Try out a Displacement Map with a precomp of your shockwave.
Using a white solid, add a circle mask and animated the circle to expand and collapse. When you’re happy with the timing, you can copy the mask, but use Expansion to reduce it’s size and set it to subtract. This will give you a donut. Feather the outer mask a little and the inner mask a lot, to give you a leading edge look.
Then precomp this and use a diplacement map on your animation (either directly or an adjustment layer). See if that gets you closer to the look you’re after.
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