Seismic System Calibration : 2 . Cross - Spectral Calibration Using Random Binary Signals

We present a rapid and accurate method of calibrating seismic systems using a random binary calibration signal and cross-spectral techniques. The complex transfer function obtained from the cross spectrum is least-squares fit to the ratio of two polynomials in s(s-i~) whose degrees are determined by a linear systems analysis. This provides a compact representation of the system frequency response. We demonstrate its application to two seismic systems, the IDA and SRO seismometers. This method yields calibrations to an accuracy of better than 1 per cent in amplitude and 1 ° in phase.