Earthquake · reviewed by a seismologist
M 4.1ml
Earthquake near Big Lake, AK
No earthquake was likely felt in Big Lake in the 24 hours to 8:41 pm AKST (05:41 UTC). The last one was M 2.8, 6 km (4 mi) NW, at 6:17 am AKST on 6 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Big Lake
This page: a magnitude 4.1 earthquake was recorded 5 km (3 mi) east of Big Lake, AK, at 7:14 am AKDT on 23 March 2019 (15:14 UTC), 47 km deep. 242 people have reported feeling it to USGS.
USGS: 4 km E of Big Lake, Alaska
34 km (21 mi) N of Anchorage, AK
- When
- 7:14 am AKDT on 23 March 2019 ()
- Where
- 5 km (3 mi) east of Big Lake, AK · earthquakes near Big Lake
- Magnitude
- M 4.1 (ml)
- Depth
- 47 km below the surface
- Felt
- 242 reports · strongest reported intensity IV
- Measured shaking
- intensity III (ShakeMap)
- USGS impact alert
- green
- Tsunami
- USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
- Nearest
- Anchorage Municipality, 50 km SE
- Nearest mapped fault
- Castle Mountain fault, 9 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2084 days ago
Earthquake alerts for Big Lake, AK
Get a notification in this browser when USGS records an earthquake near Big Lake, AK. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 93 km (58 mi) from the epicentre. In Big Lake, 5 km away, the estimate is intensity III (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 5 km, intensity III · Knik-Fairview 14 km, intensity III · Tanaina 26 km, intensity III · Willow 26 km, intensity III · Eagle River 28 km, intensity II · Anchorage 34 km, intensity II · Palmer 40 km, intensity II · Fishhook 41 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 21 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 7,900× the energy of this one
- Mineral, Virginia 2011 M 5.8 350× the energy of this one
- Magna, Utah 2020 M 5.7 250× the energy of this one
- This earthquake M 4.1 about 21 tons of TNT
- Around the size people start to feel M 3.0 this one released 45× 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 32,000 times the energy of this one.
Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:
- 5.9 23 km NE of Willow, Alaska · 43 km N of this epicentre
- 5.6 11 km NW of Big Lake, Alaska · 15 km WNW of this epicentre
- 5.6 5 km N of Susitna, Alaska · 35 km WNW of this epicentre
- 5.5 2 km ENE of Eagle River, Alaska · 28 km SE of this epicentre
- 5.5 9 km E of Susitna, Alaska · 25 km W of this epicentre
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 61.5263, -149.8616. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Anchorage Municipality, AK | 50 km (31 mi) | SE | earthquakes near Anchorage Municipality |
| Matanuska-Susitna Borough, AK | 84 km (52 mi) | NNE | earthquakes near Matanuska-Susitna Borough |
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.
- 2.4 8 km NE of Point MacKenzie, Alaska
- 2.0 5 km WNW of Point MacKenzie, Alaska
- 1.8 6 km NW of Point MacKenzie, Alaska
- 1.9 7 km NW of Point MacKenzie, Alaska
- 1.5 2 km W of Point MacKenzie, Alaska
- 2.3 Southern Alaska
- 1.8 Southern Alaska
- 2.8 7 km S of Big Lake, Alaska
- 2.2 4 km WNW of Point MacKenzie, Alaska
- 1.6 17 km SSE of Susitna, Alaska
- 1.6 7 km N of Houston, Alaska
- 2.8 8 km NW of Point MacKenzie, Alaska
- 2.0 6 km WSW of Point MacKenzie, Alaska
- 1.5 10 km SW of Big Lake, Alaska
- 1.6 17 km WSW of Big Lake, Alaska
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . 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.