地貌形态指数反映的青藏高原东北部宛川河流域新构造活动

宛川河为黄河的一级支流,位于青藏高原东北部的兰州盆地东部.该区域历史时期曾发生多次6级以上地震.以DEM数据为基础,通过河流水系分析和地貌形态指数的计算,讨论了区域新构造活动特征.山前曲折度指数(SMF)在宛川河北为1.03~1.18,在兴隆山北前缘为1.83~2.88;河谷宽高比指数(VF)在宛川河北部为0.36~2.34,在南部的兴隆山为0.55~13.SMF与VF值的大小和分布特征表明研究区新构造活动活跃,且宛川河以北(前人推测有断层存在)新构造活动的活跃程度更高.流域盆地非对称性指数(AF)在宛川河北部东南端的异常揭示存在掀斜断块和褶皱运动;结合裂点分布和沟谷错断等地貌特征,发现宛川河北正断裂的东南端也存在西北--东南向走滑活动.

The neotectonic activity of Wanchuan catchment reflected by geomorphic indices

Wanchuan River, located in the northeastern Tibetan Plateau, is one of the tributaries of the Yellow River. This area has witnessed many earthquakes of magnitude 6 on the Richter scale. Based on DEM data, this paper discussed the characteristics of neotectonic activity by analyzing the drainage networks and calculating geomorphic indices. It turns out that the mountain front sinuosity index is between 1.03 and 1.18 to the north of Wanchuan River (NWR) and from 1.83 to 2.88 in Xinglong Mountain (XLM); while the valley floor height-to-width ratio index is about 0.36-2.34 in NWR while it ranges from 0.55 to 13 in XLM. The values and distribution of the mountain front sinuosity index and the valley floor height-to-width ration indicate that neotectonics are still active in the study area, and the movements in the north of Wanchuan River catchment are more active. The abnormal AF index in the southeast part means that there should be tilted fault block and folds in the northwest of Wanchuan River catchment. There exists a strike-slip fault in the southeast of the northern Wanchuan River valley, indicated by analyses of the distribution of knickpoints and off-set valley.