Characteristics and numerical runout modeling of the heavy rainfall-induced catastrophic landslide–debris flow at Sanxicun,Dujiangyan, China,following the Wenchuan Ms 8.0 earthquake

The 2008 Ms 8.0 Wenchuan earthquake triggered a large number of extensive landslides. It also affected geologic properties of the mountains such that large-scale landslides followed the earthquake, resulting in the formation of a disaster chain. On 10 July 2013, a catastrophic landslide–debris flow suddenly occurred in the Dujiangyan area of Sichuan Province in southeast China. This caused the deaths of 166 people and the burying or damage of 11 buildings along the runout path. The landslide involved the failure of ≈1.47 million m³, and the displaced material from the source area was ≈0.3 million m³. This landslide displayed shear failure at a high level under the effects of a rainstorm, which impacted and scraped an accumulated layer underneath and a heavily weathered rock layer during the release of potential and kinetic energies. The landslide body entrained a large volume of surface residual diluvial soil, and then moved downstream along a gully to produce a debris flow disaster. This was determined to be a typical landslide–debris flow disaster type. The runout of displaced material had a horizontal extent of 1200 m and a vertical extent of 400 m. This was equivalent to the angle of reach (fahrböschung angle) of 19° and covered an area of 0.2 km². The background and motion of the landslide are described in this study. On the basis of the above analysis, dynamic simulation software (DAN3D) and rheological models were used to simulate the runout behavior of the displaced landslide materials in order to provide information for the hazard zonation of similar types of potential landslide–debris flows in southeast China following the Wenchuan earthquake. The simulation results of the Sanxicun landslide revealed that the frictional model had the best performance for the source area, while the Voellmy model was most suitable for the scraping and accumulation areas. The simulations estimated that the motion could last for ≈70 s, with a maximum speed of 47.7 m/s.     

Susceptibility assessment of the precursor stage of a landslide threatening Haivan Railway Station,Vietnam

Haivan Station is an important station on the North-South railway line in central Vietnam. Field investigation has identified a precursor stage of a landslide that would threaten this railway. Therefore, a landslide susceptibility assessment for Haivan Station was urgently needed to protect passenger safety and the national railway. Conducted investigations included air-photo interpretation, drilling, ground water and inclinometer monitoring, laboratory testing, and landslide simulation. This research applied the undrained dynamic loading ring shear apparatus ICL-2 to drill-core samples from the precursor landslide. Samples for ring shear tests were taken from sandy soil layers found at depths of ~21, ~31, and ~50 m in the cores. Each of these was believed to be a possible sliding surface of a landslide, and all were tested to shear failure in the ICL-2 apparatus. The boundary between highly weathered granitic rock and weathered granitic rock was identified at about 50 m depth. The inclinometer monitoring detected slight movement at this depth. Therefore, the present day risk of a landslide forming at 50 m is higher than for one forming at either 21 or 31 m. The landslide dynamic parameters obtained from the ring shear test of the 50-m-deep sample were used in an integrated numerical simulation model LS-RAPID. The simulation result gave the critical pore-pressure ratio for landslide occurrence, and landslide’s likely maximum speed, total volume, and depth of landslide debris that could cover the railway. These estimates serve to raise awareness of the vulnerability of the Vietnam national railway sector to landslide impact.     

Application of large-scale ring shear tests to the analysis of tsunamigenic landslides at the Stromboli volcano, Italy

The island of Stromboli (Southern Italy) is a 4,000-m-high volcanic edifice about 900 m above sea level. Most of the NW flank is formed by a wide scar (Sciara del Fuoco) filled by irregular alternations of volcaniclastic layers and thin lava flows. Between 29 and 30 December 2002, a submarine and a subaerial landslide involved the northernmost part of the Sciara del Fuoco slope and caused two tsunami waves with a maximum run-up of 10 m. Mechanisms of the rapid submarine landslide and the preceding deformation of the subaerial and submarine slope were investigated using large-scale ring shear tests on the saturated and dry volcaniclastic material. The shear behaviour of the material under different drainage conditions was analysed during tests conducted at DPRI, Kyoto University. Pore pressure generation, mobilised shear strength and grain crushing, within a range of displacements encompassing the different stages of evolution of the slope, were considered. Experimental results suggest that even at larger displacements, shear strength of the dry material explains the virtual stability of the slope. Conversely, full or partial liquefaction can be invoked to explain the submarine failure and the subsequent long runout (more than 1,000 m) of the failed materials.     

Effects of geological and tectonic characteristics on the earthquake-triggered Daguangbao landslide,China

The Daguangbao landslide is the largest co-seismic landslide triggered by the Wenchuan earthquake (Ms 8.0) occurred on 12 May 2008. The landslide, which is 4.6 km long and 3.7 km wide, involves a volume of approximately 1.2 × 10⁹ m³. An exposed slip surface, situated at the southern flank of its source area, was observed with a length of 1.8 km along the main sliding direction and an area of 0.3 km². To study the geological and tectonic characteristics of the source area and their contributions to the landslide formation during the earthquake, detailed geological investigations were firstly conducted. And it is reached that the landslide occurred on the northwestern limb of the Dashuizha anticline with its scarp showing several geological structures, including joint sets, local faults, and folds. These tectonic-related structures potentially influenced the failure of the landslide. Secondly, further investigations were focused on the inclined planar sliding surface using 12 exploratory trenches, nine boreholes, a tunnel, borehole sonic data, and micro-images. These data reveal that the rock mass along the sliding surface was the fragmented rock of a bedding fault. A pulverized zone was observed on the sliding surface, which was the zone of shear localization during the landslide. This suggests that the shear failure of the Daguangbao landslide developed within the bedding fault. The rapid failure of the landslide was associated with the degradation of the rock mass strength of the bedding fault both before and during the 2008 Wenchuan earthquake. With this study, we propose that a pre-existing large discontinuity within a slope may be the basis for initiating a large landslide during earthquake.     

Investigation and dynamic analysis of a catastrophic rock avalanche on September 23, 1991, Zhaotong,China

At 6:10 p.m. on September 23, 1991, a catastrophic rock avalanche occurred in Zhaotong, Yunnan, southwestern China. Over 216 people were killed when the Touzhai village was overwhelmed directly in the path of the landslide. The landslide involved the failure of about 12 Mm³ of jointed basaltic rock mass from the source area. The displaced materials ran out a horizontal distance of 3650 m over a vertical distance of 960 m, equivalent to a Fahrböschung of 14.7°, and covered an area of 1.38 km². To provide information for hazard zonation of similar type of potential landslides in the same area, we used a dynamic model (DAN-W) with three alternative rheological models to simulate the runout behaviour of the displaced landslide materials and found that a combination of the frictional model and Voellmy model could provide the best performance in simulating this landslide. The simulated results indicated that the duration of the movement is estimated at about 175 s for a mean velocity 21 m/s.     

高速远程地震黄土滑坡发生机制试验研究

1920年海原大地震触发了多处典型高速远程地震黄土滑坡,本文在对西吉党家岔滑坡进行野外调研的基础上,采集了具有代表性的滑带土作为试验样品,以1940年5月18日美国帝国谷强震记录作为波动输入,利用DPRI环剪试验机,对该滑坡的发生机制进行了一系列环剪试验研究。结果表明,地震发生时,坡体潜在滑面的滑带土在强震作用下发生的滑动面液化（Sliding surface liquefaction）现象是导致高速远程滑坡形成的一个重要因素。伴随着滑动面液化过程,滑体产生了逐渐增大的剪切位移及孔隙水压力（地震力作用结束瞬间已分别达到2.03m及104kPa）,并获得了较大的速度,为高速远程滑坡的发生提供了条件。     

Numerical Simulation of Rainfall-induced Xianchi Reservoir Landslide in Yunyang, Chongqing, China

A calamitous landslide happened at 22:00 on September 1, 2014 in the Yunyang area of Chongqing City, southwest China, enforcing the evacuation of 508 people and damaging 23 buildings. The landslide volume comprised 1.44 million m3 of material in the source area and 0.4 million m3 of shoveled material. The debris flow runout extended 400 m vertically and 1600 m horizontally. The Xianchi reservoir landslide event has been investigated as follows: (1) samples collected from the main body of landslide were carried out using GCTS ring shear apparatus; (2) the parameters of shear and pore water pressure have been measured; and (3) the post-failure characteristics of landslide have been analyzed using the numerical simulation method. The excess pore-water pressure and erosion in the motion path are considered to be the key reasons for the long-runout motion and the scale-up of landslides, such as that at Xianchi, were caused by the heavy rainfall. The aim of this paper is to acquired numerical parameters and the basic resistance model, which is beneficial to improve simulation accuracy for hazard assessment for similar to potentially dangerous hillslopes in China and elsewhere.     

Dynamic process of the Wenjiagou rock landslide in Sichuan Province,China

A rock avalanche is a geological event that is always sudden, rapid and with a long run-out, and can result in large loss of lives and property. The Wenjiagou rock avalanche was a high-speed rock landslide caused by a strong earthquake, in Mianzhu, Sichuan Province, southwest China. In this study, we reproduce the movement and deposition processes of the sliding mass by numerical simulation. We analyze the effects of the friction coefficient of each slip surface and the strength of the parallel bonds and contact stiffness between particles on the dynamic process and deposit features using three-dimensional particle flow code (PFC3D). The simulation results agree with the field measurements when the friction coefficient is 0.2, parallel bond strength is 2 MPa, and contact stiffness is 2?×?10⁸ kN/m. The landslide lasted about 115 s from the initial movement to the final deposition at the exit of the valley. The maximum velocity of the sliding mass was 114 m/s.     

库岸深层老滑坡间歇性复活的动力学机制研究

库岸深层老滑坡在季节性降雨和周期性库水位变动联合作用下往往表现出间歇性复活特征。在这一复活过程中,滑动期与间歇期交替出现,滑带土经历不同速率的剪切和不同时长的固结。从滑动期内残余强度的剪切速率效应、间歇期内峰值抗剪强度的恢复特征以及间歇期过渡到滑动期的孔隙水压力触发过程3个方面着手,建立了描述库岸深层老滑坡间歇性复活的动力学方程。塘角村1号滑坡滑带土试样的环剪试验结果显示：残余强度在较小速率范围内表现出负速率效应,而当剪切速率达到一定值后残余强度不再减小,且有微弱增长趋势;峰值强度在短时间内有较明显的恢复,但在较小位移后衰减至残余强度;孔隙水压力触发剪切破坏的发生滞后于所施加的水压力,这一滞后过程为孔隙水压力的扩散过程。基于试验成果,根据所建立的动力学方程,对库岸深层老滑坡间歇性复活的动力学机制进行了讨论,从而为此类滑坡的预测和防灾减灾提供有价值的参考。     

Application of DDA to simulate characteristics of the Tsaoling landslide

This study simulates the kinematic behavior of sliding blocks of rock in the earthquake-induced Tsaoling landslide using seismic discontinuous deformation analysis (DDA). We assume sliding rocks are elastic blocks. Detailed joint shear strength parameters are set in DDA in a manner compatible with what is known about the Tsaoling landslide mechanisms. Landslide run-out distance, information from survivors, and the post-failure topography are used to constrain the computational results. Calculations demonstrate that sliding rocks from the ground surface decoupled from those near the basal shear surface during the landslide. Local residents survived because surficial rocks were never deeply buried during the landslide. Additionally, shear strength parameters of material in the deposition area strongly govern final deposit topography. Computational results correlate well with actual post-failure topography.     

Mechanism for the rapid motion of the Qianjiangping landslide during reactivation by the first impoundment of the Three Gorges Dam reservoir, China

The first impoundment of the Three Gorges Dam reservoir in China started from a water surface elevation of 95 m on June 1, 2003 and reached 135 m on June 15, 2003. Shortly after the water level reached 135 m, many slopes began to deform and some landslides occurred. The Qianjiangping landslide is the largest one; it occurred on the early morning of July 14, 2003 and caused great loss of lives and property. Field investigation revealed that, although failure occurred after the reservoir reached 135 m, the stability of the slope was already reduced by preexisting sheared bedding planes. To study the mechanism of the rapid motion of this reactivated landslide, two soil samples were taken from a yellow clay layer and a black silt layer in the sliding zone, respectively, and a series of ring shear tests were conducted on the samples. One series of ring shear tests simulates the creep deformation behavior, while the other series simulates different shear rates. Conclusions drawn from analysis of the ring shear tests indicate that the mechanism of the rapid motion of the reactivated landslide was caused by the rate effect of the black silt layer during the motion phase after the creep failure. The yellow clay layer did not play any important role in the rapid motion in the 2003 event.     

Dynamic process simulation of rainfall-induced Sanxicun landslide based on a thermo-poro-elastic approach

The Sanxicun landslide occurred on July 10, 2013, in Sanxicun Village, which is located in Dujiangyan City, Sichuan Province, China. It travelled up to 1200 m, destroyed 11 houses, and killed 166 people in the village. To explain how this landslide could travel such a large distance and cause such serious damage, this study used a thermo-poro-elastic approach coupled with the Savage–Hutter model to simulate the dynamic process of the Sanxicun landslide. The simulated results were compared with the actual results, as well as those of other researchers. It showed that the simulated results for the landslide profile and mass accumulation scope were basically consistent with the actual results. The simulated landslide runout was 1242 m, which was quite close to the actual value. The simulated maximum mass accumulation thickness was 16.4 m. The maximum velocity was 32.6 m/s, which was between those calculated by Yin et al. (J Eng Geol 22(2):309–318, 2014), Yin et al. (Landslide 13:9–23, 2016), and the various trends were found to be consistent. The temperature change and the pore water pressure evolution in the shear zone during sliding are also obtained by simulation. This study had recreated the Sanxicun landslide motion process from the view of thermo-poro-elastic coupling within the shear zone.     

地震诱发的高速远程滑坡过程中土结构破坏和土粒子破碎引起的两种不同的液化机理

本文的主要目的是探讨地震诱发的高速远程滑坡的液化机理。通过排水和不排水环剪的对比试验,以及对地震诱发的不同类型的滑坡实例的现场调查,考察了土结构破坏和土粒子破碎产生的滑动带液化的不同机理。土结构破坏引起的液化在滑坡发生时即可产生,而土粒子破碎引起的液化需要在滑动过程中产生。在此基础上提出了滑动带向滑体内的扩展模型,并分析了两种液化机理引起的滑坡体形态的差异。本文的独到之处在于揭示了土粒子破碎对高速远程滑坡的重要影响,强调了在滑坡灾害预测研究中必须同等重视滑坡体结构和土粒子易破碎性的调查分析。     

Stability assessment of Jinlong village landslide,Sichuan

The Jinlong village landslide is located in Zitong County, Sichuan and approximately 150 km east of Wenchuan. The landslide has exhibited creep deformation for nearly 30 years. Field investigations indicated that the slope deformation was caused by the combined effects of unfavorable topographic and geological conditions and earthquakes. The sliding surface is along a contact between silty clay and mudstone. The Wenchuan earthquake accelerated the creep, causing bulging of the ground surface. Shear test results of the silty clay near the sliding surface indicated that the residual strength is consistent with the stability state of the landslide. The factors of safety were calculated using the limit equilibrium method (LEM) and the method of fast Lagrangian analysis of continua in two dimensions. The results using the LEM indicate that the stability is clearly affected by seismic shaking, and when the peak ground acceleration is 0.08g, the slope reaches the limit state. The shear failure surface given by numerical simulation develops on the contact between the clay and silty mudstone, which confirmed the assumed sliding surfaces’ location using the LEM.     

Characteristics and numerical runout modelling of a catastrophic rock avalanche triggered by the Wenchuan earthquake in the Wenjia valley,Mianzhu, Sichuan,China

The 2008 Wenchuan earthquake triggered more than 100 rock avalanches with volumes greater than 10 million cubic metres. The rock avalanche with the longest runout amongst these destructive landslides occurred in the Wenjia valley, Mianzhu, Sichuan, China. The landslide involved the failure of about 27.5 million cubic metres of sandstone from the source area. The displaced material travelled about 4,170 m with an elevation descent of about 1,360 m, equivalent to a fahrböschung of 16.9° and covered an area of 1.5 million square metres, with the final deposited volume of approximately 49 million cubic metres. The catastrophic event destroyed the village of Yanjing, killed 48 people and buried some houses at the mouth of the Wenjia valley. On the basis of a detailed field investigation, we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in two run-ups and a superelevation along the runout path, and downslope enlargement due to the entrainment of path materials. A numerical model (DAN3D) is used to simulate the post-failure behaviour of the rock avalanche. By means of trial and error, a combination of the frictional model and Voellmy model is found to provide the best performance in simulating this rock avalanche. The simulation results reveal that the rock avalanche had a duration of about 240 s and an average velocity of 17.4 m/s.     

Numerical runout simulation of debris avalanches in the Faroe Islands, North Atlantic Ocean

The Faroe Islands in the North Atlantic Ocean are susceptible to flow-type landslides in coarse-grained highly organic colluvium. Following several hazardous debris avalanche events, research work has been initiated to quantify landslide risk. A central task in this work is to predict landslide runout behavior. From numerical simulation of four debris avalanches, this study provides a first screening of which rheology and appertaining input parameters best predict runout behavior of debris avalanches in the Faroe Islands. Three rheologies (frictional, Voellmy, and Bingham) are selected and used for individual back analysis of the events in the numerical models BING and DAN3D. A best fit rheology is selected from comparing predicted and observed landslide runout behavior. General back analysis to identify the optimal input parameters for the chosen rheology is performed by cross validation, where each debris avalanche is modeled with input parameters from the three other events. Optimal input parameters are found from the model run producing the most accurate runout length and velocity. The Bingham is selected as the best fit rheology, a result differing from similar studies of coarse-grained landslides. A reason for why particularly the frictional rheology proves unsuitable is its tendency to produce too long runout lengths of the low-weight runout material, a result showing important limitations for using the frictional rheology in DAN3D. Optimal Bingham input parameters are τ _y ?=?980 Pa and μ _b ?=?117 Pa/s. However, future studies performed in 2D models are needed for precise parameterization before results can be used for landslide risk assessment.     

Numerical modeling of the June 24, 2015, Hongyanzi landslide generated impulse waves in Three Gorges Reservoir,China

Subaerial landslides falling into confined water bodies often generate impulsive waves. Damaging landslide tsunamis in Three Gorges Reservoir, China, have struck several times in the last 15 years. On June 24, 2015, a 23?×?10⁴ m³ slope failure occurred on the east bank of the Daning River opposite Wushan Town. The sliding mass intruded into the Three Gorges Reservoir and initiated a reservoir tsunami that resulted in two deaths and significant damage to shipping facilities. A post-event survey revealed the landslide geometry and wave run-up distribution, while an eyewitness video captured most of the landslide motion. Employing these firm constraints, we applied the Tsunami Squares method to simulate the 2015 Hongyanzi landslide and tsunami. The simulation revealed that the landslide experienced a progressive failure in the first few seconds and impacted the water with a maximum velocity of ~?16 m/s. The initial wave propagated to the opposite shore in an arch shape, and the water surface reached a maximum amplitude of ~?11 m near the landslide. Wave amplitude-time curves at four points on the river cross section show that the initial wave reached Wushan town in about 50 s with an average wave velocity of ~?30 m/s. The maximum wave run-ups on the shoreline opposite the landslide are around 6 m and attenuate to less than 1 m beyond 2-km distance. The landslide simulation matches the observed geological profile and the eyewitness video, and the numerical results coincide with the observed wave run-up heights. Nearly 80% of landslide energy is lost due to frictional resistances, but the remaining fraction imparted to the tsunami carried catastrophic consequences to a large region. The numerical results emphasize the efficiency and accuracy of Tsunami Squares method for a “Quick Look” simulation of a potential landslide.     

An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide

A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide.     

A geotechnical investigation of the retrogressive Yaka Landslide and the debris flow threatening the town of Yaka (Isparta,SW Turkey)

In this study the factors affecting the retrogressive Yaka Landslide, its mechanism and the hazard of debris flow on the town of Yaka are investigated. In the landslide area, the first landslide was small and occurred in March 2006 on the lower part of the Alaard?ç Slope near the Gelendost District town of Yaka (Isparta, SW Turkey). The second, the Yaka Landslide, was large and occurred on 19 February 2007 in the soil-like marl on the central part of Alaard?ç Slope. The geometry of the failure surface was circular and the depth of the failure surface was about 3 m. Following the landslide, a 85,800 m³ of displaced material transformed to a debris flow. Then, the debris flow moved down the Eglence Valley, traveling a total distance of about 750 m. The town of Yaka is located 1,600 m downstream of Eglence Creek and hence poses a considerable risk of debris flow, should the creek be temporarily dammed as a result of further mass movement. Material from the debris accumulation has been deposited on the base of Eglence Valley and has formed a debris-dam lake behind a debris dam. Trees, agricultural areas, and weirs in the Eglence Creek have seen serious damage resulting from the debris flow. The slope angle, slope aspect and elevation of the area in this study were generated using a GIS-based digital elevation model (DEM). The stability of the Alaard?ç Slope was assessed using limit equilibrium analysis with undrained peak and residual shear strength parameters. In the stability analyses, laboratory test results performed on the soil-like marls were used. It was determined that the Alaard?ç Slope is found to be stable under dry conditions and unstable under completely saturated conditions. The Alaard?ç Slope and its vicinity is a paleolandslide area, and there the factor of safety for sliding was found to be about 1.0 under saturated conditions. The Alaard?ç Slope and the deposited earthen materials in Eglence Creek could easily be triggered into movement by any factors or combination of factors, such as prolonged or heavy rainfall, snowmelt or an earthquake. It was established that the depth of the debris flow initiated on the Yaka Landslide reached up to 8 m in Eglence Creek at the point it is 20 m wide. If this deposited material in Eglence Creek is set into motion, the canal that passes through Yaka, with its respective width and depth of 7 and 1.45 m, could not possibly discharge the flow. The destruction or spillover of this canal in Yaka could bring catastrophic loss to residents which are located within 3–5 m of the bank of the canal. Furthermore, if material present in the landslide source area slides and this displaced material puts pressure on the unstable deposited material in Eglence Creek, even more catastrophic loss would occur to the town of Yaka. In this study, it was determined that debris flows are still a major hazard to Yaka and its population of 3,000. The results provided in this study could help citizens, planners, and engineers to reduce losses caused by existing and future landslides and debris flow in rainfall and snowmelt conditions by means of prevention and mitigation.     

The mechanism of the 1941 Tsaoling landslide, Taiwan: insight from a 2D discrete element simulation

Tsaoling is located in Southwestern Taiwan, 10 km east of the frontal thrusts of the mountain belt. Five large historical landslide events were recorded from 1862 to 1999. No details of the earliest landslide event (1862) are available, thus this paper deals with the 1941 landslide event. Using the Particle Flow Code in two dimensions (PFC 2D) to simulate the mechanism of the Tsaoling landslide in 1941, this study shows that the landslide block developed cracks and slid down 0.2–1.8 m on the sliding plane. The cracks concentrated in certain zones, which corresponded to future landslide detachment planes. During the vibration simulation, the cracks spread from the shear plane to ground surface. Monitoring the variations of the displacements, velocity, and stress during vibration simulation showed that the peak velocity and stress in the transition zones occurred at 3 s. The displacement of the left part of the block exceeded 1.3 m, and the displacement of the right part was less than 1.3 m during vibration simulation. These results suggest that the left part of the block was pushed down by the right part, ultimately inducing a landslide during an earthquake.