116 km SE of Old Harbor, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 159 km (99 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 170 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.7 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 1,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 45× the energy of this one
3. Magna, Utah 2020 M 5.7 32× the energy of this one
4. This earthquake M 4.7 about 170 tons of TNT
5. Around the size people start to feel M 3.0 this one released 350× more

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 5.4 on 2017-05-11 — about 11 times the energy of this one.

Before 2016, the USGS record lists 64 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 100 km SSE of Old Harbor, Alaska · 44 km W of this epicentre Jun 19, 1986
2. 6.6 88 km SSE of Old Harbor, Alaska · 41 km WNW of this epicentre Dec 21, 1917
3. 6.6 94 km SSE of Old Harbor, Alaska · 32 km WNW of this epicentre Apr 12, 1978
4. 6.4 95 km S of Old Harbor, Alaska · 50 km W of this epicentre Apr 16, 1964
5. 6.3 98 km SE of Old Harbor, Alaska · 18 km NNW of this epicentre Apr 12, 1964

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 56.3493, -152.1933. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 117 km SE of Old Harbor, Alaska 18:56 UTC
2. 3.0 Kodiak Island region, Alaska 11:23 UTC
3. 2.6 107 km SSE of Old Harbor, Alaska 10:41 UTC
4. 2.8 Kodiak Island region, Alaska 17:08 UTC
5. 2.4 73 km SE of Old Harbor, Alaska 23:50 UTC
6. 2.9 139 km SE of Old Harbor, Alaska 08:29 UTC
7. 4.1 108 km SSE of Old Harbor, Alaska 17:57 UTC
8. 2.4 103 km SSE of Old Harbor, Alaska 16:17 UTC
9. 4.5 105 km SSE of Old Harbor, Alaska 23:08 UTC
10. 2.7 97 km SSE of Old Harbor, Alaska 13:25 UTC
11. 2.5 134 km SSE of Old Harbor, Alaska 10:09 UTC
12. 1.7 120 km SSE of Old Harbor, Alaska 16:07 UTC
13. 2.2 114 km SSE of Old Harbor, Alaska 16:07 UTC
14. 2.0 113 km SE of Old Harbor, Alaska 18:00 UTC
15. 2.8 108 km SSE of Old Harbor, Alaska 18:48 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 02:05 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.