99 km ESE of Chignik, Alaska

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 291 km (181 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 5.4 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.7 would have released about 32 times as much.

1. Loma Prieta, California 1989 M 6.9 63× the energy of this one
2. Northridge, California 1994 M 6.7 32× the energy of this one
3. Mineral, Virginia 2011 M 5.8 1.4× the energy of this one
4. This earthquake M 5.7 about 5.4 kilotons of TNT
5. Around the size people start to feel M 3.0 this one released 11,000× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.1 on 2018-06-16.

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

1. 7.0 113 km ESE of Chignik, Alaska · 14 km ESE of this epicentre May 4, 1923
2. 6.9 143 km ESE of Chignik, Alaska · 45 km E of this epicentre Feb 13, 1951
3. 6.7 121 km SE of Chignik, Alaska · 48 km SSW of this epicentre Feb 13, 1979
4. 6.6 128 km SE of Chignik, Alaska · 32 km SSE of this epicentre Jul 28, 1934
5. 6.4 77 km ESE of Chignik, Alaska · 31 km NNW of this epicentre Mar 24, 1972

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 55.8758, -156.9924. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.2 south of Alaska 23:01 UTC
2. 2.6 125 km ESE of Chignik, Alaska 19:33 UTC
3. 2.4 south of Alaska 17:55 UTC
4. 2.1 139 km ESE of Chignik, Alaska 07:30 UTC
5. 2.9 129 km SE of Chignik, Alaska 06:54 UTC
6. 2.5 126 km SE of Chignik, Alaska 05:52 UTC
7. 2.5 112 km SE of Chignik, Alaska 20:04 UTC
8. 2.0 131 km SE of Chignik, Alaska 10:51 UTC
9. 1.7 67 km ESE of Chignik, Alaska 10:15 UTC
10. 2.8 126 km SE of Chignik, Alaska 06:07 UTC
11. 1.9 95 km SE of Chignik, Alaska 06:01 UTC
12. 2.2 139 km SE of Chignik, Alaska 03:27 UTC
13. 2.1 131 km SE of Chignik, Alaska 02:33 UTC
14. 2.3 125 km SE of Chignik, Alaska 02:02 UTC
15. 1.9 80 km SE of Chignik, Alaska 02:01 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 23:41 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.