自然灾害风险评估与分级方法论探研——以山西省地震灾害风险为例

Methodology for assessment and classification of natural disaster risk:A case study on seismic disaster in Shanxi Province

自然灾害发生的可能损失一直是灾害风险评估上的难题。本研究以自然灾害风险评估经典模型为基础,提出了新的自然灾害风险评估与风险等级划分方法,利用历史灾情和孕灾环境解决风险评价中致灾因子破坏力与灾害发生的可能,并以山西省地震灾害风险为例进行了定量化评估研究。主要改进在于:确定灾害损失率和环境参数以建立地震灾害可能损失计算模型,计算承灾体地震灾害风险的可能损失量;用标准差和对数位转换的相关计算对地震灾害风险等级进行划分。案例结果显示:山西全省发生地震灾害,可能损失风险包括房屋破坏风险超过3百万间,经济损失风险超过130亿元,人员伤亡风险将近30万人。山西省各县市之间地震灾害综合风险差异明显,最高风险区域是太原市辖区、大同市辖区、晋中市辖区等15个县市区。

The study on possible losses is one of the most important points for disaster risk management.In this paper,the classical disaster risk-assessing model was modified to assess natural disasters risks,especially in quantifying possible loss and risk severe level.Disaster risk was attributed to three main factors： disaster damage force（D）,disaster resilience society exposure（E）,and disaster-breeding environment（P）.Disaster risk is the function of these three factors.Damage force（D） indicates damage rate of a disaster in a certain intensity,which might be obtained from results of disaster events in the past.Exposure（E） includes mainly personnel,property/economic and natural resources.D and E give the quantified vulnerability of a region.Disaster-breeding environment（P） gives the occurrence possibility of environmental conditions,such as geological structure,land surface materials,land cover,and cycling occurrence event etc.P was characterized by a parameter in this paper.Shanxi Province,a high frequent earthquake region,was taken as a case study.In the case,D and E were concerned with issues of structure of buildings,casualty rate（mortality/wounded） and GDP.Parameter of P was determined by combining historical seismic integrated intensity,seismic activity fault belts distribution,and seismic peak ground acceleration.The basic risk calculating unit was based on the county level.After possible losses were calculated,integrated loss levels and their severe levels were ranked with relative calculation on standard deviation.The results showed that： the damaged building might be more 3 million rooms,the direct economic loss would be over 13 billion RMB Yuan,and the total casualty could be near 300 thousand.In Shanxi Province,there were great differences between counties in terms of the integrated risk.Integrated risk levels were ranked into four classes.In general,high risk would mainly occur in urban areas.The highest risk level was observed in districts under the jurisdiction of 15 cities such as Taiyuan,Datong and Jinzhong.This method has improved in two aspects： firstly quantifying possible losses,and secondly avoiding the constraint in disaster prediction to make the calculation possible.