May 23, 1938 Tsunami: Japan Trench
A tsunami caused by a magnitude 7.1 earthquake began at Japan Trench on May 23, 1938 at 07:18 UTC. The water rose as high as 0.83 meters. Its effects were recorded at 7 places.
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 23, 1938, 07:18 UTC
- Source
- Japan Trench
- Cause
- Earthquake
- Earthquake
- Magnitude 7.1
- Maximum water height
- 0.83 m (2.7 ft)
- Runups recorded
- 7
- Tsunami magnitude (Iida)
- -0.3
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 36.700° N, 141.400° E
The toll
The record gives no deaths, injuries or damage for this tsunami.
What the record says
NCEI’s account, from the sources it cites.
Reference #414:
1938, May 23, 16:18 local time. There was a rather strong earthquake with source off Shioyasaki, which caused light destruction in Fukushima Prefecture. It was accompanied by a series of aftershocks and tsunami waves, which were registered on the coast of Hokkaido Island, the Sanriku area, and Fukushima and Chiba Prefectures.
The predominant period of oscillations was about 20 minutes at each station.
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 |
|---|---|---|---|---|---|---|---|
| Onahama | Japan | 52 | 0.42 | Tide gauge (half the maximum wave height) | day 23, 07:42 | ||
| Choshi | Japan | 116 | 0.09 | Tide gauge (half the maximum wave height) | |||
| Hanabuchi | Japan | 177 | 0.23 | Tide gauge (half the maximum wave height) | |||
| Ishinomaki | Japan | 191 | 0.05 | Tide gauge (half the maximum wave height) | |||
| Onagawa | Japan | 192 | 0.16 | Tide gauge (half the maximum wave height) | |||
| Tsukihama | Japan | 207 | 0.07 | Tide gauge (half the maximum wave height) | day 23, 07:59 | ||
| Hachinohe | Japan | 426 | 0.11 | Tide gauge (half the maximum wave height) | day 23, 09:42 |
More
Every tsunami in 1938The 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 2026-09-24. NCEI tsunami event 1711.