QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3ml

218 km S of Sand Point, Alaska

Yes. A magnitude 2.3 earthquake was recorded 218 km S of Sand Point, Alaska at 06:57 UTC on 2021-08-11, 18 km deep.

· 18 km deep · released about 85 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 2.3 (ml)
Depth
18 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 20 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 1912 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 8 km (5 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
  3. Around the size people start to feel M 3.0 11× the energy of this one
  4. This earthquake M 2.3 about 85 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 5.7 on 2017-05-28 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 5.7 208 km SSE of Sand Point, Alaska · 50 km ENE of this epicentre
  2. 5.6 215 km SSE of King Cove, Alaska · 43 km WSW of this epicentre
  3. 5.5 241 km S of Sand Point, Alaska · 25 km SSE of this epicentre
  4. 5.5 233 km S of Sand Point, Alaska · 36 km ESE of this epicentre
  5. 5.3 232 km SSE of King Cove, Alaska · 19 km SSW 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 53.3749, -160.4922. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.5 208 km S of Sand Point, Alaska
  2. 3.4 238 km SSE of King Cove, Alaska
  3. 3.4 238 km SSE of King Cove, Alaska
  4. 3.7 224 km S of Sand Point, Alaska
  5. 3.1 240 km S of Sand Point, Alaska
  6. 3.3 207 km S of Sand Point, Alaska
  7. 2.8 229 km S of Sand Point, Alaska
  8. 2.0 217 km S of Sand Point, Alaska
  9. 2.9 238 km SSE of King Cove, Alaska
  10. 2.4 220 km S of Sand Point, Alaska
  11. 2.6 227 km S of Sand Point, Alaska
  12. 2.9 225 km S of Sand Point, Alaska
  13. 3.0 202 km S of Sand Point, Alaska
  14. 2.2 223 km SSE of King Cove, Alaska
  15. 2.8 215 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.