QuakeIndex

Earthquake · reviewed by a seismologist

M 5.4mww

219 km S of Sand Point, Alaska

Yes. A magnitude 5.4 earthquake was recorded 219 km S of Sand Point, Alaska at 10:02 UTC on 2021-06-18, 8.0 km deep. 1 person has reported feeling it to USGS.

· 8.0 km deep · released about 1.9 kilotons 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 5.4 (mww)
Depth
8.0 km below the surface
Felt
1 report · strongest reported intensity I
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Nearest mapped fault
Alaska-Aleutian subduction zone, 24 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 326 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 246 km (153 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 1.9 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 89× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4× the energy of this one
  3. Magna, Utah 2020 M 5.7 2.8× the energy of this one
  4. This earthquake M 5.4 about 1.9 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 4,000× 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 5.5 on 2020-07-05 — about 1.4 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 5.7 208 km SSE of Sand Point, Alaska · 38 km ENE of this epicentre
  2. 5.5 241 km S of Sand Point, Alaska · 22 km S of this epicentre
  3. 5.5 233 km S of Sand Point, Alaska · 23 km ESE of this epicentre
  4. 5.3 232 km SSE of King Cove, Alaska · 27 km SW of this epicentre
  5. 5.0 188 km SSE of Sand Point, Alaska · 45 km NE 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 53.3650, -160.2941. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 206 km SSE of Sand Point, Alaska
  2. 3.2 231 km S of Sand Point, Alaska
  3. 2.3 206 km S of Sand Point, Alaska
  4. 2.8 229 km SSE of King Cove, Alaska
  5. 2.9 235 km S of Sand Point, Alaska
  6. 2.6 218 km S of Sand Point, Alaska
  7. 3.2 220 km S of Sand Point, Alaska
  8. 2.8 223 km S of Sand Point, Alaska
  9. 2.6 226 km S of Sand Point, Alaska
  10. 2.4 226 km S of Sand Point, Alaska
  11. 3.4 193 km SSE of King Cove, Alaska
  12. 2.8 239 km S of Sand Point, Alaska
  13. 3.5 223 km S of Sand Point, Alaska
  14. 2.9 205 km SSE of King Cove, Alaska
  15. 3.0 223 km S 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.