M1.1 explosion 21 km NNE of West Side Highway, Washington, United States
A magnitude 1.1 explosion struck 21 km NNE of West Side Highway, Washington, United States at 16:50 local time (23:50 UTC) on 15 Oct 2026, at a depth of 0 km, according to USGS.
Data: USGS · updated 2026-10-16 17:41 UTC · reviewed
- Magnitude
- 1.1micro
local magnitude (Richter) (ml) - Depth
- -0.5 km
- Status
- Reviewed
- Origin time
- 2026-10-15 23:50:15 UTC
- Local: 15 Oct 2026, 16:50:15 (America/Los Angeles)
- Epicentre
- 46.348° N, 122.804° W
Circles show this event and others within 30 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map
Nearby places
| Place | Distance | Est. shaking |
|---|---|---|
| West Side HighwayWashington, United States · pop. 5,517 | 21 km | INot felt |
| KelsoWashington, United States · pop. 11,901 | 23 km | INot felt |
| LongviewWashington, United States · pop. 36,848 | 25 km | INot felt |
| LaceyWashington, United States · pop. 46,409 | 76 km | INot felt |
| OlympiaWashington, United States · pop. 55,733 | 77 km | INot felt |
| VancouverWashington, United States · pop. 196,442 | 79 km | INot felt |
| PortlandOregon, United States · pop. 652,503 | 93 km | INot felt |
| SeattleWashington, United States · pop. 780,995 | 145 km | INot felt |
Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more. Likely felt out to about 2 km.
Every agency's solution
Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses USGS · UW, which has been reviewed by an analyst.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGS · UWheadlinePacific Northwest Seismic Network via U.S. Geological Survey | 1.1 ml | -0.5 km | 46.35° N, 122.80° W | – | Reviewed |
How big was it?
Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.
It released roughly the energy of 773 g of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 0 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M1.1 releases about 1.6× the energy of M1.0, and its waves are about 1.4× taller on a seismogram. Energy: 773 g of TNT vs 477 g of TNT.
Each square is the energy of one M1.0. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
9 later earthquakes within 30 km; the largest was M1.8 3 h 6 min ago. 1 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M1.1
9 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 151.10 | 0.5 | 18 |
| 273.07 | 0.6 | 18 |
| 273.09 | 0.3 | 17 |
| 285.25 | 1.5 | 0 |
| 334.09 | 1.4 | 0 |
| 389.57 | 1.1 | 18 |
| 479.47 | 0.7 | 17 |
| 502.75 | 1.1 | 0 |
| 669.26 | 1.8 | 22 |
- 1.821 km S of Chehalis, Washington, United States11-12 21:05
- 1.513 km S of Chehalis, Washington, United States10-27 21:05
- 1.420 km NNE of West Side Highway, Washington, United States10-29 21:55
- 1.122 km ENE of West Side Highway, Washington, United States11-01 05:24
- 1.120 km NNE of West Side Highway, Washington, United States11-05 22:35
- 0.723 km ENE of West Side Highway, Washington, United States11-04 23:18
- 0.622 km ENE of West Side Highway, Washington, United States10-27 08:54
- 0.522 km ENE of West Side Highway, Washington, United States10-22 06:56
- 0.323 km ENE of West Side Highway, Washington, United States10-27 08:55
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Reports close 14 days after an earthquake.
Reports on SeismoAtlas
No reports yet.
Event id uw714120722. First recorded here 16 Oct 2026, 17:46:34 UTC. Solutions: USGS · UW (usgs:uw714120722). Cite as: SeismoAtlas, “M1.1 explosion 21 km NNE of West Side Highway, Washington, United States”, https://seismoatlas.com/earthquake/uw714120722-m1-1-explosion-21-km-nne-of-west-side-highway-washington-united-states, data from USGS.
JSON: /api/v1/events/uw714120722. SeismoAtlas is not an official warning service.