QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mw

Earthquake near Healy, AK

No earthquake was likely felt in Healy in the 24 hours to 2:12 am AKST (11:12 UTC). The last one was M 2.7, 23 km (14 mi) NNE, at 4:13 pm AKST on 3 November 2026, estimated intensity II (weak) in town. Every earthquake near Healy

This page: a magnitude 4.0 earthquake was recorded 7 km (4 mi) south-southwest of Healy, AK, at 2:43 am AKST on 30 December 2017 (11:43 UTC), 7.1 km deep. 48 people have reported feeling it to USGS.

USGS: 6 km SSW of Healy, Alaska

2:43 am AKST, Dec 30, 2017 · · 7.1 km deep · released about 15 tons of TNT

Every earthquake near Healy Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Denali Borough 51 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
2:43 am AKST on 30 December 2017 ()
Where
7 km (4 mi) south-southwest of Healy, AK · earthquakes near Healy
Magnitude
M 4.0 (mw)
Depth
7.1 km below the surface
Felt
48 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Nearest
Denali Borough, 51 km WSW
Nearest mapped fault
Park Road fault (Northern Foothills fold and thrust belt), 9 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 1191 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 97 km (60 mi) from the epicentre. In Healy, 7 km away, the estimate is intensity IV (light). 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: Healy 7 km, intensity IV. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 11,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
  3. Magna, Utah 2020 M 5.7 350× the energy of this one
  4. This earthquake M 4.0 about 15 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 32× 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 4.1 on 2016-07-11 — about 1.4 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 7.1 Central Alaska · 37 km NE of this epicentre
  2. 6.4 23 km ENE of Ferry, Alaska · 39 km NNE of this epicentre
  3. 6.1 35 km E of Healy, Alaska · 40 km ENE of this epicentre
  4. 5.0 30 km W of Ferry, Alaska · 43 km NW 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 63.8011, -149.0240. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Denali Borough, AK 51 km (32 mi) WSW earthquakes near Denali Borough

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. 1.8 15 km E of McKinley Park, Alaska
  2. 1.7 22 km W of Cantwell, Alaska
  3. 1.7 8 km NNE of Healy, Alaska
  4. 1.8 18 km W of Cantwell, Alaska
  5. 1.6 20 km E of Healy, Alaska
  6. 1.6 16 km ESE of McKinley Park, Alaska
  7. 1.8 8 km N of Healy, Alaska
  8. 2.2 10 km WSW of Healy, Alaska
  9. 1.6 18 km W of McKinley Park, Alaska
  10. 1.6 36 km WSW of McKinley Park, Alaska
  11. 1.7 8 km NW of McKinley Park, Alaska
  12. 1.6 14 km NW of Cantwell, Alaska
  13. 2.1 22 km WSW of McKinley Park, Alaska
  14. 2.6 28 km W of Healy, Alaska
  15. 1.5 7 km N of Healy, 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.