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Rock falls, rock slides and rock avalanches are natural or anthropogenic phenomena, mostly result of unstable rock slopes. So to determine the stability of a slope mass, rock mass classification systems are often used in rock engineering practices. Slope Mass Rating (SMR) is an efficient rock mass classification system to access structurally controlled stability of natural and engineered rock slopes. The SMR system is an adaptation of Rock Mass Rating (RMR) system and is calculated by adding corrections factors to the basic RMR. The correction factors depend on the interrelation of existing joints in a slope with respect to the slope geometry and excavation method. The conventional method of determining SMR includes the collection of slope and joint orientations followed by determination of planes and/or line of intersections of wedges responsible for kinematic instability. Then the correction factors are assigned to the most unfavourable planes and/or wedges according to the discrete ratings proposed by Romana (1985) and Anbalagan et al. (1992).To ease the tedious process involved in SMR calculation, a GUI based windows application software, EasySMR, has been developed by the first author. The application itself determines kinematic feasibility from input discontinuities and slope orientation as well as friction angle followed by direct calculation of SMR using input basic RMR. The application checks the possibility of planar, wedge and flexural toppling failures by using the equations suggested by Leung and Kheok (1987) and simultaneously calculate SMR for all the unfavourable planes and wedges. The continuous functions given by Tomas et al. (2007) has been used to determine the correction factors. The program is also aided by statistical analysis of SMR for all the kinematic failures. The outputs of the software have been validated by manual calculations for 23 rock slopes. [ABSTRACT FROM AUTHOR]

Large rockslides are major landscape modifiers in Alpine valleys and may constitute a significant natural hazard. Previous research has shown that rock-slope failures generating catastrophic mass movements often cluster in space and time. An early Holocene rockslide clustering is often associated to glacier withdrawal leading to increased stresses within over-steepened slopes and enhanced seismicity. In contrast, during the Mid- to Late Holocene, potential trigger mechanisms for slope failures are pore pressure increase due to wet climate conditions or shaking during strong earthquakes. Although their timing and mass movement processes are often well studied, no conclusive interpretation for their main trigger can be extracted by directly studying the landslide scarp or its deposit.The small and shallow lake Piburgersee (0,14 km²; 29 m deep) is uniquely located in between a spatially and temporally (4.2 - 3.0 ka BP) cluster of six large rockslides in the Eastern Alps, containing e.g. the Fernpass and Tschirgant landslides and Köfels landslide (9.8 ka BP). Applying geophysical methods (Multi-beam bathymetry, subbottom profiling) in combination with multiple sediment analyses, such as X-CT, MSCL and µ-XRF scanning, grainsize and C/N measurements, and 14C age dating on two 12 m long piston cores allow to distinguish different environmental impacts affecting the lake sediments.Piburgersee is surrounded by a mountainous morphology consisting of metamorphic rocks and a rockslide deposit at one side, which is believed to have dammed the lake in Late Glacial times. The lake has only one basin and one surface inflow generating a small delta. Lacustrine organic-rich sedimentation started with the onset of the Holocene. Normal graded, detrital intercalations with high C/N ratios are interpreted as flood layers occurring on a centennial scale. Between 7.3 – 2.8 ka BP several thick event deposits are recorded in Piburgersee, which differ from the typical flood deposits: Three, up to 50 cm thick, sand-rich detrital deposits occurred in the period 4.5 - 6.9 ka BP suggesting a terrigeneous source such as a local rock slide or a debris flow. CT-images reveal three horizons bearing deformation structures and three intraclast breccia layers in the period 4.5 – 10.5 ka BP, which all possibly characterise a seismic event. A local rockfall impacted the lake at 2.8 +/- 0.2 ka BP generating a two meter thick deposit of remobilised lacustrine sediments with a deformed and potentially eroded base containing a local rock.Preliminary results show that within the period of rockslide clustering no event deposit hinting at seismic shaking is present, except the local rock fall which was potentially simultaneously triggered with the Tschirgant rockslide at 3.0 ka BP. Additionally an intraclast breccia layer potentially falls in the time range of the Köfels rockslide at 9.8 ka BP. Available data hints at a phase of enhanced flood activity and at least six strong earthquakes in the Early- to Mid Holocene preceding the landslide cluster and possibly acting as important pre-conditioning factors. Future investigations on a longcore of the nearly located Plansee will test this preliminary interpretation and further specify the main trigger mechanisms. [ABSTRACT FROM AUTHOR]

The south-eastern part of the Carpathian Mountains (region of Vrancea, Romania) is prone to high magnitude earthquakes (M>7) with deep hypocenters (60-200 km). It is known that the 1940 (M7.7) and 1977 (M7.2) Vrancea earthquakes induced several landslides. This region also presents numerous large slopes with morphologies which might be due to seismically induced failures of rather ancient origin. However, as already historical seismically induced landslides are poorly documented, proving the seismic origin of those older mass movement is even more complicated. The investigation and the characterisation of Romanian landslides may therefore lead to a better understanding of their origin, and could therefore make an important contribution to (supra-)regional seismic risk assessment. We focus our analysis on two sites in the Buzau region: the Eagle's Lake (Lacul Vulturilor) landslide and the Balta rock slide. In October 2018, we performed a geophysical survey on both sites. This included seismological array measurements to retrieve S-waves velocity profiles from surface waves dispersion properties. We identified the bottom of the landslide body from the estimation of the resonance frequency derived through horizontal-to-vertical noise ratio measurements. Active seismic measurements, i.e. seismic refraction tomography and multichannel analysis of surface waves, were carried out to obtain, respectively, P-wave velocity profiles identifying lateral contrasts in soil properties, and shear-wave velocities in the subsurface. In addition, drone flights were used to establish a 3D model of the investigated sites. These combined measurements form a rich dataset and are used to retrieve the geometry of the landslides as well as to provide an estimation of the volumes of the failed material. This work, perspectively, aims at reconstructing the conditions and the energy needed for triggering these landslides, in order to understand the seismic component, if applicable, in the failure process. [ABSTRACT FROM AUTHOR]

Ocean island volcanoes are dynamic geological structures. Their shape changes rapidly as they evolve through complex interactions among eruptions, magma intrusions, tectonics, mass wasting and subaerial erosion. The central volcanoes of the Azores islands (North Atlantic Ocean) show a wide variety of morphologies, ranging from conical edifices to incremental caldera complexes. In the absence of geochronological constraints on morphological changes we use a multidisciplinary approach combining morpho-structural analysis with seismicity, rock geochemistry and petrography to better constrain the model of the summit evolution of Pico Volcano. After the subaerial shield-building stage, this volcano grew up to 2351 m asl as a cone-shaped edifice with steep slopes (in excess of 40°) and without lateral cones above ~1500 m asl. An older crater, now defined by a plateau at 2060-2010 m asl, formed southwest of the present summit. Subsequent dominantly effusive activity reconstructed a new volcanic cone slightly offset to NNE. This new summit was later truncated by a sub-circular pit-crater (550-m-wide), nowadays with a preserved crater wall on the SW and collapsed sector on the NE. The pit-crater was then partially occupied by the pahohehoe lavas of a 110-m-high spatter/lava cone (known as Piquinho). During the last summit eruption a 800-m-long ENE-WSW eruptive fissure cut Piquinho cone and the crater wall producing a small volume of scoria. The upper northern and eastern flanks show active rock slides that removed the NE half of the crater wall and formed debris-filled ravines. The southern edge of the older crater also shows ongoing geomorphological instability characterized by traction fissures and fresh ravines. Overall, two types of lavas were emitted contemporaneously in recent times by the whole volcano: olivine-and-clinopyroxene-bearing basalts (type A) were mostly erupted from lateral vents along different fracture systems intersecting the volcano, while plagioclase-bearing basalts and trachybasalts (type B) erupted almost exclusively from the summit. Therefore, two feeding systems were active simultaneously in Pico Volcano. Type A magmas ascended directly from the Moho Transition Zone through dyke intrusions, while type B magmas mostly formed in a shallow reservoir, believed to be the source of the frequent low-magnitude earthquakes (M ≤2) recorded at depths between 4 and 7 km. This reservoir should be located beneath the southern flank of the volcano, between the older crater and the coastline, and its position suggests a SSW dipping central conduit system linking it to the summit area.This work was financially supported by the Fundação para a Ciência e Tecnologia (Portugal) through project MARES (PTDC/GEO-FIQ/1088/2014). [ABSTRACT FROM AUTHOR]

Glacier retreat is one of the most significant consequences of 20th and 21st century temperature rise in the European Alps, most obvious at glacier tongues but also at glacier cirques. As cirque headwalls deglaciate, internal stress redistribution occurs and atmospheric forcing intensifies rendering deglaciating headwalls particularly prone to rock slope failure. Fractures intersecting these rock masses represent potential planes of weakness. Their dynamics may thus reveal information about the magnitude and timing of stability-relevant processes. The present study focuses on the need for quantitative data from unstable, recently deglaciated rock slopes, essential for better understanding the increasing risk on high-alpine infrastructure.Here, we investigate the deformation regime of an open fracture, which is of direct geotechnical relevance for a popular cable car station at the Kitzsteinhorn (3203 m a.s.l.). The fracture is situated immediately up slope of the detachment zone of a recent rock slide (2012) and was glacially covered until the 1980s. Two crackmeters are operated to measure horizontal and vertical crack deformation with a resolution of ±0.003 mm as well as crack top temperature. To decipher thermo-mechanical from cryogenic forcing, thermal expansion coefficients for both horizontal and vertical directions were calculated in order to model purely thermomechanical deformation. Based on a 2.5-year monitoring campaign, this study aims to decipher and quantify stability-relevant processes and their temporal occurrence, and addresses the following research questions: (i) Are fracture dynamics dominated by thermo-mechanical expansion/contraction of the inter-cleft rock mass? (ii) Do cryogenic processes, i. e. freeze-thaw dynamics and ice segregation, affect fracture opening/closing? (iii) Can irreversible crack deformation patterns and destabilisation be observed?(i) Fracture dynamics are dominated by thermo-mechanical expansion and contraction of the inter-cleft rock mass during sustained snow-covered and snow-free periods. Calculated thermal expansion coefficients of 7E-006 along and 14E-006 perpendicular to foliation highlight material anisotropy of the calcareous micaschist.(ii) Significant deviations from the thermo-mechanical deformation regime occur mainly during spring and autumn zero curtain periods due to freeze-thaw action. Peak vertical deformations are triggered by rainfall events providing liquid water onto the rock surface and into the fracture system. Subsequent refreezing rather than hydrostatic pressure build-up is assumed to cause the mechanical response of the rock. Lower magnitude deviations in the horizontal component arise in autumn and early winter, which are referred to segregation ice growth. Besides cryogenic processes, other mechanisms seem to affect fracture dynamics such as wedged rock fragments impeding maximum fracture-closing during snow-free periods.(iii) Irreversible fracture opening, pointing towards acute, high magnitude rock slope instability, was not observed. However, enhanced cryogenic deformation in spring and autumn may lead to shallow, low magnitude rock detachments. Our results highlight the importance of liquid water intake in combination with subzero-temperatures on the destabilisation of glacier headwalls. Randkluft systems may favour intense frost action and ice segregation, serving as important preparatory factors of paraglacial rock slope instability. [ABSTRACT FROM AUTHOR]

Himalaya is uplifting rapidly and have been modified by glacial and fluvial erosion and landslides. We investigated the geological and topographic characteristics of landslides aligned along the Kali Gandaki River, one of the largest rivers that flow from Tibet to India through High Himalaya. We made field survey, using PRISM image with a resolution of 5 m and 5-m ALOS AW3D. From the upstream to downstream, there are Dhampu, Talbagar, Kopchepani, Gadkhan, and Gadpar rockslides. The Dhampu rockslide is the largest with a volume of 3 km3 (Fort, 2000), of which deposits is represented by a mound on the left bank of the Kali Gandaki River and have been argued about its origin, moraine or landslide deposits. We found bedrock-like gneiss in the lower portion of the mound, which has irregularly shaped fractures with openings and jig-saw-fit rock fragments in the massive rock body. This strongly suggests that the mound is rockslide deposits. The structures within the deposits like the alignment of rock fragments and minor faults suggests that the deposits came from south or southwest. To the south of the deposits is an E-W-trending ridge, which is 1,000-m to 2,000-m high from the riverbed of the Kali Gandaki and has linear ridge-top depressions. The northern face of this ridge is a poorly-vegetated dip slope of gneiss, on which we see many bulges by gravitational buckling deformation. These facts suggest that the mound at Dhampu is the deposits of the landslide that occurred on the dip slope in the south and preceded by gravitational slope deformation of buckling type. This landslide once blocked the Kali Gandaki River and drastically changed the landscape upstream. Talbagar landslide occurred on the left bank just downstream of an outstanding knickpoint of the Kali Gandaki River, which knickpoint propagated from downstream forming a slope break and undercutting the nearby slopes. Talbagar landslide with a volume of 10 million m3 (Fort et al., 2010) is a rock compound slide with a rupture surface consisting of gneissosity that trends WNW-ESE and dips to N and high angle joints trending N-S. Talbagar landslide slid to WNW slightly diagonal to the strike of the gneissosity on a slope that had been undercut by the knickpoint propagation.r Kopchepani, Gadkhan, and Gadpar landslide occurred on the left bank of the Kali Gandaki River, where the slopes are mostly infacing slopes while the right bank slopes are dip slopes. The bedrock is two mica gneiss trending WNW-ESE and dipping NNE 45° to 60°. The knickpoint propagation described before made a slope break 200-400-m high above the riverbed. We found that the beds above the slope break toppled valleyward while the beds below it were not deformed. Kopchepani, Gadkhan, and Gadpar landslide occurred in the toppled rock mass above the break probably by earthquake shaking. On the contrary, the slopes on the right bank suffered from gravitational slope deformation and are rather smooth with hummocky surface. [ABSTRACT FROM AUTHOR]

The Flims mass movement is the largest one in the Alps. Its deposits reach a volume of about 9–11 km3 (CAPREZ 2008; POLLET & SCHNEIDER 2004) and recent datings show that its failure occurred during a period of warm weather conditions (IVY-OCHS et al. 2009). Next to the Flims mass movement another, slightly older (POSCHINGER 2005), rock slide took place near the village Tamins. The Tamins mass movement deposits were able to dam the Vorderrhein and Hinterrhein and the "Lake Bonaduz" was created. Calculations reveal a volume of 7,88 km3 and a water surface height of 724 masl. According to this assumption, the Flims impact produced a megaflood event with a 214±20 m high wave crest which reached regions up to 900–950 masl.The consideration of the flood wave was verified and improved by sedimentological and geophysical methods. In total, 20 samples of gravels and pebbles were taken from seven locations along the megaflood pathway. Those samples are seen as flood wave deposits and also contain proved sediments of the Bonaduz-Fm., which probably belongs to the megaflood event. Over 13,000 components were petrographically and morphologically analysed. Additionally, these analyses were compared with those of the riverbed gravels from the Vorderrhein, Hinterrhein valley and versam gorge. Furthermore, the grain size distribution of the assumed flood wave deposits were investigated and interpreted. The landscape of the northern part of the Tamins landslide deposits reveals morphological structures to capture the megaflood deposits. Because of that, this area was mapped with the focus on gravel and pebble occurrences. Additionally, the sediment fillings of the topological sinks were studied with three ERT (electrical resistivity tomography) transections with a summarized length of 1,7 km. The results enable the distinction between three deposition facies within the megaflood sedimentation. First of all, the pathway along the Vorderrhein and Rhein valley with the deposition of the Bonaduz-Fm. Secondly, the wave impact into the versam gorge and the sedimentation of the gravels between the limestone boulders of the Flims landslide main deposits. Thirdly, the inundation wave over the Tamins mass movement deposits and the filling of the topological sinks. The mapping and the ERT-survey support the assumption of the megaflood event as reason for the high sedimentation within the sediment sinks. In the area of Tamins, the gravel/pebble distribution and the morphological observations reveal a maximum flood wave impact height of 830 masl. This result supports the calculations of the maximum wave crest height at the beginning of the megaflood progression (SCHWENK 2017). Literature:CAPREZ, J. (2008): Das Flimser Bergsturzereignis: 3D-Geländerekonstruktion und Volumenberechnung mit Hilfe von GIS. – Diplomarbeit Zürich (unveröffentl.).IVY-OCHS, S., POSCHINGER, A. V., SYNAL, H.-A. & MAISCH, M. (2009): Surface exposure dating of the Flims landslide, Graubünden, Switzerland. – Geomorphology, 103, 1: 104–112.POLLET, N. & SCHNEIDER, J.-L.M. (2004): Dynamic disintegration processes accompanying transport of the Holocene Flims sturzstrom (Swiss Alps). – Earth and Planetary Science Letters, 221, 1-4: 433–448.POSCHINGER, A.V. (2005): Der Flimser Bergsturz als Staudamm. – Bull. angew. Geol., 10/1: 33–47. [ABSTRACT FROM AUTHOR]

Alpine hazards are a significant threat to alpine communities, infrastructure and economics and are expected to increase in the future. Climatic changes and population growth will enhance the risk caused by alpine mass movements requiring a precise understanding of the underlying processes. Due to high costs for maintenance and reinstallation of protective structures, clever early warning and anticipation strategies based on the process dynamics are agreed to be a key strategy for alpine societies in the near future.As part of the AlpSense-Project (www.landslides.geo.tum.de/alpsensebench) we observe a large preparing rock slide at the Hochvogel summit (2592 m a.s.l., Allgäu Alps). The Hochvogel is currently a benchmark site to gain insights into slope failure dynamics and for developing an effective early warning system.The main crack is two to eight metres wide and boulders are blocked in the crack in almost ten metres depth. The sliding mass has moved downward by about three metres compared to the back scarp edge. Analysis of historical ortho- and aerial images yield an elongation of the main crack length from 10 to 35 m from 1960 until now. In addition, almost 1.500 UAV photos have been used to generate a 3D model of the extended summit area which we used for tracing geomechanically relevant structures. After deviating a kinematic model, the volume of the potentially failing mass has been calculated. In total, geomechanically relevant cracks and weak layers are delimiting six separated subunits of 8.000 to 148.000 m³ which account for 260.000 m³ in total. The pre-deformation is yet not pronounced enough to decide on the expected volume. Since 2014 discontinuous extensometer measurements in the main crack were carried out to determine movement rates of the instable mass. The crack opened over 30 cm between 2014 and 2018 with movement rates of up to 1 cm/month. To improve the temporal resolution and in preparation of an early warning system eight vibrating wire gauges have been installed in July 2018 in the main and lateral cracks. Once a minute data are transmitted wireless to a safe server together with temperature and rain measurements from site. Here we demonstrate first results from a preparing alpine rock slope failure including a high-resolution movement record and corresponding geodetic, photogrammetric, seismic and gravimetric measurements. The comprehensive measurement design at the Hochvogel fosters our understanding of the process dynamics initiating alpine rock slope failures and will help to better predict events in future. [ABSTRACT FROM AUTHOR]

In June 2015 a flash flood caused by a failure of a natural dam originated by a hazardous large landslide in the Vere valley hit Tbilisi. 23 persons lost their lives and property damages were above $ 24 M. The catchment area is a region of high landslide susceptibility with a range of active and expectable processes with differing intensities/volumes. The event of 2015 must be seen as mega-event with recurrence periods of several 1000s of years or more. However, the landslide has created even more unstable conditions and weakened an already semi-stable system. As conclusion, the likelihood for medium to large subsequent events has risen significantly.Along with the planning of the reconstruction of the Tskneti-Samadlo-road and the Tskneti-Akhaldaba road some detailed geological investigations, e.g. large-scale engineering geological mapping, laser scanning, monitoring of groundwater level, deformation measurements etc. were carried out or are still in progress. Along with the reconstruction of the road an early warning system will be developed, tested and implemented.These first results brought some evidence of geological, hydrogeological and geotechnical setting in the Tskneti region and the types of processes (weathering, changes of water level) and landslides (rock slides, rockfalls, creeping etc.) that provided debris for the catastrophic event in 2015.Deformation measurements show ongoing movements on the surface as well as in large depths. Correlation with piezometric pressures might indicate movement acceleration in the future. UAV mapping and laser scanning are being used to identify areas of erosion and movements as well as failure volumes and deformations of retaining structures.Long term observations will have to be carried out and help for a better understanding of the slope. By analysing all measured data over a long period of time thresholds for an early warning will be defined, evaluated and updated. [ABSTRACT FROM AUTHOR]

Natural hazard and risk analysis are normally conducted based on a limited number of "credible worst-case scenarios", each with a corresponding probability. Such a scenario-based approach is computationally not too costly (in terms of number of simulations) and might seem more appropriate when there are few previous events in the region, giving limited opportunities to establish magnitude frequency distribution (MFD). However, uncertainties are not quantified and hazard zoning is simply made by a single line separating between no-hazard and hazard (at the best with a corresponding probability), and it is hard to relate the results to the safety classes based on a set of different probabilities of impact. An alternative to the scenario-based approach is a probabilistic approach (using event tree) where a large number of scenarios are analysed based on frequency distributions (uncertainties) included in all steps, e.g. for landslides, uncertainties in location, release, volume, configuration, etc. are included. The results of the various simulations are integrated in an event tree analysis to calculate exceedance probability maps, which are in turn adapted to various safety classes in the Norwegian Planning and Building Act.In the presented work we sketch a framework for the probabilistic approach to natural hazard analysis where both frequency distributions and uncertainties are included. In the absence of data or statistics on previous events, expert judgement is often needed to a large extent, among others to establish (discrete) frequency distributions. The approach may be used for several types of natural hazards. The framework is demonstrated by an example of rockslide hazard analysis. We also show how secondary effects (e.g. run-up of tsunami generated by subaerial rockslides) can be included in the framework. Factoring in probabilities in all stages implies that previously designated danger areas (based on a limited number of conservative scenarios) can be released. [ABSTRACT FROM AUTHOR]

This study is based on detailed monitoring data from a large DSGSD called Moosfluh instability, located at the current glacier tongue of the Great Aletsch Glacier (Switzerland). This about 100 Mm³ large, and up to 170 m deep toppling mode instability started to accelerate around 1990, presumably caused by increased rates of glacier ice downwasting at the landslide toe. In 2013 and 2014, when average velocities reached about 500-700 mm/a, we installed a high accuracy displacement monitoring system, composed of 2 robotized total stations measuring displacements at about 15 reflectors positioned within the active landslide, 4 GNSS stations, and 2 Time-Lapse cameras. In the fall of 2016 a dramatic increase in acceleration occurred, leading to velocities of individual landslide compartments of up to 12 m in 6 weeks. Optical imagery and digital image correlation revealed that this acceleration was caused by the rapid development of three secondary rockslide scarps, and that movement initiated at the toe of the slope and evolved upslope. To investigate the depths of movements and the subsurface kinematic mechanism in detail, we developed a new analytical model, which considers the time series of three-dimensional displacements and plunge angles of discrete points within the landslide. The application of this model leads to the conclusion that a transition from primarily toppling to sliding mode displacements occurred during fall 2016. We can trace the detailed evolution of individual compartments, showing that toppling/sliding ratios varied in both space and time. The secondary rockslides forming during this period have a depth of about 30-40 meters and volumes ranging between 1 and 5 Mm³. Planar sliding surfaces are expected to have developed at a major kink zone within the large toppling rock mass.This kinematic evolution observed at Moosfluh significantly impacts the corresponding hazard and risk assessment, as flexural toppling tends to be a self-stabilizing mechanism, whereas planar rockslides can potentially transition into catastrophic failures. The estimated potential runout length probabilities show that the main hazard would be created by the formation and subsequent breach of a rock avalanche dam in the Massa gorge below the tongue of the Great Aletsch Glacier. [ABSTRACT FROM AUTHOR]

In order to understand and identify the influence of the structure of the rock mass on rock slide formation and deformation processes, the highly active, deep-seated "Marzell" rock compound slide in the Ötztal valley (Tyrol, Austria) has been examined. The investigated rock slide is situated at the SE-facing slope above the Marzell valley glacier and measures about 400 m in width and 600 m in height (main scarp at 2850 m a.s.l.). Geologically, the rock slide is located within the fractured, foliated poly-metamorphic rocks of the Ötztal Crystalline basement (i.e. paragneisses, mica schists and banded amphibolites).A multi-disciplinary approach comprising of i) geological-geomorphological mapping, ii) tachymetric and GPS survey campaigns, iii) analyses of airborne laserscanning data (ALS), iv) analyses of historic and current ortho-images, and v) manual wire-extensometer measurements, was applied to reconstruct the rock slide evolution and to develop a geometrical-kinematical rock slide model. Given that rock discontinuities influence the geomechanical failure behaviour and thus the failure geometry, a major focus was set on rock mass characterization based on discontinuity mapping. Additionally, kinematical analyses considering the structural inventory was carried out to identify modes of rock mass failure and preliminary discrete element modelling (UDEC) was performed to study rock slide kinematics and failure mechanisms.Geomorphological features such as primary and secondary scarps, uphill and downhill facing scarps, graben structures, trenches and tension fractures indicate the evolution of two time-delayed rock slide systems. Geodetic survey results show a high recent activity of the rock slide of several decimetres per year. Based on the geological structures and the measured displacement rates, six individual rock slide slabs can be identified. These slabs are separated by discrete failure surfaces/shear zones that were formed partly or totally along pre-existing NNE-SSW and E-W trending fault systems. The detailed discontinuity analyses of foliation planes, joints, and brittle fault zones show a major influence on the rock slide failure mechanism, failure geometry and kinematics. Kinematically, the SE directed slope movement caused extensional structures near the head scarp (horst and graben, trenches, fractures) and to bulging and slope steepening at the lower part of the rock slide. Results from the numerical 2-D discontinuum model are discussed with respect to: i) the structural influence on failure geometry (from pre-failure to current failure state), ii) the internal structures (e.g. horst and graben) and deformation behaviour of the sliding mass, and iii) the existence and formation process of a basal shear zone. [ABSTRACT FROM AUTHOR]