99 km SE of Chignik, 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 15 km (9 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
3. Around the size people start to feel M 3.0 11× the energy of this one
4. This earthquake M 2.3 about 85 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 4.9 on 2017-02-27 — about 7,900 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. 6.9 105 km ESE of Perryville, Alaska · 23 km SW of this epicentre Nov 17, 1938
2. 6.7 121 km SE of Chignik, Alaska · 23 km ESE of this epicentre Feb 13, 1979
3. 6.6 128 km SE of Chignik, Alaska · 48 km E of this epicentre Jul 28, 1934
4. 6.0 98 km ESE of Perryville, Alaska · 27 km WSW of this epicentre Jan 2, 1985
5. 5.1 123 km SE of Chignik, Alaska · 29 km ESE of this epicentre Mar 16, 1977

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 55.5607, -157.4814. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.9 141 km SE of Perryville, Alaska 13:35 UTC
2. 3.7 90 km SE of Perryville, Alaska 01:16 UTC
3. 2.6 72 km ESE of Chignik, Alaska 01:10 UTC
4. 3.6 75 km SE of Chignik, Alaska 08:00 UTC
5. 2.8 77 km SE of Chignik, Alaska 09:23 UTC
6. 3.2 77 km SE of Chignik, Alaska 17:59 UTC
7. 4.2 109 km SE of Perryville, Alaska 21:17 UTC
8. 2.5 68 km SSE of Chignik, Alaska 05:04 UTC
9. 2.0 76 km ESE of Perryville, Alaska 08:02 UTC
10. 1.7 72 km SSE of Chignik, Alaska 06:19 UTC
11. 3.2 104 km SE of Perryville, Alaska 12:01 UTC
12. 2.5 104 km SE of Perryville, Alaska 10:44 UTC
13. 2.7 73 km SE of Chignik, Alaska 18:53 UTC
14. 2.2 81 km ESE of Chignik, Alaska 19:30 UTC
15. 2.6 95 km SE of Perryville, Alaska 21:09 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 12:51 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.