If an earthquake happens on Mars, is it still an earthquake? Or are seismic phenomenon named differently when they happen on other celestial bodies? If so, what are they called?
As pointed out in the comments, some do prefer to use different terms for quakes on other bodies, and you can see here that "marsquake" does have scholarly usage. That said, there is also scholarly usage for "earthquake" in this context. If you think about it, this makes sense given that one definition of "earth" is "the substance of the land surface", i.e. the ground. This definition of "earth" is agnostic to which terrestrial planet the land surface is on.