Reviewed by USGSJapan53y ago
M4.0 earthquake 207 km SSE of Katsuura, Japan
Monday, July 30, 1973, 01:42:33 UTC · 33.409°N, 141.137°E
A magnitude 4.0 earthquake struck 207 km SSE of Katsuura, Japan on Monday, July 30, 1973, 01:42:33 UTC, at a depth of 38.0 km (shallow).
- Magnitude
- 4.0
- Light · mb
- Depth
- 38 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
15 tons of TNT
That is about 1/998 of the Hiroshima bomb. A magnitude 5.0 releases about 32 times more energy.
Tectonic setting
33 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
38 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.9 on August 9, 1973. 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 249 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 · 265 km NW of this epicenter
- 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 80 km NE of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 208 km NW of this epicenter
- 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 300 km W of this epicenter
- 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 28 km W of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 197 km NE of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 283 km N of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 235 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 24 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 117,755 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 · 278 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 205 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1930M7.1
Honshu: Idu
25 Nov 1930 · 264 km away
259 deathsExtreme damage ($25M+)
- 1853
Odawara
11 Mar 1853 · 277 km away
79 deathsSevere damage ($5–24M)
- 1894M7.5
Tokyo
20 Jun 1894 · 279 km away
24 deathsLimited damage (under $1M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.