The reason people are suspicious is that a group with a bad track record is encouraging something dangerous. Sure the Chinese, the Iranians, hell the Canadians are looking to access systems in the US, but that isn't a reason to trust DHS. What we know about this one incident is that DHS made a rather unorthodox request.
Centralia is only the best known coal fire in the US. Some are not mine related, some like Laurel run PA are. Centralia is a mix. The fire was started at a landfill, but that landfill was located in an abandonded strip mine. The natural coal seam wouldn't have been near the surface had it not been for the mine.
Twenty years ago the Republican nominee was a Title X sponsor. One of his major campaign themes was no new taxes. You really need to pick a different time frame if you want Santorum to look like a viable candidate.
I doubt books from the 1940s or 70s have anything to say on whether a specific recent increase in earthquakes is fracking related. Sure we've known that it was related in other situations, but this one is a new incident worthy of study on its own.
I seem to recall a Google study that said almost the opposite. It points to a small spike increase in death rates in the first few months, then a drop, followed by a continued climb. Their references also point to issues with specific types of drives, though I haven't read it and can't speak to the results.