I adore apocalyptic and post apocalyptic fiction. When I decided to do a post apocalyptic anthology, I went back to the stories I loved the most to figure out why I loved them so much. It wasn't just that the world as we knew it was ending and had ended, it was how and what happened next.
The idea that the world could end in a way that still gave a chance to the survivors to make some sort of normal life for themselves was important to me. That is why I was specific in that it was a combination of bioterrorism and Mother Nature. I will be honest, when I first wrote up the guidelines, there was a lot of generic hand waving over the how and why of the coming of the end. What was important to me was "what comes next."
(Of course, amandapillar convinced me the how and why was just has important as the rest when she got a hold of the anthology as my co-editor. But, I digress.)
To me, apocalyptic fiction shows the best and worst of people in their situation. It was after the "end" that I wanted to read about. Would people come to Grants Pass? Would they reject the idea? I did not know. I wanted stories of all types from around the world. Stories in which people could not go to Grants Pass. Stories where people thought Grants Pass was it. Stories where Grants Pass was evil.
As a writing exercise, I also wanted the people of the writing group to write something closer to home. I wanted them to think about their own situation. How would they (or their fictional characters) deal with the destruction of the world by bioterrorism and horrific weather? It was a bit around the "write what you know" (or can extrapolate) exercise. Which is why it was not a nuclear holocaust, an alien invasion or zombie hordes. I wanted the writers to have one foot in reality as they wrote. I did not want to deal with the fantastical. If there was a fairy in the story, it was because the character was insane and the reader knew it.
Finally, and I will admit this, Grants Pass was chosen as a location for two reasons. First, it is almost halfway between Seattle, WA and the Bay Area, CA. About at the 430 mile mark. I drove that city, on average, 4 times a year for four years. It became a point of importance on my trips. Once I hit Grants Pass, everything else was "downhill" so to speak.
Second, I really did write a post about Grants Pass about a year before I put up the guidelines for the writing group. I did dream about Grants Pass. I did joke about going to Grants Pass in the apocalypse and some of my friends started chiming in on the idea of going to Grants Pass. Really, the theme and guidelines for the anthology were born from a "what if" based in my own life.
Write what you know. Read what you want. Do a call for what you want to read.