Earthquakes of Cascadia: 1979 - 2019

The widely-felt M6.3 earthquake of August 29, 2019 on the Blanco Fracture Zone was only the most recent of many moderate-size earthquakes to strike this region off of the Oregon coast. As this animation shows, such earthquakes are common along the boundaries of the Juan de Fuca plate with the Pacific Plate, which also includes the Juan de Fuca Ridge, the Gorda Ridge, and the Mendocino Fracture Zone. Fortunately these events rarely pose a tsunami hazard since the largest of these earthquakes tend to have strike-slip mechanisms that move the seafloor mostly sideways with little disruption to the ocean above. The Juan de Fuca Plate meets the North American Plate, however, with a very different sort of plate boundary: a subduction zone. This plate boundary can produce megathrust earthquakes with large vertical motions that cause devastating tsunamis. It has been more than 300 years since the last time the Cascadia Subduction Zone generated such destruction, on January 26, 1700. This subduction zone also c