2003年6月青岛震群地震震源机制与震源区应力场特征
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摘要
利用山东数字地震台网记录的2003年6月青岛震群波形资料,由P波、SV波、SH波初动和它们之间的振幅比,联合计算了ML≥2.9地震的震源机制解。结果表明,震群发生前期,震源机制较为一致,P轴与北东东(80°)近水平方向的区域应力场主压应力方向一致,震群发生后期震源机制变化相对较大。上述现象相对于强震P轴方向与区域应力场主压应力方向一致,而余震P轴絮乱的现象有一定的相似性。但相对于强震在震后引起的主压应力方向变化(约40°~96°)来说,青岛震群地震引起震源区P轴的变化(约45°)并不显著。
In this paper, based on the digital earthquake records of Qingdao earthquake sequence recorded by telemetering seismic network of Shandong province in June,2003, we study the P wave, SV wave, SH wave onsets, amplitude ratio and calculate the focal mechanism solutions of earthquakes M_L≥ 2.9. The results show that seismic mechanism is comparatively consistent in the forepart of earthquake swarm and stress P axis accords with the principal compressive stress direction of region stress field that is nearly horizontal NEE 80°, in the posterior, focal mechanism has a comparatively obvious change. Relative to the phenomenon that main shock stress P axis direction is consistent with the orientation of compressive principal stress and aftershock P axis is foul-up, the above fact has some comparability. But comparing with the change (about 40°~96°)of the principal compressive stress direction caused by strong shock, the change(about 45°) of source area stress field P axis has no precursory meaning.
In this paper, based on the digital earthquake records of Qingdao earthquake sequence recorded by telemetering seismic network of Shandong province in June,2003, we study the P wave, SV wave, SH wave onsets, amplitude ratio and calculate the focal mechanism solutions of earthquakes M_L≥ 2.9. The results show that seismic mechanism is comparatively consistent in the forepart of earthquake swarm and stress P axis accords with the principal compressive stress direction of region stress field that is nearly horizontal NEE 80°, in the posterior, focal mechanism has a comparatively obvious change. Relative to the phenomenon that main shock stress P axis direction is consistent with the orientation of compressive principal stress and aftershock P axis is foul-up, the above fact has some comparability. But comparing with the change (about 40°~96°)of the principal compressive stress direction caused by strong shock, the change(about 45°) of source area stress field P axis has no precursory meaning.
引文
陈立德,付虹.2003.地震预报基础与实践[M].北京:地震出版社,56~63
刘杰,郑斯华,康英等.2004.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,24(1):19~26
Snoke J A,Munsey J W,Teague A Get al.1984.Aprogramfor focal mechanismdetermination by combined use of polarityand SV-P amplitude ratio data[J].Earthquake Notes,55(3):15
刘杰,郑斯华,康英等.2004.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,24(1):19~26
Snoke J A,Munsey J W,Teague A Get al.1984.Aprogramfor focal mechanismdetermination by combined use of polarityand SV-P amplitude ratio data[J].Earthquake Notes,55(3):15
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