Reviewed by USGSJapan85y ago
M7.0 earthquake 122 km SSE of Koshima, Japan
Saturday, March 21, 1942, 23:20:46 UTC · 29.164°N, 130.834°E
A magnitude 7.0 earthquake struck 122 km SSE of Koshima, Japan on Saturday, March 21, 1942, 23:20:46 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on June 16, 1938.
- Magnitude
- 7.0
- Major · mw
- Depth
- 25 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 earthquake
In context
How big was it, and why here?
Energy released
511 kilotons of TNT
That is about 34 times the Hiroshima bomb. It released about 1,072 times the energy of a magnitude 5.0.
Tectonic setting
75 km
from the nearest mapped plate boundary, between the Okinawa and Philippine Sea plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
25 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 has not published any M2.5+ earthquake within 200 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 69 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.9108 km NW of Naze, JapanJune 15, 1911 · 197 km W of this epicenter
- 7.678 km S of Naze, JapanJune 16, 1938 · 214 km SW of this epicenter
- 7.4152 km ESE of Koshima, JapanFebruary 1, 1916 · 108 km E of this epicenter
- 7.422 km N of Nishinoomote, JapanJuly 13, 1923 · 197 km N of this epicenter
- 7.2Ryukyu Islands, JapanJune 24, 1901 · 153 km SW of this epicenter
- 7.2101 km NE of Naze, JapanNovember 5, 1923 · 57 km SW of this epicenter
- 7.161 km ESE of Nishinoomote, JapanAugust 24, 1904 · 161 km NE of this epicenter
- 7.0152 km NW of Uken, JapanJuly 4, 1914 · 270 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 75 recorded deaths. The most severe:
- 1914M7.1
Sakurijima
12 Jan 1914 · 269 km away
63 deaths$19 million damagetsunami
- 1911M8.0
Ryukyu Islands
15 Jun 1911 · 153 km away
12 deathsSevere damage ($5–24M)tsunami
- 1901M7.9
Ryukyu Islands
24 Jun 1901 · 254 km away
Limited damage (under $1M)tsunami
- 1916M8.0
Duda
1 Feb 1916 · 75 km away
- 1904M7.9
Kyushu
24 Aug 1904 · 123 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.