August 6, 1788 Earthquake: Alaska Peninsula, United States
A magnitude 8 earthquake struck Alaska Peninsula, United States on August 6, 1788. It caused a tsunami.
Map
Where it struck, with the other significant earthquakes within 200 km. Circles are sized and colored by magnitude; select one for its page.
The earthquake
- Date
- August 6, 1788
- Place
- Alaska Peninsula, United States
- Magnitude
- 8 (Ms)
- Tsunami
- Yes: the tsunami it caused
- Epicenter
- 55.000° N, 161.000° W
- Country
- United States
The toll
- Deaths
- Many (about 101 to 1,000) with its tsunami and other effects
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.
1788, August 7. 55.0 N, 161.0 W. Unga Island, Alaska. A strong
earthquake may have ruptured the plate boundary "from Unga to Sanak on Aug. 7. There was such a terrible flood on Unga Island that many Aleuts were killed, and the water rose to 50 sazhens (about 91 m)." The tsunami was much smaller at Pavlof Bay (on the south coast of the Alaska Peninsula) and did not affect the north side of Unimak Island. There is some doubt that this is a second earthquake in 1788. (reference #542)
Other significant earthquakes nearby
Within 200 km, the deadliest first.
More
Significant earthquakes of 1788The 1700sRecent earthquakes near hereThis day in weather history
Sources
Significant earthquakes 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 earthquake 5927.