QuakeIndex

Earthquake · reviewed by a seismologist

M 4.7ml

110 km SSE of Port Graham, Alaska

Yes. A magnitude 4.7 earthquake was recorded 110 km SSE of Port Graham, Alaska, at 3:22 am AKDT on 10 October 2020 (11:22 UTC), 46 km deep. 7 people have reported feeling it to USGS.

· 46 km deep · released about 170 tons of TNT

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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 4.7 (ml)
Depth
46 km below the surface
Felt
7 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2155 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 153 km (95 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 170 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.7 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 45× the energy of this one
  3. Magna, Utah 2020 M 5.7 32× the energy of this one
  4. This earthquake M 4.7 about 170 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 350× 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 5.0 on 2019-06-07 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 124 km SSE of Halibut Cove, Alaska · 43 km ENE of this epicentre
  2. 6.5 78 km ENE of Ouzinkie, Alaska · 45 km SW of this epicentre
  3. 5.8 124 km ENE of Ouzinkie, Alaska · 22 km SE of this epicentre
  4. 5.7 78 km SSE of Port Graham, Alaska · 32 km NNW of this epicentre
  5. 5.5 122 km ENE of Kodiak, Alaska · 47 km SSE 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 58.5157, -150.7842. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.9 91 km SSE of Halibut Cove, Alaska
  2. 2.4 99 km ENE of Ouzinkie, Alaska
  3. 1.8 82 km ENE of Ouzinkie, Alaska
  4. 1.7 82 km ENE of Ouzinkie, Alaska
  5. 2.2 101 km NE of Ouzinkie, Alaska
  6. 1.8 100 km ENE of Ouzinkie, Alaska
  7. 1.8 92 km ENE of Ouzinkie, Alaska
  8. 2.4 87 km ENE of Ouzinkie, Alaska
  9. 1.9 102 km ENE of Ouzinkie, Alaska
  10. 1.6 104 km ENE of Ouzinkie, Alaska
  11. 2.0 89 km ENE of Ouzinkie, Alaska
  12. 1.7 96 km SSE of Halibut Cove, Alaska
  13. 1.6 100 km ENE of Ouzinkie, Alaska
  14. 2.0 Gulf of Alaska
  15. 2.7 104 km ENE of Ouzinkie, 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.