QuakeIndex

Earthquake · reviewed by a seismologist

M 2.2ml

161 km SSE of Unalaska, Alaska

Yes. A magnitude 2.2 earthquake was recorded 161 km SSE of Unalaska, Alaska at 16:39 UTC on 2021-10-13, 9.0 km deep.

· 9.0 km deep · released about 60 lb of TNT

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10 km30 km60 km120 km N
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 2.2 (ml)
Depth
9.0 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 18 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 1803 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 16 km (10 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 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.2 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 250,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 180,000× the energy of this one
  3. Around the size people start to feel M 3.0 16× the energy of this one
  4. This earthquake M 2.2 about 60 lb of TNT

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 4.3 on 2018-02-24 — about 1,400 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.5 198 km SSE of Unalaska, Alaska · 41 km S of this epicentre
  2. 5.1 162 km SSE of Akutan, Alaska · 42 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 52.6461, -165.2321. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.2 193 km SSE of Unalaska, Alaska
  2. 3.4 202 km SSE of Unalaska, Alaska
  3. 3.0 204 km SSE of Unalaska, Alaska
  4. 2.6 136 km SSE of Akutan, Alaska
  5. 1.9 120 km SSE of Unalaska, Alaska
  6. 1.9 115 km SSE of Unalaska, Alaska
  7. 2.1 198 km SSE of Unalaska, Alaska
  8. 2.6 south of the Aleutian Islands
  9. 2.7 194 km SSE of Unalaska, Alaska
  10. 1.7 179 km SSE of Unalaska, Alaska
  11. 2.8 198 km SSE of Unalaska, Alaska
  12. 1.9 127 km SE of Unalaska, Alaska
  13. 2.6 190 km SSE of Unalaska, Alaska
  14. 2.5 179 km SSE of Unalaska, Alaska
  15. 1.9 133 km SSE of Unalaska, 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.