地震前兆群体空间非均匀性指标C_v值研究

Research on the Spatial Inhomogeneity Parameter C_v of Earthquake Precursory Group

本文描述了排除地震台站空间分布不均匀、台站观测项目数量不同等非地震成因因素影响后的前兆群体空间非均匀性研究思路及其指标Cv值,确定了Cv值反映的前兆群体空间分布图象的类型及其判定方法。利用Cv值对华北地区1995年以来的水氡短临前兆异常群体空间分布非均匀性及其与地震的关系进行了分析,结果表明,华北地区1995年1月1日至1998年2月1日发生的5次5级以上中强地震前,前兆群体空间分布出现5次非均匀性增强的过程,除离观测台网较远,于1996年11月发生的南黄海62级地震位于前兆群体非均匀性增强过程即将结束的时段外,其余4次地震均发生在前兆群体非均匀性增强过程结束、恢复均匀分布的时间段内。本文通过对已有岩石力学实验和震例研究成果的综合论述,探讨了短临前兆群体非均匀性的物理、力学成因机制。

The research method and parameter C v ,which depicts the spatial inhomogeneity of earthquake precursory group are developed in the paper.The affections of factors,such as inhomogeneity distribution of precursory observatory,the variety of observatory method number in each observatory station and the abnormal number of the same observatory method in different stations,etc.,which causes the non\|earthquake induced inhomogeneity,can be eliminate from C v .The criteria of C v to differentiate particular spatial pattern of earthquake precursory group are also introduced.Based on the method,the spatial inhomogeneity of precusory group of radon and the relationship between it and moderately strong earthquakes occurred in North China during the same period are analyzed.The results show 5 strengthen processes of spatial inhomogeneity of precursory group of radon before 5 earthquakes with M ≥5 0 in North China during the period from Jan.1,1995 to Feb.1,1998.Among which 4 earthquakes occurred within the time interval which the precursory group resumed spatial uniform distribution after the spatial cluster distribution,except for the South Yellow Sea earthquake with magnitude 6.2 occurred in Nov.1996,which is far from the observatory network.The physical mechanism of spatial inhomogeneity of short\|and imminent\|term precursory group is discussed according to the results available from rock mechanical experiments and earthquake cases study.