仙游地震序列中小地震震源机制解特征

利用福建地震台网记录的数字地震波形,采用基于P波初动和S/P振幅比(HASH)方法,反演了2010年8月至2014年12月间发生在福建仙游地区ML2.0级以上地震的震源机制解。结果表明,仙游地震序列中小地震震源机制解一致性较好,其节面走向、倾角及滑动角以及P、T轴优势分布十分明显。节面走向优势方向为北西向,与该区域沙县—南日岛断裂走向一致,震源破裂类型为近直立右旋走滑型。序列的发生主要受控于近南北向主压应力,与福建地区背景应力场方向存在一定差异。分析认为,仙游地震序列的发生主要受控于仙游地区小尺度区域的构造应力场,金钟水库水位变化与序列显著地震活动存在一定相关性,但对仙游地区构造应力场影响不明显。

FOCAL MECHANISM SOLUTION CHARACTERISTICS OF MODERATE AND SMALL EARTHQUAKES IN XIANYOU AREA

Based on waveforms from Fujian seismic network,using the P wave first motion polarity and S/P amplitude ratio (HASH)method,calculated the focal mechanisms of ML≥2.0 earthquakes occurred from 2010 August to 2014 December in Xianyou Area. The results show that the focal mechanisms of ML≥2.0 events are similar,its strike、dip、rake and P, T axis predominant distribution is obvious. The NW direction plane of mechanisms solutions consistent with the direction of Shaxian-Nanridao fault system. The type of focal rupture is nearly vertical right-lateral strike-slip. The occurrence of the sequence is mainly controlled by the NS direction principal compressive stress, which is different to the direction of the stress field in Fujian area. The analysis shows that the occurrence of the Xianyou earthquake sequence is mainly controlled by the tectonic stress field in the small scale of Xianyou area, and have a certain correlation with the changes of Jinzhong reservoir’s water level,but the relationship between water level and tectonic stress field is not obvious.