explosion · reviewed by a seismologist
M 1.9ml
Earthquake near Graham, WA
No earthquake was likely felt in Graham in the 24 hours to 5:59 am PST (13:59 UTC). The last one was M 1.6, 5 km (3 mi) SE, at 11:47 am PST on 9 November 2026, estimated intensity II (weak) in town. Every earthquake near Graham
No: USGS classifies this as a explosion, not an earthquake. A magnitude 1.9 explosion was recorded 11 km (7 mi) southeast of Graham, WA, at 1:36 pm PDT on 28 September 2021 (20:36 UTC), less than 1 km deep.
USGS: 2 km SSE of Kapowsin, Washington
73 km (45 mi) S of Seattle, WA · 32 km (20 mi) SE of Lakewood, WA
- When
- 1:36 pm PDT on 28 September 2021 ()
- Where
- 11 km (7 mi) southeast of Graham, WA · earthquakes near Graham
- Magnitude
- M 1.9 (ml)
- Depth
- -0.3 km below the surface
- Felt
- no reports yet
- Nearest
- Pierce County, 10 km NNE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 614 days ago
Earthquake alerts for Graham, WA
Get a notification in this browser when USGS records an earthquake near Graham, WA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 15 km (9 mi) from the epicentre. In Graham, 11 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.
Likely felt in: Graham 11 km, intensity II. Estimated for each town centre; each link is that town's own record.
USGS catalogues this as explosion, not an earthquake.
How big was it?
This earthquake released about 22 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 5.8 680,000× the energy of this one
- Magna, Utah 2020 M 5.7 480,000× the energy of this one
- Around the size people start to feel M 3.0 43× the energy of this one
- This earthquake M 1.9 about 22 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 lists 4 earthquakes of M5 or more within 50 km:
- 6.8 The 2001 Nisqually, Washington Earthquake · 44 km WNW of this epicentre
- 6.7 4 km WNW of Roy, Washington · 30 km W of this epicentre
- 6.7 1 km ENE of Dash Point, Washington · 42 km NNW of this epicentre
- 5.0 3 km WSW of Des Moines, Washington · 48 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 46.9687, -122.2095. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Pierce County, WA | 10 km (6 mi) | NNE | earthquakes near Pierce County |
| Lewis County, WA | 45 km (28 mi) | SSW | earthquakes near Lewis County |
| Thurston County, WA | 47 km (29 mi) | W | earthquakes near Thurston County |
| King County, WA | 65 km (40 mi) | NNE | earthquakes near King County |
| Kitsap County, WA | 82 km (51 mi) | NNW | earthquakes near Kitsap County |
| Mason County, WA | 84 km (52 mi) | WNW | earthquakes near Mason County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
50 earthquakes have been recorded within 50 km since this one.
- 1.6 5 km WNW of Ashford, Washington
- 1.6 6 km ENE of Elbe, Washington
- 1.5 24 km ENE of Ashford, Washington
- 1.8 1 km NNE of Kapowsin, Washington
- 1.5 25 km ENE of Ashford, Washington
- 2.1 24 km ENE of Ashford, Washington
- 2.0 7 km NE of Ashford, Washington
- 1.6 18 km N of Mossyrock, Washington
- 2.1 7 km NE of Ashford, Washington
- 1.6 1 km WNW of Kapowsin, Washington
- 2.1 5 km SW of Black Diamond, Washington
- 1.9 10 km ENE of Ashford, Washington
- 1.7 2 km WNW of Kapowsin, Washington
- 1.6 16 km NNE of Ashford, Washington
- 2.3 15 km NNE of Ashford, 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
- 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.