Earthquake near Deltana, AK

USGS: 17 km ESE of Healy Lake, Alaska

11:57 pm AKDT, Aug 20, 2021 · 2021-08-21 07:57 UTC · 13 km deep · released about 21 lb 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: 11:57 pm AKDT on 20 August 2021 (2021-08-21 07:57 UTC)
Where: 40 km (25 mi) E of Deltana, AK · earthquakes near Deltana
Magnitude: M 1.9 (ml)
Depth: 13 km below the surface
Felt: no reports yet
Nearest: Southeast Fairbanks Census Area, 58 km E
Nearest mapped fault: Dot ''T'' Johnson fault (Northern Foothills fold and thrust belt), 22 km from its surface trace — near is not the same as on
Status: Reviewed by a seismologist

USGS · last changed by USGS 1858 days ago · we first saw it 1858 days ago

A magnitude 1.9 earthquake was recorded 40 km (25 mi) E of Deltana, AK, at 11:57 pm AKDT on 20 August 2021 (07:57 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 21 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

Mineral, Virginia 2011 M 5.8 710,000× the energy of this one
Magna, Utah 2020 M 5.7 500,000× the energy of this one
Around the size people start to feel M 3.0 45× the energy of this one
This earthquake M 1.9 about 21 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.

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

Map loads when it scrolls into view

Epicentre 63.9042, -144.4062. Map © OpenStreetMap contributors.

Nearby places

Place	Distance	Direction from the epicentre
Southeast Fairbanks Census Area, AK	58 km (36 mi)	E	earthquakes near Southeast Fairbanks Census Area
Fairbanks North Star Borough, AK	132 km (82 mi)	NW	earthquakes near Fairbanks North Star Borough

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

Aftershocks so far

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

1.9 8 km ESE of Dry Creek, Alaska 07:05 UTC
1.5 18 km SSW of Dry Creek, Alaska 07:58 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 02:11 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

The official USGS event page — the source of record for every value above
Did you feel it? Report it to USGS — reports go to USGS, not to us
ShakeMap for this event, when USGS has produced one

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.