'The difference between alarming and catastrophic': Cascadia megafault has 1 especially deadly section, new map reveals

The Cascadia subduction zone has the potential to rock the Pacific Northwest and British Columbia with devastating earthquakes. Now, a closer-than-ever look at the megafualt's structure reveals it is segmented into multiple major regions. 

These regions might rupture individually or they could all unleash a massive temblor at once. But the findings indicate that the experience of a quake might be different in each zone. 

"It requires a lot more study, but for places like Tacoma and Seattle, it could mean the difference between alarming and catastrophic," study co-author Harold Tobin, a geophysicist at the University of Washington said in a statement. 

In many subduction zones, where oceanic crust grinds underneath lighter continental crust, small and medium-size earthquakes are common. These mini-quakes give researchers information about what the hidden portions of tectonic plates look like and where various faults are located. 

Related: Sleeping subduction zone could awaken and form a new 'Ring of Fire' that swallows the Atlantic Ocean

But Cascadia, which stretches 600 miles (1,000 kilometers) from Northern Vancouver Island to Cape Mendocino, California, rarely throws off small quakes, lead author Suzanne Carbotte, a marine geophysicist at the Lamont-Doherty Earth Observatory at Columbia University, told Live Science. So the best view scientists had of its structure came from research in the 1980s that used shipboard instruments to send small bursts of seismic waves into the crust and then record the returning waves to make images of the subsurface. 

Today's instruments are much more sophisticated, Carbotte said, but no one had done a repeat study of the region. So in 2021, the researchers behind the new study gathered new seismic data along the fault.