The earthquakes occur with a return period of about 90 – 200 years , and often occur in pairs , where a rupture along part of the fault is followed by a rupture elsewhere , 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 and Osaka , the two most populous 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
1944 Tōnankai earthquake
1944 Tōnankai earthquake
Nankai megathrust earthquakes