This page discusses the physics of tsunamis. It includes meteor impacts as possible causes.

A tsunami can be generated by any disturbance that displaces a large water mass from its equilibrium position. In the case of earthquake-generated tsunamis, the water column is disturbed by the uplift or subsidence of the sea floor. Submarine landslides, which often accompany large earthquakes, as well as collapses of volcanic edifices, can also disturb the overlying water column as sediment and rock slump downslope and are redistributed across the sea floor. Similarly, a violent submarine volcanic eruption can create an impulsive force that uplifts the water column and generates a tsunami. Conversely, supermarine landslides and cosmic-body impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls. Generally speaking, tsunamis generated from these mechanisms, unlike the Pacific-wide tsunamis caused by some earthquakes, dissipate quickly and rarely affect coastlines distant from the source area.

In the event of a large impact, the energy released might be comparable to a major earthquake. I've heard some reports that this earthquake had the energy of some 30,000 Hiroshima sized bombs. Since those bombs were on the order of 15 kilotons, that would be the equivalent of about 450 megatons. By way of comparison, 2004 MN4 was estimated to have an impact energy of 1600 to 2200 megatons. An impact in the water would generate very substancial waves.

It may already be happening more often than anyone realized. Scientists have used satellite data to track rogue waves. In a 3 week period, they found 10 of them. One possible cause for some of them is impacts. It's a different phenomenia than tsunamis, but threatening just the same. Some believe the rogue wave that struck Daytona, Florida in 1992 might have been caused by an impact.

In March 2001, the first officer of the cruise ship Caledonian Star saw a wave that chilled his soul. It stood almost 100 feet tall, towering over the surrounding waves, and it didn't slope -- it was a sheer wall of water. It smashed into the ship with such force that it broke windows and flooded the command deck.

This watery beast was what scientists are now calling a rogue wave. According to a study released this year, there are more of them roaming the oceans than anyone ever imagined. In July, the European Space Agency announced that it had conducted the first satellite study of the oceans, looking specifically for rogues. In a three-week period, the satellites discovered 10 rogues, some taller than 85 feet. The scientists involved said they were stunned by the results, because for centuries skeptics dismissed reports of gigantic waves as myths. Wave equations normally describe an average wave height; they don't describe rogues.