No, you can't prevent a tsunami. However, there are a number of ways of predicting the arrival of one in time to warn people to get to safety; and there are also several ways to protect an area from the worst effects of a tsunami.

A tsunami is triggered by an earthquake, but not always. For a tsunami to follow, the earth's crust in an earthquake must move vertically rather than horizontally. It is this movement that causes waves to be displaced and creates the enormously high waves that you see in a tsunami. At present it takes well over an hour for scientists to calculate whether the movement is vertical or horizontal, by which time the tsunami may well have formed already. it is hoped that they will manage to reduce this time in future.

It is also possible to create protection systems against tsunami. The most advanced of these can often be found in Japan; sadly the 2011 tsunami was too powerful for some of the existing walls and barriers that were in place, but new ones are being built.