I remember reading multiple threads about this subject and it was concluded that you'd need practically all the nukes humanity has ever produced to actually make an effective tsunami. The earthquakes that create tsunamis will first of all create a permanent change in volume, while nukes create a void, that will very quickly collapse, or if it bursts the ocean's surface, most of the energy is dissipated upwards. Also, the energy released even in small earthquakes is determined in gigatons or even teratons of energy.