山西及邻区水系与黄土冲沟的分形几何学分析结果及其与构造活动的关系

FRACTAL GEOMETRIC ANALYSIS OF DRAINAGE AND LOESS GULLLY SYSTEMS IN SHANXI AND ITS ADJACENT AREAS

本文用分形几何理论,对山西及邻区水系与黄土冲沟作了分析,发现水系与冲沟分维值的大小反映了该区构造活动性的强弱,分维值的分布定量地反映了区域构造活动的背景及各区域构造活动性的差异,在构造活动强的区域,分维值高,反之则低。按分维值的大小山西断陷带分成南中北三段,以中段介休-临汾一带的分维值及反映的构造活动性最强。该区分维值的分布及反映的构造活动性有从四周向中间增强的特点,增强区与强震的发生有关。

In this paper, the drainage and loess gully systems in Shanxi and its adjacent areas are processed and analyzed by the fracral geometric method. It is found that the fractal dimension value of a drainage or loess gully system reflects the intensity of tectonic activity. The distribution of the fractal dimension values shows quantitatively the background of tectonic activity and the difference in various regions, and it coincides perfectly with the expression of the intensity of tectonic activity in Shanxi and its adjacent areas. The fractal dimension value is high in strongly activated area, such as along the Shanxi-Weihe Fault basin zone and the mountain areas on its two sides, while it is low within the Ordos block and the area east of the Taiyue Mountain. The Shanxi-Weihe fault basin zone can be divided into three segments according to the fractal dimension values, from which the middle segment is of the highest tectonic activity, the southern segment is secondary and the northern is relatively weak. From view of the whole region, the distribution of fractal dimension values and the reflected tectonic activity tend to increase generally from the suroundings towards centre of the Jiexiu-Linfen area, which is closely associated with the 1303 and 1695 earthquakes with M =8. In addition, the fractal dimension values in the Yuncheng and Lingbao basins are approximately equal, indicating that the drainage features are similar and the tectonic activities equivalent in these two basins. Thus, it is thought that the Zhongtiao Mountain does not the separating boundary between these two basins during the recent tectonic period.Fractal dimension values are associated together with intensity of tectonic activity and difference in various areas in this paper, providing a quantitative criterion for tectonic activity research. It is a new try to use fractal geometry in studying neotectonic movement.