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  • 1
    Electronic Resource
    Electronic Resource
    On the interpretation of slow ground deformation precursory to the 1976 Friuli earthquake (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 781-792 
    Details
    ISSN: 1420-9136
    Keywords: Precursory tilt ; aseismic slip ; thrust faulting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract During three years preceding the 1976 Friuli earthquake, a continuous southward ground tilt was recorded by a tiltmeter placed near Tolmezzo, 15 km north-west of the epicentre of the impending earthquake. The cumulative ground tilt amounted to as much as 3 minutes of arc. Since the tiltmeter was placed in the proximity of an active fault, such a tilt can be explained if the fault slipped aseismically on its shallower section during the same three year period. Aseismic slip on the fault might have been caused by the same mechanism which concentrated stress in the region and eventually produced the 1976 earthquake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876384
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  • 2
    Electronic Resource
    Electronic Resource
    A viscoelastic shear zone model of compressional and extensional plate boundaries (1993)
    Springer
    Pure and applied geophysics 140 (1993), S. 471-491 
    Details
    ISSN: 1420-9136
    Keywords: Sheart zone ; compressional and extensional boundary zone ; brittle-ductile transition ; viscoclastic model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A model is proposed describing the mechanical evolution of a shear zone along compressional and extensional plate boundaries, subject to constant strain rate. The shear zones are assumed as viscoelastic with Maxwell rheology and with elastic and rheological parameters depending on temperature and petrology. Stress and strain are computed as functions of time and depth. For both kinds of boundaries the model reproduces the existence of a shallow seismogenic zone, characterized by a stress concentration. The thickness of the seismogenic layer is evaluated considering the variations of shear stress and frictional strength on faults embedded in the shear zone. Assuming that a fault dislocation takes place, the brittle-ductile transition is assumed to occur at the depth at which the time derivative of total shear stress changes from positive to negative values. The effects of different strain rates and geothermal gradients on the depth of the brittle-ductile transition are studied. The model predictions are consistent with values inferred from seismicity data of different boundary zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876966
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  • 3
    Electronic Resource
    Electronic Resource
    Depth of the brittle-ductile transition in a transcurrent boundary zone (1991)
    Springer
    Pure and applied geophysics 135 (1991), S. 447-461 
    Details
    ISSN: 1420-9136
    Keywords: Shear zone ; brittle-ductile transition ; transcurrent faults
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A model is proposed which describes the boundary zone between two transcurrent plates as a viscoelastic body, with rheological properties changing with depth. In this model, the brittle-ductile transition is defined as the depth at which the time derivative of shear stress changes from positive to negative values. Variations of this depth are studied as functions of geothermal gradient, rheological parameters and strain rate, using a “power law” rheology with exponent ranging from 1 to 4. Stress relaxation in the ductile zone is controlled by a local characteristic time, which depends on petrology, temperature and, in the case of non-Newtonian rheology, on strain rate. The composition and the hydration degree of crustal rocks may also sensibly influence the depth of the brittle-ductile transition. The model predictions are compared with observations regarding the San Andreas, Imperial Valley and North Anatolian Faults: it is found that values ofn from 1 to 3 are more appropriate to reproduce the transition depth inferred by the seismicity distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879474
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  • 4
    Electronic Resource
    Electronic Resource
    Viscous Newtonian laminar flow in a rectangular channel: application to Etna lava flows (1999)
    Springer
    Bulletin of volcanology 61 (1999), S. 40-47 
    Details
    ISSN: 1432-0819
    Keywords: Key words Lava flow ; Lava rheology ; Viscous flow ; Effusion rate ; Channel flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We introduce a 3D model for near-vent channelized lava flows. We assume the lava to be an isothermal Newtonian liquid flowing in a rectangular channel down a constant slope. The flow velocity is calculated with an analytical steady-state solution of the Navier-Stokes equation. The surface velocity and the flow rate are calculated as functions of the flow thickness for different flow widths, and the results are compared with those of a 2D model. For typical Etna lava flow parameters, the influence of levees on the flow dynamics is significant when the flow width is less than 25 m. The model predicts the volume flow rate corresponding to the surface velocity, taking into account that both depend on flow thickness. The effusion rate is a critical parameter to evaluate lava flow hazard. We propose a model to calculate the effusion rate given the lava flow width, the topograhic slope, the lava density, the surface flow velocity, and either the lava viscosity or the flow thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050261
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  • 5
    Electronic Resource
    Electronic Resource
    A dislocation model of aseismic fault slip under nonuniform friction (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 4 (1992), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A model is proposed for studying the mechanical behaviour of faults during their interseismic periods. The model considers a plane fault surface in an elastic medium, subject to a uniform shear stress which increases slowly with time. A1-D friction distribution is assumed on the fault, characterized by asperities and a weaker zone. The traction vector on the fault plane has an arbitrary orientation: in particular, it can be nonperpendicular to the asperity borders. Aseismic fault slip takes place when the applied stress exceeds the frictional resistance: slip starts in weak zones and is confined by asperities, where it propagates at increasing velocity. Propagation into asperities is characterized by a dislocation front, advancing perpendicularly to the asperity border. Fault slip does not take prate in the direction of traction, except when traction is perpendicular or parallel to the asperity border. The propagation of such aseismic dislocations produces a stress redistribution along the fault and can play a key role in determining the conditions which give rise to earthquakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.1992.tb00586.x
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  • 6
    Electronic Resource
    Electronic Resource
    A dynamical model of lava flows cooling by radiation (1989)
    Springer
    Bulletin of volcanology 51 (1989), S. 88-95 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The behaviour of a lava flow is reproduced by a two-dimensional model of a Bingham liquid flowing down a uniform slope. Such a liquid is described by two rheological parameters, yield stress and viscosity, both of which are strongly temperature-dependent. Assuming a flow rate and an initial temperature of the liquid at the eruption vent, the temperature decrease due to heat radiation and the consequent change in the rheological parameters are computed along the flow. Both full thermal mixing and thermal unmixing are considered. The equations of motion are solved analytically in the approximation of a slow downslope change of the flow parameters. Flow height and velocity are obtained as functions of the distance from the eruption vent; the time required for a liquid element to reach a certain distance from the vent is also computed. The gross features of observed lava flows are reproduced by the model which allows us to estimate the sensitivity of flow dynamics to changes in the initial conditions, ground slope and rheological parameters. A pronounced increase in the rate of height increase and velocity decrease is found when the flow enters the Bingham regime. The results confirm the observation according to which lava flows show an initial rapid advance, followed by a marked deceleration, while the final length of a flow is such that the Graetz number is in the order of a few hundreds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081978
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  • 7
    Electronic Resource
    Electronic Resource
    The historic and artistic heritage facing the earthquake risk: The Italian case (1992)
    Springer
    Natural hazards 5 (1992), S. 269-278 
    Details
    ISSN: 1573-0840
    Keywords: Historic and artistic buildings ; architecture ; seismic risk ; value analysiskw ; Italy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The problem of protection against earthquakes in Italy is made difficult by the presence of a huge historic and artistic heritage. Such a heritage is mainly made up of ancient buildings and monuments situated in the urban centres, which are densely distributed throughout Italy. Therefore, very complex problems are met in the determination of the value parameter concurring with the determination of seismic risk, in addition to hazard and vulnerability. An indication of the monetary value of a building is not sufficient as far as the cultural heritage is concerned: different criteria are necessary in order to distinguish which are the strategic buildings. If we consider that there are more than 2000 museums in Italy, most of which are placed inside historic buildings, it appears that museums should receive the highest priority in future initiatives for seismic rehabilitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125231
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  • 8
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    A dislocation model of aseismic fault slip under nonuniform friction (1992)
    Wiley
    Details
    Publication Date: 1992-04-01
    Print ISSN: 0954-4879
    Electronic ISSN: 1365-3121
    Topics: Geosciences
    Published by Wiley
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  • 9
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    A model for the atmospheric shock wave produced by a strong volcanic explosion (2020)
    Oxford University Press
    Details
    Publication Date: 2020-05-07
    Description: SUMMARY Atmospheric shock waves are a common phenomenon in explosive volcanic eruptions. We consider the motion of a spherical shock wave generated by a point source in the strong shock approximation. The shock front corresponds to discontinuities in the gas velocity, density, pressure and temperature, which are calculated as functions of the energy of the explosion. The problem is solved analytically for the distributions of velocity, density, pressure and temperature in the atmosphere as functions of the distance from the source. The motion of the shock wave being supersonic, the solution is valid for a few seconds after the explosion, corresponding to a distance of few kilometres. The acoustic effect of the shock wave, expressed by the peak sound pressure level, is calculated and may reach hundreds of decibels. The pressure waveform that could be recorded in the vicinity of the volcano is calculated and compared with typical waveforms in weak shock conditions. The change in the refractive index of air due to density inhomogeneity is calculated and the conditions under which a condensation cloud is formed behind the shock front are investigated.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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  • 10
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    A Fault Model with Two Asperities of Different Areas and Strengths (2018)
    Springer
    Details
    Publication Date: 2018-04-09
    Print ISSN: 1874-8961
    Electronic ISSN: 1874-8953
    Topics: Geosciences , Mathematics
    Published by Springer
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