A six foot wave?! That’s pretty routine around my home
in Charlevoix,Mi., on Lake Michigan.(No earthquakes though).
This “wave” might be 100 miles wide. Think of it like a storm surge in a hurricane.
This isn’t a wave that goes up and down. The entire ocean level seems to rise 7 feet, then it just keeps coming... and coming... and coming.
Imagine if the sea level suddenly rose by seven feet. The force can wash away an entire town and kill thousands.
Besides what the other commenters are telling you, an ordinary wave doesn’t move water forward with the wave (until it breaks in the very last stage, lasting seconds). The tsunami obeys the same rule, but it is ‘breaking’ the whole time it is approaching land — moving untold billions of cubic meters of water up and onto the land for minutes, at least.