They're rare events, but they're also inevitable, the disruption to service after a serious quake will be prolonged, and this factor is completely under our con

They're rare events, but they're also inevitable, the disruption to service after a serious quake will be prolonged, and this factor is completely under our control when selecting a host, unlike the others you list. Most companies offer a choice of datacenters and it's pretty easy to pick one that is not sitting on a fault.