2021年日本福岛海域M_(W)7.1地震S-net海底地震动特征  被引量:5

Characteristics of seafloor ground motions of the S-net strong ground motion from the 2021 M_(W)7.1 Off-Fukushima earthquake,Japan

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作  者:崔鑫 胡进军[1,2] 谭景阳 周旭彤 CUI Xin;HU JinJun;TAN JingYang;ZHOU XuTong(Key Laboratory of Earthquake Engineering and Engineering Vibration,Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China;Key Laboratory of Earthquake Disaster Mitigation,Ministry of Emergency Management,Harbin 150080,China)

机构地区:[1]中国地震局工程力学研究所地震工程与工程振动重点实验室,哈尔滨150080 [2]地震灾害防治应急管理部重点实验室,哈尔滨150080

出  处:《地球物理学报》2023年第1期260-271,共12页Chinese Journal of Geophysics

基  金:中国地震局工程力学研究所基本科研业务费专项(2018D18,2021EEEVL0103);国家自然科学基金项目(52078470)资助.

摘  要:2021年2月13日日本福岛县东部海域(Off-Fukushima)发生的M_(W)7.1地震是目前世界最大的海底观测系统——日本海沟地震和海啸海底观测网(S-net)——迄今为止记录到最大的俯冲带地震.为认识海底地震动并探究海陆差异,本文介绍了S-net海域台网及其数据处理的特殊性和必要性,分析了Off-Fukushima地震的地震动幅值、频谱和持时特征,比较了海底与陆地震动衰减特性的异同,对比了近海岸埋置台站、近海沟未埋台站及陆地台站地震动的差异,并与俯冲带地震动模型(GMM)进行了比较.结果表明:Off-Fukushima地震海底水平向PGV和周期大于0.5 s的加速度反应谱值显著大于陆地记录;相比陆地,海底动力放大系数谱向长周期方向偏移,表明海底记录长周期成分更丰富;受到海水的抑制作用,海底记录V/H反应谱比值小于陆地记录;由于海底记录与陆地GMM在路径和场地方面存在差异,水平向PGA及反应谱的残差分布出现明显偏移;海底近海岸埋置台站与近海沟未埋台站的地震动特征存在系统性差异,水平向差异很可能与海底地形有关,而竖向可能受到布设方式对台站与海底耦合程度的影响.本文对Off-Fukushima地震动参数特征和衰减特性的分析结果可为海域地震预警、海域区划和海域危险性分析中的海底地震动特征及GMM的确定提供参考.An M_(W)7.1 subduction earthquake occurred at eastern Fukushima prefecture offshore in Japan on February 13st,2021,which observed by the world′s largest seafloor observation network for earthquakes and tsunamis along the Japan Trench(S-net).The specific steps of S-net data processing as well as the need are introduced.Based on the processed S-net data,the seafloor ground motion characteristics of the amplitude,duration and spectrum were analyzed,and also compared with land data and ground motion models(GMM)for understanding the attenuation of offshore ground motions.We found that,between the land and S-net stations,the offshore values of peak ground velocities(PGV)and spectral accelerations at long periods(>0.5 s)are significantly greater;the peak values of averaged seismic response spectra shift to long periods comparing with land counterparts,which shows the long-period contents of seafloor ground motion are more plentiful;also,averaged curves of V/H response spectra ratio are smaller at S-net stations due to the effect of seawater.The biased residuals at offshore stations were presented because of the difference between land and seafloor for paths and sites.Meanwhile,systemic differences between offshore buried stations and offshore unburied stations were shown,possibility reflecting the influence of seabed topography in horizontal and the effect of ground coupling caused by burying methods in vertical.The study of the Off-Fukushima earthquake in this paper can be used as reference for the needs of earthquake early warning,the zoning and hazard analysis of offshore areas.

关 键 词:海底地震动 S-net M_(W)7.1 Off-Fukushima地震 地震动特性 地震动模型 

分 类 号:P315[天文地球—地震学]

 

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