QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9ml

Earthquake near Anchorage, AK

No earthquake was likely felt in Anchorage in the 24 hours to 8:07 pm AKST (05:07 UTC). The last one was M 3.5, 39 km (24 mi) SSW, at 4:48 pm AKDT on 27 October 2026, estimated intensity II (weak) in town; 98 felt reports to USGS. Every earthquake near Anchorage

This page: a magnitude 3.9 earthquake was recorded 29 km (18 mi) north-northeast of Anchorage, AK, at 5:45 am AKST on 5 December 2017 (14:45 UTC), 31 km deep. 187 people have reported feeling it to USGS.

USGS: 1 km ENE of Knik, Alaska

29 km (18 mi) NNE of Anchorage, AK

5:45 am AKST, Dec 5, 2017 · · 31 km deep · released about 11 tons of TNT

Every earthquake near Anchorage Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Anchorage Municipality 39 kmMatanuska-Susitna Borough 90 km
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
5:45 am AKST on 5 December 2017 ()
Where
29 km (18 mi) north-northeast of Anchorage, AK · earthquakes near Anchorage
Magnitude
M 3.9 (ml)
Depth
31 km below the surface
Felt
187 reports · strongest reported intensity IV
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Nearest
Anchorage Municipality, 39 km SE
Nearest mapped fault
Castle Mountain fault, 19 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1190 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 84 km (52 mi) from the epicentre. In Anchorage, 29 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: Knik-Fairview 8 km, intensity III · Big Lake 15 km, intensity III · Eagle River 17 km, intensity III · Tanaina 24 km, intensity III · Anchorage 29 km, intensity III · Palmer 35 km, intensity II · Willow 36 km, intensity II · Butte 37 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 4.0 on 2016-04-08 — about 1.4 times the energy of this one.

Before 2016, the USGS record lists 17 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.9 23 km NE of Willow, Alaska · 50 km N of this epicentre
  2. 5.6 11 km NW of Big Lake, Alaska · 26 km WNW of this epicentre
  3. 5.6 5 km N of Susitna, Alaska · 45 km WNW of this epicentre
  4. 5.5 2 km ENE of Eagle River, Alaska · 17 km SE of this epicentre
  5. 5.5 9 km E of Susitna, Alaska · 35 km WNW 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 61.4606, -149.7029. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Anchorage Municipality, AK 39 km (24 mi) SE earthquakes near Anchorage Municipality
Matanuska-Susitna Borough, AK 90 km (56 mi) N earthquakes near Matanuska-Susitna Borough

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 1.5 15 km ENE of Willow, Alaska
  2. 1.7 12 km NE of Willow, Alaska
  3. 2.2 Southern Alaska
  4. 3.5 6 km NNW of Houston, Alaska
  5. 1.8 5 km NNW of Tanaina, Alaska
  6. 1.6 3 km S of Eagle River, Alaska
  7. 1.7 4 km SE of Houston, Alaska
  8. 1.5 3 km ENE of Knik, Alaska
  9. 2.0 6 km NW of Knik-Fairview, Alaska
  10. 1.5 7 km N of Houston, Alaska
  11. 1.5 15 km SW of Anchorage, Alaska
  12. 1.6 13 km WSW of Anchorage, Alaska
  13. 1.6 10 km NNE of Houston, Alaska
  14. 2.7 4 km NW of Houston, Alaska
  15. 2.5 11 km SW of Point MacKenzie, 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.