2015年阿拉善左旗MS5.8地震序列特征及发震破裂面讨论
Discussion of the Earthquake Sequence and Earthquake Rupture Surface of Alxa Zuoqi MS5.8 in 2015

以2015年阿拉善左旗5.8级地震为研究对象，基于地震活动背景和序列统计分析，利用HypoDD双差定位方法对地震序列进行重新定位，考察余震在空间上的展布特征，并结合震中区烈度、震源机制解和重新定位结果对5.8级地震的发震破裂面进行判定。结果表明，阿拉善左旗5.8级地震为主余型，重新定位后的震中位置为39.78°N（±0.72 km）、106.34°E（±0.76 km），震源深度13.2 km（±1.15 km）；序列优势分布方向分别为近SN向和NEE向，分别延伸18 km和16 km；剖面的震源深度分布显示序列整体东倾，即震源深度由西向东逐步加深。综合区域应力场背景特征、历史地震破裂特征、主震震源机制解和序列重新定位等多方面资料判定认为，本次阿拉善左旗5.8级地震的破裂面应为近南北走向的断层面。
This paper studies the MS5.8 earthquake that occurred in Alxa Zuoqi 2015. Based on the background seismicity and statistical analysis of the sequence, the HypoDD method was used to reposition the earthquake sequence. We examined the aftershocks distribution characteristics in space, and determined the MS5.8 earthquake fracture surface combined with epicentral intensity、focal mechanism solutions, and the results of the re-positioning. The results show the Alxa Zuoqi MS5.8 earthquake is the main aftershock, after relocation, the epicenter is 39.78°N(±0.72 km)、106.34°E(±0.76 km), focal depth is 13.2 km(±1.15 km). The distribution direction of the sequence dominance is near NS and NEE, and extends 18 km and 16 km respectively. The focal depth of the profiles display the overall east-dipping sequence; the focal depth gradually deepened from west to east. The regional stress field background characteristics、historical earthquake rupture characteristics、the main shock mechanism solutions, and serial repositioning information considered judgment, the fracture surface of Alxa Zuoqi MS5.8 earthquake should be near NS-direction surface.