Don't know where this happens so no link, just going off what I heard.
It can destroy half of LA, which is 1300 km^2. Assuming LA is roughly square shaped that gives us a 36 km diameter, since it's only half of LA we divide that by 2 for 18 km, and then that by 2 for a 9 km radius.
Sticking that into the Nuke Calculator gives 1200 megatons, which is divided by 2 since only 50% of the energy is the actual blast. Therefore Ghost Rider tanked 600 megatons.
Result
Ghost Rider's Durability - 600 Megatons, Mountain level+