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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(±0.72km)、106.34°E(±0.76km),震源深度13.2km(±1.15km);序列优势分布方向分别为近SN向和NEE向,分别延伸18km和16km;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。
Based on the seismic activity background and sequence statistics analysis, taking the 5.8 magnitude Alashan Zuoqi earthquake as the research object, the HypoDD double-difference positioning method is used to reposition the seismic sequence to investigate the spatial distribution of aftershocks. Combined with the epicenter area Intensity, mechanism of focal mechanism and repositioning, the rupture surface of 5.8 earthquake was determined. The results show that the epicenter of the Alashan Zuqi 5.8 earthquake is 39.78 ° N (± 0.72km), 106.34 ° E (± 0.76km) and focal depth of 13.2km (± 1.15km) after repositioning. The distribution directions of the sequences are near SN and NEE respectively, extending for 18km and 16km, respectively. The focal depth distribution of the section shows the overall east-dip of the sequence, that is, the focal depth deepens gradually from west to east. Based on the background information of the regional stress field, the characteristics of the historical earthquake rupture, the focal mechanism solutions of the main shock and the sequence reorientation, it is considered that the rupture surface of the Alxaqeqizi 5.8 earthquake should be near the north-south fault plane.