yeswey, the definition for earthquake has been provided on the original conversation. A new answer is only acceptable if there are additional information.

But i think they are different in wording. Whats more, there is no citing source in the previous answer.

yeswey, it is basically the same answer. The original answer is from 2011, before the rule that all answers need a source.

I'd like to put in a word of support for yeswey. His inclusion of "rocks in the Earth's crust" is much more explicit and scientific than "ground", so I think his answer does add more information.

Thank you Janet17.