2021年11月17日江苏大丰海域M_(S)5.0地震震源机制与发震构造  

Focal mechanism solutions and seismogenic structure of the M_(S)5.0 earthquake in the sea area near Dafeng,Jiangsu Province on November 17,2021

作　　者：康清清[1] 于悦颖 顾勤平[1] 李玲利[2] 刘芳[3,4] 王维 杨云[1] 王俊菲[1] 许田[1] 周昱辰 孙小航 孙宗强 KANG QingQing;YU YueYing;GU QinPing;LI LingLi;LIU Fang;WANG Wei;YANG Yun;WANG JunFei;XU Tian;ZHOU YuChen;SUN XiaoHang;SUN ZongQiang(Jiangsu Earthquake Agency,Nanjing 210014,China;Anhui Earthquake Agency,Hefei 230071,China;Shanghai Earthquake Agency,Shanghai 200062,China;Shanghai Sheshan National Geophysical Observatory and Research Station,Shanghai 200062,China;Earthquake Prevention and Disaster Reduction Bureau of Shuifu City,Yunnan Province,Shuifu Yunnan 657800,China)

机构地区：[1]江苏省地震局,南京210014 [2]安徽省地震局,合肥230071 [3]上海市地震局,上海200062 [4]上海佘山地球物理国家野外科学观测研究站,上海200062 [5]云南省水富市防震减灾局,水富657800

出　　处：《地球物理学报》2025年第5期1884-1895,共12页Chinese Journal of Geophysics

基　　金：中国地震局地震科技星火计划攻关项目(XH23018C);江苏省地震局局长基金(202301);江苏省333高层次人才项目;国家自然科学基金(41704052);江苏省地震局青年基金(202207)共同资助.

摘　　要：基于江苏、山东和上海等区域地震台网宽频带波形资料,采用gCAP波形反演法获取了2021年11月17日江苏大丰海域M_(S)5.0地震的震源机制解、震源矩心深度和矩震级.节面Ⅰ走向96°、倾角71°、滑动角17°;节面Ⅱ走向0°、倾角74°、滑动角160°,说明震源机制以走滑为主.P轴仰角2°,方位48°,反映震源区主压应力呈NEE-SWW向水平推挤特征,与华东现代构造应力场方向基本一致,揭示其受区域应力场控制.本次地震矩震级为MW5.1,与面波震级M_(S)5.0、近震震级ML5.2较为一致.震源矩心深度为14.7 km,与重定位后的震源初始破裂深度16.5 km较接近,推测该地震发生在南黄海盆地地壳中部,震源由深至浅破裂,震源破裂尺度约3.5 km.重定位后余震展布呈现共轭型带状分布,优势分布方向为NWW向和NE向,NE向展布方向与震源机制解两节面走向均不匹配,震中附近亦没有已探明并公布的NE向断裂;而NWW向展布与节面Ⅰ走向相匹配,与附近的南部坳陷西侧断裂走向基本一致,结合区域重、磁场异常分布情况,初步判定节面Ⅰ为同震破裂面.我们推测本次地震为南部坳陷西侧断裂在NEESWW向水平主压应力作用下挤压错动所致,呈NE向线性展布的零星余震穿越苏北—滨海断裂并向SW延伸至大丰海岸线附近,不排除其下方存在NE-SW向展布的隐伏断层,主震发震断层的错动诱发了该断层活动.Based on the broadband seismometers'waveforms data from Jiangsu,Shandong and Shanghai regional seismic networks,the moment magnitude and focal mechanism solution as well as centroid depth of the M_(S)5.0 earthquake were obtained by the gCAP waveform inversion method.The focal mechanism indicates this earthquake is a strike slip event,with strike/dip/rake of 96°/71°/17°and 0°/74°/160°for nodal planes I and II,respectively.The plunge of P axis is 2°with azimuth angle of 48°,reflecting a horizontal compression mode that the principal compressive stress is featured by a near NEE-SWW direction in the source area.This is consist with the direction of the regional tectonic stress field in the East China block,indicating that the earthquake may be controlled by the regional stress field.The moment magnitude is MW5.1,and it is relatively consistent with the surface wave magnitude M_(S)5.0 and the local magnitude ML5.2.The focal centroid depth of this event is 14.7 km,close to the relocated initial rupture depth of 16.5 km,it imply this event occurred in the central crust of the South Yellow Sea Basin.The source rupture ranges from deep to shallow,with a scale of approximately 3.5 km.The aftershock distribution after relocation presents a conjugate zonal distribution,the two dominant distribution directions are NWW and NE.Since the NE direction distribution does not match each node plane strike of focal mechanism solution,and there is no known NE direction fault structure near the epicenter;The NWW direction distribution matches the node plane strike of focal mechanism solution I,and it is basically consistent with the strike of the nearby western margin fault of the southern depression,we suggest that the node plane I in NWW direction is a coseismic fault plane.Combined with the abnormal distribution of gravity and magnetic fields,we further infer that the M_(S)5.0 earthquake in the sea area near Dafeng was caused by the compression and dislocation of the western margin fault of the southern depression,and it was

关 键 词：大丰海域M_(S)5.0地震 gCAP方法 震源机制解 地震重定位 发震构造 

分 类 号：P315[天文地球—地震学]