地貌指数在当雄县宁中盆地及邻域构造活动性评价中的应用

Application of Geomorphic Index in Evaluating Tectonic Activity in Ningzhong Basin and Its Adjacent Areas of Dangxiong Country

遥感技术作为研究构造活动性的一种重要手段,可获取构造地貌的空间分布及水平位移分量,但无法量算垂直位移分量.应用高分辨率数字高程模型(digital elevation model,DEM)数据,得到的地貌指数可定量化表达地貌表面的三维特征,对垂直位移分量的量算具有独特优势,可弥补遥感解译方法的不足.本文以当雄县宁中盆地及邻域为研究区,利用12.5 m分辨率DEM数据计算7种地貌指数,包括山前曲折度指数、横向地形对称指数、流域非对称性指数、河谷宽高比指数、面积-高程积分指数、纵剖面和裂点以及河流坡降指数,通过与遥感解译结果进行对比验证,综合分析研究区的构造活动性,并探讨地貌指数的适用条件.研究表明,在相同的分级标准下,F1断层为正断层,活动性较弱;F2断层为左旋走滑兼正断层,活动性最强;F3断层为左旋走滑兼正断层,活动性较强.

Remote sensing technology,as an important method to research tectonic activities,has a good effect on obtaining the spatial distribution and horizontal displacement components of tectonic landforms.But it cannot calculate the vertical displacement components.If high-precision digital elevation model(DEM)is used,the obtained geomorphic index can quantitatively express the three-dimensional characteristics of the geomorphic surface,which has unique advantages in the calculation of vertical displacement components and can make up for the shortcomings of remote sensing interpretation methods.This paper takes the Ningzhong Basin and its vicinity of Dangxiong County as the research area,and uses the 12.5 m resolution DEM data to calculate 7 types of geomorphic index,mountain front sinuosity index,transverse terrain symmetry index,uneven basin asymmetry factor,valley floor width to valley height ratio,area-elevation integral index and stream gradient index,the profile and the knicks.The results are compared with the remote sensing interpretation results to comprehensively analyze the tectonic activity of the research area and find out the application conditions of geomorphic indexes.Results show that under the same classing standard,F1 fault is a normal fault with weak mobility;F2 fault is a left-lateral strike-slip and normal fault with the strongest activity;F3 fault is a left-lateral strike-slip and normal fault with the medium activity.