福建仙游地区高精度地震震源定位及深部断裂特征  

High-precision Earthquake Locations and Deep Fault Characteristics Beneath Xianyou Area,Fujian Province

作　　者：关露凝 江国明[1] GUAN Luning;JIANG Guoming(School of Geophysics and Information Technology,China University of Geosciences,Beijing 100083)

机构地区：[1]中国地质大学(北京)地球物理与信息技术学院,北京100083

出　　处：《现代地质》2023年第1期40-47,共8页Geoscience

基　　金：国家自然科学基金项目(41974060)。

摘　　要：福建仙游位于福建省东南沿海中部,其周边地区历史地震活动较平静,属于弱震区。但自从该地区的金钟水库于2010年5月下闸蓄水后,库区附近的地震活动性随之增强。为深入了解该地区的地震活动性、地震分布特征以及寻找隐伏断层,利用中国地震局提供的地震初至震相数据,使用双差定位方法对仙游地区近10年发生的地震进行重定位,获得了更为精确的震源位置,并根据重定位结果模拟深部断裂,寻找隐伏断层。结果显示:(1)重定位后的震源位置更加集中,按照发震时间可分为4个活动区,主要沿沙县—南日岛的次级断裂石苍断裂两侧北西向线性分布。(2)重定位后仙游震群的震源深度主要为8~11 km。石苍断裂左侧地震条带震源深度为6~12 km;右侧地震条带呈现明显的分层现象,上层西北侧地震较为分散,东南侧地震分布较紧凑,震源深度同左侧一样为6~12 km,而下层地震较少,震源深度为14~23 km。(3)根据重定位后的震源位置,利用奇异值分解法拟合得到三个深部断层面,其倾向均为南西向,走向为北西向,与石苍断裂和潼关断裂的倾向和走向一致。结合前人研究成果和本研究结果,推测石苍断裂并不是主发震断层,而是其两侧存在的深部断裂(高倾角隐伏断层)由于受到水库蓄水间接影响,从而触发构造地震。Xianyou area is located in the middle part of the Fujian southeastern coastal region.Historical seismicity events around Xianyou are relatively rare,and the area belongs to a weak seismic area with few earthquakes.However,since Jinzhong Reservoir in this area started to operate in May 2010,earthquake activities became more frequent near the reservoir area.To deeper our understanding in the seismicity,seismic distribution characteristics,and search for local concealed faults,based on the seismic travel time data provided by the China Seismological Bureau,the double-difference relocation method was used to relocate the earthquakes in the Xianyou area in the past decade,and more accurate source positions were obtained.According to our results,fitting deep faults to search for concealed faults.The results also show that:(1)The relocated hypocenters are more concentrated.They can be divided into four active regions according to earthquake occurrence time,and are mainly distributed along the NW direction on both sides of the secondary Shicang fault at Shaxian-Nanridao.(2)Focal depth of Xianyou earthquake swarm after relocation is mainly 8-11 km.The focal depth of the seismic belt on the left side of the Shicang fault is 6-12 km;The seismic strip on the right side shows obvious stratification.The earthquakes on the northwestern side of the upper layer are relatively disperse,while those on the southeastern side are relatively intensive.The focal depth is 6-12 km on the left side,while there are fewer earthquakes on the lower layer,with focal depth of 14-23 km.(3)According to the relocated source position,three deep fault planes are fitted by the singular value decomposition method,and they dip to the southwest and strike northwest,consistent with the dip and strike of the Shicang and Tongguan faults.Based on previous studies and our results,we speculated that Shicang fault is not the main seismogenic fault,but the deep steeply concealed faults on both sides of it,which are indirectly affected by the reservoir impoundmen

关 键 词：福建仙游 双差地震定位 水库诱发地震 模拟深部断裂 隐伏断层 

分 类 号：P315[天文地球—地震学]