QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Belfair, WA

No earthquake was likely felt in Belfair in the 24 hours to 8:58 am PST (16:58 UTC). The last one was M 4.2, 10 km (6 mi) SE, at 2:05 pm PDT on 29 September 2026, estimated intensity III (weak) in town; 9,329 felt reports to USGS. Every earthquake near Belfair

This page: a magnitude 1.8 earthquake was recorded 4 km (3 mi) north of Belfair, WA, at 3:00 pm PDT on 15 September 2021 (22:00 UTC), 22 km deep.

USGS: 4 km N of Belfair, Washington

39 km (24 mi) WSW of Seattle, WA · 36 km (23 mi) W of Burien, WA

3:00 pm PDT, Sep 15, 2021 · · 22 km deep · released about 16 lb of TNT

10 km30 km60 km120 km N Kitsap County 21 kmMason County 30 kmThurston County 62 kmJefferson County 63 kmPierce County 70 kmKing County 75 kmIsland County 75 kmGrays Harbor County 86 kmSnohomish County 101 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
3:00 pm PDT on 15 September 2021 ()
Where
4 km (3 mi) north of Belfair, WA · earthquakes near Belfair
Magnitude
M 1.8 (ml)
Depth
22 km below the surface
Felt
no reports yet
Nearest
Kitsap County, 21 km NE
Nearest mapped fault
Tacoma fault, 7 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 614 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 Belfair, 4 km away, the estimate is intensity II (weak). 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.

Earthquakes near other towns within 30 km: Allyn, Navy Yard City, Bethel, Erlands Point-Kitsap Lake, Port Orchard, East Port Orchard.

How big was it?

This earthquake released about 16 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 5.8 930,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 660,000× the energy of this one
  3. Around the size people start to feel M 3.0 59× the energy of this one
  4. This earthquake M 1.8 about 16 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 4.1 on 2017-02-23 — about 2,500 times the energy of this one.

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

  1. 6.8 The 2001 Nisqually, Washington Earthquake · 39 km SSE of this epicentre
  2. 6.7 1 km ENE of Dash Point, Washington · 36 km ESE of this epicentre
  3. 6.1 Puget Sound region, Washington · 11 km SSE of this epicentre
  4. 5.8 Puget Sound area, Washington · 24 km SSW of this epicentre
  5. 5.3 Eastern Olympic Peninsula, Washington · 37 km NNW 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 47.4892, -122.8273. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Kitsap County, WA 21 km (13 mi) NE earthquakes near Kitsap County
Mason County, WA 30 km (19 mi) WSW earthquakes near Mason County
Thurston County, WA 62 km (38 mi) S earthquakes near Thurston County
Jefferson County, WA 63 km (39 mi) NW earthquakes near Jefferson County
Pierce County, WA 70 km (44 mi) SE earthquakes near Pierce County
King County, WA 75 km (46 mi) E earthquakes near King County

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

Aftershocks so far

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

  1. 1.8 5 km SW of Des Moines, Washington
  2. 1.6 Puget Sound region, Washington
  3. 1.6 8 km WSW of Home, Washington
  4. 1.5 7 km WNW of Lofall, Washington
  5. 1.9 7 km SSW of Port Ludlow, Washington
  6. 1.9 7 km WNW of Lofall, Washington
  7. 2.3 5 km WNW of Wauna, Washington
  8. 1.5 8 km WNW of Lofall, Washington
  9. 3.7 7 km WNW of Lofall, Washington
  10. 1.5 5 km W of Gorst, Washington
  11. 1.5 3 km W of Hoodsport, Washington
  12. 1.7 6 km E of Quilcene, Washington
  13. 1.6 5 km SW of Port Ludlow, Washington
  14. 1.8 6 km NNW of Kingston, Washington
  15. 1.5 1 km NNE of Lakewood, Washington

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.