A magnitude-9 earthquake hit the Tohoku region of northeastern Japan, triggering one of the most destructive tsunamis in a thousand years. The Japanese — the most earthquake-prepared, seismically savvy people on the planet — were caught off-guard by the Tohoku quake’s savage power. Over 15,000 people died.
Now scientists are calling attention to a dangerous area on the opposite side of the Ring of Fire, the Cascadia Subduction Zone, a fault that runs parallel to the Pacific coast of North America, from northern California to Vancouver Island. This tectonic time bomb is alarmingly similar to Tohoku, capable of generating a megathrust earthquake at or above magnitude 9, and about as close to Portland, Seattle, and Vancouver as the Tohoku fault is to Japan’s coast. Decades of geological sleuthing recently established that although it appears quiet, this fault has ripped open again and again, sending vast earthquakes throughout the Pacific Northwest and tsunamis that reach across the Pacific.
What happened in Japan will probably happen in North America. The big question is when.
On a foggy spring morning just before sunrise, 27 miles northwest of Cape Mendocino, California, a pimple of rock roughly a dozen miles below the ocean floor finally reaches its breaking point. Two slabs of the Earth’s crust begin to slip and shudder and snap apart.
