Early prevention of tsunamis should be divided into two categories: preventing earthquakes and preventing landslides. These two are the primary causes of tsunamis and hence deserve the most attention as priority targets.
Prevention of earthquakes would rely on the deliberate generation of minor quakes in order to release the elastic tension energy stored in the tectonic plates under stress.
One way to generate quakes is to have something similar to flail tanks in World War II used to clear mines. Adaptations would have to be made but these machines would go into deep water and proceed to flail the ground along the fault lines. This would occur at a regular interval and result in minor and harmless tremors. This might be a very expensive option as developing these underwater machines would likely be costly
Another way to generate quakes would to use ultra low sound emitters at resonant frequencies. Once a line of the emitters are in place along the fault line, they can produce resonance that would disrupt and cause ruptures. These emitters should have the ability to relocate or they will get destroyed in the actual plate movements while at the same time they need to be close to be effective.
Yet another way to generate quakes would be use of explosives. Only explosives that would be practical to use would be tactical nuclear weapons. These are cheap and more practical compared to equivalent amounts of TNT. Furthermore, they are quite abundant in the remnants of the Cold War arsenals. The unfortunate side effect is the tremendous amount of nuclear fall out that would occur. Regular nuking would utterly devastate ecosystems and have unforeseeable repercussions.
Why they would not work
However, these ideas are
generally impractical. It turns out that flail tanks and sound emitters would
likely have too little energy to trigger a quake. According to the US
Geological Survey, a thermonuclear test named "Faultless" ironically
produced a new fault rupture on Jan. 19, 1968.
However, even then, the wavefield generated was only 20-30% earthquake like.
The largest thermonuclear test by the
Prevention of landslides is important as not all tsunamis are generated by earthquakes. The first option will be to provide concrete braces and other reinforcement structures for sections of the seafloor deemed vulnerable to slides. This would be able to prevent a significant amount of sliding. However, itís impractical and costly to do this for large areas. Only high risk areas and important protection locations like major ports and cities should have this nearby. There is also need for novel structural materials which would render it practical to build such structures as a replacement time of less than ten years is likely to be unacceptable.
The second option is to have small artificially triggered underwater landslides. These can be triggered with explosives or with small mobile underwater dozers. This is more practical than triggering quakes in that it can be smaller and more localized. Use of power that only nuclear weapons can provide is likely unnecessary.
With landslides, cost of reinforced concrete would be prohibitive. One can only do this for important areas like near city harbors. However, tsunami waves that hit can come from across the globe. Money on reinforcing underwater topology to prevent slides is likely better utilized for physical dissipation in form of seawalls and mangroves.
 J. Louie, What is Richter Magnitude. http://www.seismo.unr.edu/ftp/pub/louie/class/100/magnitude.html. Oct. 6, 1996
Page by: Peak Xu
Page by: Peak Xu