technically any earthquake can be said to consist of earth tremors, as the word tremor simply means shaking. However, it is generally accepted that the phrase earth tremor should relate only to smaller earthquakes, i.e. those of low magnitude and intensity. These would ordinarily cause little or no damage but may have a greater impact if they come in the immediate aftermath of a high magnitude and intensity earthquake which has already weakened and destabilized many structures. Where the line should be drawn is not agreed.
Geography Dictionary & Glossary for Students \\ ITS Tutorial School (ITS) - Hong Kong.