QuakeIndex

Earthquake · reviewed by a seismologist

M 6.9mww

112 km E of Chignik, Alaska

Yes. A magnitude 6.9 earthquake was recorded 112 km E of Chignik, Alaska at 09:10 UTC on 2021-10-11, 52 km deep. 320 people have reported feeling it to USGS.

· 52 km deep · released about 340 kilotons 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 6.9 (mww)
Depth
52 km below the surface
Felt
320 reports · strongest reported intensity VIII
Measured shaking
intensity VI (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 325 days ago

This was a strong earthquake. Damage is likely near the epicentre and it is felt over a wide area.

At this magnitude and depth, people at rest would likely notice it out to about 553 km (344 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 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 7.9 would have released about 32 times as much.

  1. Tōhoku, Japan 2011 M 9.1 2,000× the energy of this one
  2. San Francisco 1906 M 7.9 32× the energy of this one
  3. Ridgecrest, California 2019 M 7.1 2× the energy of this one
  4. This earthquake M 6.9 about 340 kilotons of TNT
  5. Northridge, California 1994 M 6.7 this one released 2× more
  6. Mineral, Virginia 2011 M 5.8 this one released 45× 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 4.8 on 2021-10-01.

Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 117 km SSE of Ugashik, Alaska · 34 km NNE of this epicentre
  2. 6.4 77 km ESE of Chignik, Alaska · 42 km WSW of this epicentre
  3. 6.4 104 km SSE of Ugashik, Alaska · 40 km NNW of this epicentre
  4. 6.3 112 km E of Chignik, Alaska · 12 km S of this epicentre
  5. 6.1 132 km E of Chignik, Alaska · 22 km ESE 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 56.2954, -156.5810. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.7 122 km E of Chignik, Alaska
  2. 2.4 117 km E of Chignik, Alaska
  3. 4.1 114 km E of Chignik, Alaska
  4. 3.1 115 km E of Chignik, Alaska
  5. 2.3 116 km E of Chignik, Alaska
  6. 2.6 121 km E of Chignik, Alaska
  7. 2.4 113 km E of Chignik, Alaska
  8. 2.3 136 km E of Chignik, Alaska
  9. 3.6 115 km E of Chignik, Alaska
  10. 2.2 114 km E of Chignik, Alaska
  11. 2.4 117 km E of Chignik, Alaska
  12. 2.2 113 km E of Chignik, Alaska
  13. 2.3 115 km E of Chignik, Alaska
  14. 2.5 113 km E of Chignik, Alaska
  15. 2.5 Alaska Peninsula

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.