For what it’s worth, Amazon did just have a very public search for an HQ2 location and ended up picking one on the other side of the country: https://en.m.wikipedia.org/wiki/Amazon_HQ2
I wouldn't count on it. In terms of their IT infrastructure, they've got more than one datacenter geographically distributed so they're prepared for it. I don't think companies are really good about planning around events that don't happen regularly. Especially one as amorphous as "the big one" in a place that isn't California.
Agreed. AWS's cloud infrastructure is all about high availability and spreading computing/data resources across regions. The company's operations will be fine. Although, I'm sure the higher ups in Seattle have personally spent enormous resources to get their homes upgraded and have extensively prepared for something like this. The average person can stock up on non-perishable food and water, but besides that they don't have the resources to truly prepare for what is coming.
You can't really prepare for everything. I would even doubt if most of the Amazon higher-ups are thinking much in this direction or are prepared in even the usual ways (2 weeks of food, a barrel of water, and extra batteries level).
We just aren't going to live forever. If its any consolation, you'll (not you in particular :D) probably die in a car accident or a cardiac arrest when you aren't even worried about it.
You can certainly prepare your house for the earthquake and shaking. For one, reinforcing the structure, making sure the ground is under the house is attached to stable, hard rock like granite versus sediment, and very importantly, using wood instead of brick or concrete (look at Bill Gates's Xanadu house - it's not a coincidence that it is completely made out of wood, the best house material for withstanding earthquakes). These people are definitely consulting scientists and engineers and preparing themselves and their family for a potential M9+ event.