Earthquake near Big Lake, AK

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 30 km (19 mi) from the epicentre. In Big Lake, 2 km away, the estimate is intensity II (weak). 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.

Likely felt in: Big Lake 2 km, intensity II · Knik-Fairview 17 km, intensity II · Willow 27 km, intensity II · Eagle River 28 km, intensity II · Tanaina 29 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,900 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.2 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 180,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 7,900× the energy of this one
3. Magna, Utah 2020 M 5.7 5,600× the energy of this one
4. This earthquake M 3.2 about 1,900 lb of TNT
5. Around the size people start to feel M 3.0 this one released 2× 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 7.1 on 2018-11-30 — about 710,000 times the energy of this one.

Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:

1. 5.9 23 km NE of Willow, Alaska · 46 km NNE of this epicentre Jan 1, 1975
2. 5.6 11 km NW of Big Lake, Alaska · 14 km NW of this epicentre Oct 7, 1966
3. 5.6 5 km N of Susitna, Alaska · 33 km WNW of this epicentre Dec 29, 1974
4. 5.5 2 km ENE of Eagle River, Alaska · 29 km SE of this epicentre May 11, 1965
5. 5.5 9 km E of Susitna, Alaska · 23 km W of this epicentre Dec 30, 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 61.5083, -149.9177. Map © OpenStreetMap contributors.

Nearby places

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

1. 2.5 1 km NW of Point MacKenzie, Alaska 08:31 UTC
2. 1.8 7 km NW of Point MacKenzie, Alaska 08:19 UTC
3. 1.9 3 km SE of Big Lake, Alaska 08:07 UTC
4. 1.5 7 km WSW of Knik, Alaska 08:01 UTC
5. 1.8 7 km NNW of Point MacKenzie, Alaska 07:57 UTC
6. 2.2 4 km SSE of Big Lake, Alaska 07:56 UTC
7. 1.7 7 km NW of Point MacKenzie, Alaska 07:45 UTC
8. 2.4 2 km SSE of Big Lake, Alaska 07:44 UTC
9. 2.0 4 km WNW of Point MacKenzie, Alaska 07:41 UTC
10. 1.8 4 km SE of Big Lake, Alaska 07:32 UTC
11. 1.6 4 km S of Big Lake, Alaska 07:29 UTC
12. 1.5 3 km SE of Big Lake, Alaska 07:21 UTC
13. 1.5 8 km NNW of Point MacKenzie, Alaska 07:19 UTC
14. 1.6 8 km SSW of Big Lake, Alaska 07:08 UTC
15. 1.5 3 km WNW of Point MacKenzie, Alaska 07:07 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 17:39 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.