I was in the 6.8 Nisqually quake in 2001. It lasted about 30 seconds. That was quite long enough for me.
They say that if the Cascadia Subduction Zone does the “full 9.0 rip”, it could shake for as long....if not longer...than the Alaska quake.
I was down in Georgetown for the Nisqually EQ in an area that was all a bunch of fill built up on old tidal flats. At first I thought a train was derailing on the track that ran next to my shop. There was a big freight yard next door and you could see the waves moving across the ground. It was pretty weird.