北天山流域地貌特征及其构造活动分析

Geomorphology of Northern Tianshan and Its Structural Analysis

以流域为单位计算地貌参数有助于分析区域构造活动。该文以北天山山区为研究区,将其划分为805个流域,提取地势起伏度(RA)、分形维数(FD)、河流阶梯指数(SL)、面积-高程积分(HI)、圆度比(Rc)5个参数,并以此为基础构建相对构造活动强度(IRAT),以此分析北天山流域地貌特征及构造活动强度。研究表明北天山不同地貌分区内呈现不同地貌特征,高山区地势起伏度及河流阶梯指数整体较大,河谷区圆度比变化较大。相对构造活动强度空间分布表明,研究区域中间部分构造活动较为活跃,自中部向东西两侧,强度逐渐降低;低山丘陵区中,准噶尔南缘断裂带所在区域构造活动强度更高。以流域地貌指标反映的构造活动强度分布与地壳构造变形位移场所计算结果较为相似。

Get^morphic indices based on drainage basins are conductive for analyzing thespatial intensity of tectonic act ivit y.T his paper took northern T ianshan as the research region and divided it into805drainage basins.First,five indices were calculated for each basin,including the relief amplitude(RA),the fractal dimension(FD),the hypsometric integral(HI),the stream length gradient(SL)and the circular ratio(Rc).T hese geomorphic indices were then divided into five classes,and average class values of the five indices were applied to derive the index of relative active tectonics(IRA T).Finally,this paper analyzed the topographical features and the intensity of tectonic activity.The research results show that different get^morphological subareas of northern T ianshan represent different morphological characteristics:the value of SL and RA in high mountain are larger than other places while Rc value changes greatly in river valley.Besides,the spatial distribution of IRA T value suggests that tectonic activity in middle area is relatively strong and gradually reduces to East and West sides;Meanw^hile,the intensity of tectonic ac-t ivity of t he southern margin of the Junggar fault zone is higher.in addition,the spatial intensity of tectonic activity analyzed by geomorphic indices also shows a good correspondence compared with the results calculated by tectonic deformation displacement field.