Introduction

The Emilia seismic sequence that struck northern Italy on May-June 2012 had a relevant social, cultural, emotional and economical impact. There were 17 victims, and it caused severe damage in many localities, especially to the historical centers and factories. From the scientific point of view, the sequence represented an important case study and the whole geophysical community focused their attention on it. [...

Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italy

In this paper we report seismological evidence regarding the emplacement of the dike that fed the July 18 - August 9, 2001 lateral eruption at Mt. Etna volcano. The shallow intrusion and the opening of the eruptive fracture system, which mostly occurred during July 12, and July 18, were accompanied by one of the most intense seismic swarms of the last 20 years. A total of 2694 earthquakes (1 £ Md £ 3.9) were recorded from the beginning of the swarm (July 12) to the end of the eruption (August 9). Seismicity shows the upward migration of the dike from the basement to the relatively thin volcanic pile. A clear hypocentral migration was observed, well constraining the upwards propagation of a near-vertical dike, oriented roughly N-S, and located a few kilometers south of the summit region. Earthquake distribution and orientation of the P-axes from focal mechanisms indicate that the swarm was caused by the local stress source related to the dike intrusion

Preface

The Italian territory is vulnerable and is often affected by important natural phenomena. These are not always predictable, and we must learn to defend ourselves from them. In these days of 2012, the seismic events in northern Italy have severely stretched the social and industrial structure of one of the most productive areas of Europe, the richness of which derives from a special combination of natural, cultural, social and economic factors, which need to be carefully preserved and valued. Even the scientific community of the Earth sciences is called upon to take on this difficult task. Careful reflection of the ethical value and social impact of our studies can no longer be postponed, if we, as geoscientists, want to have an active role in society. [...]</p

Preface

This special issue of Annals of Geophysics contains seventeen peer-reviewed papers that cover a wide variety of topics related to the V3-LAVA Project funded by the Italian Dipartimento della Protezione Civile in the framework of the 2007–2009 Agreement with the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The frequent eruptions of Mount Etna can produce lava flows that can cover distances long enough to invade vulnerable areas on the flanks of the volcano. These require improvements to our forecasting tools for the effective assessment of lava-flow hazards, to help the local authorities to make the necessary decisions during a volcanic eruption. The LAVA Project aims to develop, validate and unify methods for mapping the areas around Etna that are threatened by lava invasion within the next 50 years, and also within the immediate days after an eruption has begun. […

Magma transport and storage at Mt. Etna (Italy): A review of geodetic and petrological data for the 2002–03, 2004 and 2006 eruptions

A detailed reconstruction of magma movements within the plumbing system of Mt. Etna volcano has been made by reviewing the eruptions occurring during the October 2002–December 2006 period. The availability of continuous GPS data allowed detecting at least ten different ground deformation stages, highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion. These data have been coupled with the available petrological datasets including major/trace elements and Sr-Nd-Pb isotope compositions for the volcanic rocks erupted in the 2002–2006 period. We identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano. The former is located at a depth of ~ 7 km bsl and fed the 2001 and 2002–03 eruptions, while the latter, located from 3.5 to 5.5 km bsl, fed the 2004–05 and 2006 eruptions. Petrological characteristics of emitted products have been correlated with the inflation vs. deflation cycles related to the identified sources, providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature. Finally, we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002–03 eruption, as a consequence of the major seaward motion of the eastern flank of the volcano.Published149-1645V. Dinamica dei processi eruttivi e post-eruttiviJCR Journa

Seismic vs. geodetic moments at Mt. Etna volcano: A tool for a rapid understanding the eruptive behaviour?

The seismic to geodetic moment ratio (Mo/MG) related to seven magma intrusion episodes, occurring at Mt. Etna volcano between 1981 and 2008, are considered. The lateral eruptions show a moment ratio of 0.04–0.06; meaning that only about 5% of the stress energy accumulated with ground deformation was released by earthquakes. Significantly higher values instead characterized vertical (0.25–0.50) and non-eruptive (0.17) dike intrusions. This paper proposes a simple relationship, in order to estimate, during the early phases of an eruption, the intruding magma volumes by the cumulative seismic moment (of the ongoing seismicity) and elapsed time.Published1-65V. Processi eruttivi e post-eruttiviJCR Journa

An improved evaluation of the seismic/geodetic deformation-rate ratio for the Zagros Fold-and-Thrust collisional belt

This article has been accepted for publication in Geophysical Journal International ©: The Authors 2018. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.We present an improved picture of the ongoing crustal deformation field for the Zagros Fold-and-Thrust Belt continental collision zone by using an extensive combination of both novel and published GPS observations. The main results define the significant amount of oblique Arabia–Eurasia convergence currently being absorbed within the Zagros: right-lateral shear along the NW trending Main Recent fault in NW Zagros and accommodated between fold-and-thrust structures and NS right-lateral strike-slip faults on Southern Zagros. In addition, taking into account the 1909–2016 instrumental seismic catalogue, we provide a statistical evaluation of the seismic/geodetic deformation-rate ratio for the area. On Northern Zagros and on the Turkish–Iranian Plateau, a moderate to large fraction (∼49 and >60 per cent, respectively) of the crustal deformation occurs seismically. On the Sanandaj–Sirjan zone, the seismic/geodetic deformation-rate ratio suggests that a small to moderate fraction (<40 per cent) of crustal deformation occurs seismically; locally, the occurrence of large historic earthquakes (M ≥ 6) coupled with the high geodetic deformation, could indicate overdue M ≥ 6 earthquakes. On Southern Zagros, aseismic strain dominates crustal deformation (the ratio ranges in the 15–33 per cent interval). Such aseismic deformation is probably related to the presence of the weak evaporitic Hormuz Formation which allows the occurrence of large aseismic motion on both subhorizontal faults and surfaces of décollement. These results, framed into the seismotectonic framework of the investigated region, confirm that the fold-and-thrust-dominated deformation is driven by buoyancy forces; by contrast, the shear-dominated deformation is primary driven by plate stresses.Published194-2092T. Deformazione crostale attivaJCR Journa

Insights into lava fountain eruptions at Mt. Etna by improved source location of the volcanic tremor

We analysed volcanic tremor recorded during ten lava fountain eruptions at Mount Etna volcano over the second half of 2011. The seismic signal, recorded by a network of 19 broadband stations, was corrected for site effects. The site amplification factors obtained for all the seismic stations were calculated using 18 regional earthquakes. To quantitatively estimate the goodness of the site correction, the volcanic tremor source locations obtained by using site corrections were compared with those performed without such corrections. The seismic signal was filtered in two different frequency bands before applying correction: (i) the band 1-2 Hz, which contains most of the tremor energy, and (ii) the band 5-10 Hz, in which, likely due to scattering phenomena, the assumption of isotropic radiation behind the volcanic tremor source location method is valid. The results revealed that the seismic signal correction for site effects improved the tremor location results. Such improved tremor locations, together with volcanological and geodetic data, allowed us to identify two distinct periods characterised by different tremor locations during lava fountains (July - August 20 and August 20 - November 15). Such differences were probably due to magma recharge phenomena, taking place during the former period.PublishedVO4465V. Processi eruttivi e post-eruttiviJCR Journa