QuakeIndex

Earthquake · reviewed by a seismologist

M 1.5ml

Earthquake near Willow, AK

No earthquake was likely felt in Willow in the 24 hours to 8:17 pm AKST (05:17 UTC). The last one was M 2.8, 20 km (12 mi) S, at 6:17 am AKST on 6 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Willow

This page: a magnitude 1.5 earthquake was recorded 7 km (4 mi) north-northeast of Willow, AK, at 6:41 pm AKDT on 21 April 2017 (02:41 UTC), 40 km deep.

USGS: 6 km NNE of Willow, Alaska

65 km (41 mi) N of Anchorage, AK

6:41 pm AKDT, Apr 21, 2017 · · 40 km deep · released about 5.4 lb of TNT

Every earthquake near Willow Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Matanuska-Susitna Borough 57 kmAnchorage Municipality 79 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
6:41 pm AKDT on 21 April 2017 ()
Where
7 km (4 mi) north-northeast of Willow, AK · earthquakes near Willow
Magnitude
M 1.5 (ml)
Depth
40 km below the surface
Felt
no reports yet
Nearest
Matanuska-Susitna Borough, 57 km NNE
Nearest mapped fault
Castle Mountain fault, 20 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 1193 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. In Willow, 7 km away, the estimate is intensity I (not felt). 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: Houston, Meadow Lakes.

How big was it?

This earthquake released about 5.4 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,800,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 2,000,000× the energy of this one
  3. Around the size people start to feel M 3.0 180× the energy of this one
  4. This earthquake M 1.5 about 5.4 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 4.1 on 2016-07-21 — about 7,900 times the energy of this one.

Before 2016, the USGS record lists 18 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.9 23 km NE of Willow, Alaska · 18 km NE of this epicentre
  2. 5.8 14 km NNE of Fishhook, Alaska · 47 km E of this epicentre
  3. 5.6 11 km NW of Big Lake, Alaska · 26 km SSW of this epicentre
  4. 5.6 5 km N of Susitna, Alaska · 36 km SW of this epicentre
  5. 5.5 9 km E of Susitna, Alaska · 34 km SSW 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 61.8026, -149.9939. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Matanuska-Susitna Borough, AK 57 km (36 mi) NNE earthquakes near Matanuska-Susitna Borough
Anchorage Municipality, AK 79 km (49 mi) SSE earthquakes near Anchorage Municipality

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

Aftershocks so far

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

  1. 1.5 10 km SSE of Susitna North, Alaska
  2. 3.0 25 km SE of Susitna North, Alaska
  3. 1.8 3 km N of Big Lake, Alaska
  4. 1.6 15 km ESE of Susitna, Alaska
  5. 1.7 5 km NNE of Big Lake, Alaska
  6. 1.9 11 km SSW of Willow, Alaska
  7. 2.5 15 km ESE of Susitna, Alaska
  8. 2.4 12 km NNW of Willow, Alaska
  9. 1.5 0 km SW of Point MacKenzie, Alaska
  10. 2.5 29 km SSW of Trapper Creek, Alaska
  11. 1.5 12 km NNE of Houston, Alaska
  12. 1.8 15 km NNW of Willow, Alaska
  13. 2.1 4 km SE of Houston, Alaska
  14. 1.5 22 km ENE of Willow, Alaska
  15. 1.5 6 km SSW of Houston, 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.