The tensile strength of volcanic rocks: Experiments and models

Heap, Michael; Wadsworth, Fabian B.; Heng, Zhen; Xu, Tao; Griffiths, Luke; Velasco, Andrea Aguilar; Vairé, Emma; Vistour, Marie; Reuschlé, Thierry; Troll, Valentin R.; Deegan, Frances M.; Tang, Chun’an

doi:10.1016/j.jvolgeores.2021.107348

Cited by 19 publications

(24 citation statements)

References 123 publications

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“…Experimental studies have shown that alteration can influence the strength of volcanic rock (del Potro & Hürlimann, 2009; Farquharson et al., 2019; Frolova et al., 2014; Heap, Gravley, et al., 2020; Heap, Wadsworth, et al., 2021, Mordensky et al., 2018, 2019; Wyering et al., 2014). The type of alteration, porosity increasing dissolution and alteration to clay (del Potro & Hürlimann, 2009; Farquharson et al., 2019; Opfergelt et al., 2006; Watters & Delahaut, 1995) or porosity decreasing mineral precipitation (Heap, Gravley, et al., 2020; Heap, Baumann, et al., 2021; Heap, Wadsworth, et al., 2021), dictates whether the alteration decreases or increases the strength and Young's modulus of the rock. Figures 5c and 5d show plots of uniaxial compressive strength and Young's modulus, respectively, as a function of the percentage of secondary minerals for the rocks from La Soufrière.…”

Section: Discussionmentioning

confidence: 99%

“…Our triaxial data highlight that alteration (percent of secondary minerals) reduces rock cohesion, but does not systematically influence the angle of internal friction (Figure 4). Experimental studies have shown that alteration can influence the strength of volcanic rock (del Potro & Hürlimann, 2009; Farquharson et al., 2019; Frolova et al., 2014; Heap, Gravley, et al., 2020; Heap, Wadsworth, et al., 2021, Mordensky et al., 2018, 2019; Wyering et al., 2014). The type of alteration, porosity increasing dissolution and alteration to clay (del Potro & Hürlimann, 2009; Farquharson et al., 2019; Opfergelt et al., 2006; Watters & Delahaut, 1995) or porosity decreasing mineral precipitation (Heap, Gravley, et al., 2020; Heap, Baumann, et al., 2021; Heap, Wadsworth, et al., 2021), dictates whether the alteration decreases or increases the strength and Young's modulus of the rock.…”

Section: Discussionmentioning

confidence: 99%

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Alteration‐Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

et al. 2021

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Volcanoes are inherently unstable structures that are built haphazardly, in both space and time, from the products of successive effusive and explosive eruptions and endogenous growth. These materials have highly variable physical and mechanical properties (Heap & Violay, 2021) and often form oversteepened and unstable slopes. As a result, volcano deformation (such as volcano spreading; Borgia et al., 2000) and mass wasting events (such as debris avalanches resulting from partial flank collapse, lahars, and rockfalls;

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Alteration‐Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

et al. 2021

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“…Given an edifice density of 1,800 kg/m 3 and a differential tectonic stress of 2 MPa, the dike overpressure needed to initiate the stress rotation is >10 MPa (Figure 4a), equivalent to the tensile strength of low‐porosity andesitic rocks from the laboratory tests (Heap et al., 2021). It is possible that the dike overpressure might be built beneath a sealed andesitic lava dome from the 1986 eruption before it broke the seal, as proposed by the previous studies (Cervelli et al., 2006; Power & Lalla, 2010).…”

Section: Discussionmentioning

confidence: 99%

Earthquakes Indicated Stress Field Change During the 2006 Unrest of Augustine Volcano, Alaska

Zhan

Roman

Mével

et al. 2022

Geophysical Research Letters

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The crustal stress field around a volcano is affected by many competing and temporally varying factors, such as gravitational loading, tectonic processes, pre-existing structures, and pressurizing and ascending magmas or hydrothermal fluids. Volcano tectonic (VT) earthquakes, indicating shear ruptures, often provide early warnings of volcanic unrest and reveal stress changes due to magma or hydrothermal fluid (Roman & Cashman, 2006). Unfortunately, the absolute magnitude of stresses triggering the volcano tectonic (VT) seismicity cannot be measured directly. However, the relative influence of different sources, such as dike opening and tectonic processes, on the stress field can be inferred from the stress orientation or its changes (Bonafede & Danesi, 1997). For example, a ∼90° rotation of the fault plane solution (FPS) P-axis from regional maximum compression is sometimes observed when a dike opens (Fukuyama et al., 2001;Roman et al., 2021), indicating a possible reorientation in the local stress field. From numerical modeling, the influence of tectonically-and magmatically generated stress fields on the local stress field can be quantified (Roman & Heron, 2007;Vargas-Bracamontes & Neuberg, 2012). However, the effect of gravitational loading due to volcanic edifices is usually ignored, and a systematic study integrating numerical models with seismicity and geodetic data from an active volcanic system is needed.Geophysical monitoring of the 2006 eruption of Augustine Volcano in Cook Inlet, Alaska (Figure 1) provides a wealth of data with which to study the stress field changes during its unrest and subsequent eruption. Starting on 30 April 2005, the number of volcano tectonic (VT) earthquakes generally increased from several to >1,000 per

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“…Alternative analyses consider the role of horizontal pore pressure gradients and locally‐induced gradients, and outline the impact on failure (e.g., Gerbault et al., 2012; Rozhko et al., 2007). Notably, the assumption of pore fluids adjacent to a reservoir (Lister & Kerr, 1991; Rubin, 1995) suggests porosity of the surrounding crustal rock, which has been shown to impact key physical properties of the rock (e.g., Heap et al., 2021; Heap & Violay, 2021). The degree of bedrock porosity (e.g., Gerbault et al., 2012) and permeability (e.g., Mittal & Richards, 2019), and the specific nature of the fluids are therefore important considerations for future failure analyses (e.g., Ruz‐Ginouves et al., 2021).…”

Section: Implications and Limitationsmentioning

confidence: 99%

“…Naturally, one of the greatest uncertainties when modeling reservoir failure lies in the knowledge of properties of the host rock surrounding the magmatic system (Zhan & Gregg, 2019). Recent laboratory studies have demonstrated that key physical parameters of volcanic rocks, such as Young's modulus and strength, are highly dependent on the porosity of the rock (Heap et al., 2020, 2021; Heap & Violay, 2021). Porous rocks at high confining pressures can undergo compaction, which may foster additional inelastic behavior.…”

Section: Implications and Limitationsmentioning

confidence: 99%

Rheological Controls on Magma Reservoir Failure in a Thermo‐Viscoelastic Crust

et al. 2022

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As volcanoes undergo unrest, understanding the conditions and timescales required for magma reservoir failure, and the links to geodetic observations, are critical when evaluating the potential for magma migration to the surface and eruption. Inferring the dynamics of a pressurized magmatic system from episodes of surface deformation is heavily reliant on the assumed crustal rheology, typically represented by an elastic medium. Here, we use Finite Element models to identify the rheological response to reservoir pressurization within a temperature‐dependent Standard Linear Solid viscoelastic (“thermo‐viscoelastic”) domain. We assess the mechanical stability of a deforming reservoir by evaluating the overpressures required to initiate brittle failure along the reservoir wall, and the sensitivity to key parameters. Reservoir inflation facilitates compression of the ductile wall rock, due to the non‐uniform crustal viscosity, impacting the temporal evolution of the induced tensile stress. Thermo‐viscoelasticity enables a deforming reservoir to sustain greater overpressures prior to failure, compared to elastic analyses. High‐temperature (e.g., mafic) reservoirs fail at lower overpressures compared to low‐temperature (e.g., felsic) reservoirs, producing smaller coincident displacements at the ground surface. The impact of thermo‐viscoelasticity on reservoir failure is significant across a wide range of overpressure loading rates. By resisting mechanical failure on the reservoir wall, thermo‐viscoelasticity impacts dyke nucleation and formation of shear fractures. Numerical models may need to incorporate additional processes that act to promote failure, such as regional stresses (e.g., topographic and tectonic), external triggers (e.g., earthquake stress drops), or pre‐existing weaknesses along the reservoir wall.

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The tensile strength of volcanic rocks: Experiments and models

Cited by 19 publications

References 123 publications

Alteration‐Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

Alteration‐Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

Earthquakes Indicated Stress Field Change During the 2006 Unrest of Augustine Volcano, Alaska

Rheological Controls on Magma Reservoir Failure in a Thermo‐Viscoelastic Crust

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