QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

149 km S of Sand Point, Alaska

Yes. A magnitude 2.1 earthquake was recorded 149 km S of Sand Point, Alaska, at 8:20 pm AKDT on 13 April 2021 (04:20 UTC), 32 km deep.

· 32 km deep · released about 43 lb 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 2.1 (ml)
Depth
32 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2014 days ago

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

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 43 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 350,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 250,000× the energy of this one
  3. Around the size people start to feel M 3.0 22× the energy of this one
  4. This earthquake M 2.1 about 43 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 5.8 on 2018-07-19 — about 350,000 times the energy of this one.

Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 109 km SSE of King Cove, Alaska · 43 km NW of this epicentre
  2. 6.4 159 km SSE of King Cove, Alaska · 27 km SW of this epicentre
  3. 6.2 141 km SSE of King Cove, Alaska · 18 km W of this epicentre
  4. 5.9 131 km S of Sand Point, Alaska · 35 km ENE of this epicentre
  5. 5.5 137 km S of Sand Point, Alaska · 13 km N 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 54.0116, -160.8648. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 102 km SSW of Sand Point, Alaska
  2. 2.7 151 km SSE of King Cove, Alaska
  3. 3.9 117 km SSW of Sand Point, Alaska
  4. 2.6 180 km SSE of King Cove, Alaska
  5. 2.7 121 km S of Sand Point, Alaska
  6. 2.0 113 km SSW of Sand Point, Alaska
  7. 1.7 115 km S of Sand Point, Alaska
  8. 1.6 103 km SSW of Sand Point, Alaska
  9. 3.0 109 km SSW of Sand Point, Alaska
  10. 4.1 113 km SSW of Sand Point, Alaska
  11. 3.1 129 km S of Sand Point, Alaska
  12. 3.1 118 km SSW of Sand Point, Alaska
  13. 2.1 123 km S of Sand Point, Alaska
  14. 2.1 147 km SE of King Cove, Alaska
  15. 2.9 109 km S of Sand Point, 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.