三河—平谷8级震区地壳三维密度结构反演研究  

Study on inversion of three-dimensional crustal density structure in the Sanhe-Pinggu M8 earthquake area

作　　者：张明辉 申重阳[1] 杨光亮[1] 谈洪波[1] 王嘉沛 杨雄 孙凯[3] 申宇彤 ZHANG MingHui;SHEN ChongYang;YANG GuangLiang;TAN HongBo;WANG JiaPei;YANG Xiong;SUN Kai;SHEN YuTong(Institute of Seismology,China Earthquake Administration,Wuhan 430071,China;Second Crust Monitoring and Application Center,China Earthquake Administration,Xi′an 710054,China;Taiyuan University of Technology,Taiyuan 030024,China;Guangdong Earthquake Agency,Guangzhou 510070,China)

机构地区：[1]中国地震局地震研究所,武汉430071 [2]中国地震局第二监测中心,西安710054 [3]太原理工大学,太原030024 [4]广东省地震局,广州510070

出　　处：《地球物理学报》2025年第3期882-897,共16页Chinese Journal of Geophysics

基　　金：国家重点研发课题(2017YFC1500204,2018YFE0206100);国家自然科学基金(42374105,42204089,41204014,U1939204);中国地震局地震研究所基本科研业务费专项资助项目(IS202336350,IS202326341)共同资助。

摘　　要：1679年三河—平谷8级地震位于燕山褶皱与华北平原的过渡部位,其浅部和深部孕震构造动力环境仍不够清楚.本文利用三河—平谷震区高分辨率布格重力异常数据和最新全球重力场模型WGM2012数据,采用趋势分析、小波多尺度信号分离技术和迭代反演算法获取了震区莫霍面起伏和地壳内部密度扰动分布图像.研究结果表明:1679年三河—平谷8级地震位于局部重力高和重力低的过渡部位,易于构造应力应变集中和积累,同时该地震与1976年唐山地震类似,均位于太原—延庆布格重力异常梯度带(亦即中国东部重力梯级带的中段)和莫霍面陡变带的东侧;震区(39.4°N—40.3°N,115.7°E—117.5°E)地壳三维密度结构显示研究区呈中部密度高、南北密度低的特征,高低密度体多受断裂分割或限制呈交替分布,与地质隆起和凹陷相间的特点相一致,推断高密度体可能因地幔岩浆上涌侵入与熔融活动所形成,而低密度体则可能受华北平原伸展、燕山隆起均衡等制约所引起;中部大兴高密度体北东上隆活动对夏垫断裂形成与发育、三河—平谷地震孕育与发生至关重要;为此提出了三河—平谷地震的岩浆上涌与断层联合作用发震模式.该结果可为华北克拉通破坏演化过程中的构造-岩浆活动研究、首都圈地震危险性判定和巨震震源识别等提供重要参考.The 1679 Sanhe-Pinggu M8 earthquake occurred in the transition zone between the Yanshan fold belt and the North China Plain,but its shallow and deep seismogenic tectonic dynamic environment is still unclear.This study utilizes the high-resolution Bouguer gravity anomaly data and the latest global gravity field model WGM2012 data.Firstly,the trend analysis method is utilized to obtain the trend anomaly signals related to the Moho.Subsequently,these trend anomaly signals are combined with the results of Wavelet Multi-scale signal separation through weighted averaging to derive the regional gravity anomalies in the study area.The iterative inversion algorithm is further applied to obtain spatial images of Moho fluctuations and density disturbances distributions within the Earth's crust.The results reveal that the 1679 M8 Sanhe-Pinggu earthquake occurred at the transitional zone between area of high and low local gravity anomalies.Within this zone,the gravity anomaly contours exhibit a curvature from NNE to NE,creating an environment conducive to the concentration and accumulation of tectonic stress and strain.It is similar to the 1976 Tangshan earthquake,both located on the eastern side of the Taiyuan-Yanqing Bouguer gravity anomaly gradient zone(the middle segment of the gravity gradient zone in eastern China)and the Moho abrupt change zone.The three-dimensional density structure of the crust in the epicentral region(39.4°N-40.3°N,115.7°E-117.5°E)reveals a characteristic pattern of high density in the central part and low density in the north and south.High and low density bodies are mostly segmented or confined by faults,showing an alternating distribution that corresponds to the geological features of alternating uplifts and depressions.It is inferred that the high-density bodies may be formed due to the upwelling and intrusion of mantle magma,as well as melting activities,while the low-density bodies may be caused by the extension of the North China Plain and the isostasy of the Yanshan uplift.The uplifting

关 键 词：三河—平谷地震 重力反演 莫霍面起伏 三维密度结构 孕震环境 发震模式 

分 类 号：P315[天文地球—地震学] P312[天文地球—固体地球物理学]