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  • 04. Solid Earth::04.04. Geology::04.04.09. Structural geology  (27)
  • Mt. Etna  (23)
  • Elsevier  (45)
  • Elsevier B.V.
  • 2005-2009  (46)
  • 1985-1989
  • 1950-1954
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Years
Year
  • 1
    Publication Date: 2017-04-04
    Description: The multideformed axial zone of the Apennines provides a great opportunity to explore the influence of preexisting cross-structures (inherited from pre-Quaternary tectonic phases) on the segmentation of Quaternary/active seismogenic extensional faults. Detailed geological and structural data and their comparison with seismological data show that although the attitudes (strike and dip) of oblique preexisting faults are certainly an important factor in determining a segment boundary, the size of the inherited oblique structures seems to be more crucial. Pre-existing cross-structures with lengths ranging from several kilometers to a few tens of kilometers show a twofold behavior. They can act as segment barriers during the rupture of a single fault segment or they can be reactivated as transfer zones inducing the activation of two adjacent segments that belong to the same fault system. Regional basement/crustal oblique pre-existing cross-structures, with lengths ranging from several tens of kilometers to hundreds of kilometers (commonly NNE-striking), may act as “persistent structural barriers” that halt both fault segment and fault system propagation, thus determining their terminations and maximum sizes. In the northern-central Apennines, the NNE-striking Ancona–Anzio, Valnerina, and Ortona–Roccamonfina tectonic lineaments, although having been repeatedly reactivated since the Mesozoic, represent the most important examples of these structures. Moreover, probably due to their misorientation with respect to the present extensional stress field, regional NNE-striking pre-existing structures appear to be less likely to produce strong magnitude events (no surface evidence for Quaternary faulting has been found thus far and historical and instrumental seismicity shows only Mb6 events). M ~7 event, on the other hand, is more likely to occur along the (N)NW–(S)SE trending normal fault systems. Lastly, we propose a model that can explain the different sizes of fault segments and fault systems on the basis of their location with respect to the “persistent structural barriers” and their spacing. In this view, our results may contribute to a more reasonable assessment of the nature and size of future surface ruptures in the northern-central Apennines, which are of critical importance to estimating seismic hazard.
    Description: Published
    Description: 304-319
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Active faults ; Segmentation ; Pre-existing cross-structure ; Structural barrier ; Northern/central Apennines ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the orientation of the structures along which the ruptures occur. These structures represent zones of weakness which could favor the migration of melt toward the surface and the assessment of their geometry is a fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 low-magnitude, tectonic earthquakes occurred at Mt. Etna during the 2002-2003 eruption. We applied a recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on numerically calibrated relationships among the rise time of first P waves and the source parameters for a circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal mechanisms we were able to constrain the “true” fault plane orientation. The level of resolution of the fault planes was assessed through a non linear analysis based on the random deviates technique. The significance of the retrieved fault plane solutions and the fit of the assumed source model to data was assessed through a χ-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known surface faults. The inferred source parameters and Qp are in agreement with the results of previous studies.
    Description: In press
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: rise time ; Mt. Etna ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Publication Date: 2017-04-03
    Description: Despite the recent recognition of Mount Etna as a periodically violently explosive volcano, the hazards from various types of pyroclastic density currents (PDCs) have until now received virtually no attention at this volcano. Large-scale pyroclastic flows last occurred during the caldera-forming Ellittico eruptions, 15–16 ka ago, and the risk of them occurring in the near future is negligible. However, minor PDCs can affect much of the summit area and portions of the upper flanks of the volcano. During the past ~ 20 years, small pyroclastic flows or base-surge-like vapor and ash clouds have occurred in at least 8 cases during summit eruptions of Etna. Four different mechanisms of PDC generation have been identified during these events: (1) collapse of pyroclastic fountains (as in 2000 and possibly in 1986); (2) phreatomagmatic explosions resulting from mixing of lava with wet rock (2006); (3) phreatomagmatic explosions resulting from mixing of lava with thick snow (2007); (4) disintegration of the unstable flanks of a lava dome-like structure growing over the rim of one of the summit craters (1999). All of these recent PDCs were of a rather minor extent (maximum runout lengths were about 1.5 km in November 2006 and March 2007) and thus they represented no threat for populated areas and human property around the volcano. Yet, events of this type pose a significant threat to the lives of people visiting the summit area of Etna, and areas in a radius of 2 km from the summit craters should be off-limits anytime an event capable of producing similar PDCs occurs. The most likely source of further PDCs in the near future is the Southeast Crater, the youngest, most active and most unstable of the four summit craters of Etna, where 6 of the 8 documented recent PDCs originated. It is likely that similar hazards exist in a number of volcanic settings elsewhere, especially at snow- or glacier-covered volcanoes and on volcano slopes strongly affected by hydrothermal alteration.
    Description: Published
    Description: 148-160
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Pyroclastic density currents ; Mt. Etna ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
    Publication Date: 2017-04-04
    Description: We describe the Miocene–Quaternary geological–structural evolution of the region between the Salar de Uyuni and de Atacama, Andes of Chile and Bolivia. We recognized four main tectonic events based on fold geometry, fault kinematics and stratigraphic data. The oldest event, of Miocene age, is characterized by folding and reverse faulting of the sedimentary successions with an E–W direction of shortening in the northern part of the studied area and a WNW–ESE shortening in the southern part. The following two events, of Pliocene age, are characterized by lower shortening amounts; they occurred first by reverse faulting with a NW–SE-trending greatest principal stress (ó1, computed with striated fault planes) and a vertical least principal stress (ó3), followed by pervasive strike-slip faulting with the same NW–SE-trending ó1 and a horizontal NE–SW ó3. The fourth event, dating to the late Pliocene–Quaternary is characterized by normal faulting: the ó3 still trends NE–SW, whereas the intermediate principal stress ó2 exchanged with ó1. Volcanism accompanied both the contractional, transcurrent and extensional tectonic phases. The Mio–Pliocene compression appears directly linked to a rapid convergence and an apparently important coupling between the continental and oceanic plates. The E–W to WNW–ESE direction of shortening of the Miocene structures and the NW–SE ó1 of the Pliocene structures seem to be more linked to an intra-Andean reorientation of structures following the WNW-directed absolute motion of the South-American Plate. The extensional deformations can be interpreted as related to gravity forces affecting the highest parts of the volcanic belt in a sort of asymmetrical (SW-ward) collapse of the belt.
    Description: Published
    Description: 114-135
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Chile ; Bolivia ; Andes ; Fault ; Fold ; Tectonic phases ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2017-04-04
    Description: Eruptions are fed by dikes; therefore, better knowledge of dike propagation is necessary to improve our understanding of how magma is transferred and extruded at volcanoes. This study presents an overview of dike patterns and the factors controlling dike propagation within volcanic edifices. Largely based on published data, three main types of dikes (regional, circumferential and radial) are illustrated and discussed. Dike pattern data from 25 volcanic edifices in different settings are compared to derive semi-quantitative relationships between the topography (relief, shape, height, and presence of sector collapses) of the volcano, tectonic setting (presence of a regional stress field), and mean composition (SiO2 content). The overview demonstrates how dike propagation in a volcano is not a random process; rather, it depends from the following factors (listed in order of importance): the presence of relief, the shape of the edifice and regional tectonic control. We find that taller volcanoes develop longer radial dikes, whose (mainly lateral) propagation is independent of the composition of magma or the aspect ratio of the edifice. Future research, starting from these preliminary evaluations, should be devoted to identifying dike propagation paths and likely locations of vent formation at specific volcanoes, to better aid hazards assessment.
    Description: Partly fundedwith DPC-INGVfunds (LAVAProject).
    Description: Published
    Description: 67–77
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: dikes ; volcanoes ; topography ; tectonic setting ; eruptions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
    Publication Date: 2017-04-04
    Description: The 2001 eruption represents one of the most studied events both from volcanological and geophysical point of view on Mt. Etna. This eruption was a crucial event in the recent dynamics of the volcano, marking the passage from a period (March 1993–June 2001) of moderate stability with slow, continuous flank sliding and contemporaneous summit eruptions, to a period (July 2001 to present) of dramatically increased flank deformations and flank eruptions. We show new GPS data and high precision relocation of seismicity in order to demonstrate the role of the 2001 intrusive phase in this change of the dynamic regime of the volcano. GPS data consist of two kinematic surveys carried out on 12 July, a few hours before the beginning of the seismic swarm, and on 17 July, just after the onset of eruptive activity. A picture of the spatial distribution of the sin-eruptive seismicity has been obtained using the HypoDD relocation algorithm based on the double-difference (DD) technique. Modeling of GPS measurements reveals a southward motion of the upper southern part of the volcano, driven by a NNW–SSE structure showing mainly left-lateral kinematics. Precise hypocenter location evidences an aseismic zone at about sea level, where the magma upraise was characterized by a much higher velocity and an abrupt westward shift, revealing the existence of a weakened or ductile zone. These results reveal how an intrusion of a dike can severely modify the shallow stress field, triggering significant flank failure. In 2001, the intrusion was driven by a weakened surface, which might correspond to a decollement plane of the portion of the volcano affected by flank instability, inducing an additional stress testified by GPS measurements and seismic data, which led to an acceleration of the sliding flanks.
    Description: This work was funded by the Istituto Nazionale di Geofisica e Vulcanologia and by the Dipartimento per la Protezione Civile (Italy).
    Description: Published
    Description: 78–86
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: stress release ; dike ; volcano-tectonics ; flank instability ; Mt. Etna ; instrumental monitoring ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.02. Seismological data ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
    Publication Date: 2017-04-04
    Description: On 27 February 2007, two NE–SW and NNW–SSE dike-fed effusive vents opened to the North (at 650 and 400 m above sea level, asl) of the summit craters at Stromboli, forming a fissure parallel to the inner walls of the Sciara del Fuoco (SdF) sector collapse depression. The formation of these vents was soon followed by rapid subsidence of the summit crater area. This partly obstructed the central conduit, temporarily choking the fissure and increasing the deformation of the upper part of SdF. The reactivation of the NNW–SSE vent and the opening of a new vent located at 500 m asl, fed by a second dike, released the internal pressure and surface deformation ceased. The eruption then continued again from the 400 m vent, after a summit explosion on 15 March, until ending in early April after a progressive decrease of magma output. Repeated NE–SW dike intrusions have occurred in recent years, close to the upper SE limit of the SdF. In that zone, named Bastimento, the eruptive fractures traced the discontinuities that borders the SdF, increasing the risk of triggering new sector collapse. Whereas the NE–SW trending structures lie along the regional volcanostructural trend of the Aeolian arc through Stromboli, the NNW–SSE vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the SdF. Another fundamental aspect of the 2007 eruption is the collapse of the central conduit, due to the rapid and deep magma drainage linked to the opening of the 400 m vent. The intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms, but the opening of new effusive vents released the internal pressures, diminishing the hazard.
    Description: Work funded by INGV and Dipartimento Protezione Civile, Italy.
    Description: Published
    Description: 137-144
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: 2007 Stromboli eruption ; Dike-Fed vent ; Volcano-Tectonics ; Conduit collapse ; Flank instability ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.08. Volcanic arcs ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
    Publication Date: 2020-11-19
    Description: We report on structural and anisotropy of magnetic susceptibility (AMS) results from the Upper Miocene sediments of the Amantea basin, located on the Tyrrhenian coast of the Calabrian Arc (Southern Italy). The stratigraphic succession of the basin is organized in three depositional sequences, separated by two major angular unconformities. Detailed geologica1 mapping and structural analysis demonstrate that the stratigraphic evolution of the Amantea basin is strongly controlled by a synsedimentary extensional tectonic regime. Severa1 NNE-SSW-trending norma1 fault arrays with large scatter in inclination values have been interpreted as due to a domino faulting mechanism, consistent with a WNW-ESE stretching direction. AMS data have been obtained for 13 sites, both in the not constrained in age first depositional sequence (3 sites), and in the upper Tortonian-lower Messinian clays from the second depositional sequence (10 sites). Al1 the sites show a strong magnetic foliation parallel to the bedding planes, and a well defined magnetic lineation subparallel to the local bedding dip directions. The magnetic lineations cluster around a WNW-ESE trend and are parallel to the stretching directions inferred by fault-slip analysis and basin architecture. These new data then confirm the possibility to use the magnetic lineation to map the strain trajectory in weakly deformed extensional sedimentary basins. Paleomagnetic data (from previous studies) show that the whole Calabrian block underwent a 15°-20° clockwise rotation probably in the Pleistocene, postdating the extensional tectonic events which controlled the Amantea basin geometry. Therefore we suggest for the Amantea basin an original E-W-oriented stretching direction, which may be considered as the older extensional direction characterizing the Late Miocene evolution of the southern Tyrrhenian Sea domain.
    Description: Published
    Description: 33-49
    Description: JCR Journal
    Description: reserved
    Keywords: magnetic fabric ; extentional tectonics ; Miocene ; Calabrian Arc ; Italy ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
    Publication Date: 2020-11-26
    Description: During the July^August 2001 eruption of Mt. Etna development of extensional fractures/faults and grabens accompanied magma intrusion and subsequent volcanic activity. During the first days of the eruption, we performed an analysis of attitude, displacement and propagation of fractures and faults exposed on the ground surface in two sites, Torre del Filosofo and Valle del Leone, located along the same fracture system in the region surrounding the Valle del Bove depression on the eastern flank of Mt. Etna. Fractures and faults formed as the consequence of a shallow intruding dyke system that fed the several volcanic centres developed along the fracture system. The investigated sites differ in slope attitude and in geometrical relationships between fractures and slopes. In particular, the fracture system propagated parallel to the gentle slope (67‡ dip) in the Torre del Filosofo area, and perpendicular to the steep slope (V25‡ dip) in the Valle del Leone area. In the Torre del Filosofo area, slight graben subsidence and horizontal extension of the ground surface by about 3 m were recorded. In the Valle del Leone area, extensional faulting forming a larger and deeper graben with horizontal extension of the ground surface by about 10 m was recorded. For the Valle del Leone area, we assessed a downhill dip of 14‡ for the graben master fault at the structural level beneath the graben where the fault dip shallows. These results suggest that dyke intrusion at Mount Etna, and particularly in the region surrounding the Valle del Bove depression, may be at the origin of slope failure and subsequent slumps where boundary conditions, i.e. geometry of dyke, slope dip and initial shear stress, amongst others, favour incipient failures.
    Description: Published
    Description: 281-294
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: dykes ; extensional fractures ; grabens ; slope failures ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
    Publication Date: 2021-05-12
    Description: Although the tectonic features and stress regime typical for accretionary complexes and back-arc domains have been widely documented so far, few are known on the transitional zone separating these two systems. Here we report on structural analysis and anisotropy of magnetic susceptibility (AMS) results from Eocene–Pliocene sediments exposed in western Sardinia. From late Oligocene to middle Miocene, the studied area was located between the Alpine–Apennine wedge to the east, which was undergoing shortening and accretion, and the Liguro–Provenc al basin, undergoing extension and spreading. We find that, prior to the formation of the Liguro–Provenc al basin, the middle Eocene–lower Oligocene sediments cropping out at the southwesternmost edge of Sardinia were subjected to NE–SW shortening (in present-day coordinates), in agreement with recently reported geological information. Conversely, the upper Oligocene–Pliocene sedimentary sequences record a different evolutionary stage of extensional processes. Upper Oligocene–middle–upper Burdigalian sediments clearly show a N–S-oriented magnetic lineation that can be related to extensional direction along the prevalent E–W-oriented normal faults. On the other hand, no magnetic lineation has been detected in upper Burdigalian–Serravallian sediments, which mark the end of the first rifting process in Sardinia, which likely coincides with the rift-to-drift transition at the core of the Liguro–Provençal basin. Finally, a NE–SW extension is observed in two Tortonian–Pliocene sites at the northwestern margin of the NNW–SSE-oriented Campidano graben. Our study confirms that AMS may represent a valuable strain-trajectory proxy and significantly help to unravel the characters of temporally superimposed tectonic events.
    Description: Published
    Description: 213-232
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Back-arc basin ; Magnetic anisotropy susceptibility (AMS) ; Sardinia ; Mediterranean area ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
    Publication Date: 2020-11-17
    Description: Mt. Etna in Sicily (Italy) is one of the best monitored basaltic volcanoes in the world due to the frequent eruptions from its summit and flanks. Routine monitoring carried out by the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, for surveillance purposes permits following the evolution of volcanic events. In this paper, a description of the ash monitoring system as occurred during the August-December 2006 summit eruption at the Southeast Crater (SEC) is shown. This eruption was characterized by lava flow effusions and vigorous Strombolian activity. Eighteen paroxysmal episodes occurred up to the end of November, forming weak ash plumes accompanied by moderate tephra fallout over Etna’s slopes. During these events, we applied a multidisciplinary approach to promptly monitor the paroxysmal activity and the associated tephra fallout, through analysis from seismic tremor and observation from live-cameras, sampling operations, mapping and analysis of the deposit. During the most significant episodes, we carried out textural and grain-size analysis on tephra samples and evaluated the whole grain-size deposit and the erupted volume, while numerical simulations of tephra dispersal allowed better understanding eruptive dynamics. An example of this methodology is applied to the 16 November episode, during which seismic tremor furnished important constraints on the chronology. This paroxysmal eruption produced light fallout on the north-east sector of the volcano for about ten hours and a number of debris-avalanches over the slopes of the SEC cone. The erupted deposit was composed for the most part of lithic components and characterized by a whole grain-size distribution centered on 2.2 , while its total mass was evaluated 7 x 106 kg. On the whole, such integrated studies help to obtain information on magma fragmentation and eruptive mechanisms, to characterize the explosive styles shown by Etna and finally, to better approach the monitoring of imminent eruptions.
    Description: FIRB Italian project “Sviluppo Nuove Tecnologie per la Protezione e Difesa del Territorio dai Rischi Naturali” funded by Italian Minister of University and Research
    Description: Published
    Description: 123-134
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Description: open
    Keywords: Mt. Etna ; volcanic ash monitoring ; tephra deposit ; 2006 eruption ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 12
    Publication Date: 2021-07-14
    Description: Field geological data of the Pantelleria Island, a large Late Quaternary volcano located in the Sicily Channel rift zone, integrated with offshore geophysical information, are used to derive the structural setting of the Island and the surrounding region, and to analyse the relationships between tectonics and magmatism. Field work shows that the principal faults exposed on the Island fall into two systems trending NNE–SSW and NW–SE. Mapped faults from offshore multichannel seismic profiles show similar trends, and some of them represent the offshore extension of the Pantelleria Island structures. The NW–SE faults bound the Pantelleria Graben, one of the three main depressions formed since the Late Miocene–Early Pliocene within the African continental platform, which compose the Sicily Channel rift zone. A 3-D Moho depth geometry, derived from inversion of Bouguer gravity data, shows a significant uplift of the discontinuity up to 16–17 km beneath the westernmost part of the Pantelleria Graben and beneath the Pantelleria Island; it lows rapidly to 24–25 km away from the graben northeastward and south-westward. The Moho uplift could explain the presence of a shallow magma chamber in the southern part of the Island, where processes of magmatic differentiation are documented. Geological and geophysical data suggest that the northwestern part of the Sicily Channel is presently dominated by a roughly E–W directed extensional regime. Crustal cracking feeding the Quaternary volcanism could be also related to this extensional field that would be further responsible for the development of the N–S trending volcanic belt that extends in the Sicily Channel from Lampedusa Island to the Graham Bank. This mode of deformation is confirmed also by geodetic data. This implies that in the northwestern part of the Sicily Channel, the E–W extension replaced the NE–SW crustal stretching that originated the NW-trending tectonic depressions constituting the rift zone. © 2008 Elsevier B.V. All rights reserved.
    Description: Published
    Description: 32-46
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Pantelleria Island ; Channel rift zone ; structural analysis ; Quaternary volcanism ; gravity modelling ; tectonic extension ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
    Publication Date: 2020-12-14
    Description: This paper presents a new methodology for studying the evolution of curved mountain belts by means of paleomagnetic analyses performed on analogue models. Eleven models were designed aimed at reproducing various tectonic settings in thin-skinned tectonics. Our models analyze in particular those features reported in the literature as possible causes for peculiar rotational patterns in the outermost as well as in the more internal fronts. In all the models the sedimentary cover was reproduced by frictional low-cohesion materials (sand and glass micro-beads), which detached either on frictional or on viscous layers. These latter were reproduced in the models by silicone. The sand forming the models has been previously mixed with magnetite-dominated powder. Before deformation, the models were magnetized by means of two permanent magnets generating within each model a quasi-linear magnetic field of intensity variable between 20 and 100 mT. After deformation, the models were cut into closely spaced vertical sections and sampled by means of 1x1-cm Plexiglas cylinders at several locations along curved fronts. Care was taken to collect paleomagnetic samples only within virtually undeformed thrust sheets, avoiding zones affected by pervasive shear. Afterwards, the natural remanent magnetization of these samples was measured, and alternating field demagnetization was used to isolate the principal components. The characteristic components of magnetization isolated were used to estimate the vertical-axis rotations occurring during model deformation. We find that indenters pushing into deforming belts from behind form non-rotational curved outer fronts. The more internal fronts show oroclinal-type rotations of a smaller magnitude than that expected for a perfect orocline. Lateral symmetrical obstacles in the foreland colliding with forward propagating belts produce non-rotational outer curved fronts as well, whereas in between and inside the obstacles a perfect orocline forms only when the ratio between obstacles’ distance and thickness of the cover is greater than 10. Finally, when a belt collides with an obstacle in the foreland oblique to the shortening direction the outer front displays rotations opposite in sign to oroclinal-type rotations, whereas the internal fronts seem to assume an "oroclinal type" rotational pattern. Furthermore rotation is easier in laterally unconfined models, i.e. when the wedge can "escape" laterally. The results from our models may be useful when compared to paleomagnetic rotations detected in natural arcs. In these cases, our results may allow for better understanding the tectonic setting controlling the genesis of curved mountain fronts, as is the case of the Gela Nappe of Sicily we compare with some of our models.
    Description: Published
    Description: 633-654
    Description: JCR Journal
    Description: reserved
    Keywords: paleomagnetism ; tectonic rotations ; physical models ; arcuate belts ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 14
    Publication Date: 2017-04-04
    Description: We report on the anisotropy of magnetic susceptibility (AMS) analyses of fine-grained sediments deposited during the Messinian in foredeep basins at the front of the northern Apenninic chain. The data refer to 32 sampling sites, mostly distributed in the fine-grained intervals of the Laga and Colombacci formations, extending along the belt for a total length of about 300 km. Rock magnetism analyses indicate that the magnetic susceptibility and its anisotropy are in most cases dominated by the paramagnetic minerals of the clay matrix. In order to delineate the contribution of the ferrimagnetic fraction to the overall susceptibility fabric, the anisotropy of the anhysteretic remanent magnetisation was investigated at some representative sites. The magnetic fabric of the studied sediments mostly reflects the effects of compaction, showing a predominant magnetic foliation parallel to the bedding piane. At all the sites a well distinct magnetic lineation was also found, which is parallel to the fold axes and thrust fronts, both at local and regional scales. This feature is maintained in sequences that differ for sedimentological character and age, implying that the magnetic lineation was produced by a mild tectonic overprint of the primary sedimentary-compactional fabric. The relationship between the magnetic lineation trends and the vertical axis rotations detected by Speranza et al. [Speranza, F., Sagnotti, L.. Mattei, M., 1997. J. Geophys. Res. 102, 3153-3166] indicates that the magnetic lineation formed during the compressive phases of the Messinian-early Pliocene, when the Apenninic front was almost rectilinear and oriented N32O°.
    Description: Published
    Description: 73-93
    Description: JCR Journal
    Description: reserved
    Keywords: magnetic anisotropy ; rock strain ; northern Apennines ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 15
    Publication Date: 2017-04-04
    Description: The 2001 eruption represents one of the most studied events both from volcanological and geophysical point of view on Mt. Etna. This eruption was a crucial event in the recent dynamic of the volcano, marking the passage from a period (March 1993 – June 2001) of moderate stability with slow, continuous flank sliding and contemporaneous summit eruptions, to a period (July 2001 to present) of dramatically increased flank deformations and flank eruptions. We show new GPS data and high precision relocation of seismicity in order to demonstrate the role of the 2001 intrusive phase in this change of the dynamic regime of the volcano. GPS data consist of two kinematic surveys carried out on 12 July, a few hours before the beginning of the seismic swarm, and on 17 July, just after the onset of eruptive activity. A picture of the spatial distribution of the sin-eruptive seismicity has been obtained using the HypoDD relocation algorithm based on the double-difference (DD) technique. Modeling of GPS measurements reveal a southward motion of the upper southern part of the volcano, driven by a NNW-SSE structure showing mainly left-lateral kinematics. Precise hypocenter location evidences an aseismic zone at about sea level, where the magma upraise was characterized by a much higher velocity and an abrupt westward shift, revealing the existence of a weakened or ductile zone. These results reveal how an intrusion of a dike can severely modify the shallow stress field, triggering significant flank failure. In 2001, the intrusion was driven by a weakened surface, which might correspond to a decollement plane of the portion of the volcano affected by flank instability, inducing an additional stress testified by GPS measurements and seismic data, which led to an acceleration of the sliding flanks.
    Description: In press
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 3.6. Fisica del vulcanismo
    Description: 4.2. TTC - Scenari e mappe di pericolosità sismica
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: JCR Journal
    Description: reserved
    Keywords: Stress release ; Dike ; Volcano-tectonics ; Flank instability ; Mount Etna ; Instrumental monitoring ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
    Publication Date: 2017-04-04
    Description: On 27 February 2007, two NE–SW and NNW–SSE dike-fed effusive vents opened to the North (at 650 and 400 m above sea level, asl) of the summit craters at Stromboli, forming a fissure parallel to the inner walls of the Sciara del Fuoco (SdF) sector collapse depression. The formation of these vents was soon followed by rapid subsidence of the summit crater area. This partly obstructed the central conduit, temporarily choking the fissure and increasing the deformation of the upper part of SdF. The reactivation of the NNW–SSE vent and the opening of a new vent located at 500 m asl, fed by a second dike, released the internal pressure and surface deformation ceased. The eruption then continued again from the 400 m vent, after a summit explosion on 15 March, until ending in early April after a progressive decrease of magma output. Repeated NE–SW dike intrusions have occurred in recent years, close to the upper SE limit of the SdF. In that zone, named Bastimento, the eruptive fractures traced the discontinuities that borders the SdF, increasing the risk of triggering new sector collapse. Whereas the NE–SW trending structures lie along the regional volcanostructural trend of the Aeolian arc through Stromboli, the NNW–SSE vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the SdF. Another fundamental aspect of the 2007 eruption is the collapse of the central conduit, due to the rapid and deep magma drainage linked to the opening of the 400 m vent. The intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms, but the opening of new effusive vents released the internal pressures, diminishing the hazard.
    Description: In press
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: 2007 Stromboli eruption ; Dike-fed vent ; Volcano-Tectonics ; Conduit collapse ; Flank instability ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.08. Volcanic arcs ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
    Publication Date: 2017-04-04
    Description: Three different methodologies were used to measure Radon (222Rn) in soil, based on both passive and active detection system. The first technique consisted of Solid State Nuclear Track Detectors (SSNTD), CR-39 type, and allowed integrated measurements. The second one consisted of a portable device for short time measurements. The last consisted of a continuous measurement device for extended monitoring, placed in selected sites. Soil 222Rn activity was measured together with soil Thoron (220Rn) and soil carbon dioxide (CO2) efflux, and it was compared with the content of radionuclides in the rocks. Two different soil gas horizontal transects were investigated across the Pernicana fault system (NE flank of Mount Etna), from November 2006 to April 2007. The results obtained with the three methodologies are in a general agreement with each other and reflect the tectonic settings of the investigated study area. The lowest 222Rn values were recorded just on the fault plane, and relatively higher values were recorded a few tens of meters from the fault axis on both of its sides. This pattern could be explained as a dilution effect resulting from high rates of soil CO2 efflux. Time variations of 222Rn activity were mostly linked to atmospheric influences, whereas no significant correlation with the volcanic activity was observed. In order to further investigate regional radon distributions, spot measurements were made to identify sites having high Rn emissions that could subsequently be monitored for temporal radon variations.. SSNTD measurements allow for extended-duration monitoring of a relatively large number of sites, although with some loss of temporal resolution due to their long integration time. Continuous monitoring probes are optimal for detailed time monitoring, but because of their expense, they can best be used to complement the information acquired with SSNTD in a network of monitored sites.
    Description: In press
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Soil Radon and Thoron activity ; soil CO2 efflux ; Pernicana fault system ; Mount Etna ; volcano-tectonic monitoring ; 03. Hydrosphere::03.04. Chemical and biological::03.04.07. Radioactivity and isotopes ; 03. Hydrosphere::03.04. Chemical and biological::03.04.08. Instruments and techniques ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 18
    Publication Date: 2017-04-04
    Description: During an eruption at the Bocca Nuova, one of the summit craters of Mt. Etna, in October-November 1999 a part of the crater floor near its WNW rim was uplifted to form a dome-shaped feature that consisted of older lava and pyroclastics filling the crater. This endogenous dome grew rapidly over the crater rim, thus being perched precariously over the steep outer slope of the Bocca Nuova, and near-continuous collapse of its steep flanks generated swiftly moving pyroclastic avalanches over a period of several hours. These avalanches advanced at speeds of 10-20 m s-1 and extended up to 0.7 km from their source on top of lavas emplaced immediately before. Their deposits were subsequently covered by lava flows that issued from vents below the front of the dome and from the Bocca Nuova itself. Growth of the dome was caused by the vertical intrusion of magma in the marginal W part of the crater, which deformed and uplifted previously emplaced, still hot and plastically deformable eruptive products filling the crater. The resulting avalanches had all characteristics of pyroclastic flows spawned by collapse of unstable flanks of lava domes, but in this case the magma involved was of mafic (hawaiitic) composition and would have, under normal circumstances, produced fluid lava flows. The formation of the dome and the generation of the pyroclastic avalanches owe their occurrence to the rheological properties of the eruptive products filling the crater, which were transformed into the dome, and to the morphological configuration of the Bocca Nuova and its surroundings. The density contrast between successive erupted products may also have played a role. Although events of this type are to be considered exceptional at Etna, their recurrence might represent a serious hazard to visitors to the summit area.
    Description: Published
    Description: 115-128
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; Bocca Nuova ; endogenous lava dome ; pyroclastic avalanches ; magma ascent ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 19
    Publication Date: 2017-04-04
    Description: 14th MAEGS Volume
    Description: The active tectonics at the front of the Southern Apennines and in the Adriatic foreland is characterized by E-W striking, right-lateral seismogenic faults, interpreted as reactivated inherited discontinuities. The best studied among these is the Molise-Gondola shear zone (MGsz). The interaction of these shear zones with the Apennines chain is not yet clear. To address this open question we developed a set of scaled analogue experiments, aimed at analyzing: 1) how dextral strike-slip motion along a pre-existing zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge; 2) the propagation of deformation as a function of increasing displacement; 3) any insights on the active tectonics of Southern Italy. Our results stress the primary role played by these inherited structures when reactivated, and confirm that regional EW dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the Southern Apennines.
    Description: Published
    Description: 2-13
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: Active fault ; Strike-slip kinematics ; Fault reactivation ; Sandbox model ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 20
    Publication Date: 2017-04-04
    Description: Structural analysis and field mapping together with simple geometrical and flexural elastic models, document that two styles of Quaternary extensional tectonics characterized the Gran Sasso range (central Apennines, Italy). In the western part of the range, extension took place on 10–15-km-long range-front normal faults with associated 600–1000-m-high escarpments showing evidence of Late Glacial–Holocene activity. This topography has been reproduced with a thin elastic plate subjected to the isostatic forces induced by the movement along high-angle (55°–65°) planar normal faults. In the eastern part of the belt extension occurred on shallow-dipping normal faults (30°–35°) which reactivated progressively deeper pre-existing thrusts. In this area antithetic "domino" faults formed to accommodate the mechanical adjustment of the hanging-wall over a variably dipping major fault surface. The eastward increase in shortening, due to the earlier compressional phase, documented in the Gran Sasso belt by previous authors, accounts for the more developed zones of weakness and high topographic relief in the eastern sector. This setting could explain the different styles of extension and the more advanced northeastern limit of normal faulting in the eastern sector. This work suggests that normal faults can originate either with low- or high-angle geometry in the upper crust according to the pre-existing tectonic setting and that topography could be important in controlling the geometry and pattern of migrating normal faulting.
    Description: Published
    Description: 229-254
    Description: JCR Journal
    Description: reserved
    Keywords: extensional tectonics ; Quaternary ; thrust faults ; topography ; Apennines ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 21
    Publication Date: 2017-04-04
    Description: We analyze the 1997–2006 seismicity of the transition zone between Southern and Central Apennines, which is one of the most active seismic areas of Italy. Our aim is to add information on the seismotectonic picture of this area. Seismic activity is characterized by single events with Mb3.0 and low magnitude (Mb4.0) seismic sequences (1997–98 and 2005) and swarms (1999, 2000 and 2001). Hypocenters are within the upper 15 km of the crust. The epicentral distribution of the relocated seismicity shows that single events prevalently align NW–SE along the Apennine chain axis. This seismicity is related to the main, NE–SW extension affecting the chain. Single events concentrate also: at the south of the seismogenetic source responsible for the 1915 earthquake, where the 2000 swarm occurred; between the faults of the 1984 and 1805 events, where the 2001 sequence developed; between the faults of the 1805 and 1688 events, where the 1997–1998 seismic sequence concentrated. The seismic swarms occurred in 1999, 2000 and 2005 are located inside the Ortona– Roccamonfina structural line, which strikes NNE–SSW and separates the Central Apennines from the Southern ones. The epicentral distribution of these swarms and focal mechanisms suggest the presence of active NE–SW faults moving in response to a NW–SE extension. The results of the strain analysis on 52 wellconstrained focal mechanisms evidence a prevailing NE–SW extension, corresponding to the large scale stress field acting in the Apennine Chain, and a second-order NW–SE extension. This last direction of extension was already observed in the 1997–98 and 2001 seismic sequences. The location of the NE–SW striking faults responsible for the seismic swarms suggest that some segments of the Ortona–Roccamonfina line are still active and move in response to both the NE–SW regional extension of Southern Apennines, and to a NW–SE striking longitudinal extension.
    Description: Published
    Description: 102-110
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 3.1. Fisica dei terremoti
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Apennines ; seismicity ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
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  • 22
    Publication Date: 2017-04-04
    Description: Eruptions are often fed by dikes; therefore, better knowledge of dike propagation is necessary to improve our understanding of how magma is transferred and extruded at volcanoes. This study presents an overview of dike patterns and the factors controlling dike propagation within volcanic edifices. Largely based on published data, three main types of dikes (regional, circumferential and radial) are illustrated and discussed. Dike pattern data from 25 volcanic edifices in different settings are compared to derive semi-quantitative relationships between the topography (relief, shape, height, and presence of sector collapses) of the volcano, tectonic setting (presence of a regional stress field), and mean composition (SiO2 content). The overview demonstrates how dike propagation in a volcano is not a random process; rather, it depends from the following factors (listed in order of importance): the presence of relief, the shape of the edifice and regional tectonic control. We find that taller volcanoes develop longer radial dikes, whose (mainly lateral) propagation is independent of the composition of magma or the aspect ratio of the edifice. Future research, starting from these preliminary evaluations, should be devoted to identifying dike propagation paths and likely locations of vent formation at specific volcanoes, to better aid hazards assessment.
    Description: In press
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: open
    Keywords: dikes ; volcanoes ; topography ; tectonic setting ; eruptions ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 23
    Publication Date: 2017-04-04
    Description: The tectonic escarpments locally known as ‘Timpe’ cut a large sector of the eastern flank of Etna, and allow an ancient volcanic succession dating back to 225 ka to be exposed. Geological and volcanological investigations carried out on this succession have allowed us to recognize relevant angular unconformities and volcanic features which are the remnants of eruptive fissures, as well as important changes in the nature, composition and magmatic affinity of the exposed volcanics. In particular, the recognition in the lower part of the succession of important and unequivocal evidence of ancient eruptive fissures led us to propose a local origin for these volcanics and to revise previous interpretations which attributed their westward-dipping to the progressive tectonic tilting of strata. These elements led us to reinterpret the main features of the volcanic activity occurring since 250 ka BP and their relationship with tectonic structures active in the eastern flank of Etna. We propose a complex paleo-environmental and volcanotectonic evolution of the southeastern flank of Mt. Etna, in which the Timpe fault system played the role of the crustal structure that allowed the rise and eruption of magmas in the above considered time span.
    Description: Published
    Description: 289-306
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Mount Etna ; tectonics ; fisssure eruptions ; columnar basalt ; fault escarpment ; xenoliths ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 24
    Publication Date: 2017-04-03
    Description: Despite the recent recognition of Mount Etna as a periodically violently explosive volcano, the hazards from various types of pyroclastic density currents (PDCs) have until now received virtually no attention at this volcano. Large-scale pyroclastic flows last occurred during the caldera-forming Ellittico eruptions, 15–16 ka ago, and the risk of them occurring in the near future is negligible. However, minor PDCs can affect much of the summit area and portions of the upper flanks of the volcano. During the past ~ 20 years, small pyroclastic flows or base-surge-like vapor and ash clouds have occurred in at least 8 cases during summit eruptions of Etna. Four different mechanisms of PDC generation have been identified during these events: (1) collapse of pyroclastic fountains (as in 2000 and possibly in 1986); (2) phreatomagmatic explosions resulting from mixing of lava with wet rock (2006); (3) phreatomagmatic explosions resulting from mixing of lava with thick snow (2007); (4) disintegration of the unstable flanks of a lava dome-like structure growing over the rim of one of the summit craters (1999). All of these recent PDCs were of a rather minor extent (maximum runout lengths were about 1.5 km in November 2006 and March 2007) and thus they represented no threat for populated areas and human property around the volcano. Yet, events of this type pose a significant threat to the lives of people visiting the summit area of Etna, and areas in a radius of 2 km from the summit craters should be off-limits anytime an event capable of producing similar PDCs occurs. The most likely source of further PDCs in the near future is the Southeast Crater, the youngest, most active and most unstable of the four summit craters of Etna, where 6 of the 8 documented recent PDCs originated. It is likely that similar hazards exist in a number of volcanic settings elsewhere, especially at snow- or glacier-covered volcanoes and on volcano slopes strongly affected by hydrothermal alteration.
    Description: In press
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; Pyroclastic density currents ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 25
    Publication Date: 2017-04-04
    Description: The development of the 2004–2005 eruption at Etna (Italy) is investigated by means of field surveys to define the current structural state of the volcano. In 2004–2005, a fracture swarm, associated with three effusive vents, propagated downslope from the SE summit crater towards the SE. Such a scenario is commonly observed at Etna, as a pressure increase within the central conduits induces the lateral propagation of most of the dikes downslope. Nevertheless, some unusual features of this eruption (slower propagation of fractures, lack of explosive activity and seismicity, oblique shear along the fractures) suggest a more complex triggering mechanism. A detailed review of the recent activity at Etna enables us to better define this possible mechanism. In fact, the NW–SE-trending fractures formed in 2004–2005 constitute the southeastern continuation of a N–S-trending fracture system which started to develop in early 1998 to the east of the summit craters. The overall 1998–2005 deformation pattern therefore forms an arcuate feature, whose geometry and kinematics are consistent with the head of a shallow flank deformation on the E summit of Etna. Similar deformation patterns have also been observed in analogue models of deforming volcanic cones. In this framework, the 2004–2005 eruption was possibly induced by a dike resulting from the intersection of this incipient fracture system with the SE Crater. A significant acceleration of this flank deformation may be induced by any magmatic involvement. The central conduit of the volcano is presently open, constantly buffering any increase in magmatic pressure and any hazardous consequence can be expected to be limited. A more hazardous scenario may be considered with a partial or total closing of the central conduit. In this case, magmatic overpressure within the central conduit may enhance the collapse of the upper eastern flank, triggering an explosive eruption associated with a landslide reaching the eastern lower slope of the volcano.
    Description: Published
    Description: 195–206
    Description: reserved
    Keywords: eruption triggering ; volcano-tectonics ; fracture fields ; flank spreading ; Mt. Etna ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
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  • 26
    Publication Date: 2017-04-04
    Description: 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° 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° fault is partitioned eastward at Rocca Campana to a main N120° 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° 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° segment of the Pernicana fault system generates a positive flower structure.
    Description: Published
    Description: 210-232
    Description: JCR Journal
    Description: reserved
    Keywords: faults ; ground deformation ; Mt. Etna ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques
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  • 27
    Publication Date: 2017-04-04
    Description: Several sites with anomalous emissions of carbon dioxide were investigated in the region south of Mt. Etna volcano in order to assess the types of emission (focused and/or diffuse), their surface extension and the total output of CO2. Most of the studied emissions are located on the southwest boundary of Mt. Etna, near the town of Paternò. They consist of three mud volcanoes (known as Salinelle), one spring with bubbling gas (Acqua Grassa) and one area of diffuse degassing (Peschería). Another site (Naftía Lake) with remarkable gas emissions (bubbling gas into a lake as well as adjacent areas of diffuse soil degassing) is located further southwest of Mt. Etna in an area of extinct Quaternary volcanism on the northwest margin of Hyblean Mts. In all of these areas the origin of the highest CO2 emissions is clearly magmatic, and degassing to the atmosphere occurs mostly through tectonic structures, probably at a regional scale. The magmatic source that feeds anomalous degassing in the above areas is likely to be the same that feeds volcanic activity at Mt. Etna. Focused degassing was measured at each emission vent using devices that measure the air speed, whereas diffuse soil degassing was measured using the accumulation chamber method. In total, 712 measurements were carried out (146 in focused degassing vents, 566 on diffuse degassing areas). Single CO2 output values ranged from 1.8 10−5 to 1.68 kg s−1. In the case of diffuse degassing areas, statistical analyses allowed to discriminate between biogenic CO2 and CO2 deriving from a magmatichydrothermal source. Only the efflux values from the latter source were considered in the output estimates. The total estimated output thus obtained was about 2.61 kg s−1, relevant to a total surface of about 146,500 m2 (which includes only the magmatic CO2 emissions). This value is comparable with that of most non-volcanic emissions from geothermal and/or faulted areas of centralsouthern Italy, as well with the CO2 output from some of the volcanic areas of Italy.
    Description: Istituto Nazionale di Geofisica e Vulcanologia; Dipartimento per la Protezione Civile.
    Description: Published
    Description: 46–63
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; mud volcanoes ; soil CO2 effluxes ; magmatic degassing ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 28
    Publication Date: 2017-04-04
    Description: The sustained and uninterrupted plume degassing at Mount Etna volcano, Southern Italy, represents the troposphere’s most prominent natural source of fluorine. Of the ~ 200 Mg of fluorine (as HFg) emitted daily by the volcano, 1.6±2.7 Mg are deposited by wet and dry deposition. Fluorine-deposition via volcanic ash, here characterised for the first time, can be quite significant during volcanic eruptions (i.e. 60 Mg of fluorine were deposited during the 2001 eruption through volcanic ash, corresponding to ~ 85% of the total fluorine deposition). Despite the fact that these depositions are huge, the fate of the deposited fluorine and its impact on the environment are poorly understood. We herein present original data on fluorine abundance in vegetation (Castanea Sativa and Pinus Nigra) and andosoils from the volcano’s flank, in the attempt to reveal the potential impact of volcanogenic fluorine emissions. Fluorine contents in chestnut leaves and pine needles are in the range 1.8-35 µg/g and 2.1-74 µg/g respectively; they exceed the typical background concentrations in plants growing in rural areas, but fall within the lower range of typical concentrations in plants growing near high fluorine anthropogenic emission sources. The rare plume fumigations on the lower flanks of Mt Etna (distance 〉 4 km from summit craters) are probably the cause of the “undisturbed” nature of Etnean vegetation: climatic conditions, which limit the growth of vegetation on the upper regione deserta, are a natural limit to the development of more severe impacts. High fluorine contents, associated with visible symptoms, were only measured in pine needles at three sites, located near recently-active (2001 to 2003) lateral eruptive fractures. Total fluorine contents (FTOT) in the Etnean soils have a range of 112-341 µg/g, and fall within the typical range of undisturbed soils; fluorine extracted with distilled water (FH2O) have a range of 5.1 to 61 µg/g and accounts for 2-40 % of FTOT. FH2O is higher in topsoils from the eastern flank (downwind), while it decreases with depth in soil profiles and on increasing soil grain size (thereby testifying to its association with clay-mineral-rich, fine soil fractions). The fluorine adsorption capacity of the andosoils acts as a natural barrier that protects the groundwater system.
    Description: Published
    Description: 87-101
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; Fluorine ; environmental volcanology ; impact of volcanic F ; soils ; vegetation ; volcanic ash ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 05. General::05.08. Risk::05.08.01. Environmental risk
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  • 29
    Publication Date: 2017-04-04
    Description: Tephra fallout represented a major source of hazard for eastern Sicily during the 2001 eruption of Mt. Etna (Italy) between 19 July and 6 August. Long-lasting explosive activity was generated from the 2570 m vent, producing a volcanic plume up to 5 km high above sea level. The eruption caused copious lapilli and ash fallout over the volcano flanks for several days. Flight operations were cancelled at the Catania and Reggio Calabria airports; health risk and economic damage put communities living close to this active volcano on the alert. The explosive activity at the 2570 m vent had three main phases characterized by phreatomagmatic, magmatic and vulcanian explosions. In this paper, we analyze the first explosive phase between 19 and 24 July that formed a tephra deposit on the volcano's south-east flanks. Immediately after the first phase of the eruption, numerous tephra samples were collected in order to draw an isomass map, calculate physical parameters for the eruption and analyze the plume dispersion on the basis of deposit geometry. The tephra deposit shows a bilobate shape due to the change with time of both the vigour of the eruption and the wind direction and velocity that caused a higher rate of particle accumulation along two dispersal axes (SE and SSE). The total mass of tephra erupted was calculated with two different fitting methods: exponential line segments and a power law fit on the semi-logarithmic plot of mass per unit area versus , resulting in values of 1.02 109 kg and 2.31 109 kg, respectively. The whole deposit grain-size was calculated applying the Voronoi tessellation method, it shows a mode of 2 and thus indicates a high degree of magma fragmentation during the first phase of the eruption. Plume dispersal was investigated by an advection–diffusion model to reconstruct the tephra deposit. In the modelling, we took into account the variations of wind direction and velocity, and eruption intensity by dividing the explosive phase into sixteen sub-eruptions and considering the final deposit as the sum of the mass computed for each sub-eruption. Using best fit procedures, we find that the optimal agreement between computed values and field data is obtained by using the total mass calculated with the power law fit and a terminal settling velocity distribution with a particle aggregation model. The computed tephra dispersal was able to reproduce the bilobate shape of the real deposit. This work proves that advection–diffusion models can describe sedimentation processes of weak, i.e., bent-over, long-lasting plumes if the variations of wind direction and velocity, and eruptive intensity are included.
    Description: Published
    Description: 147-164
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; basaltic explosive activity ; violent strombolian eruption ; tephra deposit ; dispersal modelling ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 30
    Publication Date: 2017-04-04
    Description: We investigated the relationships between modelled strain produced by explosive activity through a volcanic conduit, observed paroxystic episodes on Mt. Etna, and high-precision continuous tilt signals recorded during such events from the tilt monitoring network. The tilt changes detected during two different explosive episodes were compared with those calculated from analytical models of ground deformation in order to constrain source properties. The July 22, 1998 subplinian explosion from Voragine crater produced small tilt changes (order of 0.5–1.5 μrad) recorded over the entire volcano edifice, implying a small storage at nearly 2.5 km below sea level. The 1998–2000 period was characterized by tens of spectacular lava fountains from the South-East crater. Very small tilt change (∼ 0.1 μrad) was recorded by a single station on the high north-eastern flank of Mt. Etna and indicated the action of a limited and shallow conduit with 1.5–1.9 km depth. These results provide a contribution to better infer the shallow plumbing system beneath Mt. Etna.
    Description: Published
    Description: 221–234
    Description: reserved
    Keywords: explosive activity ; tilt data ; volcano source modeling ; Mt. Etna ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 31
    Publication Date: 2017-04-04
    Description: Travertine deposits outcropping in the lower SW flank of Mt. Etna were studied for their mapping, as well as for their chemical, mineralogical and isotopic compositions. These deposits are dated to about 24 to 5 ka in the Adrano area, located at the western limit of the study area. In this area travertines show high Mg contents and are composed mostly of dolomite, thus apparently ruling out any primary deposition in favour of a diagenetic origin. Travertines outcropping near Paternò, in the east part of the study area, should be younger than 18 ka. Those located to the SSW of Paternò (Paternò–Diga) show high Sr contents and aragonite as dominant mineralogical phase, thus suggesting primary deposition. Those located to the Wof Paternò (Paternò Simeto–Stazione) are instead poor both in Mg and in Sr and show calcite as dominant phase. Carbon isotope composition of travertines indicates a magmatic origin of CO2 that formed them. Based on the estimated volume of travertines, between 10 and 20 Gg/a of CO2 were involved in their formation. The time-span of travertine formation coincided with the eruptive cycles of Ellittico and the first part of Mongibello, which were probably characterised by a greater amount of CO2 transported through groundwater circulation. Widespread travertine deposition probably ceased after the opening of the Valle del Bove depression that modified the volcanologic and hydrologic conditions in the summit crater area.
    Description: Istituto Nazionale di Geofisica e Vulcanologia
    Description: Published
    Description: 64–70
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: open
    Keywords: Mt. Etna ; travertine deposits ; carbon isotope composition ; mineralogical composition ; chemical composition ; CO2 budget ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling
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  • 32
    Publication Date: 2017-04-03
    Description: Veins are the geologic record of fluids that filled fractures at depth in the crust. In southern Tuscany (Italy), well-exposed Oligocene–Early Miocene sandstones hosting vein systems provide insight into the role of pore fluid and the stress state at the time of vein formation. The stress ratio (Φ = (σ2 − σ3)/(σ1 − σ3)) and driving stress ratio (R ′ = (Pf − σ3)/(σ1 − σ3)) were determined by analysing the distribution, length and aperture of fractures and veins and the magnitude of fluid overpressure. The derived fluid overpressure for the whole vein system ranges from 30 MPa to 64 MPa, with an average of 43 MPa; these values indicate that veins formed under supra-hydrostatic pressure conditions. Despite their spatial contiguity, two different vein arrays show very different stress and driving pressure ratios. One vein system is characterised by Φ = 0.62 and R ′ = 0.60, the other by Φ = 0.54 and R ′ = 0.78. The described vein systems are an example of a close spatial association of two non-hydraulically connected vein systems representing fluids focused through the upper crust.
    Description: Published
    Description: 1386-1399
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Fracture systems ; Vein systems ; Fluid overpressure ; Sandstones ; Tuscany ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 33
    Publication Date: 2017-04-04
    Description: We describe the recent activity of the Cayambe-Afiladores-Sibundoy Fault (CASF) and recognise it as one of the major potential active structures of northwestern South America, based on field observations, stereoscopic aerial photos of offset late Pleistocene-Holocene deposits and landforms, and crustal seismic activity. The CASF runs for at least 270 km along the sub-Andean zone of northern Ecuador and southern Colombia. We measured systematic latest Pleistocene-Holocene right-lateral strike-slip motion and right-lateral reverse motion consistent with earthquake focal mechanism solutions, and estimated a 7.7 +/- 0.4 to 11.9 +/- 0.7 mm/yr slip-rate. Magnitudes of the earthquakes that could be generated by possible fault-segment reactivation range up to M 7.0 +/- 0.1. The CASF should be considered as a major source of possible future large magnitude earthquakes, presenting a seismic hazard for the densely populated regions to the west. The CASF is part of the tectonic boundary of the North Andean block escaping NNE-wards with respect to the stable South American plate.
    Description: Published
    Description: 664-680
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Active fault ; Seismicity ; Slip-rate calculation ; Colombia ; Ecuador ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 34
    Publication Date: 2020-12-15
    Description: The eruptive events of the July–August 2001 and October 2002–January 2003 at Mt. Etna provide new insights for reconstructing the complex geometry of the feeding system and their relationship to regional tectonics. The 2001 eruption took place mainly on the upper southern sector of the volcano. The eruption was preceded by a large earthquake swarm for a few days before its onset and accompanied by ground deformation and fracturing. The development of surface cracking along with the seismic pattern has allowed us to recognize three distinct eruptive systems (the SW–NE, NNW–SSE and N–S systems) which have been simultaneously active. Such eruptive systems are only the upper portions of a complex feeding system that was fed at the same time by two distinct magmas. The SW–NE and NNW–SSE systems, connected with the SE crater conduit, were fed by magma coming from depth, whereas the N–S system served instead as an ascending pathway for an amphibole-bearing magma residing in a shallow reservoir. The eruptive activity started again on October 2002 on the NE Rift Zone, where about 20 eruptive vents were aligned between 2500 and 1900 m a.s.l., and on the southern flank, from the central crater to the Montagnola. The onset of eruptive activity was accompanied by a seismic swarm. As in the 2001 eruptive event, two independent feeding systems formed, characterized by distinct magmas. The SW–NE system controlled the feeding of the Northeast Rift and was accommodated by left-lateral displacement along the WNW–ESE trending Pernicana Fault. The N–S system fed the eruptions on the southern flank. Moreover, the associated crustal deformation triggered seismic reactivation of tectonic structures in the eastern flank of the volcano and offshore. These two last eruptions indicate that at Mt. Etna the ascent of magma, as well as the accommodation of deformation, is strongly dominated by local extensional structures that are connected to a regional tectonic regime.
    Description: Published
    Description: 211-233
    Description: partially_open
    Keywords: extensional tectonics ; volcanic activity ; seismicity ; Sicily ; Mt. Etna ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 35
    Publication Date: 2017-04-04
    Description: On July 18, 2001, two main eruptive vents opened on the southern flank of Mount Etna volcano (Italy) at ~2100 m and ~2550 m a.s.l., respectively. The former vent fed mild strombolian activity and lava flows, while the latter represented the main explosive vent, producing strong phreato-magmatic explosions. Explosions at this latter vent, however, shifted to a strombolian style in the following days, before switching back to phreato-magmatic activity towards the end of the eruption, which ended on August 9, 2001. On August 3, a small seismoacoustic array was deployed close to the eruptive vents. The array was composed of three stations, which recorded seismic and infrasonic waves coming from both of the eruptive vents. A further seismoacoustic station, equipped with a thermal-infrared sensor, was also installed several kilometers north of the first array. Seismic signals relating to the strombolian activity at the 2100-m vent were characterized by a strong decompression at the source. Analysis of the time delays between seismic, infrasonic and infrared event onsets also revealed that ejection velocities during explosions from both vents were subsonic. Time delays between the onset of explosive events apparent in the infrared and infrasound data indicated that the explosion source at the 2550-m vent was located 220–250 m below the crater rim. In comparison, the depth of the seismic source was estimated to be between 230 and 335 m below the rim. This converts to 120–150 and 130–235 m below the preexisting ground surface. In addition, time delays between seismic and infrasonic signals recorded for the lower (2100 m) vent also revealed a seismic source that was no more than a few tens of meters deeper than the fragmentation surface.
    Description: Published
    Description: 219-230
    Description: partially_open
    Keywords: Mt. Etna ; explosive eruptions ; arrays ; seismic ; infrasonic and thermal data ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
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  • 36
    Publication Date: 2017-04-04
    Description: The strike-slip Pernicana fault system (PFS) was activated along the eastern flank of Mt. Etna during an earthquake in September 2002 and, one month later, during the eruption of the NE Rift. Structural and volcanological data suggest that the PFS was activated as a result of the slide of the NE flank of Etna. This activation produced surface fracturing on walls and on paved and unpaved roads. The segments of the PFS, arranged in a right stepping en échelon configuration, show (a) an inverse proportion between length and frequency; (b) fractal behavior over scales of 10−2 –101 m, between their length, overstep and overlap; (c) consistent strike with regard to their fault array; and (d) a progressive eastward decrease in the displacement, along the smallest faults. The consistent geometric and kinematic features of the PFS, related to the sector collapse of Etna, are similar to those of faults in strike-slip settings.
    Description: Published
    Description: 343-355
    Description: partially_open
    Keywords: Active faulting ; Strike-slip faults ; Fractal behavior ; Volcano collapse ; Mt. Etna ; Pernicana fault system ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 37
    Publication Date: 2017-04-04
    Description: This study presents a detailed analysis and interpretation of the seismicity that occurred on July 2-7 and August 22, 2000, during a ground uplift episode which started on March 2000 at Solfatara crater, Campi Flegrei. Earthquakes are located using a probabilistic grid-search procedure acting on a 3-D heterogeneous earth structure. The mainshock of the July swarm depicts a spectrum characterized by a few narrow peaks spanning the 1^5-Hz frequency band. For this event, we hypothesize a direct involvement of magmatic fluids in the source process. Conversely, the spectra of the August events are typical of shear failure. For these latter events, we evaluate the source properties from P-and Swave displacement spectra. Results for the most energetic shocks (Md around 2) yield a source radius in the order of 100 m and stress drop around 10 bars, in agreement with most of the earthquakes that occurred during the 1982-1984 bradyseismic crises. For the August swarm we identify two clusters of similar earthquakes. Application of highresolution relative location techniques to these events allows for the recognition of two parallel alignments trending NE^SW. The relationship among source dimension and relative location evidences overlapping of sources. This may be interpreted in terms of either a heterogeneous stress field or a lubrication process acting over the fault surface. For a selected subset of the August events, we also analyze the splitting of the shear waves: results are indicative of wave propagation through a densely fractured medium characterized by a distribution of cracks oriented NE-SW. The pattern of faulting suggested by relative locations and shear-wave splitting is not consistent with the surface trace of NW^SE striking faults. However, a detailed mesostructural analysis carried out over the Solfatara area indicated the occurrence of two main crack systems striking NW-SE and NE-SW. This latter system shows a strike consistent with that derived from seismic evidence. Results from a stress analysis of the crack systems indicate that a fluid overpressure within the NW-SE-striking faults is able to form NE-SW cracks. We found that the pressure of fluids Pf required to activate the NW-SE faults is less than cHmin, while the Pf value required to open the NE-SW cracks is higher than cHmax. Our main conclusions are: (a) the Solfatara area is affected by two orthogonal fracture systems, and the fluid pathway during the 2000 crisis mainly occurred along the NNE-SSW/NE-SW-striking crack system; (b) the July seismicity is associated to the upward migration of a pressure front triggered by an excess of fluid pressure from a small-size magmatic intrusion; conversely, the August events are associated to the brittle readjustment of the inflated system occurring along some lubricated structures.
    Description: Published
    Description: 229-246
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    Keywords: Seismicity ; Hydrothermal fuids ; Fuid pressure ; Faults ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 38
    Publication Date: 2017-04-03
    Description: Remarkable changes in the local magnetic field were associated with the onset of the 2002–2003 flank eruption at Mt. Etna. After differential magnetic field measurements were filtered from the external noise by using adaptive filters, we recognized two stages in the total intensity changes, which are closely related to different volcanic events: (a) rapid variations of about 4–5 nT associated with October 26 seismic swarm recorded beneath the summit craters; (b) step-like variations of 9–10 nT coincident with October 27 eruptive fissures opening up in the north flank. These observations are generally consistent with those calculated from simple magnetic models of these volcanic processes, in which the magnetic changes are generated by stress redistribution due to magmatic intrusions at different depth. The magnetic data not only allow the timing of the intrusive event to be described in greater detail but also, together with other volcanological and geophysical evidences, permit some constraints to be set on the characteristics of propagation of a shallow dike. Firstly, at around midnight on 26 October magma was rapidly injected to a depth of 3–4 km just below the summit craters. Secondly, after 1:00 on 27 October, continued intrusion magma occurred upward and culminated a few hundred meters below the free surface fractured along a N–E direction. Thirdly, at about 2:28, magma gave rise to an explosive fissural vent at the northern base of the NE crater near 3000 m a.s.l. Finally, at about 5:00, the first eruptive fissure became active along the eastern border of the NE rift at 2500 m a.s.l. The rate of growth of the magnetic anomalies, moreover, leads to the interpretation that the magmatic intrusion travelled northward from base of the NE crater to the NE rift at approximately 14 m/min.
    Description: Published
    Description: 1-14
    Description: partially_open
    Keywords: eruptions ; monitoring ; magnetic methods ; volcanomagnetic modeling ; Mt. Etna ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 39
    Publication Date: 2017-04-04
    Description: This survey proposes a new approach to identify buried caldera boundaries of a volcanic cone, combining (1) a systematic elliptic Fourier functions (EFF) analysis on the contour lines based on the external shape of the edifice with (2) self-potential (SP) measurements on volcano flanks. The methodology of this approach is to investigate the relationships between (1) vertical morphological changes inferred from EFF analysis and (2) lateral lithological transition inside the edifice inferred from SP/elevation gradients. The application of these methods on Misti volcano in southern Peru displays a very good correlation. The three main boundaries evidenced by hierarchical cluster analysis on the contour lines coincide with the two main boundaries characterised by SP signal and with a secondary SP signature related with a summit caldera. In order to explain these results showing a very good correlation between morphologic and lithologic changes as function of elevation, caldera boundaries have been suggested. The latter would be located at an average elevation of (1) 4350–4400 m, (2) 4950–5000 m, and (3) 5500– 5550 m. For the lowest boundary in elevation, the coincidence with the lateral extension of the hydrothermal system inferred from SP measurements suggests that caldera walls act as a barrier for lateral extension of hydrothermal systems. In the summit area, the highest boundary has been related with the summit caldera, inferred by a secondary SP minimum and geological evidence.
    Description: - Institut de Recherche pour le Développement (IRD) - Instituto Geofisico del Peru´ (IGP).
    Description: Published
    Description: 283– 297
    Description: partially_open
    Keywords: caldera ; elliptic Fourier functions ; geomorphology ; self-potential ; Misti volcano ; Peru ; 03. Hydrosphere::03.02. Hydrology::03.02.02. Hydrological processes: interaction, transport, dynamics ; 03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.02. Data dissemination::05.02.04. Hydrogeological data ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 40
    Publication Date: 2017-04-04
    Description: Since the early 1970s enhanced eruptive activity of Mount Etna has been accompanied by selective geochemical changes in erupted lavas, among which a gradual increase of alkalis whose origin is still debated. Here we provide further insight into the origin of this recent evolution, based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase-poor primitive basalt that was extruded during a highly explosive flank eruption in July–August 2001. Two types of lava were erupted simultaneously along a N–S fracture system. Trachybasalts from the upper vents (2950–2700 m) were simply drained out by fracturing of the central volcanic conduit. They are identical to summit crater lavas and contain Mg-poor olivines (Fo70–72) with evolved and volatile-poor melt inclusions that represent late-stage crystallisation during shallow open conduit degassing. In contrast, plagioclase-poor basalt (80% of total) extruded through the lower vents (2550–2100 m) derived from lateral dyke intrusion of a more primitive and volatile-rich magma across the sedimentary basement. This primitive melt is best preserved in rare Fo82.4–80.5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent. Its high dissolved contents of H2 O (3.4 wt.%), CO2 (0.11 to 0.41 wt.%), S (0.32 wt.%), Cl (0.16 wt.%) and F (0.094 wt.%) point to its closed system ascent from ∼400 to 250 MPa (∼12 to 6.5 km depth b.s.l.). However, the predominance of euhedral olivine phenocrysts with common reverse zoning (cores Fo76–78 and rims Fo78–80) and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved, crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting. The few preserved inclusions in these olivines indicate pre-eruptive storage of that magma body at about 5 km depth b.s.l., in coherence with seismic data. We propose that the 2001 flank eruption resulted from gradual overpressuring of Etna's shallow plumbing system due to the influx of volatile-rich primitive basalt that may have begun several months in advance. We find that this basalt is much richer in alkalis (2.0 wt.% K2 O) and has higher S/Cl (2.0) but lower Cl/K and Cl/F ratios than all pre-1970s Etnean lavas (1.4 wt.% K2 O, S/Cl=1.5), as further exemplified by melt inclusions in entrained olivine xenocrysts. Combining these new observations with previously published data, we argue that the 2001 basalt represents a new alkali-rich basic end-member feeding Mt. Etna, only few amount of which had previously been extruded during a 1974 peripheral eruption and, more recently, during brief paroxysmal summit events. Over the last three decades this new magma has progressively mixed with and replaced the former K-poorer trachybasalts filling the plumbing system, leading to extrusion of gradually more primitive and alkali-richer lavas. Its geochemical singularities cannot result from shallow crustal contaminations. Instead, they suggest the involvement of an alkali-richer but Cl-poorer arc-type component during recent magma genesis beneath Etna.
    Description: Published
    Description: 1-17
    Description: partially_open
    Keywords: Mt. Etna ; volatiles ; degassing ; eruptive mechanism ; magma geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 41
    Publication Date: 2017-04-04
    Description: Mount Etna produced two significant eruptions in 2001 and 2002–2003, which we have analysed using geological, seismic and deformation data. These eruptions showed some similarities, such as the activating of two magmatic plumbing systems (central–lateral and eccentric), but they differed in their triggering mechanisms. While the 2001 eruption was largely the result of the emplacement of a N–S eccentric dike (independent from the central conduits) consistent with E–W regional extension, the 2002–2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano. This is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions. During the months prior to the 2001 eruption, most epicenters were concentrated on the southern flank, at depths of 5–15 km below sea level. During the 4 days before the eruption, earthquake hypocenters migrated to shallower levels (from 5 km bsl. upward) indicating the emplacement of the eccentric dike. This is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements (EDM). In contrast, the months before the 2002–2003 eruption were characterised by shallower seismicity, mainly concentrated along the active faults bordering the slipping flank sector. Flank slip accelerated in September 2002 and a second, more vigorous acceleration of flank slip occurred on 26–27 October 2002, accompanying the opening of eruptive vents. The very short (2 h) seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption. Subsequently, flank slip-deformation extended all over the eastern and southeastern flanks of the volcano, causing serious damage in this sector. The events of 2001–2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics, magma accumulation and eruption, and flank instability. In this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip, which in turn facilitated the 2002–2003 eruption. This sequence of events points to a long-term feedback mechanism between magmatism and flank instability at Etna.
    Description: Published
    Description: 235-255
    Description: partially_open
    Keywords: eruption triggering ; central–lateral vs. eccentric eruptions ; flank instability and slip ; volcano-tectonics ; Mt. Etna ; instrumental monitoring ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 42
    Publication Date: 2017-04-04
    Description: Two strong flank eruptions occurred in July–August 2001 and from late October 2002 to late January 2003 at Mt. Etna volcano. The two eruptions mainly involved the upper southern flank of the volcano, a particularly active area during the last 30 years, damaging several tourist facilities and threatening some villages. The composite eruptive activity on the upper southern flank of Mt. Etna during 2001–2003 has confirmed “a posteriori” the results of a multidisciplinary study, started well before its occurrence by combining geological, seismic and geochemical data gathered in this part of the volcano. We were able, in fact, to highlight fractured zones likely to be re-activated in the near future in this area, where the largest majority of eruptive fissures in the recent past opened along N120° to N180° ranging directions. The spatial distribution of earthquake epicentres during the period June 30th 2000–June 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre-2001 period and that of the 2001 and 2002 lateral eruptions. Soil CO2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids (mainly CO2 and water vapour) along some NNW–SSE-trending volcano-tectonic structures of the area even during inter-eruptive periods, indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of Etna. The temporal changes in both seismic and geochemical data from June 30th, 2000 to June 30th, 2001 were compared with the evolution of volcanic activity. The comparison allowed to recognize at least two sequences of anomalous signals (August to December 2000 and April to June 2001), likely related to episodes of step-like magma ascent towards the surface, as indicated by the following eruptive episodes. The N120° to N180° structural directions are in accord with one of the main structural lines affecting eastern Sicily; they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of Etna in the near future. This study also pointed out the high instability of the southern slope of Etna, a sector where the potential hazard by lava flow invasion will remain high also in the near future.
    Description: Published
    Description: 20
    Description: partially_open
    Keywords: Mt. Etna ; fault detection ; soil gas ; historical eruptive fissures ; eruptive activity ; local seismicity ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
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  • 43
    Publication Date: 2017-04-04
    Description: The evolution of scaling characteristics of the local geomagnetic field and of the seismicity at Etna volcano is studied in relation to the strong eruptive activity occurred here from 2000 to 2002. Scaling laws are found in the hourly time variability of magnetic data and in the seismicity pattern. The scaling exponents suggest the presence of persistent temporal fluctuations. Clear links between the dynamics of the measured data and the eruptive volcanic episodes are revealed. Fractal dimensions of seismicity seem to be always correlated to the beginning of main eruptive events, while strong alterations of the dynamics of the local magnetic field take place only when the eruptive fractures opened very close to the magnetic sites.
    Description: Published
    Description: 96-106
    Description: partially_open
    Keywords: scaling characteristics ; volcanic eruptions ; geomagnetic field ; seismic activity ; Mt. Etna ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 44
    Publication Date: 2017-04-04
    Description: Large-scale flank instability on Mount Etna is associated with a distinct set of faults radiating generally from the summit area and restricted to the volcanic edifice itself. New observations and mapping of very recent and continuing deformation along these faults and related structures have been analysed in combination with published information, including recent seismic and eruption data, enabling the faults to be placed in three groups. Two of these, the Pernicana fault system (PFS) and the Ragalna fault system (RFS) bound, respectively, the northern and south-western margins of instability. Their activity responds to cycles of magma pressure associated with flank eruptions, together with subsequent deflation as gravity dominates. These cycles may operate at different depths, with the RFS bordering deep-seated instability. Their positions appear governed by the contact, in the substrate of the volcano, between relatively weak early Quaternary clays and stronger rocks of the Apennine–Maghrebian Chain that rise towards the north and west in the subsurface, buttressing the edifice in these directions. The unstable mass to the un-buttressed south and east is thus defined by its weak substrate and displays structures similar to those produced in model experiments. The third fault group, the Mascaluci–-Trecastagni fault system, borders a rather faster-moving zone of instability in the eastern part of the large unstable mass, outlining one element in a nested pattern in map view. Low-angle detachments below the unstable zones are thought to occur at different levels above a deep and laterally extensive detachment associated with the RFS, producing a nested pattern in section as well. This is illustrated by the PFS where the long-recognised western half of the fault borders a fast moving zone of instability riding above a detachment that daylights as a thrusted deformation front marked by recurring landsliding at an approximate mid-slope position on the volcano. Downslope, the newly recognised eastern extension of the PFS, exhibiting slip-rates an-order-of-magnitude lower than the western segment, is thought to border a deeper slow-moving detachment that daylights offshore. Windows of deformed sub-Etnean clays at anomalously high altitudes may indicate where similar detachments, no longer mechanically favoured and now inactive, have daylighted. As a result, the edifice can be considered, overall, as consisting of multiple unstable areas, nested in plan view and with basal detachments occurring at different levels in section. This model of edifice behaviour is regarded as an evolving one, with detachments waxing and waning in their activity as flank movement progresses.
    Description: Published
    Description: 137-153
    Description: partially_open
    Keywords: Mount Etna ; instability; flank faults ; volcano collapse models ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 45
    Publication Date: 2017-04-04
    Description: New geochemical data on dissolved major and minor constituents in 276 groundwater samples from Etna aquifers reveal the main processes responsible for their geochemical evolution and mineralisation. This topic is of particular interest in the light of the progressive depletion of water resources and groundwater quality in the area. Multivariate statistical analysis reveal 3 sources of solutes: (a) the leaching of the host basalt, driven by the dissolution of magmaderived CO2; (b) mixing processes with saline brines rising from the sedimentary basement below Etna; (c) contamination from agricultural and urban wastewaters. The last process, highlighted by increased concentrations of SO4,NO3, Ca, F and PO4, is more pronounced on the lower slopes of the volcanic edifice, associated with areas of high population and intensive agriculture. However, this study demonstrates that natural processes (a) and (b) are also very effective in producing highly mineralised waters, which in turn results in many constituents (B, V, Mg) exceeding maximum admissible concentrations for drinking water.
    Description: Published
    Description: 863–882
    Description: partially_open
    Keywords: Hydrogeochemistry ; water quality ; Mt. Etna ; 03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.02. Hydrology::03.02.06. Water resources ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters
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  • 46
    Publication Date: 2022-05-24
    Description: Many studies have assessed the strong influence of volcanic activity on the surrounding environment. This is particularly true for strong gas emitters such as Mt. Etna and Stromboli volcanoes. Among volcanic gases, fluorine compounds are potentially very harmful. Fluorine cycling through rainwater in the above volcanic areas was studied analysing more than 400 monthly bulk samples. Data indicate that only approximately 1% of fluorine emission through the plume is deposited on the two volcanic areas by meteoric precipitations. Although measured bulk rainwater fluorine fluxes are comparable to and sometimes higher than in heavily polluted areas, their influence on the surrounding vegetation is limited. Only annual crops, in fact, show some damage that could be an effect of fluorine deposition, indicating that long-living endemic plant species or varieties have developed some kind of resistance.
    Description: Published
    Description: 175–185
    Description: partially_open
    Keywords: Fluorine ; Rainwater chemistry ; Volcanic activity ; Mt. Etna ; Stromboli Island ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 05. General::05.08. Risk::05.08.01. Environmental risk
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