I wasn't exactly sure how to describe this because it's not quite a shockwave. But you see it often with different weapons and abilities in Castlevania games like these examples. It's easy enough to get the projectile animation working, but I'm struggling to get that neat "trailing" effect as they move across the ground. I'm guessing it might work similar to an animated ghost trail for dashing, etc. that's also very common in those games, but starting about halfway through the projectile's animation and not transparent or anything?
EDIT: After looking closer and thinking about this a little more, I don't think it's just an animated trail. The trails can typically still do damage, so I think it's more like each projectile spawns another instance of flames or whatever behind it at a set distance around halfway through its animation cycle.