While the term Earthquake refers to seismic activity on this planet, earthquake is an interchangeable term used with groundquake, seismic activity, tremor, and tetonic plate shifting to describe the phenomena on other celestial objects. For specific objects, the word Earth is replaced with the planet's name, so it would be called a Marsquake. Similar activity on the satellites of planets, however, would be called moonquakes as well as the aforementioned generic terms.
Notice that there is a difference in capitalization in the word earthquake and Earthquake. That differentiates the difference of proper noun versus verb or pronoun.