I do, although not one as prone to severe earthquakes as you do. Most of my gear is fastened down in some way.
This is an issue I've had with my set-up, which is one of the reasons for my recent shuffling of gear; it's still not as good as I'd like it to be in that respect but it's better than it was. The cart is a great idea but it wouldn't work in my shack because there's not enough room to pull it forward to get behind it. I do have a plan, though. Sometime this year, I hope to turn the garage which lies behind the wall that my gear faces into a workshop. Once I do that, I'm going to put a door in that wall, then build a rack and move my gear so the back faces towards what's currently the laundry room. That way I'll have access to the back of the gear without even having to move anything.also, no easy way to get behind stuff to rejigger connections when required. (i have my stuff on a heavy-duty cart--roll it out and everything in the back is accessible).