中国大陆中长期地震活动的群集特征

主要研究中国华北地区和南北地震带中长期地震活动的时间特征。选取华北地区和南北地震带二个地震活动地区1970年以来有仪器记录的完整地震目录。作相关地震删除后对于不同起始震级分别计算不同时-空尺度下观测地震数N_p 与泊松分布下理论地震数n_p 的比值(称为时-空“矩”),结果表明无论华北还是南北地震带,无论起始震级是ML 3. 0或ML 4. 0,所有的地震活动过程都显示群集特征N_p/n_p> 1。地震活动随时间呈指数分布,具有标度不变性,分维数在0. 2～0. 7之间变化。

CLUSTERING OF LONG-AND MEDIUM-TERM SEISMICITY ON CHINA MAINLAND

This paper analyses the characteristics of long-nd medium-termsei smicity on China's mainla nd. We selected earthquake catalogue on North china seismic region and South-North seismic zone from 1970. 1 till 1997.12. After removing the dependent earthquakes, we have found that all earthquakes, either North china seismic region or Southnorth seismic zone, from ML 3.0 or ML 4.0, the feature of residual earthquakes shows clustering. And the long-term variation of seismicity is governed by power lawtemporal distribution; it is scale-inv ariant. The fractal dimension of shallow earthquakes on china mainland changes from 0.2～0.7.