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  • 1
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    Understanding Slow Deformation Before Dynamic Failure (2011)
    Springer Science+Business Media B.V.
    Details
    Publication Date: 2017-04-04
    Description: Slow deformation and fracturing have been shown to be leading mechanisms towards failure, marking earthquake ruptures, flank eruption onsets and landslide episodes. The common link among these processes is that populations of microcracks interact, grow and coalesce into major fractures. We present (a) two examples of multidisciplinary field monitoring of characteristic “large scale” signs of impending deformation from different tectonic setting, i.e. the Ruinon landslide (Italy) and Stromboli volcano (Italy) (b) the kinematic features of slow stress perturbations induced by fluid overpressures and relative modelling; (c) experimental rock deformation laboratory experiments and theoretical modelling investigating slow deformation mechanisms, such stress corrosion crack growth. We propose an interdisciplinary unitary and integrated approach aimed to: (1) transfer of knowledge between specific fields, which up to now aimed at solve a particular problem; (2) quantify critical damage thresholds triggering instability onset; (3) set up early warning models for forecasting the time of rupture with application to volcanology, seismology and landslide risk prevention.
    Description: Published
    Description: 229-247
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: reserved
    Keywords: Stromboli volcano · Landslides ; 02. Cryosphere::02.02. Glaciers::02.02.01. Avalanches ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 05. General::05.02. Data dissemination::05.02.02. Seismological data ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.01. Environmental risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 2
    Electronic Resource
    Electronic Resource
    Elastic waves scattering and radiation by fractal inhomogeneity of a medium (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 110 (1992), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: I obtain the Born approximation for the scattered intensity I, the differential cross-sections σd, and the total scattering cross-sections σ of elastic wavefields scattered by a mass fractal, an object with a fractal surface and a fragment of a turbulent medium. The results for I and σd are valid for an arbitrary anisotropic random discrete or continuous inhomogeneity and they are in agreement with the well known results for discrete inclusions (Gubernatis, Domany & Krumhansl 1977b). For fractal inhomogeneities I show that: (1) for small angle scattering I∝ω4+ω(sin θ/2)n̈, where θ is a scattering angle and the constant n̈ depends linearly on the fractal dimension; (2) σ∝ω4+ω; (3) σ∝ω4+n̈ if n̈〉-2 and σ∝ω2 if n̈≤ -2; and (4) the Fourier transform of the correlation function of the wavefield Γ which is coherently radiated by white noise point sources distributed on fractal objects obeys [Γ] ∝ωσ. Applying the results for σd I show that the model of inhomogeneities with a fractal surface is in agreement with the fractal dimensions of some fault systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1992.tb02094.x
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  • 3
    Electronic Resource
    Electronic Resource
    Seismic Attenuation By Scattering: Theory and Numerical Results (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 114 (1993), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Estimates of seismic wave attenuation are strongly affected by scattering. Scattering is an important effect caused by interaction of seismic wavefields with inhomogeneities of hydrocarbon reservoirs, Earth's crust and mantle. In order to study the contribution of scattering to apparent attenuation we consider plane-wave propagation in acoustic 2-D and 3-D inhomogeneous media. Different attenuation estimates result depending on what wavefield function is being averaged during corresponding processing. By wave-theoretical analysis and high-order finite difference modelling in two dimensions we show that scattering attenuation estimates derived from the mean of amplitude spectra and from the mean logarithm of amplitude spectra depend on travel distance. For not too long travel distances, where the coherent part of the wavefield dominates, we give an analytical description of these estimates. In 2-D and 3-D the relations are established between the autocorrelation functions of velocity fluctuations of a random medium and the autocorrelation functions of amplitude and phase fluctuations on a receiver line perpendicular to the general propagation direction of an originally plane wave. For long distances, where the wavefield fluctuates strongly, we show that both mean logarithm of amplitude and logarithm of mean amplitude tend to constants. They differ approximately by a factor two in both scattering regimes. the scattering attenuation coefficient of the meanfield is not dependent on travel distance. We compared our theoretical results with numerical calculations and found excellent agreements. the concept presented clarifies the nature of seismic Q estimations in the presence of scattering and can help to yield statistical earth models from seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1993.tb03925.x
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of random isotropic inhomogeneities on the phase velocity of seismic waves (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 127 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In this paper we study, theoretically and numerically, the influence of 2-D and 3-D random isotropic stationary inhomogeneities on the phase velocities of the transmitted compressional wavefield of an initially plane (or spherical) wave. Due to scattering by the inhomogeneities the wavefield becomes distorted as the wave propagates through the medium. The traveltimes fluctuate when considering different wavefield registrations acquired at the points of surfaces that are parallel to the wavefront of the initial wave. It is usually observed that the slowness obtained from the averaged traveltime differs from the averaged slowness of (he medium. In the geophysical lilerature this effect has been termed the ‘velocity shift’.Using the Rytov approximation we establish formulas for the frequency- and travel-distance-dependent phase velocity of the transmitted wavefield in 2-D and 3-D randomly inhomogeneous media. We also compare our analytical results with finite-difference simulations. Good agreement between numerical simulations and theory is observed. The low-frequency limit of our analytical results coincides with the known effective-medium limit of the phase velocity in statistically isotropic inhomogeneous fluids with constant densities. In the high-frequency limit our results coincide with the results previously obtained by the ray-perturbation theory. However, in contrast to the ray theory, our description is not restricted to media with differentiate correlation functions of fluctuations. Moreover, our results quantify the frequency dependence of the velocity shift in the intermediate-frequency range. This frequency dependence is of major importance for estimating this effect in realistic situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb04057.x
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature variation of the H0 acidity function in aqueous sulfuric acid solution (1969)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 91 (1969), S. 6654-6662 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01052a021
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  • 6
    Electronic Resource
    Electronic Resource
    Consistency of the indicator overlap method with linear free energy--enthalpy correlations (1970)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 92 (1970), S. 1567-1568 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00709a023
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  • 7
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    High-resolution image of the North Chilean subduction zone: seismicity, reflectivity and fluids (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-20
    Description: We obtained high-precision locations for 5250 earthquakes in the Iquique segment of the northern Chilean subduction zone from two temporary local seismic networks around 21°S. A double seismic zone in the downgoing Nazca slab can be clearly identified. One band of seismicity is located at the plate interface and a second one 20–25 km deeper in the oceanic mantle. It can be traced updip to uncommonly shallow levels of 50 km. A combined interpretation of seismicity and reflectivity along the seismic ANCORP’96 experiment suggests the prevalence of fluid processes in the subducted oceanic crust as well as in the uppermost 20 km of the mantle. Crustal seismicity is pervasive below the Coastal Cordillera. Beneath the Precordillera, the lower bound of crustal seismicity delineates a sharp west-dipping boundary down to 20 km depth, consistent with earlier findings indicating a rheological boundary.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
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    Microseismic reflection imaging of the Central Andean crust (2016)
    Oxford University Press
    Details
    Publication Date: 2016-01-08
    Description: The coda of passive seismic recordings is often rich in arrivals that are coherent across several stations. If reflections can be extracted, then they may be used for seismic reflection subsurface imaging. With the objective to image the upper crust of the North Chilean Precordillera (Central Andes; approximate location 21°S 69°W), we developed a workflow to process passive seismic data into subsurface reflection images. We analysed the waveform recordings of several hundred microseismic events using signal processing and imaging techniques adapted from active (controlled source) seismic imaging as used in the oil industry. Key processing steps involved precise arrival time picking and hypocentre determination, removing signal amplitude variations due to varying source radiation patterns, identification and separation of reflections from coherent noise, and transformation of the processed waveforms into images of the subsurface reflectivity. When designing our microseismic reflection imaging workflow, we took advantage of the fact that the passive seismic recording geometry with the hypocentres located at depth and the receivers positioned at the surface resembles a reverse vertical-seismic profiling experiment. The resultant P - and S -wave reflection images reveal several reflective features, such as an approximate 15° westward dipping reflector over the 5–25 km depth range that largely coincides with a distinct seismicity boundary. We interpret the imaged interface as the brittle-ductile transition zone boundary, possibly enhanced by a tectonic shear zone. For the area of the North Chilean Precordillera, the deduced microseismic reflection sections with horizontal extensions of about 50 km represent the first high-resolution images of the shallow crust, which could not be obtained from previous active-source seismic-reflection data.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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