The Seahawks seem to be playing a lot of "Bear" fronts this season. They've done it in the past but they're doing it a lot more now, probably due to the personnel they have. In this front you have a NT flanked by two 3-technique DTs. It clogs the middle making it hard for the offense to double team, pull, trap, etc. It's more vulnerable on the edges but I think the Seahawks feel they can counter that with their team speed, especially when we bring in more DBs.
As for your question, in the "Bear" front you'll often see players in the traditional SAM and WILL positions stacked on the same side. Think Otis Wilson and Wilber Marshall. Hers's what it looks like:
Most people think of the Seahawks' base defense as a "4-3 Under" but we've seen less of that in its pure form. One reason might be that we don't have anybody in the mold of Red Bryant that can dominate when 2-gapping on the strong side. The 4-3 Under looks like this:
I'm actually surprised there hasn't been more talk about the use of the Bear front this year - it seems like a significant shift. If you look at the players we've brought in (Snacks, Rush, Bullard) they seem to have been chosen to fit this scheme. If Snacks can play close to what he has in the past as a 2-gapping 0-tech NT, rotating with Mone who has been good, that could really help this front. KJ seems to have taken to it as well.