Earthquake · reviewed by a seismologist
M 2.8ml
Earthquake near Anchorage, AK
No earthquake was likely felt in Anchorage in the 24 hours to 5:26 am AKST (14:26 UTC). The last one was M 3.5, 39 km (24 mi) SSW, at 4:48 pm AKDT on 27 October 2026, estimated intensity II (weak) in town; 98 felt reports to USGS. Every earthquake near Anchorage
This page: a magnitude 2.8 earthquake was recorded 20 km (12 mi) south-southwest of Anchorage, AK, at 9:00 am AKDT on 20 August 2017 (17:00 UTC), 37 km deep. 24 people have reported feeling it to USGS.
USGS: Southern Alaska
20 km (12 mi) SSW of Anchorage, AK
- When
- 9:00 am AKDT on 20 August 2017 ()
- Where
- 20 km (12 mi) south-southwest of Anchorage, AK · earthquakes near Anchorage
- Magnitude
- M 2.8 (ml)
- Depth
- 37 km below the surface
- Felt
- 24 reports · strongest reported intensity IV
- Nearest
- Anchorage Municipality, 40 km ENE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1192 days ago
Earthquake alerts for Anchorage, AK
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Alerts are on for .
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This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth it was probably too small to be felt, even directly above it. In Anchorage, 20 km away, the estimate is intensity II (weak). 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
- Magna, Utah 2020 M 5.7 22,000× the energy of this one
- Around the size people start to feel M 3.0 2× the energy of this one
- This earthquake M 2.8 about 480 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 4.2 on 2016-02-15 — about 130 times the energy of this one.
Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:
- 6.8 24 km ENE of Sterling, Alaska · 49 km SSW of this epicentre
- 5.8 20 km ENE of Beluga, Alaska · 48 km WNW of this epicentre
- 5.7 13 km S of Girdwood, Alaska · 50 km ESE of this epicentre
- 5.5 2 km ENE of Eagle River, Alaska · 40 km NE of this epicentre
- 5.5 26 km SSW of Anchorage, Alaska · 9 km WSW 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 61.0413, -149.9792. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Anchorage Municipality, AK | 40 km (25 mi) | ENE | earthquakes near Anchorage Municipality |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 2.1 21 km WSW of Anchorage, Alaska
- 2.8 23 km ESE of Point Possession, Alaska
- 1.6 25 km WSW of Anchorage, Alaska
- 1.5 16 km SSE of Susitna, Alaska
- 1.7 1 km ENE of Knik, Alaska
- 3.9 1 km ENE of Knik, Alaska
- 2.2 19 km W of Point MacKenzie, Alaska
- 1.5 27 km NW of Cooper Landing, Alaska
- 1.7 4 km S of Big Lake, Alaska
- 1.8 15 km S of Hope, Alaska
- 1.5 14 km ESE of Point Possession, Alaska
- 2.0 24 km W of Point MacKenzie, Alaska
- 1.6 20 km W of Hope, Alaska
- 2.3 14 km W of Anchorage, Alaska
- 1.6 25 km NE of Point Possession, 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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.