Reviewed by USGSJapan89y ago
M5.9 earthquake 142 km ESE of Iwaki, Japan
Friday, December 9, 1938, 09:35:20 UTC · 36.679°N, 142.411°E
A magnitude 5.9 earthquake struck 142 km ESE of Iwaki, Japan on Friday, December 9, 1938, 09:35:20 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M6.5 on December 7, 1938.
- Magnitude
- 5.9
- 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
9 kilotons of TNT
That is about 1/2 of the Hiroshima bomb. It released about 19 times the energy of a magnitude 5.0.
Tectonic setting
62 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 75 km
USGS lists 1 M2.5+ earthquake within 75 km in the following 30 days; the largest was M5.7 on December 12, 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 191 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 293 km SW of this epicenter
- 7.8105 km E of Iwaki, JapanNovember 5, 1938 · 45 km NW of this epicenter
- 7.7116 km E of Namie, JapanNovember 6, 1938 · 79 km N of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 86 km W of this epicenter
- 7.7116 km ESE of Namie, JapanNovember 5, 1938 · 54 km N of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 245 km NE of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 226 km N of this epicenter
- 7.6141 km ESE of Namie, JapanNovember 6, 1938 · 37 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 43 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 14,369 recorded deaths. The most severe:
- 1855M7.0
Tokyo
11 Nov 1855 · 261 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 286 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1828
Sandyo In Etigo
18 Dec 1828 · 274 km away
1,443 deathsExtreme damage ($25M+)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 246 km away
745 deathsSevere damage ($5–24M)tsunami
- 1853
Odawara
11 Mar 1853 · 293 km away
79 deathsSevere damage ($5–24M)
- 1905M7.0
Off Fukushima
6 Jul 1905 · 82 km away
57 deathstsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.