explosion · reviewed by a seismologist
M 1.6md
Earthquake near Monroe, WA
No earthquake was likely felt in Monroe in the 24 hours to 10:47 am PST (18:47 UTC). The last one was M 4.2, 76 km (47 mi) SW, at 2:05 pm PDT on 29 September 2026, estimated intensity II (weak) in town; 9,329 felt reports to USGS. Every earthquake near Monroe
No: USGS classifies this as a explosion, not an earthquake. A magnitude 1.6 explosion was recorded 3 km (2 mi) south of Monroe, WA, at 3:05 pm PDT on 21 September 2021 (22:05 UTC), less than 1 km deep.
USGS: 2 km S of Monroe, Washington
37 km (23 mi) NE of Seattle, WA · 19 km (12 mi) ENE of Bothell, WA
- When
- 3:05 pm PDT on 21 September 2021 ()
- Where
- 3 km (2 mi) south of Monroe, WA · earthquakes near Monroe
- Magnitude
- M 1.6 (md)
- Depth
- -0.4 km below the surface
- Felt
- no reports yet
- Nearest
- Snohomish County, 29 km NNE
- Nearest mapped fault
- Southern Whidbey Island fault, 2 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 1877 days ago
Earthquake alerts for Monroe, WA
Get a notification in this browser when USGS records an earthquake near Monroe, 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 12 km (7 mi) from the epicentre. In Monroe, 3 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: Monroe 3 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 8.4 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,800,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,300,000× the energy of this one
- Around the size people start to feel M 3.0 110× the energy of this one
- This earthquake M 1.6 about 8.4 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 4.6 on 2019-07-12 — about 27,000 times the energy of this one.
Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:
- 5.4 8 km NNE of Lake Marcel-Stillwater, Washington · 10 km SE of this epicentre
- 5.2 9 km NE of Lake Marcel-Stillwater, Washington · 13 km SE of this epicentre
- 5.0 4 km ENE of Machias, Washington · 19 km N 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 47.8292, -121.9638. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Snohomish County, WA | 29 km (18 mi) | NNE | earthquakes near Snohomish County |
| King County, WA | 39 km (24 mi) | SSE | earthquakes near King County |
| Kitsap County, WA | 55 km (34 mi) | WSW | earthquakes near Kitsap County |
| Island County, WA | 64 km (40 mi) | NW | earthquakes near Island County |
| Skagit County, WA | 75 km (46 mi) | N | earthquakes near Skagit County |
| Pierce County, WA | 88 km (54 mi) | S | earthquakes near Pierce County |
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.
- 1.5 0 km SSE of Wilderness Rim, Washington
- 1.5 4 km SSW of Clinton, Washington
- 1.6 2 km E of Granite Falls, Washington
- 1.7 4 km SW of White Center, Washington
- 1.8 3 km WSW of White Center, Washington
- 1.8 3 km NNW of Picnic Point, Washington
- 1.6 4 km NE of Granite Falls, Washington
- 1.6 6 km SW of Sultan, Washington
- 1.6 Puget Sound region, Washington
- 1.5 Washington
- 1.5 Washington
- 1.8 2 km SSE of Lake Forest Park, Washington
- 2.0 Washington
- 1.7 4 km E of Granite Falls, Washington
- 1.9 4 km E of Granite Falls, 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.