QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

Earthquake near Akutan, AK

No earthquake was likely felt in Akutan in the 24 hours to 2:25 pm AKST (23:25 UTC). The last one was M 4.4, 84 km (52 mi) SE, at 3:00 pm AKST on 11 November 2026, estimated intensity II (weak) in town. Every earthquake near Akutan

This page: a magnitude 3.9 earthquake was recorded 39 km (24 mi) southeast of Akutan, AK, at 6:49 pm AKST on 20 December 2016 (03:49 UTC), 63 km deep. 1 person has reported feeling it to USGS.

USGS: 38 km SE of Akutan, Alaska

6:49 pm AKST, Dec 20, 2016 · · 63 km deep · released about 11 tons 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
6:49 pm AKST on 20 December 2016 ()
Where
39 km (24 mi) southeast of Akutan, AK · earthquakes near Akutan
Magnitude
M 3.9 (mb)
Depth
63 km below the surface
Felt
1 report · strongest reported intensity II
Measured shaking
intensity III (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1197 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 63 km (39 mi) from the epicentre. In Akutan, 39 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: Akutan 39 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× more

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 2016-09-18 — about 22 times the energy of this one.

Before 2016, the USGS record lists 35 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 39 km S of Akutan, Alaska · 35 km WSW of this epicentre
  2. 6.5 59 km ESE of Akutan, Alaska · 23 km E of this epicentre
  3. 6.5 83 km SE of Akutan, Alaska · 45 km ESE of this epicentre
  4. 6.5 81 km ESE of Akutan, Alaska · 43 km ESE of this epicentre
  5. 6.4 50 km SE of Akutan, Alaska · 13 km SSE 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 53.9292, -165.2967. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.0 22 km SE of Akutan, Alaska
  2. 2.4 43 km SE of Akutan, Alaska
  3. 1.9 Fox Islands, Aleutian Islands, Alaska
  4. 1.5 57 km SSE of Akutan, Alaska
  5. 1.8 40 km SE of Akutan, Alaska
  6. 1.9 53 km E of Akutan, Alaska
  7. 2.0 39 km E of Akutan, Alaska
  8. 3.7 62 km SSE of Akutan, Alaska
  9. 1.8 47 km S of Akutan, Alaska
  10. 1.8 66 km ESE of Akutan, Alaska
  11. 1.8 40 km SE of Akutan, Alaska
  12. 2.0 30 km E of Akutan, Alaska
  13. 2.1 69 km S of Akutan, Alaska
  14. 2.6 46 km E of Akutan, Alaska
  15. 1.9 72 km SSE 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.