QuakeScout
Magnitude6.8

Reviewed by USGSJapan59y ago

M6.8 earthquake 51 km ESE of Hyūga, Japan

Monday, April 1, 1968, 07:13:19 UTC · 32.272°N, 132.156°E

A magnitude 6.8 earthquake struck 51 km ESE of Hyūga, Japan on Monday, April 1, 1968, 07:13:19 UTC, at a depth of 33.1 km (shallow). It is the strongest earthquake within 300 km since an M7.5 on April 1, 1968.

Magnitude
6.8
Strong · mw
Depth
33 km
Shallow
Felt reports
0
Did You Feel It?
Est. shaking
VI
Strong (ShakeMap)
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

265 kilotons of TNT

That is about 18 times the Hiroshima bomb. It released about 556 times the energy of a magnitude 5.0.

Tectonic setting

70 km

from the nearest mapped plate boundary, between the Amur and Okinawa 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 100 km

USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 92 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.01941 Hyuganada EarthquakeNovember 18, 1941 · 26 km SW of this epicenter
  2. 7.958 km ESE of Takanabe, JapanNovember 2, 1931 · 44 km S of this epicenter
  3. 7.518 km NNE of Nichinan, JapanFebruary 26, 1961 · 87 km SW of this epicenter
  4. 7.518 km SE of Honmachi, JapanNovember 10, 1909 · 133 km W of this epicenter
  5. 7.560 km ESE of Nobeoka, JapanApril 1, 1968 · 26 km NE of this epicenter
  6. 7.422 km N of Nishinoomote, JapanJuly 13, 1923 · 183 km SW of this epicenter
  7. 7.229 km ESE of Takanabe, JapanApril 13, 1913 · 43 km SW of this epicenter
  8. 7.161 km ESE of Nishinoomote, JapanAugust 24, 1904 · 208 km S of this epicenter

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 24,965 recorded deaths. The most severe:

  1. 1792M6.4

    Kyusyu Island

    21 May 1792 · 184 km away

    15,030 deathsExtreme damage ($25M+)tsunami

  2. 1707M8.4

    Nankaido

    28 Oct 1707 · 268 km away

    5,000 deathsExtreme damage ($25M+)tsunami

  3. 1854M8.4

    Nankaido

    24 Dec 1854 · 282 km away

    3,000 deathsExtreme damage ($25M+)tsunami

  4. 1711M6.7

    Seionaikai, Japan

    20 Dec 1711 · 283 km away

    1,000 deathsSevere damage ($5–24M)tsunami

  5. 1872M7.4

    Honshu: Sw

    14 Mar 1872 · 293 km away

    804 deathsExtreme damage ($25M+)tsunami

  6. 1914M7.1

    Sakurijima

    12 Jan 1914 · 160 km away

    63 deaths$19 million damagetsunami

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

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