These smaller plates plunge beneath the North America plate at a rate of 1 to 11/2 inches per year. As the Juan de Fuca and Gorda plates push into North America, stress accumulates. Earthquakes are caused by the abrupt release of this slowly accumulated stress.
CSZ earthquakes are believed to occur every 200 to 600 years, and the last major event in the CSZ is estimated to have occurred 300 years ago.
In the event of an earthquake, move to high ground until told to return to lower lying areas that are susceptible to tsunamis.
You may need to survive on your own after an emergency. This means having your own food, water, and other supplies in sufficient quantity to last for at least three days. Local officials and relief workers will be on the scene after a disaster, but they cannot reach everyone immediately. You could get help in hours, or it might take days. In addition, basic services such as electricity, gas, water, sewage treatment and telephones may be cut off for days, or even a week or longer.
Go to this link to read the items you should have set aside in case of an emergency.