Study On Seismic Landslide Hazard Rapid Assessment Based On The Inventory Of Landslides Triggered By Wenchuan Earthquake

Earthquake triggered landslides is a common geological hazard.Because of its concealment,suddenness,clustering and destructiveness,it is easy to destroy the infrastructures and buildings and lead to casualties and property loss.Earthquake triggered landslide is one of the most serious hazard in China which could cause a wide range and huge destructiveness,especially in the Sichuan-Yunnan region.Because of neotectonic movements and seismic activity,landslide hazards caused by earthquakes are even more frequent and intense in the past decade.The Newmark displacement method is a typical deterministic method which was based on the mechanical model.Utilizing the earthquake data and important factors such as rock strength parameters and terrain slope data,this method can rapidly quantify the risk of landslides.It not only can satisfy the efficiency of assessment,but also can guarantee the reliability of evaluation as much as possible.According to the characteristics of rapid assessment during the earthquake emergency phase and basing on the actual landslide survey data and the simplified Newmark method,this paper focuses on the methodology and application of rock-soil strength parameters and critical sliding displacement in rapid landslides hazard assessment study.The main results are as follows:1.Based on the simplified Newmark method,a technical procedure for the seismic landslide hazard rapid assessment is developed in 11 counties which were severely afflicted in Wenchuan 8.0 earthquake.Given the geologic map,topographic slope data,static safety factor,critical acceleration(8 and the regional displacement of different intensities are calculated by Arc GIS spatial data modeler tools.Based on the intensity map produced by Shake Map system,rapid assessment of seismic landslide hazard in the areas of intensity impact is achieved.2.Based on the actual landslide survey data,the method for determining the rock-soil strength parameters in local regions is discussed.Taking Qingchuan County,Beichuan County and other six counties as the study areas,the landslides displacement which corresponds to the combination of rock-soil strength parameters of different rock groups are calculated.Comparing the landslide prediction area and the actual landslide point,reasonable value ranges of rock-soil strength parameters for different rock groups are determined.The analysis results of reasonable rock-soil strength parameters under different conditions,different intensities,and different rock groups indicate that: a).The positive correlation between reasonable values of rock-soil strength parameters of the same rock group and the intensity level is significant,the higher the intensity level,the greater the value of the combination of rock-soil strength parameters;b).The reasonable value range of rock-soil parameters of the same rock group in different regions and different intensity conditions is basically similar to the value range specified in the code,but the specific value is a little bit different.Given the above results,assigning one group of strength parameters to a rock group from specification range has limitation in rapid landslides assessment in local area.3.According to the determined rock-soil parameters,taking Qingchuan County,Beichuan County and other six counties six counties as the study areas,the reasonable range of critical displacement in the study areas is determined by comparing the landslide hazard zones with the actual landslide survey points,the reasonable range and the rule of critical displacement value are obtained as following: a).The analysis results of the reasonable range of critical displacement for the same rock group with different intensity levels indicate that the critical displacement of the same rock group in the study area shows a basic consistency within a certain range.The intensity has little effect on the critical displacement value;b).The higher the hardness and the better the integrity of the rock group is,the smaller the critical displacement value is.Therefore,using one critical displacement value as the criterion of the landslide instability of different rock groups will have a certain impact on the predicted results when the simplified Newmark model is used in landslides hazard rapid assessment,.The study in this paper provides a technical support for the construction of an automated output system for earthquake emergency products and provides a data support for the establishment of the regional geotechnical strength parameter database.The conclusion can be provided as a good reference for improving the accuracy of landslides rapid assessment.