CLASSIFICATION OF TRANSLATIONAL LANDSLIDE ACTIVITY USING VEGETATION ANOMALIES INDICATOR (VAI) IN KUNDASANG, SABAH

This paper introduced a novel method of landslide activity mapping using vegetation anomalies indicators (VAIs) obtained from high resolution remotely sensed data. The study area was located in a tectonically active area of Kundasang, Sabah, Malaysia. High resolution remotely sensed data were used to assist manual landslide inventory process and production on VAIs. The inventory process identified 33, 139, and 31 of active, dormant, and relict landslides, respectively. Landslide inventory map were randomly divided into two groups for training (70%) and validation (30%) datasets. Overall, 7 group of VAIs were derived including (i) tree height irregularities; (ii) tree canopy gap; (iii) density of different layer of vegetation; (iv) vegetation type distribution; (v) vegetation indices (VIs); (vi) root strength index (RSI); and (vii) distribution of water-loving trees. The VAIs were used as the feature layer input of the classification process with landslide activity as the target results. The landslide activity of the study area was classified using support vector machine (SVM) approach. SVM parameter optimization was applied by using Grid Search (GS) and Genetic Algorithm (GA) techniques. The results showed that the overall accuracy of the validation dataset is between 61.4–86%, and kappa is between 0.335–0.769 for deep-seated translational landslide. SVM RBF-GS with 0.5m spatial resolution produced highest overall accuracy and kappa values. Also, the overall accuracy of the validation dataset for shallow translational is between 49.8–71.3%, and kappa is between 0.243–0.563 where SVM RBF-GS with 0.5m resolution recorded the best result. In conclusion, this study provides a novel framework in utilizing high resolution remote sensing to support labour intensive process of landslide inventory. The nature-based vegetation anomalies indicators have been proved to be reliable for landslide activity identification in Malaysia.

Modeling The Post-Failure And Run-Off For a Translational Landslide In Taiwan By Material Point Method

The material point method (MPM) is an extended finite element method that can be used to simulate large deformation scenarios. A massive translational landslide in Taiwan was adopted to validate the numerical technique as thorough investigations, including the digital terrain models (DTMs), laboratory experiments, and numerical analyses, were available in a forensic report. The MPM code Anura3D was used to mimic the landslide’s kinematics, post-failure, and run-off process. An unstable sandstone/shale interlayer was found to lead the slope sliding; therefore, the before-and-after DTMs from the report mentioned above were used to examine the run-off distance and deposition to determine the best fit of reduced material properties for this layer. The sliding paths, displacements, velocities of the sliding can be evaluated by dividing the material points into several groups to differentiate the kinematic among them. Meanwhile, the simulations were compared with different numerical methods. The landslide duration and possible maximum safety distance were also assessed. This study has demonstrated that the MPM can analyze the large deformation, post-failure, and run-off distance of landslides. The critical timing of a slope failure is possible to be an essential index on national spatial planning for future disaster reduction.

Analysis of the instability conditions and failure mode of a special type of translational landslide using long-term monitoring data: a case study of the Wobaoshi landslide (in Bazhong, China)

A translational landslide comprised of nearly horizontal sandstone and mudstone interbeds occurred in the Ba River basin of the Qinba–Longnan mountainous area. Previous studies have succeeded to some extent in investigating the formation mechanism and failure mode of this type of rainfall-induced landslide. However, it is very difficult to demonstrate and validate the previously established geomechanical model, owing to lack of landslide monitoring data. In this study, we considered a translational landslide exhibiting an unusual morphology, i.e., the Wobaoshi landslide, which occurred in Bazhong, China. First, geological conditions of this landslide were determined through field surveys, and the deformation and failure mode of the plate-shaped main bodies were analyzed. Second, long-term monitoring was performed to obtain multiparameter monitoring data (width of the crown crack, rainfall, and accumulated water pressure in cracks). Finally, an equation was developed to evaluate the critical water height of the multistage bodies, i.e., hcr, based on the geomechanical model analysis of the multistage main sliding bodies, and the reliability of this equation was verified using long-term relevant monitoring data. Subsequently, the deformation and failure mode of the plate-shaped bodies were analyzed and investigated based on numerical simulations and calculations. Thus, the monitoring data and geomechanical model proved that the accumulated water pressure in cracks makes cracks open much wider and causes the plate-shaped bodies to creep. Simultaneously, an optimized monitoring methodology was proposed for this type of landslide. Therefore, these research findings are of reference significance for the rainfall-induced translational landslides in this area.

Analysis of instability conditions and failure mode of a special type of translational landslide using a long-period monitoring data: a case study of the Wobaoshi landslide (Bazhong city, China)

A translational landslide comprising nearly horizontal sand and mud interbed was widely developed in the Ba river basin of the Qinba–Longnan mountain area. Scholars have conducted theoretical research on this rainfall-induced landslide; however, owing to the lack of landslide monitoring engineering and data, demonstrating and validating the theoretical research wasdifficult. This study considered a translational landslide with an unusual morphology: the Wobaoshi landslide, which is located in Bazhong city, China. First, the formation conditions of this landslide were ascertained through field exploration, and the deformation and failure characteristics of the plate-shaped sliding body were analyzed. Then, long-period monitoring engineering was conducted to obtain multi-parameter monitoring data, such as crack width, rainfall intensity, and pore-water pressure. Finally, through the mechanical model analysis of the multi-stage sliding bodies, the calculating formula of the maximum height of the multi-stage plate girders, hcr, was derived，and the long-period monitoring data were used to verify its accuracy. Combined with numerical simulation and calculations, the deformation and failure modes of the plate-shaped sliding bodies were analyzed and explored. In this paper, the multi-parameter monitoring data proved that the stability of the sliding body is affected greatly by the rainfall intensity and pore-water pressure and the pore-water pressure in the crack is positive for the beginning of the plate-shaped sliding bodies, and an optimization monitoring method for this type of landslide was proposed. Therefore, this paper has theoretical and practical significance for the intensive study of translational landslides in this area.

Petrography, Geology Structure and Landslide Characterization of Sumatra Fault Deformation: Study Case In Km 10-15 Highway, Koto Baru Sub District, West of Sumatra

Research area is around Tanjung Balik, Koto Baru Sub Base, Lima Puluh Kota District, West Sumatra Province. Located along the highway Km 10-15 Riau – West Sumatra and the coordinate around 00˚08'40 '' LU - 0˚11'20 '' N and 100˚45'20 '' BT - 100˚47'00 '' BT. The purpose of research to identify petrography, microstructure, types of landslides and the geological condition. The methods using polarization microscope, stereography, landslide identification survey and geological mapping. The result of study shows the petrography analysis of lithology of study area are classified into three types of rocks are Feldspathic Greywacke, Lithic Arenite, and Slate. Microstructures trending system show the foliation structure that is relatively Southeast-Northwest. Types of landslide which dominates in the research area are debris avalanche and translational landslide. Geological analysis show some of rock units are classified into two units: Sandstone Unit and Slate Unit. Sandstone Unit spread in the northern part of the study area, while Slate Unit spread in the southern part of the study area. The characteristics of these rocks showed Pematang Formation.

Modelling the 1929 Grand Banks slump and landslide tsunami

On 18 November 1929, an Mw 7.2 earthquake occurred south of Newfoundland, displacing >100 km3 of sediment volume that evolved into a turbidity current. The resulting tsunami was recorded across the Atlantic and caused fatalities in Newfoundland. This tsunami is attributed to sediment mass failure because no seafloor displacement due to the earthquake has been observed. No major headscarp, single evacuation area nor large mass transport deposit has been observed and it is still unclear how the tsunami was generated. There have been few previous attempts to model the tsunami and none of these match the observations. Recently acquired seismic reflection data suggest that rotational slumping of a thick sediment mass may have occurred, causing seafloor displacements up to 100 m in height. We used this new information to construct a tsunamigenic slump source and also carried out simulations assuming a translational landslide. The slump source produced sufficiently large waves to explain the high tsunami run-ups observed in Newfoundland and the translational landslide was needed to explain the long waves observed in the far field. However, more analysis is needed to derive a coherent model that more closely combines geological and geophysical observations with landslide and tsunami modelling.