2003年内蒙古巴林左旗M_S5.9地震发震构造

Seismogenic Structure of 2003 Bailinzuoqi M_S5.9 Earthquake in Inner Mongol ia, China

2003年8月16日内蒙古巴林左旗MS5.9地震在大兴安岭地区显得较为突出,为该区有记载以来的最高震级地震,突破了以往我们对这一地区地震构造背景的认识。地震发生后,相关考察报告与研究文献对于其发震构造的认识存在分歧。本项研究基于对该地震相关的地震学资料的收集,结合震区及邻区的航卫片判读,通过野外地质地貌调查,发现了NW向水泉子沟-天山口断裂的存在。初步认定该断裂长度为60km,其中,该断裂西北段即水泉子沟-西山湾段的活动时代相对较新,断错地层年代为距今498±49ka,断层泥ESR样品的测试年龄为距今325±32ka。综合此次地震的震源机制解、震害分布特征以及余震序列等研究结果,推断水泉子沟-西山湾段为该地震的发震断裂。

The determination of seismogenic structure is of great importance in seismic hazard analysis （SHA） whereas the identification of seimogenic structure of moderate earthquake is quite challenging. It＇s absolutely well-marked that the 2003 Bailinzuoqi Ms5.9 earthquake occurred because of the low seismicity of the whole Dahingganling Uplift. The penetrating research of seismogenic conditions in which ＂2003 event＂ took place can make sense to the understanding of seimogenic structure of Dahingganling Uplift. According to the tough field investigation that last more than two months in the target area, we find the Shuiquanzigou-Tianshankou fault that caused the 2003 earthquake reveals the distribution of this fault and the latest active information, that is, the Shuiquanzigou-XishanwanTianshankou fault consists of Shuiquanzigou-Xishanwan section which cuts the stature of MidPleistocene, being active in Mid-Pleistocene derived from ESR dating of fault clay and YangshulinTianshankou section based on the materials collection of geophysics and seismology related to this event and the interpretation of remote sensing images. Finally, the authors consider the section of Shuiquanzigou-Xishanwan as the seismogenic fault based on the synthetical analysis of the focal mechanism, the distribution of the seismic damage and aftershocks.