Reviewed by USGSJapan42y ago
M4.8 earthquake 86 km SSE of Katsuura, Japan
Saturday, September 29, 1984, 10:26:58 UTC · 34.400°N, 140.571°E
A magnitude 4.8 earthquake struck 86 km SSE of Katsuura, Japan on Saturday, September 29, 1984, 10:26:58 UTC, at a depth of 69.2 km (shallow). It is the strongest earthquake within 300 km since an M5.7 on September 25, 1984.
- Magnitude
- 4.8
- Light · mb
- Depth
- 69 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
239 tons of TNT
That is about 1/63 of the Hiroshima bomb. A magnitude 5.0 releases about 2 times more energy.
Tectonic setting
21 km
from the nearest mapped plate boundary, between the Okhotsk and Philippine Sea plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
69 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 557 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 · 148 km NW of this epicenter
- 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 106 km SE of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 88 km NW of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 251 km N of this epicenter
- 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 235 km W of this epicenter
- 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 124 km S of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 184 km E of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 191 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 48 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 120,838 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 125 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 156 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 85 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1707M8.4
Enshunada
28 Oct 1707 · 257 km away
2,000 deathsSevere damage ($5–24M)tsunami
- 1854M8.3
Enshunada Sea
23 Dec 1854 · 250 km away
1,000 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 158 km away
259 deathsExtreme damage ($25M+)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.