M2.9 Earthquake 8 km NNE of Hamilton, Washington — August 28, 2021
2021-08-28 21:59:07 UTC (2021-08-28) · approx. 1:59 PM UTC-8 local
Felt by 29 people across nearby locations.
On August 28, 2021 at 21:59 UTC, a magnitude 2.9 shallow crustal earthquake struck 8 km NNE of Hamilton, Washington, at a depth of 0.9 km and coordinates 48.5952°, -121.9495°. The earthquake was reported felt by 29 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 2.6 (weak). This earthquake was detected by 25 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 139, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 2.9 releases seismic energy equivalent to roughly 374 kg of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 63 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Washington, a region characterized by the Cascadia Subduction Zone, where the Juan de Fuca Plate subducts beneath North America and is capable of producing M9+ megathrust earthquakes. The nearest mapped fault system is the Cascadia Subduction Zone. View all earthquakes in Washington.
Learn more: Cascadia Subduction Zone · Magnitude scale · Aftershock sequences
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 29 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-121.9495°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 2.9 earthquake near Hamilton, Washington?
The magnitude 2.9 earthquake that struck 8 km NNE of Hamilton, Washington on August 28, 2021 at 21:59 UTC had a depth of 0.9 km. It was felt by 29 people with maximum shaking intensity of MMI 2.6 (weak). For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 48.5952°, -121.9495°, which is 8 km NNE of Hamilton, Washington. View all earthquakes in Washington.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 2.9 earthquakes can continue for several days and gradually diminish over time.
Has Washington had earthquakes this big before?
The largest recorded earthquake in Washington was the M7.4 offshore earthquake of April 13, 1949. Today's magnitude 2.9 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: uw61772691). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, August 28, 2021). M2.9 Earthquake 8 km NNE of Hamilton, Washington — August 28, 2021. Retrieved November 6, 2021 from https://www.earthquaketracker.org/earthquakes/event/uw61772691/