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  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (5)
  • 04. Solid Earth::04.04. Geology::04.04.09. Structural geology  (3)
  • 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
  • Agu  (7)
  • Blackwell Publishing Ltd  (2)
  • Annual Reviews
  • 2005-2009  (9)
  • 1980-1984
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  • 1
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    A thermal pressurization model for the spontaneous ...: 2. Traction evolution and dynamic parameters (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: We investigate the dynamic traction evolution during the spontaneous propagation of a 3-D earthquake rupture governed by slip-weakening or rate- and state-dependent constitutive laws and accounting for thermal pressurization effects. The analytical solutions as well as temperature and pore pressure evolutions are discussed in the companion paper by Bizzarri and Cocco. Our numerical experiments reveal that frictional heating and thermal pressurization modify traction evolution. The breakdown stress drop, the characteristic slip-weakening distance, and the fracture energy depend on the slipping zone thickness (2w) and hydraulic diffusivity (w). Thermally activated pore pressure changes caused by frictional heating yield temporal variations of the effective normal stress acting on the fault plane. In the framework of rate- and state-dependent friction, these thermal perturbations modify both the effective normal stress and the friction coefficient. Breakdown stress drop, slip-weakening distance, and specific fracture energy (J/m2) increase for decreasing values of hydraulic diffusivity and slipping zone thickness. We propose scaling relations to evaluate the effect of w and w on these physical parameters. We have also investigated the effects of choosing different evolution laws for the state variable. We have performed simulations accounting for the porosity evolution during the breakdown time. Our results point out that thermal pressurization modifies the shape of the slip-weakening curves. For particular configurations, the traction versus slip curves display a gradual and continuous weakening for increasing slip: in these cases, the definitions of a minimum residual stress and the slip-weakening distance become meaningless.
    Beschreibung: Published
    Beschreibung: B05304
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): thermal pressurization ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.02. Exploration geophysics::04.02.03. Heat flow ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 2
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    Unbekannt
    Evidence of seismic deformation of the paved floor of the decumanus at Tindari (NE, Sicily) (2008)
    Blackwell Publishing Ltd
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: Most of the ancient town of Tindari (NE, Sicily) was settled on a plateau the most surficial layer of which was made of unconsolidated material. Ongoing excavations at the archaeological site at Tindari uncovered a large portion of the decumanus which suffered deformations preliminarily assigned to coseismic effects. An analysis of the local dynamic response through the simulation of strong seismic shaking to the bedrock and modelling of spectral ratios of the bedrock-soft soil was carried out to verify the susceptibility of superficial terrains of the promontory to coseismic deformations. To perform this simulation the finite element method (FEM) was used. Four accelerometric recordings of three earthquakes of medium-high magnitude, recorded on rocky sites, were chosen to simulate the seismic shaking, using a constitutive law for the materials composing the promontory layers both of linear-elastic type and of elastoplastic type. The analysis of the linear-elastic field allowed the definition of the frequencies for which the spectral ratios of the accelerations recorded the highest amplifications; in particular the frequency range 31.5–37.2 Hz can be combined with deformation of the paved floor of the decumanus. The analysis in the elastoplastic field highlighted the zones of promontory more susceptible to suffer plasticization process. The results show that the topmost layer of the decumanus is the most susceptible to suffer plasticization. Therefore, the performed analysis lends greater support to the hypothesis that the deformations were produced by seismic shaking.
    Beschreibung: Published
    Beschreibung: 213-222
    Beschreibung: 3.10. Sismologia storica e archeosismologia
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Fourier analysis ; Elasticity and anelasticity ; Earthquake ground motions ; Site effects ; Computational seismology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Tomomorphometry of the Somma-Vesuvius volcano (Italy) (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: A tomomorphometric analysis of the Somma-Vesuvius topography is presented. This consists in extracting horizontal cross sections at different altitudes, and in determining some morphometric parameters: radius of the circle with a surface area equal to the cross section, circularity, ratio between the major and minor axis of the best fitting ellipse, orientation a of the ellipse major axis, and the x-y centroid. The Somma includes three portions: the apron zone, the flanks, and the summit caldera boundary. Between 225 m and 525 m, a is 50 –60 . Between 600 m and 775 m, a is 130 –135 . These are the preferred strike of the eruptive fissures affecting the northwestern Somma flanks, the faults affecting the whole edifice, the nodal planes from local earthquakes. The Somma activity developed along a NE-SW structural discontinuity, whereas the post-caldera activity concentrated along a NW-SE striking structure. Somma activity migrates from SE to NW.
    Beschreibung: Published
    Beschreibung: L17305
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Tomomorphometry ; Somma-Vesuvius volcano ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: We show that the low-pass filtered, peak amplitudes of initial P- and S-wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real-time estimation of the event size in seismic early warning applications. The earthquake size can be therefore estimated using only a couple of seconds of signal from the P- or S-wave onsets, i.e. while the rupture itself is still propagating and rupture dimension is far from complete. We argue that dynamic stress release and/or slip duration on the fault in the very early stage of seismic fracture, scales both with the observed peak amplitude and with the elastic energy available for fracture propagation. The probability that a fracture grows to a larger size should scale with the energy initially available.
    Beschreibung: Published
    Beschreibung: L23312
    Beschreibung: JCR Journal
    Beschreibung: partially_open
    Schlagwort(e): Earthquake ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    A thermal pressurization model for the spontaneous dynamic rupture propagation on a three-dimensional fault: 1. Methodological approach (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: We investigate the role of frictional heating and thermal pressurization on earthquake ruptures by modeling the spontaneous propagation of a three-dimensional (3-D) crack on a planar fault governed by assigned constitutive laws and allowing the evolution of effective normal stress. We use both slip-weakening and rate- and state-dependent constitutive laws; in this latter case we employ the Linker and Dieterich evolution law for the state variable, and we couple the temporal variations of friction coefficient with those of effective normal stress. In the companion paper we investigate the effects of thermal pressurization on the dynamic traction evolution. We solve the 1-D heat conduction equation coupled with Darcy’s law for fluid flow in porous media. We obtain a relation that couples pore fluid pressure to the temperature evolution on the fault plane. We analytically solve the thermal pressurization problem by considering an appropriate heat source for a fault of finite thickness. Our modeling results show that thermal pressurization reduces the temperature increase caused by frictional heating. However, the effect of the slipping zone thickness on temperature changes is stronger than that of thermal pressurization, at least for a constant porosity model. Pore pressure and effective normal stress evolution affect the dynamic propagation of the earthquake rupture producing a shorter breakdown time and larger breakdown stress drop and rupture velocity. The evolution of the state variable in the framework of rate- and state-dependent friction laws is very different when thermal pressurization is active. In this case the evolution of the friction coefficient differs substantially from that inferred from a slip-weakening law. This implies that the traction evolution and the dynamic parameters are strongly affected by thermal pressurization.
    Beschreibung: Published
    Beschreibung: B05303
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): thermal pressurization ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.02. Exploration geophysics::04.02.03. Heat flow ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 6
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    Unbekannt
    Evidence of instantaneous dynamic triggering during the seismic sequence of year 2000 in south Iceland (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: We analyze the coseismic stress perturbation during the 17 June 2000 south Iceland seismic sequence; the main shock (Ms 6.6) was followed by three large events within a few tens of seconds (8, 26, and 30 s) located within 80 km. The aim of this paper is to investigate short-term fault interaction and instantaneous triggering. This happens when a fault perturbed by a stress change fails before the end of the transient stress perturbation. We compute the shear, normal, and Coulomb stress changes as functions of time in a stratified elastic half-space by using discrete wave number and reflectivity methods. We calculate dynamic stresses caused by the main shock at the hypocenters of these three subsequent events. Our numerical results show that the onset of the last two events is slightly delayed with respect to the arrival time of the second positive peak of Coulomb stress variation, while the first event occurred after the first positive stress peak. We have also analyzed the response of a spring slider system representing a fault governed by a rate- and state-dependent friction law, perturbed by shear and normal stress variations caused by the main shock. The fault response to the computed stress perturbations is always clock advanced. We have found suitable constitutive parameters of the modeled fault that allow the instantaneous dynamic triggering of these three earthquakes. If the initial sliding velocity is comparable with the tectonic loading velocity, we obtained failure times close to the observed origin times for low values of the initial effective normal stress.
    Beschreibung: Published
    Beschreibung: B03302
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): seismic sequence ; Iceland ; 2000 ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 7
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    Coseismic ruptures and associated tectonic landforms along the Duzce segment of the North Anatolian Fault Zone (2007)
    Agu
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: This paper presents a comparison between the pattern of surface ruptures produced by a single earthquake and patterns of cumulative deformation. We performed a detailed study of the 1999 earthquake coseismic ruptures and of the long-term tectonic landforms in a key area of the Du¨zce fault segment of the North Anatolian fault. We observed a scaleindependent en echelon arrangement of the coseismic surface ruptures. As a whole, the long-term geomorphic expression of the Du¨zce Fault near the 1999 ruptures is evidence of the principal slip zone at depth that accommodates the bulk of the displacement during an individual rupture event. This may stay localized through many rupture episodes with persistent geometry and kinematics. The long-term tectonic and geomorphic expression of the fault in a broader area around the 1999 ruptures defines a wider deformation zone. In fact, an old and complex fault arrangement has been mapped, partially coinciding with the 1999 rupturing fault, suggesting that the 1999 ruptures are an incomplete expression of the long-term Du¨zce fault system. The relationships between the coseismic and the old fault systems suggest an evolution of the fault pattern trough time, with a tendency to simplify a geometric complexity into a straighter, mature trace. The integrated investigation of long-term tectonic morphologies and structural pattern offers a noteworthy frame to interpret the coseismic rupture kinematics and clarifies their complexities. Moreover, to fully understand the principal slip zone at depth, this work shows the importance of the study of strain distribution pattern and evolution of surface rupturing faults.
    Beschreibung: Published
    Beschreibung: B06312
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Coseismic ruptures ; tectonic ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 8
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    Multiple hydro-fracturing by boron-rich fluids in the Late Miocene contact aureole of eastern Elba Island (Tuscany, Italy) (2008)
    Blackwell Publishing Ltd
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: In eastern Elba Island (Tuscany, Italy), a shallow crustal level felsic, tourmaline-bearing, dyke-sill swarm of Late Miocene age is associated with abundant tourmaline-quartz hydrothermal veins and metasomatic masses. Development of these veins and masses in the host rocks demonstrates multiple hydro-fracturing by magmatic, boron-rich saline fluid. Tourmalines in felsic dykes are schorl, whereas in veins and metasomatic masses, tourmaline composition ranges from schorl-dravite through dravite to uvite. This compositional shift is evidence for an increasing contribution to the magmatic boron-rich fluids by a Mg-Ca-Ti-rich external component represented by biotite-rich and amphibolite host rocks. This system can be envisaged as an exposed proxy of the high temperature hydrothermal system presently active in the deepest part of the Larderello-Travale geothermal field (Tuscany).
    Beschreibung: Published
    Beschreibung: 318-326
    Beschreibung: 3.3. Geodinamica e struttura dell'interno della Terra
    Beschreibung: 3.5. Geologia e storia dei sistemi vulcanici
    Beschreibung: JCR Journal
    Beschreibung: reserved
    Schlagwort(e): Hydro-fractures ; geothermal systems ; Magmatism ; southern Tuscany ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Long-term seismogenesis in Greece: Comparison of the evolving stress field and precursory scale increase approaches (2007)
    Agu
    Details
    Publikationsdatum: 2024-05-09
    Beschreibung: Recent strong (M 6.6) earthquakes in Greece are examined from the point of view of two current, but disparate, approaches to long-term seismogenesis. These are the evolving stress field (ESF) approach, in which earthquakes are considered to be triggered by accumulated stress changes from past earthquakes and tectonic loading on the major faults, and the precursory scale increase (Y) approach, in which a major earthquake is preceded in the long term by an increase in minor earthquake occurrences, with the magnitude of the precursory earthquakes, and the precursor time and area all scaling with the major earthquake magnitude. The strong earthquakes are found to be consistent with both approaches, and it is inferred that both approaches have a relevant role to play in the description of the long-term generation process of major earthquakes. A three-stage faulting model proposed previously to explain the Y phenomenon involves a major crack, which eventually fractures in the major earthquake, being formed before the onset of precursory seismicity. Hence we examine whether ESF can account for the formation of the major crack by examining the accumulated stress changes at the time of the onset of Y for each strong earthquake. In each case, the answer is in the affirmative; there is enhanced stress in the vicinity of the main shock at the time of the onset. The same is true for most, but not all, of the locations of precursory earthquakes.
    Beschreibung: Published
    Beschreibung: B05318
    Beschreibung: reserved
    Schlagwort(e): seismogenesis ; Greece: ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
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