Seismic background noise dramatically decreased as a result of lockdown measures in place for mitigating the spread of COVID-19.

We present an improved rendition of the geodetic velocity and strain fields in Sicily and southern Calabria obtained through the analysis of 18 years of GPS observations from continuous and survey station networks. The dense spatial coverage of geodetic data provides precise quantitative estimates of previously established first‐order active kinematic features, including: i) a narrow east‐west‐elongated belt of contraction (∼1–1.5 mm/yr) extending offshore northern Sicily from Ustica to Stromboli across the Aeolian Islands; ii) a narrow east‐west‐trending contractional belt located along the northern rim of the Hyblean Plateau in southern Sicily, with shortening at up to 4.4 mm/yr; iii) right motion (∼3.6 mm/yr) on the Aeolian‐Tindari‐Letojanni fault (ATLF) system, a main shear zone extending from the Aeolian Islands to the Ionian coast of Sicily, with significant transpression and transtension partitioned between discrete sectors of the fault; iv) transtension (∼1 mm/yr) across the Sicily Channel between Sicily and North Africa. We use geodetic observations coupled to geological constraints to better elucidate the interplay of crustal blocks revealed in the investigated area. In particular, we focus on the ATLF, which forms the primary boundary between the Sicilian and Calabrian blocks. The ATLF juxtaposes north‐south contraction between Sicily and the Tyrrhenian block with northwest‐southeast extension in northeastern Sicily and Calabria. Contraction between Sicily and Tyrrhenian blocks probably arises from the main Europe‐Nubia convergence, although Sicily has a component of lateral motion away from Nubia. We found that convergence is not restricted to the northern offshore, as commonly believed, but is widely accommodated between the frontal belt and the northern rim of the Hyblean foreland in southern Sicily. Geodetic data also indicate that active right shear on the ATLF occurs to the southeast of the mapped fault array in northern Sicily, suggesting the fault cuts through till the Ionian coast of the island. The small geodetic divergence between the Hyblean and Apulian blocks rimming on both sides the Calabria block and subjacent Ionian slab, coupled with marine geophysical evidences in the Ionian Sea lends credit to the proposed deep root of the ATLF and to a fragmentation of the Ionian domain.

Lava fountains have a major impact on the local population since they cause ash plumes that spread several kilometers above and hundreds of kilometers away from the crater. Ash fallout is responsible for disrupting airports and traffic on the motorways well beyond the area of the volcano itself, as well as affecting the stability of buildings and causing public health issues. It is thus a primary scientific target to forecast the impact of this activity on local communities on the basis of parameters recorded by the monitoring network. Between 2011 and 2015, 49 paroxysmal explosive episodes occurred at two of Mt Etna's five summit craters: the New South-East Crater (NSEC) and the Voragine (VOR). In this paper, we examine the features of the 40 episodes occurring at the NSEC during 2011–2013, and of the 4 events at VOR in December 2015. We study these paroxysms using geophysical monitoring data, characterize the episodes, and analyse all available data statistically. Our main results are two empirical relationships allowing us to forecast the maximum elevation of the ash plume from the average height of the lava fountain, useful for hazard assessment and risk mitigation. For Etna, and using the examples described in this paper, we can infer that wind speed 10 m s⁻¹ is normally associated with weak plumes, bent-over along the wind direction and reaching lower elevations.

Seismic, deformation, and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment. In spite of their wide use, there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques. Here we combine seismic (volcanic tremor and long‐period seismicity), deformation (GPS), and geochemical (volcanic gas plume CO₂/SO₂ ratios) measurements in an attempt to interpret trends in the recent (2007–2008) activity of Etna volcano. We show that each eruptive episode occurring at the Southeast Crater (SEC) was preceded by a cyclic phase of increase‐decrease of plume CO₂/SO₂ ratios and by inflation of the volcano's summit captured by the GPS network. These observations are interpreted as reflecting the persistent supply of CO₂‐rich gas bubbles (and eventually more primitive magmas) to a shallow (depth of 1–2.8 km asl) magma storage zone below the volcano's central craters (CCs). Overpressuring of the resident magma stored in the upper CCs' conduit triggers further magma ascent and finally eruption at SEC, a process which we capture as an abrupt increase in tremor amplitude, an upward (>2800 m asl) and eastward migration of the source location of seismic tremor, and a rapid contraction of the volcano's summit. Resumption of volcanic activity at SEC was also systematically anticipated by declining plume CO₂/SO₂ ratios, consistent with magma degassing being diverted from the central conduit area (toward SEC).