explosion · reviewed by a seismologist
M 1.8ml
Earthquake near Olympia, WA
No earthquake was likely felt in Olympia in the 24 hours to 5:03 am PST (13:03 UTC). The last one was M 4.2, 42 km (26 mi) NNE, at 2:05 pm PDT on 29 September 2026, estimated intensity III (weak) in town; 9,329 felt reports to USGS. Every earthquake near Olympia
No: USGS classifies this as a explosion, not an earthquake. A magnitude 1.8 explosion was recorded 18 km (11 mi) west-northwest of Olympia, WA, at 11:59 am PDT on 18 September 2023 (18:59 UTC), less than 1 km deep.
USGS: Olympic Peninsula, Washington
80 km (50 mi) SW of Seattle, WA · 19 km (12 mi) WNW of Olympia, WA
- When
- 11:59 am PDT on 18 September 2023 ()
- Where
- 18 km (11 mi) west-northwest of Olympia, WA · earthquakes near Olympia
- Magnitude
- M 1.8 (ml)
- Depth
- -0.2 km below the surface
- Felt
- no reports yet
- Nearest
- Mason County, 27 km N
- Nearest mapped fault
- Olympia structure, 6 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 1136 days ago
Earthquake alerts for Olympia, WA
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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 13 km (8 mi) from the epicentre. In Olympia, 18 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: Shelton 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 13 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.
- Mineral, Virginia 2011 M 5.8 1,100,000× the energy of this one
- Magna, Utah 2020 M 5.7 810,000× the energy of this one
- Around the size people start to feel M 3.0 72× the energy of this one
- This earthquake M 1.8 about 13 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 3,100 times the energy of this one.
Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:
- 6.8 The 2001 Nisqually, Washington Earthquake · 30 km E of this epicentre
- 6.7 4 km WNW of Roy, Washington · 41 km ESE of this epicentre
- 6.1 Puget Sound region, Washington · 42 km NE of this epicentre
- 5.8 Puget Sound area, Washington · 25 km NE of this epicentre
- 5.8 8 km N of Satsop, Washington · 27 km W 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 47.1145, -123.1155. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Mason County, WA | 27 km (17 mi) | N | earthquakes near Mason County |
| Thurston County, WA | 29 km (18 mi) | SE | earthquakes near Thurston County |
| Grays Harbor County, WA | 54 km (33 mi) | W | earthquakes near Grays Harbor County |
| Kitsap County, WA | 68 km (42 mi) | NNE | earthquakes near Kitsap County |
| Pierce County, WA | 73 km (45 mi) | E | earthquakes near Pierce County |
| Pacific County, WA | 80 km (50 mi) | SW | earthquakes near Pacific County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
46 earthquakes have been recorded within 50 km since this one.
- 1.5 17 km NNW of Pe Ell, Washington
- 2.1 2 km ENE of Home, Washington
- 1.6 3 km SSW of Shelton, Washington
- 1.6 15 km N of Satsop, Washington
- 1.6 24 km ESE of Neilton, Washington
- 1.7 9 km ENE of McCleary, Washington
- 1.6 7 km SSW of Shelton, Washington
- 1.6 6 km S of Gorst, Washington
- 1.6 2 km N of McCleary, Washington
- 1.9 7 km W of Shelton, Washington
- 1.5 17 km SSE of Montesano, Washington
- 1.6 11 km S of Shelton, Washington
- 2.2 7 km NNW of Hoodsport, Washington
- 2.7 7 km NNW of Montesano, Washington
- 1.6 11 km S of Shelton, 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.