I too live within a couple miles of I-5 on the west side just north of Seattle. My current elevation is about 460 feet above mean sea level. The problem with an earthquake that size is that certain areas of the Puget Sound will change in elevation. The entire reason that the earthquake in 1700 was discovered was because of a sandbar in the San Jaun’s that had a couple of hundred dead trees below the water line that were obviously a few hundred years old and not a salt-water variety. They came from the tree-line that was a couple of hundred feet above the channel. They were moved from up in the air to below the water line in a matter of seconds as the ground buckled under and shifted west. So your altitude may not matter.
my grandchildren live in Edmunds...don’t know what their elevation is....
Bingo!