Charles Francis Richter was an American born seismologist and probably one of the most recognizable names in the field in the 20th century. Born in 1900, he actually studied physics in college but became fascinated with seismology and the study of movements in the Earth's crust and started his career at the Carnegie Institute. He soon moved to the California Institute of Technology where he remained as a professor for the rest of his career. He died in 1985.
Richter is most famous for the development of the first seismograph and the resulting scale to quantify the relative strength of earthquakes. In the 1930's, he and colleague Beno Gutenberg developed the first device for quantitatively measuring movements in the Earth's crust during an earthquake and called it a seismograph. Before this, earthquakes were measured on a scale based purely on subjective observations. With a seismograph, Richter and Gutenberg developed a logarithmic scale to quantify earthquakes, meaning an increase in the numerical scale by one integer represents a ten-fold increase in intensity. For whatever reason, popular history associated only Richter's name with the inventions.
Richter actually published very little, but among his body of work are two books, one in 1941 titled Seismicity of the Earth (with Gutenberg) and the other in 1958 titled Elementary Seismology. Richter was also involved later in his career with helping to develop more modernized building codes in California to better withstand earthquakes and help prevent structural damage and deaths.