How strong does an earthquake need to be in order to cause a Tsunami?
All of the above is very true, but many seismologists believe an earthquake of at least 6.0 magnitude is required to generate a tsunami, but of course not all earthquakes above this magnitude will generate a tsunami, even if they occur under the ocean. However, it is mainly a factor of the amount of displacement in the ocean crust as a result of the earthquake, rather than the amount of energy is released by it, as this is what causes the tsunami wave.
