I've been assured by IRS personnel that relief will happen automatically.  That's somewhat tongue-in-cheek but that doesn't make it less true.  I've also been assured by IRS personnel in the past that every CP-2000 letter is reviewed by a human before it goes out.

If you're unlucky enough to not have been picked up by the automated "disaster by zip code" system (or, for example, if your books and records are in a disaster area but your mailing address is not) you can self-identify by calling 866-562-5227.

Rick

Edit: I'll tack on the FAQs for posterity:

https://www.irs.gov/businesses/small-businesses-self-employed/faqs-for-disaster-victims