analysis of the stability of i walls with gaps between the i wall and the levee fill following hurricane katrina an extensive investigation of the performance of floodwalls in the new orleans area was undertaken by the u s army corps of engineers and others this investigation included detailed study of failures of cantilevered sheet pile i walls during the hurricane an important lesson from this investigation was that gaps can form on the canal side of i walls as the water rises in the canal and causes the i wall to deflect once formed these gaps filled with water resulting in significantly higher loads on the walls gap formation was a key factor in several i wall failures and modeling such gaps correctly is clearly an important aspect of analyzing i wall stability this paper describes simple procedures for estimating the depths of gaps behind i walls for calculating the loads to which they are subjected and for including them in stability analyses the effects of gaps on the stability of the 17th canal and the london avenue canal i walls are discussed

grain size dependent concentration of cosmogenic 10be and erosion dynamics in a landslide dominated himalayan watershed for documenting recent or late quaternary erosion rates at the scale of a small watershed or even an entire mountain range the use of in situ terrestrial cosmogenic nuclides tcn such as 10be in river sediments has become widespread over the last decade in mountainous settings however landslides may induce a two fold complication in the cosmogenic nuclide budget first they may episodically deliver large amounts of sediment with low tcn concentrations to the river channel second they may generate a grain size concentration dependence in these sediments however studies that have explored grain size dependence in landslide dominated areas have reached differing conclusions and the underlying mechanisms remain poorly understood the present study focuses on the khudi khola river basin a small drainage basin in the central himalayas the area is characterized by steep slopes heavy rainfall and high sediment production rates importantly the watershed contains a large area of active landsliding in situ 10be was analyzed in sediments of grain sizes ranging from 75 m to 4 cm collected from five locations upstream downstream and in the small tributaries which drain the landslides in all sampling locations including those situated upstream of the landslides the finest grains 75 250 m are two to four times more concentrated in 10be than the largest clasts 4 7 mm we developed a numerical slope model which includes a low level of background soil erosion and episodic denudation from large mass wasting events we then introduced a coarsening of average grain size with soil depth to the model our simulation shows that the data available for this valley are compatible with a scenario in which landslides deliver coarse grains to the channel that are less concentrated in tcn and have deeper provenance best fit estimates of the model parameters suggest recurrence times of 3000 to 9000 years for a major landslide on the same slope and mean long term landslide denudation rates of 1 7 to 4 7 mm yr 1 a negative correlation between tcn concentration and grain size is also observed directly upstream and 5 km downstream of the landsliding area suggesting that nearly all of the sediment carried by the river is derived from ancient landslides while almost no sediment is supplied by erosion of soil mantled slopes despite these complications apparent denudation rates directly derived from the tcn concentrations and from previously published data in the region are all on the same order of magnitude around 2 mm yr 1 however a factor of three variability remains between the different studies depending on the location the year of sampling and the analyzed grain size fraction thus although tcn derived average denudation rates provide a useful first order estimate even in fast eroding terrains dominated by landslides caution should be applied when using quantitative results in such settings

increased late pleistocene erosion rates during fluvial aggradation in the garhwal himalaya northern india the response of surface processes to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution in the himalaya most large rivers feature prominent fill terraces that record an imbalance between sediment supply and transport capacity presumably due to past fluctuations in monsoon precipitation and or effects of glaciation at high elevation here we present volume estimates chronological constraints and 10 be derived paleo erosion rates from a prominent valley fill in the yamuna catchment garhwal himalaya to elucidate the coupled response of rivers and hillslopes to pleistocene climate change although precise age control is complicated due to methodological problems the new data support formation of the valley fill during the late pleistocene and its incision during the holocene we interpret this timing to indicate that changes in discharge and river transport capacity were major controls compared to the present day late pleistocene hillslope erosion rates were higher by a factor of 2 4 but appear to have decreased during valley aggradation the higher late pleistocene erosion rates are largely unrelated to glacial erosion and could be explained by enhanced sediment production on steep hillslopes due to increased periglacial activity that declined as temperatures increased alternatively erosion rates that decrease during valley aggradation are also consistent with reduced landsliding from threshold hillslopes as a result of rising base levels in that case the similarity of paleo erosion rates near the end of the aggradation period with modern erosion rates might imply that channels and hillslopes are not yet fully coupled everywhere and that present day hillslope erosion rates may underrepresent long term incision rates

stability of i walls in new orleans during hurricane katrina failures of i walls during hurricane katrina were responsible for many breaches in the flood protection system in new orleans six breaches were examined in detail by task group 7 of the interagency performance evaluation taskforce four of these failures and breaches which occurred before the water levels reached the top of the wall were not caused by overtopping erosion the failure of the i wall at the 17th street canal resulted from shear through the weak foundation clay the south failure of the london avenue i wall was caused by subsurface erosion which carried massive amounts of sand inland and removed support for the wall leading to catastrophic instability at the north breach on london avenue the failure was caused by high pore pressures combined with a lower friction angle in the loose sand which resulted in gross instability of the i wall under the water pressure load from the storm surge looking back with the benefit of 20 20 hindsight these stability and erosion failures can be explained in terms of modern soil mechanics exploration techniques laboratory test procedures and analysis methods an important factor in all of the cases investigated was development of a gap behind the wall as the water rose against the wall and caused it to deflect formation of the gap increased the load on the wall because the water pressures in the gap were higher than the earth pressures that had acted on the wall before the gap formed where the foundation soil was clay formation of a gap eliminated the shearing resistance of the soil on the flood side of the wall because the slip surface stopped at the gap where the foundation soil was sand formation of the gap opened a direct hydraulic connection between the water in the canal and the sand beneath the levee this hydraulic short circuit made seepage conditions worse and erosion due to underseepage more likely it also increased the uplift pressures on the base of the levee and marsh layer landward of the levee reducing stability because gap formation has such important effects on i wall stability and because gaps behind i walls were found in many locations after the storm surge receded the presence of the gap should always be assumed in i wall design studies

the influence of climate on the tectonic evolution of mountain belts simple physical arguments analogue experiments and numerical experiments all suggest that the internal dynamics of actively deforming collisional mountain ranges are influenced by climate however obtaining definitive field evidence of a significant impact of climate on mountain building has proved challenging spatial correlations between intense precipitation or glaciation and zones of rapid rock uplift have indeed been documented in numerous mountain ranges and are consistent with model predictions more compelling evidence such as tectonic changes in response to rather than just coincident with climate change has however rarely been documented triggered by a climate driven increase in erosion rate friction dominated mountain ranges are expected to show a number of simultaneous responses a decrease in the width of the range a temporary increase in sediment yield a persistent increase in the rate of rock uplift and a reduction in the subsidence rate of surrounding basins the most convincing field evidence for such a coordinated response of a mountain range to climate change comes from the european alps and the st elias range of alaska field studies and experimental research during the past two decades have provided considerable evidence for a significant influence of climate on tectonics recent advances suggest that model predictions can guide future fieldwork aimed at substantiating this view

regional crustal thickness and precipitation in young mountain chains crustal thickness is related to climate through precipitation induced erosion along the andes the highest mountains and thickest crust 70 km occur at 25 south a region of low precipitation westerly winds warm passing over the atacama desert precipitation is modest in the high andes and eastward over the altiplano severe aridity hence low erosion rates helps to account for the elevated volcanogenic contractional arc and high internally draining plateau in its rain shadow weak erosion along the north central arc provides scant amounts of sediment to the chile peru trench starving the subduction channel subcrustal removal might be expected to reduce the crustal thickness but is not a factor at 25 south the thickness of the gravitationally compensated continental crust cannot reflect underplating and or partial fusion of sediments but must be caused chiefly by volcanism plutonism and contraction contrasting climate typifies the terrane at 45 south where moisture laden westerly winds encounter a cool margin bringing abundant precipitation the alpine landscape is of lower average elevation compared with the north central andes and is supported by thinner continental crust 35 km intense erosion supplies voluminous clastic debris to the offshore trench and vast quantities are subducted however the southern andean crust is only about half as thick as that at 25 south suggesting that erosion not subcrustal sediment accretion or anatexis is partly responsible for the thickness of the mountain belt the himalayas plus tibetan plateau the sierra nevada plus colorado plateau and the japanese islands exhibit analogous relationships between crustal thickness and climate

the moho in australia and new zealand abstract australia and new zealand share in part a history in the gondwana supercontinent australia has a long and complex tectonic history with the last major accretion in the early paleozoic whereas new zealand is still undergoing major plate boundary processes the australian continent is relatively well covered with both active and passive seismic techniques multiple sources of information are therefore available for building a model of moho depth results from on shore and off shore refraction experiments are supplemented by receiver functions from a large number of portable stations and the recently augmented set of permanent stations moho picks from more than 10 500 km of full crustal reflection profiles provide valuable additional constraints the composite data set provides good sampling of much of australia though coverage remains low in some remote desert areas the various datasets provide multiple estimates of the depth to moho in many regions and the consistency between the different techniques is high some of the thinnest crust lies beneath the archean craton in the pilbara and in the neighbourhood of the simpson desert thick crust is encountered beneath parts of the proterozoic in central australia and beneath the paleozoic lachlan fold belt in southeastern australia there are a number of zones of sharp contrast in depth to moho notably in the southern part of central australia despite most of the continental material around new zealand being submerged moho data for this region is mainly onshore concentrating on the australia pacific plate boundary two major wide angle reflection transects provide the bulk of the active source data with just a few traditional reflection profiles offshore the plate boundary provides an abundance of local earthquakes for tomographic imaging and this data is supplemented with receiver functions from both portable and permanent networks onshore the combined coverage is as dense as that of australia although it could be argued that a higher spatial resolution is required to capture the nature of the moho of tectonically active new zealand three regions of thickened crust can be identified one beneath the southern alps another beneath fiordland and below the wanganui basin between the north and south island thin crust is identified west of the volcanic arc with extensive underplating below the back arc region

3 d pn tomography reveals continental subduction at the boundaries of the adriatic microplate in the absence of a precursor oceanic slab abstract slab pull generated by subducting oceanic lithosphere is generally considered as a major trigger for the onset of continental subduction however this may be in conflict with the occurrence of uhp terranes bearing no evidence of oceanic lithospheric rocks involved in the exhumation cycle here we image the uppermost mantle p velocity structure beneath the central mediterranean suggesting the possibility that the initiation of continental subduction may not require a precursor oceanic slab we combine i a three step inverted 3 d pn tomography model of the adriatic microplate with ii available geologic constraints and palinspastic reconstructions of the africa eurasia plate boundary zone our pn tomography model reveals elongated regions with vp

the many surface expressions of mantle dynamics plate tectonic theory suggests that present day topography can be explained by the repeated interactions between the tectonic plates moving along earth s surface however mounting evidence indicates that a significant proportion of earth s topography results from the viscous stresses created by flow within the underlying mantle rather than by the moving plates this dynamic topography is transient varying as mantle flow changes and is characterized by small amplitudes and long wavelengths it is therefore often hidden by or confused with the more obvious topographic anomalies resulting from horizontal tectonic movements however dynamic topography can influence surface processes and thus enter the geological record it has for example played a role in the establishment of amazon drainage patterns in turn surface processes such as the erosion of topographical anomalies could affect mantle flow this emerging view of dynamic topography suggests that the concept of plate tectonics as the driver of surface deformation needs to be extended to include the vertical coupling between the mantle and the surface unravelling this coupling back in time with the help of models and the geological record can potentially provide unprecedented insights into past mantle dynamics

exhumation and incision history of the lahul himalaya northern india based on u th he thermochronometry and terrestrial cosmogenic nuclide methods abstract low temperature apatite u th he ahe thermochronology on vertical transects of leucogranite stocks and 10 be terrestrial cosmogenic nuclide tcn surface exposure dating on strath terraces in the lahul himalaya provide a first approximation of long term 10 4 10 6 years exhumation rates for the high himalayan crystalline series hhcs for northern india the ahe ages show that exhumation of the hhcs in lahul from shallow crustal levels to the surface was 1 2 mm a and occurred during the past 2 5 ma bedrock exhumation in lahul fits into a regional pattern in the hhcs of low temperature thermochronometers yielding plio pleistocene ages surface exposure ages of strath terraces along the chandra river range from 3 5 to 0 2 ka two sites along the chandra river show a correlation between tcn age and height above the river level yielding maximum incision rates of 12 and 5 5 mm a comparison of our ahe and surface exposure ages from lahul with thermochronometry data from the fastest uplifting region at the western end of the himalaya the nanga parbat syntaxis illustrates that there are contrasting regions in the high himalaya where longer term 10 5 10 7 years erosion and exhumation of bedrock substantially differ even though holocene rates of fluvial incision are comparable these data imply that the orogen s indenting corners are regions where focused denudation has been stable since the mid pliocene however away from these localized areas where there is a potent coupling of tectonic and surface processes that produce rapid uplift and denudation plio pleistocene erosion and exhumation can be characterized by disequilibrium where longer term rates are relatively slower and shorter term fluvial erosion is highly variable over time and distance the surface exposure age data reflect differential incision along the length of the chandra river over millennial time frames illustrate the variances that are possible in himalayan river incision and highlight the complexity of himalayan environments

failure analysis of the breached levee at the 17th street canal in new orleans during hurricane katrina the breached levee system at the 17th street canal has been independently studied by conducting total and effective stress analyses performance of the levee system during the hurricane duration wa

higher erosion rates in the himalaya geochemical constraints on riverine fluxes the modern erosion rate of continental scale mountains is difficult to estimate and is usually based on measurement of the suspended load flux of rivers combined with assumptions about river bedload transport and sedimentation in flood plains these two parameters are very difficult to measure directly in continental scale basins in this paper we examine the chemical composition of the suspended load bedload and dissolved load of the ganga and brahmaputra rivers and compare them with the average composition of himalayan source rocks a mass balance equation of erosion fluxes shows that a si rich component is needed in addition to suspended and dissolved load fluxes to account for the composition of the source rock it corresponds to bedload sediment and flood plain deposits which are enriched in quartz by mineral sorting during transport the combined budget of si al and fe in the river system allows us to estimate this si rich flux by this method the total himalayan erosion is estimated to be twice the measured flux of suspended load the comparison between the brahmaputra and the ganga shows that the eastern himalaya has a higher erosion rate 2 9 mm yr than the western himalaya 2 1 mm yr this is likely the result of the higher runoff in the brahmaputra basin the intensity of the monsoon acts as a first order control of the erosion rate in the range

dating the onset of lower tagus river terrace formation using electron spin resonance in the western iberian peninsula staircases of fluvial terraces have been the subject of several recent studies in particular many recent publications have focused on the quaternary fluvial chronostratigraphy of the lower tagus basin however there are still doubts with respect to the timing of the first incision into the late tertiary basin fill deposits their upper part already recording a fluvial environment basin inversion which was the start of terrace formation this is because most dating methods are ineffective for this type of deposit generally without organic and or volcanic materials in the last 10 years new dating methods such as electron spin resonance esr applied to sedimentary quartz now facilitate more accurate chronologies this paper presents the results of the esr dating of the older terraces of the lower tagus basin portugal with extrapolation on the age of early drainage network evolution according the results the oldest fluvial terrace was formed around 900 ka so the origination of the portuguese tagus river terrace system can be attributed to the final part of the early pleistocene

incision and differential bedrock uplift along the indus river near nanga parbat pakistan himalaya from 10be and 26al exposure age dating of bedrock straths abstract well preserved river cut bedrock surfaces straths abandoned by the progressive incision of the indus river in northern pakistan were dated using in situ cosmogenic 10 be and 26 al exposure age dating measurements on young and modern straths show no significant ingrowth of 10 be and 26 al implying that strath exposure ages closely approximate their abandonment age strath exposure ages range up to 65 ka and increase with height above the river the straths can be divided into two groups low straths dated at about 7 ka which yield very rapid bedrock incision rates 9 12 m ka and high straths 7 ka in age which yield somewhat slower incision rates 1 6 m ka incision rates for both groups increase by 1 3 m ka downstream toward an active reverse fault the raikot fault that forms the western border of the nanga parbat haramosh massif nphm the downstream increases in incision rates for the low straths mimic downstream increases in the modern gradient suggesting that bedrock incision rates have been proportional to stream power over the last 7 ka gradient increases are probably the result of the creation of knickpoints by bedrock uplift along the raikot fault the longitudinal profile and steep gorge of the indus river in the study area indicate that bedrock incision appears to keep pace with differential vertical motions between the nphm and surrounding regions thus the 1 3 m ka difference in incision rates likely reflects the differential bedrock uplift rate between the nphm and the skardu basin the differential incision rate is consistent with differential exhumation rates obtained from apatite fission track ages assuming geotherms of 80 90 c km in the nphm and 35 c km in the skardu basin this relation suggests that rapid bedrock incision of at least 1 3 m ka has persisted within the nphm for the last 0 5 ma the acceleration of incision rates throughout the study area since 15 ka is likely to be a climatic signal that records an increase in the discharge and or sediment load of the indus river in the study area related to deglaciation of the surrounding terrane

geologic conditions underlying the 2005 17th street canal levee failure in new orleans a careful program of subsurface sampling and cone penetration test soundings was employed to characterize the geologic conditions beneath the failed portion of the 17th street canal levee in new orleans where a 150 m long section of the levee and floodwall translated up to 16 m when flood waters rose to 1 2 m of the wall s crest on august 29 2005 during hurricane katrina the subsurface conditions are characterized by discrete layers of fill placed upon the historic cypress swamp which is underlain by a deeper prehistoric cypress swamp these swamp deposits were consolidated beneath the levee and in the area of the 2005 failure the swamp materials infilled a natural depression believed to be an old slough which dipped below the sheetpile tips for a distance of about 50 m which corresponds to where the breach appears to have initiated detailed examination of the recovered soils suggest that recent hurricanes periodically inundated the swamps with saline and or brackish water which cause a mass

epicentre accuracy based on seismic network criteria summary we establish reliable and conservative estimates for epicentre location accuracy using data that are readily available in published seismic bulletins a large variety of seismic studies rely on catalogues of event locations making proper assessment of location uncertainty critical event location and uncertainty parameters in most global regional and national earthquake catalogues are obtained from traditional linearized inversion methods using a 1 d earth model to predict traveltimes reported catalogue uncertainties are based on the assumption that error processes are gaussian zero mean and uncorrelated unfortunately these assumptions are commonly violated leading to the underestimation of true location uncertainty especially at high confidence levels we find that catalogue location accuracy is most reliably estimated by station geometry we make use of two explosions with exactly known epicentres to develop local network location 0 2 5 accuracy criteria using monte carlo simulations of network geometry we find that local network locations are accurate to within 5 km with a 95 per cent confidence level when the network meets the following criteria 1 there are 10 or more stations all within 250 km 2 an azimuthal gap of less than 110 3 a secondary azimuthal gap of less than 160 and 4 at least one station within 30 km to derive location accuracy criteria for near regional 2 5 10 regional 2 5 20 and teleseismic 28 91 networks we use a large data set of exceptionally well located earthquakes and nuclear explosions beyond local distances we find that the secondary azimuthal gap is sufficient to constrain epicentre accuracy and location error increases when the secondary azimuthal gap exceeds 120 when station coverage meets the criterion of a secondary azimuth gap of less than 120 near regional networks provide 20 km accuracy at the 90 per cent confidence level while regional and teleseismic networks provide 25 km accuracy at the 90 per cent confidence level

practical earthquake location on a continental scale in australia using the ausrem 3d velocity model this study explores the full 3d earthquake location for the australian continent exploiting the recent 3d australian seismological reference model ausrem seismic velocities from ausrem were used as input to precompute finely spaced p and s travel time grids for each station in the australian national seismograph network using the multistage fast marching method travel times from anywhere in the grid to the corresponding station can then be computed by interpolation the location search using these travel times is based on matching observed and computed arrival times using the neighborhood algorithm all computations involved can be performed in practical time frames on a single processor computer the performance of the 3d approach relative to location using the 1d global ak135 velocity model was assessed by locating a set of recent earthquakes the arrival time residuals for p and s arrivals are significantly smaller when using the 3d ausrem model the improvements over ak135 are especially large in the 10 18 distance range in which a distance bias is strongly reduced and for those paths where the ak135 residuals are large a small set of six ground truth events was used to assess to what extent the reduction in travel time residuals leads to better absolute location accuracy the 3d location offset from the ground truth position is typically half that of the ak135 offset the patterns of offsets suggest that the already fast mantle wavespeeds in western australia need to be even faster than in ausrem

post earthquake landsliding and long term impacts in the wenchuan earthquake area china abstract the ms 8 0 wenchuan earthquake on may 12 2008 triggered tens of thousands of landslides and produced large amounts of loose material the loose material accumulated in gullies or on slopes provides abundant sources for the consequent debris flows which will endanger resettled residents and destroy urban reconstruction during the 5 years following the wenchuan earthquake event heavy rainfalls have already induced a great number of debris flows in the earthquake damaged area resulting in serious casualties and property losses the co seismic landslides and the debris flows induced by rainfalls in the mianyuan river basin are analyzed using multi temporal remote sensing images more than 2000 landslides were triggered and about 4 0 108 m3 of loose material was generated in the mianyuan river basin and the volume of erodible material is 6 0 107 1 6 108 m3 there were 1 27 107 m3 of bed load sediments and 6 3 105 m3 suspended load sediments transported into the river system in the past 5 years the active mass movements will last for a long period in the mianyuan river basin

evaluation and prediction of 17th street canal i wall stability using numerical limit analyses numericallimitanalyseshavebeenusedtoevaluatethestabilityofthe17thstreetcanali wallleveeduringhurricanekatrina the potential formation of a water filled gap along the canal side soil wall interface at failure is included in both the lower and upper bound for mulations the analyses replicate published two dimensional 2d cross sections and soil properties developed in forensic investigations car ried out by the interagency performance evaluation task force ipet and by the independent levee investigation team ilit the current results provide anindependent basis forunderstanding andevaluating the proposedfailure mechanisms anddemonstrate that awater filled gap is a necessary condition for the critical i wall failure mechanism further limit analysis calculations produce credible estimates of the surge elevation that caused failure of the 17th street canal i wall as well as predictions of a consistent failure mechanism the numerical limit anal yses show clearly how differences in the stability of the i wall are linked to different interpretations of the stratigraphy and undrained shear strengths by ipet and ilit the analyses also show that effects of a thin layer of weak organic clay as postulated by ilit are not necessary to explain the i wall failure doi 10 1061 asce gt 1943 5606 0000814 2013 american society of civil engineers ce database subject headings drainage walls clays lateral loads levees and dikes louisiana hurricanes structural stability author keywords upper and lower bound limits undrained stability walls clays limit equilibrium lateral loading

the incision variations of poiqu documented by the zhangmu landslide in the upper himalaya of tibet abstract aiming at the rate and causes of the incision variations in the upper himalaya orogenic belt of tibet a new method of incision rate estimation based on the analysis of the evolution of zhangmu landslide and its spatial and temporal relationship with the surrounding gullies is applied the research results are 1 the zhangmu landslide was an ancient huge landslide occurred at 24 2 2 4 ka bp consisting of an ancient bedrock landslide and subsequent deposit landslides with an area of 1 23 km2 and remaining volume of 23 4 106 m3 2 the fluvial incision rate shows variations in poiqu and its branch which may be controlled by the discharge and decreases from the poiqu 11 5 1 2 mm a to the tributaries from 4 8 0 5 mm a in the bangcundong gully to 2 4 0 2 mm a in zhangmu gully 3 the fluvial incision rate also shows temporal variations in the poiqu there are two periods of low rate and high rate incision processes in the poiqu while the section shape transforms from a gentle slope to a cliff in the low rate period from 24 2 ka bp to 10 0 ka bp in the poiqu valley the incision rate was 10 4 1 0 mm a while the high fluvial incision rate since 10 0 ka bp was 13 0 1 3 mm a 4 the fluvial incision promotes the landscape evolution and triggers the potential landslide in thousands of years

climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be cosmogenic radionuclide surface exposure dating abstract temporal and spatial changes in glacier cover throughout the late quaternary in tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region and the lack of numerical dating to help reconstruct the timing and extent of glaciation throughout tibet and the bordering mountains we use geomorphic mapping and 10 be cosmogenic radionuclide crn surface dating in study areas in southeastern gonga shan southern karola pass and central western nyainqentanggulha shan and tanggula shan tibet and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands each of the study regions receives its precipitation mainly during the south asian summer monsoon when it falls as snow at high altitudes gonga shan receives the most precipitation 2000 mm a 1 while near the margins of monsoon influence the karola pass receives moderate amounts of precipitation 500 600 mm a 1 and in the interior of the plateau little precipitation falls on the western nyainqentanggulha shan 300 mm a 1 and the tanggula shan 400 700 mm a 1 the higher precipitation values for the tanggula shan are due to strong orographic effects in each region at least three sets of moraines and associated landforms are preserved providing evidence for multiple glaciations the 10 be crn surface exposure dating shows that the formation of moraines in gonga shan occurred during the early mid holocene neoglacial and little ice age on the karola pass during the lateglacial early holocene and neoglacial in the nyainqentanggulha shan date during the early part of the last glacial cycle global last glacial maximum and lateglacial and on the tanggula shan during the penultimate glacial cycle and the early part of the last glacial cycle the oldest moraine succession in each of these regions varies from the early holocene gonga shan lateglacial karola pass early last glacial western nyainqentanggulha shan and penultimate glacial cycle tanggula shan we believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south asian monsoon and in particular in regional precipitation gradients in zones of greater aridity the extent of glaciation has become increasingly restricted throughout the late quaternary leading to the preservation of old 100 ka glacial landforms in contrast in regions that are very strongly influenced by the monsoon 1600 mm a 1 the preservation potential of pre lateglacial moraine successions is generally extremely poor this is possibly because lateglacial and holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations furthermore the intense denudation mainly by fluvial and mass movement processes which characterize these wetter environments results in rapid erosion and re sedimentation of glacial and associated landforms which also contributes to their poor preservation potential

probabilistic earthquake location in complex three dimensional velocity models application to switzerland 1 we present a new approach to determine precise and reliable hypocenter locations in the tectonically complex region of switzerland a three dimensional 3 d p wave velocity model to be used for earthquake relocation is obtained by simultaneously inverting arrival times of local earthquakes for hypocenter locations and 3 d p wave velocity structure a 3 d p wave velocity model derived from controlled source seismology css is used as an initial reference model the final 3 d model thus combines all available information from both css and local earthquake data the probabilistic nonlinear formulation of the earthquake location problem includes a complete description of location uncertainties and can be used with any kind of velocity model in particular the combination of nonlinear global search algorithms such as the oct tree importance sampling with probabilistic earthquake location provides a fast and reliable tool for earthquake location the comparison of hypocenter locations obtained routinely by the swiss seismological service sed to those relocated in the new 3 d velocity model using a probabilistic approach reveals no systematic shifts but does exhibit large individual shifts in some epicenter locations and focal depths we can attribute these large shifts in part to large uncertainties in the hypocenter location events with a low number of observations 8 and no observation within the critical focal depth distance typically show large location uncertainties improved hypocentral locations particularly for mine blasts and earthquakes whose routine hypocenter locations had been questionable confirm that improved velocity model and probabilistic earthquake location yield more precise and reliable hypocenter locations and associated location uncertainties for switzerland

rigorous plasticity solutions for the bearing capacity of two layered clays this paper applies numerical limit analysis to evaluate the undrained bearing capacity of a rigid surface footing resting on a two layer clay deposit rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity both methods assume a perfectly plastic soil model with a tresca yield criterion and generate large linear programming problems the solution to the lower bound linear programming problem is obtained by modelling a statically admissible stress field whereas the upper bound problem is solved through modelling a kinematically admissible velocity field results from the limit theorems typically bracket the true collapse load to within approximately 12 and have been presented in the form of bearing capacity factors based on various layer properties and geometries a comparison is made between existing limit analysis empirical and semi empirical solutions this indicates that the latt

catastrophic rock slope failures and late quaternary developments in the nanga parbat haramosh massif upper indus basin northern pakistan abstract the nanga parbat haramosh massif has some of the greatest relief on earth and highest measured rates of uplift denudation and river incision in bedrock many studies have sought to understand how its morphology relates to geotectonic evolution and glaciations however few catastrophic rock slope failures had been recognised and many of their impacts had been attributed to other processes recently more than 150 of these landslides have been found within a 100 km radius of nanga parbat 8125 m new discoveries are reported east north and west of nanga parbat along the indus streams most generated long run out rock avalanches that dammed the indus or its tributaries some impounding large lakes they initiated episodes of intermontane sedimentation followed by trenching and removal of sediment valley floor features record a complex interplay of impoundment and sedimentation episodes superimposition of streams in pre landslide valley floors and exhumation of buried features these findings depart from existing reconstructions of quaternary events a number of the rock avalanche deposits were previously misinterpreted as tills or moraine and their associated lacustrine deposits attributed to glacial lakes features up to 1000 m above the indus formerly seen as tectonically raised terraces are depositional features emplaced by landslides or erosion terraces recording the trenching of valley fill in landslide interrupted river reaches unquestionably tectonics and glaciation have been important but decisive and misread formative events of the holocene involve a post glacial landslide fragmented fluvial system the latter has kept valley developments in a chronic state of disequilibrium with respect to climatic and geotectonic controls accepted glacial chronologies are put in doubt particularly the extent and timing of the last major glaciation the pace and role processes in the holocene have been seriously underestimated

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

erosion and exhumation in the himalaya from cosmogenic isotope inventories of river sediments the outward erosional flux is a key factor in the tectonic evolution of mountain belts and there is much debate about the feedbacks between tectonics erosion and climate here we use cosmogenic nuclides 10be and 26al analysed in quartz from river sediments from the upper ganges catchment to make the first direct measurements of large scale erosion rates in a rapidly uplifting mountain belt the erosion rates are highest in the high himalaya at 2 7 0 3 mm yr 1 errors fall to 1 2 0 1 mm yr on the southern edge of the tibetan plateau and are 0 8 0 3 to 0 6 mm yr in the foothills to the south of the high mountains these relative estimates are corroborated by the nd isotopic mass balance of the river sediment analysis of sediment from an abandoned terrace suggests that similar erosion rates have been maintained for at least the last few thousand years the data presented here along with data recently published for european river catchments demonstrate that a log linear relationship between relief and erosion rate holds over three orders of magnitude variation in erosion rate and between very different climatic and tectonic regimes the erosion rate estimates from cosmogenic nuclides correlate well with exhumation rates calculated from previously published apatite fission track ages in the indian himalaya this confirms that much of the exhumation in the himalayan mountain chain is now balanced by erosion however exhumation rates calculated from high blocking temperature systems such as 40ar 39ar in muscovite imply lower exhumation rates rocks presently at the surface must have undergone a three to six fold increase in exhumation rate within the last few million years we show how this could be explained either by climatic forcing of erosion rate changes or by tectonics published evidence for equally rapid changes of exhumation rate in the past and the probable diachroneity in the time at which the present exhumation rates accelerated imply that tectonics has moderated at least some of the change in exhumation rates

new orleans and hurricane katrina iii the 17th street drainage canal the failure of the levee and floodwall section on the east bank of the 17th street drainage canal was one of the most catastrophic breaches that occurred during hurricane katrina it produced a breach that rapidly scoured a flow pathway below sea level so that after the storm surge had largely subsided floodwaters still continued to stream in through this breach for the next two and a half days this particular failure contributed massively to the overall flooding of the metropolitan orleans east bank protected basin slightly more than half of the loss of life and a similar fraction of the overall damages occurred in this heavily populated basin there are a number of important geotechnical and geoforensic lessons associated with this failure accordingly this paper is dedicated solely to investigating this single failure geological and geotechnical details such as a thin layer of sensitive clay that was laid down by a previous hurricane proper strength characterization of soils at and beyond the toe of the levee and recognition of a water filled gap on the inboard side of the sheet pile cutoff wall are judged to be among the most critical factors in understanding this failure the lessons learned from this study are of importance for similar flood protection systems throughout other regions of the united states and the world

failure mechanisms in two layer undrained slopes this note presents results of stability analyses of two layer undrained slopes by the finite element method the study focuses on the circumstances under which either deep or shallow failure mechan

modern erosion rates in the high himalayas of nepal abstract current theories regarding the connections and feedbacks between surface and tectonic processes are predicated on the assumption that higher rainfall causes more rapid erosion to test this assumption in a tectonically active landscape a network of 10 river monitoring stations was established in the high himalayas of central nepal across a steep rainfall gradient suspended sediment flux was calculated from sampled suspended sediment concentrations and discharge rating curves accounting for solute and bedload contributions the suspended sediment fluxes were used to calculate watershed scale erosion rates that were then compared to monsoon precipitation and specific discharge we find that in individual watersheds annual erosion rates increase with runoff in addition our data suggest average erosion rate increases with discharge and precipitation across the entire field site such that the wetter southern watersheds are eroding faster than the drier northern watersheds the spatially non uniform contemporary erosion rates documented here are at odds with other studies that have found spatially uniform long term rates 10 5 10 6 yr across the pronounced rainfall gradient observed in the region the discrepancy between the modern rates measured here and the long term rates may be reconciled by considering the high erosional efficiency of glaciers the northern catchments were much more extensively glacierized during the pleistocene and therefore they likely experienced erosion rates that were significantly higher than the modern rates we propose that in the northern watersheds the high rates of erosion during periods of glaciation compensate for the low rates during interglacials to produce a time averaged rate comparable to the landslide dominated southern catchments

epcrust a reference crustal model for the european plate summary we present a new crustal model for the european plate derived from collection and critical integration of information selected from the literature the model covers the whole european plate from north africa to the north pole 20 n 90 n and from the mid atlantic ridge to the urals 40 w 70 e the chosen parametrization represents the crust in three layers sediments upper crust and lower crust and describes the 3 d geometry of the interfaces and seismologically relevant parameters isotropic p and s wave velocity plus density with a resolution of 0 5 0 5 on a geographical latitude longitude grid we selected global and local models derived from geological assumptions active seismic experiments surface wave studies noise correlation receiver functions model epcrust presents significant advantages with respect to previous models it covers the whole european plate it is a complete and internally consistent model with all the parameters provided also for the sedimentary layer it is reproducible it is easy to update in the future by adding new contributions and it is available in a convenient digital format epcrust could be used to account for crustal structure in seismic wave propagation modelling at continental scale or to compute linearized crustal corrections in continental scale seismic tomography gravity studies dynamic topography and other applications that require a reliable crustal structure because of its resolution our model is not suited for local scale studies such as the computation of earthquake scenarios where more detailed knowledge of the structure is required we plan to update the model as new data will become available and possibly improve its resolution for selected areas in the future

late quaternary landscape evolution and genesis of the 2009 catastrophic landslide in the hsiao lin area southwestern taiwan abstract with cumulative rainfall of 1700 mm typhoon morakot triggered a catastrophic landslide at hsiao lin 9 august 2009 which dammed the river buried the village and killed 400 people we conducted a geomorphic study to understand the origin of this landslide in the context of the long term evolution of the hillslope the landslide originated from a broad poorly drained slope 21 23 and ran down along two first order channels the erosion up to 80 m thick has created a concave shape slope and exposed mostly loose debris which implies that the landslide was mainly the reworking of ancient colluviums the genesis of the concave shape slope where the source sediments of the landslide resided reflects the weakness of the mudstone shale bedrock underlying this slope in contrast to the sandstone based transport area the two channels in the transport area also follow old faults or joints given that the source area has been subject to erosion during large landslides the subsequent deposition here was likely achieved by minor colluvial processes this deposition continued until the catastrophic failure in 2009 which could be controlled by 1 the amount of sediments deposited which determined the slope angle and 2 the headward expansion of the channels from the transport area which enhanced groundwater convergence and later provided routes for the landslide materials to run downslope extensive mass wasting motions had occurred in the area as shown by the prevalence of 20 m thick landslide debris flow sequences on the lower part of the hillslope which are dated 21 14 9 13 7 and 12 0 ka by the radiocarbon method these mass wasting events had hindered the long term incision of the trunk river in response to the rapid tectonic uplift at least the 12 0 ka event which caused extensive mud flow deposition had dammed the river overall this study shows how bedrock lithology and structures controlled the shape of a hillslope and caused extremely unsteady mass wasting transport in the active mountains of taiwan

controls on the patterns of topography and erosion rate in a critical orogen 1 we solve for the steady state patterns of erosion rate and topography in a critical wedge to understand the mutual adjustment of tectonics erosion and topography in the absence and presence of spatial variations in precipitation rate we consider steady state systems in which tectonics favors a critical topographic form assumed to be the mean elevation across the range and in which surface erosion by rivers and hillslopes operates on a two dimensional landscape we find that 1 a nonuniform critical topographic form implies a nonuniform pattern of ridge valley relief and hence a nonuniform pattern of erosion rate and 2 when the system is forced by local variations in precipitation rate maintenance of the critical topographic form requires a local response of rock uplift that greatly dampens changes in topography we apply these concepts to the western side of the olympic mountains of washington state where mean elevation ridge valley relief and precipitation rates increase from the coast to the topographic crest of the range we find that the main control on the erosion rate pattern is the pattern in mean elevation and the amount of precipitation in contrast the pattern of precipitation is only a minor control as a whole our work demonstrates an approach for developing the theoretical context that is necessary for interpreting spatial associations between patterns in topography precipitation and erosion in natural orogens

geohazards and large geographically distributed systems a general classification for scale in geotechnical engineering is used to explore the modelling of large geographically distributed systems and their response to geohazards both component and network performance are reviewed with respect to components prototype scale experiments of underground pipeline response to abrupt ground deformation are described including control of soil properties soil pipeline interaction and performance of high density polyethylene pipelines direct shear ds apparatus size is shown to have a significant effect on ds strength and the most reliable ds device is identified from comparative tests with different equipment mohr coulomb strength parameters for partially saturated sand are developed from ds test data and applied in finite element simulations of soil pipeline interaction that show excellent agreement with prototype scale experimental results apparent cohesion measured during shear failure of partially saturated sand is caused by suction induced dilatancy wi

esr in the 21st century from buried valleys and deserts to the deep ocean and tectonic uplift abstract electron spin resonance esr dating can date many materials including hydroxyapatite in enamel and some fish scales aragonite and calcite in corals molluscs some travertine and calcrete and quartz from ash fluvial deposits and some flint dating studies using these materials have numerous potential applications in many varied quaternary settings esr dating uses signals resulting from trapped charges created by radiation in crystalline solids ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation when compared to other dating techniques age agreement has been excellent for teeth corals molluscs and quartz recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment new chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift using tooth and mollusc dates to assess water availability in deserts and using isochron data to assess u uptake processes into teeth when coupled with other geochemical and geomorphological techniques esr can provide the chronometric control to build paleoclimatic and other paleoenvironmental records many other applications are possible from heating studies for artefacts to dating sulphates and other minerals on distant planets

uppermost mantle p wavespeed structure beneath eastern china and its surroundings abstract pn travel time tomography provides a way of improving structural information on the uppermost mantle across eastern china exploiting recent developments of dense seismic networks with well recorded seismic events we used waveforms from 2009 at chinese stations supplemented by bulletin arrival times an initial p wave model was constructed using the crustal model from crust1 0 coupled to a p wave model in the mantle derived from the sl2013sv model to capture the broad scale features this starting model enables us to compensate for the large contrasts in crustal thickness across the region all events were relocated using the initial 3 d p model and after relocation consistent patterns of travel time residuals are obtained we extract pn as the first arrival in the distance range 1 8 to 12 we use the fmtomo fast marching tomography approach to invert the travel time results to generate a p wavespeed structure with a resolution of 2 2 down to 75 km there are considerable variations in pn wavespeed in the uppermost mantle across the region the central portion of the north china craton is imaged with particularly slow p wavespeeds whilst most of the neighbouring ordos block is fast fast p wavespeeds extend through much of the uppermost mantle beneath eastern central asia orogen northeast china and beneath the korean peninsula in the south the sichuan block and the western yangtze craton show rather fast p wavespeeds the tanlu fault system appears to cut through the crust into the mantle with marked slow p wavespeed at its southern end

uppermost mantle structure of the australian continent from pn traveltime tomography past studies of the seismic structure of the australian continent have dominantly exploited surface wave tomography for the mantle with seismic refraction receiver functions and ambient noise used for crustal structure the 3 d structure has been summarized in the australian seismological reference model ausrem for which the zone immediately below the crust is the least well characterized pn traveltime tomography provides a way of improving structural information on the uppermost mantle across the continent we have exploited waveforms from larger events across australia recorded at both permanent and portable stations since 1993 supplemented by bulletin arrival times to compensate for the large velocity contrasts with much faster mantle wave speeds in the center and west all events were relocated using the ausrem model after relocation consistent patterns of traveltime residuals are obtained we extract pn as the first arrival in the distance range 1 8 to 15 we use the fmtomo approach to invert the travel time residuals to generate a p wave speed structure with a resolution of 3 3 there is strong heterogeneity in pn wave speed in the uppermost mantle across the continent the fastest pn wave speed of 8 36 km s beneath the precambrian cratons of western and central australia is 3 99 faster than the global ak135 model and the slowest pn wave speed 7 66 km s on the eastern margin is 4 74 slower the slowest velocities in the uppermost mantle are found along the eastern margin of the australian continent beneath the phanerozoic orogenic belts with links to neogene volcanism

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

geology of the new orleans area and the canal levee failures the geologic history of the new orleans area significantly influences the engineering properties of the foundation soils beneath the levees geologic and engineering data gathered from the levee breaches identify a spatially complex geomorphic landscape caused by holocene sea level rise lateral changes in depositional environments development of mississippi river delta lobes and the distributary channels associated with delta development overlying the pleistocene surface beneath new orleans are predominantly fine grained shallow water sediments associated with bay sound or estuarine nearshore gulf sandy beach lacustrine interdistributary and paludal marsh and swamp environments these environments define the new orleans area history during the holocene and comprise the levee foundation beneath the failure areas a barrier beach ridge is present in the subsurface along the southern shore of lake ponchartrain which blocked the filling of the lake with fluvial deltaic sediments this buried beach impacted the supply and texture of sediment being deposited by advancing distributary channels and influenced the engineering properties of these soils marsh and swamp soils beneath the failure area at the 17th street canal are much thicker in comparison to those beneath the london avenue canal failures because of the influence of the beach complex and are thickest in the industrial canal area additionally human activities in the new orleans area during historic time contributed to the spatial complexity and affected the engineering properties of the foundation soils these activities include construction of drainage and navigation canals groundwater pumping hydraulic filling of the lake ponchartrain lake front and construction of levees to prevent river flooding human activities combined with the geologic setting and subsidence in this region are responsible for the unique landscape that was impacted by hurricane katrina

quaternary glacial history of the central karakoram abstract the quaternary glacial history of the world s highest mountains the central karakoram is examined for the first time using geomorphic mapping of landforms and sediments and 10 be terrestrial cosmogenic nuclide surface exposure dating of boulders on the moraines and glacially eroded surfaces four glacial stages are defined the bunthang glacial stage 0 7 ma the skardu glacial stage marine oxygen isotope stage mis 6 or older the mungo glacial stage mis 2 and the askole glacial stage holocene glaciers advanced several times during each glacial stage these advances are not well defined for the oldest glacial stages but during the mungo and askole glacial stages glacial advances likely occurred at 16 11 13 5 and 0 8 ka the extent of glaciation in this region became increasingly more restricted over time in the braldu and shigar valleys glaciers advanced 150 km during the bunthang and skardu glacial stages while glaciers advanced 80 km beyond their present positions during the mungo glacial stage in contrast glaciers advanced a few kilometers from present ice margins during the askole glacial stage glacier in this region likely respond in a complex fashion to the same forcing that causes changes in northern hemisphere oceans and ice sheets teleconnected via the mid latitude westerlies and also to changes in monsoonal intensity

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

catastrophic landslide induced by typhoon morakot shiaolin taiwan abstract typhoon morakot induced the catastrophic and deadly shiaolin landslide in southern taiwan on 9 august 2009 resulting in more than 400 casualties we undertook a geological and geomorphological investigation with the aim of reconstructing the events leading up to this landslide and to clarify factors that contributed to its development cumulative rainfall reached up to 1676 5 mm in about three days under the influence of the typhoon and the shiaolin landslide with a volume of 25 106 m3 occurred one day after the peak in rainfall intensity the landslide occurred on a dip slope overlying late miocene to early pliocene sedimentary rocks consisting of silty shale massive mudstone and sandstone it started as a rockslide in the upper third of the landslide area and transformed into a rock avalanche that crossed a series of terraces and displaced or buried the village below it buried the riverbed of the chishan river and ran up the opposite slope creating a landslide dam 60 m high which was breached about 1 h and 24 min later flooding the village the velocity of the landslide is estimated to have been 20 4 to 33 7 m s 1 and its apparent friction angle was 14 which indicates its high mobility the detachments in the source area consist of combinations of bedding planes and joints or faults the landslide was preceded by gravitational deformation which appeared as hummocky landforms before the landslide and as buckle folds exposed after the event the landslide deposits consist of fragments of mudstone shale and sandstone as well as clayey material at its base this clayey material consisting of illite chlorite quartz feldspar and calcite is assumed to have strongly influenced the long rapid runout

giant landslides topography and erosion abstract distributions of slope angles in tectonically active mountain belts point to the development of threshold conditions where hillslopes attain a critical inclination or height at which they fail readily because of limitations in material strength it has been proposed that hillslopes adjust to rapid uplift and bedrock incision through an increase in the rate of relief limiting landsliding rather than gradual slope steepening here we test this concept by investigating the relationship between mean local relief h which we take to be a proxy of long term erosion rates e and the occurrence of over 300 of the largest v 10 8 m 3 terrestrial landslides on earth we find that nearly two thirds of these giant landslides have occurred in the steepest 5 of the earth s land surface where relief is close to its proposed upper strength limit they are primarily located in deeply incised valleys along fault bounded fringes of active mountain belts and in volcanic arcs this distribution coincides with areas of high long term erosion rates 4 mm yr 1 confirming that giant landslides contribute to rapid denudation of mountains most of the eroded volume is concentrated in the smallest but steepest parts of mountain belts and volcanic arcs first order estimates of minimum erosion rates accomplished by the largest landslides are 0 01 mm yr 1 these rates are between 1 and 10 of the late pleistocene to holocene mean erosion rates in a given area importantly the landslide erosion rates show a nonlinear increase with mean local relief suggesting that the contribution of giant landslides in total and per event increases significantly with increasing overall erosion rates however giant landslides also occur in areas of lower than average relief h 300 700 m irrespective of whether threshold hillslopes have developed or not factors contributing to these failures include soft rocks extensive low angle discontinuities high rates of fluvial bedrock incision and tectonically driven deformation and slope loading

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

on seismological reference models and the perceived nature of heterogeneity a key ingredient in understanding earth structure is the integration of seismological information with results from mineral physics for both the dominant radial dependence of material properties and the 3d structure revealed by seismic tomography in each case an important role is played by reference models for the internal structure of the earth originally constructed to meet seismological needs representations of the travel times of seismic phases are required for the location of seismic events and these have been supplemented by models that match the frequencies of the free oscillation of the earth which have played a major role in characterising seismic sources through the centroid moment tensor derived from long period records parameterised models were introduced to combat the computational demands of inversion and have been extensively used however in such models e g prem the form of the seismic parameters is prescribed to have a functional behaviour such as a cubic based on mathematical convenience rather than physical requirements any 1d models face the challenge of the significant lateral heterogeneity at the top and bottom of the mantle as well as the more subtle variations in between it may well be possible to capture the long wavelength components of 3d heterogeneity but the nature of available data sources means that it will be difficult to achieve comparable p and s definition for the whole mantle in many circumstances reference models are used for comparison with models constructed for different data sets it is then best that e g a cratonic reference model is used to judge results from cratons regionalisation of travel time observations provides a means of constructing such reference models for a broad range of tectonic environments when coupled with suitable path corrections it is possible to make a good account of regional 2d variations it is desirable that reference models used for interpretation of seismic tomography are tied as clearly as possible to mineral physics results with a representation based on the bulk modulus k shear modulus g and density rather than just the p and s wavespeeds comparator models for different mineral compositions and temperature regimes have the potential to aid the interpretation of tomographic images particularly in the separation of the influences of temperature and composition

ausmoho the variation of moho depth in australia summary since 2004 more than 7000 km of full crustal reflection profiles have been collected across australia to give a total of more than 11000 km providing valuable new constraints on crustal structure a further set of hitherto unexploited results comes from 150 receiver functions distributed across the continent mostly from portable receiver sites these new data sets provide a dramatic increase in data coverage compared with previous studies and reveal the complex structure of the australian continent in considerable detail a new comprehensive model for moho depth across australia and its immediate environment is developed by utilizing multiple sources of information on shore and off shore refraction experiments are supplemented by receiver functions from a large number of portable stations and the recently augmented set of permanent stations and moho picks from the full suite of reflection transects the composite data set provides a much denser sampler of most of the continent than before though coverage remains low in the remote areas of the simpson and great sandy deserts the various data sets provide multiple estimates of the depth to moho in many regions and the consistency between the different techniques is high in a number of instances differences in estimates of moho depth can be associated with the aspects of the structure highlighted by the particular methods the new results allow considerable refinement of the patterns of moho depth across the continent some of the thinnest crust lies beneath the archean cratons in the pilbara and the southern part of the yilgarn thick crust is encountered beneath parts of the proterozoic in central australia and beneath the palaeozoic lachlan fold belt in southeastern australia the refined data indicate a number of zones of sharp contrast in depth to moho notably in the southern part of central australia

catastrophic landslides and their effects on the upper indus streams karakoram himalaya northern pakistan abstract the paper examines the nature and geomorphic influences of deposits from rock avalanches that obstruct rivers most of the 115 rockslide rock avalanche events identified in the karakoram himalaya straddled one or more stream valleys at least 73 of these landslides formerly dammed the indus or its tributaries upstream of the barriers remnants exist of once very extensive lacustrine deposits the stability and long term survival of dams from large rock avalanches is addressed and the reasons for the gradual or phased rather than catastrophic and sudden breaching case histories emphasise the erosional and depositional forms associated with the barriers they are reconstructed in terms of the emplacement and properties of the deposits from rock avalanches and the response of the river to interruption by them these barriers have exerted a substantial control over stream response and development for most of the holocene at least today they are associated with distinctive features of channel form and thalweg river terrace systems intermontane sediment sinks and sources and local erosional forms in bedrock more broadly the landslide barriers have created a naturally fragmented river system deposition and erosion in the lower few tens or hundreds of meters of the upper indus stream valleys have been dominated by epicycles of aggradation trenching and downcutting that mainly reflect the scale timing and history of each barrier the landforms involved are only indirectly related to the late glacial and paraglacial conditions that have hitherto been regarded as the main explanation

epmantle a 3 d transversely isotropic model of the upper mantle under the european plate summary we present a new 3 d transversely isotropic shear wave velocity model of the european and mediterraneanuppermantleobtainedbyanalysisofsurfacewaves datausedarefundamentalmode rayleigh and love group velocity measurements in the period range 35 170 s taken on seismograms recorded by european stations for regional earthquakes the tomographic inversion to map the 3 d earth structure is split into two steps first we regionalize the group velocity dispersion measurements obtaining distinct geographical group velocity maps at different periods then each local dispersion curve is inverted separately to find the shear wave velocity structure at depth the inversion benefits from using ap rioriinformation from a 3 d global mantle model s20rts and a new detailed european crustal model epcrust to constrain the shallower layers the inversion scheme follows a non linear iterative algorithm by which rayleigh and love group slowness are inverted simultaneously for the best fitting isotropic voigt shear wave speed 2 vsv 1 vsh and radial anisotropy parameter vsh vsv final merging of the vs profiles results in a new higher resolution 3 d model of european upper mantle we find that western europe and mediterranean sea are mainly characterized by relatively low velocities strongly contrasting with the fast roots of the eastern european craton many regional scale structures are also evident in the model thus providing insights into the complex geodynamic framework of the european continent most prominent are the low velocity west mediterranean spreading basins and european cenozoic rift system and seismically fast features connected to subduction of adria microplate hellenic arc and calabrian arc radial anisotropy does not vary very significantly with respect to the prem profile as available data only resolve lateral variations to a limited degree due to trade off with velocity epmantle has the potential to provide a reliable seismological reference for the upper mantle structure in the broad european region

liquefaction and soil failure during 1994 northridge earthquake the 1994 northridge california earthquake caused widespread permanent ground deformation on the gently sloping alluvial fan surface of the san fernando valley the ground cracks and distributed deformation damaged both pipelines and surface structures to evaluate the mechanism of soil failure detailed subsurface investigations were conducted at four sites three sites are underlain by saturated sandy silts with low standard penetration test and cone penetration test values these soils are similar to those that liquefied during the 1971 san fernando earthquake and are shown by widely used empirical relationships to be susceptible to liquefaction the remaining site is underlain by saturated clay whose undrained shear strength is approximately half the value of the earthquake induced shear stress at this location this study demonstrates that the heterogeneous nature of alluvial fan sediments in combination with variations in the groundwater table can be responsible for complex patterns of permanent ground deformation it may also help to explain some of the spatial variability of strong ground motion observed during the 1994 earthquake

interpretation of direct shear box testing of sands as quasi simple shear interpretation of the direct shear box dsb test implicitly assumes a simple shear mode of deformation but this assumption has not been fully verified in particular in tests on sands this paper describes a laboratory investigation which was commissioned to find an optimum configuration of a dsb apparatus for measuring the strength and dilatancy characteristics in direct simple shear the examination was made in a newly developed dsb apparatus using dry specimens of two standard sands toyoura sand and silver leighton buzzard sand boundary effects such as the wall friction the size of the opening between the two halves of the shear box and the constraint imposed by the loading platen were each independently examined in pilot tests to determine their influence on the measurements of strength and angle of dilatancy the optimum configuration was determined through careful examination of the boundary stresses and strains of rectangular specimens subjected to shearing under drained and constant volume

constraints on the early uplift history of the tibetan plateau the surface uplift history of the tibetan plateau and himalaya is among the most interesting topics in geosciences because of its effect on regional and global climate during cenozoic time its influence on monsoon intensity and its reflection of the dynamics of continental plateaus models of plateau growth vary in time from pre india asia collision e g 100 ma ago to gradual uplift after the india asia collision e g 55 ma ago and to more recent abrupt uplift 7 ma ago and vary in space from northward stepwise growth of topography to simultaneous surface uplift across the plateau here we improve that understanding by presenting geologic and geophysical data from north central tibet including magnetostratigraphy sedimentology paleocurrent measurements and 40ar 39ar and fission track studies to show that the central plateau was elevated by 40 ma ago regions south and north of the central plateau gained elevation significantly later during eocene time the northern boundary of the protoplateau was in the region of the tanggula shan elevation gain started in pre eocene time in the lhasa and qiangtang terranes and expanded throughout the neogene toward its present southern and northern margins in the himalaya and qilian shan

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

episodic fluvial incision of rivers and rock uplift in the himalaya and transhimalaya abstract seventeen strath terraces in northern india were dated using 10 be surface exposure methods ages range from c 7 to c 735 ka and provide fluvial incision rates of 0 02 0 003 to 2 6 1 9 mm a 1 on the northern side of the ladakh range incision rates are c 1 mm a 1 in the northern zanskar range they are 0 06 0 005 mm a 1 new and published incision rates in southernmost lahul range from 0 1 0 02 to 13 2 6 2 mm a 1 rates for ages 35 ka are 0 4 0 2 mm a 1 across the himalaya and transhimalaya holocene fluvial incision rates range from c 0 02 to c 26 0 mm a 1 whereas pleistocene incision rates are 5 mm a 1 many of the holocene incision rates exceed exhumation rates whereas pleistocene incision rates are comparable with exhumation rates this suggests that long term fluvial incision is in dynamic steady state with exhumation the temporal pattern for rates of fluvial incision is probably controlled by episodic incision linked to significant precipitation changes throughout the quaternary suggesting that strath terraces with ages 35 ka can be used for assessing long term rates of rock uplift in contrast rates of fluvial incision based on late glacial and holocene strath terraces reflect changes in monsoon intensity and deglaciation events by determining ages for multiple samples on flights of strath terraces it is possible to document changes in incision rate assess whether post abandonment transient shielding has occurred and help elucidate tectonic v climatic controls on their formation supplementary material tables ds1 4 for previously published data and recalculated ages for strath terraces and figures ds1 and ds2 showing plots of incision rates against time for the himalaya and transhimalaya are available at http www geolsoc org uk sup18454

a simple algorithm for local earthquake location using 3d vp and vs models test examples in the central united states and in central eastern taiwan traditional local earthquake location using a horizontally layered homogeneous velocity model is limited in its resolution and reliability due to the existence of frequently overlooked 3d complexity of the real earth during traditional 3d seismic tomography simultaneous earthquake relocation using the resultant 3d velocity model has produced reliable earthquake locations however only a small subset of events are typically used and thus relocated in the inversion the rest of the events in a catalog must then be relocated using the 3d models the repeated calculation of travel times across 3d v p and v s models is also not efficient and not practical for a routine network earthquake location when the very time consuming exact 3d raytracing is used because high resolution earthquake data are now available from many modern seismic networks representative high resolution 3d v p and v s models for a region can be better determined by taking advantage of recently available high speed computer technology and large disk space we implemented a simple algorithm to efficiently locate every local earthquake using the best available regional 3d v p and v s models once the v p and v s information for all cubic cells in a 3d grid model are determined p and s travel times from each grid point to all seismic stations can be calculated and stored on disk files for later usage during the iteration process for earthquake location travel times from a trial hypocenter to all recording stations can be determined simply by a linear interpolation from those of the adjacent eight grid points available in the previously stored disk files without the need for raytracing the iterations continue until the hypocenter adjustments at the end of the last iteration are below the given criteria and the travel time residual or the difference between the observed and the calculated travel times is a minimum therefore any local earthquake can be efficiently and reliably located using the available 3d velocity models this simple location program has been applied to relocate earthquakes in the new madrid seismic zone nmsz of the central united states and in the central eastern taiwan region preliminary results in both regions reveal that earthquake hypocenters can be efficiently relocated in spite of the very significant lateral structural variations tests with data from taiwan further demonstrate that the resolution of seismic tomography and the relocated seismicity is sensitive to relative distribution of seismic network stations and background seismicity thus this single event location program can be applied to relocate all earthquakes in a seismic network catalog and more importantly to allow routine earthquake location for any seismic network using the available 3d velocity models

the siwaliks of western nepal ii mechanics of the thrust wedge abstract comparison between numerical models and structural data is used for a better understanding of the evolution of the siwalik thrust belt of western nepal the numerical model involves discontinuities within a critical wedge model a kinematic forward model of serial cross sections and a linear diffusion algorithm to simulate erosion and sedimentation in western nepal large piggy back basins duns are located above thick thrust sheets that involve more than 5500 m of the neogene siwalik group whereas piggy back basin sedimentation is less developed above thinner thrust sheets 4300 m thick numerical model results suggest that thrust sheet thickness and extension of wedge top basins are both related to an increase of the basal decollement dip beneath the duns the west dang transfer zone wdtz is a n ne trending tectonic lineament that limits the westward extent of the large piggy back basins of mid western nepal and is linked to a thickening of the himalayan wedge eastward the wdtz also affects the seismotectonics pattern the geometry of the thrust front the lateral extent of lesser himalayan thrust sheets and the subsidence of the foreland basin during middle siwalik sedimentation numerical models suggest that the individualisation of the piggy back basins at the transition between the middle siwalik and upper siwaliks followed the deposition of the middle siwaliks that induced a geometry of the foreland basin close to the critical taper as wdtz induces an e w thickning of the himalayan wedge it could also induce a northward shift of the leading edge of the ductile deformation above the basal detachment in greater himalayas of far western nepal field data locally suggest episodic out off sequence thrusting in the frontal thrust belt of western nepal whereas numerical results suggests that episodic out off sequence reactivation could be a general characteristic of the himalayan wedge evolution often hidden by erosion