satellite sar interferometry for the improved assessment of the state of activity of landslides a case study from the cordilleras of peru abstract in peru landslides have been causing damages and casualties annually due to the high mountain relief and distinct seasonal precipitation distribution satellite synthetic aperture radar sar interferometry represents one possibility for mapping surface deformation at fine spatial resolution over large areas in order to characterize aspects of terrain motion and potentially hazardous processes we present land surface motion maps derived from satellite sar interferometry insar for a part of the santa river basin between the cordilleras blanca and negra around the city of carhuaz in peru using both persistent scatterer interferometry psi and differential sar interferograms dinsar from alos 1 palsar 1 envisat asar alos 2 palsar 2 and sentinel 1 we mapped 42 landslides extending over 17 190 141 m2 within three classes of activity i e 0 2 cm a 2 10 cm a and 10 cm a a geomorphological inventory of landslides was prepared from optical satellite imagery and field experience and compared to the insar based slope instability inventory the two approaches provide slightly different information about landslide spatial and temporal activity patterns but altogether they can be combined for the assessment of the state of activity of landslides and possibly the development of hazard maps which are not systematically available in this region we conclude that alos palsar 1 and 2 and sentinel 1 data have a high potential to derive high quality surface deformation information of landslides in many mountainous regions worldwide due to their global and frequent acquisition strategies

case history of landslide movement during the northridge earthquake we document a case history of northridge earthquake induced movement of a coherent landslide mass comprised principally of weathered previously sheared siltstone information on the residual shear strength of the material through which the sliding occurred is available both from backanalysis of a static rainfall induced failure on the same slope and laboratory test data postearthquake field reconnaissance data establishes the seismic slope displacements near the slope crest a yield coefficient is estimated for the slope based on residual shear strengths and measured groundwater levels at the time of the northridge earthquake this yield coefficient is used with four horizontal equivalent acceleration time histories that approximate the seismic demand within the slide mass in newmark sliding block displacement analyses the calculated displacements range from approximately 20 to 90 mm which compares well with observed displacements at the slide scarp of approximately 50 mm

triggering and runaway processes of catastrophic tsaoling landslide induced by the 1999 taiwan chi chi earthquake as revealed by high velocity friction experiments pliocene sedimentary rocks of about 130 mm3 in volume slid along bedding planes dipping by 14 with an average speed of about 35 m s during the tsaoling landslide we conducted friction experiments to reproduce the initiation processes of this landslide by idealizing landslide movements during the earthquake as accelerating decelerating motion experiments were done on shale from the field at 3 mpa normal stress corresponding to the overburden pressure results indicate that the accelerating decelerating motion causes weakening and strengthening at each oscillation cycle and results in overall slip weakening which can be approximated as an exponential slip weakening behaviors during oscillatory slip are fairly similar to those during sliding at constant slip rates newmark analysis with measured frictional properties reveals that the landslide can be triggered with wet gouge properties but the landslide motion stops with parameters for dry shale gouge delayed initiation of the landslide is consistent with a survivor s witness

self excitation process due to local seismic amplification responsible for the reactivation of the salcito landslide italy on 31 october 2002 1 an integrated numerical and geophysical approach was used to investigate the role of local seismic amplification in the reactivation of the salcito landslide italy after the molise earthquake of 31 october 2002 numerical stress strain analysis with flac 5 0 fdm software performed in dynamic configuration showed that the 1 hz frequency was consistent with landslide instability conditions the fourier spectrum of the triggering earthquake showed two main peaks occurring at 1 and 2 hz respectively which could be related to local effects the analysis of h v spectral ratios of ambient noise records obtained in the landslide area evidenced amplification effects in the 1 3 hz range on the basis of an engineering geology model numerical modeling of both 1 d and 2 d seismic wave propagation was conducted using linear and nonlinear solutions the simulation outputs showed 1 a 1 hz amplification ascribable to 2 d effects due to a landslide mass lying within a basin like geological structure 2 a double peak amplification at about 2 and 3 hz respectively ascribable to 1 d resonance of the landslide mass and 3 1 d plus lateral wave effects within the landslide mass in the 2 5 3 5 hz frequency range these findings suggest that local amplification of ground motion by the salcito landslide mass may generate a self excitation process responsible for its reactivation

the formation of longitudinal fronts in a coastal plain estuary longitudinal estuarine fronts aligned parallel to the axis of the estuary are characteristic of the york river their time scale for genesis and decay is of the order of hours they are usually located at the inner edge of the shoals or over the main channel field measurements have shown marked intratidal differences in density and current speeds across this estuary these can be correlated with changes in depth and the strength of the advective processes differential advection between the channel and shoal regions when acting upon a constant longitudinal density gradient is shown to be of sufficient magnitude to generate strong lateral density gradients and thus fronts at particular times within the tidal cycle

anti plane responses of acceleration by a shallow hill next to an alluvial valley abstract this study proposed a hybrid method combining finite element method fem and a wave function based on the lamb series in conjunction with modified transfinite interpolation for use in examining surface accelerations on a semi elliptical hill subjected to shear horizontal sh waves of various dimensionless frequencies at various incident angles the case topography included a semi elliptical hill of fixed height adjacent to a semi elliptical alluvial valley of variable depth ehav differences in site effects between ehav and a single semi elliptical hill or a semi elliptical alluvial valley were investigated as a function of the modified transmissibility tr variations in tr associated with clearly revealed the resonance frequencies rfs associated with an elevated probability of landslides our simulation results revealed a larger number of rfs form in hills adjacent to av than in isolated hill this study proposes a systematic approach for the analysis of site effects of ehav focusing on the identification of potential landslides due to seismic waves excitation

velocity field of the la clapiere landslide measured by the correlation of aerial and quickbird satellite images 1 two displacement maps of the la clapiere landslide france have been derived over two periods of 4 years 1995 1999 and 1999 2003 by correlation of aerial photographs and a quickbird satellite image the movement of the landslide ranges from 2 5 m to 20 m per year those values have been validated over 13 points monitored by conventional tacheometric measurements three areas with significant differences in velocity field have been mapped limits of those areas are in good agreement with in situ observations velocity maps show the low long term temporal variability of the landslide movement and its spatial variability the optical correlation method using images derived from various sensors airborne and spatial is a promising technique for improving the spatial resolution of velocity field observation of landslides over several years

earthquake driven acceleration of slow moving landslides in the colca valley peru detected from pleiades images abstract major earthquakes in mountainous areas often trigger rapid landslides some observations also suggest that earthquakes can damage landslide prone areas or cause slow moving landslides to accelerate with a risk of evolution to rapid landslides in the following months after the earthquake here we use optical images from the pleiades satellites to detect slow moving landslides and quantify the effect of earthquakes on the landslide motion we process multi temporal pleiades images acquired in march april and july 2013 over an area of 210 km2 in the colca valley south peru to obtain two digital elevation models dem and three displacement fields of the area the processed dems have an uncertainty of 0 6 m 1 an order of magnitude better than two global and freely available dems gdem v2 and srtm whereas the displacement fields have an uncertainty of between 0 11 and 0 18 m 1 in both horizontal directions using these data we detect 9 slow moving landslides and compare their velocities during the march april and april july periods we find that landslide velocities are highest during the wet season which suggests a strong groundwater control and we also highlight a landslide acceleration caused by a regional mw 6 0 earthquake the major parameters controlling the acceleration of the slow moving landslides are the rock type and the distance to the source suggesting that friction at the basal interface in the weeks after the earthquake is dependent on the shaking intensity

a 45 year time series of dune mobility indicating constant windiness over the central sahara although evidence is mounting that links global warming to changes in atmospheric dynamics over the atlantic realm similar studies over the african continent are lacking and even if such models would exist it would be difficult to verify their validity due to the paucity of meteorological observations and anemometers in the central sahara a pragmatic way around this problem is to monitor barchan dune velocity as a proxy for the windiness of desert areas dune migration rates are a measure of the amount of work done by the wind which does not require field measurements but can be observed from space instead this paper presents a novel application of the remote sensing tool cosi corr for the construction of time series of dune mobility from sequences of optical satellite imagery the technique has been applied to the bodele depression in northern chad to demonstrate that dune migration rates in the central sahara have been remarkably constant for nearly half a century leading us to conclude that wind velocities have not changed more than 0 2 per year over that period it is therefore unlikely that the frequency and intensity of dust storms originating from this hot spot has significantly changed over the past decades either

the formation of a tidal intrusion front at the mouth of a macrotidal partially mixed estuary a field study of the dart estuary uk high resolution measurements of density and velocity were made before during and after the formation of a transient tidal intrusion front at the mouth of a narrow partially mixed estuary during spring tides detailed acoustic doppler current profiler adcp and density measurements throughout 1 km longitudinal transects at hourly intervals during spring tides indicated that the front formed when the barotropic inflow was sufficient to arrest the buoyant outflow from the estuary this has been shown to be driven by a constriction of the channel at the mouth and a depression in the seabed just landward of the mouth with these changes in topography shown to interact with the flow in a similar manner to theoretical two layer flow over the lee side of a sill a detailed analysis of the flow and stratification across the narrow frontal interface found a high degree of shear and mixing just prior to the plunge point which together with a hydraulic jump at the seabed depression eventually led to the destruction of the density interface and the total intrusion of seawater as the flooding tide strengthened there was no surface manifestation of this front during neap tides and further measurements have confirmed that the relatively weak barotropic flow at this time was not sufficient to overcome the stratification in a two layer regime an evaluation of the key frontal discriminators has confirmed the validity of their use in such an estuary

controls of earthquake faulting style on near field landslide triggering the role of coseismic slip 1 we compare the spatial distributions of seven databases of landslides triggered by mw 5 6 7 9 earthquakes using distances normalized by the earthquake fault length we show that the normalized landslide distance distributions collapse i e the normalized distance distributions overlap whatever the size of the earthquake separately for the events associated with dip slip buried faulting earthquakes and surface faulting earthquakes the dip slip earthquakes triggered landslides at larger normalized distances than the oblique slip event of loma prieta we further identify that the surface faulting earthquakes of wenchuan chi chi and kashmir triggered landslides at normalized distances smaller than the ones expected from their mw 7 6 magnitudes these results support a control of the seismic slip through amplitude rake and surface versus buried slip on the distances at which landslides are triggered in terms of coseismic landslide management in mountainous areas our results allow us to propose distances at which 95 and 75 of landslides will be triggered as a function of the earthquake focal mechanism

landslide movement in southwest colorado triggered by atmospheric tides the slumgullion landslide in the western united states has been moving almost continuously for over 100 years observations and numerical modelling show that air pressure changes from atmospheric tides trigger daily movement

application of image cross correlation to the measurement of glacier velocity using satellite image data abstract image to image cross correlation software is applied to pairs of digital satellite images to map the velocity field of moving ice this technique uses small scale glacial surface features such as crevasse scars and snow dunes as markers on the surface of the moving ice displacements of the surface features are mapped by selecting small image areas centered on distinct features or by dividing a large area of densely featured glacial surface into a grid of areas and searching a subsequent image for matching areas using a cross correlation algorithm interpolation of the peak correlation values allows the displacements to be measured to subpixel accuracy resulting in very precise velocity measurements cross correlation is also applied to provide image coregistration in areas devoid of bedrock exposures in such areas subtle large scale topographic undulations in the ice surface related to underlying bedrock structure may be correlated by using large image areas and low pass filtered images both types of applications are demonstrated using ice stream d and ice stream e in west antarctica as test areas a high resolution map of the velocity field of the central portion of ice stream e generated by the displacement measuring technique is presented the use of cross correlation software is a significant improvement over previous manually based photogrammetric methods for velocity measurement and is far more cost effective than in situ methods in remote polar areas

closing the mass budget of a tidewater glacier the example of kronebreen svalbard in this study we combine remote sensing in situ and model derived datasets from 1966 to 2014 to calculate the mass balance components of kronebreen a fast flowing tidewater glacier in svalbard

analysis of large seismically induced gravitational deformations imaged by high resolution cosmo skymed synthetic aperture radar using differential synthetic aperture radar interferometry dinsar on cosmo skymed constellation of small satellites for the mediterranean basin observation data we obtain an accurate and spatially continuous measure of the coseismic ground displacement due to the mw 6 3 l9aquila central italy earthquake we identify two local deformation patterns associated with long term gravitational mass movements and interpret the deformation mechanisms by integrating geological analysis and simple analytical modeling these subtle deformations the role of which in landscape evolution and earthquake induced hazard needs to be fully assessed may only be identified using high resolution dinsar

inversion of deformation fields time series from optical images and application to the long term kinematics of slow moving landslides in peru abstract slow moving landslides are numerous in mountainous areas and pose a large threat to populations many observations show that their kinematics is driven by climatic forcings and earthquakes in this study we document the complex interaction between those two forcings on the slow moving landslide kinematics based on the retrieval of landslide displacements over 28 years using optical satellite images to overcome the decorrelation effect over this large time span and possible misalignment between images we develop a method that uses the redundancy of displacement fields from image pairs to derive a robust time series of displacement the method is tested on the 28 year long spot1 5 pleiades archive over an area in peru affected by both earthquakes and rainfall errors are estimated on stable areas and by comparison with one 13 year long and eleven 3 year long gps time series on the maca landslide the methodology diminishes by up to 30 the uncertainty and reduces significantly the gaps due to decorrelation the data set allows detecting 3 major landslides moving at a rate of 35 to 50 m over 28 years and smaller landslides with lower displacement rates time series obtained over the three main landslides provide interesting results of their long term kinematics primarily driven by precipitation we propose simple statistical hydro kinematic models relating yearly motion to seasonal rainfall to explain the observed time series we found that annual precipitation is controlling the landslide displacements after a certain rainfall threshold is reached besides this control we show the possible impact of a local mw 5 4 earthquake in 1991 on the kinematics of the maca landslide our results suggest that the earthquake accelerated the landslide and has an effect during several years on the precipitation threshold required for triggering a motion these results suggest that the rainfall threshold can vary in time following strong earthquakes shaking

combined observations of rock mass movements using satellite sar interferometry differential gps airborne digital photogrammetry and airborne photography interpretation 1 recent global warming through the related retreat of mountain glaciers causes a growing number of different slope instabilities requiring accurate and cost effective monitoring we investigate the potential of combined remote sensing observations from satellite and airborne microwave and optical sensors for an efficient survey of mountainous ground displacements the evolution of a paraglacial deep seated rock mass movement due to glacier retreat in the swiss alps has been observed between 1976 and 2008 with satellite synthetic aperture radar sar interferometry differential gps and airborne digital photogrammetry analysis of differential sar interferograms revealed an acceleration of the landslide from 4 cm yr in the slope parallel direction during the mid 1990s to more than 30 cm yr in the summer of 2008 differential gps surveys performed between the summers of 2007 and 2008 indicate seasonal variations of the landslide activity the photogrammetric analysis revealed no significant movement i e 1 cm yr between 1976 and 1995 and provides an overview of the total displacement between 1995 and 2006 with high spatial resolution in situ and airborne photography interpretation suggests that the landslide was activated at earliest by the end of the last glaciation but without any significant long lasting activity during the holocene and that the exponentially increasing reactivation since the 1990s is the result of ongoing debutressing of the valley flank due to the glacier retreat in combination with strong precipitation and snowmelt events we conclude that the employed remote sensing techniques complement each other well within a landslide hazard assessment procedure

geochronologic and stratigraphic constraints on canyon incision and miocene uplift of the central andes in peru the deepest valleys of the andes have been cut in southern peru by the rios cotahuasi ocona and colca majes these canyons are late miocene landforms based on a new ignimbrite stratigraphy supported by 42 new 40ar 39ar age determinations obtained on plateau forming and valley filling ignimbrites between 19 and 13 ma a gently sloping surface bevelling the clastic wedge southeast of the developing mountain front was mantled by widespread ignimbrites after 13 ma this paleosurface was tilted up from 2 2 km a s l at the mountain front to 4 3 km a s l at the base of the pliocene and pleistocene volcanoes that crown the southwestern edge of the altiplano the canyons incised this topography after 9 ma while the dated base of younger ignimbrite valley fills suggests that these canyons had been cut down to near their present depths as early as 3 8 ma by 1 4 ma however the canyons had been almost completely refilled by 1 3 km thick unwelded pyroclastic deposits which were subsequently eroded valley incision since 9 ma at an average rate of 0 2 mm yr 1 is the response to topographic uplift after 13 ma combined with increasing runoff due to a wetter climate recorded after 7 ma although long term aridity generated an imbalance between high long term uplift rates and low plateau denudation rates the combination of aridity and volcanism still promoted canyon incision because episodic volcanic fills maintained a cycle of catastrophic debris avalanches and subsequent dam breakouts

seismically induced rock slope failures resulting from topographic amplification of strong ground motions the case of pacoima canyon california abstract the 1994 northridge earthquake mw 6 7 triggered extensive rock slope failures in pacoima canyon immediately north of los angeles california pacoima canyon is a narrow and steep canyon incised in gneissic and granitic rocks peak accelerations of nearly 1 6 g were recorded at a ridge that forms the left abutment of pacoima dam peak accelerations at the bottom of the canyon were less than 0 5 g suggesting the occurrence of topographic amplification topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 mw 6 7 san fernando earthquake furthermore high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones we conducted field investigations and slope stability back analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions which would have generated a significantly lower number of areas affected by landslides in contrast modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994 this observation confirms a significant role for topographic amplification on the triggering of landslides at the site and emphasises the need to select carefully the inputs for seismic slope stability analyses

surface motion of mountain glaciers derived from satellite optical imagery a complete and detailed map of the ice velocity field on mountain glaciers is obtained by cross correlating spot5 optical images this approach offers an alternative to sar interferometry because no present or planned radar satellite mission provides data with a temporal separation short enough to derive the displacements of glaciers the methodology presented in this study does not require ground control points gcps the key step is a precise relative orientation of the two images obtained by adjusting the stereo model of one slave image assuming that the other master image is well georeferenced it is performed with numerous precisely located homologous points extracted automatically the strong ablation occurring during summer time on the glaciers requires a correction to obtain unbiased displacements the accuracy of our measurement is assessed based on a comparison with nearly simultaneous differential gps surveys performed on two glaciers of the mont blanc area alps if the images have similar incidence angles and correlate well the accuracy is on the order of 0 5 m or 1 5 of the pixel size similar results are also obtained without gcps an acceleration event observed in early august for the mer de glace glacier is interpreted in term of an increase in basal sliding our methodology applied to spot5 images can potentially be used to derive the displacements of the earth s surface caused by landslides earthquakes and volcanoes

internal kinematics of the slumgullion landslide usa from high resolution uavsar insar data abstract landslides represent one of the most damaging natural hazards and often lead to unexpected casualties and property damage they also continually modify our natural environment and landscapes knowledge of landslide systems is largely restricted by the stochastic nature subjective interpretation and infrequent or spatially sparse surveying of landslides characterized by persistent daily movements of a couple of centimeters over multi centennial timescales and a long narrow shape as long as 4 km the slumgullion landslide in colorado usa represents an ideal natural laboratory to study slow moving landslides here we demonstrate the capability of the highly accurate spatially continuous airborne synthetic aperture radar sar system of the nasa uninhabited aerial vehicle sar uavsar to characterize the kinematic details of internal deformation of the slumgullion landslide using sar interferometry insar we develop a phase based approach to automatically extract the boundaries of the mobile geological structures without unwrapping comparison with historic field observations from 1991 reveals the 40 m advance of the frontal toe and shift of an internal fault the uavsar data also resolve an internal minislide 100 by 70 m which moves more southerly than the main body at 5 mm day in the lower part of the landslide a light detection and ranging lidar digital elevation model dem shows that the minislide is associated with the opening of a 30 by 10 m pull apart basin and bounding strike slip faults these extensional structures nearby incised streams and steepened local slopes helped establish the kinematic environment for the formation of the secondary minislide the disparity between the uavsar insar derived horizontal moving directions and the lidar dem derived slope aspects suggest that while the surface topography governs the first order orientation the local kinematics is also subject to the variable nature of heterogeneous landslide materials and the irregular basal bedrock surface the landslide velocity and precipitation show similar multi annual variations our study demonstrates that the freely available high resolution uavsar data have great potential for characterizing landslide kinematics and other small scale geological and geomorphological processes

first surface velocity maps for glaciers of monte tronador north patagonian andes derived from sequential pleiades satellite images we apply cross correlation to pleiades satellite images to generate accurate high resolution monthly surface velocity maps of monte tronador glaciers between march and june 2012 measured surface displacements cover periods as short as 19 days with a precision of 0 58 m 11 m a 1 these glaciers follow a radial flow pattern with maximum surface speeds of 390 m a 1 associated with steep icefalls the lower reaches of the debris covered tongues of verde and casa pangue glaciers are almost stagnant whereas ventisquero negro another debris covered glacier shows acceleration at the front due to calving into a proglacial lake low elevation debris covered glacier tongues show increasing velocities at the beginning of the accumulation season whereas higher elevation clean ice tongues reduce their speed during this period this contrasting behavior is probably in response to an increase in water input to the subglacial system from winter rainfall events at low elevations and a decrease in meltwater production at higher elevations these sequential velocity maps can help to identify the controls on glacier surface velocity aid in the delimitation of ice divides and could also contribute to more realistic calibration of ice flux mass balance models in this glacierized area

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

observations of a tidal intrusion front in a tidal channel abstract a visible front indicated by a surface colour change and sometimes associated with foam or debris lines was observed in a tidal channel during neap tide this is an example of a tidal intrusion front occurring in the absence of sudden topographical changes or reversing flows typically reported to be associated with such fronts detailed acoustic doppler current profiler and conductivity temperature depth measurements were taken on repeated transects both with fronts apparent and with fronts absent the results indicated that the front occurred as a result of stratification which was sustained by the buoyancy flux and the weak tide induced mixing during neap ebb tide the stronger tide induced mixing during spring tide restrained stratification leading to the absence of a front the mechanism of the frontogenesis was the density gradient between the stratified water formed during neap ebb tide and the more mixed seawater during neap flood tide thus the water on the landward southwestern side of the front was stratified and that on the seaward side northeastern of the front was vertically well mixed gradient richardson number estimates suggest that the flow between the stratified and mixed water was near the threshold 0 25 for shear instability meanwhile the density gradient would provide an initial baroclinic contribution to velocity convergence which is indicated by the accumulation of buoyant matter such as foam grass and debris into a sharply defined line along the surface the front migrates with the flood current with a local maximum towards the eastern side of the channel leading to an asymmetrical shape with the eastern side of the front driven further into the tiaozhoumen tidal channel

coseismic and postseismic motion of a landslide observations modeling and analogy with tectonic faults we document the first time series of a landslide reactivation by an earthquake using continuous gps measurements over the maca landslide peru our survey shows a coseismic response of the landslide of about 2 cm followed by a relaxation period of 5 weeks during which postseismic slip is 3 times greater than the coseismic displacement itself our results confirm the coseismic activation of landslides and provide the first observation of a postseismic displacement these observations are consistent with a mechanical model where slip on the landslide basal interface is governed by rate and state friction analogous to the mechanics of creeping tectonic faults opening new perspectives to study the mechanics of landslides and active faults

assessment of the size of large and great historical earthquakes in peru a critical reappraisal of great historical earthquakes in peru is made in order to obtain quantitative estimates of rupture length seismic moment tsunami magnitude mt and moment magnitude mw newly collected information concerning several historical earthquakes permits the evaluation of macroseismic zones and from the size of these zones the estimation of length of rupture seismic moment and magnitude mw it is found that local tsunami data provide good quantitative estimates of mt and therefore an independent way of verifying macroseismic estimates of rupture length and seismic moment a space time diagram of great historical earthquakes shows the existence of three zones roughly corresponding to the segmentation of the nazca plate hasegawa and sacks 1981 subducting under peru the northern zone looks aseismic the central one is very complex it breaks either completely or in smaller segments and it may go through long quiescence periods the recurrence time for the southern segment the more regular one is of the order of one century

use of sentinel 2 images for the detection of precursory motions before landslide failures abstract the sentinel 2 optical satellites provide a global coverage of land surfaces with a 5 day revisit time at the equator we investigate the ability of these freely available optical images to detect precursory motions before rapid landslides a 9 month time series of displacement is derived from sentinel 2 data over a major landslide in the french alps which exhibited a sudden reactivation in june 2016 this analysis reveals a 7 month period of low activity 1 m followed by a sudden acceleration of 3 2 1 2 m in 3 days before the failure of a mass of about 2 to 3 6 106 m3 the location of this precursory motion is consistent with that of the slow motions occurring since 2001 about 1 m year as revealed by aerial photographs and lidar analysis this change in activity over a very short period of time days emphasizes the value of the frequent revisit time of sentinel 2 despite its medium resolution of 10 m we finally simulate the ability of sentinel 2 for detecting these precursory patterns before a rapid landslide occurs based on typical voight s laws for creeping materials characterized by a power law exponent based on this analysis and on global cloud cover maps we compute the probability to detect pre failure motions of landslides using the sentinel 2 constellation this probability is highly heterogeneous at the global scale affected by the revisit time of the satellite and the cloud cover however the main factors controlling this detection ability are the properties of the landslide itself its size and the parameter with almost 100 of detection probability for 1 3 and 0 for 1 8 despite all these limitations probability to detect a motion before a landslide failure often reaches 50 for classical landslide parameters these results open new perspectives for the early warning of large landslide motion from global and open source remote sensing data

morphology structure and kinematics of a rainfall controlled slow moving andean landslide peru the large slow moving landslide of maca is located in the upper colca valley southern peru a region characterized by a well pronounced rainy period and intense and recurrent sustained seismicity the landslide developed in deep lacustrine deposits has recently accelerated threatening the maca village this work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation acceleration we present a multidisciplinary characterization of the maca landslide that includes i geological and morphological mapping in the field ii remote sensing analysis using an historical aerial photograph of 1955 and the pleiades satellite images 2013 iii global positioning system gps including time series of surveys over 13 years and continuous measurements over 14 months iv a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass our study shows that this 60 mm3 landslide which can be classified as a clay silt compound landslide moved by 15 m between 2001 and 2014 with a large inter annual velocity variation up to a factor of 500 depending on the rainfall intensity we suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in peru this study reveals three main driving factors acting at different timescales i over several decades the river course has significantly changed causing the maca landslide reactivation in the 1980s due to the erosion of its toe ii at the year scale a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity iii transient changes in slide velocity may occur anytime due to earthquakes this study particularly highlights the non linear behaviour of the motion with rainfall copyright 2016 john wiley sons ltd

detecting co seismic displacements in glaciated regions an example from the great november 2002 denali earthquake using spot horizontal offsets we use spot image pairs to determine horizontal offsets associated with the mw 7 9 november 2002 denali earthquake in the vicinity of slate creek ak field measurements and aerial photographs are used to further characterize the geometry of the surface rupture aerial photographs show that shear localization occurs where the rupture trace is linear and distributed off fault deformation is common at fault bends and step overs or at geologic contacts between rock glacial sediments and ice the displacement field is generated using a sub pixel cross correlation technique between spot images taken before and after the earthquake we identify the effects of glacier motion in order to isolate the tectonic displacements associated with the denali earthquake the resulting horizontal displacement field shows an along strike variation in dextral shear with a maximum of approximately 7 5 m in the east near 144 52 w which decreases to about 5 m to the west near 145 45 w if the november 2002 earthquake represents the long term behavior of the denali fault it implies a westward decrease in the long term dextral slip rate a possible mechanism to accommodate the westward decreasing slip on the denali fault is to transfer fault slip to adjacent east trending contractional structures in the western region of the central alaskan range

some consequences of a flood tide front in loch creran abstract loch creran is a small scottish sea loch with two basins which are connected by a shallow narrows a sharp front that forms just inside the narrows during flood tides producing a simple mechanism for flushing the top brackish layer of the inner basin the mechanism is shown to be consistent with temperature and velocity data conservation equations are used with salinity data to estimate mixing and entrainment rates and thus the energy used a bottom drag coefficient for the narrows is estimated from the tidal signals of velocity and pressure gradient and the turbulent kinetic energy entering the inner loch from the narrows is calculated so that finally a value for the flux richardson number the fraction of available energy used by mixing and entrainment can be given

the dynamics of a bathymetrically arrested estuarine front abstract the mixing and circulation associated with a bathymetrically arrested estuarine front was studied using hydrographic and current data a quasisteady front exhibiting strongly convergent surface flows is formed along the steeply sloping inner margins of the flood tide delta during each semidiurnal tide cycle this front separates the brackish ambient water within a deep estuarine basin from the incoming oceanic tidal water the position of the front is dependent on the local water depth and the difference in density between the two water masses beneath the surface there is an inclined frontal interface where static stability is very low and vertical mixing intense a vertically integrated horizontal momentum equation was derived for flow in the upper layer and an estimate made as to the value of the associated entrainment coefficient

fault zone controls on the spatial distribution of slow moving landslides slow moving landslides earthflows can dominate hillslope sediment flux and landscape erosion in hilly terrain with mechanically weak fine grained rock controls on the occurrence of slow moving landslides are poorly constrained and need to be understood for landscape evolution models sediment budgets and infrastructure and hazards planning here we use airborne interferometric synthetic aperture radar insar and aerial photographs to document 150 previously unidentified active earthflows along the central creeping portion of the san andreas fault california the earthflows move seasonally in response to winter rainfall occur on hillslopes at 20 40 gradients less than typically associated with rapid catastrophic landslides and have similar morphological characteristics to earthflows in different climatic and tectonic settings although our data extend up to 10 km from the fault trace 75 of detected landslides occur within 2 km of the active fault topographic precipitation and rock type metrics alone are not enough to explain the observed spatial distribution of earthflows instead we hypothesize that earthflows cluster near the creeping san andreas fault because of a fault induced zone of reduced bulk rock strength that increases hillslope susceptibility to failure in addition similar lithology topography and climate exist north of the creeping section of the fault yet earthflows there are rare this may be due to large magnitude earthquakes episodically triggering coseismic rapid landslides which preferentially remove weak rock from the fault damage zone our analysis suggests that the necessary conditions for earthflow formation in central california include some combination of reduced rock strength fine grained sedimentary rock threshold precipitation and relief and possibly the absence of large magnitude earthquakes these conditions likely hold for earthflow development in other areas and our work suggests that local variations in rock strength and seismicity such as those associated with fault zones need to be taken into account in order to accurately predict earthflow occurrence

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

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

geologic interpretation of the near infrared images of the surface taken by the venus monitoring camera venus express we analyze night time near infrared nir thermal emission images of the venus surface obtained with the 1 m channel of the venus monitoring camera onboard venus express comparison with the results of the magellan radar survey and the model nir images of the beta phoebe region show that the night time vmc images provide reliable information on spatial variations of the nir surface emission in this paper we consider if tessera terrain has the different nir emissivity and thus mineralogic composition in comparison to the surrounding basaltic plains this is done through the study of an area sw of beta regio where there is a massif of tessera terrain chimon mana tessera surrounded by supposedly basaltic plains our analysis showed that 1 m emissivity of tessera surface material is by 15 35 lower than that of relatively fresh supposedly basaltic lavas of plains and volcanic edifices this is consistent with hypothesis that the tessera material is not basaltic maybe felsic that is in agreement with the results of analyses of vex virtis and galileo nims data if the felsic nature of venusian tesserae will be confirmed in further studies this may have important implications on geochemical environments in early history of venus we have found that the surface materials of plains in the study area are very variegated in their 1 m emissivity which probably reflects variability of degree of their chemical weathering we have also found a possible decrease of the calculated emissivity at the top of tuulikki mons volcano which if real may be due to different more felsic composition of volcanic products on the volcano summit

the tidal intrusion front an estuarine convergence zone freshwater discharge in a small estuary flows seaward as a density current which is forced back into the estuary during the flood phase of the tidal streams the development of the two layer flow and the associated frontal structure is described the front exhibits a v configuration with an isolated point convergence at its apex and an associated gyre system

maximal two layer exchange over a sill and through the combination of a sill and contraction with barotropic flow the analysis of two layer exchange flow through contractions with a barotropic component treated by armi farmer 1986 is extended to include exchange flows over sills and through a combination of a sill and contraction it is shown that exchange over a sill is fundamentally different from exchange through a contraction control at the sill crest acts primarily through the deeper layer into which the sill projects and only indirectly controls the surface layer this asymmetry in the control results in asymmetrical flows the interface depth above the crest is not one half the total depth as assumed in other studies by analogy with flow through contractions but is somewhat deeper the maximal exchange rate is less than for flow through a contraction of equal depth when both a sill and a contraction are present the contraction influences control at the sill crest only if it lies between the sill and the source of denser water the response to barotropic flow is also asymmetrical the transition to single layer flow occurs at much lower speeds for a barotropic component in one direction than the other results of the analysis are applied to exchange flow through the strait of gibraltar which includes both a sill and a contraction it is shown that maximal exchange conditions apply throughout part of the tidal cycle and observations illustrate several of the analytical predictions for barotropic flows including the formation of fronts single layer flow submaximal exchange and reverse flow

landslide patterns reveal the sources of large earthquakes the distribution of fault slip in an earthquake controls seismic surface deformation and ground shaking and is the most direct record of fault response to tectonic stress detailed information about slip patterns in large earthquakes is only available where a dense local network of seismometers is in place elsewhere the evaluation of earthquake source and mechanism relies on observation of proxies such as surface change or damage intensity in upland areas the density of seismically induced landslides is strongly influenced by the intensity and duration of strong ground motion and therefore contains information about the earthquake source mechanism here we show that density patterns of co seismic landslides closely track the distribution of fault slip in two large thrust earthquakes in japan when adjusted for site effects landslide distributions readily obtained from remote sensed images can supplement or replace instrumental records of earthquakes opening historical and remote events for close geophysical investigation

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

glacier surface velocities in alpine terrain from optical satellite imagery accuracy improvement and quality assessment the worldwide retreat of mountain glaciers has important consequences for the water food and power supply of large and densely populated areas in south and central asia successful mitigation of the hydrological impacts on societies as well as assessing glacier related hazards require large scale monitoring of glacier dynamics however detailed glaciological data from the asian highlands are lacking due to its size and difficult accessibility we have applied a novel technique for precise orthorectification co registration and sub pixel correlation of advanced spaceborne thermal emission and reflection radiometer aster satellite imagery to derive surface velocities of himalayan glaciers our approach allows for the correction of offsets due to attitude effects and sensor distortions as well as elevation errors if a digital elevation model dem from the shuttle radar topography mission srtm was used for orthorectification after post processing the error on the displacements is on the order of 2 4 m per correlation translated into annual velocities this error is reduced increased when the correlated images are more less than a year apart through application of a filtering procedure and several quality tests the consistency of the results is validated to provide confidence in the remotely sensed velocity measurements despite the lack of ground control this novel approach allows fast easy and economically viable acquisition of detailed glaciological data in areas of difficult access and provides a means for large scale monitoring of glaciers in high mountainous terrain

global patterns of loss of life from landslides global loss of life from landslides is poorly quantifi ed a global data set of fatalities from nonseismically triggered landslides that resulted in loss of life between a d 2004 and 2010 permits for the fi rst time proper quantifi cation of impacts and spatial distributions in total 2620 fatal landslides were recorded worldwide during the 7 yr period of the study causing a total of 32 322 recorded fatalities these total numbers of landslides and victims are an order of magnitude greater than other data sets have indicated but analysis of the data suggests that it may still slightly underestimate the true human costs the majority of human losses occur in asia especially along the himalayan arc and in china this geographical concentration dominates the annual landslide cycle which peaks in the northern hemisphere summer months finally numbers of fatalities per event show a fat tailed power law distribution with the density of landslides being moderately correlated with the population density on a national basis

controls on the seasonal deformation of slow moving landslides article history precipitation drives seasonal velocity changes in slow moving landslides by increasing pore water pressure and reducing the effective normal stress along basal shear zones this pressure change is often modeled as a pore water pressure wave that diffuses through the landslide body such that the minimum time required for landslides to respond to rainfall should vary as the square of landslide depth which often approximates the saturated thickness and inversely with hydraulic diffusivity here we assess this model with new observations from the landslide prone eel river catchment northern california using satellite radar interferometry insar time series precipitation data and high resolution topographic data from airborne lidar we quantify the seasonal dynamics of 10 slow moving landslides which share the same lithologic tectonic and mediterranean climate conditions these slope failures have areas ranging from 0 16 to 3 1 km 2

flow convergence and stability at a tidal estuarine front acoustic doppler current observations characteristics of the flow field in an estuarine frontal zone have been investigated in a field study in the lower james river estuary underway sampling with an acoustic doppler current profiler adcp on repeated transects across the front provided information on the structure of the flow field near the front and its evolution in time as this tidal intrusion front advanced up the estuary during the flooding tide prominent and consistent features in the velocity field included a localized zone of convergent flow beneath the visible surface line and a stratified shear layer just upriver of the front within the shear layer between the buoyant surface water and the faster higher salinity undercurrent gradient richardson number estimates suggest that the flow was at or near the threshold for shear instability another shear type gradient in the flow field the across front variation of the along front velocity component strengthened over a sequence of transects with intensity increasing toward the surface tracking of the front was then interrupted when the identifying line of foam and accumulated material on the surface previously sharp and well defined broke up and dispersed to such an extent that the visible signature of the front was lost temporarily a visible frontal expression later reappeared and propagation upriver continued lower bound estimates of downwelling flow in the frontal zone were determined by continuity considerations

correlation of satellite image time series for the detection and monitoring of slow moving landslides abstract slow moving landslides are widespread in many landscapes with significant impacts on the topographic relief sediment transfer and human settlements their area wide mapping and monitoring in mountainous terrain however is still challenging the growing archives of optical remote sensing images offer great potential for the operational detection and monitoring of surface motion in such areas this study proposes a multiple pairwise image correlation mpic technique to obtain a series of redundant horizontal displacement fields and different multi temporal indicators for a more accurate detection and quantification of surface displacement the technique is developed and tested on a series of monoscopic and stereoscopic pleiades satellite images at a test site in the south french alps empirical tests confirm that mpic significantly increased detection accuracy f measure 0 85 and that the measurement error can be reduced by averaging velocities from all pair combinations covering a given time step i e when stereo pairs are available for at least one date the derived inventory and displacement fields of 169 slow moving landslides show a positive relationship between the landslide size and velocities as well as a seasonal acceleration of the largest landslides in response to an increase in effective precipitation the processing technique can be adapted to better exploit increasingly available time series from a variety of optical satellites for the detection and monitoring of landslide displacement