229 km WSW of Adak, 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 309 km (192 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 7.6 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.8 would have released about 32 times as much.

1. Ridgecrest, California 2019 M 7.1 89× the energy of this one
2. Loma Prieta, California 1989 M 6.9 45× the energy of this one
3. Northridge, California 1994 M 6.7 22× the energy of this one
4. This earthquake M 5.8 about 7.6 kilotons of TNT
5. Magna, Utah 2020 M 5.7 this one released 1.4× more
6. Around the size people start to feel M 3.0 this one released 16,000× 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 since 2016 was M 6.1 on 2020-01-26 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 152 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 238 km WSW of Adak, Alaska · 8 km WSW of this epicentre Mar 22, 1905
2. 7.2 207 km WSW of Adak, Alaska · 27 km NE of this epicentre Dec 19, 2007
3. 6.9 203 km WSW of Adak, Alaska · 29 km NE of this epicentre Mar 31, 1913
4. 6.9 231 km WSW of Adak, Alaska · 16 km NNW of this epicentre May 14, 1969
5. 6.8 235 km WSW of Adak, Alaska · 16 km NW of this epicentre May 6, 1987

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 51.1664, -179.7462. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 251 km WSW of Adak, Alaska 18:36 UTC
2. 2.0 240 km WSW of Adak, Alaska 18:24 UTC
3. 2.2 251 km WSW of Adak, Alaska 18:16 UTC
4. 3.3 237 km WSW of Adak, Alaska 16:44 UTC
5. 5.4 247 km WSW of Adak, Alaska 16:41 UTC
6. 2.2 255 km WSW of Adak, Alaska 03:31 UTC
7. 2.2 247 km WSW of Adak, Alaska 03:29 UTC
8. 2.4 249 km WSW of Adak, Alaska 02:15 UTC
9. 3.8 248 km WSW of Adak, Alaska 23:31 UTC
10. 4.0 245 km WSW of Adak, Alaska 22:31 UTC
11. 2.9 242 km WSW of Adak, Alaska 21:39 UTC
12. 2.4 235 km WSW of Adak, Alaska 20:49 UTC
13. 5.1 239 km WSW of Adak, Alaska 15:51 UTC
14. 2.8 242 km WSW of Adak, Alaska 08:20 UTC
15. 2.6 241 km WSW of Adak, Alaska 07:03 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:34 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.