QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5ml

Earthquake near Unalaska, AK

No earthquake was likely felt in Unalaska in the 24 hours to 7:32 pm AKST (04:32 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 2.5 earthquake was recorded 5 km (3 mi) southwest of Unalaska, AK, at 3:24 pm AKDT on 26 March 2023 (23:24 UTC), 9.3 km deep.

USGS: 4 km SW of Unalaska, Alaska

3:24 pm AKDT, Mar 26, 2023 · · 9.3 km deep · released about 170 lb of TNT

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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
3:24 pm AKDT on 26 March 2023 ()
Where
5 km (3 mi) southwest of Unalaska, AK · earthquakes near Unalaska
Magnitude
M 2.5 (ml)
Depth
9.3 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1030 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 21 km (13 mi) from the epicentre. In Unalaska, 5 km away, the estimate is intensity III (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 5 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.6× the energy of this one
  4. This earthquake M 2.5 about 170 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 2,800 times the energy of this one.

Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 36 km ESE of Unalaska, Alaska · 37 km ESE of this epicentre
  2. 6.0 51 km SW of Unalaska, Alaska · 47 km SW of this epicentre
  3. 5.9 27 km WNW of Dutch Harbor, Alaska · 28 km NW of this epicentre
  4. 5.9 13 km NE of Dutch Harbor, Alaska · 19 km NE of this epicentre
  5. 5.4 48 km WSW of Unalaska, Alaska · 45 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 53.8393, -166.5763. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.1 53 km S of Unalaska, Alaska
  2. 1.7 50 km SW of Unalaska, Alaska
  3. 3.3 Fox Islands, Aleutian Islands, Alaska
  4. 1.8 19 km SW of Unalaska, Alaska
  5. 2.5 18 km W of Dutch Harbor, Alaska
  6. 1.7 17 km W of Dutch Harbor, Alaska
  7. 1.7 21 km SE of Unalaska, Alaska
  8. 1.5 3 km ESE of Unalaska, Alaska
  9. 1.9 2 km WSW of Dutch Harbor, Alaska
  10. 2.0 3 km WSW of Dutch Harbor, Alaska
  11. 2.2 3 km W of Unalaska, Alaska
  12. 1.5 2 km W of Dutch Harbor, Alaska
  13. 1.5 5 km W of Dutch Harbor, Alaska
  14. 1.6 3 km W of Unalaska, Alaska
  15. 1.8 3 km W 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.