Compact tunable monolithic sensors for vibration monitoring and control of structures and very low frequency – large band characterization of sites

In this paper we describe a new mechanical implementation of a horizontal monolithic folded pendulum inertial sensor, configurable as low-frequency large-band seismometer and/or accelerometer, for seismic monitoring (strong motion and seismic noise characterization) and for monitoring and control of scientific, civil and industrial structures, also in difficult environmental conditions (mines, dangerous conditions, high vacuum, low temperature and cryogenic environment). The very large measurement band (〖10〗^(-7)÷10 Hz), low readout noise <〖10〗^(-8) m/√Hz in the band (0.01 ÷10 Hz) with laser optical lever readout and <〖10〗^(-12) m/√Hz in the band (0.01 ÷10 Hz) with laser interferometric readout) are its main characteristics. Moreover, scalability, compactness (l <15 cm), light weight (<2 Kg), tunability down to ≈66 mHz and high quality factor (>1500 in air) are other very relevant features. In the paper, after a general description of the seismometer, we present and discuss preliminary scientific data recorded in the INFN Gran Sasso National Laboratory (LNGS).