STUDY ON THE GEOMORHOLOGIC ZONATION BY FRACTAL PARAMETERS——A CASE STUDY OF ORDOS BLOCK AND ITS SURROUNDING AREAS
利用分形参数进行地貌定量分区研究——以鄂尔多斯块体及周边为例

Geomorphologic zonation is one of the fundamental works in Geoscience,but it was mostly qualitative in the past.Several studies on the quantitative geomorphologic zonation have been done based on the terrain factors such as slope,aspect and relief in recent years,however,many problems are still unresolved.As the digital terrain technology and the fractal theory become more mature,it is possible to classify quantitatively landforms by such fractal parameters as the surface fractal dimension(D)and the ordinate-intercept(γ).In this paper Ordos Block and its surrounding areas were chosen,and,based on the 90-m-resolution SRTM data,the variogram method and the cellular fractal model were adopted to calculate their fractal parameters in such three sizes of the moving windows as 65×65,129×129 and 257×257.The results in these moving windows indicate together that the scale-invariance of the landforms of Ordos Block and its surrounding areas hold over at least from 2.97km to 11.61km,and the distributions of the fractal parameters are region-dependent apparently.The quantitative geomorphologic zonation by the fractal dimension and the ordinate-intercept comprehensively is achieved with the K-Means unsupervised classification.The resultant regions are consistent with the geomorphologic types and each zone has the characteristic fractal values.Hetao Basin and Yinchuan Basin are characterized by high surface fractal dimensions and low ordinate-intercepts(D=2.8~3.0,γ=0~1)in contrast to the mountainous areas including Luliang Mountain,Helan Mountains and Wulaer Mountains where low surface fractal dimensions and high ordinate-intercepts(D=2.4~2.6,γ=2.5~3.5)are found.The other regions are defined by the following fractal parameters respectively: North Shaanxi Loess Plateau in the southern part of Ordos Block,D=2.5~2.7 and γ=2.5~3.5; Kubuqi Desert and Mu Us Desert in the northern part of Ordos Block,D=2.2~2.4 and γ=0~1;Shanxi Basin Belt and Weihe Basin,D=2.2~2.4 and no predominant ordinate-intercept values.The comprehensive zonation result shows that the fractal feature is related with the geological structures and the geomorphologic types closely in each zone,it is therefore feasible to classify landforms quantitatively by fractal parameters.