A magnitude 4.2 earthquake struck the northern Key Peninsula in Western Washington on Tuesday afternoon, sending noticeable ground motion across the central Puget Sound basin and startling communities from Bremerton to Olympia.
Earthquakes originating more than twenty kilometers below Puget Sound typically disperse seismic energy across a broader geographic footprint while producing lower peak ground accelerations at the immediate epicenter.
Public safety dispatch centers in Kitsap and Pierce counties received dozens of telephone calls from startled citizens seeking confirmation of the seismic disturbance.
Tacoma Fault Mechanics and Regional Subduction Stress Dynamics Geoscientists examining the focal mechanism of Tuesday’s tremor pointed to complex tectonic interactions beneath the Puget Lowland crust.
The event also provided an operational benchmark for the United States West Coast ShakeAlert early warning network.
A magnitude 4.2 earthquake struck the northern Key Peninsula near Wauna at 2:05 p.m. Tuesday, sending tremors across Western Washington without causing structural damage.