QuakeScout
Magnitude2.6

Reviewed by USGSAlaska5y ago

M2.6 earthquake 6 km NE of False Pass, Alaska

Thursday, February 18, 2021, 07:29:27 UTC · 54.897°N, 163.350°W

A magnitude 2.6 earthquake struck 6 km NE of False Pass, Alaska on Thursday, February 18, 2021, 07:29:27 UTC, at a depth of 116.5 km (intermediate).

Magnitude
2.6
Minor · ml
Depth
116 km
Intermediate
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

120 kg of TNT

That is about 1/125,702 of the Hiroshima bomb. A magnitude 5.0 releases about 3,981 times more energy.

Tectonic setting

179 km

from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: intermediate

116 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.7 on March 15, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M31h6h1d3d7d14d30dMainshock M2.6
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 2.741 km N of False Pass, Alaska5y ago · 37 km N of this epicenter
  2. 2.542 km SSW of False Pass, Alaska5y ago · 48 km SW of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 377 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.6The 1946 Unimak Island, Alaska EarthquakeApril 1, 1946 · 160 km S of this epicenter
  2. 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 241 km E of this epicenter
  3. 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 222 km E of this epicenter
  4. 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 144 km E of this epicenter
  5. 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 200 km SW of this epicenter
  6. 7.071 km SE of King Cove, AlaskaMay 30, 1991 · 118 km E of this epicenter
  7. 6.917 km S of Sand Point, AlaskaMay 13, 1993 · 187 km E of this epicenter
  8. 6.868 km SSW of Unalaska, AlaskaMarch 29, 1957 · 293 km SW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:

  1. 1946M8.6

    Unimak Island

    1 Apr 1946 · 160 km away · intensity VI

    168 deaths$26 million damagetsunami

  2. 1788M8.0

    Alaska Peninsula

    6 Aug 1788 · 150 km away

    tsunami

  3. 2020M7.6

    Alaska

    19 Oct 2020 · 241 km away · intensity IX

    tsunami

  4. 1948M7.5

    Alaska Peninsula

    14 May 1948 · 157 km away

  5. 1957M7.5

    Aleutian Islands: Fox Islands

    22 Mar 1957 · 119 km away · intensity V

  6. 1820

    East Aleutian Islands

    1 Mar 1820 · 93 km away

    tsunami

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

Nearby trackers

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