Reviewed by USGSJapan104y ago
M6.8 earthquake 21 km SE of Shimoda, Japan
Wednesday, September 26, 1923, 08:23:45 UTC · 34.533°N, 139.097°E
A magnitude 6.8 earthquake struck 21 km SE of Shimoda, Japan on Wednesday, September 26, 1923, 08:23:45 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M7.8 on September 2, 1923.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 10 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 earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
208 kilotons of TNT
That is about 14 times the Hiroshima bomb. It released about 437 times the energy of a magnitude 5.0.
Tectonic setting
47 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
10 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 100 km
USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 30 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 · 85 km N of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 91 km NE of this epicenter
- 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 106 km W of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 268 km NE of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 32 km SW of this epicenter
- 7.2176 km SE of Shingū, JapanFebruary 12, 1910 · 239 km SW of this epicenter
- 7.082 km ENE of Hasaki, JapanMarch 12, 1909 · 282 km NE of this epicenter
- 7.0208 km SE of Katsuura, JapanApril 21, 1916 · 262 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 30 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 141,683 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 73 km away
105,385 deaths$600 million damagetsunami
- 1847M7.4
Zenkoji, Nagano
8 May 1847 · 292 km away
12,000 deathsExtreme damage ($25M+)
- 1891M8.4
Mino-Owari
27 Oct 1891 · 219 km away
7,273 deathsExtreme damage ($25M+)
- 1855M7.0
Tokyo
11 Nov 1855 · 140 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 97 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1707M8.4
Enshunada
28 Oct 1707 · 128 km away
2,000 deathsSevere damage ($5–24M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.