Richter magnitude scale against the distance, and found a series of curves that showed a rough correlation with the estimated magnitudes of the earthquakes. Richter resolved some difficulties with this method, then, using data collected by his colleague Beno Gutenberg, produced similar curves, confirming that they could be used to compare the relative magnitudes of different earthquakes. To produce a practical method of assigning an absolute measure of magnitude required additional developments. First, to span the wide range of possible values Richter adopted Gutenberg's suggestion of a logarithmic scale, where each step represents a tenfold increase of magnitude, similar to the magnitude scale
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