Reviewed by USGSJapan42y ago
M4.7 earthquake 117 km SE of Katsuura, Japan
Friday, October 5, 1984, 13:37:23 UTC · 34.346°N, 141.160°E
A magnitude 4.7 earthquake struck 117 km SE of Katsuura, Japan on Friday, October 5, 1984, 13:37:23 UTC, at a depth of 87.0 km (intermediate). It is the strongest earthquake within 300 km since an M4.7 on October 4, 1984.
- Magnitude
- 4.7
- Light · mb
- Depth
- 87 km
- Intermediate
- 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
169 tons of TNT
That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.
Tectonic setting
8 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: intermediate
87 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 580 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 · 195 km NW of this epicenter
- 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 57 km SE of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 133 km NW of this epicenter
- 7.769 km ESE of Kitaibaraki, JapanMay 23, 1938 · 245 km N of this epicenter
- 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 289 km W of this epicenter
- 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 118 km S of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 134 km E of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 179 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 47 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 117,838 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 173 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 191 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 129 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 210 km away
259 deathsExtreme damage ($25M+)
- 1853
Odawara
11 Mar 1853 · 198 km away
79 deathsSevere damage ($5–24M)
- 1974M6.5
Nakagi
8 May 1974 · 226 km away · intensity IX
27 deathsModerate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.