Earthquake · reviewed by a seismologist
M 4.7mw
Earthquake near Anchorage, AK
No earthquake was likely felt in Anchorage in the 24 hours to 4:36 pm AKST (01:36 UTC). The last one was M 3.5, 39 km (24 mi) SSW, at 4:48 pm AKDT on 27 October 2026, estimated intensity II (weak) in town; 98 felt reports to USGS. Every earthquake near Anchorage
This page: a magnitude 4.7 earthquake was recorded 23 km (14 mi) north of Anchorage, AK, at 10:00 am AKST on 9 December 2018 (19:00 UTC), 41 km deep. 596 people have reported feeling it to USGS.
USGS: 7 km SW of Knik, Alaska
23 km (14 mi) N of Anchorage, AK
- When
- 10:00 am AKST on 9 December 2018 ()
- Where
- 23 km (14 mi) north of Anchorage, AK · earthquakes near Anchorage
- Magnitude
- M 4.7 (mw)
- Depth
- 41 km below the surface
- Felt
- 596 reports · strongest reported intensity V
- Measured shaking
- intensity IV (ShakeMap)
- USGS impact alert
- green
- Tsunami
- USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
- Nearest
- Anchorage Municipality, 40 km SE
- Nearest mapped fault
- Castle Mountain fault, 21 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 1183 days ago
Earthquake alerts for Anchorage, AK
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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 154 km (96 mi) from the epicentre. In Anchorage, 23 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 13 km, intensity III · Knik-Fairview 16 km, intensity III · Eagle River 18 km, intensity III · Anchorage 23 km, intensity III · Tanaina 32 km, intensity III · Willow 38 km, intensity III · Palmer 43 km, intensity III · Butte 45 km, intensity III. Estimated for each town centre; each link is that town's own record.
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.
- Northridge, California 1994 M 6.7 1,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 45× the energy of this one
- Magna, Utah 2020 M 5.7 32× the energy of this one
- This earthquake M 4.7 about 170 tons of TNT
- 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 7.1 on 2018-11-30 — about 4,000 times the energy of this one.
Before 2016, the USGS record lists 20 earthquakes of M5 or more within 50 km; the five largest:
- 5.6 11 km NW of Big Lake, Alaska · 23 km NW of this epicentre
- 5.6 5 km N of Susitna, Alaska · 41 km WNW of this epicentre
- 5.5 2 km ENE of Eagle River, Alaska · 20 km ESE of this epicentre
- 5.5 9 km E of Susitna, Alaska · 30 km WNW of this epicentre
- 5.5 26 km SSW of Anchorage, Alaska · 48 km SSW 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 61.4201, -149.8368. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Anchorage Municipality, AK | 40 km (25 mi) | SE | earthquakes near Anchorage Municipality |
| Matanuska-Susitna Borough, AK | 96 km (59 mi) | N | 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.
- 1.5 6 km S of Big Lake, Alaska
- 1.5 8 km NNW of Point MacKenzie, Alaska
- 1.5 5 km S of Big Lake, Alaska
- 2.7 3 km WNW of Point MacKenzie, Alaska
- 1.6 6 km WNW of Point MacKenzie, Alaska
- 1.8 4 km WNW of Point MacKenzie, Alaska
- 1.6 2 km NE of Big Lake, Alaska
- 1.6 2 km SSW of Big Lake, Alaska
- 2.1 3 km N of Big Lake, Alaska
- 2.3 3 km NW of Point MacKenzie, Alaska
- 1.6 4 km SSE of Big Lake, Alaska
- 2.2 8 km WSW of Knik, Alaska
- 1.6 7 km SSE of Big Lake, Alaska
- 1.8 3 km WNW of Big Lake, Alaska
- 1.5 2 km NW of Point MacKenzie, 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.