August 21, 1951 Tsunami: Hawaii, United States
A tsunami caused by a magnitude 6.9 earthquake began at Hawaii, United States on August 21, 1951 at 10:57:00 UTC. The water rose as high as 3.6 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
The tsunami
- Date
- August 21, 1951, 10:57:00 UTC
- Source
- Hawaii, United States
- Cause
- Earthquake
- Earthquake
- Magnitude 6.9, 12 km deep
- Maximum water height
- 3.6 m (11.8 ft)
- Runups recorded
- 7
- Tsunami intensity (Soloviev-Imamura)
- 0.5
- Tsunami magnitude (Iida)
- 1.8
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 19.500° N, 156.000° W
The toll
- Damage
- Limited (under about $1 million)
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.
This was the strongest earthquake since 1868 on the Hawaiian Islands...At Napoopoo and Milolii, the sea level fell and then rose...A very slight tsunami was registered by tide gauges at Honolulu, Hilo, and at Port Allen (Reference #415).
After a magnitude 6.9 local earthquake, the sea level fell 1.2 m at Napoopoo and then rose 0.6 m above the normal level. At Milolii, the level fell 1.2 m and then rose 0.8 m above the normal position, washing away a canoe. Tide gage measurements registering 38 minutes later at Honolulu indicated a wave height of 0.03 m and a period of 14 minutes. Small oscillations were noted at Hilo and reported to have been recorded at Port Allen, Kauai with less than 0.1-m runup (Reference #236).
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 |
|---|---|---|---|---|---|---|---|
| Napoopoo, Hawaii, HI, HI | United States | 9 | 0.9 | Tide gauge (half the maximum wave height) | |||
| Kailua-Kona, Hawaii, HI, HI | United States | 14 | 0.9 | Tide gauge (half the maximum wave height) | |||
| Hookena, Hawaii, HI, HI | United States | 17 | 1.2 | Eyewitness observation of water height | |||
| Milolii, Hawaii, HI, HI | United States | 36 | 1 | Tide gauge (half the maximum wave height) | |||
| Hilo, Hawaii, HI, HI | United States | 102 | 0.1 | Tide gauge (half the maximum wave height) | day 21, 11:38 | ||
| Honolulu, Oahu, HI, HI | United States | 279 | 0.03 | Tide gauge (half the maximum wave height) | day 21, 11:35 | ||
| Port Allen, Kauai, HI, HI | United States | 459 | 0.1 | Tide gauge (half the maximum wave height) |
More
Every tsunami in 1951The 1900sTsunamis of United StatesThe 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 1815.