在Landsat遥感图像解译、ASTER GDEM数据处理、地形图分析、地质图分析和地貌剖面制作的基础之上,结合野外构造地貌考察与观测,对龙门山北东段山前区域内的构造地貌进行了定量、半定量分析,研究发现沿山前发育的水系及其演化、河道形态、河床高程、冲积扇展布均与大规模逆冲断裂有关,河流阶地不对称分布说明龙门山北东段山前断裂在扩展过程中存在着由北东向南西迁移的特征.通过宇宙核素成因埋藏年龄测试技术测定了古冲积扇的形成年龄,并利用古冲积扇的高程差异及扇根间距计算了龙门山北东段的第四纪活动速率,表明自1.73 Ma、0.54 Ma以来,龙门山北东段山前逆冲断裂的隆升速率分别为0.06 mm/a、0.09 mm/a;右旋走滑速率分别约为2.31 mm/a、1.48 mm/a.%There is a close relationship between the evolution of landforms and tectonic activities.In this paper,the authors selected north east sections of Longmen Mountains foreland faults at the eastern margin of the Tibetan Plateau as a place to study the morphotectonic features.Based on the Landsat ETM Satellite images,ASTER DEM data,topographic and geologic maps,the river channel and terraces sections by using GIS spatial analysis combined with field morphotectonics investigations and observations,the characteristics of Fujiang River alluvial fans in Wudu Basin of Jiangyou County can be quantitatively and semi-quantitatively studied based on the river channel elevations,dating data of samples,fluvial system characteristics,and distance between the fan root is measured and studied in the study area.The results show that:(1)Typical tectonic geomorphologic features such as the drainage system,river channel,river bed elevation,alluvial fan root,large-scale thrust fault,asymmetric riverine terraces along the piedmont indicate that this thrust fault migrated from northeastern to southwestern.(2)Based on the elevation difference of alluvial fan data,cosmogenic nuclide burial ages data of alluvial fan and the distance between the fan root data,activity rates of the fault have been estimated:since 1.73 Ma and 0.54 Ma,in Early Pleistocene and Middle Pleistocene,the Longmen Mountains in north-eastern piedmont thrust fault uplift rates is about 0.06 mm/a and 0.09 mm/a respectively;the fault right-lateral strike-slip rates is about 2.31 mm/a and 1.48 mm/a respectively.(3)The Longmen Mountains in north-eastern piedmont fault right-lateral strike-slip rates are larger than that uplift rates since Late Pleistocene,indicate that the north east Longmen Mountains tectonic belt is given priority to the right-lateral strike-slips,and supplemented by thrust fault.
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