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2008年盈江地震序列的震源参数和震源机制相关系数研究
邓菲1) 刘杰2)
1) 中国地震局地震预测研究所,北京100036 /2) 中国地震台网中心,北京100045
摘要:
基于云南数字地震台网记录的2008年盈江地震序列的数字波形资料,采用波谱分析方法和Brune震源模型,得到盈江地震序列的震源参数。利用两次地震事件的相同台站的震源谱参数(零频振幅)计算谱振幅相关系数,据此对地震的震源机制进行聚类分组,并收集和对比地震序列已知的震源机制解结果,发现每组内震源机制解P轴的相关性较好,且相关系数越大,P轴的方位角就越接近。将盈江地区划分为三个研究区,联合震源参数的应力降和聚类分组中每组的平均震源机制解结果研究地震序列发生过程中应力的释放水平和应力场方向变化特征。结果表明:不同阶段震源机制解类型的变化和转化特征一定程度上反映了孕震过程中区域应力场随时间的变化特征,并且地震震源机制解类型在时间段上的集中并向区域构造应力场方向转换的现象可能是发生强震的标志。震源机制解分组类型和对应类型的地震的应力降有一定依赖关系,震源机制解类型反映的应力场与区域应力场接近的地震应力降高,震源机制解类型反映的应力场与区域应力场差距较大的地震应力降普遍较低。
关键词:  应力降  震源机制相关性  聚类分组  盈江地震序列
DOI:
分类号:
基金项目:
Research on the Source Parameters and Correlation Coefficients of Focal Mechanisms for the Yingjiang Earthquake Sequences in 2008
Deng Fei,Liu Jie
Abstract:
The source parameters of the Yingjiang earthquake sequences in 2008 are obtained by applying spectral analysis and Brunes source model,based on the digital waveform data recorded by the Yunnan Digital Seismic Network. The correlation coefficients are calculated using the low-frequency spectral amplitudes of 2 events recorded by a same station,then,events with similar focal mechanism are grouped using the clustering analysis method. Compared to the obtained focal mechanisms,it is found that there are good correlations with the azimuth of P axes in each clustering group,and the larger the correlation coefficient,the closer the azimuths of P axes. We divide the Yingjiang area into 3 regions to analyze the stress level and stress direction by combining the source parameters and the mean focal mechanism of each group. The results show: The change and transformation of the focal mechanism types at different stages can represent the temporal characteristics of the regional stress field. If the earthquake focal mechanism types are concentrated in a time period and switch to the direction of regional stress field, it may be a sign of strong earthquake. There is some relationship between the stress drop and the type of focal mechanism. Those earthquakes with stress fields revealed by focal mechanism types closer to the regional tectonic stress field will have higher stress drop, while those with the focal mechanism-revealed stress fields differing a lot from the regional tectonic stress field will generally have a lower stress drop.
Key words:  Stress drop  Correlation of focal mechanisms  Clustering group  Yingjiang earthquake sequences in 2008