Charles Francis Richter developed a logarithmic scale to measure intensity. The name "magnitude" for this measurement came from Richter's childhood interest in astronomy - astronomers measure the intensity of stars in magnitudes. Gutenberg's contribution was substantial, but his aversion to interviews contributed to his name being left off the scale. After the publication of the proposed scale in 1935, seismologists quickly adopted it for use in measuring the intensity of earthquakes. Richter remained at the Carnegie Institute until 1936, when he obtained a post at the California Institute of Technology, where Beno Gutenberg worked. Gutenberg and Richter published "Seismicity of the Earth" in
Seismic magnitude scales times. As originally defined by m was based on the maximum amplitude of waves in the first 10 seconds or more. However, the length of the period influences the magnitude obtained. Early USGS/NEIC practice was to measure on the first second (just the first few P-waves), but since 1978 they measure the first twenty seconds. The modern practice is to measure short-period scale at less than three seconds, while the broadband scale is measured at periods of up to 30 seconds. The regional mb scale – also denoted mb_Lg, mbLg, MLg (USGS), Mn, and m – was developed by for