龙门山区湔江水系样式及其对汶川地震的响应

摘要

Wenchuan Earthquake(Ms8.0) on May 12,2008 in Sichuan is a serious disaster in Longmenshan Mountain tectonic belt.The earthquake occurred along Yingxiu-Beichuan,Pengguan and Xiaoyudong fault zones.Co-seismic deformation led to dramatic change of ground appearance.The earthquake also caused landslide and collapse,which further developed into debris flow with heavy rainfall.All these lead to a series of changes of river geomorphology and response in Longmenshan Mountain Zone.By use of SRTM3-DEM data,geographic information system (GIS),and hydrological analysis module of software ArcGIS 9.3,drainage pattern map of Jianjiang basin is extracted.Based on this information,matching character between the surface rupture combination style in the Xiaoyudong zone and the drainage pattern on the Jianjiang River is researched.The results are as following:(1) Direction of the river course is controlled by surface rupture (for example,the direction of river course and flows in the upstream of Jianjiang River is controlled by the direction of Beichuan fault) ; (2) Direction of surface rupture has the distinct effect on the river turning and slope break point(for example,Xiaoyudong fracture leads to the turning of the main course of Jianjiang River,and Pengguan fault controls the slope break point and turning point of the Bailu River) ; (3) Surface rupture combination style has the crucial function on the drainage pattern of the river.That is proved by the fact that I-shape surface rupture combination style in the Xiaoyudong zone steers the drainage pattern of the Jianjiang River,which leads to the asymmetric and irregular character of the drainage pattern of Jiangjiang River.In sum,drainage pattern of Jianjiang River is mainly affected by the surface rupture and combination style caused by Wenchuan Earthquake.%2008年“5.12”四川汶川Ms8.0地震是发生在龙门山构造带中段的一次重大灾变事件,地震沿映秀-北川、彭灌和小鱼洞等3条断裂带发生了地震地表破裂,同震构造变形造成这些断裂带地表地貌特征发生巨大变化,地震还伴生了大量滑坡和崩塌,在雨季,强降雨驱动了大规模泥石流的发生,从而导致龙门山构造带的河流地貌发生了一系列变化和响应.本次研究利用SRTM3-DEM数据,以地理信息系统(GIS)为平台,通过ArcGIS 9.3软件中的水文分析模块,提取了湔江流域的水系样式图.在此基础上,通过对小鱼洞地区地表破裂组合样式与湔江水系样式的匹配性研究,结果表明:1)地表破裂走向对河道走向具有明显的控制作用(如映秀-北川断裂控制了湔江上游的河道和流向)；2)地表破裂走向对河道偏转及坡折点具有明显的控制作用(如小鱼洞断裂导致了湔江主河道的偏转、彭县-灌县断裂控制了白鹿河的坡折点及转折点)；3)地表破裂组合样式对水系样式具有明显的控制作用,表现在小鱼洞地区“工”字形的地表破裂组合样式对湔江水系样式的控制作用,使得湔江水系样式具有不对称性、不规则性.由此可知:湔江水系样式主要受到汶川地震地表破裂及组合样式的控制作用.