Which is not true?

That the apparent motions are due to compression?

Or that the plate can compress like that?

I can see on the map, especially with North America, how the change in direction vector across the US is due to the plate rotating. I see how the further from the apparent center of rotation, the velocities increase. This is just like a record spinning. It has a constant angular velocity, but depending on how far your are from the spindle, the linear velocity changes - slower on the inside, faster on the outside.

I'm just having a little trouble seeing much rotation on the Pacific plate, but that may be due to the dearth of GPS stations. It appears the Pacific plate is moving pretty linearly. Yeah, I'd have to do the math to really see it, spherical geometry.

OK. I will accept that the GPS measurements are due to rotation.

But, can this be a separate issue from the plate not being able to accommodate 20mm of compression across 4000km?

Are the plates really THAT rigid?

Even the NA plate deforms in the western US where it meets the plate boundary. The vectors all start rotating as you approach California, and THAT is not due to rotation, but deformation. Right?

Brian