Reviewed by USGSJapan89y ago
M5.7 earthquake 86 km ESE of Iwaki, Japan
Monday, December 12, 1938, 23:38:43 UTC · 36.712°N, 141.754°E
A magnitude 5.7 earthquake struck 86 km ESE of Iwaki, Japan on Monday, December 12, 1938, 23:38:43 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M5.9 on December 9, 1938.
- Magnitude
- 5.7
- Moderate · 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: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
6 kilotons of TNT
That is about 1/3 of the Hiroshima bomb. It released about 12 times the energy of a magnitude 5.0.
Tectonic setting
107 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
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 75 km
USGS lists 1 M2.5+ earthquake within 75 km in the following 30 days; the largest was M5.8 on December 23, 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 193 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.05 km SSE of Ōiso, JapanSeptember 1, 1923 · 269 km SW of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 253 km SW of this epicenter
- 7.8105 km E of Iwaki, JapanNovember 5, 1938 · 40 km NE of this epicenter
- 7.7116 km E of Namie, JapanNovember 6, 1938 · 89 km NE of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 33 km SW of this epicenter
- 7.7116 km ESE of Namie, JapanNovember 5, 1938 · 65 km NE of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 282 km NE of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 243 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 46 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 120,480 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 271 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 211 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 247 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1828
Sandyo In Etigo
18 Dec 1828 · 218 km away
1,443 deathsExtreme damage ($25M+)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 280 km away
745 deathsSevere damage ($5–24M)tsunami
- 1894M7.0
Syonai
22 Oct 1894 · 298 km away
726 deathsSevere damage ($5–24M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.