QuakeIndex

Earthquake · reviewed by a seismologist

M 3.3ml

256 km SW of Adak, Alaska

Yes. A magnitude 3.3 earthquake was recorded 256 km SW of Adak, Alaska at 03:26 UTC on 2020-03-15, 10 km deep.

· 10 km deep · released about 1.3 tons 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 3.3 (ml)
Depth
10 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 2359 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 51 km (32 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 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 130,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
  3. Magna, Utah 2020 M 5.7 4,000× the energy of this one
  4. This earthquake M 3.3 about 1.3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 2.8× 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 4.3 on 2017-07-01 — about 32 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. 6.8 Andreanof Islands, Aleutian Islands, Alaska · 28 km ESE of this epicentre
  2. 6.7 254 km SW of Adak, Alaska · 40 km NW of this epicentre
  3. 6.0 207 km SW of Adak, Alaska · 49 km NE of this epicentre
  4. 6.0 254 km SW of Adak, Alaska · 26 km SE of this epicentre
  5. 6.0 257 km SW of Adak, Alaska · 13 km SE 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 50.1868, -179.1259. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 263 km SW of Adak, Alaska
  2. 2.2 292 km SW of Adak, Alaska
  3. 3.7 269 km SW of Adak, Alaska
  4. 3.6 266 km SW of Adak, Alaska
  5. 3.0 270 km SW of Adak, Alaska
  6. 3.0 252 km SW of Adak, Alaska
  7. 3.0 261 km SW of Adak, Alaska
  8. 2.4 237 km SW of Adak, Alaska
  9. 3.1 284 km SW of Adak, Alaska
  10. 2.9 285 km SW of Adak, Alaska
  11. 2.6 270 km SW of Adak, Alaska
  12. 2.0 263 km SW of Adak, Alaska
  13. 2.1 262 km SW of Adak, Alaska
  14. 2.6 262 km SW of Adak, Alaska
  15. 2.2 239 km SW of Adak, 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.