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1792 Unzen landslide and tsunami

Natural disaster in Japan

Field	Value
title	1792 Unzen landslide and tsunami
image	島原大変肥後迷惑.jpg
pre-1900	yes
local-date
map2	{{Location map	Kyushu#Japan
lat	32.8
long	130.3
mark	Bullseye1.png
marksize	50
position	top
width	260
float	center
relief	yes}}
magnitude	6.4
location
countries affected	Japan: Kyushu, Shimabara, Nagasaki
tsunami	Yes
casualties	15,000 deaths from landslide and megatsunami (estimate)

| pre-1900 = yes | local-date = The 1792 Unzen landslide and tsunami resulted from the volcanic activities of Mount Unzen (in the Shimabara Peninsula of Nagasaki Prefecture, Japan) on 21 May. This caused the collapse of the southern flank of the Mayuyama dome in front of Mount Unzen, resulting in a tremendous tsunami, killing 15,000 people altogether. It was also called Shimabara erupted, Higo affected, (Shimabara means the central mountain of the Shimabara Peninsula) since many people were killed by this tsunami in Higo (Kumamoto Prefecture, situated 20 km across the Ariake Sea).

Volcanic activities

Towards the end of 1791, a series of earthquakes occurred on the western flank of Mount Unzen which gradually moved towards Fugen-dake (one of Mount Unzen's peaks). In February 1792, Fugen-dake started to erupt, triggering a lava flow which continued for two months. Meanwhile, the earthquakes continued, shifting nearer to the city of Shimabara. On the night of 21 May, two large earthquakes were followed by a collapse of the eastern flank of Mount Unzen's Mayuyama dome, causing a landslide which swept through the city of Shimabara and into the Ariake Sea, triggering a great tsunami.

File:Unzen pyroclastic and lahar deposits.jpg|Mount Unzen (center) and Mayuyama (right) showing the destruction, recent photo File:Shimabara Mayuyama.jpg|Mayuyama of Shimabara Peninsula, from the sea of Shimabara City

Megatsunami

It is not known whether the collapse occurred as a result of an eruption of the dome or as a result of the earthquakes. The tsunami struck Higo Province on the other side of Ariake Bay before bouncing back and hitting Shimabara again. Out of an estimated total of 15,000 fatalities, around 5,000 are thought to have been killed by the landslide, around 5,000 by the tsunami across the bay in Higo Province, and a further 5,000 by the tsunami returning to strike Shimabara. The initial wave once reached a height of 330 ft, classing this tsunami as a megatsunami. At the Osaki-bana point Futsu town, the waves locally grew to a height of 187 ft due to the effect of sea bottom topography.

Monuments

As of July 1991, the following monuments have been found:

Kind of Monument	Kumamoto Prefecture	Nagasaki Prefecture
43	41	84
5	0	5
16	90	106
1	0	1
9	3	12
74	134	208

Lake Shirachi

Lake Shirachi is a pond in Shimabara city, Nagasaki Prefecture which was created after the landslide at Mayuyama created by the inpouring of underground water. Its size was first 1 km (south-north) and 300m 400m (east to west), but the production of a water exit river made it smaller and it is now 200 m by 70 m.

Tsukumojima (99 Islets)

As a result of the destruction, Tsukumojima or 99 islets or rocks were distributed near Shimabara city. In the same Nagasaki Prefecture, there are 99 islands or Kujūkushima distributed from Sasebo city to Hirado city. These islands are different from Tsukumojima.

References

National Geophysical Data Center. "Comments for the Significant Earthquake".
Johnston, Eric. (1 March 2011). "Latest volcano show: Shinmoe". [[The Japan Times]].
''200 Years after the Kansei Great Tsunami, Symposium and Exhibition of Unzen Disaster'' Booklet published by Newspaper Museum, Yoyasu Machi, Kumamoto-shi, 1991

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

natural-disasters-in-nagasaki-prefecture natural-disasters-in-kumamoto-prefecture tsunamis-in-japan 1792-in-japan 18th-century-tsunamis 1792-disasters 1790s-earthquakes megatsunamis earthquakes-of-the-edo-period volcanic-tsunamis volcano-tectonic-earthquakes landslides-in-japan 18th-century-disasters-in-japan 18th-century-volcanic-events sector-collapses

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