A digital seismograph system for measuring earth noise

Abstract

A digitally recording seismograph station has been installed to record and study earth noise in the frequency range of 0.01 to 1 cps. The system is capable of recording four channels of information plus time on paper tape at sample rates of up to three times per second with a dynamic range of 90 db. Preliminary analyses of the digital records show that the spectral peak between 0.1 and 0.2 cps exhibits properties consistent with Rayleigh waves arriving from the southwest mixed with isotropic noise.