汶川M_s 8.0级地震强震记录所揭示的地震断层特征分析

基于2008年5月12日汶川Ms8.0级地震的强震台站记录,对比发震断层两侧的峰值加速度与地表破裂带上同震位移的分布特点,探讨了地震动强度分布特征与地表破裂位移分布之间的相关关系。分析近断层典型台站的强震动记录时程特征,获得了强地震动记录中所包含的断层破裂过程和破裂习性信息,从强震观测记录的角度进一步证实了汶川地震主震的多次破裂特征。结果表明,汶川地震主震至少包含了4次地震破裂事件,最主要的前两次破裂事件分别对应映秀—北川断裂段和北川—南坝断裂段的破裂过程,后两次破裂事件释放的能量相对较小,应该是第二次破裂过程触发局部次级破裂所引起的。此外,垂直于断层的峰值加速度剖面揭示的发震断层的高倾角逆冲特性,与地震地质调查和小震精定位等确定的相应结果是一致的。

The causative fault properties from strong-motion records of Ms 8.0 Wenchuan earthquake

Based on analysis of strong motion records of Wenchuan Ms 8.0 earthquake on May 12,2008,we compared and discussed the distribution characteristics of peak ground acceleration(PGA) and coseismic displacements to disclose the correlation between earthquake intensity distribution and surface rupture.From the recording waveforms of typical near-fault strong motion stations,we can extract valuable information of fault rupture process and behaviors contained in acceleration time-histories,which further confirmed the multi-rupture process by means of strong motion observation.The results show that the Wenchuan earthquake contained at least 4 times of rupture events during the whole process.The most important first two events corresponded respectively to ruptures occurred in the Yingxiu-Beichuan fault and the Beichuan-Nanba fault.The other two events,in which the energy released was relatively small,were triggered probably by the second rupture event occurred on the Beichuan-Nanba fault.In addition,the peak acceleration perpendicular to the fault indicated that the causative fault was a high-angle reverse fault,which is consistent with the results of geological survey and aftershock relocation.