How a shallow fault running directly below Seattle went undiscovered for a millenium

About 1,100 years ago, a major earthquake rocked Puget Sound, suddenly shooting what is now Restoration Point on Bainbridge Island up about 23 feet while Seattle's West Point sunk more than three feet. The quake, which would likely have had a magnitude greater than 7.5, rattled along the Seattle Fault Zone, a several-mile-wide fault that runs east-west, from Issaquah to Hood Canal, passing through the stadiums and Alki on its way.