A recurring theme among native populations from western Vancouver Island and northern Washington is of an epic struggle between Thunderbird and Whale, supernatural beings whose ferocious battles cause the ground to shake and the seas to rise. More literal anecdotes describe houses swept away, rivers changing course and trees draped with debris.

Last week, the PTWC released an animated simulation of the Cascadia tsunami created with the same real-time forecast model they use to issue tsunami warnings today. The model shows the progress and severity of the waves over time and the corresponding increase in danger to coastal areas.

The simulation highlights the incredible challenges governments and first responders will face when the next ‘Big One’ hits the west coast: within minutes of the quake, low-lying areas that may have already sustained significant damage will also have to brace for a severe tsunami.