About 20,000 people are practicing around the Northwest this week for a megaquake and tsunami. Here’s why their efforts are important.

Share story

About 20,000 people are testing the region’s readiness for disaster this week, preparing for an earthquake-and-tsunami one-two punch that could devastate the Pacific Northwest should a megaquake rip along the 600-mile-long offshore fault known as the Cascadia Subduction Zone.

The “Cascadia Rising” exercise — the largest of its kind ever in the Pacific Northwest — tests emergency responses across the region.

Washington state National Guardsmen will deliver supplies on Vashon Island. In Oregon, teams will practice pulling people out of rubble. Amateur radio operators will help with communication.

Here’s why the exercise is important:

Most Read Local Stories

Unlimited Digital Access. $1 for 4 weeks.

About 5.4 million people in Washington would be in danger if a 9.0 Cascadia megaquake struck.

• FEMA projects that about 9,400 people in Washington would die in the event of a megaquake and tsunami.

• Despite decades of warnings, Washington lawmakers have not required seismic upgrades to unreinforced-masonry buildings. There are at least 1,163 of these buildings in Seattle. The buildings are the most dangerous type of structure to be inside during an earthquake.

• Scientists say it’s possible coastal communities could be hit by 100-foot waves if the Cascadia Subduction Zone snaps.

• At school facilities, a megaquake could cause $4 billion in damage, hurt more than 3,000 students and staff, and kill more than 100. Unlike other states, Washington has not finished an assessment of dangers to schools, even though many schools here predate modern building codes.

• Rough estimates of megaquake damages put the total economic cost to Oregon and Washington at around $80 billion.

• Other quakes put Seattle at risk, too. There’s even a fault right beneath the heart of the city, known as the Seattle Fault. If that ruptures, researchers believe it could trigger more than 30,000 landslides in Seattle, potentially damaging more than 10,000 buildings.

Efforts are under way to create an early-warning system for a megaquake, but even that would notify people only a few minutes before one hits.

• Some scientists believe that megaquakes (of which there have been several in recent years) come in clusters.

• The Cascadia fault is so weak that tidal forces are enough to trigger tremors and ratchet up pressure on the Cascadia Subduction Zone.

Pacific Northwesterners might be without supplies for more than a week if the Cascadia fault rips.

Earthquakes are inevitable. Here’s how to prepare before the next one strikes, and what to do when it does.