岱海流域地貌演化及其对断裂活动性的指示意义

GEOMORPHIC EVOLUTION AND ITS IMPLICATION FOR THE FAULT ACTIVITY IN THE DAIHAI DRAINAGE BASIN

以戴维斯的地貌侵蚀循环学说为基础,运用SRTM-DEM数据、高程-面积分析法和水系分支比研究流域地貌发育。首先运用R ivertools软件平台从DEM数据中提取岱海流域内独立的11个小流域,其中7个位于蛮汉山山前断裂北侧的山地中,另外4个位于盆地南缘断裂南侧的山地中;然后计算每一个流域单元的高程-面积积分值和水系分支比。北侧7个小流域积分值为0.567~0.324,从西向东总体上呈现减小的趋势;南侧4个小流域积分值为0.373~0.425,数值之间比较接近。北侧7个小流域水系分支比的为2.079~2.628,从西向东总体上呈现增大的趋势;南侧4个小流域的水系分支比为2.066~2.138,数值之间比较接近。高程-面积分析法和水系分支比分析表明,北侧7个小流域均反映蛮汉山山前断裂的活动性从西向东逐渐减弱的趋势;南侧的4个小流域均反映岱海南缘断裂沿由西向东的活动性没有明显的变化。北侧7个流域高程-面积积分值与水系分支比之间存在明显的负线性相关;两种指标综合成的主因子的变化范围是1.337^-1.699,从西向东呈现出明显降低的趋势。多种分析方法均表明,蛮汉山山前断裂从西向东活动性有减弱的趋势,而岱海南缘断裂从西向东活动性变化不大。

The Daihai drainage basin（DDB） ,a closed basin, is situated on the northeastern corner of the Ordos Massif. In its center there is the Daihai fault basin between the Manhanshan piedmont fault （MPF）on the north and the southern margin fauh（SMF）on the south. We applied the DEM data, elevation-area integral value, and drainage branching ratio to the study of the geomorphic evolution and its influencing factor in DDB, We emploied the Rivertools （a GIS analytical software）to extract the data of the geometrical shapes and boundaries of the 11 sublevel individual watersheds in DDB,7 in the ridges north to MPF,g in the ridges south to SMF. Afterwards,we took advantage of ArcGIS Desktop （another GIS analytical software）to calculate the elevation-area integral values and the drainage branching ratios of all the 11 watersheds. The elevation-area integral values of the 7 northern watersheds vary from 0. 567 to 0. 324, decreasing eastwards ; while those of the 4 southern watersheds vary from 0. 373 to 0. 425, with no sharp difference from west to east. The drainage branching ratios of the 7 northern watersheds vary from 2. 079 to 2. 628, increasing eastwards, while those of the g southern watersheds are between 2. 066 and 2. 138, with no sharp difference from west to east as well. Both of the 2 indexes of the 7 northern watersheds document a decreasing tendency of the activity of MPF from west to east, while both of those of the 4 southern watersheds do not reflect any obvious difference in the activity of SMF from west to east. There exists a clear negative linear correlation between the 2 indexes of 7 northern watersheds ; the principal factor synthesized from the 2 indexes varies from 1. 337 to - 1. 699 and assumes a remarkable decreasing tendency eastwards. The results of the multiple analytical methods used all indicate that the activity of MPF decreases from west to east, while the activity of SMF shows no significant variance from west to east.