In this work we report the ongoing characterization of the Sos Enattos former mine (Sardinia, Italy), one of the two candidate sites for the Einstein Telescope (ET), the European third-generation underground interferometric detector of Gravitational Waves. The Sos Enattos site lies on a crystalline basement, made of rocks with good geomechanical properties, characterized by negligible groundwater. In addition, the site has a very low seismic background noise due to the absence of active tectonics involving Sardinia. Finally, the area has a low population density, resulting in a reduced anthropic noise even at the ground level. This location was already studied in 2012-2014 as a promising site for an underground detector. More recently, in March 2019, we deployed a new network of surface and underground seismometers at the site, that is currently monitoring the local seismic noise. Most of the energy carried by the seismic waves is due to the microseisms below 1 Hz, showing a significant correlation with the waves of the west Mediterranean sea. Above 1 Hz the seismic noise in the underground levels of the mine approaches the Peterson’s low noise model. Exploiting mine blasting works into the former mine, we were also able to perform active seismic measurements to evaluate the seismic waves propagation across the area. In conclusion we also give a first assessment about the acoustic and magnetic noise in this underground site.
<p>Seismic noise recorded by a temporary array installed around Pozzo Pitarrone, NE flank of Mt. Etna, have been analysed with several techniques. Single station HVSR method and SPAC array method have been applied to stationary seismic noise to investigate the local shallow structure. The inversion of dispersion curves produced a shear wave velocity model of the area reliable down to depth of about 130 m. A comparison of such model with the stratigraphic information available for the investigated area shows a good qualitative agreement. Taking advantage of a borehole station installed at 130 m depth, we could estimate also the P-wave velocity by comparing the borehole recordings of local earthquakes with the same event recorded at surface. Further insight on the P-wave velocity in the upper 130 m layer comes from the surface reflected wave observable in some cases at the borehole station. From this analysis we obtained an average P-wave velocity of about 1.2 km/s, compatible with the shear wave velocity found from the analysis of seismic noise.</p>
Volcanic eruptions have important social and economic impacts. They can affect local population near active volcanoes (e.g., Horwell et al., 2017), causing loss of life, damage to infrastructure, and disruption to aviation (e.g., Barnard, 2004;Poret, Corradini, et al., 2018;. The fallout of ballistics in areas close to erupting vents represents a hazard to tourists that visit volcanoes every year (e.g., Andronico et al., 2021). Volcanoes with multiple active vents pose additional significant monitoring challenges owing to the rapid changes frequently observed in both the location and style of eruptive activity (e.g.
In this work, the reduction of seismic hazard in eastern Sicily is addressed by both studying the fundamental resonant frequency of strategic buildings through low cost geophysical investigation techniques, and exploring a practical approach to earthquake early warning EEW) system. The fundamental period and the corresponding amplification of some selected strategic buildings has been estimated using ambient vibration and earthquake data. We analyzed the basic dynamic parameters of buildings chosen as target, by using continuous vibration measurements at different floors. The dynamic behavior of structures was evaluated considering both small strains induced by ambient vibrations and larger excitation levels due to the earthquakes occurrence. A practical approach to earthquake early warning in the investigated area was dealt with by using empirical relationships between parameters measured on the initial portion of seismic recordings and related to the earthquake magnitude and peak ground motion. In particular, we performed the first preliminary tests by using empirical relationships calibrated for the considered area and taking into account the geometry of the existing permanent seismic network deployed in the eastern Sicily. The estimated relationships have been used to provide onsite warning around a given seismic station and evaluate the potential damaging effects. The joint of EEW system and geophysical investigation shown in this work may be deemed a useful guide for the future implementation of the in real time seismic monitoring in the region. FIGURE 1. Pictures of the strategic buildings chosen for this study: (a) Osservatorio Etneo (Catania); (b) Dipartimento Protezione Civile (Messina); (c) Scuola Nazario Sauro (Catania); (d) Scuola M. T. Calcutta (Tremestieri Etneo).
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