Reviewed by USGSJapan42y ago
M4.1 earthquake 184 km SE of Katsuura, Japan
Monday, September 24, 1984, 14:42:03 UTC · 33.990°N, 141.754°E
A magnitude 4.1 earthquake struck 184 km SE of Katsuura, Japan on Monday, September 24, 1984, 14:42:03 UTC, at a depth of 33.0 km (shallow).
- Magnitude
- 4.1
- Light · mb
- Depth
- 33 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
21 tons of TNT
That is about 1/707 of the Hiroshima bomb. A magnitude 5.0 releases about 22 times more energy.
Tectonic setting
11 km
from the nearest mapped plate boundary, between the Philippine Sea and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
33 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 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.7 on September 25, 1984. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.7175 km SE of Katsuura, Japan42y ago · 17 km W of this epicenter
- 4.4182 km SE of Katsuura, Japan42y ago · 9 km NE of this epicenter
- 4.4163 km SSE of Katsuura, Japan42y ago · 45 km W of this epicenter
- 5.7167 km SE of Katsuura, Japan42y ago · 31 km W of this epicenter
- 5.3163 km SE of Katsuura, Japan42y ago · 30 km W of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 532 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 · 263 km NW of this epicenter
- 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 12 km W of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 201 km NW of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 284 km N of this epicenter
- 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 112 km SW of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 111 km NE of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 218 km N of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 270 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 37 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 · 241 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 257 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 196 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 276 km away
259 deathsExtreme damage ($25M+)
- 1853
Odawara
11 Mar 1853 · 266 km away
79 deathsSevere damage ($5–24M)
- 1974M6.5
Nakagi
8 May 1974 · 286 km away · intensity IX
27 deathsModerate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.