Bedrock is very deep in Seattle. You can see the map here: https://pubs.usgs.gov/mf/1692/plate-1.pdf

For instance the space needle is just on a giant hunk of concrete that is only 30ft deep. https://www.spaceneedle.com/history#:~:text=An%20underground....

But from memory most large buildings in the downtown area are on deep foundations in soils, not to bedrock.