How is an earthquake's magnitude measured on Richter scale?

An earthquake's magnitude, determined using a seismograph, quantifies the energy released at the source of the earthquake. Firstly, the time between the arrival of the primary and secondary tremor is measured, which gives the distance from epicentre. The epicentre distance and height of the largest secondary tremor on the seismogram, when connected on the Richter scale, quantify the magnitude.