Do all earthquakes cause tsunami?
Not all earthquakes cause tsunami. Well, most cause at least a small local tsunami. For a large ocean crossing killer to be generated, a large land mass under the water must move up or down in order to displace a large volume of water. This is most common in subduction zones, where one tectonic plate slides under or over the other. If a strike-slip quake occurs, the land moves from side to side. This does not displace much if any water and therefore any tsunami is likely to be small and local.
