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The real-time monitoring of densely populated areas with high seismic and volcanic risk is of crucial importance for the safety of people and infrastructures. When an earthquake occurs, the Earth surface experiences both translational and rotational motions. The latter are usually not monitored, but their measurement and characterization are essential for a full description of the ground motion. Here we present preliminary observational data of a high-sensitivity rotational sensor based on a 2-km-long fiber-optic Sagnac gyroscope, presently under construction in the middle of the Campi Flegrei Volcanic Area (Pozzuoli, Italy). We have evaluated its performance by analyzing data continuously recorded during an acquisition campaign of five months. The experimental setup was composed of a digital nine-component seismic station equipped with both a rotational sensor and conventional seismic sensors (seismometers, accelerometers, and tiltmeters). During this experiment we detected seismic noise and ground rotations wavefield induced by small to medium local earthquakes ( M D <3). The prototype gyroscope shows a very promising sensitivity in the range of 5×10 -7 -8×10 -9 r a d / s / H z over the frequency bandwidth 5 mHz-50 Hz. Future upgrades and perspectives are discussed.

In August 2016, a magnitude 6.0 earthquake struck Central Italy, starting a devastating seismic sequence, aggravated by other two events of magnitude 5.9 and 6.5, respectively. After the first mainshock, four Italian institutions installed a dense temporary network of 50 seismic stations in an area of 260 km 2 . The network was registered in the International Federation of Digital Seismograph Networks with the code 3A and quoted with a Digital Object Identifier ( https://doi.org/10.13127/SD/ku7Xm12Yy9 ). Raw data were converted into the standard binary miniSEED format, and organized in a structured archive. Then, data quality and completeness were checked, and all the relevant information was used for creating the metadata volumes. Finally, the 99 Gb of continuous seismic data and metadata were uploaded into the INGV node of the European Integrated Data Archive repository. Their use was regulated by a Memorandum of Understanding between the institutions. After an embargo period, the data are now available for many different seismological studies.