汶川8.0级地震地表破裂迹线附近建筑物的震害分布

Distribution of Seismic Damaged Buildings along the Trace of Ground Surface Rupture Caused by the Ms 8.0 Wenchuan Earthquake

摘要: 汶川地震地表破裂带主要分三部分，映秀–北川地表破裂带、通济–雎水地表破裂带、以及小鱼洞地表破裂带。映秀–北川地表破裂带是汶川地震的主要破裂带，处于龙门山中央断裂带上，全长达260 km以上；通济–雎水地表破裂带是汶川地震在前山断裂带上产生的地表破裂，全长约50 km；小鱼洞破裂带，是主断裂带上的一个分支，从小鱼洞经草坝，延伸至向峨，破裂带由北西向逐渐过渡到南西向，全长约6 km。已发现的最大同震位错位于主破裂带的都江堰虹口附近，最大垂直位错4.8 m、最大水平右旋位错4.7 m。本文以南坝镇地震地表破裂点附近的建(构)筑物震害调查为例展开，此段地表垂直位错0.5~2.5 m，水平位错1.3~2.0 m，地表强变形带宽度7.6~18 m；相应地，50 m范围内的房屋完好率为0，倒塌率为0.424，中等破坏与严重破坏率为0.576。沿地表破裂带上的15个乡镇的1699栋建(构)筑物震害表明，在距地表破裂迹线距离为150 m范围内的建筑物的倒塌率逐渐下降，即从0.33193降低到0.29264；在距地表破裂迹线距离为250 m范围内的建筑物的完好率逐渐上升，即从0.08824上升到0.1248；超过这样的区域，倒塌率和完好率趋于平缓。从震害指数角度，可以发现，在距地表破裂迹线距离为150 m范围内的建筑物的震害指数逐渐下降，即从0.72降低到0.47344；超过这样的区域，震害指数规律性不明。

Abstract: Field investigations of the Ms 8.0 Wenchuan Earthquake show that buildings on the ground surface rupture zone were severely damaged. The surface rupture zone consists of three parts. Two of the parts are respectively along the trace of the Beichuan-Yingxiu fault and the Guanxian-Jiangyou fault. The former part is about 260 km long, which starts at Yingxiu and terminates at Nanba; the latter part is about 50 km long which starts at Tongji and terminates at Jushui. The third part connects the Beichuan-Yingxiu fault and the Guanxian-Jiangyou fault from Xiao Yudong, to Tongji, which is about 6 km long. The maximum vertical and horizontal offset of 4.8 m and 4.7 m, respectively, were observed along the Beichuan-Yingxiu fault, whereas a maximum vertical offset of 3.5 m occurred along the Guanxian- Jiangyou fault. The distribution of damaged buildings along the trace of ground surface was investigated in many segments. The seismic damage distribution in Nanba area will be introduced considering that lots of rural residents live there. Vertical and horizontal offset of 0.5 - 2.5 m and 1.3 - 2.7 m, respectively, were observed along this segment, and the significant width of deformation caused by the offset is 7.6 - 18 m. In this segment, the building of intact ratio is zero, the ratio of medium to the serious damage is 0.576 and the collapse ratio is 0.424 within 50 m. Totally 1699 structures were investigated in 15 segments along the ground surface rupture zone. The collapse ratio decreases from 0.33193 to 0.29264 corresponding to the fault distance 0 to 150 m. Here the fault distance is defined as a distance from location of structure to the trace line of rupture points; the building of intact ratio increases from 0.08824 to 0.12480 corresponding to the fault distance 0 to 250 m. In other way, earthquake damage index of building structure decreases from 0.72 to 0.47344 corresponding to the fault distance 0 to 150 m. There is no significant regularity beyond 150 m.