Landslide Initiation Research Articles

Seismic precursors to a 2017 Nuugaatsiaq, Greenland, earthquake–landslide–tsunami event

High-frequency (5–20 Hz) seismic signals precursory to and embedded within the June 17, 2017 ML = 4 earthquake–landslide event are analyzed. This event in western Greenland generated a tsunami in Karrat fjord inundating Nuugaatsiaq village 32 km distant. Spectrogram and wavelet analyses of seismic data from the Greenland Ice Sheet Monitoring Network (GLISN) corroborate observations of seismic precursors at Nuugaatsiaq reported by Poli (Geophys Res Lett 44:8832–8836, 2017) and Caplan-Auerbach (in: AGU fall meeting abstracts, 2017) and reveal additional high-frequency arrivals being generated after the apparent initiation of fault rupture. New observations of seismic precursors 181 km from the Event at Upernavik, Greenland are correlated with those seen at Nuugaatsiaq. Wavelet analysis presents > 100 significant energy peaks accelerating up to and into the earthquake–landslide event. The precursor events show a distinct, power law distribution, characterized by b values of ~ 2.4. Results are compared and contrasted with small precursors observed in the studies of a natural chalk cliff landslide at Mesnil-Val, Haute Normandie, France. The earthquake–landslide appears to have been initiated by seismic precursors located at the fault scarp, leading to a small seismic foreshock and small landslide initiation, followed by a larger earthquake at the fault scarp, precipitating the primary landslide into the Karrat Fjord, which caused the subsequent tsunami.

The mechanisms of a loess landslide triggered by diversion-based irrigation: a case study of the South Jingyang Platform, China

Continuous use of diversion-based irrigation has been associated with an increase in the frequency of loess landslides on the South Jingyang Platform, Shaanxi, China. A loess landslide event with a maximum sliding distance of 278 m occurred near the village of Miaodian on May 26, 2015. This landslide event was characterized by four individual landslides. Field investigations, geological exploration, numerical simulation, isotropically consolidated undrained (ICU) triaxial tests, and ring shear tests were conducted to identify its initiation and movement mechanisms. The ICU tests revealed that saturated loess samples were highly liquefiable. High pore water pressure was quickly produced and deviation stress increased the highest value even at low values of axial strain. Geological investigations revealed that cracks penetrated into the saturated zone from the ground surface, and simulation results revealed that these cracks played a dominant role in the infiltration of surface water and led to a rise in the groundwater table. When the infiltration recharge exceeds the holding capacity of the paleosol, the latter behaves as aquifuge under relatively undrained conditions. This process results in the accumulation of water at the bottom of the loess layer, thereby contributing to soil liquefaction and landslide initiation. The ring shear tests revealed that the saturated sand layer of the landslide substrates was subjected to easily inducible high pore water pressure under undrained conditions which led to the thrusting of the sand layer onto the deposit surface and explains the high speed and long runout distance of this landslide.

Geotechnical and hydrological characterization of hillslope deposits for regional landslide prediction modeling

We attempt a characterization of the geotechnical and hydrological properties of hillslope deposits, with the final aim of providing reliable data to distributed catchment-scale numerical models for shallow landslide initiation. The analysis is based on a dataset built up by means of both field tests and laboratory experiments over 100 sites across Tuscany (Italy). The first specific goal is to determine the ranges of variation of the geotechnical and hydrological parameters that control shallow landslide-triggering mechanisms for the main soil classes. The parameters determined in the deposits are: grain size distribution, Atterberg limits, porosity, unit weight, in situ saturated hydraulic conductivity and shear strength parameters. In addition, mineral phases recognition via X-ray powder diffraction has been performed on the different soil types. The deposits mainly consist of well-sorted silty sands with low plastic behavior and extremely variable gravel and clay contents. Statistical analyses carried on these geotechnical and hydrological parameters highlighted that it is not possible to define a typical range of values only with relation to the main mapped lithologies, because soil characteristics are not simply dependent on the bedrock type from which the deposits originated. A second goal is to explore the relationship between soil type (in terms of grain size distribution) and selected morphometric parameters (slope angle, profile curvature, planar curvature and peak distance). The results show that the highest correlation between soil grain size classes and morphometric attributes is with slope curvature, both profile and planar.

Alteration of volcanic rocks and changes in physical-mechanical properties on the South-Kambalny thermal field (South Kamchatka)

The aim of this research project was to consider hydrothermal alteration of volcanic rocks and accompanying changes in their physical and mechanical properties on the thermal field of South Kamchatka. Under the influence of thermal water and steam original andesites and basaltic andesites gradually transform to clay-rich soils and then to opalites and secondary quartzites. The changes in the mineral composition, microstructure, and physical-mechanical properties of rocks and soils in the thermal field were studied. Argillic hydrothermal alteration has gradually decomposed andesites to weak clay-rich soils which form a cover above the field. Elevated sites on the thermal field are composed of opalites and monoquartzites. Progressive hydrothermal alteration of andesites and changes in their properties promotes a broad range of geological phenomena including initiation of landslides, migration of thermal manifestations, changes in relief, and surface deformation.

Numerical modeling of the 2008 Wenchuan earthquake-triggered Niumiangou landslide considering effects of pore-water pressure

Ring-shear experiments are commonly conducted to analyze the kinematic mechanisms of landslides triggered by earthquakes, particularly for landslides impacted by pore-water pressure near the grain-crushing sliding surface. However, pore-water pressure is rarely considered in numerical simulation of the post-failure behavior of earthquake-induced landslides. In this paper, a pore-water pressure model based on the results of ring-shear tests (Cui et al. Landslides 14(3):1–15, 2016) is incorporated into the discontinuous deformation analysis (DDA) for modeling and further understanding the initiation and motion behaviors of the Niumiangou landslide triggered by the 2008 Wenchuan earthquake. The pore-water pressure can be recalculated in each time step before the sliding block is detached from the base in the source area, and the friction coefficient of the sliding surface is simultaneously updated according to the pore-water pressure ratio in the modified DDA. The modified pore-water pressure DDA (PWP-DDA) is validated by means of comparison with the analytical results of the dynamic behaviors of a sliding block on an inclined plane under dynamic acceleration. The simulation results indicate that the pore-water pressure on the sliding surface of the Niumiangou landslide sharply increases within a short period, with small relative displacement of the landslide. Relative to the simulated results from the unmodified DDA, the pore-water pressure calculated by the PWP-DDA promotes higher velocity and longer run-out of the sliding mass. Moreover, the modeling run-out and deposit pattern from the PWP-DDA are in basic agreement with the topography of an actual survey.

LANDSLIDE HAZARD ZONATION MAPPING OF CHAMOLI LANDSLIDES IN REMOTE SENSING AND GIS ENVIRONMENT

Abstract. Landslides are very common problem in hilly terrain. Chamoli region of Himalaya is highest sensitive zone of the landslide hazards. The purpose of Chamoli landslide study, to observe the important terrain factors and parameters responsible for landslide initiation. Lithological, geomorphological, slope, aspect, landslide, drainage density and lineament density map generated in remote sensing and GIS environment. Data information of related geological terrain obtain through topographic maps, remote sensing images, field visits and geological maps. Geodatabases of all thematic layers prepared through digitization of topographic map and satellite imageries (LISS-III, LISS-IV & ASTER DEM). Integrated all thematic layers applying information value method under GIS environment to map the zonation of landslide hazard zonation map validation and verification completed by field visit. The landslide hazard zonation map classified in four classes very high, high, medium and low.

Automatic calculation of rainfall thresholds for landslide occurrence in Chukha Dzongkhag, Bhutan

Bhutan is highly prone to landslides, particularly during the monsoon season. Several landslides often occur along the Phuentsholing–Thimphu highway, a very important infrastructure for the country. Worldwide, empirical rainfall thresholds represent a widely used tool to predict the occurrence of rainfall-induced landslides. Nevertheless, no thresholds are currently designed and proposed for any region in Bhutan. In this work, we define empirical cumulated event rainfall–rainfall duration thresholds for the possible initiation of landslides using information on 269 landslides that occurred between 1998 and 2015 along the 90-km highway stretch between the towns of Phuentsholing and Chukha, in southwestern Bhutan, and daily rainfall measurements obtained from three rain gauges. For this purpose, we apply a consolidated frequentist method and use an automatic tool that identifies the rainfall conditions responsible for the failures and calculates thresholds at different exceedance probabilities and the uncertainties associated with them. Analyzing rainfall and landslide data, we exclude from the analysis all the landslides for which the rainfall trigger is not certain, so we reduce the number of landslides from 269 to 43. The calculated thresholds are useful to identify the triggering conditions of rainfall-induced landslides and to predict the occurrence of the failures in the study area, which is, to date, poorly studied. These rainfall thresholds might be implemented in an early warning system, in order to reduce the risk posed by these phenomena to the population living and traveling along the investigated road stretch.

Numerical Investigation of Rainfall-Induced Landslide in Mudstone Using Coupled Finite and Discrete Element Analysis

In this study, the role of water infiltration on a rainfall-induced landslide in mudstone is investigated. Finite element analysis (FEA) and discrete element analysis (DEA) were employed to explore the driving mechanism in the prefailure regime and the dynamic runout process in the postfailure regime, respectively. The driving mechanism was revealed in terms of the pore water pressures, saturation, and displacement of the sliding zone. To account for water infiltration associated with the dynamic runout process of the landsliding, the sliding friction coefficient in DEA was examined. Based on the results, satisfactory agreement between the numerical analysis and landslide behavior was realized. In prefailure regime, the onset of landslide initiation was found through assessment of rapid change of source displacement (RCSD). The estimated seepage force was about 0.5 N at landslide initiation. In postfailure regime, the results demonstrate that water infiltration and transition in steepness play significant roles in the behavior of the dynamic runout process. The landsliding exhibited a maximum speed of 4.41 m/s and decelerated as it reached a more gentle slope. Overall, the study indicated that the coupling of FEA and DEA can be used to investigate the role of water infiltration and provide useful insights. The approach can be further applied for studies on many other rainfall-induced geohazards to disclose the role of water infiltration with the prefailure and postfailure characteristics.

The Effect of Bedrock Topography on Timing and Location of Landslide Initiation Using the Local Factor of Safety Concept

Bedrock topography is known to affect subsurface water flow and thus the spatial distribution of pore water pressure, which is a key factor for determining slope stability. Therefore, the aim of this study is to investigate the effect of bedrock topography on the timing and location of landslide initiation using 2D and 3D simulations with a hydromechanical model and the Local Factor of Safety (LFS) method. A set of synthetic modeling experiments was performed where water flow and slope stability were simulated for 2D and 3D slopes with layers of variable thickness and hydraulic parameters. In particular, the spatial and temporal development of water content, pore water pressure, and the resulting LFS were analyzed. The results showed that the consideration of variable bedrock topography can have a significant effect on slope stability and that this effect is highly dependent on the intensity of the event rainfall. In addition, it was found that the consideration of 3D water flow may either increase or decrease the predicted stability depending on how bedrock topography affected the redistribution of infiltrated water.

Rainfall events with shallow landslides in the Entella catchment, Liguria, northern Italy

Abstract. In recent decades, the Entella River basin, in the Liguria Apennines, northern Italy, was hit by numerous intense rainfall events that triggered shallow landslides and earth flows, causing casualties and extensive damage. We analyzed landslide information obtained from different sources and rainfall data recorded in the period 2002–2016 by rain gauges scattered throughout the catchment, to identify the event rainfall duration, D (in h), and rainfall intensity, I (in mm h−1), that presumably caused the landslide events. Rainfall-induced landslides affected the whole catchment area, but were most frequent and abundant in the central part, where the three most severe events hit on 23–24 November 2002, 21–22 October 2013 and 10–11 November 2014. Examining the timing and location of the slope failures, we found that the rainfall-induced landslides occurred primarily at the same time or within 6 h from the maximum peak rainfall intensity, and at or near the geographical location where the rainfall intensity was largest. Failures involved mainly forested and natural surfaces, and secondarily cultivated and terraced slopes, with different levels of maintenance. Man-made structures frequently characterize the landslide source areas. Adopting a frequentist approach, we define the event rainfall intensity–event duration (ID) threshold for the possible initiation of shallow landslides and hyper-concentrated flows in the Entella River basin. The threshold is lower than most of the curves proposed in the literature for similar mountain catchments, local areas and single regions in Italy. The result suggests a high susceptibility to rainfall-induced shallow landslides of the Entella catchment due to its high-relief topography, geological and geomorphological settings, meteorological and rainfall conditions, and human interference. Analysis of the antecedent rainfall conditions for different periods, from 3 to 15 days, revealed that the antecedent rainfall did not play a significant role in the initiation of landslides in the Entella catchment. We expect that our findings will be useful in regional to local landslides early warning systems, and for land planning aimed at reducing landslide risk in the study area.

Extracting region-specific runout behavior and rainfall thresholds for massive landslides using seismic records: a case study in southern Taiwan

Typhoon Morakot struck Taiwan on 7 August 2009, bringing severe rainfall and landslides. Of the many landslides caused by the storm, 12 large-scale landslides were discovered based on seismic signals recorded from broadband seismic stations. Landslides inventoried from both seismic records and satellite imagery are used as baseline data to evaluate region-specific forensic analyses of landslide features, e.g. disturbed area, width and runout distance (Drunout), associated with landslide-induced seismic signals and signal durations (Δt). The results of these analyses show that (i) the landslide-disturbed area correlated well with signal duration when Δt was over 60 s; (ii) the landslide-disturbed area correlated well with the ratio of the landslide width to runout distance when Δt was under 40 s; (iii) the runout distance of sliding mass exhibited a positive relation with Δt2, satisfying the energy conserved during mass movement. This case study presents a region-specific examination of the Δt-Drunout relationship based on 12 large-scale landslides that occurred during Typhoon Morakot, providing insight into the sliding processes. In addition, the time of landslide initiation was extracted from seismic signals in order to better understand region-specific, large-scale, landslide rainfall thresholds. These relationships indicate that (a) long-duration rainstorms with high cumulative rainfall tend to dictate the occurrence of large-scale landslides; (b) the rainfall threshold for large-scale landslides is found to be higher than in previous studies that also include smaller landslides, defined in this region as I = 60D−0.31, where I is the rainfall intensity (mm/h) and D is the duration (h) of the rainstorm.

Landslides and flash floods induced by the storm of 22nd November 2011 in northeastern Sicily

On 22nd November 2011, after extreme rainfall (more than 350 mm fell in 10 h), thousands of shallow landslides evolving into debris flows occurred in several torrent catchments of Peloritani ridge, northeastern Sicily, carrying a large amount of wood. A rapid increase in torrent discharge occurred during the storm, inducing floods of the Longano and Mela torrents, also amplified by wood obstructions of bridges. A detailed reconstruction of the main geo-hydrological events has been done. Landslides have been mapped by satellite photos and checked by field surveys, and were found to be particularly concentrated in the Longano, Mela and Saponara catchments. The timing of landslide initiation has been estimated by technical report data, eyewitnesses, and by calibration of the Leaky Barrel Model [Wilson, Wiezoreck, Environ Eng Geosci 1(1):11–27, 1995]. The recorded amount of rainfall has been transformed into the torrent discharge by the HEC-HMS model, using a detailed digital elevation model (DEM) with resolution of 2 × 2 m, and the torrent hydrograph has been obtained corresponding to several river sections. In the urban area of Barcellona Pozzo di Gotto, the torrent discharge reached its peak before the arrival of the large trunks, indicating that the main cause of the inundation in the urban area was the bridge obstruction. The aim of this study is to provide a detailed case history of landslides inducing floods, and their relationship with the use of simple hydrological models, which could help in estimating the risk of inundation caused by a large amount of wood in unmonitored catchments.

Mechanical state of gravel soil in mobilization of rainfall-induced landslides in the Wenchuan seismic area, Sichuan province, China

Abstract. Gravel soils generated by the Wenchuan earthquake have undergone natural consolidation for the past decade. However, geological hazards, such as slope failures with ensuing landslides, have continued to pose great threats to the region. In this paper, artificial model tests were used to observe the changes of soil moisture content and pore water pressure, as well as macroscopic and microscopic phenomena of gravel soil. In addition, a mathematical formula of the critical state was derived from the triaxial test data. Finally, the mechanical states of gravel soil were determined. The results had five aspects. (1) The time and mode of the occurrence of landslides were closely related to the initial dry density. The process of initiation was accompanied by changes in density and void ratio. (2) The migration of fine particles and the rearrangement of coarse–fine particles contributed to the reorganization of the microscopic structure, which might be the main reason for the variation of dry density and void ratio. (3) If the confining pressure were the same, the void ratios of soils with constant particle composition would approach approximately critical values. (4) Mechanical state of gravel soil can be determined by the relative position between state parameter (e, p′) and ec–p′ planar critical state line, where e is the void ratio, ec is the critical void ratio and p′ is the mean effective stress. (5) In the process of landslide initiation, dilatation and contraction were two types of gravel soil state, but dilatation was dominant. This paper provided insight into interpreting landslide initiation from the perspective of critical state soil mechanics.

Interaction between Perched Epikarst Aquifer and Unsaturated Soil Cover in the Initiation of Shallow Landslides in Pyroclastic Soils

A physically based mathematical model of the slope of Cervinara (southern Italy), which is characterized by a shallow pyroclastic soil cover laying upon a limestone fractured bedrock, has been developed. Previous and current ongoing monitoring suggested that leakage through the soil–bedrock interface occurred, with leaking water temporarily stored in a perched aquifer located in the upper part of the fractured limestone (epikarst). This aquifer supplied several springs, and recharge to the deeper groundwater circulation occurred. Hence, in the proposed model, the unsaturated water flow taking place within the soil cover is coupled with the saturated water flow in the perched aquifer. The application of the model to the simulation of the slope hydrologic behavior over a period of 11 years, between 2006–2017, provides realistic results in terms of soil storage, epikarst storage, spring discharge, and groundwater recharge. The different response times of soil and epikarst aquifer to precipitation input allow distinguishing the hydrological predisposing causes of potential landsliding (i.e., a few months of persistent rainfall that is capable of filling the epikarst aquifer) from the triggers, which are represented by single intense rainfall events. The application of the model offers a key of interpretation of the hydrological processes leading to the landslide that occurred on 16 December 1999.

Spatio‐temporal variability of extreme precipitation in Nepal

Nepal is one of the most vulnerable countries to climate change impacts. Extreme weather events associated with heavy precipitations are the principal causes of landslides, debris flows and all types of floods disasters in the country, which by causing tremendous losses of life and property affects the socio‐economic development. Given the limited availability of knowledge in spatio‐temporal distribution of precipitation in Nepal, this study analyses the spatial distribution of monthly and annual precipitation and 1‐day extreme precipitation and their trends utilizing a large number of stations (291 stations for the first time) distributed across the country for the period of 1966–2015. This study focuses on the exploration of elevational dependencies of precipitation to demonstrate the effect of topographic heterogeneity caused by the numbers of broad and narrow river valleys and mountain slopes and ridges. Also, this study investigates the relation of 1‐day extreme precipitation with mean annual precipitation. Our results show the peak annual precipitation elevation between 2,000 and 3,500 m above sea level, while in contrast 1‐day extreme precipitation peaks are found at lower elevation in the southern foothills with its highest intensity in a central region of the country. The occurrence of 10% of mean annual precipitation in a single day has been observed in 75% of the analysed stations which in turn indicates the high likelihoods of initiation of landslides, soil erosions and floods in different parts of the country. There is no definitive countrywide decadal trend in extreme precipitation intensity and occurrence. A station‐wise trend clearly shows the increase in extreme precipitation events in western mountainous regions in the recent decades. In other locations, the mixed patterns of station‐wise increasing and decreasing trends are found.

First-time landslides in Vashon advance glaciolacustrine deposits, Puget Lowland, U.S.A.

Advance glaciolacustrine (Qglv) deposits from the last continental glaciation are widespread in the densely populated Puget Lowland and are prone to shallow landsliding. Much less frequently in historic time, new landslides propagate deeply within intact Qglv deposits. The exceptional volume and highly mobile nature of the 22 March 2014, State Route 530 (Oso) landslide generated considerable uncertainty and public concern about the likelihood for similar deep-seated failures initiating from most any slope where these deposits crop out. The primary study objectives are to utilize geotechnical data from the small data set of available published and public-domain investigations to characterize, in general terms, hydrogeologic, geotechnical and geomorphic factors and their relative contribution to initiating deep-seated landslides within intact Qglv deposits; and to inform future hazard and risk assessments for first-time landslides within these deposits.Qglv deposits are overconsolidated, very stiff to hard, laminated to massive, silt and clay. Shear strength is anisotropic, with cohesion being a significant component of bedding-parallel strength and friction dominating strength perpendicular to bedding. Hydraulic conductivity is likely also anisotropic. Multi-year records of pore pressures within Qglv deposits show no to minor seasonal flux; only minor pore pressure responses to multi-day to multi-week episodes of heavy precipitation have been detected. Back analyses using limit-equilibrium methods and peak anisotropic strength under drained conditions demonstrate initial stability of the slopes. Instability occurs near the fully softened strength. We conclude that, over the long term, loss of cohesive strength, rather than hydroclimatic pore pressure response, is the more important contributor to diminishing stability and, in some cases, initiation of first-time landslides in Qglv deposits. The shape and location of the slide surface is strongly influenced by strength anisotropy and stress state. Sliding surfaces developed near the basal contact of the Qglv deposits in all of the five studied landslides. Higher stress states associated with increasing sequence thickness of the landslide masses decrease stability. The length of the basal slide surface, and thus the aspect ratio of the landslide mass, appears to increase proportionally with sequence thickness of the landslide mass.

The Aso-Bridge coseismic landslide: a numerical investigation of failure and runout behavior using finite and discrete element methods

The complex coseismic process of the Aso-Bridge landslide during the main shock of the 2016 Kumamoto Earthquake was investigated. Finite element analysis and discrete element analysis considering vertical seismic accelerations (VSA) were conducted to explore the salient features of the prefailure mechanism and postfailure kinematic process of the coseismic landslide associated with the initiation time and kinematic runout behavior, respectively. Two seismic input conditions, one involving only horizontal seismic accelerations (HSA), and the other accounting for both HSA and VSA, were used to assess the influence of VSA from the prefailure to postfailure regimes. First, satisfactory agreement between the study and the published results in terms of landslide initiation time was obtained. As revealed by the rapid change of source displacement (RCSD), VSA did not alter landslide initiation time; however, it significantly increased the RCSD approximately 2-fold, which provided a clear initiation time. At landslide initiation, the estimated average velocities in a vertical direction increased approximately 16-fold (from −0.011 to −0.174 m/s) by accounting for VSA. Second, the results suggested that VSA had a trivial influence on runout behavior in the postfailure regime, given that such behavior was dominated by the collision and free fall during the sliding as well as the terrain features. With an average velocity of 21.34 m/s, the sliding source ultimately reached the riverbank within 21 s. The paper demonstrates that a combination of FEA and DEA can be used to investigate the coseismic process of the Aso-Bridge landslide and lead to satisfactory agreement with the event. Our comprehensive analysis provides insight into the role of VSA in earthquake-induced landslides.

Formation process of two massive dams following rainfall-induced deep-seated rapid landslide failures in the Kii Peninsula of Japan

Extreme heavy rainfall due to Typhoon Talas on September 2–4, 2011 in the Kii Peninsula, Japan, triggered numerous floods and landslides. This study investigates the mechanism and the entire process of rainfall-induced deep-seated landslides forming two massive dams in the Kuridaira and Akatani valleys, respectively. The mechanism of the rapid deep-seated landslides is examined through a series of laboratory experiments on samples from sliding surfaces by using undrained high-stress dynamic-loading ring-shear apparatus. The test results indicate that the failure of samples is triggered by excess pore water pressure generation under a shear displacement from 2 to 7 mm with a pore pressure ratio ranging from 0.33 to 0.37. The rapid movement of landslides is mainly attributed to high mobility due to the liquefaction behavior of both sandstone-rich and shale samples. Geomorphic settings and landslide mobility are major contributing factors to the dam formation. Additionally, shear displacement control tests show that a certain amount of shear displacement between 2 and 7 mm along the sliding surfaces of the gravitationally deformed slopes might have led to the failures. Importantly, computer simulation with LS-RAPID software using input parameters obtained from physical experiments is employed to interpret the entire formation process of the abovementioned two landslide dams. The simulation results are examined in accordance with the observed on-site geomorphic features and recorded data to explain the possibility of sliding processes. The results further point out that local failures are initiated from the lower middle part of the landslide bodies where the geological boundary exists. This condition most probably influences the landslide initiation in the two case studies. This research is therefore helpful for hazard assessment of slopes that are susceptible to deep-seated landslides and other sequential processes in areas with geology and geomorphology similar to that of the Kii Peninsula.

On the initiation, movement and deposition of a large landslide in Maoxian County, China

At 5 am 24th June 2017, a catastrophic landslide hit Xinmo Village, Maoxian County, Sichuan Province, China. The slide mass rushed down from an altitude of 3400m and traveled 2700 m in a high velocity. The 13 million m3 deposition buried the whole village and caused about 100 deaths. The source area of the landslide is located in a high steep slope, average slope angle is 40o and maximal angle is 65o. The strata are interbedded Triassic Zagunao Formation metamorphic sandstone and slate with the dip slope angle of 45°. Based on high-resolution satellite remote sensing image, UAV image, DEM data, and field investigation, failure mechanism, travel features, and deposit characteristics were analyzed. The results showed that this landslide was influenced by Songpinggou Fault zone. According to the topography before the failure, the landslide is located in the back scarp of an antecedent landslide induced by Diexi Earthquake in 1933. The bedding slope provided potential rupture surface. Historical seismic activities and long-term gravitational deformation caused rock mass accumulated damages. Weathering and precipitation weakened the rock mass and finally induced shearing and tension failure. A huge block detached from the top rock slope, pushed the past landslide deposits in the middle part, rushed out of the slope bottom in a high velocity and buried the Xinmo Village. The rapid movement entrained and brought the soil into the Songping Gully which recoiled with and bounced back from the opposite mountain.

Impact of climate change on landslides frequency: the Esino river basin case study (Central Italy)

Researchers have long attempted to determine the amount of rainfall needed to trigger slope failures, yet relatively little progress has been reported on the effects of climate change on landslide initiation. Indeed, some relationships between landslides and climate change have been highlighted, but sign and magnitude of this correlation remain uncertain and influenced by the spatial and temporal horizon considered. This work makes use of statistically adjusted high-resolution regional climate model simulations, to study the expected changes of landslides frequency in the eastern Esino river basin (Central Italy). Simulated rainfall was used in comparison with rainfall thresholds for landslide occurrence derived by two observation-based statistical models (1) the cumulative event rainfall–rainfall duration model, and (2) the Bayesian probabilistic model. Results show an overall increase in projected landslide occurrence over the twenty-first century. This is especially confirmed in the high-emission scenario representative concentration pathway 8.5, where according to the first model, the events above rainfall thresholds frequency shift from ~ 0.025 to ~ 0.05 in the mountainous sector of the study area. Moreover, Bayesian analysis revealed the possible occurrence of landslide-triggering rainfall with a magnitude never occurred over the historical period. Landslides frequency change signal presents also considerable seasonal patterns, with summer displaying the steepest positive trend coupled to the highest inter-model spread. The methodological chain here proposed aims at representing a flexible tool for future landslide-hazard assessment, applicable over different areas and time horizons (e.g., short-term climate projections or seasonal forecasts).