The Tōnankai earthquakes are major

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqua ...

s that affect the Tōnankai region (Southeastern Sea) of

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, between the

Tōkai region The is a subregion of the Chūbu region and Kansai region in Japan that runs along the Pacific Ocean. The name comes from the Tōkaidō, one of the Edo Five Routes. Because Tōkai is a sub-region and is not officially classified, there is s ...

(Eastern Sea) and

Nankaidō is a Japanese geographical term. It means both an ancient division of the country and the main road running through it. The road connected provincial capitals in this region. It was part of the Gokishichidō system. The ''Nankaidō'' encompass ...

(Southern Sea Circuit) region, and are caused by ruptures in the Tōnankai zone of the

Nankai megathrust The is a submarine Trough (geology), trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately offshore. The underlying Fault (geology), fault, the ''Nankai megathrust,'' is the source of the devastating ...

, specifically segments C and/or D. These are a class of Nankai megathrust earthquakes, frequently occurring in combination with a rupture of segment E (Tōkai zone, yielding

Tōkai earthquakes The Tōkai earthquakes () are major earthquakes that have occurred regularly with a return period of 100 to 150 years in the Tōkai region of Japan. The Tōkai segment has been struck by earthquakes in 1498, 1605, 1707, 1854, and 1923. Given the hi ...

), and either in combination with or followed by a rupture of segment A and/or B (Nankai zone, yielding

Nankai earthquakes The are major megathrust earthquakes that affect the Nankaidō (Southern Sea Circuit) region of Japan, west of the Tōnankai region (Southeastern Sea) and Tōkai region (Eastern Sea), and are caused by ruptures in the Nankai zone of the Nankai ...

). The most notable Tōnankai earthquake, and the only earthquake known to have consisted of ruptures in the Tōnankai zone only, is the

1944 Tōnankai earthquake The 1944 Tōnankai earthquake occurred at 13:35 local time (04:35 UTC) on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale (making it the strongest known earthquake of 1944) and a maximum felt intensity of greater th ...

History

The distinction of Tōnankai earthquakes, and the Tōnankai region itself, is a recent one, dating to the

. Nankai (Southern Sea) and Nankaidō (Southern Sea Way), and likewise Tōkai (Eastern Sea) and Tōkaidō (Eastern Sea Way) are historical names and divisions of Japan, but following the 1944 earthquake, it was recognized that there were distinct segments in between these, which could independently rupture, and thus a different category was created.

References

{{DEFAULTSORT:Tonankai earthquakes Megathrust earthquakes in Japan Earthquake clusters, swarms, and sequences