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M1.3 explosion 61 km SSE of Graham, Washington, United States

A magnitude 1.3 explosion struck 61 km SSE of Graham, Washington, United States at 15:10 local time (22:10 UTC) on 27 Oct 2026, at a depth of -1 km, according to USGS.

Data: USGS · updated 2026-10-28 17:53 UTC · reviewed

Magnitude
1.3micro
local magnitude (Richter) (ml)
Depth
-1 km
Status
Reviewed
Origin time
2026-10-27 22:10:23 UTC
Local: 27 Oct 2026, 15:10:23 (America/Los Angeles)
Epicentre
46.535° N, 122.016° 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

Distance and estimated shaking at nearby places
PlaceDistanceEst. shaking
GrahamWashington, United States · pop. 23,49161 kmINot felt
YelmWashington, United States · pop. 8,43464 kmINot felt
South HillWashington, United States · pop. 52,43170 kmINot felt
SpanawayWashington, United States · pop. 27,22770 kmINot felt
PuyallupWashington, United States · pop. 39,65976 kmINot felt
SeattleWashington, United States · pop. 780,995122 kmINot felt
PortlandOregon, United States · pop. 652,503124 kmINot felt
VictoriaBritish Columbia, Canada · pop. 289,625234 kmINot 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 3 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.

AgencyMagnitudeDepthEpicentreTime offsetStatus
USGS · UWheadlinePacific Northwest Seismic Network via U.S. Geological Survey1.3 ml-1 km46.54° N, 122.02° W–Reviewed

How big was it?

Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.

It released roughly the energy of 1 kg 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 -1 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.

M1.3 releases about 2.8× the energy of M1.0, and its waves are about 2× taller on a seismogram. Energy: 1 kg 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

18 later earthquakes within 30 km; the largest was M1.8 5 days ago. 4 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.

Aftershocks

Mainshock M1.3

18 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).

Aftershocks
Time after mainshock (hours)MagnitudeDepth (km)
28.050.86
36.590.88
50.130.96
67.190.83
67.371.64
142.330.23
182.160.07
185.390.85
191.080.65
207.820.74
261.791.86
266.961.66
308.731.47
314.730.74
317.660.86
332.400.22
375.041.04
385.160.811
  1. 1.840 km SSE of Graham, Washington, United States11-07 19:57
  2. 1.639 km SSE of Graham, Washington, United States10-30 17:32
  3. 1.639 km SSE of Graham, Washington, United States11-08 01:07
  4. 1.465 km SE of Graham, Washington, United States11-09 18:54
  5. 1.040 km SSE of Graham, Washington, United States11-12 13:12
  6. 0.949 km SE of Graham, Washington, United States10-30 00:18
  7. 0.840 km SSE of Graham, Washington, United States11-10 03:50
  8. 0.864 km SE of Graham, Washington, United States11-12 23:19
  9. 0.857 km ESE of Chehalis, Washington, United States10-29 10:46
  10. 0.839 km SSE of Graham, Washington, United States10-30 17:21
  11. 0.840 km SSE of Graham, Washington, United States10-29 02:13
  12. 0.852 km SSE of Graham, Washington, United States11-04 15:34
  13. 0.740 km SSE of Graham, Washington, United States11-05 13:59
  14. 0.739 km SSE of Graham, Washington, United States11-10 00:54
  15. 0.640 km SSE of Graham, Washington, United States11-04 21:15
  16. 0.249 km SE of Graham, Washington, United States11-02 20:30
  17. 0.245 km SSE of Orting, Washington, United States11-10 18:34
  18. 0.042 km SE of Graham, Washington, United States11-04 12:19

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 uw714130481. First recorded here 28 Oct 2026, 17:54:35 UTC. Solutions: USGS · UW (usgs:uw714130481). Cite as: SeismoAtlas, “M1.3 explosion 61 km SSE of Graham, Washington, United States”, https://seismoatlas.com/earthquake/uw714130481-m1-3-explosion-61-km-sse-of-graham-washington-united-states, data from USGS.

JSON: /api/v1/events/uw714130481. SeismoAtlas is not an official warning service.