The good news? You can stop worrying about killer waves from asteroids hitting the Earth. The bad? You probably don't want to buy any coastfront property any time soon anyway.
Norwegian scientist Galen Gisler, from the University of Oslo, has been running simulations of what would happen if a 200-metre asteroid hit the ocean, and the results may be better than you'd think:
The impact initially sends waves hundreds of metres high spreading from the impact site. However, the very height of the waves makes them prone to collapse even in very deep water: they start breaking immediately, like ordinary waves on a beach.
By the time they are 30 kilometres from the impact site, they have shrunk to a height of less than 60 metres. The team did not simulate the waves' propagation much further, but extrapolating the shrinkage suggests heights of less than 10 metres by the time they have travelled 1000 kilometres.
That said, that doesn't mean that an asteroid splash would be harmless, says Gisler:
You don't want to be close to one of these things... Local effects will include hurricane-force winds and enormous amounts of water falling directly from the sky.
We suggest that the right decision would be to live far away from any nearby coast... and just hope that the asteroid doesn't fall directly on you, instead.
Asteroids won't raise killer waves - but mind the splash [New Scientist]