggered many landslides in nishigo village of southern fukushima prefecture japan the hiegaesi landslide a long runout landslide with travel angle of 11 which occurred in loamy volcanic ash pumice layer and was deposited in a nearby rice paddy was investigated in an observation pit dug in the middle part of the landslide deposit the sliding zone just above the deflected rice plants was observed and it was confirmed that grain crushing occurred in the sliding zone the triggering and sliding mechanisms of this landslide then were investigated by ring shear tests in laboratory for the triggering mechanism one saturated naturally drained test test a torque controlled test and one saturated undrained test test b speed controlled test were conducted on the samples taken from the source area of the landslide even in the naturally drained test opening the upper drain valve of the shear box a temporary liquefaction occurred in the undrained test excess pore pressure was generated along with shearing and sliding surface liquefaction phenomenon was observed the effective stress and shear resistance finally decreased to near zero these results can explain the observed phenomenon of small friction resistance like a flow of liquid when the sliding mass slid out of the source area for the sliding mechanism of the landslide in the rice paddy saturated undrained test test c speed controlled test was performed on soil sample above the deflected rice plants the apparent friction angle obtained in this test was 8 in addition the residual friction angle measured after test b and test c was the same value of 41 combining with the observation on the shear zone in the ring shear box after test c it is concluded that during the sliding in rice paddy the undrained shear strength of the soil layer itself mainly influenced the high mobility of the landslide probably because the friction between rice plants and soils is greater than the undrained shear strength inside the soil mass

the generation and evolution of nonlinear internal waves in the deep basin of the south china sea abstracttime series observations of nonlinear internal waves in the deep basin of the south china sea are used to evaluate mechanisms for their generation and evolution internal tides are generated by tidal currents over ridges in luzon strait and steepen as they travel west subsequently generating high frequency nonlinear waves although nonlinear internal waves appear repeatedly on the western slopes of the south china sea their appearance in the deep basin is intermittent and more closely related to the amplitude of the semidiurnal than the predominant diurnal tidal current in luzon strait as the internal tide propagates westward it evolves under the influence of nonlinearity rotation and nonhydrostatic dispersion the interaction between nonlinearity and rotation transforms the internal tide into a parabolic or corner shape a fully nonlinear two layer internal wave model explains the observed characteristics of internal tide evolution in the deep basin for different representative forcing cond

the hydrogeological attributes and mechanisms of a receding sedimentary terrain in the anambra basin southern nigeria this research investigated the hydrogeological aspects associated with severe gulling and landsliding on a vulnerable sedimentary terrain in the context of the newly identified deformation patterns and large numbers of recently discovered scars clustering slopes on identical coordinates results of field survey remote sensing vertical electrical sounding and experimental analyses were presented to explain the causes and mechanisms of the mass movements ravaging the terrain a digital elevation model accurately captured the diverse geomorphologic elements including landslide scars hills ridges valleys plains and rivers that matched field observations the model aided the identification of previously unknown steep incised channels active headcuts unstable side walls and a seasonal river flowing near the slopes having large number of landslide scars it was observed that areas that lay on higher elevations where the clusters occur were dominated by fresh scars while the moderate to low elevations were dominated by older ones majority of the slope failures initiated within the sandstone as shallow slides 1 m to the sliding surface covering 104 m2 with short runout distances bigger landslides although few occurred as isolated individual events initiated at the sandstone shale boundary on distinct slopes the steepness of the slopes seemed controlled by slope morphology concavity which probably influenced the number and distribution of landslide events the steeper slopes were more concave and had the highest concentration of scars shallow water table 4 11 m and increased instability brittleness index under increasing over consolidation ratio are the critical failure factors

quantitative assessment on the influence of rainfall on landslides in jianshi county of qing river basin china rainfall is one of the main inducing factors of landslide disaster based on many years of landslide monitoring data and rainfall data of jianshi county 66 landslides occurred from 2002 to 2008 were chosen which is about 52 38 of the total 126 landslides in the whole area there are 13 landslides with deformation or displacement over twice this is about 19 70 of 66 landslides chosen according to analysis the correlation between rainfall and landslides with the geostatistics method the critical rainfall and effective rainfall are determined using the bayes statistical inference model to improve the probability model the probabilities of landslide early warning system zones are determined the landslide early warning model is established on basis of the result of landslide susceptibility rainfall model and probabilistic model with arcgis software the probability value t is from 0 002168 to 0 909062 the whole county is divided into four grades of landslide early warning system the data of second deformation or displacement of 13 landslides induced by the rainfall are used to validate the model totally the result of landslide early warning model is scientific and reliable the rainfall data of eight landslides are in line with the model and in the range of level iv v the accuracy is about 61 54 according to the relationship between landslide and rainfall the distributions of 11 landslides are located in the level v zone and the accuracy is 84 62 according to the relationship between landslide early warning result

influence of grass roots on shear strength of pyroclastic soils this paper investigates the effects of indigenous vegetation on the shear strength of loose pyroclastic soils of the campania region southern italy these soils are frequently affected by shallow

the relationship of mantle derived fluids to gold metallogenesis in the jiaodong peninsula evidence from d o c s isotope systematics abstract the largest gold district in china is the jiaodong peninsula where three types of gold deposits are recognized quartz vein fracture altered and breccia types the first two developed along a group of ne trending faults and are hosted by granitic intrusions dated at 160 to 150 ma biotite granite and 130 to 126 ma granodiorite and by metamorphic rocks of the precambrian crystalline basement the breccia type gold system is mainly located around the northern margin of the jiaolai cretaceous basin where mineralisation is controlled by both detachment fractures and ne trending faults this study is based on stable isotope determinations from ten gold deposits including linglong jiaojia sanshandao cangshang wang ershan dayigezhuang denggezhuang pengjiakuang fayunkuang and dazhuangzi as well as the linglong jurassic biotite granite guojialing cretaceous granodiorite and archean gneiss the stable isotope systematics reflect the style of the three types of gold deposits but also show that they belong to the same metallogenic system in which the hydrothermal fluids were derived from a mantle fluid reservoir and mixed with crustal fluids the ore forming age is later than both the jurassic biotite granite and cretaceous granodiotite but overlaps with the 121 to 114 ma ages of lamprophyre and diabase dykes the hydrothermal fluids that were responsible for both gold mineralisation and the retrograde alteration of the diabase and lamprophyre dykes are similar and represent a co 2 and potassium rich system this fluid system is interpreted to be the consequence of cretaceous lithospheric thinning asthenospheric upwelling and mantle degassing in eastern china

strong intraseasonal variability of meridional currents near 5 n in the eastern indian ocean characteristics and causes abstractthis paper reports on strong intraseasonal upper ocean meridional currents observed in the indian ocean between the bay of bengal bob and the equator and elucidates the underlying physical processes responsible for them in situ measurements from a subsurface mooring at 5 n 90 5 e reveal strong intraseasonal variability of the meridional current with an amplitude of 0 4 m s 1 and a typical period of 30 50 days in the upper 150 m which by far exceeds the magnitudes of the mean flow and seasonal cycle such prominent intraseasonal variability is however not seen in zonal current at the same location further analysis suggests that the observed intraseasonal flows are closely associated with westward propagating eddylike sea surface height anomalies sshas along 5 n the eddylike sshas are largely manifestations of symmetric rossby waves which result primarily from intraseasonal wind stress forcing in the equatorial waveguide and reflection of the equatorial kelvin waves at the eastern bou

the railroad switch effect of seasonally reversing currents on the bay of bengal high salinity core the southwest monsoon current smc flows eastward from the arabian sea into the bay of bengal bob during summer advecting a core of high salinity water this high salinity core has been linked with arabian sea high salinity water that is presumed to enter the bob directly from the arabian sea via the smc here we show that the high salinity core originates primarily from the western equatorial indian ocean reaching the bob via the somali current the equatorial undercurrent and the smc years with anomalously saline high salinity cores are linked with the east africa coastal current and the somali current winter convergence and an anomalously strong equatorial undercurrent seasonal reversals that occur at the somali current and smc junctions act as railroad switches diverting water masses to different basins in the northern indian ocean interannual fluctuations of the equatorial undercurrent are linked to wind stress and el nino

rainfall induced landslides by deficit field matric suction in unsaturated soil slopes landslides are mainly triggered by decrease in the matric suction with deepening the wetting band by rainfall infiltrations this paper reports rainfall induced landslides in partially saturated soil slopes through a field study a comprehensive analysis on umyeonsan mt landslides in 2011 was highlighted the incident involves the collapse of unsaturated soil slopes under extreme rainfall event fundamental studies on the mechanism and the cause of landslides were carried out a number of technical findings are of interest including the failure mechanism of a depth of soil and effect of groundwater flow the downward movement of wetting band and the increase of groundwater level based on this an integrated analysis methodology for a rainfall induced landslide is proposed in this paper that incorporates the field matric suction for obtaining hydraulic parameters of unsaturated soil the field matric suction is shown to govern the rate of change in the water infiltration for the landslide analysis with respect to an antecedent rainfall special attention was given to a one dimensional infiltration model to determine the wetting band depth in the absence of the field matric suction the results indicate that landslide activities were primarily dependent on rainfall infiltration soil properties slope geometries vegetation and groundwater table positions the proposed methodology has clearly demonstrated both shallow and deep seated landslides and shows good agreement with the results of landslide investigations

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide