QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8ml

Earthquake near Unalaska, AK

No earthquake was likely felt in Unalaska in the 24 hours to 1:39 pm AKST (22:39 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 2.8 earthquake was recorded 22 km (14 mi) south-southeast of Unalaska, AK, at 11:53 pm AKDT on 21 October 2019 (07:53 UTC), 78 km deep.

USGS: 22 km SSE of Unalaska, Alaska

11:53 pm AKDT, Oct 21, 2019 · · 78 km deep · released about 480 lb of TNT

Every earthquake near Unalaska Felt it? Tell USGS Check my area
10 km30 km60 km120 km N
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
11:53 pm AKDT on 21 October 2019 ()
Where
22 km (14 mi) south-southeast of Unalaska, AK · earthquakes near Unalaska
Magnitude
M 2.8 (ml)
Depth
78 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2498 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 it was probably too small to be felt, even directly above it. In Unalaska, 22 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.

Earthquakes near other towns within 30 km: Dutch Harbor.

How big was it?

This earthquake released about 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
  3. Around the size people start to feel M 3.0 2× the energy of this one
  4. This earthquake M 2.8 about 480 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 2019-09-27 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists 21 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 39 km S of Akutan, Alaska · 43 km ENE of this epicentre
  2. 6.2 57 km SE of Unalaska, Alaska · 39 km ESE of this epicentre
  3. 6.2 36 km ESE of Unalaska, Alaska · 23 km E of this epicentre
  4. 6.1 56 km SSW of Unalaska, Alaska · 42 km SW of this epicentre
  5. 6.1 63 km SSW of Unalaska, Alaska · 50 km SW 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 53.6903, -166.4061. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.5 24 km SE of Unalaska, Alaska
  2. 2.5 39 km SE of Unalaska, Alaska
  3. 1.8 64 km SE of Unalaska, Alaska
  4. 2.2 28 km SW of Unalaska, Alaska
  5. 3.7 59 km S of Unalaska, Alaska
  6. 1.9 28 km E of Unalaska, Alaska
  7. 1.9 25 km S of Unalaska, Alaska
  8. 4.4 27 km S of Unalaska, Alaska
  9. 1.5 63 km SE of Unalaska, Alaska
  10. 1.5 34 km SE of Unalaska, Alaska
  11. 2.2 6 km WSW of Unalaska, Alaska
  12. 2.8 45 km SE of Unalaska, Alaska
  13. 4.8 35 km SE of Unalaska, Alaska
  14. 2.0 47 km SE of Unalaska, Alaska
  15. 2.1 32 km S of Akutan, 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.