Megathrust earthquakes of magnitude ~ 8 and ensuing large tsunamis occur along the Nankai and Suruga troughs, central Japan, with a recurrence interval of 90–270 years since an AD 684 Hakuho earthquake. Historical records show that the AD 1854 Ansei-Tokai earthquake caused coseismic uplift of ~ 1 m in coastal areas west of Suruga Bay, including the Shimizu Plain, east Shizuoka Prefecture. The 1361 Shohei Tokai earthquake was accompanied by coseismic uplift, but no evidence has been found to indicate uplift before the earthquake. This study examined sediment cores recovered from the coastal beach ridge in the Shimizu Plain using sedimentological and paleontological analyses and radiocarbon dating. We infer from the results that a relative sea-level fall of 1.6 m took place at AD 398–428. This coincides with archeological evidence suggesting the occurrence of a large earthquake in west Shizuoka Prefecture in AD 400. This combination of evidence indicates that the drop in sea level was caused by coseismic uplift associated with a megathrust rupture along the Suruga Trough, with a recurrence interval of ~ 500–1000 years. The results also indicate that a megathrust rupture occurred in the region from the Eastern Nankai Trough to the Suruga Trough at ca. AD 400.

中文翻译：

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日本中部清水平原沿海低地矿床到公元400年同震隆升的地质证据

在日本中部的南海槽和骏河槽中发生了大约8级的特大推力地震，随后发生了海啸，自公元684年白凤地震发生以来，其复发间隔为90-270年。历史记录表明，公元1854年安塞-东海地震在Suruga湾以西的沿海地区（包括静冈县东部的清水平原）引起了大约1 m的同震隆升。1361年的Shohei Tokai地震伴随着同震隆起，但没有证据表明地震前隆起。这项研究使用沉积学和古生物学分析以及放射性碳年代测定法研究了从清水平原沿海海滩山脊中回收的沉积物岩心。我们从结果推断，在公元398–428年，相对海平面下降了1.6 m。这与考古学证据相吻合，表明公元400年静冈县西部发生了大地震。这些证据表明，海平面下降是由于同震隆升引起的，这与沿Suruga槽的特大推力破裂有关，且复发间隔〜500–1000年。结果还表明，在东南海海槽到苏鲁河海槽的区域内，大约在2000年发生了巨大的推力破裂。公元400年。结果还表明，大约在东南海海槽到苏鲁加海槽的区域发生了巨大的推力破裂。公元400年。结果还表明，大约在东南海海槽到苏鲁加海槽的区域发生了巨大的推力破裂。公元400年。