Reviewed by USGSJapan58y ago
M5.6 earthquake 156 km E of Miyako, Japan
Thursday, September 12, 1968, 13:36:30 UTC · 39.745°N, 143.756°E
A magnitude 5.6 earthquake struck 156 km E of Miyako, Japan on Thursday, September 12, 1968, 13:36:30 UTC, at a depth of 21.3 km (shallow). It is the strongest earthquake within 300 km since an M5.7 on August 25, 1968.
- Magnitude
- 5.6
- Moderate · mw
- Depth
- 21 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
4 kilotons of TNT
That is about 1/4 of the Hiroshima bomb. It released about 9 times the energy of a magnitude 5.0.
Tectonic setting
40 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
21 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 2 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M6.1 on September 24, 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 416 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 · 93 km SE of this epicenter
- 8.21968 Tokachi-Oki EarthquakeMay 16, 1968 · 132 km N of this epicenter
- 8.11952 Tokachi-Oki EarthquakeMarch 4, 1952 · 260 km N of this epicenter
- 8.0113 km ENE of Miyako, JapanMarch 20, 1960 · 47 km W of this epicenter
- 7.978 km E of Hachinohe, JapanMarch 9, 1931 · 147 km NW of this epicenter
- 7.970 km S of Honchō, JapanMay 16, 1968 · 209 km N of this epicenter
- 7.7277 km SSE of Kushiro, JapanMay 3, 1919 · 188 km NE of this epicenter
- 7.7116 km E of Namie, JapanNovember 6, 1938 · 291 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 54 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 32,982 recorded deaths. The most severe:
- 1896M8.3
Sanriku
15 Jun 1896 · 34 km away
27,122 deathsExtreme damage ($25M+)tsunami
- 1933M8.4
Sanriku
2 Mar 1933 · 93 km away
3,022 deathsExtreme damage ($25M+)tsunami
- 1766M6.9
Hirosaki
8 Mar 1766 · 289 km away
1,700 deathsSevere damage ($5–24M)tsunami
- 1793M8.3
Sanriku,Rikuzen,Rikuchu
17 Feb 1793 · 140 km away
745 deathsSevere damage ($5–24M)tsunami
- 1896
Senhoku, Ugo
31 Aug 1896 · 237 km away
206 deathsExtreme damage ($25M+)
- 1905M7.0
Off Fukushima
6 Jul 1905 · 279 km away
57 deathstsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.