基于深度学习震相拾取和密集台阵数据构建青海玛多M_(S)7.4地震震源区高分辨率地震目录  

High-resolution earthquake catalog for the focal area of the Qinghai Madoi M_(S)7.4 earthquake based on deep-learning phase picker and dense array

作　　者：郭慧丽[1] 常利军[1] 鲁来玉[1] 吴萍萍[1] 吕苗苗[1] 丁志峰[1] GUO HuiLi;CHANG LiJun;LU LaiYu;WU PingPing;Lü MiaoMiao;DING ZhiFeng(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2022年第5期1628-1643,共16页Chinese Journal of Geophysics

基　　金：中国地震局地球物理研究所基本业务专项(DQJB21Y41,DQJB19B30);国家自然科学基金项目(41704060,U1839209,42074053)共同资助.

摘　　要：高分辨率地震目录有助于描绘断层的精细结构和认识发震断裂的构造形态及发震机制.基于玛多地震科考布设的短周期台阵数据,本文利用深度学习自动拾取P/S波震相、震相关联、绝对定位、相对定位等定位流程,构建了玛多M_(S)7.4地震后第14天至第43天的高分辨率地震目录,揭示了玛多震源区主震西侧以及主震向东20 km区域范围内的地震序列的时空分布特征和发震断层的几何形态.定位结果显示地震的发生频次随时间推移逐渐降低,并趋于平稳.地震序列整体上沿着地表破裂呈现条带状展布,集中分布于破裂带偏北一侧,走向为NWW-SEE.发震深度主要集中在15 km以内.地震剖面图显示发震断层整体向北倾斜,但在深度8~10 km左右,倾角转变为向南倾,表明可能受到局部构造应力或物性差异的影响,破裂面并非单一的平面结构,浅部与深部的破裂存在差异.不同区域的断层形态表现出明显的分段性.在西段(鄂陵湖南)走向为近E-W向,与整体序列的走向呈现一定拐角,断层倾向为近垂直,发震优势层为8~12 km.中间段(鄂陵湖至黄河乡)地震活动性较弱,地震深度浅,集中在2~5 km;以野马滩大桥为界,该段西侧地震序列较宽且连续,东侧地震序列表现为不连续性,出现小的地震空区或稀疏区.东段(主震向东)地震活动性最强,发震深度主要在8~12 km,地震序列在该段有一个向北凸起的弧度,说明该区域可能受到局部构造作用,形成复杂的孕震环境.High-resolution earthquake catalog is helpful to describe the fine structure of faults and to understand the seismogenic mechanism.Based on the seismic data recorded by short-period array which were deployed after Madoi M_(S)7.4 earthquake,we build high-resolution seismic catalogues by using a sequential earthquake association and location workflow which includes a deep-learning phase picker(PhaseNet),and multiple earthquake locating methods.Our high resolution catalog reveals the temporal and spatial distribution characteristics of earthquake sequences and the shape of seismogenic faults in the west of the main shock and 20 km east of the main shock of the Madoi focal area.The results show that the frequency of earthquakes gradually decreases with time and tends to be stable.The earthquake sequence is distributed in strips along the surface fracture and concentrated on the north side of the fracture zone,with the strike of NWW-SEE.The depths of earthquakes are mainly within 15 km.The cross sections show that fracture surface of the seismogenic fault tilts northward as a whole,but the dip angle changes to southward at the depth of 8~10 km.It indicates that the fracture surface is not a single plane structure,which may be affected by local tectonic stress or physical property differences.The fault morphology in different regions is different and shows obvious segmentation.In the western section(south of E′Ling Lake),the strike of the earthquake sequence is near E-W,showing a certain corner with the overall sequence,and the fault dip is near vertical,with a dominant seismogenic layer at 8~12 km.The seismicity of the middle section(from E′Ling Lake to Huanghe Town)is relatively weak,and the depths of earthquakes are shallow concentrating at 2~5 km.Bounded by Yematan Bridge,the earthquake sequence on the west side is wide and continuous,and the earthquake sequence on the east side is characterized by clustering.Small seismic gaps or sparse areas appear here.The east section(east of the main shock)has the stronges

关 键 词：玛多M_(S)7.4地震 深度学习 高分辨率地震目录 地震定位 

分 类 号：P315[天文地球—地震学]