QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8mwr

157 km E of McCarthy, Alaska

Yes. A magnitude 4.8 earthquake was recorded 157 km E of McCarthy, Alaska at 20:22 UTC on 2023-08-06, 3.0 km deep. 7 people have reported feeling it to USGS.

· 3.0 km deep · released about 240 tons of TNT

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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 4.8 (mwr)
Depth
3.0 km below the surface
Felt
7 reports · strongest reported intensity III
Measured shaking
intensity VI (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1123 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 170 km (106 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 240 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 710× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 32× the energy of this one
  3. Magna, Utah 2020 M 5.7 22× the energy of this one
  4. This earthquake M 4.8 about 240 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 500× 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. The previous largest was M 4.2 on 2022-10-06.

Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.7 152 km E of McCarthy, Alaska · 5 km W of this epicentre
  2. 5.4 140 km SSE of Alcan Border, Alaska · 22 km NW of this epicentre
  3. 5.4 136 km SSE of Alcan Border, Alaska · 23 km NNW of this epicentre
  4. 5.3 136 km E of McCarthy, Alaska · 24 km WNW of this epicentre
  5. 5.2 130 km SSE of Alcan Border, Alaska · 29 km NNW 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 61.3461, -139.9737. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.8 151 km ESE of McCarthy, Alaska
  2. 1.6 156 km SSE of Alcan Border, Alaska
  3. 1.5 153 km E of McCarthy, Alaska
  4. 3.3 156 km E of McCarthy, Alaska
  5. 1.8 143 km E of McCarthy, Alaska
  6. 1.5 152 km SSE of Alcan Border, Alaska
  7. 2.4 151 km SSE of Alcan Border, Alaska
  8. 1.5 166 km E of McCarthy, Alaska
  9. 1.6 158 km ESE of McCarthy, Alaska
  10. 1.5 158 km ESE of McCarthy, Alaska
  11. 1.5 157 km E of McCarthy, Alaska
  12. 1.6 153 km ESE of McCarthy, Alaska
  13. 1.9 138 km E of McCarthy, Alaska
  14. 1.6 159 km ESE of McCarthy, Alaska
  15. 1.8 154 km E of McCarthy, 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.