The Tonankai Earthquake was an interplate earthquake whose source region extended from east off the coast of Kii Peninsula to the Enshunada Sea. A seismic intensity of 6 in JMA scale was observed at Tsu in Mie Prefecture, and Omaezaki in Shizuoka Prefecture (Fig.6-10). There was extensive damage in Shizuoka, Aichi, Gifu, and Mie Prefectures, and slight damage in Osaka and Shiga, Nara, Wakayama, and Hyogo Prefectures (Fig.6-11). In total, this earthquake is said to have resulted in 1,251 dead or missing, 2,971 injured, and the complete collapse of more than 16,000 houses. This earthquake occurred during the Second World War, however, so the survey data varies widely. The damage was greater in areas with soft ground. In Nagoya, 1,024 houses were totally collapsed and 5,820 were partially collapsed. There was also extensive damage of houses, roads, and railroads on the east side of the Tenryugawa River (the Otagawa River basin) in Shizuoka (Fig.6-12). The tsunami struck from Izu Peninsula to Kii Peninsula. The tsunami ranged from 0.5 m to 2 m high in Ise and Atsumi Bays, from 1 m to 2 m high on the Enshunada Sea coast, and 2.5 m high in Shimoda City (Fig.6-13). This earthquake also caused an upheaval of about 15 cm (maximum) from the western bank of Suruga Bay to the Enshunada Sea coast, where continuous subsidence was observed in the period of no earthquakes.

As shown in Fig.6-14, the number of both perceptible and imperceptible aftershocks decayed. The largest aftershock (M 6.4) occurred on December 12.