Reviewed by USGSJapan58y ago
M6.1 earthquake 167 km E of Noda, Japan
Tuesday, September 24, 1968, 03:34:50 UTC · 40.352°N, 143.761°E
A magnitude 6.1 earthquake struck 167 km E of Noda, Japan on Tuesday, September 24, 1968, 03:34:50 UTC, at a depth of 22.5 km (shallow). It is the strongest earthquake within 300 km since an M6.8 on September 21, 1968.
- Magnitude
- 6.1
- Strong · mw
- Depth
- 23 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
19 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 39 times the energy of a magnitude 5.0.
Tectonic setting
51 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
23 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 lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M6.0 on October 20, 1968. 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 423 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.41933 Sanriku (Sanriku-oki) Earthquake, JapanMarch 2, 1933 · 146 km SE of this epicenter
- 8.21968 Tokachi-Oki EarthquakeMay 16, 1968 · 69 km NW of this epicenter
- 8.11952 Tokachi-Oki EarthquakeMarch 4, 1952 · 193 km N of this epicenter
- 8.0113 km ENE of Miyako, JapanMarch 20, 1960 · 70 km SW of this epicenter
- 7.978 km E of Hachinohe, JapanMarch 9, 1931 · 116 km W of this epicenter
- 7.970 km S of Honchō, JapanMay 16, 1968 · 148 km NW of this epicenter
- 7.7277 km SSE of Kushiro, JapanMay 3, 1919 · 161 km E of this epicenter
- 7.7217 km ESE of Kamaishi, JapanJuly 6, 1905 · 217 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 52 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 32,970 recorded deaths. The most severe:
- 1896M8.3
Sanriku
15 Jun 1896 · 97 km away
27,122 deathsExtreme damage ($25M+)tsunami
- 1933M8.4
Sanriku
2 Mar 1933 · 146 km away
3,022 deathsExtreme damage ($25M+)tsunami
- 1766M6.9
Hirosaki
8 Mar 1766 · 265 km away
1,700 deathsSevere damage ($5–24M)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 207 km away
745 deathsSevere damage ($5–24M)tsunami
- 1896
Senhoku, Ugo
31 Aug 1896 · 238 km away
206 deathsExtreme damage ($25M+)
- 1968M8.2
Off East Coast Of Honshu Island
16 May 1968 · 69 km away · intensity VI
52 deaths$131 million damagetsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.