QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mw

50 km N of Chase, Alaska

Yes. A magnitude 4.2 earthquake was recorded 50 km N of Chase, Alaska, at 11:22 pm AKDT on 12 September 2017 (07:22 UTC), 80 km deep. 42 people have reported feeling it to USGS.

· 80 km deep · released about 30 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Matanuska-Susitna Borough 74 kmDenali Borough 87 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
Magnitude
M 4.2 (mw)
Depth
80 km below the surface
Felt
42 reports · strongest reported intensity IV
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Nearest
Matanuska-Susitna Borough, 74 km SSE
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 80 km (50 mi) from the epicentre. 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.

How big was it?

This earthquake released about 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 5,600× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 250× the energy of this one
  3. Magna, Utah 2020 M 5.7 180× the energy of this one
  4. This earthquake M 4.2 about 30 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 63× 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 4.6 on 2016-04-26 — about 4 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.7 66 km ESE of Denali National Park, Alaska · 49 km NW of this epicentre
  2. 5.6 44 km S of Cantwell, AK · 48 km ENE of this epicentre
  3. 5.5 52 km WSW of Cantwell, Alaska · 30 km N of this epicentre
  4. 5.4 70 km WSW of Cantwell, Alaska · 35 km NNW of this epicentre
  5. 5.4 48 km N of Petersville, Alaska · 37 km W 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 62.8983, -149.9213. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Matanuska-Susitna Borough, AK 74 km (46 mi) SSE earthquakes near Matanuska-Susitna Borough
Denali Borough, AK 87 km (54 mi) N earthquakes near Denali Borough

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

Aftershocks so far

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

  1. 1.5 57 km SSW of Cantwell, Alaska
  2. 2.0 54 km N of Chase, Alaska
  3. 1.9 43 km NNE of Chase, Alaska
  4. 1.7 76 km SE of Denali National Park, Alaska
  5. 1.6 38 km NE of Chase, Alaska
  6. 1.5 71 km NNE of Petersville, Alaska
  7. 1.9 43 km NNE of Petersville, Alaska
  8. 1.5 36 km NNE of Chase, Alaska
  9. 1.5 43 km NNE of Chase, Alaska
  10. 1.6 16 km ENE of Chase, Alaska
  11. 1.6 54 km NNE of Chase, Alaska
  12. 1.5 51 km N of Chase, Alaska
  13. 1.6 74 km NNE of Petersville, Alaska
  14. 1.7 44 km NNE of Chase, Alaska
  15. 1.8 43 km WSW of Cantwell, 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.