re: Good plan.
An impact of even moderate size would produce waves vastly different than those from an earthquake.
The 60,000-megaton blast of the impact vaporizes the asteroid and blows a cavity in the ocean 11 miles across and all the way down to the seafloor, which is about 3 miles deep at that point. The blast even excavates some of the seafloor. Water then rushes back in to fill the cavity, and a ring of waves spreads out in all directions. The impact creates tsunami waves of all frequencies and wavelengths, with a peak wavelength about the same as the diameter of the cavity. Because lower-frequency waves travel faster than waves with higher frequencies, the initial impulse spreads out into a series of waves.
"In the movies they show one big wave, but you actually end up with dozens of waves. The first ones to arrive are pretty small, and they gradually increase in height, arriving at intervals of 3 or 4 minutes," Ward said.
From UC Santa Cruz