Reviewed by USGSJapan83y ago
M6.1 earthquake 243 km SSE of Katsuura, Japan
Thursday, July 20, 1944, 20:07:17 UTC · 33.160°N, 141.433°E
A magnitude 6.1 earthquake struck 243 km SSE of Katsuura, Japan on Thursday, July 20, 1944, 20:07:17 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M6.9 on July 19, 1944.
- Magnitude
- 6.1
- Strong · 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
20 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 42 times the energy of a magnitude 5.0.
Tectonic setting
45 km
from the nearest mapped plate boundary, between the North American and African 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 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 108 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 246 km NW of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 204 km NE of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 273 km NW of this epicenter
- 7.1150 km ESE of Hasaki, JapanMarch 13, 1909 · 250 km N of this epicenter
- 7.0208 km SE of Katsuura, JapanApril 21, 1916 · 67 km NE of this epicenter
- 7.0125 km ESE of Katsuura, JapanAugust 18, 1927 · 155 km N of this epicenter
- 6.9off the east coast of Honshu, JapanJuly 19, 1944 · 73 km N of this epicenter
- 6.821 km SE of Shimoda, JapanSeptember 26, 1923 · 264 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 110,621 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 280 km away
105,385 deaths$600 million damagetsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 243 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1936
Nii Jima
27 Dec 1936 · 248 km away
3 deathsLimited damage (under $1M)
- 1782M7.3
Tokaido, Japan
22 Aug 1782 · 268 km away
Severe damage ($5–24M)tsunami
- 1909M7.5
Yokohama
13 Mar 1909 · 149 km away
Limited damage (under $1M)tsunami
- 1909M6.7
Choshi
12 Mar 1909 · 149 km away
Limited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.