Seismographs record the amplitude of the waves from an earthquake, which are then used in a logarithm to calculate the quake's size. Adjustments to the measurements are made for various factors including distance from the seismograph and the quake's epicenter. The largest earthquake recorded, as of January 2015, is the Great Chilean Earthquake. The 1960 quake registered a 9.5 on the Richter Scale.
The Richter Scale is rarely used anymore since the creation of the moment magnitude scale. The scale is more accurate in determining size.Learn more about Earthquakes