河北平原地区断层系的分形特征分析

FRACTAL CHARACTERISTICS OF FAULT SYSTEM AND THEIR RELATIONS WITH EARTHQUAKES IN HEBEI PLAIN

断层形成机理的复杂性和时空展布的不规则性,传统的评价方法往往很难取得令人满意的定量化结果,应用分形理论可以对断裂构造系进行定量评价,断层分维是断层数量、规模、组合方式及动力学机制的综合体现,因此分维值的大小可以作为断层构造复杂程度一个定量化指标。运用分形理论,对河北平原区主要断裂构造带进行了定量评价。得出河北平原区NNE向分维值为1.358,纬向断层系分维值为1.183,河北平原区活断层系空间分维值较高,这和研究区地震活动频繁、地质灾害多发一致。最后对河北平原区、渭河盆地和川滇断层系分形值和地震活动性进行了分析对比,发现地震空间分布和分形值的大小有对应关系,且渭河盆地、川滇的分形值大于河北平原地区,河北平原所发生的地震多沿NNE向呈带状分布。

Because of the complex mechanism of active faults and their scrambling spread, it is difficult to evaluate the activity of fault system and get satisfied results by traditional methods. Using the theory of fractal can quantitatively analyze and evaluate the fault systems. The fractal dimension of a faults system shows the number of faults in a system, the size of the fault system, the combination mode of the fault system and the dynamics mechanism of the system. So, the fractal dimension can indicate the active and complex grade of a fault system. This paper uses fractal to analyze the faults in Hebei Plain. It gets the fractal dimension of the NNE faults is 1. 358. The fractal dimen- sion of the direction of latitude is 1. 183. The high fractal dimension is consistent with many existing earthquakes and geological hazards occurred in the plain. At last, the paper analyzes and compares the earthquakes and fractal in the three zones： Hebei plain, Weihe basin and Chuandian zone. It is found that for the relationship between the earthquake spatial distribution and the fractal dimension, the fractal dimension in Hebei plain is the least one, and the earthquake zone is distributed along the NNE in Hebei plain.