Seismic doesn't really mean anything in the context though. There's no scale of election results which defines "seismic" in a certain way. It's just a metaphor.
Is this an important result, politically?
If the result is mirrored at the general election, the SNP will lose some seats in Westminster and Labour will gain some. It means that the SNP is less likely to hold the balance of power. This in turn means the SNP has less leverage to demand an independence referendum. Of course, with the polling as it is, I don't think the SNP holding the balance of power was realistic anyway. If the polling between the Tories and Labour was closer, it would be pretty important, but it isn't, so it's not.
Does it mean anything for the government of Scotland? Maybe, as an indicator that people are unhappy with the SNP, but nothing beyond that. Wghen are the next Scottish parliamentary elections anyway?