Reviewed by USGSJapan42y ago
M4.4 earthquake 163 km SSE of Katsuura, Japan
Wednesday, September 26, 1984, 10:39:52 UTC · 33.906°N, 141.279°E
A magnitude 4.4 earthquake struck 163 km SSE of Katsuura, Japan on Wednesday, September 26, 1984, 10:39:52 UTC, at a depth of 53.9 km (shallow).
- Magnitude
- 4.4
- Light · mb
- Depth
- 54 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: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
60 tons of TNT
That is about 1/251 of the Hiroshima bomb. A magnitude 5.0 releases about 8 times more energy.
Tectonic setting
22 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
54 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 50 km
USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.7 on October 4, 1984. 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 552 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 · 233 km NW of this epicenter
- 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 34 km E of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 172 km NW of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 293 km N of this epicenter
- 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 77 km SW of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 149 km NE of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 227 km N of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 229 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 40 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 117,812 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 210 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 236 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 169 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 242 km away
259 deathsExtreme damage ($25M+)
- 1853
Odawara
11 Mar 1853 · 241 km away
79 deathsSevere damage ($5–24M)
- 1974M6.5
Nakagi
8 May 1974 · 246 km away · intensity IX
27 deathsModerate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.