Reviewed by USGSJapan88y ago
M7.4 earthquake off the east coast of Honshu, Japan
Tuesday, October 10, 1939, 18:31:59 UTC · 38.513°N, 143.070°E
A magnitude 7.4 earthquake struck off the east coast of Honshu, Japan on Tuesday, October 10, 1939, 18:31:59 UTC, at a depth of 20.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on November 6, 1938.
- Magnitude
- 7.4
- Major · mw
- Depth
- 20 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquake
In context
How big was it, and why here?
Energy released
2.0 megatons of TNT
That is about 131 times the Hiroshima bomb. It released about 4,121 times the energy of a magnitude 5.0.
Tectonic setting
80 km
from the nearest mapped plate boundary, between the Pacific and Okhotsk plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
20 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 200 km
USGS has not published any M2.5+ earthquake within 200 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 231 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.41933 Sanriku (Sanriku-oki) Earthquake, JapanMarch 2, 1933 · 153 km NE of this epicenter
- 7.978 km E of Hachinohe, JapanMarch 9, 1931 · 238 km N of this epicenter
- 7.8105 km E of Iwaki, JapanNovember 5, 1938 · 193 km SW of this epicenter
- 7.7116 km E of Namie, JapanNovember 6, 1938 · 143 km SW of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 262 km SW of this epicenter
- 7.7116 km ESE of Namie, JapanNovember 5, 1938 · 168 km SW of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 92 km E of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 17 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 49 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 32,467 recorded deaths. The most severe:
- 1896M8.3
Sanriku
15 Jun 1896 · 136 km away
27,122 deathsExtreme damage ($25M+)tsunami
- 1933M8.4
Sanriku
2 Mar 1933 · 153 km away
3,022 deathsExtreme damage ($25M+)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 81 km away
745 deathsSevere damage ($5–24M)tsunami
- 1894M7.0
Syonai
22 Oct 1894 · 287 km away
726 deathsSevere damage ($5–24M)tsunami
- 1804M7.3
Kisakata
10 Jul 1804 · 277 km away
450 deathsExtreme damage ($25M+)tsunami
- 1896
Senhoku, Ugo
31 Aug 1896 · 243 km away
206 deathsExtreme damage ($25M+)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.