Earthquake magnitude determination from the vertical component of surface waves

An earthquake magnitude formula, giving the closest possible fit to magnitudes of Gutenberg and Richter [1949], is developed for the vertical component of surface waves with periods of about 20 sec from records at Pasadena. The magnitude is obtained as the sum of five terms. The first term takes account of the amplitude, the second accounts for the amplitude variation with epicentral distance, the third accounts for depth of earthquake focus (down to 100 km), the fourth is the regional correction, depending on the properties of the path of the surface waves, and the fifth corrects for the fact, verified here, that the ratio of vertical to horizontal amplitudes of surface waves varies with the magnitude. It is not possible to obtain the magnitude from the records at one station to a higher accuracy than ± ¼.