四川汶川地震断裂活动和次生地质灾害浅析

Fault activity of the Wenchuan earthquake in Sichuan,China and seismic secondary geohazards

为了揭示汶川地震断裂活动与次生地质灾害的关系,在对汶川地震重灾区进行快速调查的基础上,分析了影响汶川地震的龙门山断裂带震后的断裂活动、地表破裂与崩塌、滑坡、泥石流等次生地质灾害发育特征的关系。野外调查发现,龙门山3条断裂带的地表变形破坏(包括沿断裂带的道路、农田、建筑物和边坡变形破坏)特征具有明显的差异性和分段性,即映秀-北川断裂地震活动最剧烈,南坝-关庄断裂、灌县-安县断裂、平武-青川断裂等活动性次之的"横向"差异性,以及龙门山断裂带由南向北地震活动性减弱的"纵向"分段性。地震断裂活动的差异性和分段性明显控制了崩塌、滑坡、泥石流等次生地质灾害的发育特征,即映秀-北川断裂区域的次生地质灾害规模大、分布密度大、危害严重,沿其余断裂的次生地质灾害危害相对较轻。

Quick investigation and analysis were carded out in worst-hit areas of the Wenchuan earthquake to reveal the relation between the Wenchuan earthquake fault activity and secondary geohazards. The authors analyzed the relations between fault activities and ground rupture of the Longmenshan falt zone and the characteristics of development of secondary geohazards such as rock falls, landslides and debris flows in main earthquake affected areas. According to the observation, the surface deformation and destruction （including roads, farmland, buildings and slopes along the fault zone） of three fault zones of the Longmen Mountains have distinct differences and segmentation. The activity of Yingxiu-Beichuan fault is most intense, the activities of the Nanba-Guanzhuang fault, Guanxian-Anxian fault and Pingwu-Qingchuan fault come next, showing ＂longitudinal differences＂, and the activity of the Long-menshan fault zone weakens from south to north, showing ＂latitudinal segmentation＂. It is evident that the difference and segmentation of earthquake fault activity controlled the development of seismic secondary geohazards such as avalanches, landslides and debris flows, i.e. the scale, distribution density and harm of secondary geohazards along the Yingxiu-Beichuan fault all exceed corresponding features of the counterparts along other faults.