Evidence from boulders for extraordinary tsunamis along Nankai Trough, Japan
Evidence from boulders for extraordinary tsunamis along Nankai Trough, Japan
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日本南海海槽沿岸异常海啸的巨石证据
DOI：
10.1016/j.tecto.2022.229487
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发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
Tomoo Echigo
中科院分区：
文献类型：
--
作者：
Yuichi Namegaya ;Hideaki Maemoku ;Masanobu Shishikura ;Tomoo Echigo
日本西部南开海槽沿岸地区多次遭受灾难性海啸袭击。已知的最大地震是1707年的CE Hoei地震(Mw8.7)，沿着整个海槽破裂了板块界面。我们提出了更大海啸的证据，这些巨石散布在面向南开海槽的日本久本县桥贵-IWA英安岩侵入体(HID侵入体)的陆地一侧。虽然巨石来自侵入性岩石，但它们的位置距离侵入性岩石高达100米，表明它们是通过海啸和/或风暴潮运输的。对2012年台风前后的激光扫描地形与1976年和2007年拍摄的航空照片进行比较表明，风暴潮并没有移动任何较重的巨石。模拟海啸作用在巨石上的流体力与静摩擦力的比较表明，1707年前的地震海啸并没有移动所有的巨石。因此，巨石的分布证明，过去曾发生过比1707年公元前地震更大的海啸。我们还表明，伸展断层或板块边界上的大滑动是比1707年公元前地震更大的潜在地震来源，可能会引发巨石运动。
The coastal area along the Nankai Trough, western Japan, has been repeatedly hit by catastrophic tsunamis. The largest known earthquake, the 1707 CE Hoei earthquake (Mw8.7), ruptured the plate interface along the entire trough. We present evidence for even larger tsunamis from boulders scattered on the landward side of the Hashigui-iwa dacite intrusion (the HID intrusion), Kushimoto, Japan, which faces the Nankai Trough. Although the boulders derive from the intrusive rock, their locations, which are up to 100 m from the intrusive rock, suggest their transport by tsunamis and/or storm surges. Comparisons of laser-scanned topographies before and after a typhoon in 2012 and aerial photographs taken in 1976 and 2007 indicate that storm surges did not move any of the heavier boulders. A comparison of the fluid forces caused by simulated tsunamis acting on the boulders with the static frictional force indicates that the 1707 CE earthquake tsunami did not move all the boulders. The distribution of the boulders is thus evidence that tsunamis larger than that caused by the 1707 CE earthquake occurred in the past. We also show that large slip on a splay fault or the plate boundary is a potential source of earthquakes larger than the 1707 CE earthquake that could have set the boulders in motion.