采用体波谱振幅相关系数方法研究地震集中区震源机制变化过程
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摘要
同一震源区两次地震到达某台站的直达P波、S波零频观测谱值之比与其辐射图型因子之比线性相关,而后者取决于震源机制的几何特性。用波形记录计算谱振幅相关系数,认为该系数是震源机制异同的归一化数值描述。据此对2003年青岛序列及冀鲁豫交界地区小震集中区地震事件进行聚类分组,给出序列事件的滑动平均相关系数的时序曲线。研究结果表明:青岛序列的滑动平均相关系数时序曲线存在由一致到发散的变化过程,即震源区应力场强度由相对集中向逐步分散过度;冀鲁豫交界地区小震集中区谱振幅相关系数较低,震源机制各不相同,区域应力积累没有形成任何一个优势方向。
The ratio of observed spectral amplitudes of direct P and S wave phases is linearly correlated with the ratio of their radiation pattern factors,and the radiation pattern factor depend on geometrical property of focal mechanism,if 2 events occurred in same focal region and recorded by same seismic station.Using low-frequency spectral amplitude values the correlation coefficient can be calculated,and the coefficent gives a normalized measurement for the similarity of focal mechanisms.Applying this method to the Qingdao earthquake sequence in 2003 and the small earthquake concentrating area in conjactive area of Hebei,Shandong and Henan provinces,the events with similar focal mechanism can be grouped,and the temporal average correlation coefficient curve of earthquake sequence can be obtained.The results show: the temporal average correlation coefficient curve of Qingdao earthquake sequence is changed from centralizing to scattering pattern,namely stress strength in focal area was transform from comparatively concentrating to separating;but the coefficient for conjactive area of Hebei,Shandong and Henan was poorer,regional stress concentration is not formed one dominant diraction.
The ratio of observed spectral amplitudes of direct P and S wave phases is linearly correlated with the ratio of their radiation pattern factors,and the radiation pattern factor depend on geometrical property of focal mechanism,if 2 events occurred in same focal region and recorded by same seismic station.Using low-frequency spectral amplitude values the correlation coefficient can be calculated,and the coefficent gives a normalized measurement for the similarity of focal mechanisms.Applying this method to the Qingdao earthquake sequence in 2003 and the small earthquake concentrating area in conjactive area of Hebei,Shandong and Henan provinces,the events with similar focal mechanism can be grouped,and the temporal average correlation coefficient curve of earthquake sequence can be obtained.The results show: the temporal average correlation coefficient curve of Qingdao earthquake sequence is changed from centralizing to scattering pattern,namely stress strength in focal area was transform from comparatively concentrating to separating;but the coefficient for conjactive area of Hebei,Shandong and Henan was poorer,regional stress concentration is not formed one dominant diraction.
引文
[1]国家地震局监测司.测震学分析预报方法[M].北京:地震出版社,1997:131-136.
[2]Lund B,Boovarsson R.Correlation of Microearthquake Body-WaveSpectral Amplitudes[J].Bull.Seism.Soc.Amer.,2002,92:2419-2433.
[3]朱航,刘杰,陈天长.采用体波谱振幅相关系数方法研究地震序列的震源机制变化过程[J].地震,2006,26(2):1-11.
[4]山长仑,孙庆文,李镇军.2003年7月青岛震群地震震源机制与震源区应力场特征[J].地震地磁观测与研究,2006,27(5):12-16.
[5]尤晋元,王珊,冯博琴,等.数据挖掘概念与技术[M].北京:机械工业出版社,2007:251-273.
[6]吕子强,肖兰喜,许萍.濮阳地震集中区地震精定位及其预测意义[J].华北地震科学,2008,26(2):12-15.
[7]许明华,曲国胜,李行船,等.注水诱发地震的成因及影响因素探讨[J].西北地震学报,2008,30(3):221-226.
[8]王金州,刘文龙,陈宇卫,等.地震空区及条带附近地震破裂特征的震例研究[J].西北地震学报,2002,24(2):167-173.
[9]万永革.美国L地震和H地震前震源机制与主震机制一致现象的研究[J].中国地震,2008,24(3):216-225.
[10]李英,许康生.2007年甘肃部分地震的震源参数反演[J].西北地震学报,2009,31(4):355-357.
[2]Lund B,Boovarsson R.Correlation of Microearthquake Body-WaveSpectral Amplitudes[J].Bull.Seism.Soc.Amer.,2002,92:2419-2433.
[3]朱航,刘杰,陈天长.采用体波谱振幅相关系数方法研究地震序列的震源机制变化过程[J].地震,2006,26(2):1-11.
[4]山长仑,孙庆文,李镇军.2003年7月青岛震群地震震源机制与震源区应力场特征[J].地震地磁观测与研究,2006,27(5):12-16.
[5]尤晋元,王珊,冯博琴,等.数据挖掘概念与技术[M].北京:机械工业出版社,2007:251-273.
[6]吕子强,肖兰喜,许萍.濮阳地震集中区地震精定位及其预测意义[J].华北地震科学,2008,26(2):12-15.
[7]许明华,曲国胜,李行船,等.注水诱发地震的成因及影响因素探讨[J].西北地震学报,2008,30(3):221-226.
[8]王金州,刘文龙,陈宇卫,等.地震空区及条带附近地震破裂特征的震例研究[J].西北地震学报,2002,24(2):167-173.
[9]万永革.美国L地震和H地震前震源机制与主震机制一致现象的研究[J].中国地震,2008,24(3):216-225.
[10]李英,许康生.2007年甘肃部分地震的震源参数反演[J].西北地震学报,2009,31(4):355-357.
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