宁蒗6.2级地震活动异常动态演变图像与序列主要特征
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摘要
:1 998年 1 1月 1 9日云南宁蒗发生了 6.2级地震 ,根据震前震源区及周围地区中小地震活动异常图像 ,分析研究了在区域应力场作用下 ,震源区介质由稳定状态进入非稳定状态过程地震活动异常动态演变特征。同时 ,根据序列参数 h、b值的动态变化 ,给出序列异常变化特征。主要特征为 :1 .地震孕育中期阶段 ,3级以上地震活动主要分布在震源外围地区 ,震源区高度平静 ;地震孕育发展至短期阶段 ,震源外围地震活动消失 ,震源周围地震活动迅速增强 ,且随着地震的逼近 ,地震活动逐渐向震源区收缩 ;至短临阶段 ,孕震区出现显著的小震群活动。 2 .宁蒗 6.2级地震在其 5.3级前震前 ,震群发育 ,震群参数 h值小于 1 .0 ,且随着地震的逼近 ,震群参数 h值逐渐减少、b值逐渐增大。 3 .5.2级前震和6.2级主震前 ,序列参数 h值均出现明显快速减小的动态异常过程。此外 ,5.3、5.2级前震后 ,其 2级以上余震衰减迅速 ,且余震又少又小。
There was occurred an earthquake with Ms6.2 in Ninglang Yunnan province on Nov. 19, 1998. According to the small earthquake seismic anomalies in and around epicentral area before the main shock ,the author has analysed the anomaly dynamic evolution in the process of the medium in the epicentral area from steady to unsteady in the action of regional stress field,and he has got the sequential anomaly characteristics according to the sequential parameters of h and b values. The characteristics are:1.Ms≥3.0 earthquakes are distributed in the outer area of the epicent,and the epicentral area is extreamly quiet in the middle period of seismogeny, in the earthquake development to the short period, seismicity of outer area disappeared and strenghened to the epicentral area; in the short impending period,small earthquake swarm acted significancely in the seismogenic area. 2. The earthquake swarm parameter h<1.0 before Ninglang Ms6.2 earthquake,and then h value began smaller, b value began bigger. 3.Before pre earthquake with Ms5.2 and main shock with Ms6.2,h value appeared rapidly smaller process,and after pre shocks with Ms5.3 and Ms5.2,the after shocks with Ms≥2.0 attenuated rapidly and they were smaller and fewer.
There was occurred an earthquake with Ms6.2 in Ninglang Yunnan province on Nov. 19, 1998. According to the small earthquake seismic anomalies in and around epicentral area before the main shock ,the author has analysed the anomaly dynamic evolution in the process of the medium in the epicentral area from steady to unsteady in the action of regional stress field,and he has got the sequential anomaly characteristics according to the sequential parameters of h and b values. The characteristics are:1.Ms≥3.0 earthquakes are distributed in the outer area of the epicent,and the epicentral area is extreamly quiet in the middle period of seismogeny, in the earthquake development to the short period, seismicity of outer area disappeared and strenghened to the epicentral area; in the short impending period,small earthquake swarm acted significancely in the seismogenic area. 2. The earthquake swarm parameter h<1.0 before Ninglang Ms6.2 earthquake,and then h value began smaller, b value began bigger. 3.Before pre earthquake with Ms5.2 and main shock with Ms6.2,h value appeared rapidly smaller process,and after pre shocks with Ms5.3 and Ms5.2,the after shocks with Ms≥2.0 attenuated rapidly and they were smaller and fewer.
引文
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[2 ] 程式 .1 976年 1 1月 7日四川盐源 6.7级地震 [A].中国震例 .北京 :地震出版社 ,1 990 .1 48.
[3] 刘正荣 .地震频度衰减与地震预报 [J].地震研究 ,1 986,9( 1 ) :1～ 1 1 .
[4] 陈立德 .震源硬化模型的理论、实验及观测事实依据 [J].地震 ,2 0 0 0 ,2 0 ( 1 ) :1～ 8.
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