Calibrating seismometers by means of earthquake data

Recordings of earthquakes were used to calculate the magnification of ground motion produced by various seismometers. The calculations were based upon die 'A' values (energy parameters) listed by Gutenberg for seismic waves P, PP, and S. Results of the calibration procedure indicate that the energy content of P, PP, and S waves recorded on Benioff instruments increases with increasing wave period. In order to calibrate the horizontal seismometers by use of recorded longitudinal waves, it is necessary to correct for the fact that the amplitudes recorded transverse to the direction of wave propagation are appreciable. The resultant calibrations were accurate enough to be used for a subsequent study of the energy content of seismic waves.