基于俯冲带动力学参数评估琉球海沟对我国东南沿岸的海啸威胁

Tsunami Potential Threat from the Ryukyu Trench on Chinese Coast Based on Subduction Zone Dynamics Parameters

为了提升我国沿海海啸防灾减灾能力,加强民众海啸风险防范意识,系统地分析了琉球海沟俯冲带地震所引发海啸对我国大陆东南沿岸及台湾东部的潜在威胁,基于逻辑树与蒙特卡洛随机模拟的概率性方法对其海啸风险进行定量评估.考虑到琉球海沟历史地震记录稀少,基于俯冲带的动力学参数对该区域潜在地震的最大震级进行了修正.与此同时,结合前人对该区域的古海啸研究成果建立了海啸源参数逻辑树,分析了评估结果的不确定性.研究结果表明,2000年重现期下台湾东部宜兰县和花莲县周边的最大海啸波幅可以达到2~3 m;上海和浙江舟山的最大海啸波幅也能达到0.6 m和0.8 m左右.由于琉球海沟历史上没有灾害性海啸,其对东南沿岸和台湾东部的海啸威胁难以量化评估,模拟结果为今后该地区的海啸防御提供了理论依据.

In order to improve tsunami mitigation capabilities along the coast of China and to increase public awareness of tsunami hazards,this paper systematically analyses the potential threat of tsunamis caused by earthquakes in the Ryukyu Trench subduction zone off the southeast coast of China and the eastern part of Taiwan Province.We quantitatively assess their tsunami hazard based on a probabilistic approach of logic tree and Monte Carlo simulation.Considering the scarcity of historical earthquake records in the Ryukyu Trench,we determined the maximum magnitude of potential earthquakes in the region based on the dynamic parameters of the subduction zone.At the same time,a logical tree of tsunami source parameters was constructed to analyse the uncertainty of the assessment results by integrating previous research results on paleotsunamis in the region.The results show that the maximum tsunami wave amplitude can reach 2-3 m around Yilan and Hualien counties in eastern Taiwan Province in the return period of 2000 years;the maximum tsunami wave amplitude can also reach about 0.6 m and 0.8 m in Shanghai and Zhoushan at the same time.Therefore,although there are almost no catastrophic tsunami events in the historical record of the Ryukyu Trench,its tsunami threat to the southeast coast of China,especially the eastern part of Taiwan,cannot be ignored.