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  • Articles  (86)
  • 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism  (28)
  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (23)
  • 04. Solid Earth::04.04. Geology::04.04.09. Structural geology  (19)
  • Mt. Etna  (14)
  • Aeolian Islands, Vulcano
  • Creep observations and analysis
  • Somma-Vesuvius
  • AGU  (58)
  • Geological Society of America  (19)
  • Wiley  (6)
  • American Geophysical Union (AGU)
  • EGU - Copernicus
  • Egu-Copernicus
  • Frontiers Media S.A.
  • Wiley-AGU
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Keywords
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  • 1
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    Coseismic recrystallization during shallow earthquake slip (2015)
    Geological Society of America
    Details
    Publication Date: 2020-11-26
    Description: Solidified frictional melts, or pseudotachylytes, remain the only unambiguous indicator of seismic slip in the geological record. However, pseudotachylytes form at 〉5 km depth, and there are many rock types in which they do not form at all. We performed low- to high-velocity rock friction experiments designed to impose realistic coseismic slip pulses on calcite fault gouges, and report that localized dynamic recrystallization may be an easy-to-recognize microstructural indicator of seismic slip in shallow, otherwise brittle fault zones. Calcite gouges with starting grain size 〈250 μm were confined up to 26 MPa normal stress using a purpose-built sample holder. Slip velocities were between 0.01 and 3.4 m s−1, and total displacements between 1 and 4 m. At coseismic slip velocities ≥0.1 m s−1, the gouges were cut by reflective principal slip surfaces lined by polygonal grains 〈1 μm in size. The principal slip surfaces were flanked by 〈300 μm thick layers of dynamically recrystallized calcite (grain size 1–10 μm) containing well-defined shape- and crystallographic-preferred orientations. Dynamic recrystallization was accompanied by fault weakening and thermal decomposition of calcite to CO2 + CaO. The recrystallized calcite aggregates resemble those found along the principal slip surface of the Garam thrust, South Korea, exhumed from 〈5 km depth. We suggest that intense frictional heating along the experimental and natural principal slip surfaces resulted in localized dynamic recrystallization, a microstructure that may be diagnostic of seismic slip in the shallow crust.
    Description: Published
    Description: 63-66
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: reserved
    Keywords: Rock mechanics ; shallow earthquales ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks ; 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::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    An early Eocene carbon cycle perturbation at ~52.5 Ma in the Southern Alps: Chronology and biotic response (2009)
    AGU
    Details
    Publication Date: 2021-05-17
    Description: At least two transient events of extreme global warming occurred superimposed on the long-term latest Paleocene and early Eocene warming trend in the Paleocene-Eocene thermal maximum (PETM) (or ETM1 ~55.5 Ma) and the Elmo (or ETM2 ~53.6 Ma). Other than warmth, the best known PETM is characterized by (1) significant injection of 13C-depleted carbon into the ocean-atmosphere system, (2) deep-sea carbonate dissolution, (3) strong biotic responses, and (4) perturbations of the hydrological cycle. Documentation of the other documented and suspected "hyperthermals" is, as yet, insufficient to assess whether they are similar in nature to the PETM. Here we present and discuss biomagnetostratigraphic data and geochemical records across two lower Eocene successions deposited on a continental margin of the western Tethys: the Farra and Possagno sections in the Venetian pre-Alps. We recognize four negative carbon isotope excursions within chron C24. Three of these shifts correlate to known or suspected hyperthermals: the PETM, the Eocene thermal maximum 2 (~53.6 Ma), and the informally named "X event" (~52.5 Ma). The fourth excursion lies within a reverse subchron and occurred between the latter two. In the Farra section, the X event is marked by a ~0.6% negative carbon isotope excursion and carbonate dissolution. Furthermore, the event exhibits responses among calcareous nannofossils, planktic foraminifera, and dinoflagellates that are similar to, though less intense than, those observed across the PETM. Sedimentological and quantitative micropaleontological data from the Farra section also suggest increased weathering and runoff as well as sea surface eutrophication during this event.
    Description: Published
    Description: PA2209
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Paleoclimate ; Hyperthermal events ; Early Eocene ; Bio-magnetostratigraphy ; Geochemistry ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Antarctic Drilling Recovers Stratigraphic Records From the Continental Margin (2009)
    AGU
    Details
    Publication Date: 2021-06-25
    Description: The Antarctic Geological Drilling (ANDRILL) program — a collaboration between Germany, Italy, New Zealand, and the United States that is one of the larger programs endorsed by the International Polar Year (IPY; http:// www .ipy .org) — successfully completed the drilling phase of the Southern McMurdo Sound (SMS) Project in December 2007. This second drill core of the program’s campaign in the western Ross Sea, Antarctica, complements the results of the first drilling season [Naish et al., 2007] by penetrating deeper into the stratigraphic section in the Victoria Land Basin and extending the recovered time interval back to approximately 20 million years ago.
    Description: Published
    Description: 89-90
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: N/A or not JCR
    Description: reserved
    Keywords: ANDRILL ; SMS Project ; MMCO (Middle Miocene Climatic Optimum) ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Coherence of Mach fronts during heterogeneous supershear earthquake rupture propagation: Simulations and comparison with observations (2010)
    AGU
    Details
    Publication Date: 2021-02-17
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: We study how heterogeneous rupture propagation affects the coherence of shear– and Rayleigh–Mach wave fronts radiated by supershear earthquakes. We address this question using numerical simulations of ruptures on a planar, vertical strike–slip fault embedded in a three–dimensional, homogeneous, linear elastic half–space. Ruptures propagate spontaneously in accordance with a linear slip–weakening friction law through both homogeneous and heterogeneous initial shear stress fields. In the 3–D homogeneous case, rupture fronts are curved due to interactions with the free surface and the finite fault width; however, this curvature does not greatly diminish the coherence of Mach fronts relative to cases in which the rupture front is constrained to be straight, as studied by Dunham and Bhat (2008). Introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear–wave speed. Calculations of the Fourier amplitude spectra (FAS) of ground velocity time histories corroborate the kinematic results of Bizzarri and Spudich (2008): 1) The ground motion of a supershear rupture is richer in high frequency with respect to a subshear one. 2) When a Mach pulse is present, its high frequency content overwhelms that arising from stress heterogeneity. Present numerical experiments indicate that a Mach pulse causes approximately an –1.7 high frequency falloff in the FAS of ground displacement. Moreover, within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources, our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the Mach fronts, ground motion at stations experiencing Mach pulses should be richer in high frequencies compared to stations without Mach pulses. In contrast to the foregoing theoretical results, we find no average elevation of 5%–damped absolute response spectral accelerations (SA) in the period band 0.05–0.4 s observed at stations that presumably experienced Mach pulses during the 1979 Imperial Valley, 1999 Kocaeli, and 2002 Denali Fault earthquakes compared to SA observed at non–Mach pulse stations in the same earthquakes. A 20% amplification of short period SA is seen only at a few of the Imperial Valley stations closest to the fault. This lack of elevated SA suggests that either Mach pulses in real earthquakes are even more incoherent that in our simulations, or that Mach pulses are vulnerable to attenuation through nonlinear soil response. In any case, this result might imply that current engineering models of high frequency earthquake ground motions do not need to be modified by more than 20% close to the fault to account for Mach pulses, provided that the existing data are adequately representative of ground motions from supershear earthquakes.
    Description: Published
    Description: B08301
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Numerical modeling ; Supershear ruptures ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    An EGF technique to infer the rupture velocity history of a small magnitude earthquake (2008)
    AGU
    Details
    Publication Date: 2021-05-11
    Description: An empirical Green’s function (EGF) technique has been developed to detect the rupture velocity history of a small earthquake. The assumed source model is a circular crack that is characterized by a single and unipolar moment rate function (MRF). The deconvolution is treated as an inverse problem in the time domain, which involves an assumed form of the moment rate function (MRF). The source parameters of the MRF are determined by adopting a global nonlinear inversion scheme. A thorough synthetic study on both synthetic and real seismograms allowed us to evaluate the degree of reliability of the retrieved model parameters. The technique was applied to four small events that occurred in the Umbria-Marche region (Italy) in 1997. To test the hypothesis of a single rupture process, the inversion results were compared with those arising from another EGF technique, which assumes a multiple rupture process. For each event, the best fit model was selected using the corrected Akaike Information Criterion. For all the considered events the most interesting result is that the selected best fit model favors the hypothesis of a single faulting process with a clear variability of the rupture velocity during the process. For the studied events, the maximum rupture speed can even approach the P-wave velocity at the source, as theoretically foreseen in studies of the physics of the rupture and recently observed for high-magnitude earthquakes.
    Description: Published
    Description: B10314
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: EGF technique ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    The 1974 flank eruption of Mount Etna: An archetype for deep dike-fed eruptions at basaltic volcanoes and a milestone in Etna's recent history (2010)
    AGU
    Details
    Publication Date: 2021-05-25
    Description: The 1974 western flank eruption of Mount Etna produced a rare, nearly aphyric and plagioclase-free trachybasalt that could not be derived from the central volcano conduits and was more alkaline and more radiogenic than all previous historical lavas. New results for the petrochemistry and volatile content of its products, combined with contemporaneous seismic and volcanological observations, allow us to reinterpret the origin and significance of this event. We show that the eruption was most likely triggered by deep tectonic fracturing that allowed a dike-like intrusion to propagate in 9 days from 11 km depth up to the surface, bypassing the central conduits. Relatively fast, closed system decompression of the volatile-rich magma initially led to lava fountaining and the rapid growth of two pyroclastic cones (Mounts De Fiore), followed by Strombolian activity and the extrusion of viscous lava flows when gas-melt separation developed in the upper portion of the feeding fracture. The 1974 trachybasalt geochemistry indicates its derivation by mixing 25% of preexisting K-poor magma (best represented by 1763 La Montagnola eruption’s products) and 75% of a new K-rich feeding magma that was gradually invading Mount Etna’s plumbing system and became directly extruded during two violent flank eruptions in 2001–2003. We propose to classify 1974-type so-called ‘‘eccentric’’ eruptions on Etna as deep dike-fed (DDF) eruptions, as opposed to more common central conduit-fed flank eruptions, in order to highlight their actual origin rather than their topographic location. We ultimately discuss the possible precursors of such DDF eruptions.
    Description: Published
    Description: B07204
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: 1974 deep dike-fed eruption ; Mt. Etna ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Mirror-like faults and power dissipation during earthquakes (2015)
    Geological Society of America
    Details
    Publication Date: 2021-05-17
    Description: Earthquakes occur along faults in response to plate tectonic movements, but paradoxically, are not widely recognized in the geological record, severely limiting our knowledge of earthquake physics and hampering accurate assessments of seismic hazard. Light-reflective (so-called mirror like) fault surfaces are widely observed geological features, especially in carbonate-bearing rocks of the shallow crust. Here we report on the occurrence of mirror-like fault surfaces cutting dolostone gouges in the Italian Alps. Using friction experiments, we demonstrate that the mirror-like surfaces develop only at seismic slip rates (∼1 m/s) and for applied normal stresses and sliding displacements consistent with those estimated on the natural faults. Under these experimental conditions, the frictional power density dissipated in the samples is comparable to that estimated for natural earthquakes (1–10 MW/m2). Our results indicate that mirror-like surfaces in dolostone gouges are a signature of seismic faulting, and can be used to estimate power dissipation during ancient earthquake ruptures.
    Description: Published
    Description: 1175-1178
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquakes ; Faults ; Carbonates ; Rock Mechanics ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    On the relations between fracture energy and physical observables in dynamic earthquake models (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: We explore the relationships between the fracture energy density (E_G) and the key parameters characterizing earthquake sources, such as the rupture velocity (v_r), the total fault slip (u_tot), and the dynamic stress drop (Dt_d). We perform several numerical experiments of three‐dimensional, spontaneous, fully dynamic ruptures developing on planar faults of finite width, obeying different governing laws and accounting for both homogeneous and heterogeneous friction. Our results indicate that E_G behaves differently, depending on the adopted governing law and mainly on the rupture mode (pulselike or cracklike, sub‐ or supershear regime). Subshear, homogeneous ruptures show a general agreement with the theoretical prediction of E_G *proportional to* (1 - (v_r/v_S)^2)^(1/2), but for ruptures that accelerate up to supershear speeds it is difficult to infer a clear dependence of fracture energy density on rupture speed, especially in heterogeneous configurations. We see that slip pulses noticeably agree with the theoretical prediction of E_G *proportional to* u_tot^2 , contrarily to cracklike solutions, both sub‐ and supershear and both homogeneous and heterogeneous, which is in agreement with seismological inferences, showing a scaling exponent roughly equal to 1. We also found that the proportionality between E_G and Dt_d^2, expected from theoretical predictions, is somehow verified only in the case of subshear, homogeneous ruptures with RD law. Our spontaneous rupture models confirm that the total fracture energy (the integral of EG over the whole fault surface) has a power law dependence on the seismic moment, with an exponent nearly equal to 1.13, in general agreement with kinematic inferences of previous studies. Overall, our results support the idea that E_G should not be regarded as an intrinsic material property.
    Description: Published
    Description: B10307
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Fracture energy ; Dynamic models ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    High spatial resolution radon measurements reveal hidden active faults on Mt. Etna (2005)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Radon emissions are frequently monitored in volcanically and tectonically active areas in order to reveal changes in soil degassing, as radon acts a tracer for the more abundant CO2 degassing commonly observed in such areas. Between July 2002 and May 2003 a series of discrete measurements of radon concentrations in soil were made with high spatial resolution (∼5–100 m) in the Santa Venerina area on Mt. Etna. These measurements revealed well-defined linear anomalies that we interpret as being caused by active faults whose higher porosity than surrounding soils allows an increased CO2 flux, carrying radon from beneath. These faults were not visible at the surface and were therefore revealed at high spatial resolution by our radon survey. Our hypothesis that the positive anomalies are attributable to active faults was strengthened by the observation of concentrated damage along this geometry during the earthquakes that struck this area in late October 2003.
    Description: Published
    Description: 4
    Description: partially_open
    Keywords: Structural Geology: Role of fluids ; Structural Geology: Fractures and faults ; Structural Geology: Instruments and techniques ; Volcanology: Instruments and techniques ; 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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    Format: 490 bytes
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  • 10
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    A study of regional waveform calibration in the eastern Mediterranean (2006)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We modeled Pnl phases from several moderate magnitude earthquakes in the eastern Mediterranean to test methods and develop path calibrations for determining source parameters. The study region, which extends from the eastern part of the Hellenic arc to the eastern Anatolian fault, is dominated by moderate earthquakes that can produce significant damage. Our results are useful for analyzing regional seismicity as well as seismic hazard, because very few broadband seismic stations are available in the selected area. For the whole region we have obtained a single velocity model characterized by a 30 km thick crust, low upper mantle velocities and a very thin lid overlaying a distinct low velocity layer. Our preferred model proved quite reliable for determining focal mechanism and seismic moment across the entire range of selected paths. The source depth is also well constrained, especially for moderate earthquakes.
    Description: Published
    Description: N/A or not JCR
    Description: reserved
    Keywords: Body wave propagation ; earthquake parameters ; lithosphere ; upper-mantle ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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