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On June 17, 2020, Aniangzhai landslide, an ancient landslide located in Danba County, southwest China, was reactivated by Meilonggou debris flow. The front edge of the slope collapsed, mobilizing a soil mass of about 2.35 × 106 m3. Evaluating the stability of the whole slope is of great importance to avoid further landslides and mitigate the damage for Aniangzhai villagers living on this slope. This paper focuses on the inaccessible upper slope of Aniangzhai landslide (no attention paid before) that exhibits a relative elevation difference of more than 1000 m. Multi-source remote sensing, including unmanned aerial vehicle (UAV) photogrammetry, light detection and ranging (LiDAR), and satellite-based interferometric synthetic aperture radar (InSAR) techniques, was used in this research to identify and evaluate this high mountain upper slope potential hazard in Aniangzhai landslide. Considering the huge height difference and the steep slope of Aniangzhai landslide, an iterative route planning method was proposed and adopted to obtain a 3D model with 0.02 m resolution and a DEM with 0.25 m resolution by using UAV and LiDAR close-in flight method, respectively. Meter-level huge cracks were clearly identified by the high-resolution UAV 3D model and LiDAR data, which confirm that the location of these cracks is related to the morphological structure of this ancient landslide. Time series InSAR analysis reveals the activity of this high-altitude area, with a maximum LOS displacement rate of 15 cm/a. The combination of the above remote sensing technologies confirms and reveals the high potential risk and the reactivated condition of the upper slope of Aniangzhai landslide. Through this finding, we show that the evolution of Aniangzhai landslide happened through four stages with a cascading effect. This paper proves the usefulness of an integrated method to successfully identify and evaluate the high-altitude upper slope potential hazard and compares the technical features of them, providing a reference for future works that aimed at mitigating the potential damage of the upper slope. [ABSTRACT FROM AUTHOR]

Landslides which occur at unexpected locations and times, and which have unrecognizable risk areas, often cause mass casualties. Despite there being few preceding landslides in the same season, the catastrophic Qijiaba landslide occurred in the new government-selected settlement of Wufu village, Sichuan Province, China, on September 5, 2021, killing three people and destroying 13 houses. In this paper, the landslide features and causes are discussed based on field investigations, remote sensing interpretations, and laboratory-based soil experiments. The results showed that it was a typical soil landslide within a geomorphic hollow of the slope with a volume of 20,230 m3, recurrence interval of at least 69 years, and runout distance of 137.5 m. This type of landslide is difficult to predict. The soil strength in the sliding surface decreased suddenly as the water content increased, and the soil's rich clay mineral and high clay particle contents determined its high mobility (Heim's ratio of 0.44). The occurrence time of the Qijiaba landslide lagged 1.3 days behind the peak rainfall, and the 2-day cumulative rainfall was a crucial factor in the landslide occurrence. Finally, the large water confluence area behind the main scarp was determined to be 3.9 times the area of the landslide itself, thereby providing abundant water conditions to induce failure. The factors underlying the casualties included inappropriate site selection, insufficient awareness of potential landslides, and failure to evacuate in time. The results of this study provide a basis for future prevention, mitigation, and early warning of similar landslides. [ABSTRACT FROM AUTHOR]

A rainfall-induced catastrophic landslide occurred at UTC + 8 03:50 local time on August 21, 2020, in Zhonghaicun village (N 29°20′30″, E 102°41′40″), Hanyuan County, Sichuan Province, China, resulting in damage to 6 buildings and 9 casualties (7 fatalities and 2 missing). In this paper, multitemporal remote sensing images, comprehensive field investigations, drilling holes, deformation monitoring, and numerical simulations are used to identify the main characteristics and the formation mechanism of the event. The results showed that long-term intensive rainfall in 2020 played an essential role in the failure of the Zhonghaicun landslide and that strong earthquakes in Wenchuan County (Ms 8.0, on 12 May 2008) and Lushan County (Ms 7.0, on 20 April 2013) also exerted a negative influence on the evolution process of this catastrophic landslide. Several traction zones appeared after the occurrence of the landslide. Fortunately, no evident deformation was observed and these slopes were in a stable state. In addition, a large-scale potential sliding slope, four small-scale landslides, and a debris flow were found in the study area. [ABSTRACT FROM AUTHOR]

Landslide disasters are associated with severe losses on the Loess Plateau of China. Although early warning systems and susceptibility mapping have mitigated this issue to some extent, most methods are qualitative or semi-quantitative in the site-specific range. In this paper, a quantitative spatial distribution model is presented for site-specific loess landslide hazard assessment. Coupled with multi-temporal remote sensing images and high-precision UAV cloud point data, a total of 98 loess landslides that have occurred since 2004 on the Heifangtai terrace were collected to establish a landslide volume-date and retreating distance database. Eleven loess landslides are selected to construct a numerical model for parameter back analysis, and the accuracy of the simulation results is quantitatively evaluated by the centroid distance and overlapping area. Different volumes and receding distance rates of landslides are fitted to determine the relationship between cracks and potential volume, and different volumes and parameters are combined to simulate the spatial distribution of potential loess landslides. The results of this study reveal that landslide volumes mainly range between 1 × 103 and 5 × 105 m3, and the historical occurrence probability reaches 0.551. The optimal parameters are estimated by the maximum likelihood method to obtain a uniform distribution parameter value probability model, and the results show that the error of the estimated length within a range of 0.05 from the optimal parameter does not exceed 15%. In the selected slope slide case, farmland near the toe of the slope primarily includes exposed hazards with probabilities greater than 0.7. This work provides a useful reference for local disaster reduction and a theoretical methodology for hazard assessments. [ABSTRACT FROM AUTHOR]

The May 12, 2008 Wenchuan earthquake of China (Mw 7.9 or Ms 8.0) triggered hundreds of thousands of landslides. Mapping such a large number of landslides is a major task, considering the large size of the affected area and the availability of pre- and post-earthquake remote sensing images. This paper compares three (nearly) complete landslide inventories that were compiled from visual image interpretation. The three inventories differ in the manner in which the landslides are represented, either as polygons, centroid points, or top points. Landslides in the three inventories use one-to-one correspondence. Each of the three inventories includes a large proportion of the 197,481 landslides triggered by the earthquake. These landslides were delineated as individual solid polygons and points using visual interpretation of high-resolution aerial photographs and satellite images acquired following the earthquake and verified by selected field checking throughout a broad area of approximately 110,000 km. These landslides cover a total area of approximately 1,160 km. Based on the inventories of landslide polygons and landslide centroid points, two types of density maps were constructed. Correlations of landslide occurrence with seismic, geologic, and topographic parameters were analyzed using the three landslide inventories. Statistical analysis of their spatial distribution was performed using both the landslide area percentage (LAP), defined as the percentage of the area affected by the landslides and the landslide number density (LND), defined as the number of landslides per square kilometer. There are two types of LNDs: the LND-centroid (based on the centroid point of the landslide) and the LND-top (based on the top point of the landslide). We used the three indexes to determine how the occurrence of the landslides correlates with elevation, slope angle, slope aspect, slope position, slope curvature, lithology, distance from the epicenter, seismic intensity, distance from the Yingxiu-Beichuan surface fault rupture, peak ground acceleration (PGA), and coseismic surface displacements (including horizontal, vertical, and total displacements). Both the LAP and the two types of LND values were observed to have continuous positive or negative correlations with the slope angle, slope curvature, distance from the epicenter and from the Yingxiu-Beichuan surface fault rupture, seismic intensity, and coseismic surface displacement. In addition, the highest values of the LAP and LND values appear at ranges from 1,200 to 3,000 m in elevation. Moreover, the landslides have preferred orientations, dominated by the eastern, southeastern, and southern directions. In addition, the sandstone, siltstone (Z), and granitic rocks experienced more concentrated landslides. No obvious correlations were observed between the LAP and LND values and slope position. Finally, we studied the orders of eight earthquake-triggered landslide impact factor effect on landslide occurrence. Highlights: The 197,481 landslides triggered by the 2008 Wenchuan earthquake were delineated. Three landslide inventories were constructed: polygon, centroid, and top point inventories. The landslides were spatially analyzed with topographic, lithology, and seismic parameters. [ABSTRACT FROM AUTHOR]

On September 5, 2022, an Ms6.8 earthquake struck Luding County, Sichuan Province, China. Through creating a coseismic landslide prediction model, we obtained the spatial distribution of the triggered geological hazards immediately after the earthquake. Through collecting all available multi-source optical remote sensing images of the earthquake-affected area via UAV and satellite platforms, the exact information of coseismic landslide was achieved by pattern recognition and visual inspection. According to the current results, the Luding earthquake triggered 5336 landslides with a total area of 28.53km2. The spatial distribution of the coseismic landslides is correlated statistically to various seismic, terrain, and geological factors, to evaluate their susceptibility at regional scale and to identify the most typical characteristics of these failures. The results reveal that the coseismic landslides mainly occurred on the sides of the Xianshuihe fault (within 1.2 km) and Dadu River (within 0.5 km) in striped patterns. They are concentrated in the regions with an elevation range of 1000–1800 m, a slope range of 25–55°, and lithologies of acid plutonic rocks, mixed sedimentary rocks, and siliciclastic sedimentary rocks. Besides, the coseismic landslides of the Luding earthquake are smaller in size and shallower than those triggered by the 2008 Wenchuan earthquake and the 2017 Jiuzhaigou earthquake. Rapidly achieving the spatial locations and distribution patterns of the coseismic landslides enables to provide effective support and guidance to emergency rescue, risk mitigation, and reconstruction planning. [ABSTRACT FROM AUTHOR]

At 18:00 on July 19, 2019, the ancient Yahuokou flow-like landslide in Dongshan Town, Zhouqu County, Gansu Province, China, was revived. The landslide mass of about 3.92 × 106 m3 was revived step by step, slid down the slope, and finally slipped into the Minjiang river, causing the Minjiang river to become a semi-blocked state, the water level of the river rose, and the riverside road was interrupted. The landslide is 1920 m long, with a height difference of 550 m and an apparent friction coefficient of 0.286. It is a typical push-type large-scale long-striped fault-fractured zone accumulation landslide, which is controlled by the Pingding-Huama fault zone. Under the action of long-term rainfall, the trailing edge of the upper section of the landslide first undergoes slow creep deformation, which eventually leads to the overall instability and decline of the upper section of the landslide, and then loads the upper part of the middle section of the sliding mass, which promotes the instability and decline of the middle section of the sliding mass. Finally, the sliding mass in the middle section exerts a load on the upper part of the sliding mass in the lower section, which revives the sliding mass in the lower section and gradually slides into the Minjiang river. Through field investigation, remote sensing interpretation, and borehole investigation, the basic characteristics and information of landslide deformation and movement are obtained. The limit equilibrium method is used to analyze the revival mechanism and the spring model is proposed to analyze the movement mechanism of the landslide. With the help of DNA-W numerical simulation software, the sliding process of the upper sliding mass is simulated by a frictional rheological model to verify the spring model. The analysis of the dynamic mechanism of the Yahuokou flow-like landslide will help provide a reference for the research on the instability and movement mechanism of the landslide in the Pingding-Huama fault zone, and provide the necessary scientific basis for the prevention and mitigation of landslide disasters. [ABSTRACT FROM AUTHOR]

The deep-seated gravitational slope deformation (DSGSD) triggered by impoundment has attracted worldwide attention. After impoundment of Wudongde reservoir downstream of Jinsha River, China, Zaogutian DSGSD occurred with an estimated volume of 129 million m3, which provided an opportunity for in-depth analysis and cognition of its mechanism and risk. The DSGSD sits on a chair-shaped bedding bank slope with multi-weak interlayers at the bottom, forming a lithology structure of brittle cap overlying a ductile substratum. Based on the traditional engineering geological exploration, 3D observation of the DSGSD was carried out by UAV photogrammetry, and the cracks, discontinuities, and macroscopic deformation characteristics of different areas were identified. Combining the InSAR survey and surface-parallel flow assumption, the mm-level 3D deformation rate field and time-series displacement from December 2019 to December 2020 were reconstructed. Finally, the following conclusions were arrived at: according to the cracks and the boundary between rock mass and deposit, the DSGSD could be divided into four zones: the loose deposit near the bank, the scarp area in the front part, the major sliding area in the middle part, and the stable area. The loose deposits were deforming by uplifting with a maximum rate of 70 mm/year. The deformation rate in the western part of the major sliding area was the fastest, and the rates of the maximum settlement and southward deformation peaked at 100 mm/year and 250 mm/year, respectively, which were 2–3 times data in the scarp area. Under the soaking of reservoir water, the mechanical magnitude of the weak layer in the lower Dengying Formation and the Guanyinya Formation got reduced, which was the triggering factor of Zaogutian DSGSD. As a result, the major sliding area pushed the scrap area to creep along with the weak layer, and sliding accompanied by tensile fracturing is the instability mode in case of failure. The combination of InSAR and UAV observation provides a deeper insight into the deformation mechanism of DSGSD, which is not only conducive to slope stability evaluation but also demonstrates the role of remote sensing technology in the study of DSGSD. [ABSTRACT FROM AUTHOR]

The Heifangtai terrace, in Northwest China, is a typical area where loess landslides have been induced by agricultural irrigation, and many of the landslides are prone to reactivation. However, the spatiotemporal evolution and hydrological-triggering mechanisms of loess landslide reactivation are not well understood. In this research, multiple remote sensing (SBAS-InSAR, TLS, and optical remote sensing), integrated with time-lapse ERT (tl-ERT) imaging, was used to monitor the post-failure evolution of the Luojiapo landslide in Heifangtai during the period of May 2015 to Nov. 2020. Pronounced temporal and spatial differences in the deformation and hydrological evolution of landslides after sliding were observed. The largest displacement rates occurred in the landslide source area, and the lateral extension of the landslide source area caused by spatial differences in reactivation is an important feature of landslide evolution. In the landslide area, the groundwater table (GWT) decreased at first ascribed to the spring hole caused by the exposure of the GWT after sliding and then increased due to the subsequent continuous irrigation, and the lag time of the GWT response to irrigation decreased significantly. Spatial differences in GWT evolution are one of the main causes of spatial differences in landslide reactivation, and reactivation was more likely to occur where the GWT fluctuated at a high level. The GWT also fell with local reactivation. Our findings highlight the potential for obtaining internal and external spatiotemporal information of loess landslide evolution using multiple remote sensing integrated with tl-ERT. Our results also help to understand the reactivation process of irrigated loess landslides and provide a reference for the monitoring and early warning of such landslides. [ABSTRACT FROM AUTHOR]

Enhanced debris flow activity observed after the 2008 Wenchuan earthquake, Sichuan Province, SW China, is still intense more than a decade since the earthquake. A heavy rainstorm on 20 August 2019 caused catastrophic debris flows in the epicentral area of the earthquake. By remote sensing imagery interpretation and field investigation, 13 debris flows were identified. An empirical rainfall threshold I-D model (intensity–duration) of post-seismic debris flows is established. Changing rainfall thresholds, characteristics, and initiation mechanisms of the 2019 debris flows were analyzed, which are different from the events that occurred in previous years. We find that the 2019 debris flows were mainly initiated by concentrated runoff erosion of sediments stored in tributary channels of catchments, with little contribution from the coseismic landslides and new hillslope failures. Differently, the major sediment supply of debris flows in previous years was mainly from the reactivation of coseismic landslide deposits. By analyzing the triggering rainfall of all recorded debris flows after the Wenchuan earthquake, we find that the rainfall threshold in 2019 is about 1/2–4/5 of the pre-earthquake value, and the I-D model we built can predict the 2019 debris flows successfully. Considering that there are still a large number of coseismic landslide deposits in the mountain catchments and the rainfall thresholds are slowly recovering, the post-seismic debris flows may last for a long period. [ABSTRACT FROM AUTHOR]

This article describes the Zhongbao landslide that occurred in Liujing Village, Tudi Township, Wulong District, Chongqing, China, on July 25, 2020. Due to the catastrophic soil and rock landslide, the houses and village roads of three villagers in the landslide area are damaged and formed weirs. The landslide eventually formed a barrier lake. In order to reveal the failure mechanism of the landslide, aerial data was collected on the landslide site using UAV and high-resolution remote sensing images. The characteristics of the landslide are analyzed based on the geological conditions and the properties of the rock formations in the landslide area. The continuous intense rainfall increased the water content of the landslide in this area, increasing its weight. Increasing the water content softens the sliding surface and lowers strength. Therefore, the rock and soil mass on the upper slope slides along the sliding surface under the action of gravity, causing a shale rock mass of about 1.3 million cubic meters to slide quickly from the upper part of the slope into the V-shaped valley and form a barrier dam and barrier lake. By evaluating the rising height of the initial dammed lake, the affected area can be predicted. Through the analysis of the study area, it can provide references for the failure mechanism of landslides, the characteristics of landslide bounce, and the risk assessment of cofferdams in Southwest China. [ABSTRACT FROM AUTHOR]

The reactivation of landslides has always been a prominent problem that has endangered town construction and people's safety worldwide. At about 8 a.m. on July 12, 2018, on a mountain near the Bailong River in Nanyu Township, Zhouqu County, Gansu Province, China, a landslide collapse event occurred. About 10,000 m3 of sloped material slid into the Bailong River, with the largest stone reaching 3 m3. As a result, a large number of houses were flooded. Highways and bridges were destroyed. Using field investigations, unmanned aerial vehicle (UAV) photography, InSAR traces, historical records, and multiple remote sensing images, we extracted the landslide's geometry and geomorphic parameters to quantify the characteristics of the Jiangdingya landslide. Based on high-resolution topographic data collected before and after the landslide, the change in the geomorphological factors, geomorphologic stability, and detection of the precursory motion before the landslide failure were analyzed to fully investigate the temporal geomorphological changes. Synthesizing the above research, we discuss the causes of landslide reactivation. The Jiangdingya landslide is a typical ancient landslide formed by the coupling of internal and external dynamics. Rainfall, seismic fault zone activity, human activities, and river erosion were the main causes of this reactivation event. [ABSTRACT FROM AUTHOR]

Rock avalanches are unpredictable due to their complex geological conditions and dynamics and such features have been regarded as important reasons for property damage and fatalities. The Ganluo rock avalanche of August 14, 2019 in China provides an outstanding case to evaluate the failure mechanism and dynamic process of long-runout rock avalanches. To understand the failure mechanism and dynamics of such events, a combination of in situ investigation, remote sensing data study, and simulation is performed. The result shows that the Ganluo rock avalanche released a rock mass volume of approximately 5.20 × 104 m3 that detached from the slope, and 1.52 × 104 m3 of unstable rock mass is still in the source zone. The analysis indicated that the prerequisite for the rock avalanche was continuous heavy rainfall, which occurred in the preceding months. The simulation shows the maximum sliding velocity is approximately 22 m/s. Additionally, the potential destructive zone of the unstable rock mass is evaluated, which can provide a reference for secondary disaster prediction. [ABSTRACT FROM AUTHOR]

To determine the emplacement mechanisms of rock avalanches, the surficial and internal sedimentological characteristics of avalanche deposits are attracting increased scientific interest. In this study, deposits of the massive paleoseismic Tagarma rock avalanche in the Tarim Basin of the Pamir-western Himalayan syntaxis, China, are investigated to enrich the knowledge on rock avalanche dynamics. Based on a combination of remote sensing data and in situ surveys, a series of typical surficial landforms, including a Toreva block, arc-shaped transverse ridges, aligned megablocks, and longitudinal lineament, are studied in detail. Clusters of superimposed gneiss megablocks preserving the bedrock structures of the source scar are widely distributed along the travel path. Moreover, inverse grading in the deposit and a substrate characterized by clast-supported pebbles with imbricate structures are also observed. Cracks and fissures are common in most pebbles, indicating intense interactions between the avalanche mass and the substrate. Through analysis of these surficial and internal characteristics, we propose that the avalanche mass should have propagated rapidly as a single unit with slight internal mixing and high internal pressure fluctuations. These internal pressure fluctuations obviously exceeded the overburden pressure and contributed to the intense shattering of the main deposit, especially the basal facies. The basal facies was mainly emplaced by a frictional, simple shear process and controlled the avalanche hypermobility. From the proximal to the distal parts, the transport of the avalanche mass can be classified as an extension-dominated sliding process in the transition zone and a compression-dominated sliding process in the accumulation zone. [ABSTRACT FROM AUTHOR]

Ridge-top rockslides frequently cause huge property losses and casualties due to the difficulties involved in detecting their precursors by means of manual surveys. Their early identification and the surrounding area's evaluation in terms of potential danger are essential for preventing disasters. The recent large rockslide which occurred at Su Village, which is in possession of data related to pre-failure images, real-time video, and post-failure boreholes, is helpful for providing new insights into the processes associated with these events. Due to a strong sustained rainfall, a large volume of granite blocks rapidly descended from the upper part of the hillside, causing 27 deaths and destroying more than 20 houses. It is found that the early identification of the hazard associated with such rockfalls can be made by the analysis of remote sensing images and Persistent Scatterer Interferometry (PSI) analysis of Synthetic Aperture Radar (SAR) data. The depth-integrated continuum method, including taking the entrainment effect into account, was adopted to analyze the dynamic processes and to identify the areas at risk. The computational results show that the evaluated runout distance and extent match well with the field investigation results. The parameter sensitivity surrounding cohesion, coefficients of lateral earth pressure, and volume amplification were analyzed. It is demonstrated that the cohesion plays a significant role in the dynamic processes and the deposited area. However, the effects from the earth pressure coefficient and volume bulking are comparatively weaker. [ABSTRACT FROM AUTHOR]

The Aizigou paleolandslide is a large basalt landslide in the Liucheng section of the Lower Jinsha River, southwestern Sichuan Province, China. Geological investigation and interpretation of remote sensing imagery, in addition to experiments, numerical simulation, and geochronological dating were used to determine the formation and movement of the landslide. Four factors were critical: a substantial height difference between the landslide shearing surface and the foot of the slope; multiple structural defects within the rock mass; a tuff intercalation in the basaltic series with long-term softening due to surface water and groundwater; and seismic activity. The kinematic behavior of the landslide was simulated using a 3-D discrete element model (3DEC), with four stages: (1) Seismic waves in the upper part of the slope were amplified by the mountain topography. When the vibrational energy exceeded the strength of the rock mass, the landslide formed, with deformation and failure by sliding and fracture. (2) Landslide materials with a volume of approximately 3.82 × 108 m3 slid at high speed from a high position, before colliding with the mountainside on the right bank of Aizi Valley. (3) The high-speed debris flow then moved 3 km downstream in Aizi Valley. (4) Landslide materials with a volume of 2.72 × 108 m3 blocked Jinsha River. A lake formed behind the barrier dam; its backwater region reached 75 km upstream. Optically stimulated luminescence dating of the lake sediments suggested that the landslide occurred about 25,000 years ago. [ABSTRACT FROM AUTHOR]

In order to analyze the changes in the sediment budget after the Wenchuan earthquake and after the heavy rain events in the following years, 12 debris flow gullies in the Longchi Dujiangyan County were selected. A comparison of the TM images taken on 18 September 2007 (before the '5.12' Wenchuan earthquake) with the SPOT5 images taken on 10 February 2009 (after the '5.12' Wenchuan earthquake) indicates that the landslide area in the 12 debris flow watersheds increased from 83.1 × 10 m to 3126.5 × 10 m. Also, the gully length increased by 60.55 %, and the area with deposits in the channel bed increased by 134.80 %. A comparison of the SPOT5 images taken on 10 February 2009 (after the '5.12' Wenchuan earthquake) with the WorldView-2 images taken on 26 April 2011 (after the large rainstorm event in August 2011) showed that the landslide area increased by 24.8 % from 3126.5 × 10 m to 3902.8 × 10 m while the gully length increased by 26 % and the channel deposits by 12 %. A comparison of the WorldView-2 images taken on 26 April 2011 with the WorldView-2 images taken on 14 July 2011 indicated that the landslide area increased in this relatively dry period by only 2.3 %. [ABSTRACT FROM AUTHOR]

Laxiwa Hydropower Station is the largest among those hydropower stations in the upper reaches of the Yellow River. The construction started in October 2001, diversion tunnel was finished in January 2004, and impoundment started in March 2009. However, from May 2009, the right-bank slope of the reservoir about 700 m high and 1,000 m wide located 500 m far from the dam was found to be deforming greatly and continuously. Although this slope had been identified as an old landslide, the survey before the construction of the dam concluded that this slope being composed of granite is stable and would be stable even after the impoundment, and thus no detailed monitoring of the slope deformation had been performed before the visible deformation occurred after the impoundment. To indentify the relationship between the deformation of the slope and impoundment, we utilized differential synthetic aperture radar interferometry and Advanced Land Observing Satellite Prism data to analyze the slope deformation before and after impoundment. We found that no identifiable deformation took place before the impoundment, while during the period of 3 April 2009 to 22 May 2010, after impoundment, maximum horizontal displacement reached approximately 7.5 m. This slope is still deforming even after a total horizontal displacement of several tens of meters being reached, showing high risk of catastrophic failure. [ABSTRACT FROM AUTHOR]