QuakeScout
Magnitude6.6

Reviewed by USGSJapan107y ago

M6.6 earthquake 92 km WSW of Kamiiso, Japan

Thursday, March 3, 1921, 03:02:26 UTC · 41.495°N, 139.624°E

A magnitude 6.6 earthquake struck 92 km WSW of Kamiiso, Japan on Thursday, March 3, 1921, 03:02:26 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on March 14, 1914.

Magnitude
6.6
Strong · mw
Depth
15 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 earthquake

In context

How big was it, and why here?

Energy released

124 kilotons of TNT

That is about 8 times the Hiroshima bomb. It released about 260 times the energy of a magnitude 5.0.

Tectonic setting

80 km

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

Depth: shallow

15 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 10 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.5Near the east coast of Honshu, JapanAugust 9, 1901 · 245 km SE of this epicenter
  2. 7.2Near the east coast of Honshu, JapanAugust 9, 1901 · 265 km SE of this epicenter
  3. 7.013 km ESE of Yokote, JapanMarch 14, 1914 · 262 km S of this epicenter
  4. 6.830 km ESE of Tomakomai, JapanFebruary 20, 1913 · 223 km NE of this epicenter
  5. 6.624 km S of Shizunai-furukawachō, JapanSeptember 16, 1909 · 237 km E of this epicenter
  6. 6.484 km NW of Noshiro, JapanOctober 11, 1919 · 94 km S of this epicenter
  7. 6.225 km WSW of Muroran, JapanJune 8, 1912 · 120 km NE of this epicenter
  8. 6.084 km W of Noshiro, JapanAugust 5, 1907 · 139 km S of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 19 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 3,408 recorded deaths. The most severe:

  1. 1766M6.9

    Hirosaki

    8 Mar 1766 · 112 km away

    1,700 deathsSevere damage ($5–24M)tsunami

  2. 1894M7.0

    Syonai

    22 Oct 1894 · 289 km away

    726 deathsSevere damage ($5–24M)tsunami

  3. 1804M7.3

    Kisakata

    10 Jul 1804 · 273 km away

    450 deathsExtreme damage ($25M+)tsunami

  4. 1896

    Senhoku, Ugo

    31 Aug 1896 · 203 km away

    206 deathsExtreme damage ($25M+)

  5. 1914M7.2

    Senhoku

    15 Mar 1914 · 256 km away

    94 deathsSevere damage ($5–24M)

  6. 1833M7.4

    Honshu: Nw

    7 Dec 1833 · 291 km away

    85 deathsSevere damage ($5–24M)tsunami

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

Nearby trackers

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