The transfer function of a short-period vertical seismograph

Abstract

We locate the poles and zeros of the transfer function of a seismograph which consists of the Geotech Model 1051 Benioff vertical seismometer and the Geotech Model 4500 galvanometer-phototube amplifier with a 5 cps galvanometer. A weighted least squares fit to the measured frequency response of the seismometer, assuming a damping ratio of 17 to 1, gives for the pole locations of the seismometer transfer function: - 10 . 539 ; - 5 . 787 + i 7 . 407 ; - 5 . 787 - i 7 . 407 There is a triple zero at the origin. The overall seismograph transfer function has additional poles at - 22 . 21 + i 22 . 21 ; - 22 . 21 - i 22 . 21 ; - 0 . 06283 ; - 29 . 62 + i 29 . 62 ; - 29 . 62 - i 29 . 62 ; an additional zero at the origin, and a quadruple zero at infinity. an additional zero at the origin, and a quadruple zero at infinity.