December 20, 1946 Tsunami: S Coast, Honshu, Japan

Reference #414:

On December 21, 1946, at 4:19 [local time] there was a catastrophic earthquake on the southwest of Japan in the Nankai area. The number of homes destroyed directly by the earthquake was 2,598; 1,443 people died. In addition, 1,451 homes were washed away by the ensuing tsunami waves.

A sizeable tsunami rolled onto the coast of the Kii Peninsula and Shikoku Island. The tsunami was strongest on the east coast of Kii Strait, from Fukuro to Mio, where the rise of water was 6 m. The rise was slightly less on the western coast of the strait, and increased from south to north (from 2-3 to 4.5-5 m). In Tosa Bay, the maximal rise of water was observed in the Susaki region, where it also reached 5 m, but the impact of the tsunami was considerably weaker here than in the Kii Strait.

According to visual observations, the first wave was the highest at Sinjo and Kanno'ura, while the second wave was the highest at most other points, and the third was highest far into Susaki Gulf. The records for the tide gauges situated on the eastern shore of the Kii Strait, showed that the tsunami began here with an ebb, which was followed by a large rise in the water level.

The following is known about the effects of the tsunami at individual points. On both shores of the entrance to Yura Bay (at Katakui, Okui, Kashiwa and west of Kamiya), the rise of water was 2.7-2.8 m. According to residents, the tsunami advanced slowly here, and the water rose gradually; at Katakui, the sea bottom was exposed. East of the Kashiwa-Itoya line, the rise of water increased markedly, reaching 3.9 m at Yura and Fukui, and 4-4.2 m at the head of the bay.

At Tokushima, the water rose only 1.5 m and the incursion did no damage. The rise of water increased towards the head of Akaishi Bay, which constricts in a southwestern direction. At Komatsushima, it was only 1.7-1.9 m (possibly due to the protection of the breakwater) and at Yokosu, the water did not cross a dike 2 m high, but between Kanaiso and Akaishi, it even flowed across a dike 3 m high. At Akaishi, the water rose 2.8-2.9 m. The tsunami approached Akaishi in the form of a step, and the run-up was rather strong. No little damage was done: dikes were destroyed, homes were flooded, and different objects were carried away.

At Shishikui, partly screened from the south by a rocky cape, the rise of water on shore was 3.3 m. Protective tree stands, planted along the coast, somewhat weakened the thrust of the water, and for the most part it overflowed along the mouth of the Shishikui River. The broken surf rose up river. On the south side of this cape, the rise of water was 4.4 m. At Kanno'ura, situated somewhat to the west, the rise of water was rather high, but the coast did not suffer, except for the top of a little bay which constricts to the north. The ships in the harbor did not run aground which indicates the low speed of currents at the steep and deep shore.

At Kanno'ura and at Cape Muroto, according to accounts, the movement of the water began with an ebb tide. Muroto Port dried up as far as the breakwater. At Cape Muroto, both the rise of water and the wave periods were less than on other sections of the coast. At Kochi, a large area of the subsided shore was flooded with water, but the tsunami itself was very weak. The tsunami practically did not enter Urado Bay which has a narrow, long and very shallow entrance.

The tsunami was registered far from the source, on the coast of the Hawaiian Islands and North and South America.

See individual runup locations for more information..

Reference #150:

Lists 1,362 deaths, 11,661 houses destroyed, 1,451 houses washed away, 2,598 houses burned down.

View a calculated tsunami-travel-time map.