大华北地区十次中强地震前后区域地震时间分布结构信息维D1特征

本文用分形理论的信息维方法研究了大华北地区1976年以来十次中强地震区域地震时间分布信息维在主震前后随时间的变化。结果表明信息维的变化反映了地震时间分布结构自组织特征,在震前一、二年内无标度区及其上、下限值出现明显的下降异常变化,无标度区跨度由1个数量级变宽为3个数量级,震后恢复到一个数量级。震前无标度区跨度越宽,表明地震时间分布自相似结构自组织程度越高,大华北地区十次中强震无论其所在地区、震源深度、地震序列类型、发震构造不同、震前信息维都显示了明显的下降过程,并且临震前降到最低值,震后回升。信息维下降异常时间与主震震级无关,但信息维下降的最低值与主震震级有关。

FEATURES OF INFORMATION DIMENSION D1 OF TIME-DISTRIBUTION STRUCTURE OF REGIONAL EARTHQUAKES AROUND TEN MODERATELY STRONG EARTHQUAKES IN NORTH CHINA

This paper studied the variation of the information dimension D1, of the time distribution of regional earthquakes in ten moderately strong earthquakes in North China since 1976 with time around mainshocks using the information dimension method of fractal theory. Results show that the information dimension changes have reflected the selforganization characteristics of time-distribution structure of earthquakes. There appear obvious descending anomaly variations of the non-scale region and its upper and lower limit values one or two years before the earthquake occur rence. The span of the non-scale region becomes wider from one order of magnitude to three orders of magnitude, and it recovers one order of magnitude after the earthquake. The wider the non-scale region span before the earthquake was, it is shown-that the higher the self-similar organization degree is. No matter how different the locations, the focal depth, type of earthquake sequence and causative structures of the ten moderately strong earthquake in North China are,the information dimension before the earthquakes show obvious descending process and they drop to the lowest value before the impending earthquake and rise again after the earthquakes. The descending anomaly duration of the information dimensions is not related with the mainshock magnitude, but the lowest descending value of the information dimensions is in relation with the mainshock magnitude.