The first reported use of any measurement of earthquake intensity was attributed to the Italian Schiantarelli, who recorded the intensity of the 1783 earthquake that occurred in Calabrian, Italy ,but the first actual richter scale i believe was invented in 1935 by Charles Richter.
The Richter scale was first introduced in the year 1935 by Charles Francis Richter (April 26, 1900 – September 30, 1985). He was an American seismologist and physicist. Richter magnitude scale is used to quantify the size of earthquakes. He developed it in collaboration with Beno Gutenberg; as both worked at California Institute of Technology, California, USA