Page "Comet Shoemaker–Levy 9" Paragraph 25

As predicted beforehand, the collisions generated enormous seismic waves which swept across the planet at speeds of and were observed for over two hours after the largest impacts.

The waves were thought to be travelling within a stable layer acting as a waveguide, and some scientists believed the stable layer must lie within the hypothesised tropospheric water cloud.

However, other evidence seemed to indicate that the cometary fragments had not reached the water layer, and the waves were instead propagating within the stratosphere.