May 21, 1792 Tsunami: Shimabara Bay, Kyushu Island, Japan

Ref #9675:

1792, May 21. 14,524 deaths. Figures from Katayama indicate 9,528 fatalities along the Shimabara peninsula and an additional 4,996 fatalities in Higo and Amakusa provinces across Ariake Sea. The vast majority were killed by the tsunami, the avalanche reaching only the southern outskirts of Shimabara city.

Ref #414:

1792 (mistakenly 1793), May 1. In the winter of 1791-1792, there was a strong eruption of Unzen volcano (Nagasaki Prefecture, Kyushu Island), which lasted four months. It did great damage to the vicinity of the volcano and was accompanied by frequent underground shocks, as a result of which homes collapsed here and there. Some people were killed. The side of the mountain collapsed at the end of the eruption, and this caused a destructive tsunami. The accounts of the eruption in the Japanese literature are somewhat contradictory, especially with respect to dates.

On November 13, 1791, tremors of the volcano began, rumbling was heard, and collapses occurred. On May 21 (April 1) at 18:00 [Local Time], the earth again "shook" strongly twice, and in an instant, the steep southern slope of the Mayeama Mountain, from the peak to the foot, 2 km2 in area, and apparently about 0.5 km3 in volume, collapsed. Rocks and earth completely buried the ports of Shimabara and Antoku. The locality to the south of the main gates of the city of Shimabara were also covered with a layer from several tens of centimeters to 3 meters deep.

The collapse generated an enormous tsunami, more than 6-9 m in height in places, in Shimabara Bay. The height of the wave was estimated at 35-55 m at Shimabara. The length of coast, affected by the destruction of the tsunami, was 75 km. Homes and castles were washed out in the coastal cities, and fields were flooded at 17 villages. In all, 380 homes were washed away; 9,745 people were killed or disappeared without a trace, and 707 people were injured as a result of the tsunami and the collapse; 496 head of cattle died. Three small islands situated near the coast disappeared. At the same time, the mud and sand washed out to sea formed a score of new small islands in the region of Minato port.

The tsunami also caused great destruction on the other shore of Shimabara Bay, in Kumamoto Prefecture. There were more than 1,100 victims in Ashikita district, and 4,000 in the two adjacent districts of Uto and Tamana. There was also considerable destruction and 343 residents drowned on the Amakusa Is. The height of the wave on the Amakusa Is was estimated at 5-15 m.

Ref #2140:

A tsunami was caused by either an explosion at Mayu-yama (Unzen Volc Complex) or by a strong volcanic earthquake.

4,300 deaths from the tsunami.

Ref #1897:

1792, Feb. 10. Sea wave at Shimabara in Hizen, accompanying the eruption of Mt. Unsen; it is recorded that the high tide occurred seven or eight times a day. On this occasion portion of the mountain was split up and fell into the sea forming a number of small isles. Inundated area, however, was confined to the coast of the Sea of Tsukushi.

Ref #150:

1792, Feb. 10. 15,030 deaths. More than 6,200 houses destroyed. Eruption of Unzendake Volcano. Mt. Bizan (Zenzan) collapsed and slided debris generated large tsunami, about 10m in height. Shimabara Penin.

Ref#3766:

Total number of casualties of the event was recorded about 15000 persons, in which about 5000 persons were killed due to the tsunami on the eastern coast (Kumamoto Pref.) of the bay

Total death accounts vary:

Ref #1051, 12371, 3766, 2990: 15,000 deaths Ref #1068: 15,200 deaths Ref # 414: 15,188 deaths Ref #150: 15,030 deaths Ref #1182: 14,300 deaths