QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7ml

Earthquake near Girdwood, AK

No earthquake was likely felt in Girdwood in the 24 hours to 8:16 am AKST (17:16 UTC). The last one was M 1.8, 8 km (5 mi) SE, at 10:01 am AKDT on 19 October 2026, estimated intensity II (weak) in town. Every earthquake near Girdwood

This page: a magnitude 1.7 earthquake was recorded 33 km (20 mi) south-southwest of Girdwood, AK, at 2:47 am AKDT on 23 April 2018 (10:47 UTC), 10 km deep.

USGS: 21 km NNW of Moose Pass, Alaska

64 km (40 mi) SSE of Anchorage, AK

2:47 am AKDT, Apr 23, 2018 · · 10 km deep · released about 11 lb of TNT

Every earthquake near Girdwood Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Anchorage Municipality 56 km
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
2:47 am AKDT on 23 April 2018 ()
Where
33 km (20 mi) south-southwest of Girdwood, AK · earthquakes near Girdwood
Magnitude
M 1.7 (ml)
Depth
10 km below the surface
Felt
no reports yet
Nearest
Anchorage Municipality, 56 km N
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1187 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 7 km (4 mi) from the epicentre. In Girdwood, 33 km away, the estimate is intensity I (not felt). 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 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
  3. Around the size people start to feel M 3.0 89× the energy of this one
  4. This earthquake M 1.7 about 11 lb of TNT

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 4.0 on 2016-10-02 — about 2,800 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 5.7 13 km S of Girdwood, Alaska · 21 km NE of this epicentre
  2. 5.6 17 km W of Whittier, Alaska · 26 km ENE of this epicentre
  3. 5.3 16 km WSW of Whittier, Alaska · 26 km ENE of this epicentre
  4. 5.1 16 km WNW of Hope, Alaska · 42 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 60.6807, -149.4496. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Anchorage Municipality, AK 56 km (35 mi) N earthquakes near Anchorage Municipality

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 2.4 24 km NNE of Cooper Landing, Alaska
  2. 1.8 7 km SSW of Cooper Landing, Alaska
  3. 2.0 12 km NE of Moose Pass, Alaska
  4. 1.5 6 km W of Hope, Alaska
  5. 2.3 7 km W of Cooper Landing, Alaska
  6. 1.9 3 km NE of Hope, Alaska
  7. 2.0 10 km WNW of Moose Pass, Alaska
  8. 1.5 15 km NNW of Hope, Alaska
  9. 1.9 16 km NE of Moose Pass, Alaska
  10. 1.8 8 km NE of Girdwood, Alaska
  11. 1.7 5 km NNE of Sunrise, Alaska
  12. 1.6 16 km W of Hope, Alaska
  13. 1.6 26 km NNE of Moose Pass, Alaska
  14. 1.7 7 km NE of Girdwood, Alaska
  15. 2.2 7 km ENE of Sunrise, 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.