If two collided tsunamis kept each other! would they? If two wakes up in a lake not just go bump in the lake ? I'm sure you do!
For a mega - tsunami as world changers that have occurred in the past, we are helpless to the walls of a smaller size seems to help.
the hardest mineral .. Diamond ! but nothing can scratch diamond or another right ? . However, it is almost impossible to build a wall made out of it . What really cost much . Seismologists can think of something , but in the meantime , we will use security measures to be safe in a tsunami ..
Well , tsunamis usually kilometers wide thats why they are so powerful , its legth is a periodic wave , id say no more than 5 meters in terms of height to reach high to the coast due to increasing superficiality of this causes the shore wave height increase can be as high as 30 meters . What can stop as tsunami is a question of how and where you stop powerful . The Great Wall of China easily stop a stronger , because it is so broad that the tsunami , so it will cover all high and to stem the tide . There on the walls of the tsunami in Japan made , many of them , they work quite well . So what is it strong enough? Concrete .
''another' was my first reaction. I believe you'd have to be thinking in terms of Hoover Dam-like construction. It's not just the height of the wave but the millions of pounds of force behind it. Somebody has probably extrapolated a scale determined by such things as slant of shore, speed of water, narrowing of the channel, etc. Consideration of probability and frequency are being used today to determine the efficacy of decisions toward protection of certain vulnerable areas around the world.