GNGTS 2022 - Atti del 40° Convegno Nazionale

374 GNGTS 2022 Sessione 2.2 low frequencies is essentially linked to a better thermal stability of the sensor, therefore to a reduction of the instrumental self-noise. The power is reduced also above 2 Hz, and even more clearly above 10 Hz. At high frequencies, the noise reduction is essentially linked to the physical attenuation of the wavefield. In the band between 0.3 Hz and 2 Hz the power is almost identical. Fig. 3 - Left: a comparison between the acceleration power spectral densities (24 hours signal) for the vertical components at FAVA site (62.5 m deep); red line: surface sensor; blue line: posthole sensor. Right: a micro-crack (red arrow) triggers a low-frequency asymmetric oscillation at LIBRI site (27 m deep). Conclusion. The upgrade of the earthquake monitoring network in Sicily thanks to the GRINT project represents a main advancement that makes the infrastructure more efficient, reliable, and sustainable for the next decade. In particular, the integration of the posthole seismometers will provide better quality data which will enhance a variety of high-quality seismological studies and will better support the Istituto Nazionale di Geofisica e Vulcanologia in the seismic surveillance of this region characterized by the highest seismic hazard of the whole Italy. References . D’Alessandro A., D’Anna R., Di Gangi F., Passafiume G., Scudero S., Speciale, S., Vitale G., Bignami Christian, Piersanti A., Cannelli V., Galli G., Mineo R., Alessandro G., Buonmestieri S., Rao S. and Stramondo S.; 2021: Sullo sviluppo della rete multiparametrica in Sicilia. Quaderni di Geofisica, 172, pp. 1-40. Greig W., Spriggs N. and Bainbridge G.; 2014: Comparison study between vault seismometers and posthole seismoter. 2nd European Conference Of Earthquake Engineering And Seismology, Istanbul, 25-29 August 2014. Hayman, M. B. ; 2014: Downhole Seismometers . Encyclopedia of Earthquake Engineering, pp .1-22. Hutt C. R., Ringler A. T. and Gee L. S.; 2017: Broadband Seismic Noise Attenuation versus Depth at the Albuquerque Seismological Laboratory. Bull. Seismol. Soc. Am., 107(3), pp. 1402-1412. Lin Y. Y., Chen D. Y., Kuo C. H., Lin C. J., Chen W. Y. and Wen Y. Y.; 2022: Orientation Corrections of a Borehole Seismometer Network in Taiwan Using Teleseismic Earthquakes. Seis. Res. Lett. Withers M. M., Aster R. C., Young C. J. and Chael, E. P.; 1996: High-frequency analysis of seismic background noise as a function of wind speed and shallow depth . Bull. Seismol. Soc. Am., 86(5), pp. 1507-1515.