The Seahawks have held their cards pretty tightly to their chest this preseason -- Jimmy Graham has only been used sparingly and Marshawn Lynch almost not at all -- and so the true identity for this year's offense has yet to really be revealed. That said, I think it's pretty clear that one concept will be a pretty key part of what they do.
I don't know what the Seahawks call it, but it's a "levels" concept based off of play-action, and the goal is to flood a zone, so you're seeing two defenders try to match up with three Seahawks, and it's something that we've seen them do with varied personnel throughout the years.