Apologies, Ricky, but that’s about as high res an image as I’m going to be able to give you of the node tree. Not in the office today.
If the bumps aren’t very good, I might suggest playing with some of the values. I significantly improved things by turning the noise texture down to point 1 for scale, 8 for detail, point five for roughness.
The Multiply node after the spherical gradient’s colour ramp will control the size of your blast pattern, because the spherical gradient is of course acting as a mask.
Also, of course, adjust the strength of the bump affect. Mine is actually set at 10 with a distance of point 3
Also, if bump mapping just isn’t cutting it, you might try displacement, on a very heavily sub-divided mesh plane. I got some good results with setting midlevel to point 2, and scale of displacement to -1.
Anyway, Happy Blending, and have fun playing with things. Best way ever to learn…