QuakeIndex

ice quake · reviewed by a seismologist

M 1.9ml

Earthquake near Petersburg, AK

USGS: 36 km E of Petersburg, Alaska

3:58 am AKDT, Aug 27, 2020 · · 0.0 km deep · released about 21 lb of TNT

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10 km30 km60 km120 km N Petersburg Borough 48 kmWrangell City and Borough 79 km
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
3:58 am AKDT on 27 August 2020 ()
Where
37 km (23 mi) E of Petersburg, AK · earthquakes near Petersburg
Magnitude
M 1.9 (ml)
Depth
0.0 km below the surface
Felt
no reports yet
Nearest
Petersburg Borough, 48 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2212 days ago

A magnitude 1.9 earthquake was recorded 37 km (23 mi) E of Petersburg, AK, at 3:58 am AKDT on 27 August 2020 (11:58 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

USGS catalogues this as ice quake, not an earthquake.

How big was it?

This earthquake released about 21 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 710,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 500,000× the energy of this one
  3. Around the size people start to feel M 3.0 45× the energy of this one
  4. This earthquake M 1.9 about 21 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.

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 56.8672, -132.3592. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Petersburg Borough, AK 48 km (30 mi) NW earthquakes near Petersburg Borough
Wrangell City and Borough, AK 79 km (49 mi) SSE earthquakes near Wrangell City and Borough

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 2.1 42 km ENE of Petersburg, Alaska
  2. 2.0 75 km ENE of Petersburg, Alaska
  3. 2.5 73 km ENE of Petersburg, Alaska
  4. 2.0 44 km NNE of Wrangell, Alaska
  5. 1.7 70 km ENE of Petersburg, Alaska
  6. 2.8 34 km E of Petersburg, Alaska
  7. 1.9 37 km NE of Petersburg, Alaska
  8. 1.8 58 km ENE of Petersburg, Alaska
  9. 1.8 39 km N of Wrangell, Alaska
  10. 1.6 25 km E of Petersburg, Alaska
  11. 2.5 48 km NE of Wrangell, Alaska
  12. 1.9 34 km E of Petersburg, Alaska
  13. 2.1 33 km E of Petersburg, Alaska
  14. 1.8 48 km NNE of Wrangell, 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.