Magnitude and Intensity of an Earthquake

An earthquake is measured by its Magnitude and Intensity. The Magnitude indicates the amount of energy released at the source (or epicentre) and is measured by the open-ended Richter Scale.

The intensity of an earthquake at a particular locality indicates the violence of earth motion produced there by the earthquake. It is determined from reported effects of the tremor on human beings, furniture, buildings, geological structure, etc. Many places, including Hong Kong, have adopted the Modified Mercalli Scale (MMS) which classifies earthquake effects into twelve grades.