[gcruse]

I can't imagine an asteroid big enough to create a hot spot plume at the antipode which is, after all, all the way through the planet.

Maybe it will give a plume that is already there a pop, or create an interstitial weakness that later becomes a hot spot. More likely, hot spots just happen.

[MainFrame65]

The math is well beyond me, but I believe that the idea is that the stricture of the Earth would act as a lens and mirror system, with the varying densities of the inner core, mantle, and crust, as well as the boundary effect of the outer spherical surface acting to focus the energy on the opposite side (antipode).

I don't know if it relates, but if you drop a heavy ball straight down into a pool, the water flows around the top of the ball and spouts upward rather than just splashing out.

[Mike Darancette]

I can't imagine an asteroid big enough to create a hot spot plume at the antipode which is, after all, all the way through the planet.

The shock waves are radiated in all directions from the impactor. The shock waves travel around the globe and can be additive at the antipodes.

There can be as much damage on opposite side of an island as on the end hit by a tsunami because the wave reinforces itself when it comes together again.