Wikianswers gives a delightful answer to this question:
"Unfortunately the romans weren't very knowledgable and for example had no word for Volcano. They probably gave it a generic term such as Tragedy."Hilarious! (It would be nice if this anonymous contributor was shot against a wall by a firing squad.) A more mature answer is easy to find on the Perseus website simply by looking up 'earthquake' in their Latin dictionary.
To the contrary, we see that the Romans had several terms at their disposal describing in much detail the accompanying features of their seismic tragedies. Aside from generic concussio, other terms are borrowed from Greek:
epiclintae= an earthquake with horizontal motionAfter being curious myself about what Romans called an earthquake, I find my curiosity only increasing. I wonder how much of these precise terms for 'earthquake' were encouraged by the obsessive study of divination and prophecy maintained by the Etruscans who had, afterall, founded Rome and who made thorough books about their oracular findings much like their Babylonian precedents.
mycetias = a rumbling earthquake
ostes = an earthquake with one violent shock
palmatias = a slight earthquake
rhēctae = an earthquake that breaks the earth into fissures