Study: Fault line under Seattle bigger than thought

Study: Fault line under Seattle bigger than thought »Play Video
SEATTLE -- The fault line under Seattle could be bigger than anyone thought, according to new research conducted by a University of Washington graduate student.

Beth Martin found evidence that could mean quakes along the fault line could be larger, and even trigger a tsunami.

The Nisqually earthquake that rocked the Northwest eight years ago was a 6.8 magnitude.

The quake, centered deep in the Earth, caused a lot of shaking and some damage.

But the ground didn't rise up like it did 1,000 years ago. That's when scientists believe a 7- to 7.5-magnitude earthquake hit the more shallow Seattle fault zone that runs from Sammamish, through Seattle and out toward Bremerton.

Scientists believe some areas rose 18 feet during the quake, that the southwest tip of Bainbridge Island rose out of the Puget Sound, and so did much of Alki Point in West Seattle, which is now full of homes.

The quake also generated a tsunami - a wave possibly six feet high - when it hit Elliott Bay in Shoreline.

And now Martin says she's gathered evidence that the Seattle fault zone could be much bigger than we think, and a quake could spread damage much further west.

Martin's evidence comes from, of all things, clams. They're carbon-dated back to that big quake and found in soil samples she took in the tide lands near Gorst, much further west from where scientists believed the fault ends.

"So somehow this area went from a tide flat with clams in it to a cedar forest. So that's my evidence that everything went up," she said, pointing to the soil sample.

If the shallow Seattle fault is longer, scientists say another quake could do more damage and trigger a bigger tsunami.

Scientists say they aren't sure exactly where the fault line begins and ends.

And in case you were wondering, yes, an earthquake underneath Lake Washington could generate a tsunami.