QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Nikiski, AK

No earthquake was likely felt in Nikiski in the 24 hours to 9:21 am AKST (18:21 UTC). The last one was M 4.3, 58 km (36 mi) SSE, at 2:30 am AKST on 1 November 2026, estimated intensity II (weak) in town; 115 felt reports to USGS. Every earthquake near Nikiski

This page: a magnitude 1.8 earthquake was recorded 48 km (30 mi) north-northwest of Nikiski, AK, at 9:37 pm AKDT on 28 September 2018 (05:37 UTC), 69 km deep.

USGS: 19 km WNW of Tyonek, Alaska

86 km (54 mi) W of Anchorage, AK

9:37 pm AKDT, Sep 28, 2018 · · 69 km deep · released about 15 lb of TNT

Every earthquake near Nikiski Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Kenai Peninsula Borough 94 kmAnchorage Municipality 119 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
9:37 pm AKDT on 28 September 2018 ()
Where
48 km (30 mi) north-northwest of Nikiski, AK · earthquakes near Nikiski
Magnitude
M 1.8 (ml)
Depth
69 km below the surface
Felt
no reports yet
Nearest
Kenai Peninsula Borough, 94 km SSW
Nearest mapped fault
Granite Point anticline (Cook Inlet folds), 14 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1185 days ago

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

At this magnitude and depth it was probably too small to be felt, even directly above it. In Nikiski, 48 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 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 710,000× the energy of this one
  3. Around the size people start to feel M 3.0 63× the energy of this one
  4. This earthquake M 1.8 about 15 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 5.2 on 2017-05-30 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 Southern Alaska · 20 km E of this epicentre
  2. 6.8 4 km NE of Beluga, Alaska · 26 km ENE of this epicentre
  3. 6.7 6 km WNW of Nikiski, Alaska · 44 km S of this epicentre
  4. 6.4 19 km SSE of Tyonek, Alaska · 34 km SE of this epicentre
  5. 6.0 Southern Alaska · 16 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 61.1095, -151.4900. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Kenai Peninsula Borough, AK 94 km (59 mi) SSW earthquakes near Kenai Peninsula Borough
Anchorage Municipality, AK 119 km (74 mi) E 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. 1.7 50 km WNW of Beluga, Alaska
  2. 1.7 30 km WNW of Beluga, Alaska
  3. 1.5 45 km NW of Nikiski, Alaska
  4. 1.6 9 km SW of Tyonek, Alaska
  5. 1.7 2 km ENE of Tyonek, Alaska
  6. 2.2 13 km SE of Tyonek, Alaska
  7. 1.6 4 km NNW of Tyonek, Alaska
  8. 1.7 32 km W of Tyonek, Alaska
  9. 2.7 47 km NNW of Beluga, Alaska
  10. 1.5 2 km NNW of Beluga, Alaska
  11. 1.7 2 km NNE of Beluga, Alaska
  12. 1.8 21 km WSW of Point Possession, Alaska
  13. 1.8 10 km S of Tyonek, Alaska
  14. 1.7 14 km NW of Beluga, Alaska
  15. 1.6 26 km SW of Tyonek, 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.