Fracturing of Etnean and Vesuvian rocks at high temperatures and low pressures

Rocchi, Valentina; Sammonds, Peter; Kilburn, Christopher R. J.

doi:10.1016/s0377-0273(03)00342-1

Cited by 56 publications

(41 citation statements)

References 36 publications

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“…It is reasonable to expect that effectively viscous deformation of wall rocks, heated to well above the normal geotherm in proximity of magmatic sources, will influence M a n u s c r i p t 12 the dynamics governing the formation of dikes (Jellinek and DePaolo, 2003;Del Negro et al, 2009). Non-linear rock behavior is consistent with laboratory tests carried out on Etnean rock samples (Rocchi et al, 2004) that revealed an average tensile strength of about 10 MPa and can justify the wide fracture field produced in the northern flank of Etna during the magma propagation.…”

Section: Numerical Resultssupporting

confidence: 83%

3D integrated geophysical modeling for the 2008 magma intrusion at Etna: Constraints on rheology and dike overpressure

Currenti

Napoli

Stefano

et al. 2011

Physics of the Earth and Planetary Interiors

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We present a 3D numerical model based on FEM (Finite Element Method) to jointly evaluate geophysical changes caused by dislocation and overpressure sources in volcanic areas. A coupled numerical problem was solved to estimate ground deformation, gravity and magnetic changes produced by stress redistribution accompanying magma migration within the volcano edifice. We successfully applied the integrated numerical procedure to image the magmatic intrusion occurring in the northern flank of Etna during the onset of the 2008 eruption. A multi-layered crustal structure of the volcano constrained by geological models and geophysical data was considered. Geodetic and gravity data provide information on the strain field, while piezomagnetic changes give constraints on the stress field. Therefore, the integrated modeling gives insights on Mt Etna rheology and dike overpressure involved in the magma propagation and improves understanding of dike emplacement in the northern sector of the volcano. Our FEM-based approach improves the reliability of model-based inference of geophysical parameters obtained during monitoring of the onset of Etna lateral intrusions that can prelude to an impending eruption.

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Section: Numerical Resultssupporting

confidence: 83%

3D integrated geophysical modeling for the 2008 magma intrusion at Etna: Constraints on rheology and dike overpressure

Currenti

Napoli

Stefano

et al. 2011

Physics of the Earth and Planetary Interiors

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“…Strain-rate strengthening is observed and may be a result of increased elasticity as well as crack coalescence lagging behind axial deformation at faster rates (e.g., Jaeger and Cook, 1976). Strain-rate strengthening is observed across all conditions similar to previous studies on volcanic rocks (e.g., Rocchi et al, 2004), but is more effective at high temperature, as was suggested by Lindholm et al (1974). The strain-rate effect implies that slow strain events, such as downslope movement, creep, or shallow magma pooling, could cause more pervasive damage and be more detrimental to the stability of an edifice than fast strain events such as dike intrusions or ground motion produced during earthquakes.…”

Section: Discussionsupporting

confidence: 87%

“…Only recently have laboratory studies begun to systematically investigate the microstructural, physical, and mechanical properties of volcanic rocks, a material infamously known for its formation under disequilibrium conditions, thereby rich in heterogeneities at all scales. These include experiments on a range of material under relevant volcanic conditions such as thermal stressing (Vinciguerra et al, 2005;Kendrick et al, 2013a;Heap et al, 2014a), cyclic inflation-deflation cycles by intrusions (Heap et al, 2009(Heap et al, , 2010Kendrick et al, 2013a), fragmentation (Spieler et al, 2004;Kueppers et al, 2006;Scheu et al, 2008), and flow or fracture at high temperatures and/or pressures (Balme et al, 2004;Rocchi et al, 2004;Smith et al, 2005;Lavallée et al, 2007Lavallée et al, , 2008Benson et al, 2008;Cordonnier et al, 2009;Loaiza et al, 2012;Kendrick et al, 2013b).…”

Section: Introductionmentioning

confidence: 99%

Geomechanical rock properties of a basaltic volcano

et al. 2015

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In volcanic regions, reliable estimates of mechanical properties for specific volcanic events such as cyclic inflation-deflation cycles by magmatic intrusions, thermal stressing, and high temperatures are crucial for building accurate models of volcanic phenomena. This study focuses on the challenge of characterizing volcanic materials for the numerical analyses of such events. To do this, we evaluated the physical (porosity, permeability) and mechanical (strength) properties of basaltic rocks at Pacaya Volcano (Guatemala) through a variety of laboratory experiments, including: room temperature, high temperature (935 • C), and cyclically-loaded uniaxial compressive strength tests on as-collected and thermally-treated rock samples. Knowledge of the material response to such varied stressing conditions is necessary to analyze potential hazards at Pacaya, whose persistent activity has led to 13 evacuations of towns near the volcano since 1987. The rocks show a non-linear relationship between permeability and porosity, which relates to the importance of the crack network connecting the vesicles in these rocks. Here we show that strength not only decreases with porosity and permeability, but also with prolonged stressing (i.e., at lower strain rates) and upon cooling. Complimentary tests in which cyclic episodes of thermal or load stressing showed no systematic weakening of the material on the scale of our experiments. Most importantly, we show the extremely heterogeneous nature of volcanic edifices that arise from differences in porosity and permeability of the local lithologies, the limited lateral extent of lava flows, and the scars of previous collapse events. Input of these process-specific rock behaviors into slope stability and deformation models can change the resultant hazard analysis. We anticipate that an increased parameterization of rock properties will improve mitigation power.

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“…In Figure 10 we have included other published data on basalt. The Vesuvian sample investigated by Rocchi et al [2004] was a porphyritic basalt made up of 20% euhedral phenocrysts and 80% glassy/cryptocrystalline groundmass, with numerous macropores up to 1 mm in diameter. The Stromboli basalt investigated by Heap et al [2010] was made up of 40% phenocrysts and 60% microcrystalline groundmass, with significant crack porosity attributed to rapid thermal cooling.…”

Section: 1002/2016jb012826mentioning

confidence: 99%

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

et al. 2016

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Understanding how the strength of volcanic rocks varies with stress state, pressure, and microstructural attributes is fundamental to understanding the dynamics and tectonics of a volcanic system and also very important in applications such as geothermics or reservoir management in volcanic environments. In this study we investigated the micromechanics of deformation and failure in basalt, focusing on samples from Mount Etna. We performed 65 uniaxial and triaxial compression experiments on nominally dry and water‐saturated samples covering a porosity range between 5 and 16%, at effective pressures up to 200 MPa. Dilatancy and brittle faulting were observed in all samples with porosity of 5%. Water‐saturated samples were found to be significantly weaker than comparable dry samples. Shear‐enhanced compaction was observed at effective pressures as low as 80 MPa in samples of 8% porosity. Microstructural data revealed the complex interplay of microcracks, pores, and phenocrysts on dilatant failure and inelastic compaction in basalt. The micromechanics of brittle failure is controlled by wing crack propagation under triaxial compression and by pore‐emanated cracking under uniaxial compression especially in the more porous samples. The mechanism of inelastic compaction in basalt is cataclastic pore‐collapse in agreement with a recent dual‐porosity model.

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Fracturing of Etnean and Vesuvian rocks at high temperatures and low pressures

Cited by 56 publications

References 36 publications

3D integrated geophysical modeling for the 2008 magma intrusion at Etna: Constraints on rheology and dike overpressure

3D integrated geophysical modeling for the 2008 magma intrusion at Etna: Constraints on rheology and dike overpressure

Geomechanical rock properties of a basaltic volcano

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

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