Study On Fuzzy Comprehensive Assessment Of Urban Earthquake-induced Geological Hazard Risk Of The Main Fault Zones In Southwest China

Occurred in the Longmen Shan Fault Zone, the Wenchuan Ms8.0, and LushanMs7.0earthquakes give us such a serious problem, which is namely that the townsdistributed in the other regional deep faults of southwest China, or wil face a seriousthreat to earthquake and its secondary geological disasters. Based on the twoearthquakes and other regional faults’ researches, we have established the assessmentindex system of urban earthquake-induced geological hazard risk, and usedAHP-Fuzzy comprehensive assessment method to calculate risk index for the22towns which were destroyed in the two earthquakes. Combining with the actualcondition, we have finally constructed the standard of urban earthquake-inducedgeological hazard risk rank. Researches have made progress in the following areas:(1)"Wenchuan Earthquake" and "Lushan Earthquake" show that in the towns ofsouthwest mountains, the main types of earthquake-induced geological disasters arelandslides, collapses, debris flows, shattered mountain bodys and barrier lakes etc.(2)The assessment index system of urban earthquake-induced geological hazardrisk includes risk evaluation index system and vulnerability assessment index system.Risk is mainly controlled by the geological environment characteristics of the towns’surrounding, fracture and earthquake. Thus we selected slope, relative elevation,landforms, lithology and its full extent, slope type, etc, the sixteen indicatorscomposing risk evaluation index system. The vulnerabilities include populational andsocial vulnerability, physical vulnerability, resources and environmental vulnerability,and economic vulnerability. Based on the previous research and actual condition, weselected population density, dependency ratio, the government’s emphasis ongeological disasters, the transportation routes’ density, the number of hospital beds, GDP Per capita, deposits and urban fixed asset investment, the eight indicatorscomposing vulnerability assesment index system.(3)On the basis of the establishment of urban earthquake-induced geologicalhazard risk assessment index system, we constructed the AHP-Fuzzy comprehensiveevaluation model.(4) According to the loss, the ranks of urban earthquake-induced geologicalhazard risk are mainly divided into very low risk, low risk, high risk and very highrisk. We constructed the standard of urban earthquake-induced geological hazard riskrank, in which the risk index R ranged (0，0.4) is in extreme low risk, the risk index Rranged (0.4，0.5) is in low risk, the risk index R ranged (0.5，0.6) is in high risk, andthe risk index R ranged (0.6,1) is in extreme high risk.(5)Based on the standard of risk rank by "Wenchuan Earthquake" and "Lushanearthquake", we have used AHP-Fuzzy comprehensive evaluation method on thetowns of many other Fault Zones, such as Xianshui River Fault Zone, Anning RiverFault Zone, Zemu River Fault Zone, Xiaojiang Fault Zone and Red River Fault Zone.And the results are consistent with the objective situation.