Part of this comes from the fact that Seattle's SODO area is built upon slews placed over glacial rock so the reverberations from the Stadiums basically bounces down and is reflected back.
I'm trying to find where I heard the whole description of this, I believe it was from `hugefloods` youtube channel.
I believe it was this video: https://www.youtube.com/watch?v=fuK2kGeV15Q
But I don't have time again to search through it, so this is pretty lazy proof, sorry.