We calibrated 64 Mark Products L22-D short-period geophones of the IRIS/PASSCAL Array using a mass-displacement test. The mean natural frequency of the 192 components was 2.1 Hz (slightly larger than the nominal value of 2 Hz) with a standard deviation of about +/- 0.15 Hz. The standard deviation of the voltage sensitivity is about +/- 5 per cent. Variability of both sensitivity and natural period are within the manufacturer's published specifications. Three types of nonlinearities were noted: a 5 per cent difference in parameters determined by positive and negative mass-displacements, possibly due to a nonlinear spring (observed on more than 90 per cent of the 192 components tested); apparent cross-axis errors in wide (1 to 2 Hz) bands near 10 Hz; and spurious resonance peaks at frequencies between 22 and 29 Hz (observed on about 20 per cent of the components). Array equalization of seismograms from the Loma Prieta earthquake aftershock survey indicate that the root mean square misfit between two seismograms recorded by different geophones at the same site can be reduced from approximately 10 per cent to approximately 5 per cent by application of the calibration results.
Ey811Times Cited:13Cited References Count:2