M4.5 earthquake 82 km ESE of Nemuro, Japan

Thursday, July 5, 1973, 12:21:00 UTC · 43.066°N, 146.525°E

A magnitude 4.5 earthquake struck 82 km ESE of Nemuro, Japan on Thursday, July 5, 1973, 12:21:00 UTC, at a depth of 39.0 km (shallow). It is the strongest earthquake within 300 km since an M5.5 on July 5, 1973.

Magnitude: 4.5; Light · mb
Depth: 39 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

85 tons of TNT

That is about 1/178 of the Hiroshima bomb. A magnitude 5.0 releases about 6 times more energy.

Tectonic setting

72 km

from the nearest mapped plate boundary, between the Okhotsk and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

39 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 9 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.4 on July 29, 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 446 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 32 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 107 recorded deaths. The most severe:

1843M8.4
Hokkaido: Yezo, Kushiro, Nemuro
25 Apr 1843 · 126 km away
45 deathsModerate damage ($1–5M)tsunami
1952M8.1
Hokkaido
4 Mar 1952 · 241 km away · intensity IX
33 deathsSevere damage ($5–24M)tsunami
1973M7.7
Hokkaido Island
17 Jun 1973 · 61 km away · intensity VIII
27 deaths$5 million damagetsunami
1894M7.9
Off Coast Of Honshu
22 Mar 1894 · 76 km away · intensity IX
1 deathModerate damage ($1–5M)tsunami
1938M6.1
E. Hokkaido Island, Japan
28 May 1938 · 189 km away
1 deathLimited damage (under $1M)tsunami
1958M8.3
Kuril Islands
6 Nov 1958 · 229 km away · intensity X
Moderate damage ($1–5M)tsunami

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

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