M8.2 earthquake 1969 Hokkaido Toho-oki Earthquake

Monday, August 11, 1969, 21:27:36 UTC · 43.465°N, 147.787°E

A magnitude 8.2 earthquake struck 1969 Hokkaido Toho-oki Earthquake on Monday, August 11, 1969, 21:27:36 UTC, at a depth of 28.6 km (shallow). It is the strongest earthquake within 300 km since an M8.5 on October 13, 1963.

Magnitude: 8.2; Great · mw
Depth: 29 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VI; Strong (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 400 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

30 megatons of TNT

That is about 1,998 times the Hiroshima bomb. It released about 63,096 times the energy of a magnitude 5.0.

Tectonic setting

49 km

from the nearest mapped plate boundary, between the Okhotsk and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

29 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 400 km

USGS lists 55 M2.5+ earthquakes within 400 km in the following 30 days; the largest was M7.1 on August 14, 1969. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 318 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 28 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 47 recorded deaths. The most severe:

1843M8.4
Hokkaido: Yezo, Kushiro, Nemuro
25 Apr 1843 · 219 km away
45 deathsModerate damage ($1–5M)tsunami
1894M7.9
Off Coast Of Honshu
22 Mar 1894 · 181 km away · intensity IX
1 deathModerate damage ($1–5M)tsunami
1938M6.1
E. Hokkaido Island, Japan
28 May 1938 · 281 km away
1 deathLimited damage (under $1M)tsunami
1958M8.3
Kuril Islands
6 Nov 1958 · 133 km away · intensity X
Moderate damage ($1–5M)tsunami
1969M8.2
Shikotan Island, Kurilskiye
11 Aug 1969 · 18 km away · intensity IX
Moderate damage ($1–5M)tsunami
1963M8.5
Kuril Islands
13 Oct 1963 · 216 km away · intensity IX
Limited damage (under $1M)tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers