Nankai megathrust earthquakes

You can help expand this article with text translated from the corresponding article in Japanese. Click [show] for important translation instructions. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Consider adding a topic to this template: there are already 1,203 articles in the main category, and specifying|topic= will aid in categorization. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Japanese Wikipedia article at [[:ja:南海トラフ巨大地震]]; see its history for attribution. You may also add the template {{Translated|ja|南海トラフ巨大地震}} to the talk page. For more guidance, see Wikipedia:Translation.

Nankai megathrust earthquakes (Japanese: 南海トラフ巨大地震, Hepburn: Nankai Torafu Kyodai Jishin) are great megathrust earthquakes that occur along the Nankai megathrust – the fault under the Nankai Trough – which forms the plate interface between the subducting Philippine Sea Plate and the overriding Amurian Plate (part of the Eurasian Plate), which dips beneath southwestern Honshu, Japan. The fault is divided into five segments in three zones, which rupture separately or in combination, and depending on location, the resulting earthquakes are subdivided by zone from west to east into Nankai earthquakes, Tōnankai earthquakes, and Tōkai earthquakes.

The earthquakes occur with a return period of about 90–200 years, and often occur in pairs, where a rupture along one part of the fault is followed by a rupture elsewhere on the fault, notably the 1854 Ansei-Tōkai earthquake and the 1854 Ansei-Nankai earthquake the next day, and the 1944 Tōnankai earthquake, followed by the 1946 Nankaidō earthquake. In one recorded case (the 1707 Hōei earthquake) the fault ruptured along its entire length. All of these great earthquakes have resulted in damaging tsunamis, which are particularly damaging due to the Japanese population being concentrated on the Taiheiyō Belt, especially the coastal cities of Tokyo, Yokohama and Osaka, the three most populous cities in Japan. The area remains seismically active, and future earthquakes are anticipated, with a high risk of a Nankai earthquake in the near future, which could be potentially very damaging.