QuakeIndex

Earthquake · reviewed by a seismologist

M 4.6mb

135 km S of Unalaska, Alaska

Yes. A magnitude 4.6 earthquake was recorded 135 km S of Unalaska, Alaska, at 7:16 pm AKDT on 8 July 2018 (03:16 UTC), 32 km deep.

· 32 km deep · released about 120 tons of TNT

Felt it? Tell USGS Check my area
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 4.6 (mb)
Depth
32 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 326 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 146 km (91 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 120 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,400× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 63× the energy of this one
  3. Magna, Utah 2020 M 5.7 45× the energy of this one
  4. This earthquake M 4.6 about 120 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 250× 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 5.9 on 2017-05-24 — about 89 times the energy of this one.

Before 2016, the USGS record lists 38 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 183 km S of Unalaska, Alaska · 48 km S of this epicentre
  2. 6.5 127 km E of Nikolski, Alaska · 36 km WNW of this epicentre
  3. 6.4 118 km E of Nikolski, Alaska · 45 km WNW of this epicentre
  4. 6.4 123 km ESE of Nikolski, Alaska · 43 km W of this epicentre
  5. 6.3 136 km ESE of Nikolski, Alaska · 29 km W 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 52.6559, -166.4824. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 4.0 135 km ESE of Nikolski, Alaska
  2. 3.1 149 km ESE of Nikolski, Alaska
  3. 4.0 154 km ESE of Nikolski, Alaska
  4. 3.5 151 km ESE of Nikolski, Alaska
  5. 5.3 139 km ESE of Nikolski, Alaska
  6. 2.9 142 km ESE of Nikolski, Alaska
  7. 2.1 132 km S of Unalaska, Alaska
  8. 2.1 137 km ESE of Nikolski, Alaska
  9. 2.4 97 km SSW of Unalaska, Alaska
  10. 1.9 129 km S of Unalaska, Alaska
  11. 2.3 111 km S of Unalaska, Alaska
  12. 2.5 111 km S of Unalaska, Alaska
  13. 1.9 131 km S of Unalaska, Alaska
  14. 1.9 100 km SSW of Unalaska, Alaska
  15. 1.9 114 km SSW of Unalaska, 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.