New studies put potential megaquake closer to Seattle

SEATTLE - Pacific Northwesterners have learned to live with the knowledge that a monster earthquake will wallop the region one day.

But for Seattle-dwellers, that harsh reality has always been tempered by the fact that the fault called the Cascadia Subduction Zone is most likely to snap offshore - nearly 100 miles from the urban corridor.

Now scientists are beginning to suspect the jolt could come much closer.

The latest evidence is an upcoming study in Geophysical Research Letters that concludes the danger zone could lie within 50 miles of Seattle.

"That's a lot closer to where everybody lives," said co-author Timothy Melbourne, of Central Washington University.

The closer the quake, the heavier the damage in Seattle, said Thomas Heaton, professor of engineering seismology at California Institute of Technology. Heaton, who was not involved in the study, conducted computer simulations that show the city's tall buildings would be particularly vulnerable.

"If that earthquake happens, it will hammer the place," Heaton said. "It will hammer harder if it's closer."

The researchers hope their work will help spur tougher building codes.

"There's no reason to panic at the moment," Heaton said. "But on the other hand, people shouldn't just walk away and say: 'Oh, let's not think about it.' "

The 600-mile-long subduction zone is the place where the ocean floor is being shoved, or subducted, under the continent.

It's one of the world's most treacherous faults, capable of unleashing megaquakes and tsunamis on a par with the 2004 Sumatra disaster.