QuakeIndex

Earthquake · reviewed by a seismologist

M 4.9ml

79 km E of Ugashik, Alaska

Yes. A magnitude 4.9 earthquake was recorded 79 km E of Ugashik, Alaska at 09:18 UTC on 2020-02-17, 101 km deep. 8 people have reported feeling it to USGS.

· 101 km deep · released about 340 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lake and Peninsula Borough 69 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 4.9 (ml)
Depth
101 km below the surface
Felt
8 reports · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Nearest
Lake and Peninsula Borough, 69 km NNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2385 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 151 km (94 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 340 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 500× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 22× the energy of this one
  3. Magna, Utah 2020 M 5.7 16× the energy of this one
  4. This earthquake M 4.9 about 340 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 710× 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 5.3 on 2018-05-11 — about 4 times the energy of this one.

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

  1. 5.4 60 km E of Ugashik, Alaska · 21 km WSW of this epicentre
  2. 5.2 55 km WSW of Karluk, Alaska · 46 km ESE of this epicentre
  3. 5.2 67 km ESE of Egegik, Alaska · 47 km NNW of this epicentre
  4. 5.0 54 km WNW of Karluk, Alaska · 50 km ENE 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 57.5151, -156.0645. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lake and Peninsula Borough, AK 69 km (43 mi) NNW earthquakes near Lake and Peninsula 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. 1.7 68 km WSW of Karluk, Alaska
  2. 1.9 65 km ESE of Ugashik, Alaska
  3. 2.0 66 km W of Karluk, Alaska
  4. 1.6 76 km ESE of Egegik, Alaska
  5. 2.0 72 km W of Karluk, Alaska
  6. 2.5 86 km WSW of Karluk, Alaska
  7. 1.6 82 km ENE of Ugashik, Alaska
  8. 2.0 76 km ENE of Ugashik, Alaska
  9. 1.7 67 km E of Ugashik, Alaska
  10. 1.5 75 km E of Ugashik, Alaska
  11. 1.6 81 km E of Ugashik, Alaska
  12. 2.1 85 km SE of Ugashik, Alaska
  13. 1.5 70 km SE of Ugashik, Alaska
  14. 2.0 75 km ESE of Egegik, Alaska
  15. 1.6 77 km WNW of Karluk, 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.