Well Dennis has it sorta right in respect to the basin and range - I would suggest reading John McPhee's books on the subject - either his Basin and Range or the Annals of the Former World which includes the Basic and Range.

Maybe you are mis-interpreting the word 'pulse' - there is actually a shortening going on as an anomily - caused by thrust-type faulting - I don't think they've addressed the cause - that's what they are trying to figure out - A pure guess on my part would say that its got to be the interaction of 3 tectonic plates - North America, Pacific and Juan de Fuca - the real question is why is it happening in those 2 areas. I doubt there was a quake somewhere further west that transferred itself eastward.

As for blocks rotating - I didn't see any real evidence of it in those diagrams of the motion (2a) - the thought of the basin and range and its creation is somewhat interesting and overwhelming really. It started out flat - started extending (no real agreement as to why) then faulted and blocks dipped to form mountain ranges and valleys on a spectacular scale that is still at work today.

Canie