Earthquake · reviewed by a seismologist
M 3.2ml
south of Alaska
Yes. A magnitude 3.2 earthquake was recorded south of Alaska at 05:04 UTC on 2021-07-31, 36 km deep.
- When
- Magnitude
- M 3.2 (ml)
- Depth
- 36 km below the surface
- Felt
- no reports yet
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1857 days ago
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. 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 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.
- Northridge, California 1994 M 6.7 180,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 7,900× the energy of this one
- Magna, Utah 2020 M 5.7 5,600× the energy of this one
- This earthquake M 3.2 about 1,900 lb of TNT
- 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 4.8 on 2021-07-29 — about 250 times the energy of this one.
Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:
- 7.0 164 km SE of Chignik, Alaska · 47 km WSW of this epicentre
- 6.9 171 km SW of Akhiok, Alaska · 31 km NNW of this epicentre
- 6.2 148 km SSW of Akhiok, Alaska · 46 km NE of this epicentre
- 6.1 210 km SE of Chignik, Alaska · 31 km S of this epicentre
- 6.0 223 km SSW of Akhiok, Alaska · 41 km SSE 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 55.4507, -155.7146. Map © OpenStreetMap contributors.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 2.4 182 km ESE of Chignik, Alaska
- 1.9 167 km SW of Akhiok, Alaska
- 2.4 165 km SSW of Akhiok, Alaska
- 3.1 south of Alaska
- 2.7 168 km ESE of Chignik, Alaska
- 2.0 157 km SW of Akhiok, Alaska
- 2.3 160 km SSW of Akhiok, Alaska
- 2.5 147 km SW of Akhiok, Alaska
- 2.3 167 km SW of Akhiok, Alaska
- 2.9 167 km SW of Akhiok, Alaska
- 2.2 161 km SW of Akhiok, Alaska
- 3.0 190 km SE of Chignik, Alaska
- 1.9 165 km SE of Chignik, Alaska
- 2.6 177 km SSW of Akhiok, Alaska
- 2.8 199 km SE of Chignik, 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.