Earthquake · reviewed by a seismologist
M 4.0mb
Alaska Peninsula
Yes. A magnitude 4.0 earthquake was recorded in the Alaska Peninsula, at 12:04 am AKDT on 22 July 2020 (08:04 UTC), 44 km deep.
- When
- Magnitude
- M 4.0 (mb)
- Depth
- 44 km below the surface
- Felt
- no reports yet
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2232 days ago
Earthquake alerts for Sand Point, 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 86 km (53 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 11,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 500× the energy of this one
- Magna, Utah 2020 M 5.7 350× the energy of this one
- This earthquake M 4.0 about 15 tons of TNT
- Around the size people start to feel M 3.0 this one released 32× 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 in our catalogue was M 6.1 on 2020-07-22 — about 1,400 times the energy of this one.
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 55.1692, -159.3191. Map © OpenStreetMap contributors.
Aftershocks so far
53 earthquakes have been recorded within 50 km since this one.
- 1.7 82 km S of Perryville, Alaska
- 1.7 70 km S of Ivanof Bay, Alaska
- 1.7 82 km S of Perryville, Alaska
- 1.9 79 km S of Perryville, Alaska
- 1.7 59 km ESE of Sand Point, Alaska
- 3.8 82 km ESE of Sand Point, Alaska
- 4.0 85 km ESE of Sand Point, Alaska
- 1.7 66 km ESE of Sand Point, Alaska
- 1.9 68 km ESE of Sand Point, Alaska
- 2.2 96 km SSE of Perryville, Alaska
- 1.8 74 km ESE of Sand Point, Alaska
- 2.2 120 km ESE of Sand Point, Alaska
- 1.8 53 km SE of Sand Point, Alaska
- 1.8 62 km ESE of Sand Point, Alaska
- 5.5 73 km S of Ivanof Bay, 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.