This is a good question, that I cannot answer fully, although I think I have a few ideas. JCarter426 is around here a bit lately, so hopefully he can fill in the gaps and give a real explanation.
I would think that there is a number in combatanimations.2da that corresponds to the power blast, and any other combat animation, right?
What number that is.... that is the difficult part. Is there a way to determine what animation actually is the power blast? Has someone already done this for us?