QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Butte, AK

No earthquake was likely felt in Butte in the 24 hours to 7:07 am AKST (16:07 UTC). The last one was M 4.4, 112 km (69 mi) ENE, at 11:11 am AKDT on 30 October 2026, estimated intensity II (weak) in town; 54 felt reports to USGS. Every earthquake near Butte

This page: a magnitude 1.8 earthquake was recorded 50 km (31 mi) east-northeast of Butte, AK, at 8:56 pm AKDT on 28 August 2020 (04:56 UTC), 11 km deep.

USGS: 25 km SE of Chickaloon, Alaska

8:56 pm AKDT, Aug 28, 2020 · · 11 km deep · released about 15 lb of TNT

Every earthquake near Butte Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Anchorage Municipality 80 kmMatanuska-Susitna Borough 101 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
8:56 pm AKDT on 28 August 2020 ()
Where
50 km (31 mi) east-northeast of Butte, AK · earthquakes near Butte
Magnitude
M 1.8 (ml)
Depth
11 km below the surface
Felt
no reports yet
Nearest
Anchorage Municipality, 80 km SW
Nearest mapped fault
Castle Mountain fault, 24 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 2249 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 9 km (6 mi) from the epicentre. In Butte, 50 km away, the estimate is intensity I (not felt). 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 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 710,000× the energy of this one
  3. Around the size people start to feel M 3.0 63× the energy of this one
  4. This earthquake M 1.8 about 15 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 4.6 on 2018-01-27 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 31 km SSW of Glacier View, Alaska · 21 km ESE of this epicentre
  2. 6.4 23 km S of Glacier View, Alaska · 24 km E of this epicentre
  3. 6.4 37 km SSE of Glacier View, Alaska · 41 km ESE of this epicentre
  4. 5.9 15 km N of Glacier View, Alaska · 41 km NNE of this epicentre
  5. 5.9 42 km S of Glacier View, Alaska · 36 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 61.6328, -148.1155. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Anchorage Municipality, AK 80 km (50 mi) SW earthquakes near Anchorage Municipality
Matanuska-Susitna Borough, AK 101 km (63 mi) NW earthquakes near Matanuska-Susitna Borough

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

Aftershocks so far

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

  1. 1.8 48 km S of Glacier View, Alaska
  2. 2.2 30 km NE of Chickaloon, Alaska
  3. 1.9 31 km SSW of Glacier View, Alaska
  4. 1.7 30 km NNE of Chickaloon, Alaska
  5. 2.6 23 km S of Glacier View, Alaska
  6. 1.6 32 km SSE of Chickaloon, Alaska
  7. 1.8 4 km ESE of Chickaloon, Alaska
  8. 1.5 59 km S of Glacier View, Alaska
  9. 2.1 34 km SE of Chickaloon, Alaska
  10. 2.4 4 km NE of Chickaloon, Alaska
  11. 1.9 28 km SSE of Chickaloon, Alaska
  12. 1.9 30 km SSE of Chickaloon, Alaska
  13. 1.9 33 km SSE of Chickaloon, Alaska
  14. 2.3 31 km SSE of Chickaloon, Alaska
  15. 2.1 33 km SSE of Chickaloon, 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.