Reviewed by USGSJapan89y ago
M7.7 earthquake 69 km ESE of Kitaibaraki, Japan
Monday, May 23, 1938, 07:18:30 UTC · 36.534°N, 141.459°E
A magnitude 7.7 earthquake struck 69 km ESE of Kitaibaraki, Japan on Monday, May 23, 1938, 07:18:30 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.8 on September 2, 1923.
- Magnitude
- 7.7
- Major · mw
- Depth
- 15 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- 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
5.4 megatons of TNT
That is about 355 times the Hiroshima bomb. It released about 11,220 times the energy of a magnitude 5.0.
Tectonic setting
118 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
15 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 M5.6 on June 18, 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 142 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 · 236 km SW of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 221 km SW of this epicenter
- 7.6119 km SE of Kamaishi, JapanNovember 1, 1915 · 273 km NE of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 222 km SE of this epicenter
- 7.3110 km ESE of Ishinomaki, JapanJune 18, 1933 · 195 km NE of this epicenter
- 7.383 km E of Ishinomaki, JapanNovember 2, 1936 · 206 km N of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 67 km S of this epicenter
- 7.167 km ENE of Kashima-shi, JapanAugust 14, 1924 · 39 km S 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 119,268 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 238 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 179 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 215 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1828
Sandyo In Etigo
18 Dec 1828 · 204 km away
1,443 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 280 km away
259 deathsExtreme damage ($25M+)
- 1853
Odawara
11 Mar 1853 · 210 km away
79 deathsSevere damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.