QuakeIndex

Earthquake · reviewed by a seismologist

M 5.4mww

116 km S of Unalaska, Alaska

Yes. A magnitude 5.4 earthquake was recorded 116 km S of Unalaska, Alaska, at 11:46 am AKDT on 26 July 2016 (19:46 UTC), 17 km deep. 1 person has reported feeling it to USGS.

· 17 km deep · released about 1.9 kilotons 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 5.4 (mww)
Depth
17 km below the surface
Felt
1 report · strongest reported intensity I
Measured shaking
intensity IV (ShakeMap)
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1199 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.6 on 2016-07-10.

Before 2016, the USGS record lists 47 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 127 km E of Nikolski, Alaska · 17 km WSW of this epicentre
  2. 6.4 118 km E of Nikolski, Alaska · 25 km WSW of this epicentre
  3. 6.4 123 km ESE of Nikolski, Alaska · 34 km SW of this epicentre
  4. 6.3 136 km ESE of Nikolski, Alaska · 23 km SSW of this epicentre
  5. 6.3 Fox Islands, Aleutian Islands, Alaska · 39 km SW 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 52.8329, -166.7743. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 134 km S of Unalaska, Alaska
  2. 1.7 129 km S of Unalaska, Alaska
  3. 2.5 128 km S of Unalaska, Alaska
  4. 1.9 119 km S of Unalaska, Alaska
  5. 2.1 124 km ESE of Nikolski, Alaska
  6. 2.0 Fox Islands, Aleutian Islands, Alaska
  7. 2.3 125 km S of Unalaska, Alaska
  8. 2.1 129 km ESE of Nikolski, Alaska
  9. 2.2 132 km ESE of Nikolski, Alaska
  10. 2.0 126 km S of Unalaska, Alaska
  11. 3.2 Fox Islands, Aleutian Islands, Alaska
  12. 2.0 128 km S of Unalaska, Alaska
  13. 2.4 118 km SSW of Unalaska, Alaska
  14. 2.0 119 km S of Unalaska, Alaska
  15. 2.9 119 km S 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.