QuakeScout
Magnitude4.4

Reviewed by USGSAlaska40y ago

M4.4 earthquake 75 km SE of Akhiok, Alaska

Monday, July 7, 1986, 11:29:58 UTC · 56.416°N, 153.402°W

A magnitude 4.4 earthquake struck 75 km SE of Akhiok, Alaska on Monday, July 7, 1986, 11:29:58 UTC, at a depth of 33.0 km (shallow).

Magnitude
4.4
Light · 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

60 tons of TNT

That is about 1/251 of the Hiroshima bomb. A magnitude 5.0 releases about 8 times more energy.

Tectonic setting

77 km

from the nearest mapped plate boundary, between the North American and Pacific 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.0 on July 21, 1986. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M51h6h1d3d7d14d30dMainshock M4.4
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 3.681 km S of Old Harbor, Alaska40y ago · 22 km E of this epicenter
  2. 5.063 km SE of Akhiok, Alaska40y ago · 20 km N of this epicenter
  3. 3.3120 km SSE of Old Harbor, Alaska40y ago · 49 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 255 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.9Kodiak Island region, AlaskaOctober 9, 1900 · 182 km NE of this epicenter
  2. 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 144 km NW of this epicenter
  3. 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 218 km W of this epicenter
  4. 6.9105 km ESE of Perryville, AlaskaNovember 17, 1938 · 292 km W of this epicenter
  5. 6.9143 km ESE of Chignik, AlaskaFebruary 13, 1951 · 191 km W of this epicenter
  6. 6.9171 km SW of Akhiok, AlaskaFebruary 6, 1964 · 170 km SW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1900M8.3

    Kodiak Island

    9 Oct 1900 · 75 km away · intensity VIII

    Limited damage (under $1M)

  2. 1788M8.0

    Unga Island

    21 Jul 1788 · 69 km away · intensity VII

    Limited damage (under $1M)tsunami

  3. 1970M6.0

    Andreanof Islands

    11 Mar 1970 · 124 km away · intensity V

    Limited damage (under $1M)tsunami

  4. 1792

    Kodiak Island

    1792 · 107 km away · intensity VII

    Limited damage (under $1M)tsunami

  5. 1906M7.6

    Aleutian Islands

    23 Dec 1906 · 57 km away

  6. 1912M7.5

    Alaska Peninsula

    7 Nov 1912 · 155 km away · intensity V

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

Nearby trackers

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