Reviewed by USGSJapan104y ago
M8.0 earthquake 5 km SSE of Ōiso, Japan
Saturday, September 1, 1923, 02:58:35 UTC · 35.274°N, 139.344°E
A magnitude 8.0 earthquake struck 5 km SSE of Ōiso, Japan on Saturday, September 1, 1923, 02:58:35 UTC, at a depth of 15.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 8.0
- Major · mw
- Depth
- 15 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- IX
- Violent (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
13 megatons of TNT
That is about 872 times the Hiroshima bomb. It released about 27,542 times the energy of a magnitude 5.0.
Tectonic setting
31 km
from the nearest mapped plate boundary, between the Okhotsk and Philippine Sea plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
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 6 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M7.8 on September 2, 1923. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 6.821 km SE of Shimoda, Japan104y ago · 85 km S of this epicenter
- 5.97 km W of Miura, Japan104y ago · 22 km SE of this epicenter
- 6.112 km SSE of Odawara, Japan104y ago · 19 km SW of this epicenter
- 6.79 km SSE of Mobara, Japan104y ago · 92 km E of this epicenter
- 7.85 km E of Tateyama, Japan104y ago · 62 km SE of this epicenter
- 6.78 km S of Ninomiya, Japan104y ago · 10 km SW of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 29 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 172 km SW of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 297 km E of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 208 km E of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 113 km SW of this epicenter
- 7.1150 km ESE of Hasaki, JapanMarch 13, 1909 · 276 km E of this epicenter
- 7.082 km ENE of Hasaki, JapanMarch 12, 1909 · 226 km E of this epicenter
- 7.0208 km SE of Katsuura, JapanApril 21, 1916 · 282 km SE of this epicenter
- 7.0139 km S of Ōyama, JapanOctober 8, 1915 · 245 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 143,613 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 24 km away
105,385 deaths$600 million damagetsunami
- 1847M7.4
Zenkoji, Nagano
8 May 1847 · 227 km away
12,000 deathsExtreme damage ($25M+)
- 1891M8.4
Mino-Owari
27 Oct 1891 · 214 km away
7,273 deathsExtreme damage ($25M+)
- 1855M7.0
Tokyo
11 Nov 1855 · 59 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 67 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1751M6.6
Honshu: Nw
20 May 1751 · 241 km away
2,100 deathsExtreme damage ($25M+)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.