investigating surface movements of debris covered miage glacier western italian alps using dendroglaciological analysis dendroglaciological analysis of supraglacial trees represents an example of applied dendro geomorphological methods in reconstructing glacier variations supraglacial trees react to glacier ice and debris movement assuming typical shapes with modified radial growth in this paper based on tree ring analysis of larix decidua mill we investigate the relationship between the distribution and growth of trees located on the most famous and representative debris covered glacier in the italian alps miage glacier valle d aosta and the superficial movements of ice and debris in the lower part of the tongue different growth anomalies e g pointer years compression wood abrupt growth changes were identified and dated three reference tree ring chronologies based on undisturbed larches growing outside the glacier were constructed for comparison with tree ring data from supraglacial trees the oldest sampled trees colonized the glacier surface just before 1960 the simultaneous presence of different disturbance indicators occurred mainly between 1984 and 1990 on the southern lobe and during the period 1989 93 on the northern glacier lobe these results fit with glaciological data documenting volume and surface level variations in the same period

crustal structure variations along the nw african continental margin a comparison of new and existing models from wide angle and reflection seismic data abstract deep seismic data represent a key to understand the geometry and mechanism of continental rifting the passive continental margin of nw africa is one of the oldest on earth formed during the upper triassic lower liassic rifting of the central atlantic ocean over 200 ma we present new and existing wide angle and reflection seismic data from four study regions along the margin located in the south offshore dakhla on the central continental margin offshore safi in the northern moroccan salt basin and in the gulf of cadiz the thickness of unthinned continental crust decreases from 36 km in the north to about 27 km in the south crustal thinning takes place over a region of 150 km in the north and only 70 km in the south the north moroccan basin is underlain by highly thinned continental crust of only 6 8 km thickness the ocean continent transition zone shows a variable width between 40 and 70 km and is characterized by seismic velocities in between those of typical oceanic and thinned continental crust the neighbouring oceanic crust is characterized by a thickness of 7 8 km along the complete margin relatively high velocities of up to 7 5 km s have been imaged between magnetic anomalies s1 and m25 and are probably related to changes in the spreading velocities at the time of the kimmeridgian tithonian plate reorganization volcanic activity seems to be mostly confined to the region next to the canary islands and is thus not related to the initial opening of the ocean which was associated to only weak volcanism comparison with the conjugate margin off nova scotia shows comparable continental crustal structures but 2 3 km thinner oceanic crust on the american side than on the african margin

modeling historical climate variability and slope stability this study presents scenario models for historical variations of climate and slope stability a model for historical annual patterns of temperature and rainfall was established on the basis of seasonal proxies a process based spatio temporal model for groundwater variations and slope stability was developed using the gis environment of the software pcraster we applied the slope stability model to study the effects of the different climate scenarios on slope stability for three different hillslopes in the area around bonn germany the findings indicate three climatic phases with different annual temperature and precipitation patterns over the historic period the modeling results show that a climatic scenario representing unstable conditions of a transition from the more humid little ice age to dryer recent climate produces the highest slope instabilities the intensity of this impact however varies with the sensitivity of the geomorphic system i e local landforms and lithology and cannot be generally related to the stability of a specific hillslope more unstable areas are not necessarily more sensitive to climatic changes the location of permeable layers prone to groundwater rise in relation to sensitive layers lower strength and higher gradients higher stress influences the sensitivity of a site with respect to climate changes the presented method is capable of modeling landscape sensitivity to climate change with respect to groundwater controlled landslides

mid miocene propagation of the yellowstone mantle plume head beneath the columbia river basalt source region columbia river flood basalt volcanism is the product of mid miocene distortion of the yellowstone mantle plume head against the precambrian margin of north america the overall migration pattern of columbia river basalt vents reflects northward propagation of the plume head beneath the west southwest migrating north american plate thermal uplift mimics the vent migration over the 1 5 m y of grande ronde basalt extrusion the projected crest of the plume head migrated 105 km 7 cm yr from the chief joseph dike swarm east oortheast into the clearwater embayment where uplift occurred over the same period at a rate of 0 67 mm yr chemical variations reflect progressive melting of the plume and mantle lithosphere followed by the mixing of these components with an enriched source from the overriding craton rapid thickening of the plume head against the cratonic margin led to decompressional melting and magma rise beneath a thin oceanic lithosphere of accreted terranes

reconstructing recent landslide activity in relation to rainfall in the llobregat river basin eastern pyrenees spain abstract a chronology of recent landslides in the upper basin of the llobregat river eastern pyrenees has been reconstructed from technical reports field reconnaissance and dendrogeomorphological analysis the precipitation conditions responsible for triggering and reactivating landslides have been deduced by analysis of rainfall records from two rain gauges located in the area two different rainfall patterns relate to landslide occurrence i without antecedent rainfall high intensity and short duration rains trigger mostly debris flows and shallow slides developed in colluvium and weathered rocks a rainfall threshold of around 190 mm in 24 h initiates failures whereas more than 300 mm in 24 48 h are needed to cause widespread shallow landsliding ii with antecedent rain moderate intensity precipitation of at least 40 mm in 24 h reactivates mudslides and both rotational and translational slides affecting clayey and silty clayey formations in this case several weeks and 200 mm of precipitation are needed to cause landslide reactivation dendrochronological analysis shows that landslide activity in the eastern pyrenees was relatively low between 1926 and 1959 but has since increased significantly with reactivation now occurring about every 3 years

landslide development at the shores of a dam reservoir wloclawek poland based on 40 years of research this article presents results of our 40 year research on dynamics of a deep rotational landslide developed in clay deposits the landslide is located in a lowland within the shoreline of wloclawek reservoir with little water level variation in dobrzyn on the vistula northern poland it is an old landslide which was active also before the construction of the reservoir our research was initiated in 1970 i e when the river vistula was dammed there currently the landslide covers about 20 000 m2 and has a volume of about 160 000 m3 during the 40 years 3 periods of increased landslide activity were observed the first conspicuously nearly 40 increase in the rate of movements within the central landslide was initiated in the early 1970s and lasted till the early 1980s it coincided with the initial filling of the reservoir and the first years of exploitation of wloclawek reservoir the increase in landslide dynamics was a direct effect of hydrological and morphological changes associated with the damming of the river the next 2 periods of increased landslide activity occurred in 2001 2002 and 2010 2011 the latter was the most spectacular displacement within the central landslide it was recorded between december 2010 and february 2011 and reached 10 0 19 4 m after unusually long lasting heavy rainfall in the summer and autumn of 2010 followed by snowmelt and unfavourable changes in air temperature since march 2011 no movements within the landslide have been recorded

impact of piping on gully development in mid altitude mountains under a temperate climate a dendrogeomorphological approach abstract gullies are complex geomorphic systems induced and transformed not only by surface erosion processes but also by subsurface processes such as piping however the transient nature of piping makes this process more difficult to observe and study especially when a pipe roof has totally collapsed this study aims at assessing piping impact on gully initiation and development using dendrogeomorphological analyses which are a novel approach in piping study the survey was carried out in a mountainous area under a temperate climate using the bere nica wyzna catchment in the bieszczady mts eastern carpathians as a case study we estimated the minimum age of pipe collapses and presented the transformation of pipe collapses in order to identify the direction of pipe and gully development we also verified the contribution of piping to gully development by the reconstruction of gully bottom deepening the analysis was based on changes in tree and root wood anatomy in diffuse porous deciduous angiosperm species i e common alder alnus glutinosa and field maple acer campestre the pipe collapses in the piping system studied are at least 19 to 23 27 years old and the pipe roof initially collapsed in the lower sections of the slope above the gully head and the pipe develops up the slope by headward erosion the gully that was analysed in forest had been deepened by piping during several episodes connected with high precipitation events in contrast the pipe located in grasslands collapsed 1 2 years after such events indicating that dense vegetation delays pipe collapse this study shows that dendrogeomorphological analyses based on diffuse porous deciduous angiosperm species may be a useful tool in piping research it provides information on pipe and gully development as well as enabling estimates to be made of the age of pipe collapses

the proximity of hotspots to convergent and divergent plate boundaries an analysis of four different hotspot distributions ranging from morgan s 1972 original list of 19 to vogt s 1981 list of 117 reveals that the hotspots are preferentially located near divergent plate boundaries the probability of this proximity occurring by chance alone is quite remote less than 0 01 for all four hotspot distributions the same analysis also reveals that the hotspots are preferentially excluded from regions near convergent plate boundaries the probability of this exclusion occurring by chance alone is 0 1 or less for three out of the four distributions examined we interpret this behavior as being a consequence of the effects of large scale convective circulation on ascending mantle plumes mantle thermal plumes the most probable source of hotspots arise from instabilities in a basal thermal boundary layer plumes are suppressed from regions beneath convergent boundaries by descending flow and are entrained into the upwelling flow beneath spreading centers plate scale convective circulation driven by subduction may also advect mantle thermal plumes toward spreading centers

the effectiveness of dendrogeomorphic methods for reconstruction of past spatio temporal landslide behaviour abstract dendrogeomorphic methods are in fact frequently used for spatio temporal landslide behaviour reconstruction however their real accuracies have not yet been deeply evaluated the purpose of this study is to evaluate the effectiveness and accuracy of tree ring based methods by comparing them with field monitoring data on landslide behaviours a total of 876 increment cores have been extracted from 219 p sylvestris individuals to reconstruct the past spatio temporal activity of the ubietova landslide 1977 the landslide re activation events recorded within the tree ring series of each tree have been spatially interpolated those data have been compared with the long term field monitoring based on the measured changes in the stabilized geodetic point positions in general the tree ring based spatio temporal landslide evolution revealed a higher landslide activity than the monitoring based one particularly in the lower part of the landslide however higher activity was recorded from the monitoring in the northern part of the upper half of the landslide while approximately 30 of the studied landslide area revealed highly similar normalized values based on both approaches the best fit between the results 80 was in areas with mean cumulative surface displacements of approximately 200 mm monitoring based results and mean event recurrence time of 14 5 years tree ring based results the potential sources of uncertainties that should be considered in future dendrogeomorphic research are the irregular spatial positions and spatial density of trees the physiology of the tree species the inertia of tree growth responses within tree ring sequences and the type of studied landslide

geomorphological pedological and dendrochronological signatures of a relict landslide terrain mt garbatka kamienne mts sw poland abstract in the kamienne mountains the largest concentration of apparently relict landslides in the sudetes range occurs on the northern slopes of mt garbatka mass movements re shaped two adjacent slope hollows and a wide depositional area is located down the valley the main landslide body is nearly 1 km long and 200 300 m wide its flattened surface morphology and the occurrence of large dispersed allochtonous boulders in the distal part suggests a flow like movement initiated by shallow translational slides in the upper slopes the thickness of colluvium determined by an ert survey may reach 10 m geomorphic signatures of mass movement are subdued suggesting that considerable time has elapsed since the origin of the landslide and that large scale mass movements are likely pre holocene in age this is consistent with the results of an extensive soil survey within the landslide body and on the surrounding slopes similarity of soil properties and well developed horizonation of profiles both within the landslide and outside it shows that no major disturbance has taken place during the soil formation period dendrogeomorphological research in turn yielded evidence of numerous growth disturbances recorded in tree rings of norway spruce growing on the landslide body these signals are interpreted that the slope surface is not entirely stable under current environmental conditions flow or creep of landslide material is not very likely given the characteristics of cover materials and it is hypothesized that dendrochronological signals develop in response to ground deformation through piping and throughflow landslide hazard in the valley below mt garbatka appears low at present but to claim complete stability would be premature

geo botanical evidence of late quaternary mass wasting in block field areas of virginia studies of block fields at massanutten mountain virginia document and provide information on the magnitude and frequency of mass movement on these coarse grained slopes block fields which traditionally have been considered relicts of pleistocene climate occur on and downslope from resistant massanutten sandstone in passage creek basin slopes are strewn with boulders and vegetative cover on the open block fields is absent to sparse several block fields were investigated for evidence of recent movement using the degree of lichen growth differences in block weathering and rock fall damaged trees temporal and spatial aspects of geomorphic processes can be inferred through dendrogeochronology corrasion scars and stem ages infer a minimum age for a geomorphic or hydrologic event high flows on passage creek coincided with tree ring determined dates of block field movement although pleistocene periglacial climate may have facilitated original formation of block fields some block fields now continue to spread downslope during intense runoff events present block field mass wasting may be the principal erosional process in these areas of resistant rock

using geochemistry to map mantle flow beneath the lau basin geochemical tracers can be used to map mantle flow beneath the lau basin tonga region over the past 6 m y and constrain the extent and means by which different components contribute to the magmas erupted there helium isotope data track the samoan plume to show that it infiltrated into the northwestern part of the lau basin at 40 mm yr 1 through an opening tear in the pacific plate in contrast to other recent studies our analysis indicates that this plume does not contribute to the arc lavas a louisville plume component is present in the northern tonga arc lavas but this was added from volcaniclastic sediments transported into the arc on the subducting slab and does not require the presence of plume material within the mantle wedge the louisville tracer has been used to infer that the mantle wedge beneath the island arc is downwelling at the rate of 20 40 mm yr 1 owing to viscous drag against the downgoing pacific plate a third geochemical tracer provided by the distinction between indian and pacific mantle indicates that indian mantle has migrated eastward at rates of 45 65 mm yr 1 the inferred rates of migration indicate that the translation of geochemical signatures occurs by mantle flow rather than by the order of magnitude faster movement of partial melts except for the flow in the mantle wedge the directions of mantle flow in this region are unrelated to the overlying plate motions

imaging canary island hotspot material beneath the lithosphere of morocco and southern spain abstract the westernmost mediterranean has developed into its present day tectonic configuration as a result of complex interactions between late stage subduction of the neo tethys ocean continental collision of africa and eurasia and the canary island mantle plume this study utilizes s receiver functions srfs from over 360 broadband seismic stations to seismically image the lithosphere and uppermost mantle from southern spain through morocco and the canary islands the lithospheric thickness ranges from 65 km beneath the atlas mountains and the active volcanic islands to over 210 km beneath the cratonic lithosphere in southern morocco the common conversion point ccp volume of the srfs indicates that thinned lithosphere extends from beneath the canary islands offshore southwestern morocco to beneath the continental lithosphere of the atlas mountains and then thickens abruptly at the west african craton beneath thin lithosphere between the canary hot spot and southern spain including below the atlas mountains and the alboran sea there are distinct pockets of low velocity material as inferred from high amplitude positive sub lithospheric conversions in the srfs these regions of low seismic velocity at the base of the lithosphere extend beneath the areas of pliocene quaternary magmatism which has been linked to a canary hotspot source via geochemical signatures however we find that this volume of low velocity material is discontinuous along strike and occurs only in areas of recent volcanism and where asthenospheric mantle flow is identified with shear wave splitting analyses we propose that the low velocity structure beneath the lithosphere is material flowing sub horizontally northeastwards beneath morocco from the tilted canary island plume and the small localized volcanoes are the result of small scale upwellings from this material

spatio temporal analysis of a complex landslide in the northern apennines italy by means of dendrochronology dendrochronology is used to determine the spatial and temporal development of movements in a complex landslide located in the northern apennines the analysis of trees growing on the landslide body enabled us to date their colonisation pattern which starts from the 1920s and increases mainly after 1950 since then sampled trees recorded with growth anomalies the movements involving the landslide body in 1956 1957 1982 1983 1990 1995 and 1998 these movements are reactivations of the main landslide that probably occurred in the last decades of the 19th century in 1980 trees on the upper landslide body were involved in a rock fall due to the expansion of the main scarp microsections cut out from selected tree ring sequences allowed seasonal dating of the highlighted movements which mostly occurred in early spring meteorological and seismic time series were analyzed in order to relate them with reactivations and to search for correlations and triggering events the seismic activity although characterized by low magnitudes could be able either to trigger the movements 1990 or to destabilize the ground where rainfalls could have been playing the first role in triggering the reactivation probably in 1982 1983 and 1995 the other reactivations seem to be linked either to long lasting rainfalls or to monthly rainfall peaks mostly following dry periods

debris flows rainfall thresholds in the apennines of emilia romagna italy derived by the analysis of recent severe rainstorms events and regional meteorological data abstract recent severe rainstorms events in october 2014 and september 2015 triggered more than a hundred debris flows in the western part of the apennines of emilia romagna italy in this work we tested a novel method to define debris flows rainfall thresholds for the 2014 and 2015 rainstorms which have been used as reference events and to extend these results across the apennines of emilia romagna making use of long term rainfall data of the regional raingauges network results are compared for validation to rainfall rates recoded during other past rainstorm debris flows events which have been used as validation events at first the method involves a spatial discriminant analysis between the spatial distribution of debris flows and the high frequency weather radar rainfall data for the 2014 and 2015 reference events the analysis defines rainfall cutoff values over rainfall durations from 30 to 6 h related to verification indices in the roc curves which are used as debris flows rainfall thresholds exceedance ratios are calculated between the computed rainfall thresholds and the rainfall rates at 10 years return periods at corresponding rainfall durations computed for raingauges located in the areas affected by the 2014 and 2015 events the ratios are then used as multipliers of the rainfall rates at 10 years return periods over rainfall durations from 30 to 6 h calculated for all other raingauges in the regional study area to spatialize thresholds calculation to the regional scale the computed thresholds are interpolated across the apennines of emilia romagna the research resulted in the assessment of two levels debris flows rainfall thresholds curves which seem to be adequate to discriminate rainfall rates recorded during past debris flows events used for validation discussion evidences advantages and limits of our approach compares results to existing debris flows thresholds and highlights their possible use in a multi stage warning procedure at regional scale

spatial and temporal analysis of mass movement using dendrochronology tree growth and inclination on sloping land is affected by mass movement suitable analysis of tree growth and tree form can therefore provide considerable information on mass movement activity this paper reports a new automated method for studying the temporal and spatial aspects of mass movement activity ringwidth data from only a few cores per tree are required the method uses filtering techniques and statistical time series analysis preliminary results for two landslides in the barcelonnette area of the french alps show a relative stability of movement activity over the last hundred years no trend and short periodicity six to seven year periods of mass movement activity the advantages of the method over other mostly visual methods are its clearness flexibility repeatability and rapidity however further testing is needed to examine its reliability

experimental investigation on progressive deformation of soil slope using acoustic emission monitoring abstract the deformation process of soil slopes observed during a landslide can have progressive characteristics which can be quantified through acoustic emission ae monitoring a model test is designed based on the geological model of a translational landslide and experiments are conducted to reproduce the three stage deformation process of a soil slope the deformation process of progressive landslides is described using equations and an entire loading process is realized using a programmable logic controller plc the maximum velocity of a sliding body is measured to be approximately 6 mm s with the final displacement exceeding 210 mm the ae deformation and mechanical measurements of the entire process are compared to comprehensively evaluate the evolution behavior of progressive soil landslides the experiments demonstrate that ae rates can linearly quantify slope velocity as well as help quantify slope acceleration a copper tube and an aluminum tube are compared as different waveguides and the quantitative relationship between the ae and deformation obtained by the active copper waveguide is found to be more distinct the experiments also show that the acceleration of a slope can be effectively used as a discriminant index of progressive landslides which has the potential to be applied in field monitoring

lichen dating of coseismic landslide hazards in alpine mountains abstract studies of rockfalls and block slides provide insight about seismic shaking hazards in alpine mountains subject to earthquakes large samples of the longest axis of the largest lichen on each block can be used to identify regional landslide events lichen size distributions for many sites cluster consistenly at the same sizes the coseismic rockfall lichenometry model can be used to 1 date and locate prehistorical earthquakes 2 document regional frequency of earthquakes and 3 describe regional patterns of seismic shaking determination of colonization time great growth phase and especially uniform phase rates of lichen growth are essential for dating regional landslide events rocks that tumble downhill during historical earthquakes allow accurate calibration of the growth rate for rhizocarpon subgenus rhizocarpon these plentiful fresh substrates are dated to their day of formation an initial calibration of uniform growth rate based on historical and tree ring dated landslides was fine tuned by assigning earthquake dates to mean values of lichen size peaks for regional rockfall events that increase in abundance towards epicenters of historical earthquakes calibration for each new site is unnecessary in the southern alps of new zealand and in the sierra nevada of california because several species of yellow rhizocarpons within each climatic region have constant growth rates that are independent of altitude or substrate lithology

climate change increases frequency of shallow spring landslides in the french alps in this contribution past process activity is reconstructed on seven landslide bodies of the riou bourdoux catchment southeastern french alps based on an unusually dense data set of 3036 tree ring series extracted from 759 conifers we provide evidence for 61 landslide reactivations since a d 1898 based on logistic regressions and threshold analyses of monthly rainfall data and temperature anomalies we determine that the combination of snow rich winters and positive temperature anomalies in spring enhanced snowmelt seems to have driven landslide reactivations in the past since the early 1990s however landslide reactivations clearly have been on the rise and thereby exhibit excessive and unprecedented rates of activity 12 5 events per 10 yr at the scale of the riou bourdoux catchment from the data evidence exists for a shift from snowmelt induced landslides controlled by winter precipitation to reactivations controlled by spring temperatures therefore this contribution also adds evidence to the hypothesis that climate change and related warmer springs could further enhance landslide activity in the course of the 21 st century

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

evidence for slab rollback in westernmost mediterranean from improved upper mantle imaging this work is funded by the picasso project nsf grant ear 0808939 the deployment and data processing for spanish stations was funded by consolider ingenio 2010 project topo iberia csd2006 00041 as well as alert es cgl2010 19803 c03 02

plume capture by divergent plate motions implications for the distribution of hotspots geochemistry of mid ocean ridge basalts and estimates of the heat flux at the core mantle boundary abstract the coexistence of stationary mantle plumes with plate scale flow is problematic in geodynamics we present results from laboratory experiments aimed at understanding the effects of an imposed large scale circulation on thermal convection at high rayleigh number 106 ra 109 in a fluid with a temperature dependent viscosity in a large tank a layer of corn syrup is heated from below while being stirred by large scale flow due to the opposing motions of a pair of conveyor belts immersed in the syrup at the top of the tank three regimes are observed depending on the ratio v of the imposed horizontal flow velocity to the rise velocity of plumes ascending from the hot boundary and on the ratio of the viscosity of the interior fluid to the viscosity of the hottest fluid in contact with the bottom boundary when v 1 and 1 large scale circulation has a negligible effect on convection and the heat flux is due to the formation and rise of randomly spaced plumes when v 10 and 100 plume formation is suppressed entirely and the heat flux is carried by a sheet like upwelling located in the center of the tank at intermediate v and depending on established plume conduits are advected along the bottom boundary and ascending plumes are focused towards the central upwelling heat transfer across the layer occurs through a combination of ascending plumes and large scale flow scaling analyses show that the bottom boundary layer thickness and in turn the basal heat flux q depend on the peclet number pe and when 10 q pe1 2 and when 1 q pe 1 3 consistent with classical scalings when applied to the earth our results suggest that plate driven mantle flow focuses ascending plumes towards upwellings in the central pacific and africa as well as into mid ocean ridges furthermore plumes may be captured by strong upwelling flow beneath fast spreading ridges this behavior may explain why hotspots are more abundant near slow spreading ridges than fast spreading ridges and may also explain some observed variations of mid ocean ridge basalt morb geochemistry with spreading rate moreover our results suggest that a potentially significant fraction of the core heat flux is due to plumes that are drawn into upwelling flows beneath ridges and not observed as hotspots

assessment of shallow landslide susceptibility by means of multivariate statistical techniques several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution a data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes the performance of principal component analysis t test and one way test allowed a preliminary selection of the most significant variables which were used as input variables for the discriminant analysis the function obtained has classified successfully 88 5 per cent of the overall slope population and 95 6 per cent of the failed slopes slope gradient watershed area and land use appeared as the most powerful discriminant factors a landslide susceptibility map based on the scores of the discriminant function has been prepared for ensija range in the eastern pyrenees an index of relative landslide density shows that the results of the map are consistent copyright 2001 john wiley sons ltd language en

the fate of the juan de fuca plate implications for a yellowstone plume head beneath the pacific northwest the juan de fuca plate a remnant of the farallon plate continues subducting beneath the north american continent to the east of the cascadia subduction zone lies the yellowstone hotspot track the origins of this track can be traced back to the voluminous basaltic outpourings in the columbia plateau around 17 ma if these basalts are the result of a large melting anomaly rising through the mantle to the base of the north american continent such as a mantle plume head the anomaly would need to punch through the subducting juan de fuca slab here we use teleseismic body wave travel time tomography to investigate the fate of the subducted slab and its possible interaction with a plume head our dataset is derived from the oregon array for teleseismic study oats deployment in oregon and all other available seismic data in this region during the same period in our jdf07 models we image the subducted juan de fuca plate in the mantle east of the cascades beneath oregon where the slab has not been imaged before to a depth of 400 km but no deeper the slab dips similar to 50 degrees e and has a thickness of similar to 75 km immediately beneath the slab we image a low velocity layer with a similar geometry to the slab and extending down to at least similar to 575 km depth in the v model the total length of the high velocity slab is similar to 660 km about 180 km longer than the estimated length of slab subducted since 17 ma assuming similar slab geometry to today this 180 km length of slab would reach similar to 60 km depth comparable to the thickness of continental lithosphere we propose that the absence of the slab below 400 km today is due to the arrival of the yellowstone plume head similar to 17 ma which destroyed the juan de fuca slab at depths greater than the thickness of the continental lithosphere given this scenario the low velocity anomaly beneath the slab is likely the remnant plume head material which has been pulled down by traction with the subducting plate the amplitude of the observed low velocity anomaly is comparable with that expected for plume head material 100 300 degrees c hotter than the surrounding asthenosphere c 2007 elsevier b v all rights reserved

control of slab width on subduction induced upper mantle flow and associated upwellings insights from analog models the impact of slab width w i e trench parallel extent on subduction induced upper mantle flow remains uncertain we present a series of free subduction analog models where w was systematically varied to upscaled values of 250 3600 km to investigate its effect on subducting plate kinematics and upper mantle return flow around the lateral slab edges we particularly focused on the upwelling component of mantle flow which might promote decompression melting and could thereby produce intraplate volcanism the models show that w has a strong control on trench curvature and on the trench retreat subducting plate and subduction velocities generally in good agreement with previous modeling studies upper mantle flow velocity maps produced by means of a stereoscopic particle image velocimetry technique indicate that the magnitude of the subduction induced mantle flow around the lateral slab edges correlates positively with the product of w and trench retreat velocity for all models an important upwelling component is always produced close to the lateral slab edges with higher magnitudes for wider slabs the trench parallel lateral extent of this upwelling component is the same irrespective of w but its maximum magnitude gets located closer to the subducting plate in the trench normal direction and it is more focused when w increases for w 2000 km the upwelling occurs laterally in the trench parallel direction next to the subslab domain and the mantle wedge domain while for w 2000 km it is located only next to the subslab domain and focuses closer to the trench tip because of stronger poloidal flow in the mantle wedge extending laterally

scaling properties of faults and their populations abstract faults are natural shear fractures which while active and growing are the source of seismicity and deformation within the brittle upper crust of the earth and when dead are the relicts of past such deformation results are now conclusive that fault growth is a self similar process in which the total geological slip scales linearly with fault length with a proportionality constant typically 10 2 more limited data also suggest linear scaling with fault length of the process zone size and consequently fracture energy these observations as well as the characteristic slip profiles of faults are broadly consistent with a dugdale barenblatt type elastic plastic model of crack propagation the scaling parameters are not universal but depend on rock properties secondary fault structures such as the width of the cataclasite zone and of the process zone wake the zone of enhanced brittle deformation surrounding the fault also exhibit linear scaling with fault length and slip fault populations have often been found to be fractal exhibiting a power law fault size distribution similar observations have been made for the scaling laws governing veins and joints the primary difference is that the proportionality constant between aperture and length is 10 3 about a tenth that of faults reflecting the lower strength of rock in tension than in shear

bifurcation of the yellowstone plume driven by subduction induced mantle flow in the northwestern united states two neighbouring volcanic chains the snake river plain and high lava plains decrease in age in opposing directions laboratory experiments show that diverging volcanic chains can form where vigorous mantle circulation beneath a subduction zone causes an upwelling mantle plume to split into two

rheology and density of glucose syrup and honey determining their suitability for usage in analogue and fluid dynamic models of geological processes abstract analogue models of lithospheric deformation and fluid dynamic models of mantle flow mostly use some kind of syrup such as honey or glucose syrup to simulate the low viscosity sub lithospheric mantle this paper describes detailed rheological tests and density measurements of three brands of glucose syrup and three brands of honey additional tests have been done for one brand of glucose syrup that was diluted with water to various degrees 2 5 and 10 by weight the rheological tests have been done to test the effect of shear strain shear rate and temperature on the dynamic viscosity of the syrup the results show that the viscosity of all glucose syrups and honeys is independent of shear strain i e no strain hardening or softening the viscosity of the glucose syrups is independent of shear rate i e linear viscous or newtonian in the range 10 4 10 0 s 1 with stress exponents that are almost identical to one n 0 995 1 004 all the honeys show a very weak but consistent decrease in viscosity with increasing shear rate of 7 14 from 10 3 to 100 s 1 and have stress exponents more distinct from one n 1 007 1 026 all syrups have a viscosity that is strongly dependent on temperature in the range 0 50 c where viscosity decreases with increasing temperature such decrease can be fitted with exponential and arrhenius functions with the latter giving the best results furthermore the viscosity of glucose syrup decreases approximately exponentially with increasing water content oscillation tests indicate that the rheology of all the syrups is entirely dominated by viscous behaviour and not by elastic behaviour at frequencies of 10 3 102 hz finally the density investigations show that the density of glucose syrup and honey decreases approximately linearly with increasing temperature in the range 10 70 c with coefficients of thermal volumetric expansion at 20 c of 3 89 3 95 10 4 c 1 and 4 57 4 81 10 4 c 1 for glucose syrup and honey respectively the new results demonstrate that glucose syrups and to a lesser degree honeys are well suited for usage in analogue and fluid dynamic experiments to represent linear viscous strain independent and shear rate independent rheologies to model geological processes glucose syrups have the added advantage of being more transparent than honeys allowing for accurately resolving and quantifying flow patterns in the fluid during a model run

the dynamics of off axis plume ridge interaction in the uppermost mantle two decades of geochemical and geophysical observations have led to the plume channel model whereby buoyant off axis mantle plumes feed and interact with diverging plates at mid ocean ridge axes which act as sinks of upper mantle material here we present results from two dimensional 2 d numerical experiments which incorporate the essential physics and fluid dynamic aspects of the plume ridge upper mantle system in order to test the feasibility of this plume ridge interaction model specifically experiments test the relative importance of physical effects such as strong viscosity variations and thermal and chemical buoyancy forcing in plume ridge dynamics results indicate that both transient and steady state connections may be established between off axis plumes and ridges for a range of realistic mantle conditions the presence of a strongly sloping rheological boundary layer rbl is a necessary condition for long term communication between an off axis buoyant upwelling and a spreading ridge the flux of buoyant material to the ridge is also shown to increase with increasing plume to mantle density contrast decreasing plume viscosity and smaller plume ridge separation distances plume ridge interaction regimes are defined based on the competing effects of plate driven and buoyancy driven flow thermal erosion of the viscous lithosphere strongly inhibits long term plume ridge interaction by enhancing the plates ability to deflect the plume both head and conduit away from the ridge axis

slope instability in nicaragua triggered by hurricane mitch distribution of shallow mass movements the heavy rains associated with hurricane mitch triggered off a number of slope instability processes in several central american countries different instability processes have been acknowledged for the various mountainous regions of nicaragua an enormous movement of the casita volcano slopes resulted in numerous deaths and some deep movements have been reactivated on the other hand numerous shallow mass movements and debris flows have given rise to great material loss throughout a large part of nicaraguan mountains

how different are the results acquired from mathematical and subjective methods in dendrogeomorphology insights from landslide movements abstract knowledge of past landslide activity is crucial for understanding landslide behaviour and for modelling potential future landslide occurrence dendrogeomorphic approaches represent the most precise methods of landslide dating where trees annually create tree rings in the timescale of up to several hundred years despite the advantages of these methods many open questions remain one of the less researched uncertainties and the focus of this study is the impact of two common methods of geomorphic signal extraction on the spatial and temporal results of landslide reconstruction in total 93 norway spruce picea abies l karst trees were sampled at one landslide location dominated by block type movements in the forefield of the orlicke hory mts bohemian massif landslide signals were examined by the classical subjective method based on reaction compression wood analysis and by a numerical method based on eccentric growth analysis the chronology of landslide movements obtained by the mathematical method resulted in twice the number of events detected compared to the subjective method this finding indicates that eccentric growth is a more accurate indicator for landslide movements than the classical analysis of reaction wood the reconstructed spatial activity of landslide movements shows a similar distribution of recurrence intervals ri for both methods the differences maximally 30 of the total ri ranges in results obtained by both methods may be caused by differences in the ability of trees to react to tilting of their stems by a specific growth response reaction wood formation or eccentric growth finally the ability of trees to record tilting events by both growth responses in their tree ring series was analysed for different decades of tree life the highest sensitivity to external tilting events occurred at tree ages from 70 to 80 years for reaction wood formation and from 80 to 90 years for eccentric growth response this means that the ability of p abies to record geomorphic signals varies with not only eccentric growth responses but also with age

regional tree ring based chronology of landslides in the outer western carpathians abstract landslides are a type of mass wasting and denote any downslope movement of soil and rock under the influence of gravity as such they can represent a dangerous natural hazard process especially in case that they affect inhabited areas or transport infrastructure because the occurrence of landslides is typically favoured by terrain and lithological conditions the process is frequently concentrated in relatively small isolated regions exhibiting suitable initial conditions of terrain instability extensive regional assessments of landslide activity have been used in the past to uncover common triggers and process patterns mostly in the aftermath of large regional disasters by contrast however regional reconstructions of past landslide activity have not been realized with dendrogeomorphic techniques and with the aim to date past landslide histories over extended time periods and with annual dating precision this study therefore aims at disentangling landslide dynamics at the regional scale covering ca 600 km2 by using growth ring records of trees that grow on active landslides the studied area of the host nsko vsetinska hornatina mts central europe is well known for its high landslide activity but has so far been lacking a detailed chronology of past events to this end we dated past activity on 26 landslide bodies using tree ring series from 1322 disturbed trees to reconstruct 327 landslide reactivations during the last century the reconstructed landslide database allowed correlations between landslide types and their frequencies or occurrence as well as inferences between selected morphometric parameters with landslide frequency and magnitude we also observe periods of increased landslide activity 1940s 1960s 1980s and 1990s and events of regional importance e g 1961 1985 and 1997 as well as a significant decrease in landsliding during the last two decades

the temporal stability and activity of landslides in europe with respect to climatic change teslec main objectives and results abstract the major aim of the european project the temporal stability and activity of landslides in europe with respect to climatic change teslec was to investigate the interrelationship between landslides climate and time the research was focused on three main objectives 1 developing criteria for the recognition of landslides 2 reconstructing past distributions of landslide incidents and their relationship to climatic change parameters and 3 developing a hydrological and slope stability modelling framework using different test sites the results of the project are related to these major objectives and include 1 a technical manual for landslide recognition 2 records of landslide activity and 3 an evaluation of different hydrological and slope stability models landslide activity since 1950 has been generally high at all test sites in some areas there has almost been a continuous activity observed since the beginning of the monitoring the records before 1950 are incomplete and probably indicate a lack of data rather than a lack of landslide activity whether the observed active landslides are carrying a climate signal cannot be stated for all test sites with high confidence since some relationships between climate and landslides are uncertain thus for the present the complexity of the relationships between climate and landsliding seems to make it not feasible to establish universal laws all over europe on the other hand it was possible to establish for some areas a cumulative rainfall duration threshold for the reactivation of landslides future scenarios of regional precipitation were derived from downscaled general circulation model gcm experiments and used within simple slope hydrological and slope stability models the evaluation of hydrological and slope stability models shows that physically based models are not always the best solution due to the model complexity and data requirements for shallow landslides more simple tank models are sometimes the better alternative future model development should strengthen considerations of fissure flow sudden changes in permeability larger landslide volumes and complex landslide topography

hydrometeorological triggers of periglacial debris flows in the zermatt valley switzerland since 1864 1 the triggering of debris flows depends on a critical combination of available unconsolidated material and water supply in periglacial environments debris flows are generally triggered by liquefaction of loose material in a channel or by progressive erosion during a large release of water here we link an unusually dense and highly resolved database on periglacial debris flows with meteorological records dating back to ad 1864 to reconstruct 150 yr of rainstorms that triggered debris flows at high elevation sites source area elevations ranging from 2000 to 4545 m a s l in the swiss alps analysis is based on a tree ring derived frequency series of debris flows from eight torrents as well as on daily records from three meteorological stations and runoff data from four river gauging stations results show that the debris flow season at these high altitude sites now is much longer may to october than it used to be in the late nineteenth century when activity was limited to june september debris flows early in the season are generally triggered by lower rainstorm totals 20 mm day than those occurring later in the season because early season snowmelt adds considerable amounts of water to the system and therefore facilitates debris flow formation debris flows in may june july and august are triggered primarily by short duration high intensity rainstorms local thunderstorms whereas late season september october debris flows are commonly related to longer lasting advective rainstorms

triggering threshold precipitation and soil hydrological characteristics of shallow landslides in granitic landscapes abstract sierra de gredos a mountain range in central spain is prone to the occurrence of shallow landslides which can transform into sediment laden flows as demonstrated by geomorphologic evidence the analyses of these complex processes require reliable design tools for predicting thresholds of triggering precipitation in order to assess the susceptibility characteristics in the sierra de gredos there is a lack of knowledge concerning how weathering mantle properties vary spatially and what effects these spatial patterns have on infiltration surface runoff and shallow subsurface flow in this context this paper is focused on the hydrogeomorphic characterization of a shallow landslide that occurred on december 17 1997 the generalized quasi dynamic model gqdm was implemented to approach the critical rainfall intensity set for different durations and to establish the intensity duration id threshold to this purpose field and laboratory methods such as seismic refraction tomography srt time domain reflectometry tdr and geotechnical tests were applied the use of these field investigations and their combination with the gqdm have allowed us to provide a detailed description of the behavior of the catchment and reproduce the pattern of instability generated by an intense storm which triggered the 1997 shallow landslide furthermore this threshold can be used as a predictive tool for hazard prevention

dynamic features and effects of rainfall on landslides in the three gorges reservoir region china using the xintan landslide and the large huangya landslide as the examples the study area is located in three gorges reservoir region china over 200 landslides have been monitored over a number of years with their behavior being compared to the effective rainfall database for the study area analysis of the available data indicates that the occurrences of landslides in this region are controlled by rainfall whose intensity and rainfall processes are the most important dynamic factors in determining the stability of slopes therefore the relationship between rainfall and the movement of typical landslides has been specifically analyzed for the xintan landslides and the large huangya landslide by using the loading unloading response ratio parameter of rainfall the result of this study indicates that the mutation of the loading unloading response ratio of rainfall of the xintan landslide and the large huangya landslide in the three gorges reservoir region china occurred just before their destabilization which shows that the loading unloading response ratio of rainfall and its changing feature can be taken as a precursor for the landslides induced by rainfall

dynamics and scaling characteristics of shear crack propagation a model for a description of a shear crack fault propagation is proposed on the basis of the unification of continuum damage and fracture mechanics with ideas of fracture models for random media energy release linked with local failures of elements as a result of evolution of fracture processes at lower scale levels stimulated by the stress concentration in the vicinity of the fault is treated as a seismicity source 2d simulations are performed for analysis of the effect of the size of pre existing fault on characteristic features of rupture evolution scaling including multifractal character of crack propagation and of respective energy release is shown

research on the displacement response ratio of groundwater dynamic augment and its application in evaluation of the slope stability on the basis of systematic analysis on the motivation and mechanism of displacement and destabilization of the water induced landslides this paper completes a study on the relationship between groundwater dynamic effect laws and displacement response characteristics in the process of the colluvial landslide stability evolution it is found that the displacement and destabilization of landslide are directly controlled by the underground water level variation and also there exists one to one corresponding relation between the deformation of landslide and the groundwater level variation on the basis of the results above the underground water level increment and the corresponding deformation variation are taken to be as the dynamic load parameter of landslide and the dynamic incremental displacement response parameter respectively then the displacement dynamic appraisal parameter and prediction model of the groundwater dynamic incremental displacement response ratio are determined in term of the basic principle of elastic plastic mechanics in this paper meanwhile taking the typical colluvial landslide in the three gorges reservoir area xintan landslide as an example the values and changing rule of the groundwater dynamic incremental displacement response ratio parameter of the a3 and b3 monitoring points on this landslide are obtained by means of the groundwater dynamic incremental displacement response ratio prediction model finding that the change rule of the dynamic incremental displacement response ratio time curve is consistent basically with the dynamic stability evolutional law of the actual slope the research results show that the groundwater dynamic incremental displacement response ratio prediction model can be used to forecast the kinetics of displacement for this slope and this method has widely theory and extensive practicality

modelling a viscous rock joint activated by rainfall application to the la clapiere landslide abstract the continuous evolution of sliding rock masses activated by rainfall combined with snowmelt will be discussed in this paper the effects of precipitation on slip velocities during the periods separating failure events have already been studied in the literature by means of either pure statistical approaches or sophisticated numerical codes a simple schematic model will be presented in this paper based on a crude physical and geometrical simplification of the rock mass hydromechanical system this model enables simulating the correlations between rainfall snowmelt data and slip velocities with relative efficiency this model may be considered as an intermediate tool between purely statistical and more sophisticated numerical models moreover it is potentially useful for assessing the stability of civil engineering and open pit mining slopes

contribution of dendrochronology to the determination of magnitude frequency relationships for landslides abstract the determination of magnitude frequency m f relationships is necessary for landslide hazard assessment ideally this is achieved by using inventories of past landslide events recorded by technical units or aerial photo interpretation however direct sources of landslide data are often unavailable dendrogeomorphological techniques allow us to determine the frequency of events but few attempts have been made to estimate landslide magnitude by analysing the spatial distribution of disturbed trees this paper addresses m f determination for rockfalls debris flows and complex slides obtained by dendrogeomorphology the cases presented require the appropriate understanding of both the geomorphological context and the disturbance caused by landslide motion on trees both small and large rockfalls can be identified and dated by reconstructing the trajectories in the forest stand the larger the rockfall size the longer the path the higher the number of affected trees and the greater the area of deposition of rock fragments the area of damaged trees is proposed as an indicator of the rockfall magnitude the frequency and extent of a series of debris flows were reconstructed by mapping their deposits using relative dating criteria and by dating damaged trees local and global mudslide reactivations were deduced by sampling various tree generations and by analysing the location of the disturbed trees in the landslide units magnitude cumulative frequency curves were determined for the three cases

dynamics of subduction and plate motion in laboratory experiments insights into the plate tectonics behavior of the earth 1 three dimensional laboratory experiments have been designed to investigate the way slab bearing plates move during subduction inside the mantle in our experiments a viscous plate of silicone lithosphere subducts under its negative buoyancy in a viscous layer of pure honey mantle varying thickness width viscosity and density of the plate and mantle three characteristic modes of subduction are observed a retreating trench mode mode i a retreating trench mode following a transient period of advancing trench mode ii and an advancing trench mode mode iii these modes are characterized by different partitioning of the amount of subduction into plate and trench motion our experiments show that the velocity of subduction can be modeled by the dynamic interaction between acting and resisting forces where lithospheric bending represents 75 95 of the total resisting forces however our experimental results also show the impossibility to predict a priori the plate velocity only from the velocity of subduction without considering trench migrations we find experimentally that the lithospheric radius of curvature which depends upon plate characteristics stiffness and thickness and the mantle thickness exerts a primary control on the trench behavior our results suggest that the complexity of the style of subduction could be controlled by geometrical rules of a plate bending inside a stratified mantle the earth system is in the crucial range for the interplay between the rigidity of the plate and the mantle stratification this setting may be the responsible for the complexity of the past and present tectonic styles

investigation of the hsien du shan rock avalanche caused by typhoon morakot in 2009 at kaohsiung county taiwan abstract the hsien du shan rock avalanche at kaohsiung county taiwan was triggered by heavy rainfall brought by typhoon morakot in 2009 heavy rainfall began on the day of august 6 and continued to the morning of august 9 when the slope failure and landslide occurred in this post event investigation physical mechanical and hydraulic properties of the rocks soils at this large landslide site are evaluated the in situ hydraulic conductivity of the soils at the source area was found to be too low k 1 48 10 6 m s for rainfall to vertically infiltrate to the deep sliding surface which was found to have a maximum depth of 85 6 m the post failure simulations using discontinuous deformation analysis dda suggest that the geometry of the sliding surface governs the failure behavior and two continuous progressing failures likely occurred at the beginning of the hsien du shan rock avalanche slope deformation was observed by the local residents before the hsien du shan rock avalanche occurred as a geomorphologic precursor in addition water accumulation along the sliding surface governs the behavior of the sliding surface therefore in the future an early warning system of a rock avalanche can be developed by simultaneously applying high resolution airborne lidar to detect slope deformation and using geo electric measurements to image the infiltration of surface water to the sliding surface

relationship between rain and or meltwater pore water pressure and displacement of a reactivated landslide abstract in order to clarify the relationship between rain and or meltwater mr pore water pressure and landslide displacement continuous monitorings were conducted at a reactivated landslide comprised mainly of weathered mudstone of tertiary in age an exponential relationship was found between the total amount of mr at each event and the amount of pore water pressure increment integrated by time impulse of pore water pressure in addition as the total mr increased the difference between the minimum and maximum values of pore water pressure for each event fluctuation range of pore water pressure also increased but the intensity of mr had little effect on the fluctuation range of pore water pressure the correlation coefficient for the fluctuation range of pore water pressure and cumulative landslide displacement and that for the impulse of pore water pressure and cumulative displacement were similar but were only 0 57 to 0 66 on the other hand the correlation coefficient for the total mr and cumulative landslide displacement was large 0 65 0 69 cumulative landslide displacement was very highly correlated with effective mr which shows the estimated water content in the ground for a half life period of 4 days and correlation coefficients were 0 89 0 92 thus the displacement characteristics of this reactivated landslide which has a long history of landsliding can be explained using the hydrological factor of water content rather than the hydraulic characteristics of pore water pressure

dendrogeomorphological analysis of mass movement a technical note on the research method dating of mass movement events by examining the course of eccentricity of the annual rings of trees inclined as a result of these movements can be a problem in the case of multiple inclined trees showing compound trunk curvature and complex reaction wood these problems however can be solved when sampling of ring width cores is based on accurate analysis of the form of the trunk

regional scale high plasticity clay bearing formation as controlling factor on landslides in southeast spain complex landslides in clay bearing sediments are investigated in two moderate relief regions of southeast spain both regions more than 100 km apart show landslides affecting the same flysch formation which outcrops widely in the central and western betic cordillera along the contact between the external south iberian domain and internal alboran domain zones intense rainfall episodes can be considered as the main triggering factor for slope failures in these two areas we have chosen two landslides diezma and riogordo landslides one from each area of study to investigate their morphological and geotechnical features in order to establish the relative importance of the different controlling factors from a kinematic point of view the two features studied in detail can be referred as to rotational failures evolving downhill to slow earthflows the movement was concentrated on several surfaces developed on a clay rich layer mostly constituted by smectite this clay mineral is of critical relevance to the mechanical behaviour of soils and flysch like formations being very consistent at dry conditions but rapidly losing its strength at wet conditions thus softened smectite rich clay layers with high water contents can approach the properties of a lubricant which in turn can be critical for slope stability in addition to their high plasticity these clays have a high swelling potential which can induce significant vertical overpressure thus reducing even more the strength properties of the flysch formation in southeast spain a region with a mediterranean rainfall regime slope stability can be seriously influenced by the presence of these smectite rich clay layers in a formation of regional extent as is the case of the flysch formation therefore this lithologically controlled factor should be taken into account when evaluating landslide hazard in the betic cordillera

measuring medium term sheet erosion in gullies from trees a case study using dendrogeomorphological analysis of exposed pine roots in central iberia the assessment of gully erosion poses a great challenge because of the complexity and connectivity of the geomorphic processes involved this study focuses on the quantification of sheet erosion rates in a set of slope gullies located on the northern piedmont of the guadarrama mountains spanish central system in order to delineate accurately the gully areas in which sheet erosion was predominant the hydrologic erosion response unit hru eru approach was used and a dendrogeomorphological analysis of exposed tree roots was carried out to quantify sheet erosion rates in one selected hru eru identification of the first year of exposure by erosion from anatomical criteria was therefore critical the 29 samples taken were prepared for anatomical analysis and cross dated anatomical analysis of the samples showed a reduction in the lumen area of earlywood tracheids following root exposure and also in most cases a slight increase in growth rings moreover at the end of the ring latewood tissue and visible annual borders were very clearly defined by several rows of thick walled tracheids a non parametric test was used on the findings derived from this qualitative analysis to objectify determination of the first year of exposure estimates of sheet erosion were obtained by dividing the height of eroded soil by the number of years that each root was exposed the mean value of soil erosion for the entire study site was then determined from statistical inference using this procedure a range of sheet erosion rates between 6 2 and 8 8 mm y 1 125 2 and 177 8 t ha 1 year 1 was obtained for the dominant hru eru of these gullies in central iberia these estimates of eroded soil thickness were adjusted based on the recent finding that root anatomical changes occur prior to their exposure by erosion

application of the shetran basin scale landslide sediment yield model to the llobregat basin spanish pyrenees the first application of the shetran basin scale landslide erosion and sediment yield model is carried out for a major landsliding event in the upper 505 km2 of the llobregat basin in the eastern spanish pyrenees in november 1982 the model simulates the spatial distribution of shallow landslides and their sediment yield acknowledging uncertainty in the model parameter evaluation the aim of the application was not to reproduce the observed occurrence of landslides as accurately as possible with one simulation but to bracket the observed pattern with several simulations representing uncertainty in the key input conditions bounds on the landslide simulations were thus determined as a function of uncertainty in the vegetation root cohesion used in the model factor of safety calculations the resulting upper bound considerably overestimates the observed pattern 17 000 landslides compared with an observation of around 700 but it reproduces several of the principal clusters in the observed pattern the lower bound contains around 500 landslides the sediment yield estimates 2670 14 630 t km 2 are comparable to measurements elsewhere in the pyrenees for extreme events the results demonstrate an ability to simulate the basin scale landslide response to a rainfall event and the resulting sediment yield they also highlight the need for further research in setting the uncertainty bounds and in avoiding large overestimates of landslide occurrence arising in part from a current inability to model small scale controls for a basin of the given size copyright 2006 john wiley sons ltd

reconstruction of landslide movements using digital elevation model and electrical resistivity tomography analysis in the polish outer carpathians abstract landslides are a major threat to the environment infrastructure and human activities especially in mountainous and hilly areas it is therefore important to accurately identify the mass movements triggering these mechanisms this paper presents the impacts of lithotectonic conditions on the formation of mass movements on the example of the landslide that is located in the northern part of the polish outer carpathians in the area of the research the ratio of the total area of landslides to the surface of the area reaches even 20 the interpretation of a high resolution digital elevation model dem electrical resistivity tomography ert and fieldwork results allowed for the reconstruction of the landslide movements and dividing them into two areas the western one dominated by rotational movement and the eastern one featuring rotational and translational movement it was found that the eastern part is more active now as it probably was also in the past which might have resulted from the lithotectonic conditioned or from the impact of the flowing waters of the dunajec river moreover in the eastern part of the landslides a small sized ridge 55 m 25 m was identified which shows greater stability in comparison with the colluvium that surrounds it in order to explain the lower rate of movement of this landform a morphometric analysis and research using ert were performed the geophysical measurements showed that the ridge comprised rock formations of greater resistivity than its surroundings it is most likely that the only preserved sandstone packet constituting the original secondary escarpment became separated from the bedrock due to rotational movement the presented studies indicate that the landslide was created due to geological and atmospheric conditions a clear revival of landslide movements took place after significant precipitation events that last occurred in the years 2010 and 2015 the bedrock substrate due to its lithology and tectonics facilitates these movements it was found that the landslide studied is a complex entity characteristic of the polish outer carpathians that has undergone multiple stages of development the landslide is active or periodically active and therefore must be excluded from the planned development as well as from other forms of human activity

high magnitude landslide events on a limestone scarp in central germany morphometric characteristics and climatic controls abstract there are both internal and external controlling factors leading to slope instability and susceptibility to mass movement processes this paper explores which external climatic variables of different temporal scales influence the occurrence of high magnitude landslide events the investigations were focused on the wellenkalk cuesta scarp in the thuringia basin thuringer becken in central germany the cuesta scarp is composed of a densely jointed limestone caprock wellenkalk and impermeable mudstones and marls of the upper bunter sandstone rot in the lower part of the slope mass movements are a typical feature of the wellenkalk scarp the entire scarp slope length 1000 km has been systematically mapped and investigated in a comprehensive research project in order to provide reliable information on the spatial distribution and control of the mass movements more than 20 of the scarp slope has been influenced by various types of holocene mass movements with strong differences in spatial frequencies sixteen high magnitude landslides sturzfliesungen were identified by field inspection and mapping of slope geomorphology information on locations morphometric characteristics stratigraphic positions and rainfall related attributes of the scarp slopes affected by the large landslides is presented mean annual rainfall amounts decrease from more than 800 mm in the western part of the basin to less than 550 mm in the east meteorological statistics on the spatial distribution of heavy rainfall intensities of different durations and return periods show that greatest precipitation intensities in short events 1 h are reached at the western margin differences in rainfall intensities between the western and eastern parts decrease with increasing duration of the events where available event related meteorological information was collected the spatial distribution of the landslides is most closely mirrored in the pattern of mean annual precipitation though this variable is generally not thought to be a satisfactory or reliable climatic controlling factor no landslides occur below a threshold value of 700 mm the empirical data show that some general level of average perennial water input into the slope system seems to be of decisive importance for the occurrence of high magnitude mass movements only when the precondition of a more general hydrological disposition is fulfilled a direct triggering of high magnitude mass movements by a short time intensive rainfall period or event can become effective

application of radar data to modeling rainfall induced landslides many shallow landslides are triggered by heavy rainfall previous studies of landslide modeling have been hampered by the scarcity of rain gauges to adequately depict the spatial variability of rainfall conditions triggering landslides this study simulates the efficiency of the critical rainfall model for landslide prediction in a mountainous watershed with inputs of different rainfall estimates associated with a typhoon tropical cyclone event doppler radar data at a spatial resolution of 1 km and measurements from six gauging stations provide the sources for rainfall estimates inverse distance weighted splines and kriging are the interpolation methods for gauged rainfall estimates a comparison of the simulation outputs shows that the model using radar rainfall estimates has a better performance than those using gauged rainfall estimates in predicting both landslides and stable areas in light of the results this paper also discusses the validity of the critical rainfall model for landslides in relation to its rainfall input and steady state hydrological assumption

tree ring based assessment of rockfall frequency on talus slopes at sola d andorra eastern pyrenees abstract the determination of the frequency of rockfall events continues to challenge quantitative hazard assessments in most mountain areas dendrogeomorphological analysis was used to assess rockfall frequency on talus slopes at sola d andorra eastern pyrenees andorra rockfall events were dated at two sites one at the outlet of a chute and the other below a rock wall the impact wounds visible on the tree surface were analyzed with a seasonal temporal resolution at each site trees were sampled in three forest strips 15 to 30 m wide located at different heights on the talus all the trees with visible injuries in the strips were sampled rockfall frequency cannot be assessed by a simple analysis of time series of tree damage a satisfactory assessment requires a prior interpretation of the location of the damaged trees in relation to a number of rockfall events at sola d andorra the rockfall chronology was reconstructed for the last 25 years by dating visible wounds for older periods the tree wound record of rockfalls is incomplete owing to progressive closure of wounds wounds exceeding 40 years in age had already disappeared from the tree surface in the study area our results show a clear reduction of the rockfall frequency down the talus a noticeable lateral change in frequency and an influence of source morphology chute or wall on rockfall activity on the talus

can low magnitude earthquakes act as a triggering factor for landslide activity examples from the western carpathian mts poland abstract there are numerous examples of the impact of strong earthquakes on landslide activity there is however very little information about the ability of low magnitude earthquakes m

estimates of strain due to brittle faulting sampling of fault populations abstract the geometry of sampling domains is a first order consideration in the characterization of brittle fault populations in most cases descriptions of fault size distributions based on map cross section traverse or borehole data systematically underestimate the number of small faults present in a volume the geometry of sampling domains may be accounted for using an empirical proportionality between fault displacement and trace length estimates of strain in which the sampling geometry is considered suggest that small faults accommodate a significant portion of the total strain due to the brittle faulting process

a review of dendrogeomorphological research applied to flood risk analysis in spain over the last forty years applying dendrogeomorphology to palaeoflood analysis has improved estimates of the frequency and magnitude of past floods worldwide this paper reviews the main results obtained by applying dendrogeomorphology to flood research in several case studies in central spain these dendrogeomorphological studies focused on the following topics 1 anatomical analysis to understand the physiological response of trees to flood damage and improve sampling efficiency 2 compiling robust flood chronologies in ungauged mountain streams 3 determining flow depth and estimating flood discharge using two dimensional hydraulic modelling and comparing them with other palaeostage indicators 4 calibrating hydraulic model parameters i e manning roughness and 5 implementing stochastic based cost benefit analysis to select optimal mitigation measures the progress made in these areas is presented with suggestions for further research to improve the applicability of dendrogeochronology to palaeoflood studies further developments will include new methods for better identification of the causes of specific types of flood damage to trees e g tilted trees or stable isotope analysis of tree rings to identify the climatic conditions associated with periods of increasing flood magnitude or frequency

prehistoric rock avalanches in the olympic mountains washington rock avalanches blocked streams in the olympic mountains southwest of puget sound during the past few thousand years limiting radiocarbon ages indicated that three or four of six avalanches occurred from 1000 to 1300 years ago or shortly thereafter most of the dates were from the outer preserved rings of trees drowned behind avalanche dams these three or four avalanches may be coeval not only with one another but also with abrupt tectonic deformation in western washington no rock avalanches in the olympic mountains are known to have resulted from storms or earthquakes during the past century the avalanches strengthen the case that a large prehistoric earthquake occurred in the puget sound region

a review of assessing landslide frequency for hazard zoning purposes abstract the probability of occurrence is one of the key components of the risk equation to assess this probability in landslide risk analysis two different approaches have been traditionally used in the first one the occurrence of landslides is obtained by computing the probability of failure of a slope or the reactivation of existing landslides in the second one which is the objective of this paper the probability is obtained by means of the statistical analysis of past landslide events specifically by the assessment of the past landslide frequency in its turn the temporal frequency of landslides may be determined based on the occurrence of landslides or from the recurrence of the landslide triggering events over a regional extent hazard assessment using frequency of landslides which may be taken either individually or collectively requires complete records of landslide events which is difficult in some areas its main advantage is that it may be easily implemented for zoning frequency assessed from the recurrence of landslide triggers does not require landslide series but it is necessary to establish reliable relations between the trigger its magnitude and the occurrence of the landslides the frequency of the landslide triggers can be directly used for landslide zoning however because it does not provide information on the spatial distribution of the potential landslides it has to be combined with landslide susceptibility spatial probability analysis to perform landslide hazard zoning both the scale of work and availability of data affect the results of the landslide frequency and restrict the spatial resolution of frequency zoning as well magnitude frequency relationships are fundamental elements for the quantitative assessment of both hazard and risk

mass movements and tree rings a guide to dendrogeomorphic field sampling and dating abstract trees affected by mass movements record the evidence of geomorphic disturbance in the growth ring series and thereby provide a precise geochronological tool for the reconstruction of past activity of mass movement the identification of past activity of processes was typically based on the presence of growth anomalies in affected trees and focused on the presence of scars tilted or buried trunks as well as on apex decapitation for the analyses and interpretation of disturbances in tree ring records in contrast clear guidelines have not been established with largely differing or no thresholds used to distinguish signal from noise at the same time processes with a large spatial footprint e g snow avalanches landslides or floods will likely leave growth anomalies in a large number of trees whereas a falling rock would only cause scars in one or a few trees along its trajectory based on the above considerations we examine issues relating to the interpretation and dendrogeomorphic dating of mass movements particular attention is drawn to sampling in terms of sample distribution across a study site the actual selection of trees as well as to sample size i e number of trees sampled based on case studies from snow avalanche debris flow and landslide sites we demonstrate that thresholds can indeed improve dating quality and at the same time minimize noise in time series we also conclude that different thresholds need to be used for different processes and different periods of the reconstruction especially for the early stages of the reconstruction when the number of potentially responding trees will be much smaller this paper seeks to set standards for dendrogeomorphic fieldwork analysis and interpretation for different processes of mass movements

application of eccentric growth of trees as a tool for landslide analyses the example of picea abies karst in the carpathian and sudeten mountains central europe abstract a method based on dendrochronology was developed to analyse the spatial and temporal variability of landslide activity as an alternative and complement to methods such as field monitoring of landslide relief aerial photography and remote sensing the method involves a feature of wood anatomy tree ring eccentricity which is used in the dating procedure the degree of eccentricity is used as an indicator of the intensity of the mechanical stress affecting a tree stem in a certain year the objective was to develop a mathematical indicator of tree ring eccentricity for dating the recent dynamics of landslides a method presented in the paper is also designed for practical application in detecting initial landslide activity and allowing the determination of triggering factors the index developed is dimensionless and for this reason is independent of the absolute ring variations of the single trees analysed using reference results from stable slopes as thresholds in dating an objective method for detecting landslide activity was developed the method was used in the carpathian and sudeten mountains on three landslides with different sizes and geological settings it was found that the values of eccentricity index in trees growing on stable slopes rarely exceed at 100 while in trees growing on landslides they can reach hundreds to thousands per cent a spatial analysis of the eccentricity values conducted for a single landslide has revealed that the method developed allows one to identify areas of landslide activation and to observe the down or upslope propagation of instability a comparison of the results obtained regarding the precipitation record has shown that by using the method that has been developed it is possible to detect past mass movement episodes caused by heavy long term rainfall as well as by single short lasting but torrential downpours

holocene history of earthflow mass movements in south central british columbia the influence of hydroclimatic changes large earthflows in south central british columbia have exhibited regionally consistent fluctuations in their movement during the holocene over the past 60 years air photographs show that many earthflows were reactivated during the relatively wet period 1950 1985 over the past 300 years a fairly coherent relationship is established between periods of wetter climate defined by the tree ring record and phases of slope movement defined by the record of compression wood development in conifers located near earthflow headscarps on a time scale of several thousand years stratigraphic evidence shows that many large earthflows in the region underwent significant reactivation of movement in the post mazama period during the relatively wet cool neoglacial interval of the holocene these lines of evidence indicate that holocene hydroclimatic changes have exerted an important influence on the regimen of large earthflows earthflows present a wealth of paleogeomorphic information hitherto largely neglected

laboratory investigation of the interaction of off axis mantle plumes and spreading centres mantle plumes and mid ocean ridge spreading centres are the dominant phenomena through which mass and heat are transported from the mantle to the earth s surface it now seems that the dispersion of near ridge plumes beneath the lithosphere is modulated strongly by mid ocean ridges in particular geochemical and geophysical observations have suggested that rising plumes are diverted towards and feed nearby ridges 1 7 here we confirm the feasibility of this model with laboratory experiments that incorporate the essential physical and fluid dynamic aspects of a plume ridge upper mantle system our results indicate that an off axis plume may communicate thermally and chemically with a spreading ridge through a narrow sub horizontal conduit instead of a broader radially spreading plume head a necessary condition for this communication is the presence of a lithospheric or rheological boundary layer that thickens away from the ridge axis owing to conductive cooling interestingly we find that for high plume temperatures increasing the plume thermal buoyancy may inhibit rather than enhance plume ridge interaction as a result of increased erosion of the overlying lithosphere

flow of canary mantle plume material through a subcontinental lithospheric corridor beneath africa to the mediterranean comment the atlas mountain article 1 range in morocco northwest africa represent an intracontinental belt with an elevation up to 4400 m marked by the unexpected lack of a thick lithospheric root this has been explained by the major role of thermal uplift in the anti high and middle atlas

capture of the canary mantle plume material by the gibraltar arc mantle wedge during slab rollback summary recent evidence suggests that a portion of the canary plume travelled northeastwards below the lithosphere of the atlas mountains in north africa towards the alboran domain and was captured 10ma ago by the gibraltar subduction system in the western mediterranean the capture would have been associated with the mantle return flow induced by the westwardretreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the gibraltar subduction zone such material eventually contaminated the subduction related volcanism in the alboran region in this work we use scaled analogue models of slab plume interaction to investigate the plausibility of the plume capture an upper mantle scaled model combines a narrow 400 km edge fixed subduction plate with a laterally offset compositional plume the subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 1350 km 2 while the plume head initially spreads axisymmetrically it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km before getting dragged towards mantle wedge when applied to the canary plume gibraltar subductionsystem ourmodelsupportstheobservationallybasedconceptualmodelthatmantle plume material may have been dragged towards the mantle wedge by slab rollback induced toroidal mantle flow using a scaling argument for the spreading of a gravity current within a channel we also show that more than 1500 km of plume propagation in the sublithospheric atlas corridor is dynamically plausible

thrust sequences in the eastern spanish pyrenees detailed mapping of the south pyrenean zone in the eastern spanish pyrenees shows that a great number of alpine thrusts affect the basement and the cover the geometry of the thrust structures and their propagation sequence can be interpreted from balanced sections the folding dies out downwards from the higher thrust sheets to the lower ones and demonstrates a piggy back thrusting sequence these thrusts form a duplex the sole thrust of this duplex is the vallfogona thrust the roof thrust is rooted somewhere within the axial zone the thrusts climb southwards from the axial zone basement up into tertiary cover sediments these thrusts have been folded so that they now dip to the south and form the southern side of the axial zone antiformal stack locally smaller antiformal stacks developed and produced strong folds in the higher thrust sheets the south pyrenean zone studied is equivalent to the gavarnie nappe and the connection between them below the detached south pyrenean central unit may be the nogueres zone

the sensitivity of dendrogeomorphic approaches to assessing landslide movements abstract an understanding of past landslide behaviour is crucial for the estimation of future landslide activity in this respect methods of absolute dating are frequently used for landslide history assessment dendrogeomorphic tree ring based approaches are standard methods for the spatio temporal reconstruction of landslide activity with annual to even sub annual resolution and timespans of several centuries depending on the tree age nevertheless the verification of the effectiveness sensitivity and precision of these dendrogeomorphic approaches has not been addressed in more detail despite their wide spectrum of limitations this study makes an assessment of tree ring based chronologies of landslides based on a comparison with the independent data of past landslide activity from instrumental monitoring the chronology of past landslide events was created from 528 tree ring series from 132 individuals of norway spruce picea abies l karst growing on a monitored landslide in the outer western carpathians the ond ejnik mt and was expressed as the yearly variation in the standard event response index the landslide was monitored at two sites via technical levelling since 2007 and an automated wire extensometer since 2014 the obtained results show a high sensitivity of reaction wood formation to movements on the order of several mm e g the abrupt acceleration of movements in february 2017 as recorded by the extensometer moreover a one year delay in the growth response to movement occurring in the middle part of the growing season of the previous year was detected this fact fully supports the introduction of the dendrological year to dendrogeomorphic research the partial lack of correspondence between tree ring records and data from more distant monitoring sites suggests the need for separate dendrogeomorphic analyses of the individual homogenous parts of landslide areas finally the use of four instead of two increment cores per tree did not provide any extra event years but increased the values of the event response index of the dated events

probability maps of landslide reactivation derived from tree ring records pra bellon landslide southern french alps probability maps of landslide reactivation are presented for the pra bellon landslide located in the southern french alps based on results obtained with dendrogeomorphic analysis spatiotemporal patterns of past landslide activity was derived from tree ring series of 403 disturbed mountain pine trees growing in the landslide body in total 704 growth disturbances were identified in the samples indicating 22 reactivation phases of the landslide body between 1910 and 2011 the mean return period was 4 5 years given the spatiotemporal completeness of the reconstruction probabilities of landslide reactivation were computed and illustrated using a poisson distribution model and for 5 20 50 and 100 years probability of landslide reactivation is highest in the central part of the landslide body and increases from 0 13 for a 5 year period to 0 94 for a 100 year period conversely probabilities of reactivation are lower at its margins the proposed method differs from conventional approaches based on statistical analyses or physical modeling that have demonstrated to have limitations in the prediction of spatiotemporal reactivation of landslides our approach is in contrast based on extensive data on past landslides and therefore allowed determination of quantitative probability maps of reactivation derived directly from the frequency of past events this approach is considered a valuable tool for land managers in charge of protecting and forecasting people and their assets from the negative effects of landslides as well as for those responsible for land use planning and management it demonstrates the reliability of dendrogeomorphic mapping that should be used systematically in forested shallow landslides

new insight into the factors leading to the 1998 flank collapse and lahar disaster at casita volcano nicaragua during unusually high rainfall associated with hurricane mitch in 1998 a flank collapse leading to a disastrous lahar occurred at casita volcano nicaragua the lack of a similar failure during a rainfall event of comparable magnitude in 1982 tropical storm alleta suggests that additional factors influenced the 1998 collapse we have investigated the potential contribution of erosional flank undercutting seismic activity and anthropogenic land cover change at the collapse site except for seismic events prior to mitch which may have increased flank instability none of these factors appears significant instead for failure to occur the following conditions were required 1 highly fractured slope material allowing deep and rapid infiltration of meteoric water 2 a less permeable underlying layer to obstruct drainage 3 strong continuous antecedent rainfall to build up high pore water pressure and 4 episodic high intensity precipitation during mitch to generate recurrent pressure waves prerequisite 1 was provided by edifice wide deformation towards the south east seismic activity and proximity to a prominent fault and local subsidence condition 2 was met by clay rich layers resulting from hydrothermal alteration more than 1 900 mm of rain fell in the 6 months prior to mitch without significant interruption while intense episodic precipitation occurred during the hurricane satisfying conditions 3 and 4 respectively the main difference with alleta was that it occurred at the beginning of the rainy season and therefore without sufficient antecedent rainfall anthropogenic activity including land cover change did not affect slope stability i e the hazard however vulnerability was generated when two towns were established in the lowlands south of casita on top of previous lahar deposits it was greatly increased when approximately 4 km of forest between the collapse site and the towns were cleared paving the way for a largely unobstructed debris flow deforestation also facilitated erosion along the flanks to provide about 78 of the material contained in the lahar when it destroyed the towns killing more than 2 500 people

the origin of shallow landslides in moravia czech republic in the spring of 2006 abstract at the end of march 2006 the czech republic cz witnessed a fast thawing of an unusually thick snow cover in conjunction with massive rainfall most watercourses suffered floods and more than 90 shallow landslides occurred in the moravian region of eastern cz primarily in non forested areas this region geologically part of the outer western carpathians is prone to landslides because the bedrock is highly erodible mesozoic and tertiary flysch the available meteorological data depth of snow water equivalent of the snow cumulative rainfall air and soil temperatures from five local weather stations were used to construct indices quantitatively describing the snow thaw among these the total cumulative precipitation tcp combines the amount of water from both thawing snow and rainfall this concurrence of rain and runoff from snow melt was the decisive factor in triggering the landslides in the spring the tcp index was applied to data of snow thaw periods for the last 20 years when no landslides were recorded this was to establish the safe threshold of tcp without landslides the calculated safe threshold value for the region is ca 100 mm of water delivered to the soil during the spring thaw corresponding to ca 11 mm day 1 in 2006 10 of the landslides occurred under or at 100 mm of tcp the upper value of 155 mm covered all of the landslides

dynamics of lithospheric thinning and mantle melting by edge driven convection application to moroccan atlas mountains edge driven convection edc forms in the upper mantle at locations of lithosphere thickness gradients e g craton edges in this study we show how the traditional style of edc a convection cell governed by the cold downwelling below an edge alternates with another style of edc in which the convection cell forms as a secondary feature with a hot asthenospheric shear flow from underneath the thicker lithosphere these alternating edc styles produce episodic lithosphere erosion and decompression melting three dimensional models of edc show that convection rolls form perpendicular to the thickness gradient at the lithosphere asthenosphere boundary stagnant lid convection scaling laws are used to gain further insight in the underlying physical processes application of our models to the moroccan atlas mountains region shows that the combination of these two styles of edc can reproduce many of the observations from the atlas mountains including two distinct periods of cenozoic volcanism a semicontinuous corridor of thinned lithosphere under the atlas mountains and piecewise delamination of the lithosphere a very good match between observations and numerical models is found for the lithosphere thicknesses across the study area amounts of melts produced and the length of the quiet gap in between volcanic episodes show quantitative match to observations

deep structure of the japan subduction zone abstract we determined 3 d p wave velocity structure down to 700 km depth under the japan islands using a large number of arrival time data from local and teleseismic events simultaneously we collected 207 000 arrival times from 7743 shallow and deep earthquakes occurred in and around japan and 34 148 data from 333 teleseismic events which were recorded by over 1000 seismic stations on the japan islands our tomographic model revealed some new features the philippine sea slab is found to subduct down to 500 km depth under southwest japan though the seismicity within the slab ends at 150 200 km depth significant low velocity anomalies are found to exist in the deep portion of the mantle wedge above the pacific slab which may be caused by the deep dehydration process of the slab slow anomalies are detected in the mantle beneath the pacific slab which may be caused by a mantle plume or upwelling of hot mantle materials associated with the deep subduction of the pacific slab and its collapsing down to the lower mantle

differences between the responses of european larch larix decidua mill and norway spruce picea abies l karst to landslide activity based on dendrogeomorphic and dendrometric data abstract investigations of mass movement hazards need to be supported by accurate data regarding past frequencies of landslide reactivations dating landslide events using tree rings is a reliable approach for vegetated slopes in temperate climates despite the enhanced use of dendrogeomorphic research during recent decades little is known about the specific responses of larix spp to landslide movements we investigated the active section 0 6 ha of a complex landslide in the vsetinske vrchy mts outer western carpathians that is overgrown by a forest stand composed of european larch larix decidua mill and norway spruce picea abies l karst using the dendrometric and dendrogeomorphic data identified from 74 trees 33 l decidua and 41 p abies including the number and types of growth disturbances gds and compiled event chronologies we compared the responses of both tree species to the same landslide reactivations we observed the same mean tree stem inclination for both tree species whereas the inclination azimuths differed l decidua generally showed a higher number of stem bends compared to p abies similar proportions of subjectively identified gds compression wood cw and abrupt growth suppression gs and mathematically identified gds tree ring eccentricities were observed in both tree species however the total number of gd tree 1 was slightly higher in l decidua 4 1 than in p abies 3 2 a higher abundance of gs was identified in l decidua at the expense of cw compared to p abies the event chronology based on the mathematical approach revealed slightly more landslide signals than for the subjective approach mainly in l decidua however the largest known landslide reactivation in 1997 was recorded in all cases in both tree species based on the cw analysis it was shown that larger stem inclinations are associated with longer persistence of cw in p abies rather than l decidua resulting in the possible masking of younger landslide events by contrast p abies compensates for that limitation by having a generally shorter mean duration of cw than l decidua overall it seems that the complexity of landslide movements and root system architecture influenced the number and character of gds in both tree species in addition we did not find any relationships between the measured dendrometric parameters and number of gds to better assess the most suitable trees for dendrogeomorphic dating prior to sampling therefore we recommend sampling both tree species when they overgrow the same landslide body so that the final event chronology will be more robust and possible limitations of one tree species can be eliminated by the benefits of the second

frequency of debris flows and their relation with precipitation a case study in the central alps italy abstract debris flows are very important and widespread mass movements and represent a remarkable geomorphological hazard this research deals with debris flows in an alpine environment studied using dendrogeomorphological dating techniques outlining their relation with precipitation and analysing possible changes in their frequency and intensity over time the study area is the upper valle del gallo northern italy a typical high mountain environment dominated by mass wasting processes where many debris flow fans occupy the valley bottom dendrogeomorphological research was conducted on twelve of these fans and two channels located on slopes tree growth anomalies abrasion scars compression wood and abrupt growth changes were used as dating methods two hundred and thirty nine debris debris flow events between 1875 and 2003 were dated using 757 trees pinus montana mill analysis between dated events and precipitation suggests that debris flows in the study area could be triggered by 20 30 mm of rain concentrated in a few hours the debris flow frequency tends to increase gradually but the highest value seems to have occurred in the period 1974 1983 this trend agrees with the historical occurrence of flooding events in northern italy as inferred by literature and with similar studies conducted in the swiss alps the results of this research are intended as a contribution for understanding the response of geomorphological processes to climatic changes

evidence for active subduction beneath gibraltar we report on a marine seismic survey that images an active accretionary wedge west of gibraltar ramp thrusts offset the seafloor and sole out to an east dipping decollement indicating ongoing westward vergent tectonic shortening new traveltime tomographic re sults image a slab of oceanic lithosphere descending from the atlantic domain of the gulf of cadiz passing through intermediate depth 60 120 km seismicity beneath the west ernmost alboran sea and merging with a region of deep focus earthquakes 600 660 km below granada spain together these new data provide compelling evidence for an active east dipping subduction zone

analysis of baishuihe landslide influenced by the effects of reservoir water and rainfall since the impoundment of the three gorges reservoir in june 2003 a number of new landslides have occurred and existing landslides have been made worse the 1 260 104 m3 baishuihe landslide located at 56 km west of the three gorges dam began to deform more noticeably after the first impoundment in early july 2003 the sliding of the two blocks comprising the landslide one an active block and the other a relatively stable block became apparent after approximately 5 years of monitoring field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir these effects have been investigated in the present paper including the deformation characteristics movement pattern direction displacement and velocity earmarking the temporal evolution of the active block based on a practical creep model of a large rock slide alert velocity thresholds for pre alert alert and emergency phases have been computed corresponding to the imminence of failure the alert velocity thresholds are being proposed to be included as a part of an early warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure the emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the three gorges reservoir in the near future

fault strain and seismic coupling on mid ocean ridges the contribution of extensional faulting to seafloor spreading along the east pacific rise epr axis near 3 s and between 13 n and 15 n is calculated using data on the displacement and length distributions of faults obtained from side scan sonar and bathymetric data it is found that faulting may account for of the order of 5 10 of the total spreading rate which is comparable to a previous estimate from the epr near 19 s given the paucity of normal faulting earthquakes on the epr axis a maximum estimate of the seismic moment release shows that seismicity can account for only 1 of the strain due to faulting this result leads us to conclude that most of the slip on active faults must be occurring by stable sliding laboratory observations of the stability of frictional sliding show that increasing normal stress promotes unstable sliding while increasing temperature promotes stable sliding by applying a simple frictional model to mid ocean ridge faults it is shown that at fast spreading ridges 90 mm yr the seismic portion of a fault ws is a small proportion of the total downdip width of the fault w the ratio ws w interpreted as the seismic coupling coefficient x and in this case x 0 in contrast at slow spreading rates 40 mm yr ws w and therefore x 1 which is consistent with the occurrence of large magnitude earthquakes mb 5 0 to 6 0 occurring for example along the mid atlantic ridge axis

spatio temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch a dendrogeomorphic approach using broad leaved trees abstract the undercut slope of the skalicka stra nice vrchy hill situated in the piedmont of the carpathian mountains czech republic is a regional landslide hotspot notorious for its repeated recent and historical sliding reactivations we performed tree ring analysis of a large number n 274 of broad leaved trees to reconstruct the spatio temporal patterns of landslide reactivation for a period spanning more than one hundred years 1884 2011 although tree rings of broad leaved trees are less reliable archives of landslide activity than those of conifers the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock although some known landslide years could not be found or were expressed by only weak signals in the reconstructed dataset the majority of landslide events reconstructed from the tree ring series coincide with hydrometeorological data revealing a correlation with heavy summer rainfalls lasting from two to ten days the spatial distribution of landslide recurrence derived from the tree ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock

high resolution fingerprints of past landsliding and spatially explicit probabilistic assessment of future reactivations aiguettes landslide southeastern french alps the purpose of this study was to reconstruct spatio temporal patterns of past landslide reactivation and the possible occurrence of future events in a forested area of the barcelonnette basin southeastern french alps analysis of past events on the aiguettes landslide was based on growth ring series from 223 heavily affected mountain pine pinus uncinata mill ex mirb trees growing on the landslide body a total of 355 growth disturbances were identified in the samples indicating 14 reactivation phases of the landslide body since ad 1898 accuracy of the spatio temporal reconstruction is confirmed by historical records and aerial photographs logistic regressions using monthly rainfall data from the histalp database indicated that landslide reactivations occurred due to above average precipitation anomalies in winter they point to the important role of snow in the triggering of reactivations at the aiguettes landslide body in a subsequent step spatially explicit probabilities of landslide reactivation were computed based on the extensive dendrogeomorphic dataset using a poisson distribution model for an event to occur in 5 20 50 and 100 yr high resolution maps indicate highest probabilities of reactivation in the lower part of the landslide body and increase from 0 28 for a 5 yr period to 0 99 for a 100 yr period in the upper part of the landslide body probabilities do not exceed 0 57 for a 100 yr period and somehow confirm the more stable character of this segment of the aiguettes landslide the approach presented in this paper is considered a valuable tool for land use planners and emergency cells in charge of forecasting future events and in protecting people and their assets from the negative effects of landslides