QuakeIndex

Earthquake · reviewed by a seismologist

M 4.3mb

180 km S of Sand Point, Alaska

Yes. A magnitude 4.3 earthquake was recorded 180 km S of Sand Point, Alaska at 03:19 UTC on 2020-10-31, 18 km deep.

· 18 km deep · released about 43 tons of TNT

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10 km30 km60 km120 km N
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
Magnitude
M 4.3 (mb)
Depth
18 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 13 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 2125 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 120 km (75 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 43 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.3 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 4,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 180× the energy of this one
  3. Magna, Utah 2020 M 5.7 130× the energy of this one
  4. This earthquake M 4.3 about 43 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 89× 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 5.2 on 2016-11-14 — about 22 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.7 208 km SSE of Sand Point, Alaska · 29 km SSE of this epicentre
  2. 5.0 188 km SSE of Sand Point, Alaska · 9 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 53.7408, -159.9788. Map © OpenStreetMap contributors.

Aftershocks so far

52 earthquakes have been recorded within 50 km since this one.

  1. 2.7 south of Alaska
  2. 2.7 141 km SSE of Sand Point, Alaska
  3. 2.5 207 km S of Sand Point, Alaska
  4. 2.7 185 km S of Sand Point, Alaska
  5. 2.8 208 km S of Sand Point, Alaska
  6. 3.2 154 km SSE of Sand Point, Alaska
  7. 2.5 219 km S of Sand Point, Alaska
  8. 2.7 134 km SSE of Sand Point, Alaska
  9. 3.1 168 km SSE of Sand Point, Alaska
  10. 3.1 222 km S of Sand Point, Alaska
  11. 3.5 217 km S of Sand Point, Alaska
  12. 3.0 207 km S of Sand Point, Alaska
  13. 4.4 145 km SSE of Sand Point, Alaska
  14. 2.9 143 km SSE of Sand Point, Alaska
  15. 5.1 141 km SSE of Sand Point, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.