| Strong earthquakes can not only trigger a large number of landslides in mountainous areas,but also have an important impact on the development level of geological hazards in earthquake-affected areas after the major shake.Usually,the geological hazards triggered by strong earthquakes will be significantly enhanced and can continue for a long period of time,then returning to the pre-earthquake level.Therefore,studying the evolution characteristics of landslides in strong earthquake-affected areas is particularly important in disaster prevention.In this paper,Yingxiu,which was severely affected by strong earthquakes near the epicenter of the M_S8.0 Wenchuan earthquake in 2008,was selected as the research area.Multi-year(in April 2005,June 2008,April 2011,April 2013,May 2015,May 2017)high-resolution satellite images are used to interpret multi-temporal landslide inventories covering Yingxiu area of 66 km~2.We established 5 phases and 3types of databases for earthquake landslides,and we also obtained 7 major geological and geomorphic factors using the technology of Arc GIS platform,including elevation,slope,aspect,curvature,lithology,distance to the nearest river and fault.On this basiss,the methods of correlation analysis and regression are used to compare the intensity of landslide activity in different periods,the evolution law of landslide hazards triggered by Wenchuan earthquake was studied as well.Combining the above data and methods,the following conclusions are obtained:(1)From 2008 to 2019,the total area of landslides in the study area decreased from 21.41km~2 of co-seismic landslides in 2008 to 0.67km~2 in 2019.Overall,the number of re-actived landslides and new landslides decreased,indicating that the hazard activity level of the landslide after the earthquake has recovered or is close to the level before the earthquake.The area of landslide reduction is mainly concentrated in elevation 1000m to 2100m,slope 30°to 55°,slope direction 40°to 180°,curvature-2-2.In terms of lithological influence,the environment of the Pengguan complex in the study area is more prone to landslides,and the sedimentary clastic rock lithology is more conducive to the recovery of landslides;when the distance from the nearest water system is greater than 1600m,the influence of the water system on the landslide is gradually decrease.(2)Different geological and geomorphic factors have different effects on the evolution of landslides,and the influence factors and the differences between the factors on the development of landslides are different in different years.The above seven influence factors selected in this paper have different q values for the development distribution of landslides(q value means that an influence factor explains 100*q%of the landslide distribution specific to a certain year,which is also called explanatory power).In different years The most significant influence is elevation,especially as the time after the earthquake passes,the effect of faults on the distribution of landslides gradually decreases,and the explanatory power of elevation on the distribution of landslides increases year by year,reaching more than 20%in 5years,2017 The annual explanatory power is even as high as 78.5%.The interaction between factors can enhance the explanatory power of the development and distribution of landslides,of which the synergistic effect of elevation and aspect is the most significant.The superposition of curvature and water system greatly enhances the explanatory power of the distribution of landslides.In the management of earthquake-induced landslide disasters,the macroscopic control of slope physical factors and regional structural factors should be considered comprehensively.Based on the spatial distribution characteristics of landslides and the quantitative attribution conclusions of their influencing factors,this paper clarifies the focus of landslide disaster management in different natural years area.(3)The effect of the earthquake on the stability of the slope body in the study area is significant.After the earthquake,the study area has changed in terrain slope,static safety factor of slope body,and regional landslide risk.High-angle slopes are prone to displacement under the action of seismic loads,leading to the occurrence of landslides,which is more obvious for the improvement of landforms.In 2008,59.27%of the landslides occurred in 45.22%of the area and in high-risk areas.The results of the two are consistent,indicating that the Newmark model is feasible to assess the risk of landslides in the area.The effect of earthquakes has a greater impact on the results.Taking into account the parameter changes,the area ratio of landslides in high-risk and higher-risk areas increased from 59.27%in 2008 to 78.76%in 2011,compared with before the earthquake.The load acceleration required for the deformation of the slope body after the earthquake is smaller,and the slope body is more unstable. |
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