Cascadia Subduction Zone By: Zana Burnett

Cascadia Subduction Zone The Cascadia Subduction zone is a type of convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping fault that separates the Juan de Fuca and North America plates. Great Subduction Zone earthquakes are the largest earthquakes in the world, and can exceed magnitude 9.0. Earthquake size is proportional to fault area, and the Cascadia Subduction Zone is a very long sloping fault that stretches from mid-Vancouver Island to Northern California.

Earthquakes The last known great earthquake in the northwest was in January 1700, the Cascadia Earthquake. Geological evidence indicates that great earthquakes may have occurred at least seven times in the last 3,500 years, suggesting a return time of 300 to 600 years. The width of the Cascadia Subduction zone varies along its length, depending on the temperature of the subducted oceanic plate, which heats up as it is pushed deeper beneath the continent. As it becomes hotter and more molten, it eventually loses the ability to store mechanical stress and generates earthquakes. Because of the very large fault area, the Cascadia Subduction Zone could produce a very large earthquake, magnitude 9.0 or greater, if rupture occurred over its whole area.

Hazards The Subduction of the Juan de Fuca plate beneath North America changes markedly along the length of the Subduction zone, notably in the angle of Subduction, distribution of earthquakes, volcanism, geologic and seismic structure of the upper plate, and regional horizontal stress. Flooding Tidal Waves Collapsed Buildings

If an earthquake occurs at the coast Drop, cover and hold. Get under a sturdy object and hold on. Watch for falling objects. As soon as the shaking is over, move to high ground or inland. Do not wait for an official warning. Stay away from the coast. Waves may continue to arrive for hours. Listen to your local radio station for an official "All Clear" notice before returning to the coastal area. Be alert for aftershocks. Have an emergency kit including clean water and food.

Protect yourself and your family Develop a family disaster plan. Everyone needs to know what to do on their own to protect themselves from an earthquake. Be familiar with local Emergency Management earthquake and tsunami plans. Know where to go to survive a tsunami. Be prepared to survive on your own for a minimum of three days. Prepare a disaster supply kit for your home, automobile and work. Take a first aid course and learn survival skills. Knowledge is your greatest defense against potential disaster.