Reviewed by USGSJapan89y ago
M6.5 earthquake 118 km ESE of Ōfunato, Japan
Wednesday, December 7, 1938, 13:04:19 UTC · 38.519°N, 142.889°E
A magnitude 6.5 earthquake struck 118 km ESE of Ōfunato, Japan on Wednesday, December 7, 1938, 13:04:19 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on November 30, 1938.
- Magnitude
- 6.5
- Strong · mw
- Depth
- 25 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 earthquakeDashed circle: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
85 kilotons of TNT
That is about 6 times the Hiroshima bomb. It released about 178 times the energy of a magnitude 5.0.
Tectonic setting
96 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
25 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 100 km
USGS lists 3 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M6.4 on December 13, 1938. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 220 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 · 166 km NE of this epicenter
- 7.978 km E of Hachinohe, JapanMarch 9, 1931 · 234 km N of this epicenter
- 7.8105 km E of Iwaki, JapanNovember 5, 1938 · 187 km SW of this epicenter
- 7.7116 km E of Namie, JapanNovember 6, 1938 · 136 km S of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 254 km SW of this epicenter
- 7.7116 km ESE of Namie, JapanNovember 5, 1938 · 163 km S of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 108 km E of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 19 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 51 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 32,526 recorded deaths. The most severe:
- 1896M8.3
Sanriku
15 Jun 1896 · 145 km away
27,122 deathsExtreme damage ($25M+)tsunami
- 1933M8.4
Sanriku
2 Mar 1933 · 166 km away
3,022 deathsExtreme damage ($25M+)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 97 km away
745 deathsSevere damage ($5–24M)tsunami
- 1894M7.0
Syonai
22 Oct 1894 · 271 km away
726 deathsSevere damage ($5–24M)tsunami
- 1804M7.3
Kisakata
10 Jul 1804 · 261 km away
450 deathsExtreme damage ($25M+)tsunami
- 1896
Senhoku, Ugo
31 Aug 1896 · 231 km away
206 deathsExtreme damage ($25M+)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.