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Wu S.R.,Key Laboratory of Neotectonics and Geohazards | Wu S.R.,Geomechanics Institute of China Geological science | Shi J.S.,Key Laboratory of Neotectonics and Geohazards | Shi J.S.,Geomechanics Institute of China Geological science | Wang H.B.,Huazhong University of Science and Technology
Environmental Earth Sciences | Year: 2012

Activity intensity for swarms of landslides is a key issue in geohazard predictions and assessment at a regional scale. From reviewed literatures, little work has been carried out on the description of activity intensity and its evaluation indicator system. On May, 12, 2008, the great Wenchuan earthquake triggered numerous landslides and debris flows. To evaluate the activity intensity of coseismic landslides, a variety of regional slides, debris flows and rock falls was investigated concerning the geological characteristics, damage to property, and life loss. After the interpretation using high-resolution imagery to map landslide inventories, they were statistically analyzed within the scope of Geographical Information Systems, noting areal density. The maximum areal density was thus obtained for seismically triggered landslides. Combined analyses in these areas show that the maximum value of areal density can be described as the activity intensity of regional landslides. The activity intensity can be categorized into eight levels from zero to seven in terms of areal density of landslides. It was noted that the activity intensity for landslides in the area hit by Wenchuan earthquake was classified into Level 7, illustrating that this area was extremely damaged by these coseismic geohazards. Following this classification, the center of the highest intensity was located on the banks of the Minjiang River near the epicenter of the earthquake, and in the vicinity of a seismic fault at Hanwang Town of Mianzhu City. Meanwhile, the banks of the Jian River and the northeast river at Nanba Town in Pingwu County were classified into Level 6. It was significantly shown that the activity intensity obviously weakens from the boundary of a coseismic fault zone to its interior. Finally, causes of triggering large numbers of landslides were interpreted, and their regional distribution was analyzed for the earthquake event. © 2011 Springer-Verlag. Source

Wang H.B.,Huazhong University of Science and Technology | Wu S.R.,Geomechanics Institute of China Geological science | Shi J.S.,Geomechanics Institute of China Geological science | Li B.,Geomechanics Institute of China Geological science
Natural Hazards | Year: 2013

Landslides are presented in various types; some of which are unique or completely different from those in other countries due to geological conditions in China. Baoji City in Shaanxi Province, as a study area, is intensely affected by loess slope movements, triggered by directly intensive rainfall and indirectly by human activities. This paper provides a framework for the development of a Geographical Information System-based procedure to qualitatively assess landslide risk at a medium scale of 1: 10,000. For environmental factors affecting landsliding in the study area, erosion of river made great contribution to the occurrence of paleo-slides and old slides, while rainfall and human activities were triggers for the presence of recent landslides. The qualitative susceptibility assessment was studied in terms of slope instability using slope units, and regional-scale hazards were then analyzed by incorporating the type of landslides with susceptibility. From the landslide susceptibility analysis, almost 75% of slopes were classified as high susceptibility, in which five slopes were recently reactivated. It was noted that only 6 old landslides were categorized into high levels of hazard in case of rainfall, after assessment by combining susceptibility with types of landslides. Finally, landslide risk analysis was qualitatively made in an automatic way within the GIS, crossing the hazard map and the map of consequences to property. © 2011 Springer Science+Business Media B.V. Source

Wang H.B.,Huazhong University of Science and Technology | Zhou B.,Huazhong University of Science and Technology | Wu S.R.,Geomechanics Institute of China Geological science | Shi J.S.,Geomechanics Institute of China Geological science | Li B.,Geomechanics Institute of China Geological science
Natural Hazards and Earth System Science | Year: 2011

Landslides are one of the most common geologic hazards in the Loess Plateau of northwest China, especially with some of the highest landslide densities found in Shaanxi and adjacent provinces. Prior to assessing the landslide hazard, a detailed landslide inventory map is fundamental. This study documents the landslides on the northwest Loess Plateau with high accuracy using high-resolution Quickbird imagery for landslide inventory mapping in the Changshou valley of Baoji city. By far the majority of landslides are in loess, representing small-scale planar sliding. Most of the large-scale landslides involve loess and bedrock, and the failure planes occurred either along the contacts between fluvial deposits and Neogene argillites, or partially within the bedrock. In the sliding zones of a large scale landslide, linear striations and fractures of the soils were clearly developed, clay minerals were oriented in the same direction and microorganism growths were present. From the analysis of microstructure of sliding soils, it is concluded that the Zhuyuan landslide can be reactivated if either new or recurring water seepage is caused in the sliding surface. It can be concluded that most landslides are attributed to the undercutting of the slope associated with gullying, and numerous ancillary factors including bedrock-loess interface, slope steepness, vegetation cover and land utilization. © 2011 Author(s). Source

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