March 20, 1939 Tsunami: Seikaido, Japan
A tsunami caused by a magnitude 6.6 earthquake began at Seikaido, Japan on March 20, 1939 at 03:22 UTC. The water rose as high as 0.8 meters. Its effects were recorded at 4 places. It killed 1 person, 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
The tsunami
- Date
- March 20, 1939, 03:22 UTC
- Source
- Seikaido, Japan
- Cause
- Earthquake
- Earthquake
- Magnitude 6.6, 20 km deep
- Maximum water height
- 0.8 m (2.6 ft)
- Runups recorded
- 4
- Tsunami intensity (Soloviev-Imamura)
- 0
- Tsunami magnitude (Iida)
- -0.3
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 32.300° N, 132.000° E
The toll
- Deaths
- 1 with the earthquake or eruption that caused it
- Damage
- Limited (under about $1 million) with the earthquake or eruption that caused it
- Houses destroyed
- 1 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:
1939, March 20, at 12:22 [local time], validity 2, there was an earthquake with source off the coast of Miyazaki Prefecture. It caused a weak tsunami. A wave 80 cm high was observed at Muroto, 12 cm at Tosashimizu, 16 cm at Aburatsu. The assumed travel time of the tsunami to Tosashimizu and Aburatsu was 30 minutes. The energy of the tsunami, according to Hatori's estimates, was 7 X 1018 ergs.
Reference #150:
1939, March 20, 32.3 132 E, magnitude 6.6. Hosojima 7cm, Aburatsu 16cm, Muroto 8Ocm, Tosa-Shimizu 12cm (peak-to-trough). 1 death, 1 house destroyed.
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 |
|---|---|---|---|---|---|---|---|
| Hososhima | Japan | 35 | 0.04 | Tide gauge (half the maximum wave height) | |||
| Aburatsu | Japan | 97 | 0.08 | Tide gauge (half the maximum wave height) | |||
| Tosa-Shimizu | Japan | 105 | 0.06 | Tide gauge (half the maximum wave height) | |||
| Murotomisaki | Japan | 230 | 0.4 | Tide gauge (half the maximum wave 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 2026-09-24. NCEI tsunami event 1731.