Journal of Geo-information Science >
Quantitative Analysis of the Tectonic Activity in Minjiang Drainage Basin Based on DEM
Received date: 2013-09-23
Request revised date: 2013-11-05
Online published: 2014-07-10
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Geomorphic indices have been widely used in relative tectonic activity studies. Most studies provide semi-quantitative information to depict relative degree of tectonic activity in mountain fronts or small basins. Here we introduced an additional fractal dimension index (FD) which is found to improve the analysis of tectonic geomorphology. Based on ASTER-GDEM data and the technique of GIS, the other tectonic geomorphic indices are extracted in Minjiang River drainage basin including hypsometric integral, stream-gradient index, drainage basin asymmetry, drainage basin shape, ratio of valley floor width-to-height, and drainage elongation ratio. This drainage is located in the transitional region between Eastern Tibetan Plateau and Sichuan Basin with an area of 23 000 km2. The results obtained from these indices are combined to yield an index of relative active tectonics (IAT) that is obtained by the average of the different classes of geomorphic indices. Based on IAT value, four classes are defined: Class 1: very high relative tectonic activity with 1≤IAT<1.5; Class 2: high with 1.5≤IAT<2.0; Class 3: moderate with 2.0≤IAT<2.5 and Class 4: low with 2.5≤IAT. Through the analysis of the geomorphic results in Minjiang River drainage basin, we conclude that the value of hypsometric index is moderate, the shape of hypsometric curve is convex-concave, Minjiang River basin tilt from right to left facing downstream, the shape of this basin is elongate, the stream length gradient index is high and the fractal dimension value is low, and this drainage have relatively higher tectonic activity (IAT=1.33). The indicative value of IAT is consistent with the areas of known relative uplift rates, landforms and geology. This method provides a new insight for exploring diversities of relative tectonic activities on an areal basis.
CHANG Zhiyang , WANG Jian , BAI Shibiao , ZHANG Zhigang . Quantitative Analysis of the Tectonic Activity in Minjiang Drainage Basin Based on DEM[J]. Journal of Geo-information Science, 2014 , 16(4) : 568 -574 . DOI: 10.3724/SP.J.1047.2014.00568
Fig.1 Location of the study area, river system and the faults图1 研究区地理特征简图(F1:岷江断裂;F2:茂汶断裂;F3:北川-映秀断裂) |
Fig.2 Technical flowchart of tectonic activity intensity assessment图2 构造活动强度量化分析流程 |
Tab.1 Summary of the morphometric parameters used in tectonic landform analysis表1 构造活动强弱评估所使用的地貌参数 |
地貌参数 | 计算公式 | 描述 |
---|---|---|
面积高程积分值(HI[21-23]) | HI=(hmean-hmin) /(hmax-hmin) | hmean是流域内高程的平均值,hmin是流域内高程的最小值,hmax是流域内高程的最大值。一般而言,高积分值表征流域流域受到构造活动的影响较大 |
面积高程积分曲线[21-23] | x=a/A,y=h/H | 面积高程积分曲线是以流域中相对高度比(h/H)为纵轴、相对面积比(a/A)为横轴绘制的曲线,可分为凸形、凹形、凹凸形曲线 |
河长坡降指数(SL[12,24-25]) | SL=(△h/△L)L | △h为单位河段的高程值变化,△L为单位河段的长度,△h/△L为河段的坡度,L为河流源头到河段中点的河长。SL异常值与构造、岩性、支流汇入等有关 |
流域盆地不对称度(AF[2,26]) | AF=(Ar/At)×100 | Ar是某一流域内顺着干流流向右侧的面积,At是流域的总面积,该指标可反映流域的不对称度,表征流域的构造倾斜程度 |
盆地形状指数(BS[5]) | BS=Bl/Bw | Bl为流域盆地河谷的源头至出山口的直线距离,Bw为流域盆地的最大宽度,流域形态可分为圆形及狭长形态,反映了构造抬升的影响 |
谷底宽度与谷肩高度比(VF[5-6]) | VF=2Vfw/(Eld+Erd-2Esc) | Vfw为谷底宽度,Eld和Erd分别为河谷两侧分水岭的高程值,Esc为谷底高程值,VF值大小可用来分析构造抬升与河流侵蚀程度 |
水系分维数(FD[27-28]) | FD= | r为不同大小的栅格,单位为m,N(r)为非空盒子的数目,水系的分维可反映水系的发育程度,代表水系所处流域的地貌侵蚀发育阶段,较低的水系分维值,意味着易受到较强构造活动的影响 |
Fig.3 Hypsometric integral curve of the study area图3 研究区的面积-高程积分曲线(h为某一等高线相对于最低点的高差;H为流域地势高差;a为某等高线之上的流域面积;A为流域总面积) |
Fig.4 Hack profile of the study area图4 研究区Hack剖面曲线 |
Fig.5 The relationship between the number of cell size and length图5 水系格网数目与格网大小双对数图 |
Tab.2 Classification of relative tectonic activity depending on geomorphic indices表2 主要地貌参数值的构造活动强度等级划分 |
活动等级1(强) | 活动等级2(中等) | 活动等级3(弱) | |
---|---|---|---|
HI[10-11,16] | HI>0.5 | 0.40≤HI≤0.50 | HI<0.40 |
SL[14,25,29] | SL≥500 | 300≤SL<500 | SL<300 |
AF[1,10-11,26] | |AF-50 | >15 | 7<|AF-50 | <15 | |AF-50 |< 7 |
BS[5,14] | BS≥3 | 2≤BS<3 | BS<2 |
VF[14] | VF<0.50 | 0.50≤VF<1.0 | VF≥1.0 |
FD[27-28] | FD<1.6 | 1.6≤FD<1.89 | 1.89≤FD |
Tab.3 Values and classification of geomorphic indices and tectonic activity level表3 研究区地貌参数指标和构造活动等级划分 |
HI | SL | AF | BS | VF | FD | |
---|---|---|---|---|---|---|
地貌参数值 | 0.5 | 800 | 83.7 | 2.4 | 0.26 | 1.02 |
构造活动等级 | 2 | 1 | 1 | 2 | 1 | 1 |
IAT值 | 1.33 | |||||
IAT等级 | 1 |
The authors have declared that no competing interests exist.
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