On Thu, 06 Jan 2005 17:36:17 +0000, griz wrote:

Does this mean that in the common use they are synonymous,
Yes.

...but only tsunami is really caused by earthquakes?

No. Tidal waves can also be caused by earth/seaquakes, or my not be.
Similarly a tsunami (note definition "esp one caused by an earthquake")
especially but not necessarily.
--
Tim C.