A magnitude 4.2 earthquake struck the Pacific Northwest near Seattle, Washington on Tuesday evening, with over 5,000 residents reporting the tremor across the Puget Sound region. Whilst the quake caused no reported injuries or significant damage, with shaking described as weak to light, it has renewed attention to the Cascadia Subduction Zone—a major fault system that scientists believe is overdue for a catastrophic event.

The earthquake occurred approximately 22 miles from Seattle at 5:05 PM ET on 29 September. Seismic events exceeding magnitude 4.0 typically occur in this region only once every three years on average. The epicentre was situated near the Cascadia Subduction Zone, a fault where the Juan de Fuca Plate pushes beneath the North American Plate. Scientists warn this zone is capable of generating a magnitude 9.0 earthquake—potentially the worst natural disaster in North American history—with such major ruptures historically occurring every 400 to 600 years, the last recorded in 1700.