摘要
1918年2月13日,滨海断裂带南澳段发生的M7.5大地震及其引发的海啸成为广东省南澳海域记录在案破坏性最强的地震事件。该案例为研究滨海断裂带结构、破裂机制以及地震海啸灾害提供了重要的研究基础。尽管已有研究揭示了此次地震的基本信息,但其确切的发震机制和海啸特征仍不明确,限制了对该区域地震海啸灾害的评估及减灾防灾策略的制定。本研究采用双差走时重定位方法,对2008~2023年间发生在该区域的ML≥0天然微震进行重新定位;通过重定位后的微震序列,成功刻画出滨海断裂带南澳段断层的三维几何形态,确定其总体走向为61°,倾角接近直立(90°),与前人通过研究控制1918年南澳地震的断层特征一致。为进一步探讨断层发震机制和海啸特性,笔者以确定的断层几何特征为极端情况,采用随机模型方法生成200个地震滑移模型,并通过COMCOT进行大量海啸模拟,评估该情况下海啸的产生能力,并尝试解释1918年海啸的历史记录。通过对比历史海啸记录,初步表明该断层很可能为1918年南澳地震的发震断层位置;南澳海啸很大程度上是由于该断层发生逆冲滑动行为所致,而正断、纯走滑或走滑兼正断滑动行为难以解释历史海啸记录。从统计学角度分析滑移模型产生的海啸特征表明,在南澳岛和大陆沿岸波高趋势一致,最大海啸影响区域集中在南澳岛南部及汕头-闽西大埕湾-东山县沿岸,最大波幅超过4 m;海啸特征主要源于断层中心区域产生3 m以上的滑移,这可能是导致1918年南澳海啸的主要原因。
The offshore region of Nan’ao Island,located within the Littoral Fault Zone,was struck by a MW 7.5 earthquake in 1918,which subsequently triggered a tsunami.This event is historically recognized as the most catastrophic earthquake ever recorded in the Nan’ao offshore area of Guangdong province,providing a valuable natural laboratory for studying fault zone structures,rupture processes,and tsunami hazards.Although previous studies have provided fundamental insights into this event,the seismogenic mechanism and tsunami characteristics of the 1918 Nan’ao earthquake remain poorly understood.However,these aspects are essential for future earthquake-tsunami hazard assessments and for guiding the development of risk reduction and mitigation strategies in the region.In this study,we first relocated microseismicity recorded in the region between 2008 and 2023 using the HypoDD method.Based on a high-resolution microseismicity catalog,we precisely mapped the three-dimensional geometry of the fault plane,revealing a general strike of 61°and a near-vertical dip angle(90°),consistent with the source fault trace identified in earlier studies as responsible for the 1918 Nan’ao earthquake.To further explore the seismogenic mechanism of the newly delineated fault geometry and its associated tsunami characteristics,we adopted the determined fault geometry as an extreme scenario and generated 200 random earthquake slip models using a stochastic modeling approach.These models were then used in large-scale tsunami simulations conducted with COMCOT to assess tsunami generation potential and to interpret the historical tsunami records of 1918.Finally,by comparing the simulation results with historical tsunami data,we aimed to identify the most plausible seismogenic mechanism of the 1918 Nan’ao earthquake.Our findings indicate that the identified fault segment is likely the seismogenic source of the 1918 Nan’ao earthquake.The 1918 Nan’ao tsunami was primarily generated by reverse faulting,while normal faulting,pure strike-slip,or strike-slip with normal faulting mechanisms fail to adequately account for the historical tsunami observations.From a statistical perspective,the tsunami characteristics derived from the slip models reveal consistent wave height trends along the coastlines of Nan’ao Island and the mainland.The most severely impacted areas include the southern part of Nan’ao Island and the coastline stretching from Shantou to Minxi Dacheng Bay and Dongshan County,where maximum wave heights exceeded 4 m.These tsunami characteristics are predominantly attributed to a 3-7 m slip along the central segment of the fault,and this slip is considered the most likely source of the 1918 Nan’ao tsunami.
作者
曾晓燕
邱强
周鹏程
李琳琳
叶秀薇
李志刚
王伟涛
肖奎霖
李发渟
熊成
邓志辉
ZENG Xiaoyan;QIU Qiang;ZHOU Pengcheng;LI Linlin;YE Xiuwei;LI Zhigang;WANG Weitao;XIAO Kuilin;LI Fating;XIONG Cheng;DENG Zhihui(Earthquake Administration of Guangdong Province,Guangzhou 510070,Guangdong,China;Key Laboratory of Earthquake Monitoring and Disaster Mitigation Technology,CEA,Guangzhou 510070,Guangdong,China;South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,Guangdong,China;State Key Laboratory of Tropical Oceanography,Guangzhou 510301,Guangdong,China;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards/School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,Guangdong,China;Guangdong Provincial Key Laboratory of Earthquake Early Warning and Safety Diagnosis of Major Projects,Guangzhou 510070,Guangdong,China)
出处
《大地构造与成矿学》
北大核心
2025年第5期1117-1131,共15页
Geotectonica et Metallogenia
基金
国家重点研发计划项目(2023YFC3008600)资助。
