August 818 Earthquake: Tokkaido, Japan
A magnitude 7.9 earthquake struck Tokkaido, Japan in August 818. 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 818
- Place
- Tokkaido, Japan
- Magnitude
- 7.9 (Ms)
- Tsunami
- Yes: the tsunami it caused
- Epicenter
- 35.200° N, 139.300° E
- Country
- Japan
The toll
- Deaths
- Many (about 101 to 1,000)
- Damage
- Moderate (about $1 to $5 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.
818, August. Kanto, Sagami Bay, 35.2 N, 139.3 E, magnitude 7.9. Boso Peninsula was struck by a moderate tsunami. South Kanto landslide. Many deaths. (reference #150)
August 818. There was strong earthquake in the prefectures of Tokyo, Saitama, Ibaraki, Gumma, and Tochigi; and there was a tsunami in Sagami Gulf. [35.2 N, 139.3 E; M=7.9, m=1]. (reference #414)
818, August. Tokaido, Sagami bay, 35.2 N, 139.3 E, magnitude 7.9 MS. Imamura considers this a distant tsunami, Kawasumi considers it associated with a probable Sanriku quake. Considering the season it seems just as likely to have been a storm surge. (reference #79)
Other significant earthquakes nearby
Within 200 km, the deadliest first.
- September 1, 1923, Tokyo, Yokohama, Japan
- May 27, 1293, Kamakura, Japan
- November 11, 1855, Tokyo, Japan
- December 30, 1703, Off SW Boso Peninsula, Japan
- September 20, 1498, Enshunada Sea, Japan
- January 12, 1945, S, Honshu, Japan
- October 28, 1707, Enshunada, Japan
- December 23, 1854, Enshunada Sea, Japan
- November 25, 1930, Idu, Honshu, Japan
- April 9, 1858, N, Hida, Japan
- September 12, 1495, Kamakura, Japan
- July 29, 1649, Tokyo, Japan
- March 1, 1633, Odawara, Japan
- March 11, 1853, Odawara, Japan
- April 28, 1714, Oomati, Japan
More
Significant earthquakes of 818The 800sRecent earthquakes near here
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 5898.