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渭河上游流域位于青藏高原东北缘,横跨近东西向的秦岭北缘构造带和近南北向的贺兰山构造带的复合部位,是青藏高原向大陆内部扩展增生的前缘部位。晚更新世以来,伴随着青藏高原的不断隆升与扩展,研究区构造活动程度强烈。同时,受印度板块和欧亚板块碰撞的远程效应的扩散作用和南北构造带活动的叠加作用影响,造成流域内部构造活动相对程度的差异性,因而需要对其分区域分析。本文利用DEM数据和3S技术,对区域地形地貌进行三维可视化和统计分析,提取地貌的参数指标,如面积-高程积分(Hi)、流域盆地不对称度(AF)、河长坡降度(SL)、山前曲折度(Smf)、谷底宽度与谷肩高度的比值(Vf)、盆地形状指数(Bs)等,然后对地貌参数指标等级进行算术平均化(S/n),可得到区域的相对构造活动程度(Iat),分为低、中等、高和较高四类等级。分析结果认为:渭河上游流域相对构造活动程度(Iat)值为1.50,流域相对构造活动程度等级为2级,属于区域活动构造程度高的地区。其中六盘山东麓断裂南端和西秦岭北缘断裂带(天水-武山断裂和漳县断裂)构造活动程度(Iat=1.33)较强,面积约占流域总面积8.79%。而研究区东南部的八渡-虢镇断裂和陇县-岐山断裂构造活动程度中等,反映了晚更新世以来,该区域构造活动减弱。研究结论与野外地质和地貌调查结果一致。
The upper reaches of the Weihe River basin is located in the northeastern margin of the Qinghai-Tibet Plateau and extends across the nearly east-west tectonic belt of the Qinling Mountains and the Helan Mountain tectonic belt near the north-south direction. It is the front part of the Qinghai-Tibet Plateau expanding to the interior of the mainland. Since Late Pleistocene, with the continuous uplift and expansion of the Qinghai-Tibet Plateau, tectonic activity in the study area has been strong. At the same time, due to the remote effect of the collision between the Indian plate and the Eurasian plate and the superimposition of the activities of the North and South tectonic belts, the relative degree of structural activity in the basin is different, so the sub-region analysis is needed. In this paper, DEM data and 3S technology were used to visualize and analyze the regional topography. The parameters of the topography were extracted, such as area-elevation (Hi), basin basin asymmetry (AF) (Smf), the ratio of valley width to valley height (Vf), basin shape index (Bs) and so on, and then arithmetic average (S / n) the index of geomorphic parameters can be obtained. Relative structural activity (Iat), divided into low, medium, high and high four levels. The results show that the relative tectonic activity (Iat) value of the upper Weihe River Basin is 1.50, and the relative tectonic activity level of the basin is Grade 2, which belongs to the area with high tectonic activity in the area. Among them, the tectonic activity (Iat = 1.33) at the southern tip of the Liupan Mountain and the northern margin of the West Qinling fault (Tianshui-Wushan fault and Zhangxian fault) are strong, accounting for 8.79% of the total basin area. In the southeastern part of the study area, the faults of Badu-Jiuzhen fault and Longxian-Qishan fault have a moderate degree of tectonic activity, which reflects the weakened tectonic activity in the region since the late Pleistocene. The conclusions of the study are consistent with the findings of field geology and geomorphology.