Swarm Of 90 Quakes Hits Off U.S. West Coast

Swarm of earthquakes jolts seabed off the U.S. West Coast

Dennis Mersereau

A swarm of earthquakes rattled the seabed off the U.S. West Coast this week, causing quite the ruckus in an area that’s used to the occasional rumble. The tremors struck along an active fault line situated off the Oregon coast. However, some good news is that seismologists don’t expect this earthquake swarm to trigger tsunamis or larger earthquakes closer to land.

A series of earthquakes began shaking several hundred kilometres off the Oregon coast during the predawn hours on Wednesday, December 7. The temblors came fast and furious; the United States Geological Survey (USGS) recorded dozens of earthquakes over the next 24 hours, including eight that measured 5.5-magnitude or stronger.

Approximately 90 earthquakes have been recorded in the area since Wednesday morning.

The earthquakes occurred along the Blanco Fracture Zone, an active fault zone between the Pacific Plate and the Juan de Fuca Plate. The two plates slide past one another across this region, causing earthquakes as they move.

This week’s earthquake swarm isn’t the first dense cluster of earthquakes along the Blanco Fracture Zone. Several clusters of small earthquakes have occurred here over the past 30 years. A notable swarm in the same area in 2008featured more than 600 small tremors in just a couple of weeks.