Major Landslide Research Articles

Risk assessment using quantitative approach: Central Himalaya, Kullu, Himachal Pradesh, India

Himalayan region has actively shown major landslide events in the last two decades. Therefore, risk assessment has been carried out in the study area to assess the risk to anthropogenic activities. The practice of risk assessment is important for rationalizing decision making in the process of development. The growing population, development of infrastructure, and unscientific mining activity in the study area are major factors responsible for majority of landslide incidences. An inventory has been developed for 142 landslides through interpretation of Google Earth image and satellite images [LISS-IV and Carto-sat], frequent field visits and past records of slope failures from various agencies. Thematic layers of all important factors [i.e., relative relief, slope, aspect, geology, soil, land use/land cover, landslide density, and drainage density] were prepared to study the factors responsible for mass movement along the slopes. These thematic layers were produced at a scale of 1:20,000 by using different sources of data in the GIS environment. Hazard zonation of the study area was carried out by using frequency ratio method, and risk assessment was done by using fuzzy logic method. Assessment of landslide vulnerability [probability of damage] was worked out from land use map. Both hazard and land use maps were reclassified and tabulated with the landslide inventory to identify the vulnerability of land use and risk. Based upon various factors, hazard zonation map of the study area is divided into five zones [very high, high, moderate, low, and very low hazard zones], whereas risk assessment is mainly divided into three zones[high-risk zone comprises 1.2% area, while 1.57% area under moderate risk zone and 97.21% area under low-risk zone].

Landslides assessment using geophysical and passive radon exhalation detection techniques in Murree Hills, northern Pakistan: Implication for environmental hazard assessment

Geophysical investigation of three landslides in Murree Hills was carried out using geophysical techniques (i.e., seismic refraction and electrical resistivity) and geochemical tool (passive radon exhalation detection method). The seismic data was acquired by using reverse shooting scheme employing placement of source after the last active geophone in the spread. The acquired data was analyzed, and layer velocities were estimated by using Hagedoorn’s method. The resistivity data was modeled in terms of true resistivity of subsurface material by curve matching technique. The radon emission was determined as alpha track densities for each detector planted in dosimeter in the sub-surface along survey profiles. The results of all the methods employed were interpreted and correlated in the context of local geology, and also considering seasonal and anthropogenic factors. The study guides the importance of local geological structure and lithologies in the formation of thick weathering layer. The weathered layer wet/moistened through rains in the winter and summer seasons or daily use of water due to urbanization of the area, exerts more downslide force thus resulting landslides. This thickness of weathered layer is determined by using seismic refraction and resistivity methods for the three landslides (MIT, Kuldana and Chitta Mor) which is in agreement. Also, the passive radon exhalation detection technique (geochemical investigation) has delineated the stable and unstable areas within the three landslide zones. These geophysical and geochemical investigations are recommended on the major landslides of the area prior to damage control measures.

Rainfall-Induced Slope Failures and Use of Bamboo as a Remedial Measure: A Review

Problems due to slope instability during rainfall season can cause major landslides occurrences. Different rainfall intensities and duration affect the slope in different manners. To counter this problem, numerous studies have been carried and many innovative techniques have come up on how to stabilize the soil so as to ensure stability. The different techniques involve chemical stabilization, retaining walls, vegetation, different methods of reinforcements, etc. Most of these methods are proving to be fatal to the environment; hence, sustainable methods of reinforcements are the latest area of interests. Bamboo has been widely used as a reinforcement material for soil stabilization. This paper presents the current state of art on the application of bamboos in the stabilization of landslide caused due to rainfall. Bamboo can be used in many forms and has proven to be effective in almost all its forms. Various ways that a bamboo can be used as reinforcements are studied in detail.

A diagnostic study of extreme precipitation over Kerala during August 2018

AbstractThe state of Kerala, located on the west coast of India, experienced a record 100‐year flood that resulted in major landslides from unprecedented prolonged and extremely heavy rainfall (50–480 mm·day−1) during August 1–19, 2018, causing extensive damage and about 500 causalities. Rainfall observations indicate that the heavy rainfall occurred over two spells (August 7–10 and 14–18) in association with an offshore trough, and a depression over the Bay of Bengal (BOB). High‐resolution 38‐year climatology data (5 km) and the ERA‐Interim reanalysis dataset show a strong low‐level jet over the Arabian Sea and a depression over the BOB with a southwestward tilt during the heavy rainfall. Very high‐resolution (2‐km) mesoscale model simulations suggest that this high convective instability due to the strong westerly jet along with the formation of offshore vortex, the transport of mid‐tropospheric moisture under the presence of conducive vertical shear of horizontal wind, and transport of mid‐tropospheric moisture from the BOB are the major factors (as shown in the schematic diagram) behind the extreme heavy rainfall over Kerala.

Retrospective deformation of the Baige landslide using optical remote sensing images

Detecting slope deformations before major landslides is crucially important for mitigating landslide disasters. In this work, we explored the use of Sentinel-2 images and an image correlation method, Co-Registration of Optically Sensed Images and Correlation (COSI-Corr), to derive slope deformations before the 2018 Baige landslide along the Jinsha River. We found that larger sliding windows outperform smaller ones in extracting the moving slope. Different solar zenith angles in image pairs have an influence on the derived displacements. Although the spatial resolution of Sentinel-2 images is 10 m, uncertainties in estimating slope deformation are found within 2 m. Using the COSI-Corr technique, we monitored sub-pixel slope deformation in Sentinel-2 images from November 2015 to August 2018. We found that the slope moved faster in summer than in winter months, which was probably driven by the monsoon climate in this region. From 2015 to 2018, the slope movement became faster, and an acceleration stage was observed before the slope failed completely. To derive reliable slope displacements, this work suggests testing different sliding window size combinations in the use of image correlation methods, and optical images acquired with similar zenith angles are preferred. This work also demonstrated the capability of using optical remote sensing images to monitor large slope deformations before major landslides. As more optical images with high spatial resolution become available, monitoring minor slope deformations directly would be practicable for large remote mountain regions.

Prediction of a multi-hazard chain by an integrated numerical simulation approach: the Baige landslide, Jinsha River, China

Successive major landslides during October and November 2018 in Baige village, eastern Tibet, dammed the Jinsha River on two occasions, and the subsequent dam breaches instigated a multi-hazard chain that flooded many towns downstream. Analysis of high-resolution aerial images and field investigations unveiled three potentially unstable rock mass clusters in the source area of the landslides, suggesting possible future failures with potential for river-damming and flooding. In order to evaluate and understand the disaster chain effect linked to the potentially unstable rock mass, we systematically studied the multi-hazard scenarios through an integrated numerical modelling approach. Our model begins with an evaluation of the probability of landslide failure, including runout and river damming, and then addresses the dam breach and resultant flood—hence simulating and visualising an entire disaster chain. The model parameters were calibrated using empirical data from the two Baige landslides. Then, we predict the future cascading hazards via seven scenarios according to all possible combinations of potential rock mass failure. For each scenario, the landslide runouts, dam-breaching, and flooding are numerically simulated with full consideration of uncertainties among the model input parameters. The maximum dam breach flood extent, depth, velocity, and peak arrival time are predicted at sequential sites downstream. As a first attempt to simulate the full spectrum of a landslide-induced multi-hazard chain, our study provides insights and substantiates the value provided by multi-hazard modelling. The integrated approach described here can be applied to similar landslide-induced chains of hazards in other regions.

Landslide risk assessment: human activities influence on an agriculture catchment

A disaster is an event that can cause damage, loss of human life, or environmental damage. One of the disasters that often occurs in the upstream area is landslides. Karangkobar is one of the regions in the upstream area that had experienced a major landslide at 2014 which is resulted in 105 houses buried in land and 95 people were dead. The landslide disaster that has occurred in the Karangkobar catchment area is caused by the topography of the hills, high slopes, thick soil solum, soil texture is clay, cropping pattern and treated land that is inconsistent with conservation rules. This shows that landslide in the Karangkobar catchment area not only caused by natural conditions, but also human activities have an influence on the land. This research aimed to analyze the risk of landslide disaster based on hazard, vulnerability and capacity aspects in the Karangkobar catchment area. Assessment of risk analysis made by overlay between Hazard, Vulnerability, and Capacity is then given scores and weights. Overlay created with Arc Gis 10.4.1, scoring is given to assigning values to each parameter disaster. Weighting was analyzed by Analytical Hierarchy Process (AHP) with pairwise method and Expert Choice V.11 software, Weighting determined based on AHP scale. The result showed that the percentage of landslide risk based on human activity in the Karangkobar catchment are 41,16 % high risk, 38,04 % medium risk, and 14,47% low risk.

Mapping of shallow landslides with object-based image analysis from unmanned aerial vehicle data

The Black Sea Region of Turkey is one of the most landslide prone areas due to its high slope topography, heavy rainfall, and highly weathered hillslope material conditions. Preparation of landslide inventory maps is the first step in producing landslide susceptibility maps. Ground-based methods for mapping landslide occurrences are time-consuming and expensive. Additionally, landslide mapping based on satellite imageries and aerial photographs has some limitations, including climatic conditions, cost, and limited repetitive measurement capacity. Visual interpretation-based landslide mapping, which is based on satellite imageries and aerial photographs, is a time-consuming procedure that requires an experience-based expert opinion. Therefore, the data acquisition based on unmanned aerial vehicle (UAV) and landslide event inventory maps using an object-based classification approach can be superior to other methods in terms of speed and cost. In this study, we developed a semiautomatic model using object-based image analyses for rapid mapping of shallow landslides from the data obtained from UAVs after major landslide events in the Black Sea Region of Turkey. For this purpose, two test sites—Kurucasile (Bartin) and Cayeli (Rize)—were selected. Landslide mapping models were developed in the investigation sites, and the performance of the models was evaluated. The landslides' data obtained with the developed models were compared to the landslides' data produced by the experts. The comparison process revealed that landslides mapped by using UAV data have an accuracy rate higher than 86% according to the number of landslides and 83% according to the landslide area.

Housing, water and sanitation implications on food insecurity and diet diversity in landslide affected communities: A cross-sectional survey of two districts in Uganda

The major landslide of 2010 in Bududa district in Eastern Uganda is the most catastrophic natural disaster in Uganda's recorded history. An estimated 350 people died and some of the affected were resettled in Kiryandongo district. We assessed housing, water and sanitation practises of affected households and controls to establish possible implications on food insecurity and diet diversity. This cross-sectional study assessed 1078 affected and control households in Bududa and Kiryandongo districts. The head of the households were either affected, selected from landslide disaster-affected communities, or controls from a random sub-county bordering the affected. Structured interviews were used and entries were tested statistically to report crude estimates based on the Pearson x2 and ANOVA, while adjusted analysis used multivariate analysis of co-variance (MANCOVA) and Wald's Odds Ratio (OR) of Binary Logistic Regression at the 95% CI. On adjusting for the disaster and covariates, households who had insufficient access to water scored higher mean (SE) on food insecurity than those who reported sufficient access: 13.1 (0.4) vs. 9.5 (0.3) (P<0.01). Intriguingly, households who owned a toilet and those who reported always using soap to wash hands scored higher food insecurity than their counterparts: 11.1 (0.3) vs. 9.0 (0.6) (P<0.01) and 11.3 (0.3) vs. 9.1 (0.5) (P<0.01), respectively. However, not owning a toilet increased the likelihood of being food insecure (OR 3.43; 95% CI 1.31, 8.97; P=0.02). In Kiryandongo, affected households scored higher food insecurity than controls: 9.5 (0.5) vs. 5.4 (0.5) (P<0.01) and higher diet diversity scores (DDS): 6.7 (0.2) vs. 6.2 (0.2) (P=0.04). Type of housing also predicted food insecurity (P<0.01) and DDS (P=0.03). Like Bududa, households with insufficient water access scored higher food insecurity while those owning toilet scored higher DDS. Uniquely, only number of rooms was linked to a high likelihood of being food insecure (OR 1.60; 95% CI 1.19, 2.15; P<0.05). Disaster, food security and diet were sensitive to housing, water and sanitation and were integral to an adequate standard of living of victims of this landslide.

PS-driven inventory of town-damaging landslides in the Benevento, Avellino and Salerno Provinces, southern Italy

ABSTRACT The Apennine provinces of Campania Region (southern Italy), Benevento, Avellino and Salerno, are known for their ‘unstable towns’ suffering periodic damage from landslides. Their identification and mapping are very challenging tasks, since boundary mapping under urban settlements is not always possible without time-consuming field analysis of building damage and/or expensive mid-term diffuse ground-surface deformation monitoring. To overcome this problem, an inventory of town-damaging landslides, guided by available Permanent Scatterers (PS) ground-deformation data, was prepared. It provides an updated tool suitable to guide future land planning and historical site restoration in the Apennine provinces of Campania Region. Our fourteen Map Sheets show active and local reactivation of suspended/dormant landslides. Overall, 356 landslides were identified, amongst which 162 were identified as flows, 101 as slides, 1 as a spreads and 92 as complex landslides. To supplement our maps, a simplified distribution analysis based on major landslide morphometric characteristics was completed.

DISCUSSION ON FAILURE MECHANISM FOR COMPLEX MOVEMENT OF SHUIMATUO LANDSLIDE IN GUIZHOU PROVINCE

At the beginning of 2011, affected by multi-periods of heavy rainfall, many geohazards were developed on the accumulated layer slopes in Shuimatuo Town, Sinan County. They include ground surface rupture, wall inclination, deformation aggravation of fissures on ground and walls. Once influenced by the heavy rainfall and other unfavorable factors, the unstable slopes would slide continuously, posing a serious threat to the 509 persons and 556 houses of Datong Community, and a significantly negative impact to the local society. Based on the field survey and indoor analysis, this paper elaborates the geo-environmental characteristics of the Shuimatuo landslide region and clarifies the important effects of geological structures and topographic conditions to the seepage field of the slope. With the help of local meteorological data, we continue to research the deformation and failure process of the slope under the rainfall condition with the SEEP/W module and the FLAC3D software. We preliminarily expound the formation mechanism of the thrust-type landslide(H1) and secondary tractive landslide(H2)triggered by the multi-period of rainfall. The preliminary research results believe that induced by the rare heavy rainfall in the history, the major landslide begins to deform, but limited by the terrain condition, showing characteristics of part and progressive failure. During the long-term creep deformation process of landslide, rainfall causes a fluctuation of the groundwater level, strengthening the creep of sliding mass. Controlled by the free surface condition, the evolutionary process of secondary tractive landslide shows obvious correlation and certain lag comparing to the major landslide. For the thrust-type accumulated layer landslide, affected by the terrain, groundwater and loading conditions, it takes a long time from strength decrease of sliding belt to the formation of sliding plane. While tractive accumulated layer landslide lasts shortly as it is a backward movement generated by slope stress redistribution due to the lack of key anti-slide body.

Geomorphologic and Glacial Evolution of the Cachapoal and southern Maipo catchments in the Andean Principal Cordillera, Central Chile (34°-35º S)

We present here a reconstruction of the post late Miocene landscape evolution of the western slope of the Andean Cordillera Principal near 34°20’ S. We base our analysis on the available geological information, a morphological characterization of the landform assemblages in the Cachapoal and southern Maipo catchments, and the first 10Be exposure ages for moraines in this area. The Cachapoal drainage basin is characterized by a variety of morphological features, like an elevated low-relief surface, volcanoes and lava flows on valley slopes, U-shaped valley sections, roches moutonnées, and large glaciated areas. Different kinds of deposits have been included in the study, such as moraines, lacustrine and landslide deposits, and a well-developed system of fluvial terraces in the more distal part of the Cachapoal catchment. Landslides are mostly developed on rocks of the late Eocene-early Miocene Abanico Formation. and are less frequent in outcrops of the overlying, early to middle Miocene Farellones Formation. We estimate that the lowest end moraine in the Cachapoal catchment is located next to the locality Bocatoma Chacayes (~950 m altitude), though covered by a major landslide. No evidence exist for glacial deposits further down stream in this region. Lateral moraine ridges of the Cachapoal Glacier at Los Cerrillos yielded 10Be exposure ages of 20.3±2.9 and 21.9±5.3 ka that indicate they are associated with the Last Glacial Maximum (LGM). Holocene moraines exist next to all glacier tongues. Of particular interest in this region is the 12 km-long debris-covered Cachapoal Glacier, the longest valley glacier in the central Chilean Andes, and its distal and proximal moraine deposits. Two lateral moraines adjacent to the present-day Cachapoal Glacier yielded exposure average ages of 13.5±2.4 ka for the external ridge, indicating the Younger Dryas, and 3.8±0.8 ka for the internal ridge, an age that coincides with the 4.2 ka global climatic event that marks the beginning of the Meghalayan Age, at the end of the Holocene. The large size of this moraine on both sides of the ice tongue indicates the great development of the glacier at that time. Some of these ages coincide with ages obtained further north in the Maipo drainage basin, at the latitude of Santiago, and in the eastern flank of the cordillera, however, no pre-LGM deposits were found here, unlike the other mentioned regions. This difference together with the much lower altitude of the LGM moraine deposits in the study region suggests that the Cachapoal catchment is a transition zone to a more humid region further south, and indicates the great need for further reconnaissance and dating of glacial deposits in this Andean region. Our analysis of the geomorphological evolution is consistent with incision start for the Cachapoal Valley in latest Miocene. In this process, glacier incision was apparently not much effective until mid-Pleistocene time, when volcanism was active in the higher regions of the mountain range covering areas not yet incised, whereas in the western Principal Cordillera lavas flowed in deeply incised valleys. Pleistocene glaciers deepened and shaped the already incised valleys, which are presently mostly occupied by rivers.

Centennial-scale process activity in a complex landslide body in the Qilian Mountains, northeast Tibetan Plateau, China

Mass movements in China typically encompass landslides, rockfalls, and debris flows, and these processes affect almost 70% of all mountain areas of China. An improved understanding of geomorphic process dynamics and their drivers and process histories are important prerequisites for a proper assessment and a sustainable management of mountain hazards. Tree rings have on varied occasions proven to be a reliable tool for the acquisition of data on past mountain hazards. Here we present the first reconstruction of past landslide activity on a slope in the Qilian Mountains, northeast Tibetan Plateau, China. To this end, a total of 543 Qilian juniper (Sabina przewalskii Kom.) samples were selected from 239 trees growing on or next to a complex landslide body, with the aim to reconstruct past landslide histories at the site. The dataset of disturbed trees was complemented with 174 increment cores from 84 reference Qilian juniper trees growing on three adjacent, yet undisturbed sites. Based on the dating of the samples and the interpretation of growth disturbances (GD) in the tree-ring series of affected trees, we provide the first reconstruction of past landslides as retrieved from a dendrogeomorphic record covering more than a millennium (956–2011 CE). Results show that the first detectable GD occurred as early as in 1042 CE, followed by seven major landslide reccurrences in 1703, 1816, 1848, 1863, 1913, 1970, and 1982. Comparison between our landslide record and a dendroclimatic precipitation reconstruction points to the crucial role of major, longer-term wet precipitation anomalies on landslide occurrence.

Landslide hazard assessment based on human activity in the upstream area

Hazard is an event that can cause damage, loss of human life, or environmental damage. One of the hazards that often occurs in the upstream area is landslides. Karangkobar is one of the region in the upstream area that had experienced a major landslide at 2014 which resulted 105 houses buried in land and 95 people were dead. The landslide disaster that has occurred in the Karangkobar catchment area is caused by the topography of the hills, high slopes, thick soil solum, soil texture, cropping pattern and treated land that inconsistent with conservation rules. This research aimed to analyse the hazard of landslide disaster based on physics and human activity aspects in the Karangkobar catchment area. Assessment of hazard analysis made by overlay between physics and human activity aspects then given scores and weights. Overlay created with Arc GIS 10.4.1 and scoring is given to assign values to each parameter disaster. The weighting was analysed by Analytical Hierarchy Process (AHP) with pairwise method and using Expert Choice V.11 software. The result showed that the percentage of landslide hazard in the Karangkobar catchment area based on physics are 42.06% low, 38.03 % medium, and 19.38 % high, while based on physics that combine with human activities are 34.64% low, 46.05 % medium, and 19.3 % high. This shows that total area for medium hazard was increase in the Karangkobar catchment area. It caused not only by natural conditions, but also human activities give effect on it.

Geoarchaeological Evidence of Middle-Age Tsunamis at Stromboli and Consequences for the Tsunami Hazard in the Southern Tyrrhenian Sea

Large-scale landslides at volcanic islands are one of the most dangerous geological phenomena, able to generate tsunamis whose effects can propagate far from the source. However, related deposits are scarcely preserved on-land in the geologic records, and are often difficult to be interpreted. Here we show the discovery of three unprecedented well-preserved tsunami deposits related to repeated flank collapses of the volcanic island of Stromboli (Southern Italy) occurred during the Late Middle Ages. Based on carbon datings, on stratigraphic, volcanological and archaeological evidence, we link the oldest, highest-magnitude investigated tsunami to the following rapid abandonment of the island which was inhabited at that time, contrary than previously thought. The destructive power of this event is also possibly related to a huge marine storm that devastated the ports of Naples in 1343 (200 km north of Stromboli) described by the famous writer Petrarch. The portrayed devastation can be potentially attributed to the arrival of multiple tsunami waves generated by a major landslide in Stromboli island, confirming the hypothetical hazard of these phenomena at a regional scale.

Operative Monographies: Development of a New Tool for the Effective Management of Landslide Risks

Active landslide risk assessment and management are primarily based on the availability of dedicated studies and monitoring activities. The establishment of decision support for the efficient management of active landslides threatening urban areas is a worthwhile contribution. Nowadays, consistent information about major landslide hazards is obtained through an interdisciplinary approach, consisting of field survey data and long-time monitoring, with the creation of a high populated dataset. Nevertheless, the large number and variety of acquired data can generate some criticalities in their management. Data fragmentation and a missing standard format of the data should represent a serious hitch in landslide hazard management. A good organization in a standard format can be a good operative solution. Based on standardized approaches such as the ICAO (International Civil Aviation Organization), we developed a standard document called operative monography. This document summarizes all available information by organizing monitoring data and identifying possible lacks. We tested this approach in the Aosta Valley Region (NW Italy) on five different slow moving landslides monitored for twenty years. The critical analysis of the available dataset modifies a simple sequence of information in a more complex document, adoptable by local and national authorities for a more effective management of active landslides.

Submarine Landslides and their Distribution in the Gas Hydrate Area on the North Slope of the South China Sea

Integrated investigations have revealed abundant resources of gas hydrates on the northern slope of the South China Sea (SCS). Regarding the gas hydrate research of northern SCS, the gas hydrate related environment problem such as seabed landslides were also concentrated on in those areas. Based on 2D seismic data and sub-bottom profiles of the gas hydrate areas, submarine landslides in the areas of Qiongdongnan, Xisha, Shenhu, and Dongsha have been identified, characterized, and interpreted, and the geophysical characteristics of the northern SCS region investigated comprehensively. The results show 6 major landslides in the gas hydrate zone of the northern SCS and 24 landslides in the Shenhu and Dongsha slope areas of the northern SCS. The landslide zones are located mainly at water depths of 200–3000 m, and they occur on the sides of valleys on the slope, on the flanks of volcanoes, and on the uplifted steep slopes above magmatic intrusions. All landslides extend laterally towards the NE or NEE and show a close relationship to the ancient coastline and the steep terrain of the seabed. We speculate that the distribution and development of submarine landslides in this area has a close relationship with the tectonic setting and sedimentary filling characteristics of the slopes where they are located. Seismic activity is the important factor controlling the submarine landslide in Dongsha area, but the important factor controlling the submarine landslides in Shenhu area is the decomposition of natural gas hydrates.

IDENTIFICATION OF LANDSLIDE SUSCEPTIBILITY ZONATION IN CNG GHAT SECTION, GUDALUR, THE NILGIRIS – USING GIS BASED ANN/MULTI CRITERIA METHOD

Abstract. Among the various natural hazards, landslide is the most widespread and damaging hazard. In recent times, throughout a lot of attention is being drawn to evaluate the risk due to landslides. The invention of remote sensing and GIS have been new vistas in the field of geo scientific studies viz. geomorphological mapping, groundwater potential mapping, disaster management etc. The present study has been undertaken to study different thematic maps like, contour, drainage, slope, aspect, curvature, DEM, DTM, drainage density, drainage intensity, geology, lineament, lineament density, lineament intensity, geomorphology, land use, weathering thickness, run off, soil thickness and buffer maps like road, drainage, lineament etc. in CNG ghat section, Gudalur, The Nilgiris. For this purpose, the satellite image IRS – RS2, LISS III January 2014 used to prepare different thematic maps. The contour, drainage and road network were incorporate from SoI Toposheets. The slope, curvature, aspects and buffer maps were prepared from GIS environments. Based on field studies, above said thematic maps (22 nos.) were prepared and were grouped into 3 categories viz. Geology, Hydrology and Terrain. In each category the input maps were assigned different score as well as each layer has been given different weightage. Finally the categories are analysed through multi – criteria analysis to find out 5 different vulnerability classes. The 5 different land susceptibility zones are classified as very low, low, moderate, high and very high. The percentages of area under different susceptibility classes are 3%, 20%, 51%, 25%, and 1% respectively. The locations of small area major landslides and slip locations were calculated from different years using (2010 and 2014) Trimble GPS in the field. The field data was converted into point layer in GIS and landslide inventory map was prepared. This map was superimposed in landslide susceptibility zonation map. As per field data 0%, 9.25%, 57.5%, 32% and 1.25% Slide points are come under very low, low, moderate, high, very high susceptibility zones respectively.

Probabilistic Evaluation of Fault Sources Based on Paleoseismic Evidence From Mass‐Transport Deposits: The Example of Aysén Fjord, Chile

AbstractContemporaneous mass‐transport deposits (MTDs) recorded in lake and fjord sediments provide evidence of past seismic shaking. However, because they are usually not connected to a fault rupture, assessment of the earthquake source remains difficult. Based on observed coseismic mass wasting and associated seismic shaking, previous studies assigned minimum intensities required to trigger them. Attempts to infer their earthquake source relied on methods developed to estimate the location and magnitude of historical earthquakes using intensity prediction equations, but considered these thresholds as actual intensities. Here we develop a probabilistic method to infer the most likely earthquake sources from the spatial distribution (or absence) of MTDs. This approach simultaneously allows the triggering intensity to exceed the assumed threshold and takes into account intensity prediction equation uncertainties, two shortcomings of existing methods. Additionally, we consider known active faults rather than a grid of possible epicenters. We apply this method to Aysén Fjord (southern Chile), which is intersected by the Liquiñe‐Ofqui Fault Zone. In 2007, an MW = 6.2 earthquake hit the fjord with intensities of VIII+, causing major landslides entering the fjord. Seismic‐reflection profiles show that its sedimentary fill contains nine prehistoric MTD levels. Following a sensitivity analysis, application of the method to the MTD record allows identifying the most likely fault sections and magnitude range for most events, confirming that they are mainly attributed to crustal earthquakes on the Liquiñe‐Ofqui Fault Zone. We conclude that the method has good potential to constrain the size and location of paleoearthquakes for which only shaking evidence is available.

Measuring decadal vertical land-level changes from SRTM-C (2000) and TanDEM-X ( ∼ 2015) in the south-central Andes

Abstract. In the arctic and high mountains it is common to measure vertical changes of ice sheets and glaciers via digital elevation model (DEM) differencing. This requires the signal of change to outweigh the noise associated with the datasets. Excluding large landslides, on the ice-free earth the land-level change is smaller in vertical magnitude and thus requires more accurate DEMs for differencing and identification of change. Previously, this has required meter to submeter data at small spatial scales. Following careful corrections, we are able to measure land-level changes in gravel-bed channels and steep hillslopes in the south-central Andes using the SRTM-C (collected in 2000) and the TanDEM-X (collected from 2010 to 2015) near-global 12–30 m DEMs. Long-standing errors in the SRTM-C are corrected using the TanDEM-X as a control surface and applying cosine-fit co-registration to remove ∼1/10 pixel (∼3 m) shifts, fast Fourier transform (FFT) and filtering to remove SRTM-C short- and long-wavelength stripes, and blocked shifting to remove remaining complex biases. The datasets are then differenced and outlier pixels are identified as a potential signal for the case of gravel-bed channels and hillslopes. We are able to identify signals of incision and aggradation (with magnitudes down to ∼3 m in the best case) in two &gt;100 km river reaches, with increased geomorphic activity downstream of knickpoints. Anthropogenic gravel excavation and piling is prominently measured, with magnitudes exceeding ±5 m (up to &gt;10 m for large piles). These values correspond to conservative average rates of 0.2 to &gt;0.5 m yr−1 for vertical changes in gravel-bed rivers. For hillslopes, since we require stricter cutoffs for noise, we are only able to identify one major landslide in the study area with a deposit volume of 16±0.15×106 m3. Additional signals of change can be garnered from TanDEM-X auxiliary layers; however, these are more difficult to quantify. The methods presented can be extended to any region of the world with SRTM-C and TanDEM-X coverage where vertical land-level changes are of interest, with the caveat that remaining vertical uncertainties in primarily the SRTM-C limit detection in steep and complex topography.