Mt. Etna 2001 eruption: New insights into the magmatic feeding system and the mechanical response of the western flank from a detailed geodetic dataset

In the last decades, the increasing availability of comprehensive geodetic datasets has allowed for more detailed constraints on subsurface magma storage and conduits at several active volcanoes worldwide. Here, by using a large dataset of geodetic measurements collected between early January 2001 and August 2001, we identified at least six different deformation stages that allow us to quantify the surface deformation patterns before, during and after the 2001 Mt. Etna volcanic eruption. Our results are largely in agreement with previous works (e.g. the presence of a deep inflating source and a shallow dike located beneath the north-western and upper southern flanks of the volcano, respectively). However, we provide (1) finer resolution of the temporal activity of these magmatic sources, leading to (2) new evidence related to the evolution of the magmatic system and the mechanical response of the western flank, in particular during the pre-eruptive phase. Results and analysis show a clear change in the ground deformation pattern of the volcano in response to the 20-24 April 2001 seismic swarm that occurred beneath the western flank, evolving from a volcano-wide inflation to a slight deflation of the summit area. We suggest that the source responsible for the volcano-wide inflation, beginning in the fall of 2000, experienced a drastic reduction in the inflation rate in response to this seismic swarm. Moreover, we provide evidence for the presence of a new inflating source located beneath the upper southern flank at a depth of similar to 7.0 km bsl that triggered both the occurrence of the 20-24 April 2001 seismic swarm and led to the rapid ascent of magma upward to the surface after 12 July (the Lower Vents system was fed by fresh magma rising from this source). The presence of this inflating source is inferred by (1) seismological and volcanological observations coming from the 2001 eruption and (2) seismological constraints coming from a previous similar episode that occurred at Etna during the 1993-1998 period. Furthermore, both shallow deflations observed after the 20-24 April 2001 seismic swarm and during the first day of the eruption also could be due to the deflation of two adjacent portions of the same shallow (similar to 2 km bsl) reservoir. Such reservoirs would feed the activity that occurred at the South-East Crater after January 2001 and the activity of the Upper Vents system during the July-August eruption, in agreement with petrochemical observations. Through an updated revision of the available data, we shed some light on the relevance of pre-eruptive activity patterns, an important element for an effective volcano monitoring. (C) 2014 Elsevier B.V. All rights reserved

Exotic Searches

The experimental information on the search for non $q \bar q$ mesons as glueballs, hybrids and multiquark states is reviewed. Candidate states which are particularly amenable to detailed study by accumulating large samples of $J/\psi$, $\eta_c$, $\chi$ decays at a $\tau$-charm factory are discussed.Comment: 25 pages, LaTex, 22 Figures (available from the authors on request), BARI-TH/94-17

Evidences of a contractional pattern along the northern rim of the Hyblean Plateau (Sicily, Italy) from GPS data

In this paper we present the main results inferred from GPS data collected between 1998.00 and 2009.78 along the northern rim of the Hyblean Plateau from 9 continuous and 23 survey-mode sites. From a geological point of view, this area is of great interest because 1) it represents an important piece of the collision front between Nubia and Eurasia 2) it is very close to the biggest European volcano Mount Etna and 3) it has been hit by strong earthquakes in the past (1169 and 1693) that struggled the cities of Catania, Siracusa and Ragusa provoking tens of thousands of casualties. We have found that the ground deformation pattern clearly defines an area of prevailing contraction along the northern rim of the Hyblean Plateau with a maximum negative strain-rate of about 0.14µstrain/yr in agreement with both geological and Interferometric Synthetic Aperture Radar (InSAR) data. In addition, a transition to extensional regime is acting toward the central sector of the plateau. The velocity field referred to the Eurasian frame indicates that a large part of the plateau is dominated by a 5.4mm/yr northward motion

Current stress and strain-rate fields across the Dead Sea Fault System: Constraints from seismological data and GPS observations

The stress and strain-rate fields characterizing the Dead Sea Fault System are investigated by using seismological and geodetic observations. In order to assess spatial variations in the regional stress field, we compiled a multidisciplinary dataset of well-constrained horizontal indicators, by merging all available data reported in literature with the data obtained in this study through weighted stress inversions of focal plane solutions. Our findings indicate that the state of stress is characterized by the coexistence of a normal faulting stress regime with the primarily strike-slip one, according to the regional frame illustrated by previous geological and seismological observations. An updated velocity field computed from new observations and earlier published data depicts the general left-lateral motion of the Dead Sea Fault System well. In agreement with previous studies, we detected some differences in the slip-rate pattern between the northern and the southern sectors of the fault system. The geodetic strain-rate field highlights how much of the deformation is accommodated along the fault system itself in a narrow region. The comparison between the stress and the strain-rate directions reveals that both orientations are near-parallel, clearly indicating that present-day crustal stress and ground deformation patterns are chiefly driven by the same tectonic processes. (C) 2013 Elsevier B.V. All rights reserved

Geometric and kinematic variations along the active Pernicana fault: Implication for the dynamics of Mount Etna NE flank (Italy)

Geological and structural analyses and ground deformation measurements performed along the eastern portion of the Pernicana fault system and its splay segments allow the structural setting and the kinematic behaviour of the fault to be defined. In addition, the interrelationship between the deformation style of fault segments and the variations of the volcanic pile thickness along the fault strike are investigated using detailed sedimentary basement data. Brittle deformation dominates the N105 degrees fault segment, where the volcanic pile is more than 200 m thick, with the development of a well-defined fault plane characterised by main left-lateral kinematics. The transtensive deformation of the N105 degrees fault is partitioned eastward at Rocca Campana to a main N120 degrees segment. Here, this segment crosses a culmination of the sedimentary basement close to Vena village where the deformation pattern of the thin volcanic pile, less than 100 m thick, is influenced by the more ductile behaviour of the basement generating local short structures with different orientation and kinematics in the southern block of the fault. On the northern one, short E-W trending faults show left-lateral displacements with a minor reverse component on south-dipping planes. This kinematics is related to the oblique orientation of the N120 degrees segment with respect to the seaward motion of the NE flank of Etna. On the whole, the compressive component of the deformation affecting the N120 degrees segment of the Pernicana fault system generates a positive flower structure. (c) 2006 Elsevier B.V All rights reserved

Crustal motion along the Calabro-Peloritano Arc as imaged by twelve years of measurements on a dense GPS network

In this work, we show the results of 12 years of continuous and survey-mode GPS measurements carried out along the western part of the Calabro-Peloritano Arc, from 1996 until the more recent acquisitions in 2008. The results highlight that a NW-SE-oriented similar to 0.15 mu strain/yr extension across the Messina Strait and the Aeolia Tindari-Letojanni fault system is active. Moreover, a N-S compressive strain-rate (similar to 0.65 mu strain/yr) is active across Vulcano and Lipari Islands coupled with an extensional strain-rate of similar to 0.15 mu strain/yr in the E-direction. Finally, taking into account the observed horizontal velocity field, an analytical inversion was performed to obtain a reliable model of deformation of the investigated area. The main results are consistent both with focal mechanism solutions and the current structural setting of the investigated area. (C) 2009 Elsevier B.V. All rights reserved

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

Comment on the paper by Barreca et al.: “The Strait of Messina: Seismotectonics and the source of the 1908 earthquake” (Earth-Science Reviews 218, 2021, 103685)

We discuss the new causative source model for the 1908 Messina Straits earthquake recently proposed by Barreca et al. (2021), where an aseismic slip of 1.13 m along a low-angle discontinuity, preceding the 1908 earthquake, have mechanically destabilized a set of overlying faults, therefore leading them to the rupture. The lack of significant variations of the relative sea level in the Messina harbor area, in the time period relevant for the levelling data (1907–1908) analyzed by Barreca et al., and at least for the decade preceding the event proves the inconsistency of the assumed pre-earthquake aseismic slip. A careful interpretation of crustal earthquake distribution in the Strait does not support the presence of the low-angle discontinuity. The modelled horizontal coseismic pattern reveals a scenario that is not supported by any other independent geological and geophysical observation. We conclude that the source model proposed by Barreca et al. for the 1908 Messina Straits earthquake can not be considered as a viable hypothesis for the causative fault

Kf evaluation in GFRP composites by thermography

Since the presence of a notch in a mechanical component causes a reduction in the fatigue strength, it is important to know the kf value for a given notch geometry and material. This parameter is fundamental in the fatigue design of aeronautical components that are mainly made of composites. kf is available in the literature for numerous types of notch but only for traditional materials such as metals. This paper presents a new practice, based on thermographic data, for the determination of the fatigue notch coefficient kf in composite notched specimens. The innovative aspect of this study is therefore to propose the application on composite materials of a new thermographic procedure to determine kf for several notch geometries: circular, U and V soft and severe notches. It was calculated, for each type of notch, as the ratio between the fatigue limits obtained on the cold and hot zone corresponding to the smooth and notched specimen, respectively. Consequently, this research activity provides, for the first time, a little database of kf for two particular typologies of composite materials showing a fast way to collect further values for different laminates and notch geometries

High rate GPS data on active volcanoes: an application to the 2005-2006 Mt. Augustine (Alaska, USA) eruption

Volcanic eruptions are usually preceded by measurable signals of growing unrest, the most evident of which are the increase in seismicity and ground deformation. It is also important to identify precursors of a possible renewal of the volcanic activity and to distinguish between an eruptive activity characterized by an intrusion (with the related destructive power) and a migration of magma stored in the main conduits. The 2005-2006 eruption at Mt. Augustine (Alaska, USA) is a good example of a massive migration of magmatic fluids from depth (about 1 km b.s.l.) under the effect of gas overpressure. The movements, recorded by High Rate GPS (HRGPS) data (15 s of sampling and processing rate) from the stations deployed on the volcano, define the dimensions and the characteristics of the shallow plumbing system. In this study, we propose a model of the different stages preceding the effusive phase (the 'precursory phase'), where gas overpressure in the body of the volcano opens the terminal conduit