Bass ackwards.
But also right on the money. The amount of water displaced has to be displaced a certain way, which means there are degrees of efficiencies of conversion from water displacement to wave formation.
The energy released from the quake itself that gets converted to wave energy will determine how much water gets displaced by the event. The conversion of quake energy released to wave energy traveling in the water column is dependent on depth of the quake, type of rock structure, as well as type of the quake. IIRC, depth is second most important behind type, and rock structure really only comes into play in coastal regions where tsunami formation isn't that probable. The San Francisco quake was so damaging because a lot of San Fran sits on unstable soil. Its like when you "pat" sand on the shoreline to the point it liquifies. Same thing happened in San Francisco. The waves of that particular quake caused "liquefaction" of the subsoil layers.
Type:
A strike/slip fault earthquake in which the ocean floor slides laterally usually doesn't (usually being the operative word) have the same effect as a subduction fault where the ocean floor actually jumps upwards. IIRC, the Indonesia quake epicenter caused the ocean floor to jump both upwards by about 6-8 meters and slide laterally about the same amount. The jump of the ocean floor is what caused that bad boy to do the damage it actually did.
Think about having two bricks underwater in a swimming pool. Move them past each pretty quick about 3 feet under water, and not much happens. Now take one of those bricks and push it three foot to the surface, from three foot down. That produces a lot of displacement energy upwards, which is a more efficient quake to wave motion conversion process.
Now strike slip lateral quakes can be devastating as well, but it really matters how the fault is aligned to nearby land masses.
EDIT: Calling it "wave energy/mass" isn't a good way to describe it. It's simply wave energy, there is no mass. There are only two water masses that move: directly above the quake, and it really doesn't go anywhere per se, and the water on the coastal areas where the underwater wave height begins to interact with the ocean floor.
Second edit: There are two uses of the word "wave" that will get confusing. "Wave" energy isn't a surface "wave" like you're thinking of. Its the sinusoidal movement of energy, that travels in waves. When it gets close to shore, do you ever begin to see the actual surface "wave" that surfers ride, but that is actually the wave energy pushing the water up. The energy wave propagated at the event epicenter offshore shows no surface wave, until it nears shore. I read this again, and I can see where that could be confusing to some.
