QuakeIndex

Earthquake · reviewed by a seismologist

M 5.8mww

241 km ESE of Atka, Alaska

Yes. A magnitude 5.8 earthquake was recorded 241 km ESE of Atka, Alaska at 20:05 UTC on 2020-08-16, 18 km deep. 1 person has reported feeling it to USGS.

· 18 km deep · released about 7.6 kilotons 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 5.8 (mww)
Depth
18 km below the surface
Felt
1 report · strongest reported intensity II
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest mapped fault
Alaska-Aleutian subduction zone, 14 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 327 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 310 km (193 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 7.6 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.8 would have released about 32 times as much.

  1. Ridgecrest, California 2019 M 7.1 89× the energy of this one
  2. Loma Prieta, California 1989 M 6.9 45× the energy of this one
  3. Northridge, California 1994 M 6.7 22× the energy of this one
  4. This earthquake M 5.8 about 7.6 kilotons of TNT
  5. Magna, Utah 2020 M 5.7 this one released 1.4× more
  6. Around the size people start to feel M 3.0 this one released 16,000× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.3 on 2020-08-15.

Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 Fox Islands, Aleutian Islands, Alaska · 27 km N of this epicentre
  2. 6.9 240 km SE of Atka, Alaska · 26 km SSW of this epicentre
  3. 6.3 240 km SSW of Nikolski, Alaska · 27 km ESE of this epicentre
  4. 6.0 238 km SSW of Nikolski, Alaska · 23 km ESE of this epicentre
  5. 6.0 228 km ESE of Atka, Alaska · 14 km W 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 51.2142, -171.0880. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.7 265 km SSW of Nikolski, Alaska
  2. 3.1 265 km SE of Atka, Alaska
  3. 3.5 217 km ESE of Atka, Alaska
  4. 3.7 228 km SW of Nikolski, Alaska
  5. 2.8 216 km SW of Nikolski, Alaska
  6. 3.8 229 km SW of Nikolski, Alaska
  7. 3.7 234 km SW of Nikolski, Alaska
  8. 2.5 238 km ESE of Atka, Alaska
  9. 2.9 248 km ESE of Atka, Alaska
  10. 2.3 213 km SW of Nikolski, Alaska
  11. 3.1 215 km ESE of Atka, Alaska
  12. 3.0 217 km SW of Nikolski, Alaska
  13. 3.0 200 km SW of Nikolski, Alaska
  14. 3.7 243 km SE of Atka, Alaska
  15. 2.8 238 km ESE of Atka, 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.