QuakeIndex

Earthquake · reviewed by a seismologist

M 4.9ml

56 km SSW of Nanwalek, Alaska

Yes. A magnitude 4.9 earthquake was recorded 56 km SSW of Nanwalek, Alaska, at 12:17 am AKDT on 29 April 2016 (08:17 UTC), 55 km deep. 12 people have reported feeling it to USGS.

· 55 km deep · released about 340 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 4.9 (ml)
Depth
55 km below the surface
Felt
12 reports · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
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 1200 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 173 km (107 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 340 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 500× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 22× the energy of this one
  3. Magna, Utah 2020 M 5.7 16× the energy of this one
  4. This earthquake M 4.9 about 340 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 710× 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. No other earthquake of M4 or more has been recorded this close in that time.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.0 61 km WSW of Nanwalek, Alaska · 41 km NW of this epicentre
  2. 5.8 63 km WSW of Nanwalek, Alaska · 37 km WNW of this epicentre
  3. 5.5 73 km WSW of Nanwalek, Alaska · 40 km WNW of this epicentre
  4. 5.3 41 km SSW of Nanwalek, Alaska · 16 km NE of this epicentre
  5. 5.2 52 km SW of Nanwalek, Alaska · 11 km NW 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 58.8989, -152.3384. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.5 41 km SSW of Nanwalek, Alaska
  2. 1.7 27 km W of Nanwalek, Alaska
  3. 2.1 8 km SSW of Nanwalek, Alaska
  4. 1.6 76 km SW of Nanwalek, Alaska
  5. 1.6 65 km SW of Nanwalek, Alaska
  6. 1.7 45 km SW of Nanwalek, Alaska
  7. 1.7 59 km WSW of Nanwalek, Alaska
  8. 2.7 53 km SSW of Nanwalek, Alaska
  9. 1.5 7 km S of Nanwalek, Alaska
  10. 1.6 50 km SW of Nanwalek, Alaska
  11. 1.5 68 km N of Aleneva, Alaska
  12. 1.6 42 km WSW of Nanwalek, Alaska
  13. 1.5 Southern Alaska
  14. 2.3 39 km WSW of Nanwalek, Alaska
  15. 1.6 38 km WSW of Nanwalek, 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.