潜在地震滑坡危险区区划方法

Hazards zonation for potential earthquake-induced landslide area

不同地区地震活动的强度和频率是不同的.基于地震危险性分析的地震滑坡危险研究在综合了地震烈度、位置、复发时间等因素的基础上,考虑了地震动峰值加速度时空分布的特点,可以有效地应用于潜在地震滑坡危险区区划.以汶川地震灾区为研究对象,根据研究区的地质构造、地震活动特点等划分出灾区的潜在震源区,对该区进行地震危险性分析,并在此基础上采用综合指标法做出基于地震危险性分析的地震滑坡危险性区划.所得地震滑坡危险性区划按照滑坡危险程度分为高危险、较高危险、较低危险和低危险四级,表示未来一段时间内研究区在遭受一定超越概率水平的地震动作用下,不同地区地震滑坡发生的可能程度.本文给出的地震滑坡危险性区划结果中,汶川地震滑坡崩塌较发育的汶川、北川、茂县等部分区域均处于高危险或较高危险区域;在对具有较高DEM精度的北川擂鼓镇地区所作的地震滑坡危险性区划中,汶川地震中实际发生的地震滑坡灾害与地震滑坡危险区划结果表现出较好的一致性.对区域范围而言,基于地震危险性分析的地震滑坡区划,可为初期阶段的土地规划使用及重大工程选址提供参考.

Earthquake-induced landslide is different from landslide triggered by rainstorms.Compared with landslides caused by rain,landslides induced by earthquake have more wide and dense space distribution and bigger scale,and can cause tremendous loss both to properties and lives.Earthquake-induced landslides usually cannot be prevented by current mitigation measures,thus,it becomes more and more important to develop a useful skill of assessing the hazard of landslides triggered by earthquake for land planning.This paper presents a method for zonation of potential earthquake-induced landslide area based on seismic hazard analysis.The approach takes account of uncertainty about earthquake location,intensity and recurrence,as well as space distribution of seismic peak ground acceleration.The study selects the damaged region in 2008.5.12 Wenchuan Earthquake as target area,and divided potential seismic source zone on the studying of geology,tectonics and seismic activity in this region.On the basis of potential seismic source zone division,this paper calculates the seismic peak ground acceleration according to different probability of exceedance of 10%,5% and 2% in 50a using seismic hazard analysis method proposed by Cornell in 1968,and then assesses earthquake-induced landslide hazard of study region with comprehensive indexes model.In this model,the hazard is classified into 4 grades as high,secondary high,secondary low and low,and five indexes are used including seismic peak ground acceleration,slope angle,rock type,and distance to faults and rivers.The result of hazards zonation for potential earthquake-induced landslide in the study area shows that landslide areas in Wenchuan earthquake such as Wenchuan county,Beichuan county,Maoxian county et al,are located at areas of high or secondary high grades.In Leiguzhen area of Beichuan county,where high resolution DEM data is available,the zonation result shows good correlation with reality.The assessed result can be used as reference for primary land planning and site choosing for great projects.