Reviewed by USGSJapan96y ago
M7.9 earthquake 78 km E of Hachinohe, Japan
Monday, March 9, 1931, 03:49:00 UTC · 40.591°N, 142.422°E
A magnitude 7.9 earthquake struck 78 km E of Hachinohe, Japan on Monday, March 9, 1931, 03:49:00 UTC, at a depth of 35.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 7.9
- Major · mw
- Depth
- 35 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VII
- Very strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
11 megatons of TNT
That is about 760 times the Hiroshima bomb. It released about 23,988 times the energy of a magnitude 5.0.
Tectonic setting
167 km
from the nearest mapped plate boundary, between the Pacific and Okhotsk plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
35 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 lists 3 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.9 on March 15, 1931. 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 85 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.7277 km SSE of Kushiro, JapanMay 3, 1919 · 270 km E of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 282 km SE of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 220 km S of this epicenter
- 7.5Near the east coast of Honshu, JapanAugust 9, 1901 · 10 km W of this epicenter
- 7.379 km ENE of Miyako, JapanMay 27, 1928 · 87 km SE of this epicenter
- 7.2Near the east coast of Honshu, JapanAugust 9, 1901 · 12 km SE of this epicenter
- 7.1123 km SE of Honchō, JapanJuly 29, 1917 · 131 km NE of this epicenter
- 7.013 km ESE of Yokote, JapanMarch 14, 1914 · 207 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 34 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 31,216 recorded deaths. The most severe:
- 1896M8.3
Sanriku
15 Jun 1896 · 181 km away
27,122 deathsExtreme damage ($25M+)tsunami
- 1766M6.9
Hirosaki
8 Mar 1766 · 149 km away
1,700 deathsSevere damage ($5–24M)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 269 km away
745 deathsSevere damage ($5–24M)tsunami
- 1894M7.0
Syonai
22 Oct 1894 · 293 km away
726 deathsSevere damage ($5–24M)tsunami
- 1804M7.3
Kisakata
10 Jul 1804 · 272 km away
450 deathsExtreme damage ($25M+)tsunami
- 1896
Senhoku, Ugo
31 Aug 1896 · 137 km away
206 deathsExtreme damage ($25M+)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.