Soil Slides Research Articles

EVALUATING THE INFLUENCE OF SPATIAL RESOLUTION ON LANDSLIDE DETECTION: A CASE STUDY IN THE CARLYON BEACH PENINSULA, WASHINGTON

Abstract. Landslides are geological events in which masses of rock and soil slide down the slope of a mountain or hillside. They are influenced by topography, geology, weather, and human activity, and can cause extensive damage to the environment and infrastructure, as well as delay transportation networks. Therefore, it is imperative to detect early-warning signs of landslide hazards as a means of prevention. Traditional landslide surveillance consists of field mapping, but the process is costly and time consuming. Modern landslide mapping uses Light Detection and Ranging (LiDAR) derived Digital Elevation Models (DEMs) and sophisticated algorithms to analyze surface roughness and extract spatial features and patterns of landslide and landslide-prone areas. This study follows a previous study performed that demonstrated that it is possible to detect unstable terrain using algorithmic mapping techniques. The focus of this study is to show how spatial resolution can influence the accuracy of the classification results. The DEM data was resampled from 6 to 12, 24, 48 and 96 ft spatial resolution. The surface feature extractors employed (local topographic range, local topographic variability, slope, and roughness) are fused and analyzed simultaneously by applying k-means and Gaussian Mixture Model (GMM) clustering methods. When compared with the detailed, independently compiled landslide reference map, our data shows a decrease in performance as spatial resolution decreases. These results suggest that spatial resolution does impact the performance of landslide classification.

Mechanical Property of Lateral Piles for Pile Composite Foundation Loaded by Model Test

Under vertical load, the composite foundation may be damaged due to insufficient lateral restraint capacity. If the lateral restraint pile is added to the edge of the composite foundation, the lateral stability can be effectively enhanced. This new reinforcement scheme is called a combined composite foundation. For the combined composite foundation, the lateral restraint piles will bear a certain force when the composite foundation is loaded, and the force may cause the piles horizontal displacement, instability, or even failure. After preload on the composite foundation, the mechanical behavior of lateral restraint piles will be more sophisticated. To study the mechanical behavior of lateral restraint piles under such condition, a laboratory model test was conducted. The results are suggested as follows: Axial force distribution curves tend to be “S” shape with two peak values at the upper and lower parts, respectively. The negative axial force is distributed at the upper part, and the positive axial force is distributed at the lower part. The bending moment and lateral soil pressure distribution of piles appear with the regularity of “increase-decrease” along the depth. Such a phenomenon is associated with the expansion of a potential slip surface. In accordance with the relative location of the potential slide surface and the piles, the lateral restraint piles can fall into three sections. Different sections get different stresses. The reinforcement scopes have an impact on the stress of different lateral restraint piles. With the increase of the reinforcement scope, the axial force, soil pressure, and bending moment show the regularity of increase. The values of axial force, the lateral soil pressure, and the bending moment increase with load growth and become stable when the load is larger than 60 kN. This is associated with the piles in the composite foundation, which verifies the reinforcement effect to prevent the soil slide and the foundation deformation.

Failure mode of rainfall-induced landslide of granite residual soil, southeastern Guangxi Province, China

Abstract. Granite residual soil landslides are widely distributed in the southeast of Guangxi, China. They pose threats to local communities, economic development and ecological restoration. To understand the failure mode, the landslide can provide a scientific basis for early warning and prevention. In this study, we conducted artificial flume model tests to investigate the failure mode of granite residual soil landslide. The macroscopic phenomena of landslides were observed and summarized. The response and variations of soil moisture content and pore water pressure were analyzed. And the discrepancies in landslide initiation were explored. The results had three aspects: (1) the response of volume moisture content was not synchronized with that of pore water pressure. Their variations were influenced by initial dry density, slope angle and rainfall intensity. The fluctuation of pore water pressure depended on soil mechanical behavior and its diffusion. (2) The differences in the formation process of granite residual soil landslides included the initiation time and mode. The starting time of landslide was delayed with increasing initial dry density and slope angle but shortened with increasing rainfall intensity. The failure mode could be changed from a sudden type to a progressive type due to the increase in initial dry density. (3) There are five stages in the landslide mobilization as follows: rain infiltration and crack generation, soil slide at the slope toe, occurrence of surface runoff and soil erosion, formation of steep-free surface, and soil slide at the upper slope. This research can provide valuable reference for the prevention and early warning of granite residual soil landslide in southeastern Guangxi.

Evaluation of Remote Mapping Techniques for Earthquake-Triggered Landslide Inventories in an Urban Subarctic Environment: A Case Study of the 2018 Anchorage, Alaska Earthquake

Earthquake-induced landslide inventories can be generated using field observations but doing so can be challenging if the affected landscape is large or inaccessible after an earthquake. Remote sensing data can be used to help overcome these limitations. The effectiveness of remotely sensed data to produce landslide inventories, however, is dependent on a variety of factors, such as the extent of coverage, timing, and data quality, as well as environmental factors such as atmospheric interference (e.g., clouds, water vapor) or snow and vegetation cover. With these challenges in mind, we use a combination of field observations and remote sensing data from multispectral, light detection and ranging (lidar), and synthetic aperture radar (SAR) sensors to produce a ground failure inventory for the urban areas affected by the 2018 magnitude (Mw) 7.1 Anchorage, Alaska earthquake. The earthquake occurred during late November at high latitude (∼61°N), and the lack of sunlight, persistent cloud cover, and snow cover that occurred after the earthquake made remote mapping challenging for this event. Despite these challenges, 43 landslides were manually mapped and classified using a combination of the datasets mentioned previously. Using this manually compiled inventory, we investigate the individual performance and reliability of three remote sensing techniques in this environment not typically hospitable to remotely sensed mapping. We found that differencing pre- and post-event normalized difference vegetation index maps and lidar worked best for identifying soil slumps and rapid soil flows, but not as well for small soil slides, soil block slides and rock falls. The SAR-based methods did not work well for identifying any landslide types because of high noise levels likely related to snow. Some landslides, especially those that resulted in minor surface displacement, were identifiable only from the field observations. This work highlights the importance of the rapid collection of field observations and provides guidance for future mappers on which techniques, or combination of techniques, will be most effective at remotely mapping landslides in a subarctic and urban environment.

Development of smart boulders to monitor mass movements via the Internet of Things: a pilot study in Nepal

Abstract. Boulder movement can be observed not only in rockfall activity, but also in association with other landslide types such as rockslides, soil slides in colluvium originating from previous rockslides, and debris flows. Large boulders pose a direct threat to life and key infrastructure in terms of amplifying landslide and flood hazards as they move from the slopes to the river network. Despite the hazard they pose, boulders have not been directly targeted as a mean to detect landslide movement or used in dedicated early warning systems. We use an innovative monitoring system to observe boulder movement occurring in different geomorphological settings before reaching the river system. Our study focuses on an area in the upper Bhote Koshi catchment northeast of Kathmandu, where the Araniko highway is subjected to periodic landsliding and floods during the monsoons and was heavily affected by coseismic landslides during the 2015 Gorkha earthquake. In the area, damage by boulders to properties, roads, and other key infrastructure, such as hydropower plants, is observed every year. We embedded trackers in 23 boulders spread between a landslide body and two debris flow channels before the monsoon season of 2019. The trackers, equipped with accelerometers, can detect small angular changes in the orientation of boulders and large forces acting on them. The data can be transmitted in real time via a long-range wide-area network (LoRaWAN®) gateway to a server. Nine of the tagged boulders registered patterns in the accelerometer data compatible with downslope movements. Of these, six lying within the landslide body show small angular changes, indicating a reactivation during the rainfall period and a movement of the landslide mass. Three boulders located in a debris flow channel show sharp changes in orientation, likely corresponding to larger free movements and sudden rotations. This study highlights the fact that this innovative, cost-effective technology can be used to monitor boulders in hazard-prone sites by identifying the onset of potentially hazardous movement in real time and may thus establish the basis for early warning systems, particularly in developing countries where expensive hazard mitigation strategies may be unfeasible.

Recharge response and kinematics of an unusual earthflow in Liechtenstein

Understanding landslide behavior over medium and long timescales is crucial for predicting landslide hazard and constructing accurate landscape evolution models. The behavior of landslides in soil that undergo periodic displacements, termed earthflows or compound soil slides, is especially difficult to forecast at these timescales. This is because velocities can increase by orders of magnitude over annual to decadal timescales, due to processes such as changing recharge conditions, erosion of the landslide toe, and retrogression of the landslide head. In this paper, we provide a detailed analysis of the Schlucher landslide, an unusual earthflow that is perched above the village of Malbun, Liechtenstein. This landslide had been displacing by 10 to 20 cm/year until 2015, when displacements on the order of 2 m/year occurred from 2016 to 2018. These large displacements damaged landslide mitigation measures, caused numerous surface deformation features, and threatened the local population downstream of the earthflow. This landslide has an unusually long monitoring record, with accurate displacement and climatic data available since 1983. We analyze this nearly 40-year monitoring time series to estimate recharge from snowmelt and rainfall, and its correlation with displacement. We also analyze recently collected, high-resolution surface and subsurface data in order to understand landslide response to recharge, landslide kinematics through time, and catastrophic failure potential. We find that interannual displacements can be explained with variations in recharge; however, periodic surges with recurrence times of tens of years must be explained by other mechanisms. In particular, recharge into the landslide during the recent acceleration (2016 to 2018) was not anomalously high. Instead, we argue that loss of internal strength is responsible for this recent acceleration period, and that this mechanism should be considered when forecasting the surge potential for certain earthflows and soil slides.

Failure mechanism and stability analysis of a reactivated landslide occurrence in Yanyuan City, China

This paper presents a recent rainfall-induced reactivated compound soil slide in Yanyuan County, China, on July 19, 2018. In this paper, according to the elaborate investigation of the soil slide area at field and prefailure slope stability analysis, the corresponding failure mechanisms are comprehensively studied. Unmanned aerial vehicle (UAV) based on remote sensing, three-dimensional modelling, in situ and laboratory experimental testing, borehole exploration, and numerical simulation were carried out in this work. According to the results, two different sliding processes were identified involving the main sliding and lateral collapse. The main sliding occurred as multiple stages along with two different types of slip zones, which involve a preexisting basal zone of the ancient landslide and an interlaminar shear zone within the ancient landslide deposits. The predominance of reactivated surface geomorphology provides a clue to elucidate the dominant compound movement of the event. Unconsolidated sliding mass and the basal sliding surface are ideal for the development of the reactivation motion. Saltatory microrelief of the original slope determined the retrogressive failure type of the soil slide. The well-developed groundwater in the landslide area significantly increased the soil mass saturation, with an average saturation value of 98%, formed dominant seepage in the sliding mass, and promoted landslide reactivation. Furthermore, rainwater infiltration due to 14 days’ antecedent cumulative rainfall of 350.6 mm directly contributed to the occurrence of the landslide by increasing the pore water pressure in the slope. The maximum shear plastic strain and displacement obtained by numerical simulation show that the lateral slope was unstable with the removal of the main sliding. Because the soil slide is located in the west area of the Emeishan Large Igneous Province (ELIP), it is a partial resurrection of the ancient basalt landslide. Therefore, this study has a certain significance for revealing the reactivated mechanism of basalt ancient landslide.

Analytical Hierarchy Process Method Based Analysis on Road Safety Inspection at Metu - Yayo Road Segment

Now days road safety becomes a worldwide concern. Similarly Road safety risk has been a major issue in the study area (Metu- Yayo road segment). The successful assessments of road safety inspection within the study area are very essential to minimize future road accidents faced by the entire road user. The study were started by examining the current condition of the road using road safety inspection manual then it used focus group judgments and it is analyzed by analytical hierarchical process method based pairwise comparison in identification of contributing factors for the road safety risk using two levels of Analytical Hierarchical process, and four major factors i.e. pavement surface condition, road geometry condition, road side environment condition, road traffic control condition, and also it tries to prioritize the road section to identify the road with better facilities and the road in the worst condition. During road safety inspection in the study area the road experience early stages of pavement distresses, road traffic sign related problems, sight distance obstruction, and soil slide related problems this in turn speeds up the road safety risk and increases the occurrence of road traffic accidents. As a result, this study concluded, road traffic control factors were the most significant factors which contributes to the occurrences of road safety risk. In comparison, Lakosaya to Yayo road section is the found in a better condition, but the road section from Mechi to Lakosaya is found in worse condition in the study area.

A numerical geotechnical model for computing soil slides at banks of water reservoirs

Soil slides can occur when the water level in a lake or a reservoir is lowered. This may take place in situations when a reservoir is flushed to remove sediments. The current study describes a three-dimensional numerical model used for the simulation of reservoir flushing that includes the slide movements. The geotechnical failure algorithms start with modelling the groundwater levels at the banks of the reservoir. A limit equilibrium approach is further used to find the location of the slides. The actual movement of the sediments is computed by assuming the soil to be a viscous liquid and by solving the Navier–Stokes equations. The resulting bed elevation changes from the slides are computed in adaptive grids that change as a function of water level, bed erosion and slide movements. The numerical model is tested on the Bodendorf reservoir in Austria, where field measurements are available of the bank elevations before and after a flushing operation. The results from the numerical simulations are compared with these observations. A parameter test shows that the results are very sensitive to the cohesion and less sensitive to the E and G modules of the soil.

Probabilistic hazard analysis of impulse waves generated by multiple subaerial landslides and its application to Wu Gorge in Three Gorges Reservoir, China

Subaerial landslides can generate impulse waves in reservoirs, fjords, and other water bodies and cause severe damage to the shipping industry, infrastructure, and human communities along the shorelines. Compared with deterministic hazard models, probabilistic hazard analysis is an important tool for assessing the intensity and exceedance probability of impulse waves generated by multiple landslide sources, which are essential for evidence-based risk mitigation and contingency planning. This paper proposes a methodological procedure for systematic probabilistic hazard analysis of impulse waves generated by subaerial landslides considering all relevant landslide sources and multiple uncertainties (i.e., landslide mechanisms, triggering scenarios, and material parameters). The main steps include: (1) definition of the source parameters by parameterizing the epistemic and aleatory uncertainties. In this respect, the logic tree, event tree, and Monte Carlo models were used to organize the uncertainties of landslide mechanism models, parametric scenarios, and material parameters, respectively; (2) estimation of generated waves based on a landslide dynamic analytical model and previously validated empirical wave models derived from prototype scaled experiments; and (3) aggregation of the hazard analysis results in the form of hazard maps and probability maps under parametric scenarios and a specific scenario. Considering the Wu Gorge in the Three Gorges Reservoir as a case study, soil slides and unstable rock slopes were analyzed to quantify the wave hazard along the reservoir under parametric and specific scenarios while considering rainfall and water level fluctuations. The results show considerable wave hazard in the Wu Gorge. For a 20-year return period, the maximum expected height of propagation waves is 14.41 m. The probability of experiencing propagation waves higher than 2 m in 20 years is over 50% in the river segment with high landslide density. The results of the probabilistic wave hazard analysis could be aggregated and disaggregated to accommodate specific requirements of wave risk management.

The Influence of the Slope Exposure on the Soil Aggregation and Structure, Water Stability of Aggregates, and Ecological Microstructure Formation of the Ravine Forest Soils in Pre-Dnipro Region (Ukraine)

Abstract The soil aggregation and structure, water stability of aggregates, and peculiarities of microstructure formation of the ravine forest soils in Dnipropetrovsk region on the example of the northern variant of the ravine forest “Kapitanivskiy” have been identified. The soil properties of southern and northern ravine exposures have been compared. The soil structure, aggregate composition, water stability of aggregates as well as soil-forming processes of the ravine ecosystem have been analyzed. Micro-morphological studies have shown a high degree of aggregation of the upper (0–60 cm) horizons of the soil profile. The structure-forming process is of a zoogenic origin. Aggregates of coprolite nature contain well-disintegrated plant remains. Dark gray, almost black color along the entire area of the micromorphological slide is due to a large amount of organic compounds, which indicates active processes of humification. Fine-dispersed humus consists of a large number of evenly spaced humus clusters. The type of humus is mull. The skeleton consists of minerals of various sizes, dominated by quartz and feldspars. Plasma is humus-clay, homogeneous throughout the entire slide, anisotropic with speckled glowing. Microstructure is mainly aggregated and, in some places, spongy, depending on a microzone of the soil slide. Elemental microstructure is of plasma-silty type. The area of the visible surface of the pores in the upper horizons of the soil profile is fairly large (40%). Pores are round and elongated, of regular shape, here and there with remains of small invertebrates. The deeper the soil slide is, the smaller the area of visible pores along with aggregation becomes. Correlating with micromorphological characteristics, water resistance of structural aggregates reaches very high (90.01% ± 3.07) values in the upper horizons of the soil slide, decreasing at depths. The coefficient of pedality is rather high (7.83 ± 0.81) in the upper horizons, decreasing at depths.

Geomorphological impact of Palu earthquake

Sulawesi and Maluku islands are tectonically under a collision area of four earth crust plates, those are Eurasia, Philliphines Islands, Pacific Ocean and Australian-India Ocean. Palu city in Central Sulawesi island in particular is geologically an area of complex structure. A fault zone of north-west to south-east direction has formed Palu area as a block being squeezed by Palu-Koro strike-slip fault zone. The aim of this research is to know the impact of earthquake happened on October 28, 2018 has caused the fault to activate of being dynamic movement of the area. Using hand camera photos, a morphological survey and analysis show the landslides and slumps could be clearly identified. Rock and soil slide and movement was also strengthened by liquefaction of hydrological fluid content within the Palu block. Morphology of Palu-Koro fault plane was also affected significantly causing landslides and slumps on the fault plane exposed in the earth surface.

The influence law of grouser shape on soil slide sinkage when tracked vehicle travels on soft road

The influence law of a tracked vehicle grouser shape on the soil slide sinkage was investigated in this study via the numerical simulations and physical tests. A finite element model was built using the plastic incremental theory and generalized Hokker’s law, while constitutive soil parameters were obtained via triaxial test. The numerical simulation model was verified by physical test results. Based on the verified numerical simulation model, the influence law of the tracked vehicle grouser shape on the soil slide sinkage was determined. The results show that (1) shear displacement in the lateral direction can increase the soil sinkage in the vertical direction, which is referred to as the “slide sinkage”; (2) there is a linear relationship between the slide sinkage and the shear displacement; (3) the grouser width and height have a positive influence on the amount of slide sinkage. Under the same load, an increase in grouser width and height will cause an increase in the soil slide sinkage. Grouser thickness and pitch have a negative influence on the slide sinkage, and under the same load, increased grouser width and height cause a reduction in the soil slide sinkage. Grouser angle characteristics have no significant effect on the soil sinkage. The application of the slide sinkage in tracked vehicles traveling on soft roads was investigated in multibody system dynamics analysis software Recurdyn to confirm these observations. The results presented in this paper may provide a workable reference for the analysis of tracked vehicles in multibody system dynamics scenarios.

Seismic damage mechanism of bedrock and overburden layer slope reinforced by sheet pile wall

Abstract Sheet pile walls, widely used in landslide control projects, have demonstrated excellent seismic performance during the great Wenchuan earthquake, as indicated by an investigation of retaining walls following earthquake damage. To further understand the mechanism of seismic damage based on the Hilbert–Huang transform method and marginal spectrum identification theory, a large-scale shaking table test of bedrock and overburden layer slope reinforced by sheet pile wall was carried out, and the mechanism of seismic damage was analysed. The results show that the change in marginal spectrum amplitude and characteristic frequency can clearly indicate the degree of seismic damage to the slope soil. First, the dynamic response of the slope soil near sheet pile wall is smaller than the response observed in soil farther from the wall, and the degree of seismic damage near the wall is relatively weaker than that farther away from the wall. Second, the energy of the seismic wave cannot be completely transferred behind the wall, and the strip cracks of soil behind the wall can be determined. Finally, the slope soil slides along a slip surface so that the front edge of the slope is squeezed due to the vertical tensile cracks at the rear edge. In addition, the results confirm the feasibility of the Hilbert–Huang transform method for studying the mechanism of the seismic damage to the structure-soil coupling system.

Investigation of slope instabilities in NW Bhutan as derived from systematic DInSAR analyses

In this work we present a methodology based on remote sensing data to map and classify unstable slopes in high alpine areas and apply this methodology to the Himalaya of northwestern Bhutan. We leverage on radar images acquired by the ESA Envisat and the JAXA ALOS-1 satellites between 2007 and 2011. Synthetic aperture radar differential interferometry (DInSAR) is used to identify and quantify recent ground surface displacements associated with potentially unstable slopes. Optical satellite images and a high-resolution digital surface model is used for the geomorphological classification of individual landforms and deposits associated with displacements. The analysis of the geomorphological characteristics reveals that displacements are associated with: rock slides, mountain slope deformation and rock slope deformation (77.5%), soil creep (4%), soil slides (1.9%) and rock glaciers (12.3%); 4.3% of the detected displacements remain of unknown origin. The method applied here for the assessment of activity likelihood uses a very large number of interferograms obtained with images acquired by different satellites. The method, which is new and replicable, takes advantage of the combination of different acquisition geometries and then combines indices of vegetation cover, layover, velocity estimate and temporal sampling associated with each detected active area to assign a weight. The analysis shows that a cluster of unstable slopes exists in the northwest, potentially related to the presence of an important regional lineament and the distribution of permafrost. Comparatively little ongoing activity is detected in the south, but field validation documents substantial landslide activity in the recent geological past. The dataset here generated, containing 700 potentially unstable areas with an associated activity likelihood, is a novel dataset that makes an essential basis of future analysis to investigate rock slope instability distribution and predisposing factors. Moreover, this dataset represents a new important step towards future landslide hazard assessment in the Himalaya of Bhutan.

Coseismic landslides triggered by the 2018 Hokkaido, Japan (Mw 6.6), earthquake: spatial distribution, controlling factors, and possible failure mechanism

The 2018 Hokkaido Eastern Iburi Mw 6.6 earthquake occurred on September 6, 2018. It triggered a large amount of slope failures near the towns of Atsuma, Mukawa, and Abira, which caused more than 80% of the casualties. This study presents an inventory of 7837 coseismic landslides based on the interpretation of the PlanetScope images, covering about 24 km2 of the disrupted area. The local and global area-volume relationships have shown that the landslides mobilized about 23–38 million m3 of deposits. Most of landslides are shallow soil slides with an average size smaller than what is commonly observed for other earthquakes. Their spatial distribution shows that the mostly affected terrain has an elevation range 100–200 m.a.s.l., with slope gradients of 25–30°. The observed density of the landslides is jointly controlled by the ground motion, slope gradient, topographic wetness index, and, to a lesser degree, tectonic features, e.g., anticlines and faults. The rainfall and the influence of Typhoon Jebi were found to be of secondary importance. The slope failures are also the results of the pulse-like ground motion traits that shook the loose and crushable pumice materials that had been deposited during the eruptions of mounts Tarumae and Eniwa, and the Shikotsu caldera volcanoes, which are prone to flow-like slope failures.

Laboratory simulation to understand translational soil slides and establish movement criteria using wireless IMU sensors

Landslide monitoring and warning using inertial measurement units (IMUs) has shown the potential for remote and real-time applications. However, the studies conducted using the IMU sensors are limited to rainfall-induced landslide detection using soil moisture sensors and accelerometers for predicting slide and measuring tilt, respectively. The tilting of the slope might not occur during a slow-moving translational slide, and it may not always be possible to accurately record the soil moisture condition. The use of raw acceleration data, which is the combination of linear and gravitational accelerations, for calculating tilt or motion is another drawback of the existing studies. Hence, there is a need for a better approach to monitor slides. This paper presents two methods to define movement thresholds and criteria to identify the translational soil slides based on our understanding of the sensor data recorded during the two laboratory experiments. BNO055 sensor devices (IMU sensors) with 3-axis accelerometers and 3-axis gyroscopes were selected for this study. The linear accelerations, gravitational accelerations, and angular velocities were utilized to understand the translational soil slides by correlating the sensor behavior to that of the slope. The interpretation of the movements during the failure at each sensor location was further verified by referring to the videos recorded by two pi-cameras. The outcomes of this study confirm the applicability of the proposed IMU sensor system and the movement thresholds for effective and reliable monitoring and warning of translational soil slides.

An Improved Data-Driven Approach for the Prediction of Rainfall-Triggered Soil Slides Using Downscaled Remotely Sensed Soil Moisture

The infiltration of rainwater into soil slopes leads to an increase of porewater pressure and destruction of matric suction, which causes a reduction in soil shear strength and slope instability. Hence, surface moisture and infiltration properties must be direct inputs in reliable landslide hazard assessment methods. Since the in situ measurement of pore pressure is expensive, the use of remotely sensed soil moisture is practically feasible. Downscaling improves the spatial resolution of soil moisture for a better representation of specific local conditions. Downscaled soil moisture, the relevant geotechnical properties of saturated hydraulic conductivity and soil type, and the conditioning factors of elevation, slope, and distance to roads are used to develop an improved logistic regression model to predict the soil slide hazard of soil slopes using data from two geographically different regions. A soil moisture downscaling model with a better accuracy than the downscaling models that have been used in previous landslide studies is employed in this study. This model provides a good classification accuracy and performs better than the alternative water drainage-based indices that are conventionally used to quantify the effect that elevated soil moisture has upon the soil slide hazard. Furthermore, the downscaling of soil moisture content is shown to improve the prediction accuracy. Finally, a technique that can provide the threshold probability for identifying locations with a high soil slide hazard is proposed.

Landslide susceptibility maps of Santiago city Andean foothills, Chile

The urban expansion of Santiago city includes areas with geomorphological and geological conditions with potential to be affected by landslide processes. This work presents compiled landslide susceptibility maps for the Andean foothills of Santiago city, between Maipo and Mapocho rivers. The maps identify the areas prone to the generation of slides, falls and flows. The results show that the oriental foothills of Santiago city have moderate to high susceptibility of rock falls, rock and soil slides and debris flows. The most important of these landslide types are debris flows, due to the runout of this processes that may reach urban areas posing a risk for the city, for which detailed hazard studies are required.

Characterizing the complexity of microseismic signals at slow-moving clay-rich debris slides: the Super-Sauze (southeastern France) and Pechgraben (Upper Austria) case studies

Abstract. Soil and debris slides are prone to rapid and dramatic reactivation. Deformation within the instability is accommodated by sliding, whereby weak seismic energies are released through material deformation. Thus, passive microseismic monitoring provides information that relates to the slope dynamics. In this study, passive microseismic data acquired at Super-Sauze (southeastern France) and Pechgraben (Upper Austria) slow-moving clay-rich debris slides (“clayey landslides”) are investigated. Observations are benchmarked against previous similar case studies to provide a comprehensive and homogenized typology of microseismic signals at clayey landslides. A thorough knowledge of the various microseismic signals generated by slope deformation is crucial for the future development of automatic detection systems to be implemented in landslide early-warning systems. Detected signals range from short-duration (< 2 s) quake-like signals to a wide variety of longer-duration tremor-like radiations (> 2 s – several min). The complexity of seismic velocity structures, the low quantity and low quality of available signal onsets and non-optimal seismic network geometry severely impedes the source location procedure; thus, rendering source processes characterization challenging. Therefore, we constrain sources' locations using the prominent waveform amplitude attenuation pattern characteristic of near-source area (< about 50 m) landslide-induced microseismic events. A local magnitude scale for clayey landslides (ML−LS) is empirically calibrated using calibration shots and hammer blow data. The derived ML−LS returns daily landslide-induced microseismicity rates that positively correlate with higher average daily displacement rates. However, high temporal and spatial resolution analyses of the landslide dynamics and hydrology are required to better decipher the potential relations linking landslide-induced microseismic signals to landslide deformation.