川滇地区前兆震群参数指标及其区域分布

Parameter Index of Precursor Swarms and Its Regional Distribution in the Sichuan-Yunnan Area

通过分析处理1970年以来川滇地区中小地震资料,提出了川滇地区前兆震群的定义,着重研究了前兆震群、前兆震群指标及其空间分布特征,结果表明前兆震群具有集中分布的区域特征;前兆震群参数指标为能量释放均匀度U≥045,震群信息熵K≥055,地震发生方式ρ≤07,震群b≥09或≤075,最大震级与次大震级差ΔM≤04,综合判定指标为5项震群参数指标3项达标。前兆震群参数的空间分布特征为ΔM无区域特征,U值、K值、b值与ρ值在思茅、景洪相对偏低。即除震级差ΔM的空间分布无区域性,前兆震群与其余震群参数均有不同程度的区域性分布特征。

Based on the definition of the earthquake swarm in the Sichuan-Yunnan area, the moderate and small earthquakes have been sorted out in the Sichuan-Yunnan area since 1970, and the parameter index of precursor swarms and their spatial distribution have been studied. It is discovered that the precursor swarms have regional characteristics of concentration distribution. The parameter index of the precursor swarm are U≥0.45, K≥0.55, ρ≤0.7, b ≥0.9 or b≤0.75, ΔM≤0.4. The synthetic index is 3/5 parameters reach to the criterion. The spatial distribution of the parameters has following characteristics: the magnitude difference of the maximum and the second magnitude (ΔM ) doesn't show regional characteristics, while the energy release homogeneity U, the swarm information entropy K, b value of the swarm and the earthquake occurrence form ρ are relatively low in Simao and Jinghong, Yunnan. Namely, the precursor swarm and its parameters have regional characteristics except the magnitude difference ΔM.