QuakeIndex

Earthquake · reviewed by a seismologist

M 2.6ml

Earthquake near Unalaska, AK

No earthquake was likely felt in Unalaska in the 24 hours to 6:41 pm AKST (03:41 UTC). The last one was M 4.4, 117 km (72 mi) ESE, at 3:00 pm AKST on 11 November 2026, estimated intensity II (weak) in town. Every earthquake near Unalaska

This page: a magnitude 2.6 earthquake was recorded 15 km (9 mi) west-southwest of Unalaska, AK, at 7:17 am AKDT on 28 October 2021 (15:17 UTC), 13 km deep.

USGS: 15 km WSW of Unalaska, Alaska

7:17 am AKDT, Oct 28, 2021 · · 13 km deep · released about 240 lb of TNT

Every earthquake near Unalaska Felt it? Tell USGS Check my area
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Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
7:17 am AKDT on 28 October 2021 ()
Where
15 km (9 mi) west-southwest of Unalaska, AK · earthquakes near Unalaska
Magnitude
M 2.6 (ml)
Depth
13 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1770 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 20 km (12 mi) from the epicentre. In Unalaska, 15 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

Likely felt in: Unalaska 15 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 240 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 63,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 45,000× the energy of this one
  3. Around the size people start to feel M 3.0 4× the energy of this one
  4. This earthquake M 2.6 about 240 lb of TNT

Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

The largest earthquake within 50 km since 2016 was M 4.8 on 2020-03-30 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 36 km ESE of Unalaska, Alaska · 48 km ESE of this epicentre
  2. 6.0 51 km SW of Unalaska, Alaska · 38 km SW of this epicentre
  3. 5.9 27 km WNW of Dutch Harbor, Alaska · 19 km NNW of this epicentre
  4. 5.9 13 km NE of Dutch Harbor, Alaska · 28 km ENE of this epicentre
  5. 5.4 48 km WSW of Unalaska, Alaska · 34 km WSW of this epicentre

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 53.8418, -166.7557. Map © OpenStreetMap contributors.

Aftershocks so far

55 earthquakes have been recorded within 50 km since this one.

  1. 1.6 52 km SW of Unalaska, Alaska
  2. 1.5 37 km WNW of Dutch Harbor, Alaska
  3. 1.8 40 km SSW of Unalaska, Alaska
  4. 1.5 27 km WSW of Dutch Harbor, Alaska
  5. 1.8 17 km SW of Unalaska, Alaska
  6. 1.5 50 km SW of Unalaska, Alaska
  7. 2.0 Fox Islands, Aleutian Islands, Alaska
  8. 1.5 53 km SW of Unalaska, Alaska
  9. 3.3 57 km SSW of Unalaska, Alaska
  10. 3.4 57 km SSW of Unalaska, Alaska
  11. 1.6 29 km S of Unalaska, Alaska
  12. 1.5 51 km SW of Unalaska, Alaska
  13. 1.5 19 km W of Dutch Harbor, Alaska
  14. 1.5 52 km SW of Unalaska, Alaska
  15. 1.7 35 km SW of Unalaska, Alaska

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.