A couple of years ago California conducted an earthquake exercise for a 7.9 Richter Scale quake. This level of quake was set because anything greater would be impossible to plan for, think about. With this as a partial stimulus, I developed a catastrophic mass fatality plan precisely for the purpose of responding to "the unthinkable." The plan assumes a massive death rate, infrastructure ground to a halt, no outside resources for an extended period. Think events such as the 1918 pandemic. Most of what passes for mass fatality plans are really "multi-fatality" plans, e.g., air crashes or even horrific events such as 9/11 (in short order, outside resources were brought in).
From what I've been able to find, few have gone this distance to try to develop plans for such large scale catastrophes. I propose that it is possible to develop what I call "legacy plans" that could actually help those left behind think through whatever might be possible to help deal with large scale catastrophes.
Even this campaign participates in the denial. It has five subtopics: Communications, Medical Response, Search and Rescue, Resource Distribution, Data Sharing. Yet the description refers to 190,000 dead and another 265,000 seriously ill. Where in the sub-topics is the "mass fatality plan?" It is almost as if the dead bodies will just magically be dealt-with.