1966年邢台强震群震前、 同震和震后断层运动特征分析

在1966年3月邢台强震群水准观测基础上, 本文首先对同震位移和数值模拟结果进行了对比, 认为邢台强震群发震断层浅层是牛家桥阳断层和永福庄断层, 深部发震断层是倾向北西的北东向断层; 然后以区域水准观测为约束, 通过反演给出了邢台强震群震前断层无震滑移、 同震断层位错和震后断层余滑空间分布。 结果表明, 震前显著无震滑移主要发生在3月8日6.8级前震的发震断层上, 而3月20日宁晋7.2级和6.7级地震发震断层深部同震位错相对弱的断层段, 震前也存在较为明显的无震滑移; 震后断层余滑主要分布在束鹿凹陷西侧的牛家桥阳断层。 从邢台强震群过程中断层运动时空演化特征可以看出, 强震破裂成核过程中震前断层无震滑移既可能发生于前震发震断层, 也可能发生于主震发震断层, 震后断层位移空间分布与同震位错具有互补性; 而震前断层无震滑移是否为有关震前前兆的真正原因, 是值得进一步深入研究的问题。

Pre-, Co-, and Post-seismic Fault Movement Features of the 1966 Xingtai Strong Earthquake Swarm

Based on the leveling observation data of the March 1966 earthquake swarm in Xingtai, this paper compared observed coseismic displacement and results from numerical simulation, thus inferred shallower Niujiaqiaoyang Fault and Yongfuzhuang Fault and a deeper NW oriented, NE trending fault as the causative faults of Xingtai earthquake swarm. Constrained by leveling data, this paper gave the spatial distribution of pre-, co-, and post-seismic movement of the faults. The results show that significant aseismic slip before the earthquake occurs mainly on the causative fault of March 8 M_S6.8 earthquake, and also occurs on the segments in the causative fault of the March 20 Ningjin M_S7.2 and 6.7 earthquakes with weak coseismic displacement. The after slip occurs mainly in the Niujiaqiaoyang Fault in the west of Shulu depression. From the spatial and temporal features of fault movement of the Xingtai earthquake swarm, we conclude that in the process of earthquake rupture nucleation, aseismic slip before the earthquake may occur in causative fault of foreshock, and also may occur in causative fault of mainshock. The distribution of afterslip shows a complementary spatial pattern with coseismic displacement. Whether the aseismic slip before the earthquake is the reason for some of pre-earthquake precursors is an issue worth further studying.