M4.2 earthquake in Izu Islands, Japan region

Thursday, January 25, 1973, 11:31:41 UTC · 33.321°N, 140.669°E

A magnitude 4.2 earthquake struck in Izu Islands, Japan region on Thursday, January 25, 1973, 11:31:41 UTC, at a depth of 76.0 km (intermediate).

Magnitude: 4.2; Light · mb
Depth: 76 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 earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

30 tons of TNT

That is about 1/500 of the Hiroshima bomb. A magnitude 5.0 releases about 16 times more energy.

Tectonic setting

42 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: intermediate

76 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 lists 7 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.3 on February 10, 1973. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 242 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 26 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 120,755 recorded deaths. The most severe:

1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 225 km away
105,385 deaths$600 million damagetsunami
1855M7.0
Tokyo
11 Nov 1855 · 271 km away
6,757 deathsExtreme damage ($25M+)tsunami
1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 197 km away
5,233 deathsExtreme damage ($25M+)tsunami
1707M8.4
Enshunada
28 Oct 1707 · 279 km away
2,000 deathsSevere damage ($5–24M)tsunami
1854M8.3
Enshunada Sea
23 Dec 1854 · 267 km away
1,000 deathsExtreme damage ($25M+)tsunami
1930M7.1
Honshu: Idu
25 Nov 1930 · 242 km away
259 deathsExtreme damage ($25M+)

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers