汶川地震地表破裂带宽度与断层上盘效应

以汶川地震产生的地表破裂宽度为研究对象, 以地表微变形、裂隙和鼓包、叠瓦状断层及反冲断层等为标志界定破裂的宽度, 查明中央破裂带和前山破裂带宽度的分布。结果表明, 中央断裂带与汉旺?白鹿断裂带的地表破裂宽度不同, 中央断裂带不同段落的地表破裂宽度也不相同。断层还表现出明显的断层上盘效应, 北川?映秀断裂上盘最小避让距离为70 m, 下盘最小避让距离为23.5 m, 断层两侧避让总宽度不应小于108 m; 汉旺?白鹿断裂上盘最小避让距离为35 m, 下盘最小避让距离20 m, 总避让宽度不应小于58 m。地表破裂宽度及断层上盘效应与破裂带陡坎高度、地震烈度分布、强震记录具有较好的一致性。

Width and Hanging Wall Effect of Surface Rupture Caused by Wenchuan Earthquake

The authors make the width of surface rupture caused by 2008 Ms 8.0 Wenchuan earthquake as the object, characterize the width of surface rupture by the thrust fault scarps, flexure-slip folds, and mole tracks, and check out characteristics of the width of the surface rupture along the Beichuan-Yingxiu fault and Hanwang-Bailu fault. The conclusion suggests that there is difference about the width between the Beichuan-Yingxiu fault and Hanwang-Bailu fault and about the width in different section along the same Beichuan-Yingxiu fault. Both of the faults have obvious hanging wall effect. The safety distance away from the fault in the hanging wall in rebuilding is 70 m at least and 23.5 m in the foot wall, and the total safety distance along the fault in rebuilding should be more than 108 m about the Beichuan-Yingxiu fault. The safety distance away from the fault in the hanging wall in rebuilding is 35 m at least and 20 m in the foot wall, and the total distance should be more than 58 m about the Hanwang-Bailu fault. In addition, the width and hanging wall effect of co-seismic surface rupture zone is in accordance with the hight of fault scarp, intensity isoseismal map, and strong earthquake ground motions.