2003年6月青岛震群地震震源机制与震源区应力场特征

Characteristics of focal mechanism and stress field in focus area of Qingdao earthquake sequence in June,2003

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ME≥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 ML≥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.