It’s still just a single-point energy release. Doesn’t matter if it’s caused by an H-bomb, or a landslide. Doesn’t matter if the ground pushes up from below, or falls down from above. The 360* spreading energy formula is what counts. Since energy is conserved, it RAPIDLY loses its wave height as the circumference grows geometrically.
The Christmas tsunami was NOT a single-point-origin event, but was 100s of miles long. As a result, the 360* energy dissipation was not in effect. The “shoulders” of wave energy on each side of any point along the tsunami reinforce the wave, preventing it from spreading out in 360* and losing its energy.
I really don’t see what is difficult to grasp here.
Thanks!