New tunable mechanical monolithic horizontal seismometer for low frequency seismic noise measurement

This paper describes a version of the mechanical horizontal monolithic sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric-discharge-machining, that can be used both as seismometer and, in a force feedback configuration, as accelerometer. It is a very compact instrument, very sensitive in the low-frequency seismic noise band, with a very good immunity to environmental noises, whose main characteristics are the tunability of the resonance frequency, a high mechanical quality factor and a very sensitive interferometric readout. In this paper we describe the results of the first tests performed on this new instrument, comparing the results with a previous version of the instrument