设定琉球海沟发生罕遇地震评估我国东南沿海地区的海啸风险

根据构造相似条件分析,琉球海沟与日本海沟、智利海沟、印尼巽他海沟一样具备发生9级罕遇超巨大地震的可能。在对近几年来全球发生的超巨大地震参数及构造对比分析的基础上,设定琉球海沟9.0级地震参数,并将其引发的海啸进行数值模拟研究。结果表明,该地震可引发初始波高为8m的海啸,台湾东北部半小时后遭受10m以上海啸,3~4小时左右传至浙南、闽北沿岸,近岸各处波高在1~2m;5小时左右传至浙北、粤北沿岸,浙江近岸各处波高在2m左右,广东沿海、台湾海峡由于台湾岛的正面阻挡,海啸波高低于50cm;8小时后靠近上海海岸线,最大波高约1m。海啸的上岸高度与海岸附近的海深和海岸线的形态密切相关,我国东南海域地形变化复杂、海湾众多,对海啸波有放大作用,模拟结果可能比实际海啸偏小。我国沿海地区分布着不少已建和在建的核电厂,在核电设计时未考虑海啸,一旦发生这种罕遇地震海啸则影响不可忽视,尤其是若与风暴潮、天文大潮叠加则可能出现严重后果。由于核电安全要求万无一失,故须制订有效预警和应对措施。

Numerical Simulation of Risk in the Southeast Coastal Region of China Owing to a Rare Earthquake-induced Tsunami in the Ryukyu Trench

Based on their tectonic similarities,the Ryukyu trench is as likely to experience a rare mega-thrust earthquake as the Japanese,Chilean,and Sunda trenches.Based on an analysis of the mega-thrust hypocenter parameters along trenches in recent years,this study proposed a scenario of an earthquake of M_W9.0 in the Ryukyu trench and then simulated the resulting earthquake-induced tsunami.Our study results indicated that the initial tsunami reached a height of up to 8 m,then propagated to northeast Taiwan half an hour later and increased in height to over 10 m.Three to four hours later,the tsunami reached the south coast of Zhejiang province and the north coast of Fujian province,and its height was then 1~2 m.Roughly five hours later,the tsunami propagated to the north coasts of Zhejiang and Guangdong provinces,at heights of approximately 2 m and less than 0.5 m,respectively.The tsunami reached the shoreline of Shanghai eight hours later,and its maximum height was then approximately 1 m.These simulated tsunami height data tend to be lower than would occur in reality because of the shoaling effect in the bays along the southeast China shoreline.Owing to the presence of a number of nuclear power plants along the coast of southeast China,the potential for tsunami impact on these plants should not be ignored in the event of a rare earthquake in the Ryukyu trench.We recommend that nuclear plants take measures to prevent potential damage from tsunami hazards.