effects of relative density in progressive sliding of tailings deposits insights from flume tests abstract we present a series of flume tests to observe the process of tailings slope failure when subjected to a concentrated water flow progressive flow slides were observed in a range of tailing deposits with varying relative densities in which hydraulic conductivity reduced with increasing relative density slope densification by compaction of very loose or loose tailings deposits can lead to a lower permeability generating excess pore pressure and subsequently reducing slope stability this is evident from the great number of acoustic emission signals before sudden failure and from a sharp increase in the surface displacement and internal displacement observed after excess pore pressure generation the variation of fluid pressure distribution results in successive sliding onset at the toe and progressing from the toe to the rear of the slope excess pore pressure generation is found to occur after rather than prior to sliding and it only occurs along the slip surface an optimal relative density of 0 35 was identified in which the slope failure changes from a sudden collapse to a progressive failure however the optimal relative density may vary with the height of the slope this research extends existing knowledge about behavior of tailings materials while the observed discrepancy between the failure mechanisms of slopes made of loose and dense deposits could provide insights for preventing failures of tailings dams

ring shear tests on soil from the vaiont landslide slip surface the paper presents results from ring shear tests carried out on two samples from the slip surface of the vaiont landslide in north italy the tests were carried out at slow and fast rates of shearing in order to determine values of the coefficient of friction appropriate to static and dynamic aspects of the landslide both samples showed a significant loss of strength negative rate effect up to 60 below the slow residual strength when sheared at rates of shearing greater than 100 mm min the observed loss of strength may explain the high acquired velocity of the landslide or alternatively some combination of this and other mechanisms may have taken place le papier presente les resultats d essais de cisaillement par anneau effectues sur deux echantilions preleves sur la surface de cisaillement du glissement de terrain vaiont dans le nord de l italie les essais ont ete menes avec des vitesses de cisaillement lentes et rapides de maniere a pouvoir determiner les valeurs des coefficients de frotteme

shear bands in plane strain compression of loose sand experimental results are presented which characterize the behaviour of a loose fine grained water saturated sand tested under globally undrained and drained conditions in a plane strain apparatus the objective of this investigation is to provide insight into the phenomenon of shear banding in loose sand together with local measurements of boundary forces and deformations stereophotogrammetry is used to investigate the progression of strain localization in plane strain compression typical results and findings concerning the evolution of non homogeneous deformation are presented in detail shear banding occurred in both undrained and drained experiments on loose masonry sand in general temporary modes of strain localization observed during macroscopically uniform deformations of a specimen gave way to a single persistent shear band a clear pattern of onset of the formation of the persistent shear band mobilization of the maximum effective friction and complete formation of the band was observ

thermochronology geochronology and upper crustal structure of the cordillera real implications for cenozoic exhumation of the central andean plateau 1 structural mapping 40ar 39ar and fission track thermochronology u pb geochronology and basin analysis reveal rapid cooling during middle eocene late oligocene and late miocene pliocene exhumation in the central andean plateau of bolivia in the 4 6 km high cordillera real numerous granites and sw directed fold thrust structures define the central andean backthrust belt along the altiplano eastern cordillera boundary u pb zircon analyses indicate permo triassic granitic magmatism with less extensive magmatism of late oligocene age mapping reveals low magnitudes of slip 5 km depth the 26 ma quimsa cruz granite postdated most thrust structures suggesting that upper crustal shortening in the cordillera real had largely ceased by late oligocene time results of 40ar 39ar and fission track modeling help constrain the moderate to low temperature 350 c cooling history revealing two phases of rapid cooling from 45 40 ma to 26 ma and from 11 ma onward initial cooling coincided with middle eocene late oligocene deformation in the backthrust belt and associated deposition of coarse clastic sediments in the altiplano basin eocene oligocene exhumation of 7 5 km of upper crust is estimated on the basis of thermochronologic data rapid late miocene and younger cooling involved an estimated 3 5 km of exhumation and occurred in the apparent absence of upper crustal shortening these findings suggest that crustal shortening and resultant exhumation of middle eocene late oligocene age played a major role in construction of the central andes however for late miocene exhumation the importance of alternative nonshortening mechanisms is difficult to ascertain due to a poor understanding of subsurface structures we speculate that greater precipitation on the eastern edge of the central andean plateau north of 17 5 s was a key factor in driving rapid youthful exhumation of the cordillera real

shear rate dependent strength control on the dynamics of rainfall triggered landslides tokushima prefecture japan a typhoon typhoon no 10 attacked shikoku island and the tyugoku area of japan in 2004 this typhoon produced a new daily precipitation record of 1317 mm on shikoku island and triggered hundreds of landslides in tokushima prefecture one catastrophic landslide was triggered in the shiraishi area of kisawa village and destroyed more than 10 houses while also leaving an unstable block high on the slope the unstable block kept moving after the event showing accelerating and decelerating movement during and after rainfall and reaching a displacement of several meters before countermeasures were put into place to examine the mechanism for this landsliding characteristic samples weathered serpentinite were taken from the field and their shear behaviours examined using ring shear tests the test results revealed that the residual shear strength of the samples is positively dependent on the shear rate which may provide an explanation for the continuous accelerating decelerating process of the landsliding the roughness of the shear surface and the microstructure of the shear zone were measured and observed by laser microscope and sem techniques in an attempt to clarify the mechanism of shear rate effect on the residual shear strength copyright 2010 john wiley sons ltd

stratigraphy and chronology of upper cretaceous lower paleogene strata in bolivia and northwest argentina integration of sequence stratigraphy magnetostratigraphy ar ar dating and paleontology considerably advances knowledge of the late cretaceous early paleogene chronostratigraphy and tectonic evolution of bolivia and adjacent areas the partly restricted marine el molino formation spans the maastrichtian and danian 73 60 0 ma deposition of the alluvial to lacustrine santa lucia formation occurred between 60 0 and 58 2 ma the widespread erosional unconformity at the base of the cayara formation is 58 2 ma this unconformity separates the upper puca and corocoro supersequences in bolivia and is thus coeval with the zuni tejas sequence boundary of north america the thick overlying potoco and camargo formations represent a late paleocene oligocene foreland fill the onset of shortening along the pacific margin at 89 ma initially produced rifting in the distal foreland santonian campanian eastward onlapping deposits indicate subsequent waning of tectonic activity along the margin significant tectonism and magmatism resumed along the margin at 73 ma and produced an abrupt increase in subsidence rate and other related phenomena in the basin subsidence was maximum between 71 and 66 ma due to the early maastrichtian global sea level high marine waters ingressed from the northwest into this underfilled basin subsidence decreased during the late maastrichtian and was low during the danian it increased again in the latest danian for which a slight transgression is recorded and peaked in the early selandian tectonism between 59 5 and 58 2 ma produced a variety of deformational and sedimentary effects in the basin and correlates with the end of emplacement of the coastal batholith the subsequent 58 2 ma major unconformity marks the onset of continental foreland basin development which extended into andean bolivia during the late paleocene oligocene interval this basin underwent internal deformation as early as eocene time in the altiplano and cordillera oriental these early structures previously assigned to the late oligocene early miocene orogeny probably accommodated observed tectonic rotations in the eocene oligocene

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

the viscous creep component in shallow clayey soil and the influence of tree load on creep rates creep tests carried out on silty clay samples of a terres noires colluvium show that even in shallow soils 1 m in depth stress conditions can be high enough to initiate measurable creep displacements by the mechanism of continuous viscous creep it is therefore not necessary to think exclusively of a shrink swell mechanism seasonal creep in order to explain these slow movements in the soil the creep tests also show a negative correlation between effective normal stress and the viscosity of the soil material therefore in shallow soils removal of an external load forest clearing might increase the creep rate at lower slope angles and therefore decrease the stability of the slopes at higher slope angles removal of external load decreases the creep rate

displacement fields from point cloud data application of particle imaging velocimetry to landslide geodesy 1 acquiring spatially continuous ground surface displacement fields from terrestrial laser scanners tls will allow better understanding of the physical processes governing landslide motion at detailed spatial and temporal scales problems arise however when estimating continuous displacement fields from tls point clouds because reflecting points from sequential scans of moving ground are not defined uniquely thus repeat tls surveys typically do not track individual reflectors here we implemented the cross correlation based particle image velocimetry piv method to derive a surface deformation field using tls point cloud data we estimated associated errors using the shape of the cross correlation function and tested the method s performance with synthetic displacements applied to a tls point cloud we applied the method to the toe of the episodically active cleveland corral landslide in northern california using tls data acquired in june 2005 january 2007 and january may 2010 estimated displacements ranged from decimeters to several meters and they agreed well with independent measurements at better than 9 root mean squared rms error for each of the time periods the method provided a smooth nearly continuous displacement field that coincides with independently mapped boundaries of the slide and permits further kinematic and mechanical inference for the 2010 data set for instance the piv derived displacement field identified a diffuse zone of displacement that preceded by over a month the development of a new lateral shear zone additionally the upslope and downslope displacement gradients delineated by the dense piv field elucidated the non rigid behavior of the slide

spatial and temporal variability in denudation across the bolivian andes from multiple geochronometers abstract we quantify spatial and temporal variations in denudation rates across the central andean fold thrust belt in bolivia with particular focus on the holocene measured and predicted 10 be cosmogenic radionuclide crn concentrations in river sediments are used to 1 calculate catchment averaged denudation rates from 17 basins across two transects at different latitudes and 2 evaluate the sensitivity of holocene climate change on the denudation history recorded by the crn data estimated denudation rates vary by two orders of magnitude from 0 04 to 1 93 mm yr 1 with mean values of 0 40 0 29 mm yr 1 in northern bolivia and 0 51 0 50 mm yr 1 in the south results demonstrate no statistically significant correlation between denudation rates and morphological parameters such as relief slope or drainage basin size in addition the crn derived denudation rates do not reflect present day latitudinal variations in precipitation comparison to 130 previously published denudation rates calculated over long thermochronology derived 10 6 yrs medium crn derived 10 2 10 4 yrs and short timescales sediment flux derived 10 1 yrs indicate temporal variations in denudation rates that increase between 0 and 200 over the last 5 ka crn modeling results suggest that the crn derived denudation rates may not be fully adjusted to wetter climate conditions recorded in the central andes since the mid holocene we conclude that large spatial variability in crn denudation may be due to local variations in tectonics e g faulting while large temporal variability in denudation may be due to temporal variations in climate

shear resistance variations in experimentally sheared mudstone granules a possible shear thinning and thixotropic mechanism we present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone little rate dependency of shear resistance was observed in sand sized granules in any wet or dry test while saturated gravel sized granules exhibited significant and abrupt reversible rate weakening from 0 6 to 0 05 at about 2 mm s repeating resistance variations occurred also under constant shear displacement rate mudstone granules generate mud as they are crushed and softened shear thinning and thixotropic behavior of the mud can explain the observed behavior with the viscosity decreasing the mud can flow through the coarser soil pores and migrate out from the shear zone this brings new granules into contact which produces new mud thus the process can start over similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behaviour may play a role in some landslide kinematics

quantifying rainfall controls on catchment scale landslide erosion in taiwan landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical tectonically active mountain belts in this study we quantified landslide erosion triggered by 24 rainfall events from 2001 to 2009 in three mountainous watersheds in taiwan and investigated relationships between landslide erosion and rainfall variables the results show positive power law relations between landslide erosion and rainfall intensity and cumulative rainfall with scaling exponents ranging from 2 94 to 5 03 additionally landslide erosion caused by typhoon morakot is of comparable magnitude to landslide erosion caused by the chi chi earthquake mw 7 6 or 22 24 years of basin averaged erosion comparison of the three watersheds indicates that deeper landslides that mobilize soil and bedrock are triggered by long duration rainfall whereas shallow landslides are triggered by short duration rainfall these results suggest that rainfall intensity and watershed characteristics are important controls on rainfall triggered landslide erosion and that severe typhoons like high magnitude earthquakes can generate high rates of landslide erosion in taiwan copyright 2012 john wiley sons ltd

rate weakening friction characterizes both slow sliding and catastrophic failure of landslides abstract catastrophic landslides cause billions of dollars in damages and claim thousands of lives annually whereas slow moving landslides with negligible inertia dominate sediment transport on many weathered hillslopes surprisingly both failure modes are displayed by nearby landslides and individual landslides in different years subjected to almost identical environmental conditions such observations have motivated the search for mechanisms that can cause slow moving landslides to transition via runaway acceleration to catastrophic failure a similarly diverse range of sliding behavior including earthquakes and slow slip events occurs along tectonic faults our understanding of these phenomena has benefitted from mechanical treatments that rely upon key ingredients that are notably absent from previous landslide descriptions here we describe landslide motion using a rate and state dependent frictional model that incorporates a nonlocal stress balance to account for the elastic response to gradients in slip our idealized one dimensional model reproduces both the displacement patterns observed in slow moving landslides and the acceleration toward failure exhibited by catastrophic events catastrophic failure occurs only when the slip surface is characterized by rate weakening friction and its lateral dimensions exceed a critical nucleation length h h that is shorter for higher effective stresses however landslides that are extensive enough to fall within this regime can nevertheless slide slowly for months or years before catastrophic failure our results suggest that the diversity of slip behavior observed during landslides can be described with a single model adapted from standard fault mechanics treatments

inverse long term stability analysis of a constrained landslide this paper deals with long term stability analysis of a constrained landslide the landslide has nowhere to go and its downhill movement is slowing in time which intuitively implies its long term stability however exactly because the landslide is slowing the shear strength on the sliding surface may decrease leading to increase in compressive stresses at the landslide foot and ultimately to a failure the proposed long term stability analysis of such a landslide is based on an inverse analysis which allows for the safety factor to be determined solely by curve fitting the observed displacement data for a safety factor lower than 1 the time of failure can be predicted using additional earth pressure measurements in the sliding layer the proposed procedure is illustrated using the observation data from the brattas st moritz landslide

field observations rheological testing and numerical modelling of a debris flow event debris flows generated from landslides are common processes and represent a severe hazard in mountain regions due to their high mobility and impact energy we investigate the dynamics and the rheological properties of a 90 000 m3 debris flow event triggered by a rapid regressive landslide with high water content field evidence revealed a maximum flow depth of 7 8 m with an estimated peak discharge of 350 400 m3 s 1 depositional evidence and grain size distribution of the debris pose the debris flow in an intermediate condition between the fluid mud and grain flow behaviour the debris flow material has silt clay content up to 15 per cent the rheological behaviour of the finer matrix was directly assessed with the ball measuring system the measurements performed on two samples at 45 63 per cent in sediment concentration by volume gave values of 3 5 577 pa for the yield strength and 0 6 27 9 pa s for the viscosity based on field evidence we have empirically estimated the yield strength and viscosity ranging between 4000 200 pa and 108 134 pa s respectively we used the flo 2d code to replicate the debris flow event we applied the model with rheological properties estimated by means of direct measurements and back analyses the results of these models show that the rheological behaviour of a debris flow mass containing coarse clasts can not be assessed solely on the contribution of the finer matrix and thus neglecting the effects of direct grain contacts for debris flows composed by a significant number of coarse clasts a back analysis estimation of the rheological parameters is necessary to replicate satisfactorily the depositional extent of debris flows in these cases the back estimated coefficients do not adequately describe the rheological properties of the debris flow copyright 2006 john wiley sons ltd

landslide kinematics and their potential controls from hourly to decadal timescales insights from integrating ground based insar measurements with structural maps and long term monitoring data abstract knowledge of kinematics is rudimentary for understanding landslide controls and is increasingly valuable with greater spatiotemporal coverage however characterizing landslide wide kinematics is rare especially at broadly ranging timescales we used highly detailed kinematic data obtained using photogrammetry and field mapping during the 1980s and 1990s and our 4 3 day ground based insar survey during 2010 to study kinematics of the large persistently moving slumgullion landslide the landslide was segregated into 11 kinematic elements using the 1980s 1990s data and the insar survey revealed most of these elements within a few hours averages of insar derived displacement point measures within each element agreed well with higher quality in situ observations averaging was deemed necessary because adverse look angles for the radar coupled with tree cover on the landslide introduced error in the insar results we found that the landslide moved during 2010 at about half its 1985 1990 speed but slowing was most pronounced at the landslide head gradually decreased precipitation and increased temperature between the periods likely resulted in lower groundwater levels and consequent slowing of the landslide we used gps survey results and limit equilibrium modeling to analyze changing stability of the landslide head from observed thinning and found that its stability increased between the two periods which would result in its slowing and the consequent slowing of the entire landslide additionally insar results suggested movement of kinematic element boundaries in the head region and our field mapping verified that they moved and changed character likely because of the long term increasing head stability on an hourly basis insar results were near error bounds but suggested landslide acceleration in response to seemingly negligible rainfall pore pressure diffusion modeling suggested that rainfall infiltration affected frictional strength only to shallow depths along the landslide s marginal faults highlighting their importance in controlling landslide stability hourly results also suggested that motion propagated along the 3 9 km length of the active landslide even following sub millimeter displacements while strengthening of landslide shear boundaries during faster movement was likely critical in regulating the landslide s motion hence detailed kinematic characterizations obtained from traditional and emerging approaches helped to reveal that mechanisms controlling landslide movement and evolution over decades also are critical to sub millimeter movement on a nearly continuous basis

contraction driven shear failure in compacting uncemented sediments shear failure in sediments is universally linked with active boundary conditions such as those imposed by tectonic stresses under conditions of no lateral strain and in the absence of tectonic stress soil mechanics theories predict a simple one dimensional compaction in which sediment particles displace vertically without shear failure during pressure diffusion conflicting with this theory shear failure planes are often found in sediments that formed under near horizontal burial conditions we investigated the effect of particle scale volume contraction as a potential cause of shear failure in uncemented particulate materials and found that loss of particle volume under confined conditions no external loading resulted in pronounced lateral stress reduction often reaching coulomb frictional failure conditions shear strain localization was analytically predicted and modeled numerically due entirely to volume loss at the grain scale we define this mode of internally driven shear failure as contractile to distinguish it from that caused by external loading and show that it can explain many natural fracture systems without invoking regional tectonics

creep properties of clastic soil in a reactivated slow moving landslide in the three gorges reservoir region china abstract most slow moving landslides in the three gorges reservoir tgr region of china are characterized by pre existing shear surfaces the large deformation within the shear zones usually gives rise to clastic soil formation the creep properties have large influence on the kinematic feature of landslides in this paper we report an in situ direct shear creep test carried out in the shear zone of a reactivated slow moving landslide in the tgr region correspondingly some laboratory ring shear creep tests are carried out to interpret the movement pattern of this landslide the shear zone soil exhibits similar non attenuating creep responses in both the in situ direct shear and laboratory ring shear creep tests at the same stress level however the in situ direct shear creep test yields a larger rate of creep displacement due to shearing along the landslide direction in the ring shear creep tests at the prepeak stage the critical creep stress that triggers creep failure is slightly lower than the peak shear strength but much larger than the residual strength at the postfailure stage the critical creep stress of the shear zone soil is equal to the residual shear strength the rate dependent residual shear strength may account for the stepwise movement pattern of the landslide

landslide amplification by liquefaction of runout path material after the 2008 wenchuan m 8 0 earthquake china here we propose that an earthquake can trigger the failure of a landslide mass while simultaneously triggering liquefaction of runout path materials before the arrival of the landslide mass thus greatly increasing the size and mobility of an overriding landslide during the 2008 wenchuan earthquake about 60 000 landslides were triggered directly resulting in about 20 000 casualties while these landslides mainly originated from steep slopes some landslides with high mobility formed in colluvial valley deposits among these the most catastrophic was the xiejiadian landslide in pengzhou city which traveled hundreds of meters before coming to rest through field investigation and laboratory testing we conclude that this landslide primarily formed from colluvial deposits in the valley and secondarily from failure of slopes in granitic rock located uphill much of the granitic slope failure was deposited in the upper part of the travel path near the slide head the remainder was dispersed throughout the main landslide deposit superposition of deposits at the landslide toe indicates that landslide debris derived from colluvial soil was deposited first the deposits at the landslide toe displayed flow characteristics such as fine materials comprising basal layers and large boulders covering the deposit surface we hypothesize that the main part of the landslide resulted from seismogenic liquefaction of valley colluvium rather than from liquefaction potentially caused by undrained loading from the granitic slope failures impacting the colluvium to examine the likelihood that seismogenic liquefaction occurred we took samples from different areas of the landslide deposit and performed undrained cyclic shear tests on them in the laboratory the results showed that the sandy soils that comprise most of the deposit are highly liquefiable under seismic loading therefore we conclude that liquefaction of the colluvium in the valley during the earthquake was the main reason for this rapid 46 m s long runout 1 7 km landslide

a possible causal relationship between creep and sliding on rwaza hill southern rwanda stability calculations on a strongly creeping 28o slope on rwaza hill in southern rwanda reveal an apparent contradiction terracette formation within the kaolinitic soil mantle should only be possible during hydrological conditions of high phreatic surfaces for which the entire soil mantle should already have slid down in a translational sliding movement this apparent contradiction can only be explained if it is accepted that the soil shear resistance can fall temporarily below the residual soil shear strength a creep experiment confirms the theoretical possibility of this hypothesis furthermore the configuration of the sliding surfaces in the field consisting in fact of lenses of crumbled earth shows close affinities with the pattern of potential ruptures in a creeping soil as provided by rheological theory these data strongly suggest that on natural slopes creep should be the ultimate soil mechanical resason for sudden failures

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

implications for timing of andean uplift from thermal resetting of radiation damaged zircon in the cordillera huayhuash northern peru abstract the cordillera huayhuash is a north south oriented range along the drainage divide of the northern peruvian andes the range has high topography with peaks in excess of 5500 m and the second highest peak in peru nevados yerupaja 6617 m bedrock is dominated by folded mesozoic miogeoclinal rocks unconformably overlain by mid tertiary volcanics intruded by late tertiary granitic rocks and silicic dikes zircon fission track zft and u th he zhe dating of zircons along a west east transect elucidates the thermal evolution of exhumed and uplifted rocks the stability of fission tracks in zircons is a function of single grain radiation damage in samples with grain to grain variability in radiation damage resetting results in variable resetting and multiple age populations low retentive zircons lrzs which have a partly disordered crystalline structure have significant radiation damage and a low temperature of annealing ca 180 200 c high retentive zircons hrzs which are nearly cry

insar based detection method for mapping and monitoring slow moving landslides in remote regions with steep and mountainous terrain an application to nepal abstract mapping and monitoring landslides in remote areas with steep and mountainous terrain is logistically challenging expensive and time consuming yet in order to mitigate hazards and prevent loss of life in these areas and to better understand landslide processes high resolution measurements of landslide activity are necessary satellite based synthetic aperture radar interferometry insar provides millimeter scale measurements of ground surface deformation that can be used to identify and monitor landslides in remote areas where ground based monitoring techniques are not feasible here we present a novel insar deformation detection approach which uses double difference time series with local and regional spatial filters and pixel clustering methods to identify and monitor slow moving landslides without making a priori assumptions of the location of landslides we apply our analysis to freely available copernicus sentinel 1 satellite data acquired between 2014 and 2017 centered on the trishuli river drainage basin in nepal we found a minimum of 6 slow moving landslides that all occur within the ranimatta lithologic formation phyllites metasandstones metabasics these landslides have areas ranging from 0 39 to 1 66 km2 and long term dry season displacement rates ranging from 2 1 to 8 8 cm yr due to periods of low coherence during the monsoon season june september each year and following the 25 april 2015 mw7 8 gorkha earthquake our time series analysis is limited to the 2014 2015 and 2016 2017 dry seasons september may we found that each of the landslides displayed slightly higher rates during the 2014 period likely as a result of higher cumulative rainfall that fell during the 2014 monsoon season although we do not have high quality insar data to show the landslide evolution directly following the gorkha earthquake the similar rates of movement before 2014 2015 and after 2016 2017 gorkha suggest the earthquake had negligible long term impact on these landslides our findings highlight the potential for region wide mapping of slow moving landslides using freely available remote sensing data in remote areas such as nepal and future work will benefit from expanding our methodology to other regions around the world

long runout mechanism and landsliding behaviour of large catastrophic landslide triggered by heavy rainfall in guanling guizhou china a large catastrophic landslide was triggered by a heavy rainfall on 28 june 2010 in guanling guizhou china the landslide buried two villages and killed 99 people along the runout path the lands

a critical evaluation of late tertiary accelerated uplift rates for the eastern cordillera central andes of bolivia abstract many articles have cited a study of apatite and zircon fission track ages from the eastern cordillera of the central andes bolivia as evidence for a marked acceleration of uplift rates over the last 40 m yr however we show that an artifact of the graphical technique used to interpret the data namely the common variable problem drives the apparent increase in order to determine what can be inferred about exhumation history from the data we developed a simple quantitative forward model to calculate the coupled apatite and zircon age profiles as a function of height and then used markov chain monte carlo techniques to estimate the family of solutions that provide reasonable fits to the data this model improves on linear regression analysis of elevation age plots which treats apatite and zircon data as independent systems results suggest that both exponential or step function velocity models fit the data well we prefer the exponential model however because it appears to be more consiste

the timing and magnitude of mountain glaciation in the tropical andes the andes of ecuador peru and bolivia host the majority of the world s tropical glaciers in the tropical andes glaciers accumulate during the wet season austral summer and ablate year round precipitation is delivered mainly by easterlies and decreases both n s and e w chronological control for the timing of glacial advances in the tropical andes varies in ecuador six to seven advances have been identified dating is based on radiocarbon ages timing of the local last glacial maximum lgm and the existence of younger dryas advances remain controversial in peru local variability in glaciation patterns is apparent surface exposure dating in the cordillera blanca and junin plain suggests that the local lgm may have been early 30 ka although uncertainties in age calculations remain the local lgm was followed by a lateglacial readvance stillstand and preceded by larger glaciations in contrast preliminary data from an intervening massif indicate that the largest moraines are lateglacial chronologies from bolivia also suggest local variability in leeward milluni and san francisco valleys local lgm moraines descend to 4300 m above sea level a s l whereas in windward zongo valley lateglacial moraines reach 3400 m a s l atlantic and pacific sea surface temperatures el nino southern oscillation and insolation changes all likely play roles in mediating tropical andean glacial cycles copyright 2008 john wiley sons ltd additional supporting information may be found in the online version of this article

an experimental study to characterize the initiation of the seismic induced tsaoling rock avalanche abstract the tsaoling rock avalanche which had a sliding volume of 120 million m3 and a maximum thickness of 170 m was triggered by the chi chi earthquake in 1999 however the initiation mechanism has not been well understood because different friction models have been proposed to describe the triggering process using the newmark sliding model and numerical simulations in this study a new dynamic ring shear test with a maximum normal stress higher than 3400 kpa is applied as an alternative approach to investigate the initiation of the seismic induced rock avalanche along the wet sliding surface at the interface of the cholan sandstone and consolidated remold shale experimental results verify that the seismic stresses at the wet sliding surface touch the failure surface and generate significant cumulative shear displacements additionally the shear surface should have non linear failure criteria rather than the well known linear mohr coulomb failure criteria with a constant friction angle furthermore the initiation time of the tsaoling rock avalanche obtained from the dynamic ring shear test is strongly correlated with the available seismic signal interpretations and the interviews of witnesses who travelled with the sliding mass this is the first experiment clarifying the co seismic behavior of the sliding surface and the initiation of the tsaoling landslide during the chi chi earthquake additionally from the development of the ring shear test the integrations of high normal stress the wet sandstone shale interface and the dynamic test with seismic loadings greatly extend the use of ring shear tests to rock avalanches

temperature dependent residual shear strength characteristics of smectite bearing landslide soils this paper presents experimental investigations regarding the effect of temperature on the residual strength of landslide soils at slow to moderate shearing velocities we performed ring shear tests on 23 soil samples at temperatures of 6 29 c the test results show that the shear strength of smectite rich soils decreased when temperatures were relatively low these positive temperature effects strength losses at lower temperatures observed for smectite bearing soils are typical under relatively slow shearing rates in contrast under relatively high shearing rates strength was gained as temperature decreased as rheological properties of smectite suspensions are sensitive to environmental factors such as temperature ph and dissolved ions we inferred that temperature dependent residual strengths of smectitic soils are also attributed to their specific rheological properties visual and sem observations of ca bentonite suggest that slickensided shear surfaces at slow shearing rates are very shiny and smooth whereas those at moderate shearing rates are not glossy and are slightly turbulent indicating that platy smectite particles are strongly orientated at slow velocities the positive temperature effect is probably due to temperature dependent micro friction that is mobilized in the parallel directions of the sheet structure of hydrous smectite particles on the contrary the influence of micro viscous resistance which appears in the vertical directions of the lamination is assumed to increase at faster velocities our results imply that if slip surface soils contain high fractions of smectite decreases in ground temperature can lead to lowered shear resistance of the slip surface and trigger slow landslide movement

residual strength of clays in landslides folded strata and the laboratory the post peak drop in drained shear strength of an overconsolidated clay may be considered as taking place in two stages first at relatively small displacements the strength decreases to the fully softened or critical state value owing to an increase in water content dilatancy second after much larger displacements the strength falls to the residual value owing to reorientation of platy clay minerals parallel to the direction of shearing if the clay fraction is less than about 25 the second stage scarcely comes into operation the clay behaves much like a sand or silt with angles of residual shearing resistance typically greater than 20 degrees conversely when the clay fraction is about 50 residual strength is controlled almost entirely by sliding friction of the clay minerals and further increase in clay fraction has little effect the angles of residual shearing resistance of the three most commonly occurring clay minerals are approximately 15 degrees for kaolinite 10 degrees for illite or clay mica and 5 degrees for montmorillonite when the clay fraction lies between 25 and 50 there is a transitional type of behaviour residual strength being dependent on the percentage of clay particles as well as on their nature the post peak drop in strength of a normally consolidated clay is due only to particle reorientation measurements of strength on natural shear surfaces agree within practical limits of variation with values derived from back analysis of reactivated landslides this field residual strength can be recovered by multiple reversal shear box tests on cut plane samples but in high clay fraction materials it is typically somewhat higher than the strength measured in ring shear tests residual strength is little affected by variation in the slow rates of displacement encountered in reactivated landslides and in the usual laboratory tests but at rates faster than about 100 mm min qualitative changes take place in the pattern of behaviour a substantial gain in strength is followed with increasing displacement by a fall to a minimum value in clays and low clay fraction silts this minimum is not less than the slow or static residual but in clayey silts with clay fractions around 15 25 according to tests currently in progress the minimum can be as low as one half of the static value author trrl

latitudinal variation of denudation in the evolution of the bolivian andes latitudinal gradients in topography relief climate and deformation have been used to suggest that climate driven erosion has exerted a first order control on the development of the central andes we synthesize the spatial and temporal variations in denudation across the eastern bolivian andes 14 22 s from new and existing estimates to test whether physical evidence exists to support the hypothesis that erosion influences thrust belt evolution basin morphometry channel network indices climate and longitudinal river profiles indicate a northward increase in relative relief fluvial incision and denudation short term denudation rate averages from landslide mapping and sediment flux data range from 1 to 9 mm yr in the north compared to 0 3 to 0 4 mm yr in the south long term denudation rate estimates from thermochronology cosmogenic radionuclides foreland basin sediment volumes stra tigraphy paleoerosion surface degradation and balanced cross sections range from 0 04 to 1 6 mm yr with rates up to more than twice as fast in the north when comparing estimates from the same method the shorter term denudation rates exhibit the greatest variance our denudation synthesis shows that an along strike disparity in denudation greater in the north has existed throughout the holocene and perhaps existed since as early as the late miocene our denudation synthesis also suggests that the disparity and denudation rates have increased to the present correlations between the thrust belt geology geometry geomorphology climate and kinematics of the orogenic wedge provides a case study in observing the regional scale interactions between uplift climate and erosion we conclude that the denudation history uplift history and tectonic geomorphic correlations suggest that models of the evolution of the bolivian andes should incorporate a latitudinal erosion gradient for the last 10 kyrs to perhaps 10 myrs

erosion and tectonics at the margins of continental plateaus the topography across the eastern margin of the central andean plateau north of 18 s beni region bears a strong resemblance to the topography of the southern margin of the tibetan plateau nepal himalaya with both regions featuring a steep frontal slope and high peaks at the plateau edge in contrast the topography of the eastern margin of the central andean plateau south of 18 s pilcomayo region tapers toward the foreland more gently and has no line of high peaks at the margin both the himalayan and the beni regions have been the sites for large amounts of denudation and in both regions geologic evidence suggests that erosion has been sufficiently vigorous for the physiographic plateau margin to have retreated toward the plateau interior during the neogene we hypothesize that the steep frontal slope and high peaks of the beni region and himalayan front largely reflect the high orographic precipitation and high erosion rates occurring in these regions and that the more gentle topography of the semiarid pilcomayo region reflects a tectonic landform only slightly modified by erosion we propose that orographic precipitation impinging on a plateau margin will generally tend to drop moisture low on the slope eroding back the plateau while enhancing or maintaining the steep long wavelength slope a numerical model coupling orographic precipitation erosion and tectonic uplift demonstrates the plausibility of this hypothesis the erosional efflux in both the beni and nepal himalaya have been considerable and simple mass balance calculations for the himalaya suggest that during the neogene the erosional mass efflux has generally outpaced the tectonic mass influx this contrasts with the apparent prior domination of tectonic influx and may reflect a decrease in the rate of tectonic addition during the same period and or increased late cenozoic erosion rates

objective oriented multistage ring shear test for shear strength of landslide soil ring shear tests were conducted on five samples of different nature with a modified imperial college type ring shear machine the three different testing methods used 1 individual sample testing for each normal stress 2 increasing load multistage ring shear test and 3 reducing load multistage ring shear test all showed similar effective residual internal friction angle for the samples irrespective of testing method however effective residual shear intercept was different according to the testing methodology the internal friction angle did not vary particularly after the first minimum point in the stress displacement curve although the residual shear intercept decreased with increase in the displacement the thickness of the shearing zone increased along with the displacement the remolded peak shear strength for saturated conditions at field dry density varied with the consolidation history measurement of remolded peak shear strength was possible in a single sample using the increasing load multistage ring shear test at normal consolidation the equilibrium water content of the sample after the ring shear test was nearly equal to the plastic limit

in situ surface shear strength as affected by soil characteristics and land use in calcareous soils of central iran abstract soil surface shear strength is an important input parameter in the process based soil erosion models but its direct measurement at the watershed scale is difficult time consuming and costly this study was conducted to predict in situ shear strength of the soil surface using multiple linear regression mlr the land use impact on the surface shear strength was examined as well a direct shear box was constructed to measure in situ shear strength cohesion c and angle of internal friction of the soil surface in the semirom region located in isfahan province central iran the shear device consisted of a circular shear box with 10 cm internal diameter and height of 1 cm an s shaped load cell for measuring horizontal shear stress and an electric motor for applying the shear stress the normal stress acting on the failure surface was adjusted by adding weights on the shear box soil surface shear strength was determined using the shear box at 100 locations under three land use systems of grassland irrigated farming and dryland farming soil particle size distribution clay silt sand and fine clay organic matter content om carbonate content bulk density and gravel content were determined as predictors of the surface shear strength normalized difference vegetation index ndvi was also calculated using satellite images the mlr was employed to predict the shear strength i e c and using two groups of input variables i easily available soil properties pedotransfer functions ptfs and ii easily available soil properties and ndvi soil spatial prediction functions sspfs a strong negative correlation r 0 72 p c and in the studied area positive correlation r 0 41 p c and fine clay content the c was negatively correlated r 0 31 p r 0 37 p r 0 47 p and gravel content indicating the roughness effect of coarse particles on frictional shear strength the results also showed that ndvi is an important factor indirectly explaining the variability of both c and in the studied soils the land use effect on the soil properties was investigated using the lsd 0 05 test the means of somehow follow the variation of gravel content among the land uses the highest means of clay and fine clay contents and c and the lowest means of sand and gravel contents and were observed in dryland farming the c has the same trend as did clay content irrigated farming with the highest mean of sand content and lowest mean of clay content had the lowest mean of c the c means were significantly different between irrigated farming and dryland farming prediction models of in situ shear strength derived using both soil properties and ndvi as predictors sspfs were more accurate than those derived using only soil properties ptfs

ore lead isotope pattern from the iglesiente sulcis area sw sardinia and the problem of remobilization of metals in sw sardinia syngenetic to syndiagenetic pb zn ores occur in cambrian carbonates along the unconformity between the cambrian and ordovician in permo triassic karsts and in vein type deposits related to late hercynian granites which also contact metamorphosed some cambrian deposits in all types of deposits the leadisotope ratios show similarly high 238u 204pb and high w 232th 204pb values indicating a crustal origin for the lead most of the cambrian ores contain isotopically similar or identical leads whereas in the younger deposits the isotope ratios vary and suggest that especially the lead of permo triassic ores may consist to a large extent of remobilized cambrian possibly also ordovician ore lead plus a hercynian component

excess pore pressure and grain crushing of sands by means of undrained and naturally drained ring shear tests an investigation of excess pore pressure generation of a weathered granitic sand taken from the source area of a typical landslide caused as a result of liquefaction and a fine silica sand was conducted in which grain crushing within the shear zone of ring shear test specimens was examined as the key phenomenon of rapid long runout motion of landslides in order to investigate and explain the low average apparent friction angle mobilized in a liquidized landslide speed controlled ring shear tests were conducted under undrained conditions on weathered granitic sand specimens formed under a wide range of initial void ratios it was revealed that very small steady state shear resistances were obtained irrespective of the initial void ratios which can explain the low average apparent friction angle in addition two series of ring shear tests on weathered granitic and fine silica sands were conducted under naturally drained conditions by keeping the upper drain valve of the shear box open during the tests the first series of tests was performed under differing total normal stresses but at the same shear speed and the second series was conducted at differing shear speeds but under the same total normal stress in order to investigate and analyze excess pore pressure generation and dissipation within the shear zone that is associated with grain crushing permeability analyses were conducted by passing water through the sample box of the ring shear test apparatus before and after shearing in addition grain size distribution analyses of samples taken from the shear zone after shearing were carried out for the weathered granitic sand samples a significant change in bulk permeability and large amount of grain crushing were observed in these tests on the above soil a considerable reduction of shear resistance which increased proportionally to the total normal stress and shear speed were obtained it was observed that due to grain crushing finer grains that lowered the permeability of the soil in the shear zone were formed it is likely that the decrease in permeability facilitated the generation of high excess pore pressures by reducing the pore pressure dissipation rate from the shear zone thus flow behaviour was exhibited even under naturally drained conditions

moisture content effect on the creep behavior of loess for the catastrophic baqiao landslide abstract understanding the creeping behavior of loess is of great importance as large scale loess landslides are closely related with creep behavior at present it is still challenging to predict and estimate the long term stability of such landslides this is in a large degree due to the poor understanding of moisture control on creep behavior of loess the purpose of this study is to decipher the loess creep behavior under various moisture contents mcs using loess specimens obtained from baqiao landslide xi an of china using multi loading triaxial creep tests under different mcs of 9 12 15 18 and 21 based on the laboratory test results a series of relationships between the creep rate at the steady state creep stage and the initial strain and initial shear modulus are revealed meanwhile a method for obtaining the long term strength of loess specimens namely the steady state creep rate slope method scrsm is proposed scrsm resolves the issue in several conventional methods such as the isochronous stress strain curve method the tangent method of steady creep rate when mcs are of concern such an improvement is primarily due to a better way of finding the inflection point of the steady state rate it is found that scrsm is robust and accurate to determine the long term strength of loess specimens furthermore we propose a modified burgers model with a newly introduced nonlinear parameter n to overcome deficiencies of conventional creep models this modified burgers model is flexible to fit the creep test curves of loess and can describe the curves at the accelerated creep stage more accurately lastly the main factors triggering the baqiao landslide is analyzed considering stratum lithology rainfall and excavation in general this study provides a basis for understanding the evolutional process of loess landslides as well as guidelines for prevention controlling and prediction of loess landslides

cenozoic forearc basin sediments in southern peru 15 18 s stratigraphic and heavy mineral constraints for eocene to miocene evolution of the central andes abstract a large sedimentary forearc basin developed in cenozoic times between the present day coastal cordillera and the western cordillera of the central andes called moquegua basin in southern peru the basin is filled by moquegua group deposits 50 to 4 ma comprising mostly siliciclastic mudstones sandstones and conglomerates as well as volcanic intercalations several facies changes both along orogenic strike and through time are described and have led to subdivision into four sedimentary units moquegua a b c and d in this paper we present a refined stratigraphic scheme of the moquegua group combined with the first provenance analysis of the moquegua basin based on i semi quantitative analysis of heavy mineral abundance ii electron microprobe emp and laser ablation la icp ms analyses of single detrital amphibole and fe ti oxide grains and iii comparative analysis of the different potential source rocks to clearly identify the most likely sources results allow us to reconstruct sediment provenance and to relate changes of the erosion sedimentation system in the moquegua basin to the evolution of the andean orogen at 50 to 40 ma the moquegua basin was close to sea level and fed by low energy rivers transporting mainly metamorphic basement and jurassic cretaceous sedimentary detritus from local and distal sources the latter might be as far as the present eastern cordillera from 35 ma on the distal sediment sources were cut off by the uplift of the altiplano and eastern cordillera leading to higher energy fluvial systems and increasing importance of local sources especially the relevant volcanic arcs from 25 ma on volcanic arc rocks became the predominant sources for moquegua group sediments the 10 ma time lag observed between the onset of uplift induced facies and provenance changes at 35 ma and the onset of intense magmatic activity at 25 ma suggests that magmatic addition was not the main driver for crustal thickening and uplift in the central andes during latest eocene to oligocene time

from source to sink preserving the cosmogenic 10be derived denudation rate signal of the bolivian andes in sediment of the beni and mamore foreland basins abstract the denudation rate signal of the bolivian andes as measured by cosmogenic 10 be in sediment is preserved in the floodplain of adjacent foreland basins even though these basins store the sediment for thousands of years this conclusion is drawn from comparing published andean source area denudation rates with new cosmogenic 10 be data as measured in the floodplains of the large beni and mamore basins for the entire beni basin including the sediment producing andes and the vast flooded plains of the foreland the cosmogenic nuclide derived denudation rate is 0 45 0 06 mm yr while that of the mamore basin is 0 55 0 19 mm yr by comparison the respective andean source areas erode at averaged rates of 0 37 0 06 mm yr upper beni and at 0 56 0 09 mm yr upper mamore we notice a decrease in variability of denudation rate with increasing spatial scale as small scale processes are averaged out sediment mixing within the floodplain damps scatter of nuclide derived denudation rates picked up in the source area on the temporal scale a remarkable agreement between cosmogenic nuclide derived rates averaging over a few kiloyears with those from fission track dating averaging over millions of years seems to suggest that cosmogenic nuclide derived denudation rates capture the long term erosional characteristics of the mountain belt the sum of these observations suggests that any sample collected along a river traversing a floodplain will yield the denudation rate of the source area this finding opens the unique possibility of constraining cosmogenic nuclide derived paleo sediment budgets for these large basins as the long term spatially averaged denudation rate signal of the sediment producing area is preserved in sedimentary archives

spatially variable exhumation rates in orogenic belts an andean example abstract the cordillera real of the bolivian andes is a large tectonically active mountain range that dominates sediment influx into the amazon basin but rates of exhumation in the orogen are poorly known we present 20 new apatite fission track ages from two valleys in the cordillera real to constrain patterns of mountain range exhumation over 106 107 yr we interpret these and previously published data from a third valley using a 2 d thermal model that accounts for topographic and advective influences on measured cooling ages exhumation rates in the cordillera real are 0 2 0 6 mm yr comparable to rates in parts of denali the washington cascades the olympic mountains and the european alps and an order of magnitude slower than rates in taiwan nanga parbat the greater himalaya of nepal and the southern alps of new zealand three to fourfold cooling age variations in the cordillera real imply at least twofold exhumation rate variations within and between valleys over distances of only tens of ki

problems in predicting the mobility of slow moving landslides abstract this paper discusses problems in predicting the mobility of slow moving landslides three case studies are presented here where research has been carried out by the utrecht university the la valette landslide complex in the french alps the la mure landslide in the french pre alps near grenoble and the hau landslide in switzerland to predict field velocities of these slow moving landslides the viscosity parameters of the material of these landslides were determined by strain controlled tests in a ring shear apparatus based on bishop s design at utrecht university the viscosity parameters from the laboratory proved to be 10 to 1000 times lower than viscosities obtained from back analyses on the observed velocities in the field this discrepancy may be explained by the development of negative pore pressures when the plastic material slides over a rigid wavy slip surface and or by convergent flow effects the associated gain in strength results in a higher apparent viscosity a more detailed analysis is made for the movements of the la valette landslide observed velocities at the la valette landslide are difficult to describe by one parameter set as the response to a change in groundwater level is not the same during a rise or fall in the piezometric level this deviation may be explained by rapid changes in total stresses and consequently changes in pore pressure under partly undrained conditions the emerging hysteresis with local and temporal variations in pore pressure makes it difficult to predict in detail the moving pattern of landslides

shear rate dependent behavior of clayey bimaterial interfaces at landslide stress levels the behavior of reactivated and first failure landslides after large displacements is controlled by the available shear resistance in a shear zone and or along slip surfaces such as a soil bedrock interface among the factors influencing the resistance parameter the dependence on the shear rate can trigger catastrophic evolution rate weakening or exert a slow down feedback rate strengthening upon stress perturbation we present ring shear test results performed under various normal stresses and shear rates on clayey soils from a landslide shear zone on its parent lithology and other lithologies and on clay rock interface samples we find that depending on the materials in contact the normal stress and the stress history the shear rate dependent behaviors differ we discuss possible models and underlying mechanisms for the time dependent behavior of landslides in clay soils

landscape analysis and the search for geomorphic unity geomorphology has been an integral part of geological science since the inception of the geological society of america even though different investigative goals have existed continuously in the discipline the dichotomy of purpose began with the vastly different perception of landscape analysis embraced by william morris davis and g k gilbert historical and physical geomorphic studies have always been conducted simultaneously but one of these research activities has dominated the field at any given time during the first half of this century most geomorphic work was devoted to the interpretation of long term evolutionary history of regional landscapes in the past four decades however research has concentrated on the study of geomorphic processes this revised direction placed greater emphasis on the physical component of geomorphology and provided a more complete understanding of the time factor in landscape analysis historical geomorphology is now less concerned with theories of cyclic time landscape development and more involved in determining the time and sequence of shorter episodes of geomorphic disequilibrium caused by tectonism and or climate change the tenor of future research in surficial geology will require input from both physical and historical geomorphology and therefore a greater unity of purpose among geomorphologists can be expected geomorphologists will have the opportunity to provide geologists and engineers with useful data about major scientific and technical problems related to plate tectonic theory interpretation of the stratigraphic record and prediction of landform stability for environmental planning

study of preexisting shear surfaces of reactivated landslides from a strength recovery perspective abstract residual shear strength is generally considered in the design of preventive measures for slopes consisting of preexisting shear surfaces of large scale landslides recent research suggests that the preexisting shear surface of a reactivated landslide can regain strength with the passage of time which might also be considered in designing the slope stability measures in this study three reactivated landslide soils were tested in a ring shear apparatus for the discontinued shear periods of 1 3 7 15 and 30 days with the following main objectives i to understand the strength recovery behavior of landslide soils in a residual state of shear after as long as 30 days of discontinued shear ii to understand the comparative pattern of strength recovery in highly plastic and less plastic soils and iii to understand the mechanism involved in strength recovery at a residual state of shear the results indicate that recovered strength measured in the laboratory is hardly noticeable after a rest period of 3 days but recovered strength is lost after a small shear displacement this paper primarily focuses on the effect of strength recovery from residual strength on preexisting shear surface soils and the mechanisms behind it

residual shear strength variability as a primary control on movement of landslides reactivated by earthquake induced ground motion implications for coastal oregon u s most large seismogenic landslides are reactivations of preexisting landslides with basal shear zones in the residual strength condition residual shear strength often varies during rapid displacement but the response of residual shear zones to seismic loading is largely unknown we used a ring shear apparatus to perform simulated seismic loading tests constant displacement rate tests and tests during which shear stress was gradually varied on specimens from two landslides to improve understanding of coseismic landslide reactivation and to identify shear strength models valid for slow gravitational failure through rapid coseismic failure the landslides we studied represent many along the oregon u s coast seismic loading tests resulted in 1 catastrophic failure involving unbounded displacement when stresses represented those for the existing landslides and 2 limited to unbounded displacement when stresses represented those for hypothetical dormant landslides suggesting that coseismic landslide reactivation may be significant during future great earthquakes occurring near the oregon coast constant displacement rate tests indicated that shear strength decreased exponentially during the first few decimeters of displacement but increased logarithmically with increasing displacement rate when sheared at 0 001 cm s 1 or greater dynamic shear resistance estimated from shear strength models correlated well with stresses observed during seismic loading tests indicating that displacement rate and amount primarily controlled failure characteristics we developed a stress based approach to estimate coseismic landslide displacement that utilizes the variable shear strength model the approach produced results that compared favorably to observations made during seismic loading tests indicating its utility for application to landslides

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

some uncertainties in the derivation of rates of denudation from thermochronologic data low temperature thermochronology such as that provided by apatite fission track analysis provides a valuable means of establishing the timing of major denudational events and associated rates of denudation over geological time scales of 106 108 ma care must be taken however in deriving denudation rates from the crustal cooling histories documented by thermochronologic techniques especially in rapidly eroding terrains since in such cases apparent denudation rates derived from thermochronologic data will usually overestimate true rates if the advective effect of denudation is not included this is likely to be resolvable where the rate of denudation exceeds 300 m ma 1 and when the depth of denudation occurring at these rates exceeds several kilometres prior to the sample cooling below the appropriate closure temperature because the time at which a sample cools below a particular closure temperature is relatively insensitive to advection the initiation of denudation can be accurately established even given uncertainties in the estimation of depths and rates of denudation where thermal events originate from a source within or below the lower crust the cooling through denudation will dominate the low temperature history of the shallow crust if denudation occurs coevally with the subsurface heating 1997 by john wiley sons ltd

widespread initiation reactivation and acceleration of landslides in the northern california coast ranges due to extreme rainfall episodically to continuously active slow moving landslides are driven by precipitation climate change which is altering both the frequency and magnitude of precipitation worldwide is therefore predicted to have a major impact on landslides here we examine the behavior of hundreds of slow moving landslides in northern california in response to large changes in annual precipitation that occurred between 2016 and 2018 we quantify the landslide displacement using repeat pass radar interferometry and pixel offset tracking techniques on a novel data set from the airborne nasa jpl uninhabited aerial vehicle synthetic aperture radar we found that 312 landslides were moving due to extreme rainfall during 2017 compared to 119 during 2016 which was the final year of a historic multiyear drought however with a return to below to average rainfall in 2018 only 146 landslides remained in motion the increased number of landslides during 2017 was primarily accommodated by landslides that were smaller than the landslides that remained active between 2016 and 2018 furthermore by examining a subset of 51 landslides we found that 49 had increased velocities during 2017 when compared to 2016 our results show that slow moving landslides are sensitive to large changes in annual precipitation particularly the smaller and thinner landslides that likely experience larger basal pore water pressure changes based on climate model predictions for the next century in california which include increases in average annual precipitation and increases in the frequency of dry to wet extremes we hypothesize that there will be an overall increase in landslide activity

displacement field in contraction driven faults we investigate the distribution of strain and deformation in the host sediment that arises once a contraction driven shear fault has localized and propagated under a zero lateral strain condition numerical modeling of displacement distributions compares well with those measured using 3d seismic data the parameters that determine the displacement field for a single normal fault embedded in sediments are fault height overburden effective stress stiffness and residual friction angle or post peak strength proximity to the free boundary biases the displacement pattern which becomes asymmetric although the measured displacements and numerical predictions are similar the measured magnitude requires pronounced low stiffness of the sediment as well as low post peak shear strength this requirement suggests that sediments hosting contraction driven shear faults most likely have high porosity and high clay fraction and have undergone diagenetic reactions involving significant mineral dissolution the diagenetic evolution of the sediment and its current composition may explain the global scaling relationship between the measured displacement and fault height for polygonal fault systems

origin of the high plateau in the central andes bolivia south america the bolivian altiplano in the central andes of south america is part of the second largest high plateau on earth it is an elongate region of subdued relief 1 2 105 km2 and 4 km above sea level bounded by the eastern cordillera and volcanic arc western cordillera here the crust is up to 75 km thick we describe the cenozoic geological evolution of this region using a revised chronostratigraphy and an analysis of the crustal and lithospheric structure crustal shortening and magmatic addition and locally sedimentation are the main mechanisms of cenozoic crustal thickening leading to nearly 4 km of surface uplift since the paleocene addition of mafic melts appears to be a first order mechanism of cenozoic crustal growth contributing 40 of the crustal thickening beneath the volcanic arc removal of the basal part of the lithosphere may have caused two episodes of widespread arc and behind arc mafic volcanism at 23 ma and 0 5 ma contributing to the surface uplift the altiplano originated as a sedimentary basin several hundred kilometers wide between the proto western cordillera and a narrow zone of uplift proto eastern cordillera farther east the latter zone formed by inversion of the center of a wide lacustrine or marine cretaceous paleocene basin close to sea level at 45 ma a thickness of 2 4 km of paleogene continental elastics accumulated in the proto altiplano basin subsequently in the oligocene we estimate that this region and the western margin of the eastern cordillera were technically shortened 22 65 km resulting in 9 km of average crustal thickening the altiplano basin was rejuvenated at 25 ma and subsequently flooded with up to 8 km thickness of detritus eroded from the uplifting eastern and western cordilleras between 25 and 5 ma folding and thrusting in the western margin of the eastern cordillera migrated westward into the center of the altiplano basin essentially terminating deposition except in local subbasins and accommodating 13 30 km of shortening and an estimated 7 km of average crustal thickening subsequently there has been strike slip deformation and limited local thrusting 5 km of shortening geomorphological and geochronological evidence for 1 5 2 km of surface uplift of this region since the late miocene suggests 14 km of lower crustal thickening beneath an essentially rigid lid and can be explained by 100 150 km of underthrusting of the brazilian shield and adjacent regions beneath the eastern margin of the central andes the present subdued relief in the altiplano may be a result of ductile flow in the lower crust and sedimentation and erosion in an internal drainage basin

soil creep and convex upward velocity profiles theoretical and experimental investigation of disturbance driven sediment transport on hillslopes the movement of unconsolidated materials near the earth s surface is often driven by disturbances that occur at a range of spatial and temporal scales the nature of these disturbances ranges from highly variable such as tree turnover to periodic and predictable such as frost heave or creep to explore the effect of probabilistic disturbances on surface processes we formulated a granular creep model with analogy to rate process theory rpt used for chemical reactions according to the theory individual particles must be energized to a height greater than adjacent particles in order for grain dilation and transport to occur the height of neighbouring particles which is akin to activation energy in chemical reactions varies with slope angle such that energy barriers get smaller in the downslope direction as slopes steepen when slopes approach the friction limited angle of repose the height of energy barriers approaches zero and grains ow in the absence of disturbance an exponential function is used to describe the probability distribution of particle excitation height although alternative distributions are possible we tested model predictions of granular dynamics in an experimental sandpile in the sandpile acoustic energy serves as the disturbance agent such that grains dilate and shear in response particle velocities are controlled by the frequency of energy pulses that result in grain displacement using tracer particles we observed a convex upward velocity pro le near the surface of the sandpile consistent with predictions of our rpt based velocity model in addition we depth integrated the velocity model to predict how ux rates vary with inclination of the sandpile and observed non linear ux gradient curves consistent with model predictions by varying the acoustic energy level in the experimental sandpile we documented changes in the rate of grain movement similar changes in modelled velocities were achieved by varying the exponent of the particle excitation probability distribution the general agreement between observed and modelled granular behaviour in our simple laboratory sandpile supports the utility of rpt based methods for modelling transport processes e g soil creep frost heave and till deformation thus enabling us to account for the probabilistic nature of disturbances that liberate sediment in natural landscapes copyright 2004 john wiley sons ltd

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

on pore water pressure variations causing slide velocities and accelerations observed in a seasonally active landslide individual block displacements continuously recorded in spring 1987 in a landslide in the french alps are strongly affected by rain and dry spells although a viscous component is present in the sliding mechanism variation of the plastic strength characteristics is necessary to explain the controlled sliding a stick slip movement behaviour and a diurnal variation in slide rate attributed to the diurnal variation in evapotranspiration were recorded the observed numerous accelerations and decelerations of the blocks movements are attributed to small variations in pore pressure these variations are explained and their magnitude is calculated starting from limit equilibrium increases of pore water pressure smaller than 0 1 k pa are sufficient to provoke the maximum recorded acceleration and velocity for a block of 2000 tons in weight

suction and rate dependent behaviour of a shear zone soil from a landslide in a gently inclined mudstone sandstone sequence in the sichuan basin china abstract bedding controlled landslides in alternated mudstone and sandstone beds in cataclinal slopes are common in the sichuan basin and in the three gorges area in china they are characterised by very gentle dip angles of the beds

some fluidized landslides triggered by the 2011 tohoku earthquake mw 9 0 japan abstract the 2011 tohoku earthquake off the pacific coast of japan generated a large tsunami and many landslides resulting in a great number of casualties although almost all casualties resulted from the tsunami some long travel fluidized small scale landslides also killed 13 people after the earthquake we surveyed seven of these catastrophic landslides triggered by the earthquake we found that most of them have nearly identical geological features with slopes consisting of pyroclastic deposits formed at different times and with a palaeosol layer that outcropped in most cases after the landslide above the palaeosol there are layers of pumice and scoria the palaeosol had a natural moisture content of 160 and the pumice and scoria had a moisture content of 145 from field observations we concluded that the sliding surface originated in the very upper part of palaeosol and liquefaction occurred in both layers resulting in the fluidization of displaced landslides to examine the trigger and movement mechanism of these landslides we monitored the ground motion of one landslide area during the many aftershocks and compared the results with records obtained by a national seismic station nearby we inferred that strong seismic motion occurred in the landslide area during the main shock we sampled the palaeosol and pyroclastic deposits and performed undrained static cyclic shear tests on the materials both in a saturated state and at natural moisture content the results indicate that high pore water pressure was generated resulting in decreased shear strength even in samples with the natural moisture content the shear strength of the palaeosol lowered to a very small value with continuous increase of shear rate enabling the high mobility of the displaced landslide materials

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

low angle normal fault lanf zone architecture and permeability features in bedded carbonate from inner northern apennines rapolano terme central italy abstract fault zones have the capacity to be hydraulic conduits within upper crustal levels allowing migration of large volume of fluids through shallow and deeper geological environments low angle normal faults lanfs crosscutting carbonate rocks produce damaged volumes that may have a relevant role in channelling or hosting geothermal fluids therefore deserving of investigation to better predict mining targets deformation along lanfs zones dissecting carbonate successions produces permeable volumes presently exploited in the larderello and monte amiata geothermal areas italy in this paper the architectural and permeability features of an exhumed lanf zone exposed in the northern apennines rapolano terme central italy affecting cretaceous bedded limestone are presented such a fault was not affected by circulation of geothermal fluids but its features could reveal much on the potential impact on fluids migration in the active geothermal areas therefore resulting an intriguing analogue the study lanf zone consists of faults which enucleated at depth 4 km during its earlier stage of evolution dissolution seams often arranged in s c fabric characterised the whole damage zone dissolution seams developed under very low grade metamorphism t 100 150 c as indicated by illite crystallinty analyses fault zone architecture and permeability features changed during the fault growth and exhumation permeability heterogeneity and anisotropy characterised the lanf zone during its development if geofluids circulated within the fault zone it could be an effective barrier during its earlier evolution being accompanied by dissolution seams on the contrary it could play as combined barriers conduits during its later evolution progressively at shallower levels being characterised by intersecting fault planes which define pipe like conduits parallel to the direction of the tectonic transport such a configuration could have the capacity to impact on fluids migration for long paths across the upper crustal levels this adds significant information for predicting deeper geothermal circuits and the location of potential exploitable reservoirs in active tectonic environments

structural setting and genesis of ore bodies in carbonate rocks in the m te atzei m te ega mining area sulcis sw sardinia at least seven different types of ore bodies with an ore stock of ba f fe pb zn cu and sb occur in paleozoic rocks lower middle cambrian and ordovician in an 15 km2 area north of the narcao village sw sardinia italy the ore bodies are related both to syngenetic accumulations and later epigenetic recirculation of the primary ores in the lower cambrian the area studied shows evidence of synsedimentary tectonic instability probably related to carbonate shelf margin features the upper cambrian is lacking and the transgressive ordovician sediments cover large areas of the previously gently folded cambrian rocks sardic phase of caledonian orogenesis the main hercynian tectonic phases had a much stronger compressive folding that is mirrored in a sequence of tight folds and upthrusts the geometric setting resulting from the tectonic frame of the cambrian and ordovician sediments must be taken into account to understand the distribution and the genesis of most of the ore bodies

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

effect of irrigation induced densification on the post failure behavior of loess flowslides occurring on the heifangtai area gansu china abstract irrigation resulted in serious ground settlement on the heifangtai terrace in china and also repeatedly triggered a lot of loess flowslides on the margin of the terrace to study the possible effect of resultant loess densification accompanying the ground settlement on the sliding behavior of these landslides we took loess samples from the source area of a landslide in the heifangtai terrace and performed a series of undrained ring shear tests to examine the undrained shear behaviors of these samples at differing initial void ratios results showed that all these tested samples exhibited purely contractive behavior throughout the entire undrained shearing process the loose samples suffered collapse failure behavior while those relatively denser samples experienced gradual increase in pore water pressure after the shear failure occurred the peak and steady state shear strengths increased as void ratio decreased however the brittleness index decreased with reduction of void ratio until a certain value after that it increased with further reduction of void ratio therefore we concluded that irrigation induced densification may have affected the occurrence and mobility of landslides occurring on the terrace margin of the heifangtai area

moraine preservation and boulder erosion in the tropical andes interpreting old surface exposure ages in glaciated valleys cosmogenic dating provides a long awaited means of directly dating glacial deposits that pre date the last glacial cycle although the potential benefits of longer chronologies are obvious the greater uncertainty associated with older cosmogenic ages may be less readily apparent we illus trate the challenges of developing and interpreting a long chronology using our data from the peruvian andes we used surface exposure dating with cosmogenic radionuclides crns 10 be and 26 al to date 140 boulders on moraines in valleys bordering the junin plain 11 s 76 w in central peru our chronology spans multiple glacial cycles and includes exposure ages greater than 1 million years which indicate that long term rates of boulder erosion have been very low interpreting the chronology of moraines for glaciations that predate the last glacial cycle is complicated by the need to consider boulder erosion and exhumation surface uplift and inheritance of crns from pre vious exposure intervals as an example we recalculate exposure ages using our boulder erosion rates 0 3 0 5 metres per million years and estimated surface uplift rates to emphasise both the chal lenges involved in interpreting old surface exposure ages and the value of chronological data even with large uncertainties when reconstructing the palaeoclimate of a region copyright 2005 john wiley sons ltd

undrained shear behavior of loess saturated with different concentrations of sodium chloride solution abstract a series of ring shear tests was conducted on saturated loess to investigate the effects of nacl concentration in pore water and desalinization on the shear behavior under undrained conditions the loess samples were taken from the ground surface of a frequently active landslide in china were saturated by de aired distilled water with different concentrations of nacl and then were sheared undrained after that the samples were retrieved remolded re set into the shear box and re saturated by passing through de aired distilled water such that the samples were desalinized and then were sheared undrained again through comparing the undrained shear behavior the effects of nacl in the pore water and desalinization on the undrained shear behavior of loess were examined the results showed that the variation of nacl concentration in pore water can strongly affect the shear behavior of saturated loess both the peak shear strength and steady state strength increased with increase of nacl concentration until a certain value after which they decreased with further increase of nacl concentration meanwhile the peak shear strength and steady state strength of the desalinized samples recovered to those of the original sample hence the effects of salinization are reversible these findings may be of practical importance to better understand the repeated occurrence of some irrigation induced loess landslides in china

a 3 d geodynamic model of lateral crustal flow during andean mountain building although the andes are believed to have resulted mainly from crustal shortening the shortening history remains debated and appears to require lateral along strike crustal flow three dimensional viscous flow modeling shows that within geological uncertainties the andes may have been produced by either neogene shortening alone or with significant pre neogene shortening these scenarios require major along strike crustal flow and predict significantly different histories of uplift and crustal motion

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

investigating links between climate and orography in the central andes coupling erosion and precipitation using a physical statistical model prior studies evaluated the interplay between climate and orography by investigating the sensitivity of relief to precipitation using the stream power erosion law spel for specified erosion rates here we address the inverse problem inferring realistic spatial distributions of erosion rates for present day topography and contemporaneous climate forcing in the central andes similarities in the altitudinal distribution and density of first order stream outlets and precipitation suggest a direct link between climate and fluvial erosion erosion rates are estimated with a bayesian physical statistical model based on the spel applied at spatial scales that capture joint hydrogeomorphic and hydrometeorological patterns within five river basins and one intermontane basin in peru and bolivia topographic slope and area data were generated from a high resolution 90 m digital elevation map and mean annual precipitation was derived from 14 years of tropical rainfall measuring mission 3b42v 7 product and adjusted with rain gauge data estimated decadal scale erosion rates vary between 0 68 and 11 59 mm yr with basin averages of 2 1 8 5 mm yr even accounting for uncertainty in precipitation and simplifying assumptions these values are 1 2 orders of magnitude larger than most millennial and million year timescale estimates in the central andes using various geological dating techniques e g thermochronology and cosmogenic nuclides but they are consistent with other decadal scale estimates using landslide mapping and sediment flux observations the results also reveal a pattern of spatially dependent erosion consistent with basin hypsometry the modeling framework provides a means of remotely estimating erosion rates and associated uncertainties under current climate conditions over large regions 2014 american geophysical union all rights reserved

kinematics of earthflows in the northern california coast ranges using satellite interferometry abstract slow moving landslides exhibit persistent downslope motion with variations in velocity driven by transient stress perturbations along the sliding surface here we use satellite insar and high resolution topographic data to identify 50 slow moving landslides in the northern california coast ranges and monitor their seasonal kinematics over 4 years these landslides have similar mechanical properties and are subject to the same external forcings which allows us to explore geometrical controls on kinematics to overcome errors associated with large deformation gradients we incorporate a deformation model in the insar processing that enables us to generate deformation time series we test our novel methodology using a synthetic deformation time series confirming our ability to resolve seasonal velocity patterns time series analysis of four representative landslides reveals that seasonal velocity changes are characterized by comparatively rapid acceleration and gradual deceleration each slide displays distinct kinematic zones with different mean velocities although velocity changes appear to occur synchronously along the landslide body over seasonal timescales because these deformation patterns are sensitive to subsurface geometry we employ a commonly used non newtonian viscous flow law to infer slide thickness and find that these slides likely exhibit a highly variable thickness and an irregular i e rough and non planar basal sliding surface our results suggest that slide geometry controls long term motion but does not strongly regulate their response to seasonal stress perturbations