92 km SSE of Ugashik, Alaska

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 8 km (5 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 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 4.5 on 2016-02-14 — about 11,000 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. 6.8 117 km SSE of Ugashik, Alaska · 25 km SSE of this epicentre May 29, 2015
2. 6.4 104 km SSE of Ugashik, Alaska · 20 km SSW of this epicentre May 20, 1979
3. 5.4 115 km SSE of Ugashik, Alaska · 22 km SE of this epicentre Jun 9, 1971
4. 5.4 113 km SSE of Ugashik, Alaska · 22 km SSE of this epicentre Jan 27, 2004
5. 5.3 117 km SSE of Ugashik, Alaska · 26 km S of this epicentre Dec 28, 1985

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 56.8087, -156.5766. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.7 68 km ESE of Ugashik, Alaska 06:52 UTC
2. 2.0 73 km ESE of Ugashik, Alaska 05:47 UTC
3. 3.3 56 km SE of Ugashik, Alaska 10:33 UTC
4. 2.3 49 km SE of Ugashik, Alaska 10:30 UTC
5. 2.5 51 km SE of Ugashik, Alaska 07:47 UTC
6. 2.4 53 km SE of Ugashik, Alaska 07:36 UTC
7. 3.1 60 km SE of Ugashik, Alaska 07:34 UTC
8. 1.8 87 km ENE of Chignik, Alaska 11:50 UTC
9. 2.3 115 km SSE of Ugashik, Alaska 20:33 UTC
10. 1.9 61 km SSE of Ugashik, Alaska 19:14 UTC
11. 1.9 100 km SE of Ugashik, Alaska 03:19 UTC
12. 2.3 124 km WSW of Akhiok, Alaska 03:05 UTC
13. 2.2 87 km ENE of Chignik, Alaska 23:26 UTC
14. 2.1 97 km SE of Ugashik, Alaska 10:44 UTC
15. 2.0 84 km SSE of Ugashik, Alaska 10:09 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 16:57 UTC. 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.