A large portion on the energy would be exerted on the landmass. I doubt the asteroid will explode mid air like nukes are designed to do, if it does most of the energy from an atmospheric explosion will be reflected up into space anyway.
The worst possible scenario would be it hitting the middle of the pacific. That would cause a very large tsunami...
An earthquake causes a different kind of damage too. It mainly causes plate tectonics to suddenly burst into horizontal or vertical movement and maybe a tidal wave, if it lifts on plate over an other underneath a sea/ocean. But an asteroid causes an explosion, an earthquake, a shock wave through air and earth, a dust cloud, the crater might shoot debris high into the atmosphere and cause days of meteor showers, etc. It's a different kind of destruction all together.