A note on upgrading long-period seismographs

Abstract

Signals generated by old-fashioned electromagnetic long-period seismometers can be digitized using low-cost electronics. We developed electronic hardware, including a calibration section, to digitize signals of a three-component long-period station. Software to decode and monitor the incoming signals on a PC was developed. The frequency response curve obtained is similar to curves of long-period stations of the World Wide Standardized Seismograph Network for a natural period of 15 s. Good quality digital long-period data have been obtained since November 1996.