July 31, 1640 Tsunami: SE. Hokkaido Island, Japan
A tsunami caused by a volcano and a landslide began at SE. Hokkaido Island, Japan on July 31, 1640. The water rose as high as 8 meters. Its effects were recorded at 3 places. It killed 700 people.
Where the waves reached
The source (white) and every runup with a place, colored by the water height recorded there. A ring is a runup NCEI marks doubtful.
- Under 1 m
- 1 to 3 m
- 3 to 10 m
- 10 to 30 m
- 30 m and more
- Height not recorded
Travel times
How long the first wave took to reach each part of the ocean, one line for each hour up to 24, estimated from the source and the depth of the sea.
The travel times are computed in your browser, which needs JavaScript.
- 1 to 4 hours
- 5 to 6 hours
- 7 to 14 hours
- 15 hours and more
Computed in your browser the way NOAA’s own travel time maps are: the wave travels at the square root of gravity times the depth, over NOAA’s ETOPO1 depths averaged to a 10 arc-minute grid. Checked against NOAA NCEI’s maps for 21 tsunamis over the first 24 hours, these lines fall within 10 minutes of NCEI’s at half the points compared and within 52 minutes at 9 in 10. They give when the first wave could arrive, not how high it is; bays, harbors and island chains finer than the grid can see it later. Not for use in a warning: see tsunami.gov.
The tsunami
- Date
- July 31, 1640
- Source
- SE. Hokkaido Island, Japan
- Cause
- Volcano and landslide
- Earthquake
- Magnitude 6.5
- Volcano
- The eruption that caused it
- Maximum water height
- 8 m (26.2 ft)
- Runups recorded
- 3
- Tsunami intensity (Soloviev-Imamura)
- 1
- Tsunami magnitude (Iida)
- 2
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 42.070° N, 140.680° E
The toll
- Deaths
- 700
- Damage
- Limited (under about $1 million)
- Houses destroyed
- 20
Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.
What the record says
NCEI’s account, from the sources it cites.
1640, July 31. There was a strong eruption of the Komagatake volcano on Hokkaido Island. The ejected ashes were carried by the wind right up to Niigata Village. The layer of ashes was 2 m deep at the foot of the volcano. A tsunami was observed; the waves reached the coast of Tsugaru Strait in the regions of Hidaka and Tokachi (Hokkaido Island). More than 100 ships gathering seaweed were washed away on the coast of Uchi'ura Bay; more than 700 people died. Twenty homes were washed away. It is assumed that the tsunami was due to the falling of the ejecta into the sea, or to an earthquake which was felt simultaneously with the eruption. Imamura surmises that the epicenter of the earthquake was situated to the east of the volcano, while Musya considers that it was situated at sea near Cape Shiriya (northern tip of Honshu Island). (reference #414)
1640, July 31, 42.1 N, 140.7 E, magnitude 6.5. Volcanic eruption of Mt. Komagatake. 700 persons drowned. About 100 vessels and many houses washed away. (reference #150)
1640, Japan. 700 persons drowned. (reference #132)
1640, July 31. Debris avalanche caused tsunami which killed 700; many ships also destroyed. (reference #9675)
1640 Komagatake, Hokkaido, Japan, Ocean entry by landslide from subaerial volcano lateral collapse. Maximum local runup > 8m. (reference #10446)
Every runup
Nearest the source first. Heights are above sea level at the time; a tide gauge reads half the wave’s full height.
| Where | Country | Km from source | Water height, m | Inland, m | Measured by | First wave, UTC | Deaths |
|---|---|---|---|---|---|---|---|
| Uchiura Bay | Japan | 7 | Eyewitness observation of water height | 700 | |||
| Hidaka | Japan | 171 | Eyewitness observation of water height | ||||
| Tokachi | Japan | 219 | Eyewitness observation of water height |
More
Every tsunami in 1640The 1600sTsunamis of JapanThe earthquakeThe eruptionThis day in weather historyAlerts in force
Sources
Tsunami events and runups from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-10-01. NCEI tsunami event 253.