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The NEWTON-g project [1] proposes a paradigm shift in terrain gravimetry to overcome the limitations imposed by currently available instrumentation. The project targets the development of an innovative gravity imager and the field-test of the new instrumentation through the deployment at Mount Etna volcano (Italy). The gravity imager consists in an array of MEMS-based relative gravimeters anchored on an Absolute Quantum Gravimeter [2].The Absolute Quantum Gravimeter (AQG) is an industry-grade gravimeter measuring g with laser-cooled atoms [3]. Within the NEWTON-g project, an enhanced version of the AQG (AQGB03) has been developed, which is able to produce high-quality data against strong volcanic tremor at the installation site.After reviewing the key principles of the AQG, we present the deployment of the AQGB03 at the Pizzi Deneri (PDN) Volcanological Observatory (North flank of Mt. Etna; 2800 m elevation; 2.5 km from the summit active craters), which was completed in summer 2020. We then show the demonstrated measurement performances of the AQG, in terms of sensitivity and stability. In particular, we report on a reproducible sensitivity to gravity at a level of 1 μGal, even during intense volcanic activity.We also discuss how the time series acquired by AQGB03 at PDN compares with measurements from superconducting gravimeters already installed at Mount Etna. In particular, the significant correlation with gravity data collected at sites 5 to 9 km away from PDN proves that effects due to bulk mass sources, likely related to volcanic processes, are predominant over possible local and/or instrumental artifacts.This work demonstrates the feasibility to operate a free-falling quantum gravimeter in the field, both as a transportable turn-key device and as a drift-free monitoring device, able to provide high-quality continuous measurements under harsh environmental conditions. It paves the way to a wider use of absolute gravimetry for geophysical monitoring.[1] www.newton-g.com[2] D. Carbone et al., “The NEWTON-g Gravity Imager: Toward New Paradigms for Terrain Gravimetry”, Front. Earth Sci. 8:573396 (2020)[3] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)

The field of rotational seismology has only recently emerged. Portable 3 component rotational sensors are commercially available since a few years which opens the pathway for a first use in volcano-seismology. The combination of rotational and translational components of the wavefield allows identifying and filtering for specific seismic wave types, estimating the back azimuth of an earthquake, and calculating local seismic phase velocities.Our work focuses on back-azimuth calculations of volcano-tectonic and long-period events detected at Etna volcano in Italy. Therefore, a continuous full seismic wavefield of 30 days was recorded by a BlueSeis-3A, the first portable rotational sensor, and a broadband Trillium Compact seismometer located next to each other at Mount Etna in August and September of 2019. In this study, we applied two methods for back-azimuth calculations. The first one is based on the similarity of the vertical rotation rate to the horizontal acceleration and the second one uses a polarization analysis from the two horizontal components of the rotation rate. The estimated back-azimuths for volcano-tectonic events were compared to theoretical back-azimuths based on the INGV event catalog and the long-period event back-azimuths were analyzed for their dominant directions. We discuss the quality of our back azimuths with respect to event locations and evaluate the sensitivity and benefits of the rotational sensor focusing on volcano-seismic events on Etna regarding the signal to noise ratios, locations, distances, and magnitudes.

Rotational seismology is an emerging field of seismology with rotational sensors such as blueSeis-3A as portable devices. We deployed one of these rotational sensors on Etna volcano from August to September 2019 in the middle of a 26 stations broadband seismic array and a fibre-optic cable deployed for Distributed Acoustic Sensing (DAS). We, therefore, recorded continuously the full seismic wavefield using a 6C station (rotational sensor co-located with a broadband seismometer) for 30 days.We will present an overview of our work on the rotational data in combination with a broadband seismometer. We will (i) compare the translational with rotational data and show how they complement each other, (ii) calculate back azimuths using only a 6C station or using merely the horizontal components of the rotational sensor, (iii) determine Love and Rayleigh wave velocities from the rotation rate and (iv) perform a simple inversion for the shallow velocity structure below the station, and finally (v) discuss the usefulness of such a sensor in a volcanic environment and (vi) highlight what new it would bring to volcano-related research.

In the framework of EUROVOLCs Trans-national grants, we propose the FAME project aiming at validating Distributed Acoustic Sensing (DAS) technology as a complementary and alternative tool for monitoring volcanic and seismic activity at Etna volcano. DAS technology provides records of strain signals with unprecedented spatial and temporal resolution.We deployed a fibre optic cable connected to an iDAS (Silixa) interrogator set-up at the Observatory Pizzi Deneri in the summit area. To allow for a continuously recording of the iDAS, a solar panel power system was designed using battery back-up and inverter to supply 200 W at 220 V/AC. An internet connection was set up for a full remote control capability. The iDAS interrogated a 1.5 km long fibre cable, buried at a depth of about 30 cm by digging a trench in Piano delle Concazze area. The DAS measurements were validated with conventional measurements from 26 broadband seismometers and 3 arrays of 3 infrasound sensors from the Geophysical Instrument Pool Potsdam (GIPP). We deployed instruments along the fibre optic cable, covering an area of about 0.1 km2. The DAS and conventional sensors acquired data from 4 July to 23 September 2019 without major interruptions.Here, we show key features of this the extraordinary multidisciplinary dataset. Thanks to the high spatial resolution (2 m), we could find locations of hypothesized faults in Piano delle Concazze area. Thanks to the long acquisition period, we continuously tracked Etna activity, marked by several eruptive episodes, including ash emissions, strombolian and effusive activities from the summit craters. The most intense and sustained eruptive events occurred in 18-20 July, 27-28 July and 9-13 September. We investigate the application of well-established analysis techniques in volcano-seismology to DAS dataset in order to assess the performance of the system in detecting and characterizing volcanic events.Our findings demonstrate that DAS technology can record on a long term basis volcanic activity, which suggests DAS technology can be integrated to volcanic monitoring systems.

Results of passive seismic surveys, in terms of both amplification and polarization effects in a section of the Tremestieri Etneo Fault (Sicily Eastern center - Catania) are discussed. For the purpose, velocimetric and accelerometric records of seismic ambient noise were analyzed. The polarization analysis of particle motion was performed and azimuthally dependent resonant frequencies were estimated. Ambient noise data were also used to assess the dynamic properties of a reinforced concrete building, located on the fault zone. The fundamental modes have been estimated through ambient noise recordings acquired by three-directional accelerometers, installed at the highest accessible floor and outside the building. The study revealed a clear oriented seismic amplification in the fault zone. This effect was observed in intensely jointed rock masses, located inside the fault area, as the result of specific geometries and significant directional impedance contrasts characterizing the area under study. The analyses show that the direction of the largest resonance motions has transversal relationship with the dominant fracture orientation. The directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone, with larger seismic motions high angle to the fractures. The results obtained are in complete agreement with those obtained by a previous study which analyzed the fault section located to the north-west. Finally, comparing the dynamic properties of the school building and the vibrational characteristics of the soil in the direction of maximum amplification, no clear resonant effect in the soil-structure interaction has been observed.