QuakeIndex

Earthquake · reviewed by a seismologist

M 4.4mb

154 km SSE of False Pass, Alaska

Yes. A magnitude 4.4 earthquake was recorded 154 km SSE of False Pass, Alaska at 13:12 UTC on 2021-07-22, 10 km deep. 1 person has reported feeling it to USGS.

· 10 km deep · released about 60 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 4.4 (mb)
Depth
10 km below the surface
Felt
1 report · strongest reported intensity II
Measured shaking
intensity I (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1831 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 129 km (80 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 60 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 2,800× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 130× the energy of this one
  3. Magna, Utah 2020 M 5.7 89× the energy of this one
  4. This earthquake M 4.4 about 60 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 130× 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 5.9 on 2016-10-27 — about 180 times the energy of this one.

Before 2016, the USGS record lists 25 earthquakes of M5 or more within 50 km; the five largest:

  1. 8.6 The 1946 Unimak Island, Alaska Earthquake · 3 km SW of this epicentre
  2. 6.2 172 km SSE of False Pass, Alaska · 20 km S of this epicentre
  3. 6.1 166 km S of False Pass, Alaska · 27 km SW of this epicentre
  4. 6.0 155 km S of False Pass, Alaska · 44 km W of this epicentre
  5. 6.0 129 km S of False Pass, Alaska · 46 km WNW 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 53.5144, -162.7950. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.8 120 km S of False Pass, Alaska
  2. 1.9 120 km S of False Pass, Alaska
  3. 2.2 132 km SSE of False Pass, Alaska
  4. 2.1 112 km S of False Pass, Alaska
  5. 3.8 117 km S of False Pass, Alaska
  6. 2.8 south of Alaska
  7. 2.5 142 km S of False Pass, Alaska
  8. 3.5 155 km S of False Pass, Alaska
  9. 1.7 Unimak Island region, Alaska
  10. 2.0 108 km SSE of False Pass, Alaska
  11. 2.8 195 km SSE of False Pass, Alaska
  12. 2.0 114 km S of False Pass, Alaska
  13. 2.2 154 km SSE of False Pass, Alaska
  14. 3.1 Unimak Island region, Alaska
  15. 2.9 141 km S of False Pass, 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.