May 1, 1939 Tsunami: NW. Honshu Island, Japan
A tsunami caused by a magnitude 7 earthquake began at NW. Honshu Island, Japan on May 1, 1939 at 05:58 UTC. The water rose as high as 1.2 meters. Its effects were recorded at 25 places. It killed 27 people, counting the earthquake or eruption that caused it.
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
- May 1, 1939, 05:58 UTC
- Source
- NW. Honshu Island, Japan
- Cause
- Earthquake
- Earthquake
- Magnitude 7
- Maximum water height
- 1.2 m (3.9 ft)
- Runups recorded
- 25
- Tsunami intensity (Soloviev-Imamura)
- 0
- Tsunami magnitude (Iida)
- -1.7
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 40.100° N, 139.500° E
The toll
- Deaths
- 27 with the earthquake or eruption that caused it
- Injuries
- 52 with the earthquake or eruption that caused it
- Damage
- Moderate (about $1 to $5 million) with the earthquake or eruption that caused it
- Houses destroyed
- 479 with the earthquake or eruption that caused it
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.
Reference #414:
On May 1, 1939, at 14:58 [local time] there was a very strong earthquake on the Oga Peninsula (Akita Prefecture).
After the earthquake, a tsunami was observed on the coast of the Oga Peninsula. Besides the tide gauge at Tsuchizaki, the tsunami was registered at three other stations: Noshiro, Ajigasawa, and Sakata.
The source of the tsunami was sketched from these observations by the method of reverse fronts. A semicircle, fringing the Oga Peninsula about 2 km from the coast of the peninsula, was obtained.
One can assume, therefore, that the tsunami arose either as a result of the collapse of coastal rocks, or as a result of oscillations of the peninsula as a whole, or as a result of a change in the relief of the sea floor adjoining the peninsula.
According to fisherman from Aikawa, the tsunami appeared in the hour after the earthquake (he did not remember the exact time); when he landed the boat, he noticed that the water had turned white for a distance of 400-500 m, and that the level had fallen about 30 cm; then the boat seemed to rise above land. In 5-10 minutes, the sea returned to its previous state.
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 |
|---|---|---|---|---|---|---|---|
| Hataka | Japan | 20 | Eyewitness observation of water height | ||||
| Nishikurosawa | Japan | 24 | Eyewitness observation of water height | ||||
| Toga | Japan | 25 | Eyewitness observation of water height | ||||
| Hamashioya | Japan | 25 | Eyewitness observation of water height | ||||
| Yushiri | Japan | 26 | 0.9 | Eyewitness observation of water height | |||
| Kita'Ura | Japan | 28 | Eyewitness observation of water height | ||||
| Kamo | Japan | 30 | Eyewitness observation of water height | ||||
| Hamamaguchi | Japan | 31 | 13 | Eyewitness observation of water height | |||
| Hadachi | Japan | 38 | Eyewitness observation of water height | ||||
| Wakimoto | Japan | 41 | 30 | Eyewitness observation of water height | |||
| Noshiroko | Japan | 45 | 0.03 | Tide gauge (half the maximum wave height) | day 1, 06:30 | ||
| Tsubaki | Japan | 53 | 1.2 | Eyewitness observation of water height | |||
| Tsuchizakiko | Japan | 63 | 0.14 | Tide gauge (half the maximum wave height) | day 1, 06:16 | ||
| Kanagasaki | Japan | 85 | Eyewitness observation of water height | ||||
| Ajigasawa | Japan | 97 | 0.03 | Tide gauge (half the maximum wave height) | day 1, 06:30 | ||
| Onagawa | Japan | 122 | Eyewitness observation of water height | ||||
| Kohama | Japan | 131 | Eyewitness observation of water height | ||||
| Sakata | Japan | 134 | 0.05 | Tide gauge (half the maximum wave height) | day 1, 06:38 | ||
| Hamanaka | Japan | 144 | Eyewitness observation of water height | ||||
| Masukawa | Japan | 144 | Eyewitness observation of water height | ||||
| Minamihirasawa, Sado Island | Japan | 241 | Eyewitness observation of water height | ||||
| Shiodo | Japan | 618 | Eyewitness observation of water height | ||||
| Usawa | Japan | Eyewitness observation of water height | |||||
| Shiohama | Japan | Eyewitness observation of water height | |||||
| Cape Oppa | Japan | Eyewitness observation of water height |
More
Every tsunami in 1939The 1900sTsunamis of JapanThe earthquakeThis 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 1734.