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Maoxian Country in Sichuan Province, China is a quake-prone mountainous area. Within 300 km of it, there have been more than ten strong earthquakes higher than Ms6.0 on record. The nearest one is the Diexi Earthquake of 1933, 8.7 km from Maoxian County. A catastrophic scale landslide, the Xinmo landslide, took place on the steep cataclinal slope of Xinmo Village on June 24, 2017. Shear failure happened to the phyllite layer of rich fissures during the landslide. In this paper, shaking table tests have been conducted on the Xinmo landslide as a prototype, and a non-contact deformation measurement based on the digital image correlation (DIC) technique has been made to analyze the dynamic response and deformation of the slope under accumulated seismic actions. As the results, stress amplification is found at the end of joints on the potential slide face. Failure starting from the middle of the potential slide face in the beginning extends upwards and downwards along the face, and leads to a steep tension crack on the top of the slope and a buckling failure of radial-arc cracks at the foot. A semi-steep radial crack in buckling part has a shear failure. The tensile stress amplification on the discontinuous face contributes to the failure accumulation of it and asymptotic failure of the slope. It proposed that the closure and downward displacement of tensile crack on the top of slope, buckling phenomenon at the foot of slope and shear failure of semi-steep crack are all the bad omens of landsliding. [ABSTRACT FROM AUTHOR]

The assessment of earthquake-induced landslide hazards is an important prerequisite for disaster prevention and reduction in tectonic active areas. However, few studies have considered the amplification effect of site and topography on ground motion parameters and made the peak ground acceleration (PGA) correction. Based on Newmark's method, taking Litang County, Sichuan Province, China, as the study area, considering the site amplification effect and topographic amplification effect, this paper carried out the assessment of landslide hazards under the action of occasional earthquakes with an exceedance probability of 10% and rare earthquakes with an exceedance probability of 2%. The results show that the hazard of earthquake-induced landslides is higher in the high slopes of loose rock in the middle of Litang County and the steep rock slopes with large topographic relief in the northeast, and low in the southern plateau and central basins. The site and topographic conditions have a significant effect on the nonlinear amplification of PGA, and the corrected PGA is even magnified by 2–3 times in steep mountains. Compared with the occasional earthquakes, the influence of rare earthquakes on the initiation and movement distance of landslides is remarkably improved. This study can provide a valuable reference for potential earthquake-induced landslide hazard assessment and seismic landslide emergency response in Litang County. [ABSTRACT FROM AUTHOR]

Earthquake-induced landslides are complex dynamic processes, a better understanding of which can be achieved by studying the entire dynamic process, including the propagation of seismic waves, cracking, instability, movement, and deposition. This paper explores the entire dynamic process in combination with the propagation of seismic waves and crack developing process of the slope under earthquake actions, while taking into account the strength attenuation, the major factor that causes the high-speed and long-runout movement. In this study, a simulation analysis tool called discontinuous deformation analysis (DDA) was used and improved by incorporating a seismic input method based on a viscous boundary and the free-field theory, virtual and real joints, and a shear strength attenuation criterion, to conduct a unified simulation analysis of the whole dynamic process of earthquake-induced landslide, and to analyze the influence of the dynamic response law on the instability and motion of landslide. Based on these improvements, the Donghekou landslide caused by the Wenchuan earthquake in 2008 was simulated. The dynamic characteristics of the slope showed an obvious amplification effect. At places with strong dynamic responses, cracks initiated rapidly. The progressive crack developing process of the landslide was represented. Owing to the low-friction effect, the speed increased sharply after the landslide began, promoting its high speed and long runout. From the crack propagation in the slope and the formation process of the sliding surface, it is evident that the Donghekou landslide was a typical tension-cracking and shearing sliding landslide. Highlights: The entire dynamic process analysis landslide method, from continuous to discontinuous, was established. The influence of the site dynamic response to the formation of a landslide was considered. The instability mechanism of a landslide was analyzed based on the fragmentation process. [ABSTRACT FROM AUTHOR]

Moderate-large earthquakes usually trigger a large number of landslides. The prehistoric large landslides can be analyzed to determine the probability of its seismic origin, and further recognized as an indicator of fault activity and earthquake intensity. Based on field investigation, high-resolution satellite image interpretation and cosmogenic exposure dating of landslide deposit, the paper presents a large, long-runout Luanshibao rock avalanche (the LSB rock avalanche), southeast Tibet. The study reveals that (1) the LSB rock avalanche straddles the Litang active strike-slip fault and deposits on the open-flat Quaternary Maoya basin, with a deposit volume of 67 Mm3 and an apparent coefficient of friction of 0.22. (2) Totally, 8 granite blocks from the proximal to the medial part of deposit dated by the Terrestrial Cosmogenic Nuclide method suggests an average 10Be exposure age of 3510 ± 346 a B.P. for the LSB rock avalanche; (3) the spatial-temporal intercutting relationships among the LSB rock avalanche, Quaternary sediments, and the Litang active fault suggest five strong paleoseismic events in the Maoya basin, which is temporally in accordance to the result defined by paleoearthquake-trench research; (4) the corresponding maximum magnitude could reach MW 7.1 ± 0.1 by the empirical equations between landslide volume and earthquake magnitude. It suggests that the Maoya section of Litang fault is probably more dangerous than other sections due to the high density of large co-seismic landslides, which could present useful reference for the alignment selection of future Sichuan-Tibet railway. [ABSTRACT FROM AUTHOR]

The landslide susceptibility assessment based on machine learning can accurately predict the probability of landslides happening in the region. However, there are uncertainties in machine learning applications. In this paper, Artificial Neural Network (ANN), Random Forest (RF), Support Vector Machine (SVM), and Logistic Regression (LR) are used to assess the landslide susceptibility in order to discuss the model uncertainty. The model uncertainty is explained in three ways: landslide susceptibility zoning result, risk area (high and extremely high) statistics, and the area under Receiver Operating Characteristic Curve (ROC). The findings indicate that: (1) Landslides are restricted by influence factors and have the distribution law of relatively concentrated and strip-shaped distribution in space. (2) The percentage of real landslide in risk area is 86%, 87%, 82%, and 61% in SVM, RF, LR, and ANN, respectively. The area under ROC of RF, SVM, LR, and ANN, respectively, is 90.92%, 80.45%, 73.75%, and 71.95%. (3) Compared with the prediction accuracy of the training set and test set from the same earthquake, the accuracy of landslide prediction in the different earthquakes is reduced. [ABSTRACT FROM AUTHOR]

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Discontinuous deformation analysis (DDA) as an efficient technique has been extensively applied in the dynamic simulation of discontinuous rock mass. In the original DDA (ODDA), the Mohr-Coulomb failure criterion is employed as the judgment principle of failure between contact blocks, and the friction coefficient is assumed to be constant in the whole calculation process. However, it has been confirmed by a host of shear tests that the dynamic friction of rock joints degrades. Therefore, the friction coefficient should be gradually reduced during the numerical simulation of an earthquake-induced rockslide. In this paper, based on the experimental results of cyclic shear tests on limestone joints, exponential regression formulas are fitted for dynamic friction degradation, which is a function of the relative velocity, the amplitude of cyclic shear displacement and the number of its cycles between blocks with an edge-to-edge contact. Then, an improved DDA (IDDA) is developed by implementing the fitting regression formulas and a modified removing technique of joint cohesion, in which the cohesion is removed once the 'sliding' or 'open' state between blocks appears for the first time, into the ODDA. The IDDA is first validated by comparing with the theoretical solutions of the kinematic behaviors of a sliding block on an inclined plane under dynamic loading. Then, the program is applied to model the Donghekou landslide triggered by the 2008 Wenchuan earthquake in China. The simulation results demonstrate that the dynamic friction degradation of joints has great influences on the runout and velocity of sliding mass. Moreover, the friction coefficient possesses higher impact than the cohesion of joints on the kinematic behaviors of the sliding mass. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The 2016 Kumamoto earthquake first occurred on April 14, 2016 with magnitude 6.5 in Kumamoto, Japan as a foreshock. Subsequently, after 28 h, an even larger earthquake occurred with magnitude 7.3 as the main shock on April 16, 2016. These earthquakes were caused by two active faults: the Futagawa and Hinagu faults. This paper proposes a landslide susceptibility calculation method that considers the geomaterial strength reduction from peak to residual state and ground motion directivity. Although there is a lack of information regarding the strength parameters of geomaterials in the slopes, a parametric analysis with various strength parameters of friction angle and cohesion was carried out. To simulate the actual landslides triggered by the 2016 Kumamoto earthquake, the best combination of friction angle and cohesion in each lithology was optimized by a proposed weighted prediction rate. Based on the calculated permanent seismic displacement, a landslide susceptibility map was produced to show the degree of susceptibility over a wide area comprising 100 km2. The proposed regional landslide susceptibility map will be valuable for estimating the locations of possible slope failures and the extent of damage, as well as for planning field reconnaissance and preventing secondary disasters immediately after earthquakes. [ABSTRACT FROM AUTHOR]

Sliding of natural and artificial slopes generally occurs during or following strong earthquakes. Such sliding is greatly affected by a combination of geological conditions and earthquake loading. Earthquake-induced landslides often cause more damage to infrastructure and human lives than the earthquake itself. Pseudo-static analysis is widely implemented as one of several design methods used in engineering practice to assess the seismic stability of natural and artificial slopes. However, the most important issue of pseudo-static analysis is to select the most appropriate method for measuring seismic coefficient. In order to investigate this, back analysis was conducted for surficial slides subjected to strong ground motion during the 2004 Mid-Niigata prefecture earthquake in Japan. This paper surveyed the stochastic properties of earthquake-induced surficial slides and clearly showed that the obtained results were applicable to back analysis of shear strength and seismic coefficient. In back analysis, soil properties such as soil strength and density and sliding depth were assumed as random variables owing to their uncertainties. Seismic coefficient is also assumed to be a random variable and varies with distance from the epicenter fault line. The analysis of 4504 recorded surficial slides clearly shows a unique relationship of landslide occurrence ratio with slope angle and distance from the epicenter fault line. This study’s results enhance the calculation of the shear strength of weathered soil covering slopes and the horizontal seismic coefficient through back analysis procedure. By considering possible stochastic properties of variables, some case studies were implemented in the back analysis. [ABSTRACT FROM AUTHOR]

The Nilgiris district in the Tamilnadu state of India is frequented by many landslides in the recent past. Though many of these landslides are rainfall-induced, there is a need to evaluate the potential of earthquake-induced landslides considering seismicity of the region. In this paper, deterministic seismic hazard of Nilgiris is carried out by considering a study area of 350 km radius around Nilgiris. Seismotectonic map of the Nilgiris, showing the details of faults and past earthquakes, is prepared. The peak ground acceleration (PGA) at bed rock level and response spectrum are evaluated. The potential sources for Nilgiris are Moyar and Bhavani shears. The PGA at bed rock level is 0.156 g corresponding to maximum considered earthquake 6.8. Ground response analysis for seven sites, in the Nilgiris, is carried out by one-dimensional equivalent linear method using SHAKE program after considering the effect of topography. PGA of surface motion got amplified to 0.64 g in Coonoor site and 0.44 g in Ooty site compared to 0.39 g of the input motion. The bracketed duration of time history of surface acceleration has increased to 20 s in Coonoor site and 18 s in Ooty site compared to that of 8 s of input motion. Results from seismic displacement analysis using Newmark's method revealed that out of seven sites investigated, five sites have moderate seismic landslide hazard and two sites (Coonoor and Ooty) have high hazard. [ABSTRACT FROM AUTHOR]

This paper studies the run-out of earthquake-induced landslides. There are more than 20 mechanical models to explain long run-out of rapid landslides including some earthquake-induced landslides. However, notably few of them considered the effect of seismic loading on the run-out of landslides. In a previous study, we have proposed a model, which is called the multiplex acceleration model (MAM), to interpret the long run-out mechanism, and a shaking-table test has been performed to verify the MAM. Because the previous MAM is a conceptual model and only a single stone has been examined under sine waves by the shaking-table test, the MAM needs to be extended and further verified. In this paper, the MAM was extended by introducing the movement change that was induced by the so-called trampoline effect of earthquake loading, and the latest practical numerical simulation program, discontinuous deformation analysis (DDA), was used to verify the mobility of earthquake-induced landslides. After a conceptual landslide model was used to verify the effect of seismic loading on the mobility, the Donghekou landslide, which was a typical long run-out landslide that was induced by the 2008 Wenchuan earthquake, was analyzed. The results show that: the seismic loading could be one of the factors that could eventually help increase the run-out of landslides. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for evaluating the safety of slopes threatened by strong earthquakes. Based on the theory of modal analysis, the proposed approach analyzes the seismic landslide spectrum, including the calculation of the landslide intrinsic frequency and the investigation of the resonance effect. The concept and the solution of the resonance index (RI) of the seismic landslide are also proposed. By using the VC++ computer language, corresponding dynamic finite element program, namely Analysis of Seismic Landslide Spectrum (ASLS), is developed. To verify the proposed method, three examples are presented: a fixed-end beam, a specially designed landslide vibration experiment, and the largest landslide triggered by the 2008 Wenchuan earthquake. The obtained numerical and experimental results show that the proposed method can effectively evaluate the safety of seismic landslides. It is suggested that the resonance phenomenon of landslides should be considered in the landslide treatment and the seismic design. [ABSTRACT FROM AUTHOR]

The 2004 Chuetsu earthquakes of Niigata (Japan) triggered numerous landslides, and the most widespread types of landslides were highly disrupted, relatively shallow slides and soil (debris) flows. This paper presented a method to evaluate slope instability using Newmark displacement on a pixel-by-pixel basis in a given area. The proposed method was able to integrate Newmark displacement modeling and Monte Carlo simulations within geographical information systems. In the modeling, an empirical attenuation relationship was utilized to calculate Arias intensity over this study area, and the variability of geotechnical parameters was taken into account to calculate coseismic landslide displacement. Before deriving the displacement from related inputs, the Monte Carlo simulations ran 1,500 times and generated 1,500 displacement values for each grid cell, and then means and standard deviations of displacement were calculated and probabilistic distributions can be obtained. Finally, given 10 cm as a threshold value of displacement, estimated probabilities of displacement exceeding 10 cm were shown as a map of seismic landslide hazards. The resulting hazard map was classified into four categories from very low to high level. [ABSTRACT FROM AUTHOR]

A catastrophic Palu earthquake on September 28th, 2018 with Mw 7.5 triggered countless slope failures, generating numerous landslides. This paper presents a practical method for susceptibility assessment of earthquake-induced landslides in the Palu region and the surrounding area. The statistical weight of evidence (WoE) model was used to assess the relationship between landslides induced by seismic motion and its causative factors to determine the susceptibility level and derive an earthquake-induced landslide susceptibility map of this study area. The 1273 landslides were classified into two data series, training data for modelling (70%) and test data for validation (30%). The six selected thematic maps as landslide causative factors are lithology, land use, peak ground acceleration (PGA), and slope (gradient, aspect, elevation). The selection of causative factors considerably influences the frequency of landslides in the area. The result is satisfactory because the AUC value of the chosen model excelled the minimum limit, which is 0.6 (60%). The estimated success rate of the model is 85.7%, which shows that the relevancy of the model is good with the occurrence of landslides. The prediction rate of 84.6% indicates that the applied model is very good at predicting new landslides.

Soil-rock mixed accumulation bodies produced by rainfall, earthquake or early landslides tend to have unconsolidated structure and poor stability, and are prone to failure under the rainfall or earthquake. The Jiuzhaigou earthquake occurred in China on August 8, 2017, caused a lot of soil-rock mixed accumulation bodies on the slope, which seriously threatened the safety of people's lives and property. Earthquakes occur frequently in this area, so it is very important to analyze the instability and movement characteristics of the soil-rock mixed accumulation bodies under earthquake. In order to overcome the shortcomings of single numerical simulation method in simulating large-scale landslide, the discrete–continuous coupled approach is adopted, in which the discrete and continuous models are established to simulate the bedrock and sliding accumulation body, respectively. The results show that it is suitable for simulating the earthquake-induced accumulation body sliding movement. Under the seismic signal, cracks firstly appear in the back edge of the upper accumulation body, and then, the collapse occurs. The sliding body pushes the lower accumulation body to be unsteady and sliding, and finally, the sliding body accumulates at the foot of the slope. The average velocity and displacement of the rock blocks are greater than that of the soil during the movement. [ABSTRACT FROM AUTHOR]

Arias intensity is an essential ground motion measure correlating with the potential for earthquake-induced landslides. The Sichuan–Yunnan region, which is primarily mountainous, is a high incidence region of earthquake-induced landslides in China. However, there is no available attenuation relationship for this intensity measure due to the backward construction of the stations. In this study, we developed a region-specific Arias intensity attenuation relationship using the China Strong-Motion Networks Center (CSMNC) database which was established in 2008. We recommend this relationship be applied in the Sichuan–Yunnan region for moment magnitudes ranging between 4.2 and 7.0, distances ranging between 0 and 300 km and with Vs30 (the average shear-wave velocity in the upper 30 m of a soil profile) ranging between 128 and 760 m/s. The current study finds that this relationship's intra-event, inter-event, and total standard deviations are greater than for other regions. This is likely caused by the complicated seismotectonic activities, nonlinear site effects, error from inferring Vs30, basin effects, etc. However, this relationship has the best performance in fitting and predicting the data from the Sichuan–Yunnan region. [ABSTRACT FROM AUTHOR]

The distinctive bathymetric feature exists in the Suruga Bay, Japan. It has been called as Senoumi (Stone flower sea) from old times. Senoumi is a 30 km wide and 20 km long concave feature. Its origin has not been explained yet; however, the feature might be a combined consequence of intensive tectonic activity in the plate border, landslides, and a submarine flow coming from the Oi River. If the Senoumi was caused by a landslide, the latter would be larger than any on-land landslide in Japan. The downshelf 'exit' from this feature is much narrower than its central part. This is not usual shape of landslides, but it is similar to the liquefied landslides such as those in quick clays which mobilize great strength reduction after failure. To study Senoumi as a landslide, the shear behaviors of the following three soil samples were investigated by the cyclic and seismic undrained stress control ring shear tests. One sample is volcanic ash taken from the base of landslide deposits (mass transport deposits), from 130 to 190 m deep layer below the submarine floor which was drilled and cored by the Integrated Ocean Drilling Program Expedition 333. Another two samples are the Neogene silty-sand and silt taken from the Omaezaki hill adjacent to the Senoumi, because the shear zone might have been formed in Neogene layers extending from on-land to the continental shelf. The largest strength reduction from peak to steady-state shear resistance in the undrained cyclic loading test was found in volcanic ash. The strength reduction in Neogene silty-sand was smaller than volcanic ash, while the Neogene silt mobilized the least post-failure strength reduction. An integrated model simulating the initiation and motion of earthquake-induced rapid landslides (landslide simulation (LS)-RAPID, Sassa et al. Landslides 7-3:219-236, ) was applied to this study. The steady-state shear resistance and other geotechnical parameters measured by the undrained ring shear tests and the greatest strong motion record in the 2011 off-the-Pacific Coast of Tohoku earthquake ( M 9.0), also known as '2011 Tohoku Earthquake' at the observation point MYG004 (2,933 gal) were input to this model. As the result, it was found that landslides would be triggered by 0.30-1.0 times of MYG004 in volcanic ash, 0.4-1.0 times of MYG004 in Neogene silty-sand and Neogene silt, though the depth and area of triggered landslides were different in soils and intensity of shaking. Feature, created by LS-RAPID using the parameters of volcanic ash, was most similar to the Senoumi in depth and extent. The result obtained from this study includes a hypothesis to be proved, but presents the strong need to investigate the risk of the large-scale submarine landslides which could enhance tsunami wave and possibly enlarge the submarine landslide retrogressively into the adjacent coastal plain by the upcoming mega earthquake in the Nankai Trough. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the preliminary results of an extensive study of the mapping the distribution of landslides triggered by the Wenchuan earthquake in Sichuan Province, China, on 12 May 2008. An extensive landslide interpretation was carried out using a large set of optical high resolution satellite images (e.g. ASTER, ALOS, Cartosat-1, SPOT-5 and IKONOS) as well as air photos for both the pre- and post-earthquake situation. Landslide scarps were mapped as points using multi-temporal visual image interpretation taking into account shape, tone, texture, pattern, elevation and ridge and valley orientation. Nearly 60,000 individual landslide scarps were mapped. The landslide distribution map was compared with the inventory map that was prepared directly after the earthquake, which contains about 11,000 individual landslide points, through the calculation of normalized landslide isopleths maps. Remarkable differences were observed, as the earlier inventory mapping did not consider the pre-earthquake situation and did not consider all individual landslides. As part of the landslide inventory, landslides were identified that had blocked the drainage and had formed landslide dams. The landslide distribution was compared with a number of aspects, such as the seismic parameters (distance to epicenter, distance to fault rupture, co-seismic fault geometry and co-seismic slip distribution), and geology. The most remarkable correlation found was with the co-seismic slip distribution and the fault geometry. Landslide distribution in the section of the fault that had mainly a thrust component with low angle fault plane was found to be much higher than the sections that had steeper fault angles and a major strike slip component. [Copyright &y& Elsevier]

Earthquakes induce landslides worldwide every year that may cause massive fatalities and financial losses. Precise and timely landslide susceptibility mapping (LSM) is significant for landslide hazard assessment and mitigation in earthquake-affected areas. State-of-the-art LSM approaches connect causative factors from various sources without considering the fusion of different information at the data modal level. To exploit the complementary information of different modalities and boost LSM accuracy, this study presents a new LSM model that integrates data modality and machine learning methods. The presented method first groups causative factors into different modal types based on their intrinsic characteristics, followed by the calculation of the pairwise similarity of modal data. The similarities of different modalities are fused using nonlinear graph fusion to generate a unified graph, which is subsequently classified using different machine learning methods to produce final LSM. Experimental results suggest that the presented method achieves higher performance than existing LSM methods. This study provides a new solution for producing precise LSM from a fusion perspective that can be applied to minimize the potential landslide risk and for sustainable use of erosion-prone slopes. [ABSTRACT FROM AUTHOR]

The main objective of this study is to understand the overall impact of earthquake in upper Indrawati Watershed, located in the high mountainous region of Nepal. Hence, we have assessed the relationship between the co-seismic landslide and underlying causative factors as well as performed landslide susceptibility mapping (LSM) to identify the landslide susceptible zone in the study area. We assessed the landslides distribution in terms of density, number, and area within 85 classes of 13 causal factors including slope, aspect, elevation, formation, land cover, distance to road and river, soil type, total curvature, seismic intensity, topographic wetness index, distance to fault, and flow accumulation. The earthquake-induced landslide is clustered in Northern region of the study area, which is dominated by steep rocky slope, forested land, and low human density. Among the causal factors, 'slope' showed positive correlation for landslide occurrence. Increase in slope in the study area also escalates the landslide distribution, with highest density at 43%, landslide number at 4.34/km2, and landslide area abundance at 2.97% in a slope class (> 50°). We used logistic regression (LR) for LSM integrating with geographic information system. LR analysis depicts that land cover is the best predictor followed by slope and distance to fault with higher positive coefficient values. LSM was validated by assessing the correctly classified landslides under susceptibility categories using area under curve (AUC) and seed cell area index (SCAI). The LSM approach showed good accuracy with respective AUC values for success rate and prediction rate of 0.843 and 0.832. Similarly, the decreasing SCAI value from very low to very high susceptibility categories advise satisfactory accuracy of the LSM approach. [ABSTRACT FROM AUTHOR]

Major earthquakes in steep orogens can trigger extensive landsliding. Most of the landslide bodies come to rest high on the slopes, but subsequent rainfalls can easily remobilize them. Sharp peaks in landslide rates are systematically observed after major earthquakes, followed by rapid decays to background levels in just several years. Yet, the migration of coseismic debris into tributary channels and rivers remains poorly understood. We collected 12 years of observations of the 2008 Wenchuan earthquake's epicentral region in China and evaluated that debris flows and fluvial transport could only evacuate a small portion of coseismic debris, while over 70% of it had stabilized on the hillslopes. Coseismic debris may remain in the orogen for a long time, but estimates based on initial landslide abundance and sediment export are hampered by uncertainties in the debris fate throughout the earthquake cycle. Plain Language Summary: Strong earthquakes leave a trail of destruction that lasts much longer than the dramatic minutes of strong ground motion. Earthquakes shake the mountains, causing extensive landsliding that delivers huge amounts of debris along the slopes and in drainage channels. This debris is loose and unconsolidated, prone to generating subsequent landslides and debris flows. We have monitored the epicentral area of the magnitude 7.9 Wenchuan Earthquake (2008, China) for 12 years to study the evolution of landslide activity in space, time, and characteristics, and track the fate of the debris from the slopes into channels and rivers. We found that the landslide rates have decreased rapidly. After 10 years, they were already comparable to the pre‐earthquake levels. Most of the debris remained on the slopes, though: it stabilized and never moved again. At current rates, the removal of the earthquake‐generated debris from the landscape through landsliding may take a long time. Key Points: Despite large amounts of erodible coseismic debris, post‐seismic landslide rates decayed to pre‐earthquake levels in less than a decadeOnly a small proportion of debris has left the orogen so far: over 70% of it has stabilized in place, along the hillslopesWith erosion proceeding at this pace, a residence time of several centuries for the debris can be expected [ABSTRACT FROM AUTHOR]

The landslide susceptibility assessment based on machine learning can accurately predict the probability of landslides happening in the region. However, there are uncertainties in machine learning applications. In this paper, Artificial Neural Network (ANN), Random Forest (RF), Support Vector Machine (SVM), and Logistic Regression (LR) are used to assess the landslide susceptibility in order to discuss the model uncertainty. The model uncertainty is explained in three ways: landslide susceptibility zoning result, risk area (high and extremely high) statistics, and the area under Receiver Operating Characteristic Curve (ROC). The findings indicate that: (1) Landslides are restricted by influence factors and have the distribution law of relatively concentrated and strip-shaped distribution in space. (2) The percentage of real landslide in risk area is 86%, 87%, 82%, and 61% in SVM, RF, LR, and ANN, respectively. The area under ROC of RF, SVM, LR, and ANN, respectively, is 90.92%, 80.45%, 73.75%, and 71.95%. (3) Compared with the prediction accuracy of the training set and test set from the same earthquake, the accuracy of landslide prediction in the different earthquakes is reduced.

Aiming to understand the dynamic disintegration and transport behavior of an earthquake-induced landslide, a dynamic discrete element method has been employed to analyze the Wangjiayan landslide triggered by the 2008 Ms 8.0 Wenchuan earthquake. Absorbing boundary condition is used for the seismic wave transmission and reflection at the slope base. The numerical results show that under seismic loading, internal rock damage initiates, propagates, and coalesces progressively along the weak solid structure and subsequently leads to fragmentation and pulverization of the slope mass. This can be quantitatively interpreted with the continuously rapid increase of the damage ratio and sudden decline of growth ratio of the number of fragments after the peak seismic shaking. During emplacement evolution, fragmented deformation patterns within the translating joint-defined granular assemblies are affected by the locally high dilatancy with a simultaneous occurrence of highly energetic collisions related to the action of shearing, and this can be quantified by the enhancement of particle kinematic activities (high vibrational and rotational granular temperatures) and intense fluctuations of location-dependent global dispersive stress. In this process, slope destabilized and transports downward in a rapid pulsing motion as friction bonds are locally and continually overcome by the seismic- and gravity-induced shear forces. The joint-determined fragment network before movement initiation and the final fragmented depositions after the rapidly sheared transport have been systematically investigated by fragment statistics (fragment size distribution, fragment mass distribution, and fractal dimension) and morphometric characters (fragment shape isotropy) to offer new insights into the disintegration characteristics of the earthquake-induced catastrophic mass movements. [ABSTRACT FROM AUTHOR]

An earthquake with Ms 7.0 (33.2° N, 103.8° E) occurred in Jiuzhaigou County of Sichuan Province in China on 8 August 2017. This earthquake triggered a large number of landslides in the study area. Although the susceptibility quality level index has improved, the high-quality assessments still have remained rare. We adopted three models, including the logistic regression (LR), support vector machine (SVM), and random forest (RF) to study the quality performance of the susceptibility distribution rule of earthquakes induced landslides. We used satellite images of before and after earthquakes and landslides as well. We used the area under receiver operating characteristic (ROC) curve (AUC) and ratio to evaluate the model's accuracy and quality performance, including the mapping availability susceptibility assessment. This study reveals that RF has the highest ratio (2.07) as compared to the LR (1.78) and SVM (1.90). The result shows that RF has more potential to implement future experiments in Sichuan Province because of a better performance quality in the susceptibility assessment of landslides induced by earthquakes. [ABSTRACT FROM AUTHOR]

Landslides induced due to monsoon rainfall and earthquakes are very common phenomena in Uttarakhand Himalayas of India. For example, many such landslides got induced and reactivated by the 1999 Chamoli earthquake. In view of above, authors have made an attempt to prepare pre- and post-earthquake landslide susceptibility zonation (LSZ) maps for a part of Chamoli district, Uttarakhand, India. The novelty of this work lies in producing an LSZ map considering peak ground acceleration (PGA) as one of the controlling factors for earthquake-induced landslide occurrences and validating the LSZ map with the post-earthquake landslide inventory. For this purpose, a spatial database of seven controlling factors, i.e., slope angle, slope aspect, slope curvature, geology, distance to drainage, normalized difference vegetation index (NDVI) and peak ground acceleration (PGA) was prepared in Geographic Information System (GIS). Then, relative frequency ratio (RFR) method was adopted for the LSZ maps. The landslide inventory of 276 landslides (220 pre-earthquake and 56 post-earthquake landslides) was prepared for the study area. Firstly, an LSZ map was generated using six controlling factors excluding PGA and the pre-earthquake landslide inventory (Case I). In another attempt, the LSZ map is prepared using seven controlling factors including PGA and pre-earthquake landslide inventory to examine the influence of seismic parameter (PGA) in landslide susceptibility assessment (Case II). Subsequently, pre- and post-earthquake landslide inventory along with seven controlling factors were used to construct another LSZ map (Case III). Finally, these three LSZ maps were validated and compared with the training and testing data. In this study, a spatial predictive model for earthquake-induced landslide is developed. [ABSTRACT FROM AUTHOR]

Many large-scale landslides have occurred along the Dadu River, in particular in the middle section of the river, located on the eastern edge of the Qinghai–Tibet Plateau. The large-scale Lantianwan landslide was triggered by the 1786 Moxi earthquake (Ms = 7.75) at Luding, Sichuan province, China. Field investigations and 3D discrete element methods were used to examine the landslide formation mechanism and simulate landslide movement. The evolution of the landslide can be divided into four stages: initiation, high-speed motion, debris flow, and accumulation and river blocking. The results indicate that tension cracking and horizontal sliding were the geological origins of the Lantianwan landslide. The Moxi earthquake combined with the magnifying effect of the topography and the back slope formed deep-dip tensile structural planes in the Lantianwan slope, which triggered the landslide. [ABSTRACT FROM AUTHOR]

In 2016, earthquakes occurred beneath Kumamoto City, Kumamoto Prefecture in the Kyushu Region of Japan and generated numerous landslides around the city, and among those triggered in this disastrous event, the Aso-Bridge landslide was the largest. For the purpose of examining the behavior of this large-scale landslide during the main shock of the Kumamoto earthquakes, we conducted a study involving simplified sliding block concepts and finite element codes, and conclude that (a) the slope of the Aso-Bridge landslide (about 710 m high and with a dip angle of 33 °) is marginally stable in the absence of earthquakes; (b) the failure surface obtained using finite element codes is in satisfactory agreement with that of the actual failure surface; ©) our results reveal that the initiation-time of the Aso-Bridge landslide lay between 18.45 and 21 s based on three indications: (I) the directional tendency of the first apparent displacement, (ii) evidential factor of safety (FS) values <1, and (iii) Newmark’s displacement; and (d) the combination of an internal friction angle of 35 ° and a cohesion value of 80 kPa led to a failure surface closest to that observed in the field. The study demonstrates that we were able to apply the simplified sliding concepts and finite element codes to analyze the Aso-Bridge landslide in reasonable agreement with the actual event. [ABSTRACT FROM AUTHOR]

The Lamuajue landslide is located in Lamuajue village on the right bank of the Meigu River, Sichuan Province, China. This landslide is an ancient landslide with an extremely wide distribution area, covering an area of 19 km with a maximum width of 5.5 km and an estimated residual volume of 3×10 m. The objectives of this study were to identify the characteristics and failure mechanism of this landslide. In this study, based on field investigations, aerial photography, and profile surveys, the boundary, lithology, structure of the strata, and characteristics of the landslide deposits were determined. A gently angled weak interlayer consisting of shale was the main factor contributing to the occurrence of the Lamuajue landslide. The deposition area can be divided into three zones: zone A is an avalanche deposition area mainly composed of blocks, fragments, and debris with diameters ranging from 0.1 m to 3 m; zone B is a residual integrated rock mass deposition area with large blocks, boulders and 'fake bedrock'; and zone C is a deposition zone of limestone blocks and fragments. Three types of failure mechanism were analyzed and combined to explain the Lamuajue landslide based on the features of the accumulation area. First, a shattering-sliding mechanism caused by earthquakes in zone A. Second, a sliding mechanism along the weak intercalation caused by gravity and water in zone B. Third, a shattering-ejection mechanism generated by earthquakes in zone C. The results provide a distinctive case for the study of gigantic landslides induced by earthquakes, which is very important for understanding and assessing ancient earthquakeinduced landslides. [ABSTRACT FROM AUTHOR]

Landslides along active fault zones are important hazards during and after earthquakes. They can also cause secondary disasters such as surges, creation of landslide dams, and flooding, especially in reservoir areas. This study analyzed landslide susceptibility of the Xiangjiaba Reservoir area associated with the Yaziba Fault. Analysis of permanent displacement and failure probabilities were used for the regional assessment. Ground motion attenuation relations were selected and compared to produce a peak acceleration map using the Yaziba Fault as the seismic source. Geotechnical parameters were determined by classification of rock groups and geomorphic data were calculated using GIS tools. A distribution of the permanent displacements and a failure probability map was generated. According to the peak ground acceleration (PGA) map, the C-B model was adopted to present the actual conditions of PGA in greater detail while local specific models are more appropriate if there is little measured data. Results indicated larger displacement values and failures are distributed on both sides of the fault, especially in the hanging wall. The feasibility of the research approach was verified using historic earthquake-induced landslides. [ABSTRACT FROM AUTHOR]

The PARSIFAL (Probabilistic Approach to pRovide Scenarios of earthquake-Induced slope FAiLures) approach was applied in the basin of Alcoy (Alicante, South Spain), to provide a comprehensive scenario of earthquake-induced landslides. The basin of Alcoy is well known for several historical landslides, mainly represented by earth-slides, that involve urban settlement as well as infrastructures (i.e., roads, bridges). The PARSIFAL overcomes several limits existing in other approaches, allowing the concomitant analyses of: (i) first-time landslides (due to both rock-slope failures and shallow earth-slides) and reactivations of existing landslides; (ii) slope stability analyses of different failure mechanisms; (iii) comprehensive mapping of earthquake-induced landslide scenarios in terms of exceedance probability of critical threshold values of co-seismic displacements. Geotechnical data were used to constrain the slope stability analysis, while specific field surveys were carried out to measure jointing and strength conditions of rock masses and to inventory already existing landslides. GIS-based susceptibility analyses were performed to assess the proneness to shallow earth-slides as well as to verify kinematic compatibility to planar or wedge rock-slides and to topples. The experienced application of PARSIFAL to the Alcoy basin: (i) confirms the suitability of the approach at a municipality scale, (ii) outputs the main role of saturation in conditioning slope instabilities in this case study, (iii) demonstrates the reliability of the obtained results respect to the historical data. [ABSTRACT FROM AUTHOR]

This study proposes a calculation method for regional earthquake-induced landslide susceptibility that applies the permanent seismic displacement calculated using Newmark's sliding block analysis with estimated vertical and horizontal seismic motions. The proposed method takes into account the direction of slope failure based on the specified slope azimuth. The study results reveal the importance of predominant slope failure direction using a simple infinite slope model subjected to earthquakes. The target area for the earthquake-induced landslide susceptibility analysis constituted a region of more than 2000 km surrounding the epicenter of the Mid Niigata prefecture earthquake in 2004. An earthquake-induced landslide susceptibility map was created based on the proposed method with a specific combination of friction angle and cohesion, and the resulting data were compared to the landslide inventory map produced from aerial photographs following the Mid Niigata prefecture earthquake in 2004. To create the susceptibility map, geomaterial cohesion values for the slope were back-calculated to satisfy the minimum safety factor in the static state. This study also proposes a calculation method for the prediction rate and determines the back-calculated strength parameters of geomaterials. The proposed regional landslide susceptibility map will be useful for understanding potential slope failure locations and magnitude of damage, as well as for planning field investigation and preventing secondary disasters immediately after earthquakes. [ABSTRACT FROM AUTHOR]

In mountainous areas of Asia, huge earthquakes have triggered numerous landslides in recent decades. Estimating the susceptibility of slopes to landslide and the volume of potential landslide debris helps in planning for disaster risk management. We developed a new index to measure the susceptibility of slopes to earthquake-induced landslides by using helicopter-borne electromagnetic resistivity (HEM) survey data to quantify the looseness of bedrock and a digital elevation model to quantify the amplification of seismic waves by topography. In our study area around the Kanagi landslide (triggered by the 1707 Hoei earthquake), our new index showed that landslide susceptibility was low within the area of past landslides, but was higher in areas outside the scar of past landslides. Our results indicate that most of the loosened rock masses have been removed by past landslides, and the areas beyond the main landslide scar, where loosened bedrock remains, are now most susceptible to future earthquake-induced landslides. Our results indicate that this index may be effective in areas susceptible to landslides due to toppling failure and rock avalanches in loosened bedrock slopes. [ABSTRACT FROM AUTHOR]

Earthquake-induced deep-seated landslides are prone to occur at gravitationally deformed and loosened slopes. These slopes need to be identified for landslide susceptibility mapping and landslide risk assessment. Surface morphology is an effective factor for finding the slopes, but is not effective for estimating the degree and the area of loosening. Subsurface geophysical investigations are quite useful for determining subsurface geological structures in regions where loosening has occurred. In this study, a method was developed for regionally mapping gravitationally deformed and loosened slopes as earthquake-induced deep-seated landslide susceptible zones by differentiating from sound bedrocks in flexural toppled slopes. Using the helicopter-borne electromagnetic resistivity data, 'average ruggedness of resistivity' was proposed as an index parameter for differentiating the loosened zones. The estimated loosened zones were compared with observed geomorphological features during field survey, and it is shown that 'average ruggedness of resistivity' is a useful parameter for regional mapping of earthquake-induced deep-seated landslide susceptible slopes. [ABSTRACT FROM AUTHOR]

A 12 million of m translational rockslide developed on a dip slope underlain by limestone with interlayered marls, and responsible for the destruction of the Montclús village in the fourteenth century, has been investigated by means of geomorphological and geophysical surveys. The combination of historical-geoarcheological, geomorphological, seismic refraction and electrical resistivity imaging datasets allowed the (1) reconstruction of the late Quaternary episodic evolution of the landslide, (2) characterization of the geometry and internal structure of the slid mass and (3) identification of preferential groundwater flow paths that favoured slope instability. The development of the landslide involved at least two different displacement episodes controlled by sliding surfaces at successively deeper stratigraphic positions. The first landsliding event, recorded by highly weathered landslide deposits situated above a perched failure plane, occurred approximately during the global Last Glacial Maximum (23-19 ka BP). The most recent event, which destroyed the Montclús village built on already slid rocks, is placed in the fourteenth century. Most probably, this reactivation event was triggered by the 1373 Ribagorza earthquake, with an estimated moment magnitude of M 6.2. This work illustrates the benefits of combining geomorphological data with complementary geophysical technics in landslide investigation. [ABSTRACT FROM AUTHOR]

An earthquake-induced landslide (EQIL) is a rapidly changing process occurring at the Earth's surface that is strongly controlled by the earthquake in question and predisposing conditions. Predicting locations prone to EQILs on a large scale is significant for managing rescue operations and disaster mitigation. We propose a deep learning framework while considering the source area feature of EQIL to model the complex relationship and enhance spatial prediction accuracy. Initially, we used high-resolution remote sensing images and a digital elevation model (DEM) to extract the source area of an EQIL. Then, 14 controlling factors were input to a stacked autoencoder (SAE) to search for robust features by sparse optimization, and the classifier took advantage of high-level abstract features to identify the EQIL spatially. Finally, the EQIL inventory collected from the Wenchuan earthquake was used to validate the proposed model. The results show that the proposed method significantly outperformed conventional methods, achieving an overall accuracy (OA) of 91.88%, while logistic regression (LR), support vector machine (SVM), and random forest (RF) achieved 80.75%, 82.22%, and 84.16%, respectively. Meanwhile, this study reveals that shallow machine learning models only take advantage of significant factors for EQIL prediction, but deep learning models can extract more effective information related to EQIL distribution from low-value density data, which is why its prediction accuracy is growing with increasing input factors. There is hope that new knowledge of EQILs can be represented by high-level abstract features extracted by hidden layers of the deep learning model, which are typically acquired by statistical methods. [ABSTRACT FROM AUTHOR]