Earthquake · reviewed by a seismologist
M 4.2ml
25 km NNE of Karluk, Alaska
Yes. A magnitude 4.2 earthquake was recorded 25 km NNE of Karluk, Alaska at 17:44 UTC on 2017-06-21, 56 km deep. 1 person has reported feeling it to USGS.
- When
- Magnitude
- M 4.2 (ml)
- Depth
- 56 km below the surface
- Felt
- 1 report · strongest reported intensity II
- Measured shaking
- intensity III (ShakeMap)
- USGS impact alert
- green
- Tsunami
- USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
- Nearest
- Kodiak Island Borough, 26 km ESE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1193 days ago
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 98 km (61 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 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 5,600× the energy of this one
- Mineral, Virginia 2011 M 5.8 250× the energy of this one
- Magna, Utah 2020 M 5.7 180× the energy of this one
- This earthquake M 4.2 about 30 tons of TNT
- Around the size people start to feel M 3.0 this one released 63× 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. No other earthquake of M4 or more has been recorded this close in that time.
Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:
- 7.1 4 km ENE of Karluk, Alaska · 23 km S of this epicentre
- 6.5 24 km SSW of Larsen Bay, Alaska · 49 km S of this epicentre
- 6.0 15 km S of Larsen Bay, Alaska · 47 km SSE of this epicentre
- 5.8 29 km NNE of Karluk, Alaska · 6 km ENE of this epicentre
- 5.7 6 km NE of Larsen Bay, Alaska · 33 km SE 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 57.7920, -154.3289. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Kodiak Island Borough, AK | 26 km (16 mi) | ESE | earthquakes near Kodiak Island Borough |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.7 20 km WNW of Karluk, Alaska
- 1.5 17 km SW of Karluk, Alaska
- 1.7 14 km WSW of Larsen Bay, Alaska
- 1.8 43 km NNE of Karluk, Alaska
- 2.9 59 km NNW of Karluk, Alaska
- 1.5 60 km N of Karluk, Alaska
- 1.7 12 km W of Larsen Bay, Alaska
- 2.0 71 km W of Aleneva, Alaska
- 1.7 26 km N of Larsen Bay, Alaska
- 1.8 24 km NNE of Karluk, Alaska
- 1.7 12 km ESE of Larsen Bay, Alaska
- 1.8 60 km N of Karluk, Alaska
- 1.6 63 km W of Aleneva, Alaska
- 3.6 46 km N of Karluk, Alaska
- 2.5 61 km NNW of Karluk, 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.