It may be time for you to borrow some traps from the animal control people and catch the perpetrator. Whatever it is, it is obviously up to no good and is also keeping you awake half the night. I live in the country so I am a bit more mercenary about pests. I love animals, but there are lines that once crossed relegate a harmless wild animal into the pest status. In my world, once a wild animal reaches pest status, then it is TIME. I've had to do some hard things out here, but necessary things. I never let the animals suffer. When possible, I trap pests and put them to sleep using ether, larger pests I simply use the tried and true bullet. After paying a fortune to restore my vehicle, and after having two members of a family in a nearby town die from Hantavirus last year, I have a sterner view on pests. Yes they're cute and fuzzy, but when they destroy property and carry deadly viruses, what has to be done is clear.
Good luck with the scratching. Hopefully you'll be able to trap it to at least find out what it is.
Hi Egraine, I think it is a big, gray, stray cat. Saw it on our deck today but our great big Maine Coon cat girl scared it off by her loud hissing. She is in an enclosed screen porch area so can't go out herself. She is strictly an indoor cat; but she sure made enough noise to scare this stray away. This also let me know who the culprit likely is. Thanks..about the moth balls. However, too low for me to crawl under the house. It's been since my mom's day that I have used them and I do remember that smell. Growing up we hung them in the closet to protect our wool things from moths.