How do we measure the intensity of earthquakes?

The intensity of an earthquake is measured by recording the tremors of the Earth’s surface with a ‘seismograph’. These tremors appear when the earthquake waves reach the surface of the Earth. Such a seismograph consists of a large, inert weight, which stays at rest even during earthquakes. A pen is attached to this pendulum. When the Earth trembles, the surface of the Earth, together with the paper placed there, moves to and fro below the ‘writing pendulum’ which does not move. We can then detect the different types of waves on the paper, which move at different speeds. The intensity of the earthquake can be calculated from these wave patterns. The intensity is measured on a scale, called ‘Richter scale’, named after its inventor. Earthquakes with an intensity of 2.5 can be felt, but ones with an intensity of 8.0 are very destructive.