QuakeScout
Magnitude3.3

Reviewed by USGSJapan53y ago

M3.3 earthquake 177 km SSE of Katsuura, Japan

Sunday, August 26, 1973, 05:09:57 UTC · 33.639°N, 140.955°E

A magnitude 3.3 earthquake struck 177 km SSE of Katsuura, Japan on Sunday, August 26, 1973, 05:09:57 UTC, at a depth of 33.0 km (shallow).

Magnitude
3.3
Minor · mb
Depth
33 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

1 tons of TNT

That is about 1/11,203 of the Hiroshima bomb. A magnitude 5.0 releases about 355 times more energy.

Tectonic setting

7 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

33 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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.0 on September 24, 1973. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M3.3
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.0193 km SSE of Tateyama, Japan53y ago · 29 km SW of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 267 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.05 km SSE of Ōiso, JapanSeptember 1, 1923 · 234 km NW of this epicenter
  2. 7.9174 km SE of Katsuura, JapanNovember 25, 1953 · 74 km NE of this epicenter
  3. 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 177 km NW of this epicenter
  4. 7.450 km SSW of Ōyama, JapanJanuary 21, 1906 · 277 km W of this epicenter
  5. 7.3206 km SSE of Wada, JapanDecember 4, 1972 · 37 km S of this epicenter
  6. 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 191 km NE of this epicenter
  7. 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 260 km N of this epicenter
  8. 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 209 km W of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 29 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:

  1. 1923M7.9

    Tokyo, Yokohama

    1 Sep 1923 · 210 km away

    105,385 deaths$600 million damagetsunami

  2. 1855M7.0

    Tokyo

    11 Nov 1855 · 247 km away

    6,757 deathsExtreme damage ($25M+)tsunami

  3. 1703M8.2

    Off Sw Boso Peninsula

    30 Dec 1703 · 175 km away

    5,233 deathsExtreme damage ($25M+)tsunami

  4. 1707M8.4

    Enshunada

    28 Oct 1707 · 296 km away

    2,000 deathsSevere damage ($5–24M)tsunami

  5. 1854M8.3

    Enshunada Sea

    23 Dec 1854 · 285 km away

    1,000 deathsExtreme damage ($25M+)tsunami

  6. 1930M7.1

    Honshu: Idu

    25 Nov 1930 · 235 km away

    259 deathsExtreme damage ($25M+)

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

Nearby trackers

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