Qualitative measure of earthquake intensity, it is a linear empirical scale based on the observed effects of seismic phenomenon. It indicates earthquake intensity on a scale I to XII (Roman numerals are used to avoid confusion with Richter scale which measures earthquake magnitude). Devised in 1902 by the Italian geologist Giuseppe Mercalli (1850-1914). Its US version (called Modified Mercalli) was developed in 1956 by Charles Richter.