Search

We explore the viability of modeling dynamic problems with a new formulation of an impulse‐based Level‐Set DEM (LS‐DEM). The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in a rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse‐based LS‐DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The new formulation significantly improves the performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example. [ABSTRACT FROM AUTHOR]

Debris avalanches and dry granular flows exhibit similar characteristics. In order to comprehend the fundamental mechanisms and improve the accuracy in predicting disasters such as landslides, debris flows, and rock avalanches, the collapse characteristics of a binary granular column are investigated through a three‐dimensional discrete element model. A novel approach is proposed by incorporating the concept of local granular velocity fluctuation and applying a cluster analysis method. Then, the flow mechanism of the binary granular column is analyzed, by considering the inhomogeneous particle size distribution. The research results show that: (1) The normalized final packing height of the granular column gradually increases when the content of coarse particles exceeds 20% and when the coarse‐fine particle size ratio increases. Conversely, the normalized run‐out distance of the granular column decreases gradually with the increase in coarse particle content and the coarse‐fine particle size ratio. (2) The particles with higher granular velocity fluctuations tend to move together and form clusters, demonstrating dynamical heterogeneity. As the coarse particle content and coarse‐fine particle size ratio increase, there is a greater tendency for particles to assemble into larger‐scale active clusters. This means that a larger number of particles exhibit collective behavior during the collapse process, resulting in increased resistance to shear deformation. Ultimately, this leads to a greater packing height and a reduced run‐out distance when observed from a macroscopic perspective. [ABSTRACT FROM AUTHOR]

This study presents the Flexible Rocking Model on Concentrated Springs (FRMCS), developed to investigate 2D laterally flexible oscillators rocking and sliding on deformable support media during ground excitations. In this model, concentrated vertical springs and viscous dampers simulate the contact forces from support medium at the corners of the body; the tensionless vertical contact element is linear in compression. Horizontal concentrated springs and linear viscous dampers simulate the frictional behaviour at the corners; the constitutive law for the springs models elastic deformations and sliding (according to Coulomb's friction law). With these elements, FRMCS can model the response of a rocking body which can experience sliding and free‐flight phases of motion. The consideration of the flexibility of the support medium enables the evaluation of the forces exerted by the support medium on the structure during an impact. In this study, the FRMCS response is first compared to a previous model where the support medium deformability and the effects of sliding and free‐flight are ignored. Then, the responses of four configurations, which feature either stiff or soft lateral springs and stiff or soft high‐grip support media, are examined under the influence of pulse excitations. Finally, to understand the potential influence of sliding, a configuration with a low‐grip support medium is explored. The comparative influence of lateral flexibility and support medium deformability and sliding is quantified with stability diagrams and various response spectra, describing structural force and moment demands. [ABSTRACT FROM AUTHOR]

Two major earthquakes of Mw7.8 and Mw7.5 ruptured the Southern East Anatolian Fault (SEAF) and the Savrun‐Çardak‐Sürgü fault (SCSF), devastating southeast Türkiye and northwest Syria on 6 February 2023. We adopt innovative nonlinear and linear approaches to analyze the coseismic ground displacements and estimate the complex slip geometry. Unlike conventional analytical solutions that simplify crust heterogeneity, finite‐element fault models invert the displacement data and simulate the dual‐fault geometry with non‐uniformly distributed shallow crustal materials. Our results suggest the west‐dipping SEAF and north‐dipping SCSF accommodate earthquake slips of >10 m. Their respective slip distributions and proximal aftershocks correlate spatially with local seismic velocity anomalies (i.e., ΔVp and ΔVs), which implies differences in structural control along these two faults and provides insights into assessing the seismic hazard of mixed incipient‐mature fault systems. Plain Language Summary: In early February of 2023, southeast Türkiye and northwest Syria experienced two devastating earthquakes that claimed more than 50,000 lives and caused substantial economic loss. The epicenters are located near the active tectonic boundary between the Anatolian and Arabian Plate. The complex seismic rupture occurred over two faults, the Southern East Anatolian Fault (SEAF) and the Savrun‐Çardak‐Sürgü Fault (SCSF). Satellite interferometric images and global positioning networks capture large‐scale ground movements. Our study adopts a novel approach to analyze the slip pattern and explore the fault orientation and slip distribution. The result highlights that the fault rupture, aftershock, and local velocity anomalies are correlated, but the correlation pattern differs between the SEAF and SCSF. This improves our understanding of the earthquake hazard along the plate boundaries that host faults of different maturity levels. Key Points: Coseismic slip distribution of the 2023 Kahramanmaraş Earthquake is estimated from the ground displacements observed by SAR and global navigation satellite system dataInnovative nonlinear‐crossover‐linear inversion method combined with finite element elastic models simulating rock heterogeneityEarthquake slips and aftershocks correlating spatially with velocity anomalies imply structural controls and different fault maturity [ABSTRACT FROM AUTHOR]

Although numerous recent studies have explored the relationship between permafrost degradation and rock slope failure, there is still a need for in‐depth investigations to develop relevant hazard assessment approaches. We investigate the predisposing, triggering and propagation processes of a rock avalanche (c. 225,000 m3) that occurred in Vallon d'Étache (France) on 18 June 2020, whose scar was coated by ice and water. Weather records and energy balance models show that the rock avalanche occurred right after the warmest spring and winter since at least 1985, but also right after the spring with the highest water supply anomaly (snowmelt and rainfall). Measured ground surface temperature and geoelectrical surveys reveal that relatively ice‐rich permafrost could exist in the NW face (release area) while it is inexistent below the SE face, contradicting certain permafrost maps. Heat transfer simulations suggest that the rock avalanche occurred during a transition from cold to warm permafrost conditions at failure depth (30 m), with a temperature increase of up to 0.6°C per decade since 2012 (when considering potential snow cover effect), and current temperature ranging between −3 and −1°C, depending on the applied model forcing. This warming certainly contributed to predispose slope to failure. In addition, the shift towards warm permafrost and water infiltration potentially enhancing permafrost degradation along fractures through heat advection or favouring the development of high hydrostatic pressures may have played as triggering factors. Finally, propagation simulations show that the rock avalanche involved several phases with different rheological properties due to the incorporation of snow and material segregation within the deposit. These new insights at various scales highlight the complexity of the triggering and propagation processes of rock slope failure occurring in high mountains, a significant part of which can be linked to snow effects on ground temperature, water supply and rheological properties. [ABSTRACT FROM AUTHOR]

Natural fault zones are complex, spatially heterogeneous systems. Rock deformation experimental studies simplify the complexity of natural fault zones either as a surface discontinuity between intact rocks (bare‐rock surfaces) or as a few mm‐thick gouge layer. However, depending on the simplified fault type and its slip history, the response to applied deformation can vary. In this work, we conduct laboratory experiments for investigating the evolution of mechanical parameters of simulated faults made of calcite gouge subjected to multiple (four) identical seismic slip‐rate pulses. We observed that, as the number of applied slip‐rate pulses increased, (a) initial friction and steady‐state friction remained approximatively constant, (b) peak friction and normalized strength excess increased and, (c) the slip distances to achieve peak and steady‐state friction, Da and Dc, decreased. The greatest changes occurred between the first and the second slip‐rate pulse. From this pulse onward, the dissipated energy of the calcite gouge fault was similar to those obtained in bare‐rock surfaces experiments. Microstructural analysis showed that, strain is localized in up to two (recrystallized) principal slip zones (PSZ) with sub‐micrometric grain size, surrounded by low porosity sintered and non‐sintered comminuted gouge domains. We conclude that previous seismic slip episodes impact on both the structure and the strain localization processes within a fault, contributing to its shear fabric evolution. We highlight that the strain localization process identifies the PSZ, dissipating the least amount of energy within the entire experimental fault zone. Plain Language Summary: Earthquakes are caused by the propagation of seismic ruptures and sliding of rocks along geological structures called faults. Within the fault, seismic ruptures propagate in mm‐cm thick slip zones that cut cm‐ to meters‐thick fault cores. Both slip zones and fault cores typically exhibit microstructural assemblages different from those of nearby rocks. Laboratory experiments are used to investigate the processes that result in the decrease of fault strength with slip and slip‐rate and govern seismic rupture propagation. However, experiments are performed on simplified fault cores consisting of either a surface discontinuity between intact rocks (i.e., slip zone = "bare‐rock surfaces") or a mm‐thick layer of powdered rocks (i.e., slip zone in a "fault gouge"). In this work, we investigate how slip zones form and evolve in an experimental fault (gouge) core depending on seismic slip history. We apply repeated pulses of seismic slip and show that (a) in the first pulse a slip zone with similar microstructure and friction properties to bare‐rock is formed, (b) in subsequent pulses these slip zones are abandoned and new slip zones are formed in the fault core. Notably, these structural changes, occur to minimize the mechanical energy dissipated in the FC. Key Points: Friction experiments applying up to four consecutive seismic slip‐rate pulses (1 m/s), in fault gouge and bare‐rock surfacesThe greatest changes in dissipated energy occurred between the first and the second slip‐rate pulseStrain localization in the principal slip zones minimizes the energy dissipated within the whole experimental fault zone [ABSTRACT FROM AUTHOR]

Determining the shear‐velocity dependence of dry granular friction can provide insight into the controlling variables in a dry granular friction law. Some laboratories believe that the quality of this study is at the forefront of the discipline for the following reasons. Results suggest that granular friction is greatly affected by shear‐velocity (v), but shear experiments over the large range of naturally occurring shear‐velocities are lacking. Herein we examined the shear velocity dependence of dry friction for three granular materials, quartz sand, glass beads and fluorspar, across nine orders of magnitude of shear velocity (10−8–2 m/s). Within this range, granular friction exhibited four regimes, following a broad approximate "m" shape including two velocity‐strengthening and two velocity‐weakening regimes. We discuss the possible physical mechanisms of each regime. This shear velocity dependence appeared to be universal for all particle types, shapes, sizes, and for all normal stresses over the tested range. We also found that ultra‐high frequency vibration as grain surfaces were scoured by micro‐chips were formed by spalling at high shear velocities, creating ∼20 μm diameter impact pits on particle surfaces. This study provides laboratory laws of a friction‐velocity (μ‐v) model for granular materials. Plain Language Summary: Numerous phenomena of earth science can be simplified to shearing granular systems, such as landslide gouge and rock avalanches. It is believed that friction varies with shear velocity, and this is no exception for dry granular materials. Studying the law of friction variation over as large a range of velocity changes as possible aids in establishing a full life‐cycle hypothesis for landslides from initiation, through movement to cessation. We sheared granular materials across nine orders of magnitude, from 10−8 to 2 m/s and obtained an "M" shape law for the variation of friction with velocity. By analyzing the acoustic frequency of shear experiments at different velocities, we discovered that the acoustic frequency increased with shear velocity. By comparing the microscopic morphology of the particle surface before and after high‐velocity shearing, we hypothesized that the impact pits may be left by particle collisions during high‐velocity shearing. We proposed that the role of ultra‐high frequency vibration on high‐velocity shear weakening should be considered, which provides a basis for accurately revealing the physical mechanism of granular friction variation with velocity. Key Points: This paper examines the shear velocity dependence of friction for dry granular materials, across nine orders of magnitude in shear velocity (10−8–2 m/s)An "M‐shaped" law for the variation of friction with velocity is obtained including two velocity‐strengthening and two velocity‐weakening lawsThere is microscopic evidence that ultra‐high frequency vibration may cause high velocity shear weakening [ABSTRACT FROM AUTHOR]

Herein, fast fracture initiation in glacier ice is modeled using a Material Point Method and a simplified constitutive law describing tensile strain softening. Relying on a simple configuration where ice flows over a vertical step, crevasse patterns emerge and are consistent with previous observations reported in the literature. The model's few parameters allows identification of a single dimensionless number controlling fracture spacing and depth. This scaling law delineates two regimes. In the first one, ice thickness does not play a role and only ice tensile strength controls the spacing, giving rise to numerous surface crevasses, as observed in crevasse fields. In this regime, scaling can recover classical values for ice tensile strength from macroscopic field observations. The second regime, governed by ice bending, produces large‐scale, deep fractures resembling serac falls or calving events. Plain Language Summary: In ice sheets and alpine glaciers, fast‐flowing sections are often characterized by crevasse fields that play a significant role in the cryo‐hydrologic system by facilitating meltwater flow, enhancing basal sliding, weakening the ice, and impacting glacier thermodynamics. Modeling these fractures at the glacier scale remains challenging and often necessitates integrating diverse models which hinders the straightforward consideration of physical issues associated with crevasse fields on a large scale. Here, a new numerical framework allows us to conduct field‐scale experiments and paves the way for a scaling law to elucidate the macroscopic factors influencing fracture fields and to easily incorporate crevasse depth and spacing into large‐scale models. A newly discovered scaling law highlights the transition between a mechanical behavior where the regular crevasse spacing is unaffected by geometry to a regime where geometry plays a significant role, particularly in large‐scale fracture processes like glacier calving. While the numerical experiments in this paper focus on glaciers, the model and conceptual framework is versatile and can address the mechanical behavior of fractures in broader geophysical contexts such as snow, rock or ice avalanches, tectonics and landslides. Key Points: Fractures in glacier flow are modeled using material point method with elastoplasticity and tensile strain softeningA dimensional analysis reveals a key dimensionless number characterizing two different regimes of fast fractureOne regime predicts acknowledged ice tensile strength from field observations and characterizes the regular crevasse spacing [ABSTRACT FROM AUTHOR]

Many landslide models assume a fully deformable body without any resistance against deformation. However, in reality, landslide bodies can display negligible to large deformation during motion. Examples for limited deformation include the prehistoric giant landslides of Flims and Köfels, or the Vajont landslide of 1963, where the structure of rock largely remained intact and the slides did not evolve into rock avalanches. Here, we propose a novel mechanical model for the controlled deformation of landslides. The model is based on the principle of material strength or resistance and includes a user‐specified function that reflects the mechanisms (internal friction, cohesion, viscosity, and yield strength) that act against the deformation induced by the free‐surface or the hydraulic pressure gradient of the landslide. This controls the landslide deformation and, in turn, also the motion and run‐out, and offers a unique possibility to describe the landslide motion ranging from a fully non‐deformable body sliding along the mountain slope to a completely fluidized motion without any resistance against the force associated with the free‐surface pressure gradient. The latter is the situation often considered for the motion of granular flows such as avalanches of snow or rock, or debris flows. The former can play a substantial role in the dynamics, however, has not yet been considered in mass flow simulations, severely limiting the applicability of those models. We demonstrate the performance of the new model and its applicability, also with the advanced open‐source computational mass flow simulation tool r.avaflow. Plain Language Summary: When simulating the movement of landslides on a computer, most of the models which have been used until now assume a very strong deformation of the moving mass, almost like flowing water. However, this is only suitable for some landslides, but not for all. Many landslides rather move as rigid blocks rather than flowing water. Here, we introduce a simple mechanical model for the controlled landslide deformation which is able to automatically simulate landslides moving as rigid blocks, and also landslides which behave in a way that is in between a rigid block and flowing water. We integrate this model in a computer program which is freely available to use, and present some tests on simple computer‐generated landscapes to demonstrate that the model is working well. Key Points: We propose a novel mechanical model for the controlled deformation of landslidesThe model is based on the principle of material strength acting against the deformation induced by the hydraulic pressure gradientThis offers a unique possibility to describe the landslide ranging from a fully non‐deformable body to a completely fluidized motion [ABSTRACT FROM AUTHOR]

We examined the possible factors affecting the spatial distribution of very low frequency earthquakes and tremors in the shallow megathrust of Nankai Trough (<30 km) using a dense network of prestack depth migrated profiles at the frontal wedge. Geometrical parameters examined were decollement roughness, taper angle, and underthrust thickness. Physical properties such as effective basal friction (μb) and pore pressure ratio (λ*) were calculated from the taper angle and p‐wave velocity. Regions of low λ* (0.39 ± 0.08) and smooth decollement showed no slow earthquake activity. In contrast, high activity of slow earthquakes was observed in areas with a rough decollement due to the presence of subducted seamounts or bathymetric highs. The low taper angle (3.8°) off Muroto where slow earthquakes also occur translates to a wide zone of low μb (0.21 ± 0.06) and high λ* (0.66 ± 0.06). However, our results also show that slow earthquakes don't always occur in areas with high λ*. Plain Language Summary: Slow earthquakes such as very low frequency earthquakes and tremors are different than typical earthquakes because they occur longer and can last for more than several days. They have been reported in numerous subduction zones around the world and the study of slow earthquakes has recently gained attention because they have been suggested as precursors to larger earthquakes albeit on rare occasions. Slow earthquakes show a clustered distribution in the Nankai Trough. We used a dense network of seismic reflection data acquired at the shallow portion of the Nankai Trough to examine why some areas have high activity and some areas have no activity. Our results showed that areas with no slow earthquake activity have a smooth decollement and low pore fluid pressure. On the other hand, areas with high slow earthquake activity have a rough decollement. The occurrence of slow earthquakes has been typically associated with high pore fluid pressure because it allows the two slabs of rock to slide easier. However, our results suggest that high pore fluid pressure may not always be a prerequisite for slow earthquakes to occur. Key Points: A smooth decollement due to absence of subducted seamounts or bathymetric highs, and low pore fluid pressure results in a slow earthquake gapSlow earthquakes don't always occur in areas of high pore pressure but in combination with other variables like decollement roughnessThe low taper angle off Muroto indicates a wide zone of low friction and high pore pressure possibly associated with subducted seamounts [ABSTRACT FROM AUTHOR]

Clay‐rich rocks are integral to subduction zone dynamics and of practical importance, for example, as barriers in nuclear waste and CO2 repositories. While the effects of swelling strain on the self‐sealing capabilities of these rocks are relatively well‐established, the implications of polar fluids interacting with charged clay particles on the frictional behavior, and the role of swelling stress in initiating slip in critically stressed faults, remain ambiguous. To address these uncertainties, we conducted triaxial friction experiments using saw‐cut samples, with the upper half composed of Opalinus claystone (OPA) and the lower half of Berea sandstone (BER). The frictional strength of the non‐wetted OPA‐BER interface was estimated based on experiments at confining pressures of 4–25 MPa and constant axial loading rate (0.1 mm/min). Fluid injection friction experiments were performed using decane (non‐polar fluid) or deionized water (polar fluid) at 10 and 25 MPa confining pressures and constant piston displacement control. Macroscopic mechanical data were complemented by distributed strain sensing on the sample surface. Compared to decane, the frictional strength of the OPA‐BER interface tended to decrease when injecting water, which is attributed to phyllosilicate lubrication and the transition of the OPA from a solid rock to an incohesive mud near the saw‐cut surface. When injecting water, slip was initiated during initial hydration of the OPA‐BER interface, although the apparent stress state was below the yield stress. To explain this behavior, we propose that the swelling stress is a crucial factor that should be integrated into the effective stress model. Plain Language Summary: Clay‐rich rocks are important in subduction zones and for practical applications like nuclear waste containment and CO2 storage. A unique property of clay is the ability to swell by incorporation of water. If swelling deformation is constrained, swelling stress can develop. While the enhanced sealing ability of fractures due to swelling is well‐known, the effect of water‐clay interactions on friction and the contribution of swelling stress to fault reactivation remain unclear. We studied these effects with laboratory experiments where Opalinus claystone (OPA) was sheared against Berea sandstone. First, using experiments without fluids, we established that our set‐up is representative for claystones. In further experiments, we injected a non‐polar fluid that does not interact with clay. We compared these with experiments where we injected water, which is polar and therefore interacts with the charged clay. The frictional strength tended to decrease when injecting water, likely due to water acting as a lubricant and transforming OPA into a slurry. Surprisingly, movement along the interface started although the applied stress was below the threshold. We explain this by the contribution of swelling stress to the overall stress state. These findings improve our understanding of clay‐rich rock behavior in nature and practical applications. Key Points: The frictional strength of clay‐rich rocks tends to decrease in the presence of a polar fluid compared to a non‐polar fluid or no fluidFrictional slip in clay‐rich rocks may be initiated although the apparent effective stress state is below the yield stressH2O‐clay interactions may contribute to reactivation of faults by altering the mechanical properties and the build‐up of swelling stresses [ABSTRACT FROM AUTHOR]

The seismic sliding of rock masses is an important phenomenon that is widely involved in earthquake geological hazards. Practical seismic sliding is a three‐dimensional problem, namely, the seismic loads may act in any direction and the rock masses may move in an arbitrary direction relative to the sliding plane. In the present work, the functions of two different seismic loading methods, that is, loading as body force time histories to the sliders or as displacement time histories to the base, are added to the program of the three‐dimensional discontinuous deformation analysis (3D‐DDA) method that is based on the contact theory to study the seismic sliding of rock blocks. The theoretical solutions of single‐block sliding on an incline under the two seismic loading methods are derived. By comparing the 3D‐DDA results of single‐block seismic sliding with the corresponding theoretical results, and comparing the 3D‐DDA results of seismic sliding of three‐stacked‐blocks under the two seismic loading methods, the correctness of 3D‐DDA for seismic sliding simulations is validated. Thereafter, the influence of three‐dimensional seismic components on single‐block sliding, and the movement of block groups under different seismic load conditions are investigated by 3D‐DDA simulations, which indicate the importance to consider rock mass seismic sliding as a three‐dimensional problem and the capability of 3D‐DDA for its analysis. This work builds a meaningful basis for the further numerical simulation study on the earthquake‐induced rock mass movements by 3D‐DDA. [ABSTRACT FROM AUTHOR]

Rockfall and rock avalanches are common in steep terrain on Earth and potentially on other planetary bodies such as the Moon and Mars. Since impacting rocks can damage exposed bedrock as they roll and bounce downhill, rockfall might be an important erosive agent in steep landscapes, even in the absence of water. We developed a new theory for rockfall‐driven bedrock abrasion using the ballistic trajectories of rocks transported under gravity. We calibrated this theory using laboratory experiments of rockfall over an inclined bedrock simulant. Both the experiments and the model demonstrate that bedrock hillslopes can be abraded by dry rockfall, even at gradients below the angle of repose, depending on the bedrock roughness. Feedback between abrasion and topographic steering of rockfall can produce channel‐like forms, such as bedrock chutes, in the absence of water. Particle size has a dominant influence on abrasion rates and runout distances, while the hillslope angle has a comparatively minor influence. Rockfall transport is sensitive to bedrock roughness; terrain with high friction angles can trap rocks creating patches of rock cover that affect subsequent rockfall pathways. Our results suggest that dry rockfall can play an important role in eroding and channelizing steep, rocky terrain on Earth and other planets, such as crater degradation on the Moon and Mars. Plain Language Summary: Rockfall is common on Earth and other planets. Falling rocks bounce down rocky slopes and likely also erode them. However, it has not been explored how erosive this process is, nor what landforms it might generate. We developed a numerical model for this erosion process and calibrated it with experiments of dry grains hopping down an inclined erodible surface. Both experiments and modeling showed that bedrock erosion from rockfall can occur even on relatively low‐grade hills. Small hollows were carved by rockfall, which over time coalesced into larger troughs that captured the path of subsequent rocks. This process led to a self‐enhancing feedback that produced a bumpy surface with rocky chutes. Rock size had a larger effect on erosion amounts than the steepness of the hill. Our work suggests that dry rockfall can play an important role in the evolution of mountain slopes on Earth and craters on the Moon and other planets. Key Points: Rockfall can erode rocky hillslopes even below the angle of reposeGrain size has a dominant effect on impact abrasion; slope is of minor importanceTopographic steering of grain results in self‐formed bedrock channels [ABSTRACT FROM AUTHOR]

This paper present results of shaking‐table tests conducted in 2015 and 2018 on a free‐standing base sliding and rocking system, which allows sliding and uplifting. A full‐scale 10‐story reinforced concrete (RC) building equipped with cast iron plates on the bottom surface of the grade beams was used as a specimen for 2015 and 2018 experiments. In 2018, the static friction coefficients of the specimen were 0.48 and 0.49, which was higher than that of the rustproofed specimens in 2015. In the experiments of 2015 and 2018, the normalized base shear (NBS) values when the sliding length of the building reached ≥1 mm were 0.0035–0.1795 and 0.1744–0.2748, respectively. In the shaking‐table test corresponding to moderate earthquake motions, the 2018 specimen showed almost no lateral movement, whereas the 2015 specimen moved laterally. Therefore, more seismic energy was input into the specimen, and the maximum interstory drift ratio of the 2018 specimen was larger than that of the 2015 specimen. However, when the 50% amplitude excitation results of the 2015 seismic structural system are compared with those of the 2018 free‐standing structural system, the 2018 results are approximately 0.57 times smaller. Thus, a free‐standing structural system with cast iron plates to reduce earthquake energy could reduce damage to buildings. The 2018 specimen satisfies the concept of a free‐standing base sliding and rocking system that does not move laterally during small to moderate earthquake motions but moves laterally during strong earthquake motions to suppress structural damage. [ABSTRACT FROM AUTHOR]

This paper focuses on the seismic analysis and performance assessment of the self‐centering moment‐resisting frames with sliding rocking beams (SCMRF‐SRB) through a nonlinear numerical simulation study. In the SCMRF‐SRB systems, the beam is comprised of three segments with the rocking beam placed in the middle segment. The beam growth (expansion) problem due to the gap‐opening in the rocking joint is counteracted by the sliding movement of the rocking beam inside the beam brackets. The restoring force of such SCMRF‐SRBs is generated by two sets of preloaded disc springs mounted on each side of the web of the beam and the energy dissipation is provided by replaceable hysteretic dampers (RHD). The relative movement of the rocking beam inside the brackets generates a friction force that contributes to the energy dissipation capacity and strength of the system based on prior experimental observations. Load vs. displacement relationships of an SCMRF‐SRB modular structure were formulated and verified with nonlinear finite element analysis results. A three‐story building located in downtown Seattle was designed and its seismic performance was studied through nonlinear static and dynamic analyses. According to the results of the nonlinear dynamic analyses, the prototype structure met the expected performance criteria in terms of inter‐story drift ratio (IDR), re‐centering behavior, and responses of the frame member at design basis earthquake (DBE). In different parametric studies, the effect of the length and location of the rocking beam on the seismic performance of the prototype structure was investigated. Moreover, the effects of the energy dissipation capacity and post‐yielding stiffness on the structural responses of the prototype buildings were studied. It was also shown that an SCMRF‐SRB structure with a large energy dissipation ratio of up to 90% can be utilized without adversely affecting the self‐centering performance of the system. [ABSTRACT FROM AUTHOR]

The physical processes that facilitate long‐distance translation of large‐volume gravity slides remain poorly understood. To better understand these processes and the controls on runout distance, we conducted an outcrop and microstructural characterization of the Sevier gravity slide across the former land surface and summarize findings of four key sites. The Sevier gravity slide is the oldest of three mega‐scale (>1,000 km2) collapse events of the Marysvale volcanic field (Utah, USA). Field observations of intense deformation, clastic dikes, pseudotachylyte, and consistency of kinematic indicators support the interpretation of rapid emplacement during a single event. Furthermore, clastic dikes and characteristics of the slip zone suggest emplacement involved mobilization and pressurized injection of basal material. Across the runout distance, we observe evidence for progressive slip delocalization along the slide base. This manifests as centimeter‐ to decimeter‐thick cataclastic basal zones and abundant clastic dikes in the north and tens of meters thick basal zones characterized by widespread deformation of both slide blocks and underlying rock near the southern distal end of the gravity slide. Superimposed on this transition are variations in basal zone characteristics and slide geometry arising from interactions between slide blocks during dynamic wear and deposition processes and pre‐existing topography of the former land surface. These observations are synthesized into a conceptual model in which the presence of highly pressurized fluids reduced the frictional resistance to sliding during the emplacement of the Sevier gravity slide, and basal zone evolution controlled the effectiveness of dynamic weakening mechanisms across the former land surface. Plain Language Summary: Large‐volume volcanic landslides pose a low‐frequency but high‐impact natural hazard due to both their massive size and long‐runout distances that exceed predictions grounded in simple sliding models. Studying the deposits of past long‐runout landslides provides insight into the physical processes that reduce friction and aid movement of slide material for long distances over the land surface. We describe the deformation styles observed in the basal zone of the gigantic Sevier gravity slide of southwestern Utah to build a conceptual model for the physical processes associated with the slide's emplacement. Field observations indicate high fluid pressures beneath the slide promoted high‐velocity sliding. During slip, mechanical breakdown of rocks exposed at the slide plane and deposition of wear products allowed pressurized fluids to escape the basal zone and resulted in deceleration of the slide. Key Points: Field observations at the long‐runout Sevier gravity slide indicate high‐velocity emplacement aided by supralithostatic fluid pressuresSlip localization and low‐permeability volcanic rocks promote effective dynamic weakening mechanisms early in translation historyIncreasing damage, permeability, and slip delocalization result in deceleration and cessation of the Sevier gravity slide [ABSTRACT FROM AUTHOR]

We propose a numerical model of laboratory earthquake cycle inspired by a set of experiments performed on a triaxial apparatus on sawcut Carrara marble samples. The model couples two representations of rock matter: rock is essentially represented as an elastic continuum, except in the vicinity of the sliding interface, where a discrete representation is employed. This allows to simulate in a single framework the storage and release of strain energy in the bulk of the sample and in the loading system, the damage of rock due to sliding, and the progressive production of a granular gouge layer in the interface. After independent calibration, we find that the tribosystem spontaneously evolves toward a stick‐slip sliding regime, mimicking in a satisfactory way the behavior observed in the lab. The model offers insights on complex phenomena which are out of reach in experiments. This includes the variability in space and time of the fields of stress and effective friction along the fault, the progressive thickening of the damaged region of rock around the interface, and the build‐up of a granular layer of gouge accommodating shear. We present in detail several typical sliding events, we illustrate the fault heterogeneity, and we analyze quantitatively the damage rate in the numerical samples. Some limitations of the model are pointed out, as well as ideas of future improvements, and several research directions are proposed in order to further explore the large numerical data set produced by these simulations. Plain Language Summary: Earthquakes are due to sudden sliding in faults several kilometers in the ground. A common laboratory practice is to reproduce such sliding events on dedicated lab devices. In this work, we present a novel numerical model aiming to reproduce such experiment in a computer simulation, in order to enhance our understanding of the phenomena at stake. This model is novel because it couples two different representations of the rock matter, namely a continuous and a discrete one. It therefore allows to reproduce in the same framework the bulk deformation of rock and the granular phenomena occurring at the sliding interface. The model is calibrated and leads to the spontaneous occurrence of unstable sliding, that is, of earthquakes of the same kind as those observed in the lab. We further explore into more detail some typical sliding events, and focus our attention of the interface damaging and wear during sliding. This work is likely to clarify our interpretations of sliding events in the lab. Key Points: A coupled Discrete‐Continuum model of a laboratory earthquakes experiment leads to the spontaneous development of numerous seismic cyclesThe stress fields on the fault are found to be very heterogeneous. Typical events of various sizes are analyzed in detailsDamage and wear of the interface are quantified during sliding, and their rates are found to follow different laws [ABSTRACT FROM AUTHOR]

The formation of frictional melt likely impacts the coseismic and, when solidified (pseudotachylyte), the interseismic strength of faults. Here we investigate these effects through experiments using a new energy‐controlled rotary shear machine (ECoR) on simulated faults made of a transparent rock analog material (polymethyl‐methacrylate). As in nature, ECoR allows (a) elastic strain energy to accumulate at different loading rates and (b) the spontaneous nucleation of slip events. ECoR is equipped with a high‐speed camera, thermocouples, and transducers to monitor the surface, temperature, and acoustic emissions (AEs), respectively. We perform experiments at normal stresses of ∼3.5 MPa across loading rates from 0.15 MPa/s, phase A, to 2.5 MPa/s, phases B‐C‐D. In phase A, the temperature remains constant, and slip events occur without visible melting every 3.3–6.4 s with 0.5–0.7 MPa stress drops and 3–7 mm displacements. In phases B‐C, slip events occur in the presence of melts every 0.5–0.9 s, and the bulk temperature increases progressively. Melt solidification increases static friction yielding slip events with stress drops up to 5 MPa and displacements up to 3 cm. Samples produce high‐frequency AEs during slip acceleration and deceleration. Once the bulk temperature reaches ∼110°C, a "final" and silent long displacement event occurs in the presence of melts (phase D). Experimental observations suggest that melt formation modulates the coseismic (flash melting, melt lubrication, and viscous braking) and interseismic (welding) stages. Furthermore, AEs associated with coseismic fault weakening and strengthening may have their natural equivalent and could be observed in seismograms through near‐fault instrumentation. Plain Language Summary: During earthquakes, rocks slide against each other result in frictional heat. In some cases, enough heat is generated that rocks melt, influencing earthquake behavior. We investigate this behavior with experiments using a newly devised laboratory apparatus on a rock‐analog material, polymethyl‐methacrylate glass (commercial name, Plexiglas®). The apparatus reproduces the natural earthquake cycle by compressing two cylinders (top and bottom sample) in the vertical direction, then gradually loads a spring, applying a horizontal shear force where the two samples meet. Slip between the samples occurs when the force from the spring overcomes the ability of the material to resist shearing. This process mimics earthquakes along faults at depth, generating heat and melts. We find that during slip, such melts initially lubricate the fault, then cool, thicken, and increase viscosity to resist slip. Moreover, the solidification of melts increases the fault strength leading to larger successive earthquakes. We used acoustic sensors to monitor the sound and vibrational waves emitted from slip events. These recordings reveal the occurrence and timing of the processes happening during faulting. As monitoring technology improves, the waves' characteristic of these processes may also become evident in seismograms of natural earthquakes and help us understand how earthquakes work. Key Points: We use a newly conceived experimental machine on polymethyl methacrylate to investigate the seismic cycle in the presence of meltsEnergy flux pulses from the machine to the fault yield fault weakening (flash melting + lubrication) and strengthening (viscous braking)Distinct acoustic emission signals correlate with the activation of coseismic fault weakening/strengthening mechanisms [ABSTRACT FROM AUTHOR]

Mass movement deposit grain‐size distributions (GSDs) record initiation, transport and deposition mechanisms, and contribute to the rate at which sediment is exported from hillslopes to channels. Defining the GSD of a mass movement deposit is a significant challenge because they are often difficult to access, are heterogeneous in planform and with depth, contain grain sizes from clay (<63 μm) to boulders (>1 m), and require considerable time to calculate accurately. There are numerous methods used to measure mass movement GSDs, but no single method alone can measure the entire range of grain sizes. This paper compares five common methods for determining mass movement deposit GSDs to assess how their accuracy may affect their applicability to different research areas. We applied an automated wavelet analysis (pyDGS), Wolman pebble counts, survey tape counts, manual photo counts and sieving to three different mass movement deposits (two debris flows, one rockslide) in Tredegar, Wales and the Longmen Shan, China. We found that pyDGS and survey tape counts produced comparable GSDs to sieving over a single order of magnitude. PyDGS required calibration to achieve accurate results, limiting its use for many applications. In Tredegar, Wolman pebble counts over‐estimated grain sizes in the lower 80% of the distribution relative to the other four methods used. We demonstrate that method choice can introduce significant uncertainties, particularly at the edges of the distributions, such that D16 values differ by up to a factor of five. These methodological uncertainties limit GSD comparisons across studies, particularly where these are used to infer processes within deposits. To minimize these challenges, the methods chosen should be both carefully reported and consistent with the research question. [ABSTRACT FROM AUTHOR]

Temporal fault‐zone observations are important to better understand the evolution of fault structure and stress configuration. However, long‐term monitoring in the fault zone is rare after a large earthquake. Here, we use seismic data in the fault zone at 1‐km depth from the Taiwan Chelungpu‐fault Drilling Project to study long‐term anisotropy after the 1999 Mw7.6 Chi‐Chi earthquake. The direct S‐wave splitting measurements resolve the overall weak anisotropy in the shallow crust. In order to resolve fault damage zone anisotropy, we perform coda cross‐correlation technique for 794 microearthquakes between 2007 and 2013. We estimate the temporal change in background shear‐wave velocity, fast shear‐wave polarization direction (FSP), and strength of anisotropy (Aani) in the fault damage zone. We show the average FSP direction is N93°E with a significant Aani of about 12%, likely due to the pervasive vertical microcracks created after the earthquake. Temporal variations of anisotropy exhibit seasonal variation with periodicity every 9–12 months that correlates with rainfall events. Furthermore, long‐term anisotropy shows a gradual rotation of FSP direction of about 15° during the first 4 years of observation. At the same time, the strength of anisotropy reduced from 17% to 10% and shear‐wave velocity increased, suggesting the fault healed after the earthquake. This study reports in‐situ evidence for two key observations: (a) long‐term, fault‐zone healing after a major earthquake and (b) modulation of 1‐km deep fault‐zone properties by surficial hydrologic processes. These observations may provide constraints on the response of the fault damage zone in the interseismic period. Plain Language Summary: Earthquakes are generated when rocks slip quickly along a fault. Damage produced by fault rupture is often observed in an area with enhanced fracture networks called the fault damage zone. Fractures inside the damage zone can open or close in response to the background stress. Therefore, observing fault fractures may provide useful information on how the background stresses evolve in the fault. Here, we observe the time‐dependent change of fractures in the fault damage zone through seismic anisotropy analysis. We measure the velocity difference of a seismic shear‐wave in different azimuths to determine the anisotropy. The azimuth of the fastest shear‐wave indicates the dominant fracture orientation inside the fault damage zone. We use borehole seismometers installed within the Chelungpu fault in Taiwan to study the long‐term anisotropy after a major earthquake, and found the fault‐zone is highly damaged with fractures aligning with the tectonic stress direction. Anisotropy varies seasonally due to fluid pressure changes in fault zone fractures during and after rainfall events. In addition, we observe a long‐term anisotropy change that might indicate fracture closure. This study presents a unique observational dataset which allows us to better understand fault zone evolution after a large earthquake. Key Points: A 7‐year (2007–2013) fault‐zone seismic anisotropy is presented from the Taiwan Chelungpu‐fault Drilling Project borehole seismic arrayAverage fast shear‐wave direction of N93°E and anisotropy strength of 12% are observed after the Chi‐Chi earthquakeAnisotropy varies seasonally with rainfalls. Long‐term anisotropy from 17% to 10% with increasing velocity suggests fault healing [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear numerical simulation study of the D‐type self‐centering eccentric braced frame system with a sliding rocking link beam (SCEBF‐SRL) to overcome the beam‐growth problem. The re‐centering capability of such SCEBF‐SRLs is enabled by post‐tensioned (PT) steel‐stranded cables. Replaceable hysteretic dampers termed RHD are used as seismic fuse devices for energy dissipation, while the friction force due to the relative movement of the sliding rocking link beam inside the column corbels would also contribute to the energy dissipation capacity of the system. Analytical load versus displacement relationships of an SCEBF‐SRL module frame were formulated and cross‐validated with nonlinear finite element (FE) analysis results. The seismic performance of the proposed system was studied through nonlinear static and dynamic analysis of three‐ and six‐story prototype SCEBF‐SRL buildings. A set of twenty‐two far‐field ground motions from the FEMA P695 database was adopted for nonlinear dynamic analysis (NDA). NDA results revealed that the ensemble median of the maximum inter‐story drift ratios (IDRs) of both SCEBF‐SRL prototypes were less than 1.4% and 2.0% at the design basis earthquake (DBE) and the risk‐targeted maximum considered earthquake (MCER) levels, respectively. Additionally, both SCEBF‐SRL buildings fully re‐centered themselves at MCER with negligibly small residual drift (<0.01%). The parametric study results suggest that with an energy dissipation ratio, βE$\hspace*{0.28em}{\beta}_{E}$ between 25% and 60% and a minimum stiffness ratio of 5%, the ensemble median of the maximum IDR of the considered prototype building could be made less than 1.5% and 2.3% at DBE and MCER levels, respectively. [ABSTRACT FROM AUTHOR]

It has been proposed that most cirques are source‐area depressions of large, deep‐seated rock‐slope failures. Yet the close relation between cirques and climate is convincing evidence of the dominance of glacial erosion, rather than rock‐slope failure, in mountain cirque development and distribution. Cirque floor altitudes have a lower limit that varies with snowfall by 1000 m or more between windward and leeward sides of mountain systems. Glaciation levels and equilibrium line altitudes implied by cirques vary in parallel with those for modern glaciers. Cirques are often found mainly on the poleward or leeward slopes of individual mountain ranges, as are modern small glaciers (because of solar radiation and wind effects on ablation and accumulation). Most rock‐slope failures (RSFs: rock slides, rock avalanches and gravitational deformations) do not involve the deep‐seated rotational movement that would produce a cirque form. Although some deep‐seated RSFs with arcuate head scars may be confused with cirques, identification as a glacial cirque is more confident as the floor is longer, wider and more gently sloping. Some scars from major RSFs may resemble poor or moderately developed cirques, but tend to have steeper floors, to be more scattered and closely related to geology, whereas glacial cirques develop on all rock types. Deep‐seated RSFs high on slopes can be associated with seismic shaking, but cirques develop without relation to seismicity. Degree of cirque development can be related to duration of exposure to glaciation. Often RSFs are found adjacent to cirques, or in glacial transfluences; only a proportion are well situated to develop into glacial cirques. Valley‐head cirques are continued down‐valley by glacial troughs. The 'overdeepening' (rock basins with reversed slopes) found in a large minority of cirques is not due to rock avalanching, fluvial or periglacial erosion. The RSF proposal should therefore be rejected in favour of the traditional glacial explanation, without any nivation stage being necessary. Rock‐slope failure is one of several possible ways of initiating hollows for glacier accumulation, as well as an ancillary process of cirque extension or widening through collapse of glacially oversteepened slopes. Headward extension of adjacent cirques on a ridge leads to displacement of the divide, sometimes by 2 km or more, lowering ridge and summit altitudes and producing the 'glacial buzzsaw' effect. Where a relatively lower snowline has led to cirque erosion on all sides of a mountain, cirque intersection lowers summits further. The buzzsaw hypothesis is not applicable, however, where remnants of a preglacial summit surface survive. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Costs for installation and maintenance of protective structures are increasing while alpine hazards progressively threaten alpine communities, infrastructure and economics. Thus, reliable process‐based anticipation and early warning strategies offer a cost‐effective and smart solution for alpine societies in the near future. However, only few comprehensive pre‐failure observations of alpine rock slopes have been reported so far. This paper demonstrates pre‐failure observations of a rapidly deforming rock mass (potentially 260,000 m3) at the Hochvogel (Allgäu Alps, 2,592 m a.s.l.) and a geotechnical monitoring and warning concept. This is implemented in the complementary multi‐method approach of the AlpSenseBench project and the basis for an effective and reliable early warning system. Since 2014, overall displacement rates in the range of 2 to 10 mm/month in the main decametre deep fracture are observed. It is expected that predictive acceleration patterns will appear in the final pre‐failure stage. A detailed knowledge of multiple anticipative signals in correlation with accelerating rock slope deformations will contribute to an advance in accuracy and reliability of rock slide early warning. [ABSTRACT FROM AUTHOR]

The Pāpaku Fault Zone, drilled at International Ocean Discovery Program (IODP) Site U1518, is an active splay fault in the frontal accretionary wedge of the Hikurangi Margin. In logging‐while‐drilling data, the 33‐m‐thick fault zone exhibits mixed modes of deformation associated with a trend of downward decreasing density, P‐wave velocity, and resistivity. Methane hydrate is observed from ~30 to 585 m below seafloor (mbsf), including within and surrounding the fault zone. Hydrate accumulations are vertically discontinuous and occur throughout the entire logged section at low to moderate saturation in silty and sandy centimeter‐thick layers. We argue that the hydrate distribution implies that the methane is not sourced from fluid flow along the fault but instead by local diffusion. This, combined with geophysical observations and geochemical measurements from Site U1518, suggests that the fault is not a focused migration pathway for deeply sourced fluids and that the near‐seafloor Pāpaku Fault Zone has little to no active fluid flow. Plain Language Summary: Faults are boundaries in the Earth where two different blocks of sediment or rock slide past each other. Offshore New Zealand, the Pāpaku Fault is very shallow and intersects the seafloor but connects to deeper faults kilometers below the seafloor where large earthquakes can occur. An ice‐like form of methane called hydrate also occurs within and surrounding the fault. We use scientific drilling data to understand the physical properties of the fault. Hydrate can affect fault properties and how fluid flows; however, based on the pattern of hydrate distribution and other geochemical and geophysical measurements, we suggest that the Pāpaku Fault does not have active fluid flow. Key Points: The Pāpaku Fault Zone is a 33‐m‐thick near‐seafloor splay fault drilled at Site U1518 on the Hikurangi MarginMultiple lines of observational, geophysical, and geochemical evidence suggest that there is little to no fluid flow along the Pāpaku Fault [ABSTRACT FROM AUTHOR]

Rockfalls and rockslides often occur in mountainous areas, and they may develop into rock avalanches because of fragmentation. A series of laboratory experiments were conducted to study the contributions of rock mass structure to the emplacement of fragmenting rockfalls and rockslides. In these experiments, we considered the process of breakable analog blocks with different structures sliding along an inclined plane, impacting at the kink point with a horizontal plane where deposition occurs. The results show that the initial geometrical subdivision (i.e., the rock mass structure) of the source rock can greatly influence the impact of the fragmentation process and total runout, while the degree of fragmentation controls the travel distance of the center of mass. The occurrence of transversal discontinuities enhances the momentum transfer efficiency from the rear to the front part of the rock mass. A negative correlation between the apparent friction coefficient (linked to the total runout) and equivalent friction coefficient (linked to the center of mass runout) was found, which appears to be induced by fragmentation. We proposed a new fragmentation‐spreading model to describe this negative correlation. This simple physical model supports the importance of fragmentation in rock fragment trajectories and the runout of rockfalls and rockslides. Fragmentation is an energy‐sinking process that will shorten the runout of the center of mass. Thus, we suggest that impact fragmentation does not fully account for the long runout of large rockfalls and rockslides. Key Points: Structural features influence the fragmentation and runout, while the degree of fragmentation influences the runout of the center of massA negative correlation between the total runout and the runout of the center of mass appears to be induced by fragmentationImpact fragmentation is an energy‐sinking process that will shorten the runout of the center of the sliding mass [ABSTRACT FROM AUTHOR]

Displacement rates of mountain slope deformations that can affect entire valley mountain flanks are often measured spatially distributed in‐situ without spatial significance. The spatially explicit measurement and recording of time series of slope deformations is a challenge, as the unstable slopes are often disintegrated into several subdomains, which move with different deformation rates. The current state‐of‐the‐art monitoring systems detect slow to very slow deformation rates between mm/a and several m/a. Using the examples of slope deformations in Saalbach‐Hinterglemm and the deep rock slide Marzellkamm in Austria this paper presents the results of terrestrial laser scans, extensometer measurements, Spaceborne InSAR data, unmanned Aerial System Photogrammetry (UAS‐P), and fixed‐point measurements. The different measurements complement each other and are optimally aligned for different application areas. InSAR data can help to identify hot spots on regional and local scale, while UAS‐P enables for spatially high level accuracy in the detection of subdomains moving at different speeds. For local warning systems TLS, extensometers and GBInSAR deliver higher accuracy. [ABSTRACT FROM AUTHOR]

Despite limited attention to geomorphic hazards in Saudi Arabia, the mountainous region in the south‐west portion of the Kingdom has experienced a series of devastating debris flows, landslides, rockfalls, and debris floods during the past several decades. While undisturbed hillslopes are relatively stable, many rock slides, rockfalls and landslides are associated with cut and fill slopes of mountain roads and other disturbances in this steep terrain. These human‐induced geomorphic hazards act synergistically to exacerbate downslope and downstream disasters, such as debris flows and debris floods. The progressive sediment loading in low‐gradient channels (wadis) together with large convective rainfall events, have caused episodic evacuation of these ephemeral channels. As such, hydrogeomorphic linkages between hillslope and channel mass wasting processes may be temporally separated as wadis accumulate sediment, posing challenges for prediction of the timing of damaging debris flows. Furthermore, there is little appreciation of the extent to which human‐related disturbances (e.g., mountain roads, construction sites, overgrazing) contribute to these downstream disasters or the vulnerability of passengers, residents, or herders to these anthropogenically induced hazards. Such knowledge and information is needed to develop effective hazard mitigation and real‐time warning systems for this and similar dry mountain regions that experience episodic storms. Here we demonstrate the need for improved road location, construction practices, and land management in this steep terrain as well as better appreciation of the hillslope and in‐channel hazard nexus to reduce downstream impacts of geomorphic disasters. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of a dramatic rock slope acceleration that occurred in fall 2016 at the Moosfluh Landslide, located at the glacier tongue of the Great Aletsch Glacier (Switzerland). The acceleration that occurred in 2016 was unanticipated and exposed the valley bottom and an adjacent damned lake to high risk. This acceleration occurred in an active deep‐seated gravitational slope deformation (DSGSD) controlled primarily by deep block‐flexural toppling. In 2013, a highly accurate displacement monitoring system was developed and installed in the surroundings of the Great Aletsch Glacier, including a time‐lapse camera, GNSS, and robotic total stations. This monitoring system provided unique data during the 2016 slope acceleration which are used in this study to assess failure mechanisms, landslide volumes, and subsurface displacement geometry. Based on a novel displacement vector analysis, we find that three retrogressive secondary rockslides developed during the first six weeks of the slope acceleration, with rupture surface depths of 30 to 40 m, and estimated volumes between 1 and 4 Mm3. These rockslides display complex deformation features, including head and lateral scarps, which developed during the slope acceleration. The kinematics of these secondary rockslides changed through time, from primarily toppling to combined toppling and sliding. Our results provide a uniquely detailed understanding of the spatial and temporal evolution of deformation features and movement kinematics that occur when several sectors of a slowly moving DSGSD transitions into rapid rockslides. Plain Language Summary: The slow moving (~30 cm per year) deep‐seated (up to 170‐m depth) landslide of Moosfluh experienced a substantial acceleration of slope movement in September 2016. A comprehensive monitoring system recorded that several compartments in the center of the Moosfluh Landslide suddenly started to move rapidly with velocities of up to several meters per week. This caused a strong modification of the slope surface morphology and structure which is documented in detail in this study. Based on monitored changes in the directions of slope movement over time, a new method was developed to interpret subsurface movement types and geometries. With this method we found that on top of the Moosfluh deep‐seated landslide several shallow (30–40 m) rockslides developed during the Moosfluh slope acceleration in 2016. We are able to assign depths and inclinations of the failure surfaces and failure mechanisms. In this case the deep‐seated landslide is formed by rotation (toppling) of steep rock columns, whereas the shallow secondary rockslides within the deep‐seated landslide show sliding movements along planar rupture planes and mixtures of both sliding and toppling. Key Points: The rapid formation of 3 secondary rockslides within a toppling mode DSGSD (Moosfluh, CH) is monitored with DIC from webcam images, aerial photogrammetry and total station monitoringThis transition corresponds to an acceleration of the landslide from a few dm/a to 50 m/a in the lowermost sectors of the instabilityA novel method developed to interpret total station reflector data revealed a change in landslide kinematics (toppling, sliding) through time [ABSTRACT FROM AUTHOR]

The identification of hazardous slopes with degrading permafrost is a key task in the mountain periglacial environment. If rockslides have previously been preconditioned by rock wall permafrost, similar events may be triggered from present unstable rock walls. An inventory of rockslides and rock avalanches in the austral part of the Santa Cruz river basin (31°40′–31°50′S, 70°30′–70°10'W), San Juan, Argentina, was made. The study area comprises a surface of approximately 432 km2 (50% above 3,500 m asl); 15 rockslides, 12 complex rockslides evolving to rock avalanches and 19 rock avalanches were identified. The deposits were analyzed with remote sensory imagery and during fieldwork in order to study processes under permafrost degradation caused by global warming. Rock sampling procedures and laboratory rock‐resistivity testing were also carried out. We characterized the detachment scars and deposits for two rockslides. Two different mechanisms were identified. In one rockslide, shallow active layer detachment was favored by shear‐displacement along pre‐existing joints, as a result of short‐term periods of climate warming. In the other, long‐term permafrost degradation favored a deeper failure process. The studied landslide processes could not be explained by permafrost degradation alone. Faults, the geometric arrangement of their structural elements and seismic activity may contribute to trigger these phenomena. It is expected that the magnitude and frequency of rockslide hazards will increase during the 21st century. [ABSTRACT FROM AUTHOR]

Landslides are among hazards that undermine the social, economic, and environmental well‐being of the vulnerable community. Assessment of landslides vulnerability reveals the damages that could be recorded, estimates the severity of the impact, and increases the preparedness, response, recovery, and mitigation as well. This study aims to estimate landslides vulnerability for the western province of Rwanda. Field survey and secondary data sources identified 96 landslides used to prepare a landslides inventory map. Ten factors—altitude, slope angles, normalized difference vegetation index (NVDI), land use, distance to roads, soil texture, rainfall, lithology, population density, and possession rate of communication tools—were analyzed. The Analytical Hierarchy Process (AHP) model was used to weight and rank the vulnerability conditioning factors. Then the Weighted Linear Combination (WLC) in geographic information system (GIS) spatially estimated landslides vulnerability over the study area. The results indicated the altitude (19.7%), slope angles (16.1%), soil texture (14.3%), lithology (13.5%), and rainfall (12.2%) as the major vulnerability conditioning parameters. The produced landslides vulnerability map is divided into 5 classes: very low, low, moderate, high and very high. The proposed method is validated by using the relative landslides density index (R‐index) method, which revealed that 35.4%, 25%, and 23.9% of past landslides are observed within moderate, high, and very high vulnerability zones, respectively. The consistency of validation indicates good performance of the methodology used and the vulnerability map prepared. The results can be used by policy makers to recognize hazard vulnerability lessening and future planning needs. Integr Environ Assess Manag 2019;00:000–000. © 2019 SETAC Key Points: Disaster vulnerability increases mainly due to lack of timely risk information sharing and integrated vulnerability assessment, which would enhance the risk awareness and preparedness.The Analytic Hierarchy Process weighted the vulnerability causal factors, then the geographic information system helped to spatially distribute the vulnerability within the study area.The findings contribute to future strategic planning and mitigation strategies toward disaster risk reduction and sustainable development. [ABSTRACT FROM AUTHOR]

We studied a data set of 28 well‐preserved lunar craters in the transitional (simple‐to‐complex) regime with the aim of investigating the underlying cause(s) for morphological differences of these craters in mare versus highland terrains. These transitional craters range from 15 to 42 km in diameter, demonstrating that the transition from simple to complex craters is not abrupt and occurs over a broad diameter range. We examined and measured the following crater attributes: depth (d), diameter (D), floor diameter (Df), rim height (h), and wall width (w), as well as the number and onset of terraces and rock slides. The number of terraces increases with increasing crater size and, in general, mare craters possess more terraces than highland craters of the same diameter. There are also clear differences in the d/D ratio of mare versus highland craters, with transitional craters in mare targets being noticeably shallower than similarly sized highland craters. We propose that layering in mare targets is a major driver for these differences. Layering provides pre‐existing planes of weakness that facilitate crater collapse, thus explaining the overall shallower depths of mare craters and the onset of crater collapse (i.e., the transition from simple to complex crater morphology) at smaller diameters as compared to highland craters. This suggests that layering and its interplay with target strength and porosity may play a more significant role than previously considered. [ABSTRACT FROM AUTHOR]

Abstract: To clarify the geological causes of rockslides induced by rainstorms in accretionary complexes, the geology and geomorphology of two large rockslides (volumes > 106 m3) induced by the heavy rainfall of Typhoon Talas in the Shimanto Belt, Kii Mountains, Japan in 2011 are investigated. Our analysis reveals that thrusts with brittle crush zones controlled the occurrence of the rockslides. The properties and distribution of thrusts were poorly constrained before this study. Flooding during the rainstorm removed surface materials along rivers, allowing thorough geological mapping to be performed. Gravitationally deformed slopes were studied using GIS analysis of 1 m digital elevation models (DEMs) and fieldwork, and X‐ray diffraction (XRD) analysis, permeability, and direct shear tests were used to characterize the mineralogy and geotechnical properties of fault gouge. The Kawarabi thrust has a brittle crush zone up to 6 m thick and acts as the sliding surface for both landslides. The thrust dips 34° downslope and is cut by high‐angle faults and joints along one or both sides of each landslide body. Prior to failure, the upper part of the slope contained small scarps, suggesting that the slopes were already gravitationally deformed. The slope instability can be attributed to long‐term river erosion, which has undercut the slope and exposed the thrust at the base of the slope. The groundwater level, monitored in boreholes, suggests that the Kawarabi thrust is a barrier to groundwater flow. The weak and impermeable nature of the thrust played an essential role in the generation of gravitational slope deformation and catastrophic failure during periods of increased rainfall. Thrusts are a common feature of accretionary complexes, including in the Shimanto Belt, and the mechanism of slope failure stated above can be typical of rockslides in accretionary complexes and provide new insights into landslide disaster mitigation. [ABSTRACT FROM AUTHOR]

Abstract: The volumes, rates and grain size distributions of sediment supplied from hillslopes represent the initial input of sediment delivered from upland areas and propagated through sediment routing systems. Moreover, hillslope sediment supply has a significant impact on landscape response time to tectonic and climatic perturbations. However, there are very few detailed field studies characterizing hillslope sediment supply as a function of lithology and delivery process. Here, we present new empirical data from tectonically‐active areas in southern Italy that quantifies how lithology and rock strength control the landslide fluxes and grain size distributions supplied from hillslopes. Landslides are the major source of hillslope sediment supply in this area, and our inventory of ~2800 landslides reveals that landslide sediment flux is dominated by small, shallow landslides. We find that lithology and rock strength modulate the abundance of steep slopes and landslides, and the distribution of landslide sizes. Outcrop‐scale rock strength also controls the grain sizes supplied by bedrock weathering, and influences the degree of coarsening of landslide supply with respect to weathering supply. Finally, we show that hillslope sediment supply largely determines the grain sizes of fluvial export, from catchments and that catchments with greater long‐term landslide rates deliver coarser material. Therefore, our results demonstrate a dual control of lithology on hillslope sediment supply, by modulating both the sediment fluxes from landslides and the grain sizes supplied by hillslopes to the fluvial system. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Österreichische Raumordnungskonferenz (ÖROK) set up a partnership in 2011 to deal with 'Risk management for gravitational natural hazards in landuse planning'. As gravitational natural hazards have a decisive influence on development in the Alpine Region, standard procedures were developed for the assessment of the relevance of these processes for landuse planning. This paper describes the recommended procedure for the assessment of hazards affecting permanent settlements from rockfall in a top-down approach. The first step to define potential conflicts between the maximum run-out of rockfall processes and the presence of settlements is a conservative empirical assessment based on rock outcrops serving as potential detachment zones and the maximum reach of such rockfalls, leading to a hazard indication map. This approach is only based on existing cartographic information, field investigations are not necessarily involved at this stage. To ensure conservative results, the use of a high-resolution 1 m ground model to identify rock outcrops is re commended. The next step includes a thorough examination of those areas in the hazard indication map with conflicts between the maximum reach/run-out of falling blocks and settlements. This stage includes field investigations with mapping of maximum reach blocks, block size distributions, underground conditions of the transit zone and the condition of rock outcrops that act as potential detachment zones. All this information is subsequently integrated into a 3D rockfall simulation. As a result the modelling enables a delineation of areas out of reach (no rockfall hazard), areas with potential impact energies ≤ 100 kJ (low intensity) and areas with potential impact energies > 100 kJ (high intensity). [ABSTRACT FROM AUTHOR]

In the valley of Navis, the village of Kerschbaum with 84 houses stands on a slowly downhill moving, relatively corase grained, aqua bearing earth-flow/-slide about 40 m thick. This secondary movement overlies a deep-seated rock slide. The rates of movement at the surface of the earth-flow/-slide were between 1 und 3 cm/a before the implementation of remedial works. Starting from the geotechnical and geomechanical model of the slope, measures were developed, which were intended to reduce the movement. A monitoring system was installed to provide information about the movement and slope water conditions of the earth-flow/-slide and the sliding rock mass. In order to estimate the creep behaviour of the earth-flow/-slide, the ductility index ILZR was determined from shear tests. A simple flow law was assumed for the estimation of the change of creep rate. Measurements over a period of about 18 months after the first phase of remedial works show rates between 0.5 and 1.2 cm/a. The reduction of the rate of movement is compared with the creep model applied and the viscosity index ILZR to check the validity. [ABSTRACT FROM AUTHOR]

In spring 2008 a rock slide detached from one of the walls in the quarry 'Frauenmühle' locally used as climbing park, mobilizing a volume of 50 m3. The binary granite is relative fresh on the bottom of the walls, but the weathering increases significantly to the natural surface. The bedrock shows an orthogonal joint system enabling the so-called 'Wollsackverwitterung'. Mapping of the joints followed by a kinematic analysis of the quarry wall by DIPS (Rocscience) indicates the slope failure to be of a planar sliding type on a medium-steep dipping plane. As the contributing factor for the slide, weathering along the plane has to be considered. Thereby the destruction of rock bridges downgrades the overall shear strength. A stability analysis based on the reconstructed block geometry and the determined shear parameters verifies the instability of the block. For today's situation, the kinematic analysis detects some critical intersections of joints being able to generate slide wedges. [ABSTRACT FROM AUTHOR]

In the former quarry near Spitz many rockslides have occurred during operation as well as after closure. They endangered a railway, the Wachau-bicycle route, an important road and the left Danube river bank. Therefore, a protection embankment and a rock fall fence were constructed as well as a monitoring system installed automatically closing all traffic routes, when rock face displacements are exceeding a threshold. In order to clarify the need for risk reduction measures, the hazard caused by the former quarry near Spitz was investigated by - Analyses of weather - and of occurrences statistics (when did rock slides occur for which reasons?) in order to assess the probability of future rock slides, - Geomechanical analyses of occurred and of possible future rock detachments and - Analyses of existing deposits and simulations of possible future rock slides in order to estimate the damage caused by these slides. The results of these investigations and the subsequent conclusions are described. Im ehemaligen Tagebau Spitz a. d. Donau ereigneten sich in der Vergangenheit sowohl während des Abbaus als auch nach dessen Stilllegung zahlreiche Felsstürze. Diese bedrohten die Wachau-Bahn, den Wachau-Radweg, die Wachau-Bundesstraße und das linksseitige Donauufer. Deshalb wurden ein Schutzdamm geschüttet, ein Steinschlagschutzzaun errichtet und ein Monitoring-Programm installiert, das bei Gefahr (bei größeren Verschiebungen) automatisch eine Sperre der Verkehrswege auslöst. Um die Notwendigkeit weiterer Maßnahmen zur Reduktion des Risikos abzuklären, wurde die vom ehemaligen Tagebau Spitz a. d. Donau ausgehende Gefahr analysiert. Dies geschah in Form von - Analysen der Wetter- und Ereignisstatistiken (wann ereigneten sich warum Felsstürze), um die Wahrscheinlichkeit weiterer Felsstürze abzuschätzen, - Geomechanischen Analysen früherer Ablösungen sowie Analysen möglicher zukünftiger Ablösungen und - Analysen früherer Ablagerungen und Simulationen möglicher zukünftiger Absturzszenarien, um den durch diese Szenarien verursachten Schaden abzuschätzen. Die Ergebnisse dieser Untersuchungen und die Schlussfolgerungen daraus werden beschrieben. [ABSTRACT FROM AUTHOR]

Forests can decrease the risk of shallow landslides by mechanically reinforcing the soil and positively influencing its water balance. However, little is known about the effect of different forest structures on slope stability. In the study area in St Antönien, Switzerland, we applied statistical prediction models and a physically-based model for spatial distribution of root reinforcement in order to quantify the influence of forest structure on slope stability. We designed a generalized linear regression model and a random forest model including variables describing forest structure along with terrain parameters for a set of landslide and control points facing similar slope angle and tree coverage. The root distribution measured at regular distances from seven trees in the same study area was used to calibrate a root distribution model. The root reinforcement was calculated as a function of tree dimension and distance from tree with the root bundle model (RBMw). Based on the modelled values of root reinforcement, we introduced a proxy-variable for root reinforcement of the nearest tree using a gamma distribution. The results of the statistical analysis show that variables related to forest structure significantly influence landslide susceptibility along with terrain parameters. Significant effects were found for gap length, the distance to the nearest trees and the proxy-variable for root reinforcement of the nearest tree. Gaps longer than 20 m critically increased the susceptibility to landslides. Root reinforcement decreased with increasing distance from trees and is smaller in landslide plots compared to control plots. Furthermore, the influence of forest structure strongly depends on geomorphological and hydrological conditions. Our results enhance the quantitative knowledge about the influence of forest structure on root reinforcement and landslide susceptibility and support existing management recommendations for protection against gravitational natural hazards. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Large, rapid rockslope failures generate deposits with complex morphologies due to a number of causal and influencing factors. To investigate these, we conducted a detailed case study at the carbonate Tschirgant deposit (Tyrol, Austria). It preserved evidence of simultaneous rock sliding (very large, coherent hummocks) and rock avalanche spreading (smaller, more scattered hummocks and ridges). Motion indicators, such as longitudinal ridges furthermore pinpoint the transition between linear sliding and radial spreading. The lithological distribution in the Tschirgant deposit shows that it retained source stratigraphy despite being split into two accumulation lobes by a high bedrock ridge. Furthermore, lithology had a very strong control on the final deposit morphology in that the different lithologic units form individual deposit surfaces. River erosion has created fortuitous outcrops that reveal the basal rock avalanche contact. The underlying valley-fill sediments (substrates) have been intricately involved in shaping the rock avalanche morphology and, where entrained, highlight internal rock avalanche deformation features. This study shows that intrinsic dynamic properties of granular media (e.g. tendency for longitudinal alignments), emplacement mode, lithology (and source predisposition), runout path topography, and substrates form the quintet of causal factors that shape rock avalanche morphology. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]