/knows a bit of geology but doesn't know Japanese.
Tectonic plates are huge chunks of the Earth's crust that "floats" over the mantle (magma/molten rock), somewhat similar to the sheety stuff that floats over the coffee with milk. (how do you call that in english?)
Crustal deformation is the deformation of the crust that can occur due to the shifting of the tectonic plates (can be caused by other stuff, but I'll keep it simple). For example, in some parts of Earth, this huge chunks of "floating" crust are constantly "ramming" against each other (
this). A whole lot of different types of crust deformation occurs at this "subduction zones", including the formation of mountain ranges, folding of rocks, etc. Earthquakes and formation of volcanoes are highly related to this kind of events btw.
In other words, crustal deformation is just a general term that refers to different types of rock/crust deformation (folding, faulting etc). This deformation is caused by other events such as plate tectonic activity, volcanism, intrusions and even glaciers or meteorite impacts.
Imo, Ea having enough power to cause crustal deformation is hardly "planet killer" force. Unless the dude deforms the crust and makes it store so much energy that the earthquake produced by that thing would knock out Earth out of orbit thus changing Earth's distance to the sun thus destroying the atmosphere thus... well, you get the idea. And even then, at worst Earth would become another Mars. Gilgamesh would need to ram Earth against another planet to actually destroy Earth.