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

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

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

Ground deformation modeling of flank dynamics prior to the 2002 eruption of Mt. Etna

On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude, suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry

Geodetic Deformation versus Seismic Crustal Moment-Rates: Insights from the Ibero-Maghrebian Region

Seismic and geodetic moment-rate comparisons can reveal regions with unexpected potential seismic hazards. We performed such a comparison for the Southeastern Iberia—Maghreb region. Located at the western Mediterranean border along the Eurasia–Nubia plate convergence, the region has been subject to a number of large earthquakes (M ≥ 6.5) in the last millennium. To this end, on the basis of available geological, tectonic, and seismological data, we divided the study area into twenty-five seismogenic source zones. Many of these seismogenic source zones, comprising the Western Betics, the Western Rif mountains, and the High, Middle, and Saharan Atlas, are characterized by seismic/geodetic ratio values lower than 23%, evidencing their prevailing aseismic behavior. Intermediate seismic/geodetic ratio values (between 35% and 60%) have been observed for some zones belonging to the Eastern Betics, the central Rif, and the Middle Atlas, indicating how crustal seismicity accounts only for a moderate fraction of the total deformation-rate budget. High seismic/geodetic ratio values (> 95%) have been observed along the Tell Atlas, highlighting a fully seismic deformation

Ground deformation modeling of flank dynamics prior to the 2002 eruption of Mt. Etna

On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude, suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry

The 2011 Lorca earthquake slip distribution controlled by groundwater crustal unloading

Earthquake initiation, propagation and arrest are influenced by fault frictional properties(1,2) and preseismic stress(3,4). Studies of triggered and induced seismicity(5-7) can provide unique insights into this influence. However, measurements of near-field, surface ground deformation(8,9) and pre-earthquake stress conditions necessary for such studies are rare. Here, we use geodetic data to determine surface deformation associated with the M-w 5.1 earthquake that occurred in Lorca, southeast Spain, on 11 May 2011. We use an elastic dislocation model to show that earthquake nucleation and the area of main fault slip occurred at very shallow depths of 2-4 km, on a rupture plane along the Alhama de Murcia Fault. Slip extended towards the surface, across fault segments with frictional properties that changed from unstable to stable. The area of fault slip correlates well with the pattern of positive Coulomb stress change that we calculate to result from the extraction of groundwater in a nearby basin aquifer. We therefore suggest that the distribution of shallow slip during the Lorca earthquake could be controlled by crustal unloading stresses at the upper frictional transition of the seismogenic layer, induced by groundwater extraction. Our results imply that anthropogenic activities could influence how and when earthquakes occur

Application of differential SAR interferometry for studying eruptive event of 22July 1998 at Mt.Etna

One of the main objectives of the project “Development and application of remote sensing methods for the monitoring of active Italian volcanoes” is directed to an operational use of differential interferometry as a tool for volcano monitoring. A first step to achieve this goal is to test commercial software in order to evaluate the most suitable for the project purposes. For testing software, SAR images collected by ERS2 from May 98 to August 98, before and after the strong eruptive event occurred on 22 July 98 at Voragine crater of Etna, have been selected. The explosive event was classified sub-plinian producing a 12 km high eruptive column and lapilli fell on land as far as 70 km south-eastward along the dispersal axis. Pre, post and across event image pairs have been processed. In particular the pair 13 May 98-22 July 98, 22 July 98-26 August 98, 13 May 98-26 August 98 are used for testing respectively pre, post and across event. In first analysis, the fringes in the differential products show a positive elevation trend in the summit area of the volcano. In particular, an increased of about 1,5 fringes in the period pre-event, and a decrement of 1 fringe in the period post-event is observed. This result is agreement whit field of deformation expected in such kind of event, confirming that the interferometric processing tool used id suitable for the purpose of the project