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Measurements of permeability at high-pressure and high-temperature are critical to model and understand the behaviour and evolution of geothermal systems. To perform such measurements and provide constraints on the permeability of crustal rocks, we designed and tested a new apparatus.Our high-pressure, high-temperature permeameter consists of three independent parts: the permeant gas circuit, the confining fluid circuit, and the heating element. For each measurement, a cylindrical sample is placed between the up- and downstream platens, into an annular Viton jacket which is secured within the pressure vessel. A confining pressure can be applied to the sample by filling the void space between the vessel and jacket through the inlet with kerosene. The confining pressure can be increased up to 50 MPa using a high-pressure hand pump. The temperature of the system can then be increased from room-temperature to up to 150 °C using a heating mantle wrapped around the pressure vessel and connected to a control box. After the confining pressure and temperature have been applied to the system, the permeability measurement is performed by flowing nitrogen (the permeant gas) through the sample while monitoring the pressure differential between the upstream pressure transducer and atmospheric pressure downstream of the sample at different volumetric flow rates (the steady-state method), measured using the downstream flowmeter.Using this new experimental apparatus, the permeability of Lanhélin granite (from France) samples were measured. Cylindrical samples were prepared and thermally stressed (heated to 700 °C) to ensure that their permeabilities lie in the range that can be measured in our set-up (> 10-18 m2). Permeability measurements were then performed under confining pressures of 2, 5, 10, 15, 20, 30, 40, and 50 MPa at room temperature, 50, and 100 °C. Our results provide the evolution of the permeability of microfractured granite in various pressure and temperature conditions, which will serve to inform numerical modelling designed to explore the influence of in-situ conditions on fluid flow within a fractured geothermal reservoir.

High-viscosity magma can form laccolith intrusions that deform and fracture the overburden, causing surface uplift and ground fracturing. Laccolith-induced deformation features have been described at well-exposed outcrops of long-solidified intrusions. The lack of recent geophysical data on rare laccolith emplacement events and the use of linearly elastic continuum-based numerical models precludes a clear understanding of the dynamic fracturing mechanisms. We present a new two-dimensional (2D) Discrete Element Method (DEM) approach to dynamic magma intrusion in a particle-based host medium. The model indicates highly discontinuous deformation and dynamic fracturing and visualizes the localization of subsurface strain. We calibrate the numerical rock strength parameters by performing numerical laboratory experiments to natural rock strength values. We systematically explored the effect of numerical parameters that govern host rock strength (bond cohesion, bond tensile strength, bond elastic modulus), and intrusion depth, on the spatial distribution of strain, stress, and fracturing. We find that high host rock stiffness results in widely distributed and dense fracturing associated with symmetrical dome-shaped surface uplift. Low host rock stiffness results in the concentration of central fracturing and narrow lateral shear bands and asymmetric evolution of the laccolith geometry and the surface deformation pattern. These patterns are affected by the intrusion depth. Our models help understand fracture distribution patterns above laccolith intrusions and open unprecedented opportunities for dynamically modelling intrusion-induced deformation in the upper few kilometers of the Earth’s crust.

Rock masses are often criss-crossed by generations of discontinuities, including veins, fractures, and joints. The presence of fractures and joints can increase rock mass permeability and decrease rock mass strength. However, fluid flow within rock masses can result in secondary mineral precipitation within these spaces. Secondary mineralisation can reduce permeability, with important consequences for fluid flow in systems that rely on discontinuity-dominated permeable networks. Here we investigate if variably sealed joints can be reactivated during deformation and the role joint reactivation plays on permeability. We deformed 20 mm in diameter by 40 mm long cores of un-jointed and jointed (variably sealed) bedded sandstones. Samples were cored such that their dominant structural feature (i.e., bedding or joint) was oriented parallel, perpendicular, or at approximately 30° to the sample axis. We find that the permeability of the undeformed samples is sensitive to the presence and orientation of bedding. In jointed samples, well-sealed joints can act as barriers to fluid flow, but partially filled joints neither inhibit nor promote fluid flow with respect to their joint-free counterparts. While all rocks in this study deformed in the brittle regime under triaxial deformation conditions, the location of the experimentally induced fractures depends on the extent to which joints are sealed. The mineralisation that fills well-sealed joints also permeates the surrounding sandstone matrix, locally reducing porosity and forming a cohesive bond between the joint-fill and the host-rock that increases rock strength: experimentally induced fractures do not exploit pre-existing joint surfaces in these samples. By contrast, strain is localised on the joint surface in samples containing partially sealed joints and the strength of these samples is lower than their un-jointed counterparts. The permeability of all samples increased after deformation, but permeability increase was largest in samples with pre-existing, poorly filled joints. We conclude that partially sealed joints act as planes of weakness within rock masses and that their reactivation can result in significant permeability increase. Well-sealed joints, however, may locally increase rock strength and never become reactivated during deformation: consequently, these joints may never re-contribute to the permeability of a rock mass. These observations provide insight into how fluid flow in the crust may evolve, with possible implications for how these systems weather over time.

The rocks forming a volcano are typically saturated or partially-saturated with liquid. However, most experiments aimed at better understanding the mechanical behaviour of volcanic rocks have been performed on dry samples, and therefore most large-scale models designed to explore volcanic stability have used parameters representative for dry rock. We present a combined laboratory and modelling study in which we (1) quantify the influence of water on the mechanical behaviour of variably altered dome rocks from La Soufrière de Guadeloupe (Eastern Caribbean) and (2) use these new laboratory data to investigate the influence of water on dome stability. Our laboratory data show that the ratio of wet to dry uniaxial compressive strength (UCS) and Young's modulus are ~0.95–0.30 and ~1.00–0.10, respectively. In other words, the rocks were all weaker when saturated with water. We also find that the ratio of wet to dry UCS decreases with increasing alteration (the wt% of secondary minerals). Micromechanical modelling suggests that the observed water-weakening is the result of a decrease in fracture toughness (KIC) in the presence of water. We also find that the ratio of wet to dry KIC decreases with increasing alteration, explaining why water-weakening increases with alteration. To explore the influence of water saturation on dome stability, we numerically generated lava domes using the experimental data corresponding to dry unaltered and altered rock, in Particle Flow Code. The strength of the dome-forming rocks was then reduced to values corresponding to wet conditions. Our modelling showed that, although the stability of the unaltered dome was not influenced by water saturation, large displacements were observed for the altered dome. Additional modelling in which we modelled a buried alteration zone within an unaltered dome showed that higher displacements were observed when the dome was water saturated. We conclude that (1) the presence of water reduces the UCS and Young's modulus of volcanic rock, (2) larger decreases in UCS in the presence of water are observed for altered rocks, and (3) large-scale dome stability modelling suggests that the stability of a dome can be compromised by the presence of water if the dome is altered or contains an altered zone. These conclusions highlight that the degree of alteration and water saturation should be monitored at active volcanoes worldwide, and that large-scale models should use values for water-saturated rocks when appropriate.

The growing structure of active volcanoes due to material addition can lead to oversteepening and overloading (McGuire, 2003). This situation can be worsened by seismic activity as most volcanoes are in seismically active areas. Moreover, the materials forming volcanic edifices are subjected to extreme conditions in terms of temperature, pore pressure (consequence of several combined factors) and chemically aggressive fluids (very low pH for example) which can all destabilize volcanoes’ flanks. Among these factors, hydrothermal activity is of particular interest as it enhances rock dissolution (and thus, increases rock porosity), promotes high pore pressures and leads to the creation of mechanically weaker materials (like clay-rich rocks) and promote the instability (Rattez and Veveakis, 2020). However, the effects that these processes have on volcano stability have been barely quantified (Heap and Violay, 2021).To better understand the influence of different types of hydrothermal alteration on the hydraulic and mechanical properties of volcanic rocks, permeameter and triaxial experiments have been performed on samples retrieved by Detienne et al. (2016) from the Tutupaca volcano (17° 01′ S, 70° 21′ W). This volcano is a dacitic dome complex located at the southern end of the Peruvian arc. The study focuses on a remarkably well-preserved debris avalanche deposit emplaced to the northeast of the volcano. The debris avalanche is sourced to Eastern Tutupaca; it left a horseshoe-shaped crater open to the northeast and was accompanied by a pyroclastic flow (volume: 6.5-7.5 x 107 m3) (Samaniego et al., 2015). The mineralogy and the microstructure of the samples have been investigated using X-ray diffraction and micro-computed tomography respectively. Preliminary results exhibit a high variability of mineralogy, microstructures, and mechanical properties. It appears that the alteration degree may have more influence on the mechanical behavior of volcanic rocks than the porosity. This dataset could be further used in numerical models of flank collapses to better constrain the role of hydrothermal alteration on the nucleation of those events. ReferencesDetienne M. (2016) “Unravelling the role of hydrothermal alteration in volcanic flank and sector collapses using combined mineralogical, experimental, and numerical modelling studies”. PhD thesis, UCLouvain.Heap M. and Violay M. (2021) “The mechanical behaviour and failure modes of volcanic rocks: a review”, Bulletin of Volcanology, 83:33. Lipman PW, Mullineaux DR (eds) (1981) “The 1980 eruptions of Mount St Helens, Washington.” U.S. Geological Survey, Professional Paper 1250, 844 pp.McGuire WJ (2003) Volcano instability and lateral collapse. Revista 1:33–45.Rattez H, Veveakis M (2020). “Weak phases production and heat generation control fault friction during seismic slip”, Nature Communications, doi: 10.31223/osf.io/xupr8 Samaniego, P., Valderrama, P., Mariño, J., De Vries, B. V. W., Roche, O., Manrique, N., Chédeville, C., Liorzou, C., Fidel, L. & Malnati, J. (2015). “The historical (218±14 aBP) explosive eruption of Tutupaca volcano (Southern Peru) ». Bulletin of Volcanology, 77, 1-18.

Volcano slope stability analysis is a critical component of volcanic hazard assessments and monitoring. However, traditional methods for assessing rock strength require physical samples of rock which may be difficult to obtain or characterize in bulk. Here, visible to shortwave infrared (350-2500 nm; VNIR-SWIR) reflected light spectroscopy on laboratory-tested rock samples from Ruapehu, Ohakuri, Whakaari, and Banks Peninsula (New Zealand), Merapi (Indonesia), Chaos Crags (USA), Styrian Basin (Austria) and La Soufriere de Guadeloupe (Eastern Caribbean) volcanoes was used to design a novel rapid chemometric-based method to estimate uniaxial compressive strength (UCS) and porosity. Our Partial Least Squares Regression models return moderate accuracies for both UCS and porosity, with R2 of 0.43-0.49 and Mean Absolute Percentage Error (MAPE) of 0.2-0.4. When laboratory-measured porosity is included with spectral data, UCS prediction reaches an R2 of 0.82 and MAPE of 0.11. Our models highlight that the observed changes in the UCS are coupled with subtle mineralogical changes due to hydrothermal alteration at wavelengths of 360-438, 532-597, 1405-1455, 2179-2272, 2332-2386, and 2460-2490 nm. These mineralogical changes include mineral replacement, precipitation hydrothermal alteration processes which impact the strength of volcanic rocks, such as mineral replacement, precipitation, and/or silicification. Our approach highlights that spectroscopy can provide a first order assessment of rock strength and/or porosity or be used to complement laboratory porosity-based predictive models. VNIR-SWIR spectroscopy therefore provides an accurate non-destructive way of assessing rock strength and alteration mineralogy, even from remote sensing platforms. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Surface deformation patterns on terrestrial planetary bodies have been interpreted as magma emplacement features due to their similarity with Earth analogues or their association with inferred eruptive products. Dome-shaped surface uplift features were recognized for example at floor-fractured impact craters on the Moon (Jozwiak et al., 2012), and at the Tharsis volcanic province on Mars (Farrand et al., 2011). The lack of subsurface geophysical data however precludes a clear observation of the characteristics and emplacement mechanisms of the inferred underlying magma intrusions. On Earth, our insight into the characteristics of the magmatic plumbing systems that underly surface doming also remains cryptic due to the sparsity of observations. The most recent event was the hybrid explosive-effusive eruption at Cordón Caulle, Chile, in 2011. Pre- and syn-eruptive surface doming and pervasive ground fracturing observed there using satellite radar interferometry was interpreted there to result from the intrusion of a rhyolitic laccolith (Castro et al., 2016). Analytical and numerical models can use such geodetic observations to help estimate intrusion characteristics and assist in forecasting potential volcanic eruptions. The same models are used to infer shallow magma intrusion characteristics on terrestrial planetary bodies where the only observations available are surface topography and shallow ground-penetrating radar data. Existing models generally assume that planetary crusts deform linearly-elastic, which leads to a simplification of the magmatic source geometry and the related displacement and stress fields. On Earth, however, host rocks around exposed solidified and exposed dykes, sills and laccoliths often show indicators of non-elastic deformation. Strain can accumulate along large-scale discontinuities in the overburden rocks, making the investigation of the emplacement mechanisms by traditional continuum models difficult. To provide a more geologically realistic means of estimating magma intrusion characteristics and investigate the associated emplacement mechanisms, we have developed a numerical discontinuum model of laccolith emplacement within the framework of the “DeMo-Planet” project. We use the two-dimensional (2D) Discrete Element Method (DEM) model PFC2D (Itasca Consulting Group, Inc.) to represent the modelled medium as a particle-based network. We can use this model to indicate fracturing and highly discontinuous deformation, as well as visualizing the localization of subsurface strain and corresponding deformation. Two stages of the model application are now available. In a first stage, a laccolith-shaped pressure source is inflated at the base of the host medium with varied depth of the magmatic source. In a second stage, particles are injected into the laccolith-shaped fluid body to simulate constant magma supply into a growing intrusion. In this presentation, we will simulate laboratory tests to calibrate the mechanical behaviour and the relations between particle contact parameters of the numerical host rock and magma. To that end, we use the elastic property values (Young modulus) and tensile strength measured on host rocks estimated for the Moon and Mars (Heap et al., 2020). We then use elastic properties measured using uni-axial laboratory tests. The investigated rock samples were collected from exposed Permian sediments above Permian trachyandesite intrusions of the Intra-Sudetic Synclinorium in Poland. The calibration of the model with geological data then allows a comparison of the numerical results with field observations of the structural deformation in the intrusions’ overburden. In the future, we plan to analyze the effect of varying gravity, geometric and mechanical model parameters on the ratio of tensile to shear-mode fracturing, as well as investigating the magma-induced surface displacement in detail. DeMo-Planet demonstrates a promising multidisciplinary approach of informing numerical models of complex, discontinuous magma emplacement processes in the heterogeneous and fractured shallow crust of terrestrial planetary bodies. The validation of this new modelling application with detailed structural information from representative Earth analogue sites will allow us to investigate the characteristics of the cryptic magma bodies underlying surface doming on the Moon and Mars. The application of our model to other terrestrial planetary bodies will simultaneously improve the interpretation of volcanic unrest signals on Earth. References Castro, J.M. et al. (2016) “Rapid laccolith intrusion driven by explosive volcanic eruption,” Nature Communications, 7, p. 13585. doi:10.1038/ncomms13585. Farrand, W.H. et al. (2011) “Spectral evidence of volcanic cryptodomes on the northern plains of Mars,” Icarus, 211(1), pp. 139–156. doi:10.1016/j.icarus.2010.09.006. Heap, M.J. et al. (2020) “Towards more realistic values of elastic moduli for volcano modelling,” Journal of Volcanology and Geothermal Research, 390, p. 106684. doi:10.1016/j.jvolgeores.2019.106684. Jozwiak, L.M. et al. (2012) “Lunar floor-fractured craters: Classification, distribution, origin and implications for magmatism and shallow crustal structure,” Journal of Geophysical Research E: Planets, 117(11), pp. 1–23. doi:10.1029/2012JE004134.

Magma ascent pathways open when pressurised gas-ash mixtures overcome the strength of the surrounding rock to form fractures. Gas-ash mixtures are injected into the propagating fractures, and if ash is deposited this early stage of dyke or conduit evolution is preserved as a tuffisite vein. Once a conduit has become established, fractures formed in the country rock adjacent to the volcanic conduit are also injected with gas-ash mixtures to form tuffisites. If tuffisites allow for the significant escape of magmatic gases from the main conduit zone, tuffisites might dissipate sufficient pressure to moderate eruption style from explosive to effusive. The hot particles within the tuffisite, however, sinter together through time, reducing tuffisite permeability until gas no longer flows. Despite their potentially important role in controlling eruption dynamics, the length of time that a tuffisite may remain permeable and the flux of gas that tuffisites can allow to escape are poorly constrained.The dimensions of tuffisites vary, but fractures are typically tens of centimetres to tens of metres in length. The internal structure of tuffisites can be complex, often consisting of multiple units of pyroclastic material, varying from massive lithic breccias to stratified tuffs. Erosion and deposition, due to the repeated injection of ash-laden fluid, produces a variety of sedimentary structures, from cross-lamination and graded bedding to soft-sediment deformation and internal injections. These structures record how the velocity and particle volume fraction of the injected fluid fluctuated through time, controlled by the fluid pressure gradient along the fracture. Tuffisites can therefore be interpreted as a fossil record of the fluid pressure fluctuations occurring during the opening of magmatic pathways.We aim to quantify and reconstruct the fluid overpressure at different stages of tuffisite evolution. A large sub-horizontal tuffisite (0.9 m wide, >40 m long) formed at 500 m depth at the dissected rhyolitic Húsafell volcano, Iceland, has been used to constrain the pressures of tuffisite formation1. The pressure required to open fractures within the Húsafell tuffisite host rocks (basalt, friable ignimbrite, densely welded ignimbrite) has been constrained experimentally by injecting samples with pressurised water. The dimensions of different units within the Húsafell tuffisite suggest overpressures of 1.9-3.3 MPa would be needed for the emplacement of the largest units seen (0.1 cm thick and 40 m long), using a simple fracture opening model1.Sintering of hot particles within the tuffisite fill reduces tuffisite permeability through time, hindering outgassing. The porosity, permeability, and particle sizes of different units within the Húsafell tuffisite allow us to constrain the possible gas flux carried by tuffisite and how this would have evolved through time. By combining constraints on the fluid pressure, permeability, and sintering timescales of the Húsafell tuffisite we aim to gain insight into the processes controlling tuffisite formation, and whether tuffisites might permit sufficient outgassing to moderate eruption explosivity.1. Unwin et al. (2021) doi:10.3389/feart.2021.668058

With increasing depth, the rheology of rocks gradually transitions from brittle (localized, fractures) to ductile (homogeneous flow). Recently, it was demonstrated that, in the crust, the transitional zone might extend to shallower depth than previously thought (2km) with a zone where the deformation regime can be both localized and ductile (the LDT). In this regime, both extremely localized (fault slip) and distributed (cataclastic flow and/or plasticity) deformation may occur concurrently. This observation had great importance since the ductile regime is commonly thought to be aseismic and to mark the maximum depth of earthquake nucleation.However, this observation was made experimentally in non-porous rocks; porous rocks on the other hand display an additional characteristic in that their ductile behaviour may consist in the formation of compactions bands which greatly impact the behaviour of porous reservoirs and systems (e.g., volcanoes). Moreover, ductile rocks are commonly believed to be aseismic, the potential coexistence of both ductile and localized regimes in reservoir rocks might therefore have great implications for induced seismicity mitigation.Here, we present three conventional triaxial experiments on Volvic basalt (homogeneous, istropic, fine grain). We deformed cylindrical cores equipped with strain gages at 5MPa and room temperature until a sample-scale fracture nucleated and propagated. Subsequently, we increased confining pressure step wise, loading the sample every step until 0.2% irrecoverable strain was accumulated in the sample. In between confinement steps, the differential stress was unloaded. A pair of Linear Variable Differential Transformers (LVDTs) was used along with the strain gauges to accurately monitor the deformation behaviour of the samples.We show that Volvic basalt transitions from being purely localized to being purely ductile over a rather narrow pressure range from 40 to 80 MPa. The transition initiates when the frictional strength of the fault equates the yield strength of the bulk and terminates when it becomes greater than the maximum strength of the bulk. In this pressure range, deformation is initially accommodated in the bulk (most likely by compaction bands) until strain hardening eventually leads to fault reactivation. Once both fault sliding and bulk flow are active, the partitioning of strain between the two can be described by the same empirical ratio as that already established for non-porous rocks, i.e. (σf - σy)/ (σflow - σy).We conducted a second experiment at a faster strain rate (10-4 s-1) and show that faster deformation promotes brittle behaviour which pushes the LDT to greater confinement (i.e., greater depth).Additionally, we conducted a similar experiment in the presence of water. In this case, the LDT occurs at lower confinement, showing that, fluids, by promoting ductile processes such as stress-corrosion, bring the LDT to shallower depth.Our results are crucial for the understanding of reservoirs where ductile deformation (compaction bands) and induced earthquake mitigation have to be finely tuned.

Volcanoes are subject to intense fluid circulation, altering primary rock properties. The rock alteration can be due to “cold” water-driven weathering or “hot” hydrothermal fluids. Such alteration is facilitated by the efficient circulation of fluids through fractures and the connected pore-network. Fluid-driven alteration can manifest as mineral dissolution and precipitation, ultimately changing the properties of the host rock, such as strength and elasticity. Alteration-induced geomechanical changes are complex due to the large range of protolith porosity (e.g. 0.01-0.8) and permeability (e.g. 10-10 to ≤10-18 m2). For example, fresh pyroclastic rocks can initially have low strength, which can be ‘reinforced’ by mineral precipitation. In contrast, dense lava rocks can decrease their strength due to pore space enlargement and development of secondary clays, oxides, sulfides and sulfates.This study analysed lab-tested samples from Ruapehu, Merapi, Whakaari, Chaos Crags, Ohakuri, Styrian Basin and La Soufrière de Guadeloupe volcanoes to provide new insights into the controls on geomechanical properties due to weathering and hydrothermal alteration. The volcaniclastic and lava rocks range from basaltic to rhyolitic in composition and encompass surface weathering and intermediate and advanced argillic alteration styles. The physical, geomechanical, Visible-Near Infrared (VNIR; 350-1000 nm), and Shortwave Infrared (SWIR; 1000-2500 nm) properties of the rocks were measured on core samples. Porosity, P-wave velocity, and uniaxial compressive strength ranged from 0.02-0.67, 88-5800 m/s, and 0.1-312 MPa, respectively. Partial Least Squares Regression (PLSR) was employed to successfully predict physical and mechanical properties using VNIR-SWIR spectroscopy data. The PLSR-based prediction models highlighted a handful of spectral bands around 400-600 nm, 1400 nm and 2200-2300 nm, indicating that hydrated secondary minerals were responsible for the observed geomechanical changes. The proposed method using VNIR-SWIR spectroscopy can lead to a new way of mapping physical and geomechanical properties at outcrop-scale using field spectrometers, and at volcano-scale using airborne and satellite remote sensing.

The tensile strength of volcanic rock exerts control over several key volcanic processes, including fragmentation, magma chamber rupture, and dyke propagation. However, and despite this importance, values of tensile strength for volcanic rocks are relatively rare. It is also unclear how their tensile strength is modified by rock physical properties such as porosity, pore size, and pore shape and ongoing processes such as hydrothermal alteration. We present here the results of systematic laboratory and numerical experiments designed to better understand the influence of porosity, microstructural parameters (pore size, shape, and orientation), and hydrothermal alteration on the tensile strength of volcanic rocks. Our data show that tensile strength is reduced by up to an order of magnitude as porosity is increased from 0.01 to above 0.3, highlighting that porosity exerts a first-order control on the tensile strength of volcanic rocks. Our data also show that pore diameter, pore aspect ratio, and pore orientation can also influence tensile strength. Finally, our data show that hydrothermal alteration can decrease tensile strength if associated with mineral dissolution and weak secondary minerals, or increase tensile strength if associated with pore- and crack-filling mineral precipitation. We present a series of theoretical and semi-empirical constitutive models that can be used to estimate the tensile strength of volcanic rocks as a function of porosity or alteration intensity. To outline the implications of our data, we show how tensile strength estimations can influence predictions of magma overpressures and assessments of the volume and radius of a magma chamber, and we explore the influence of alteration using discrete element method modelling in which we model the amount and distribution of damage within variably-altered host-rock surrounding a pressurised dyke. It is our hope that the experiments, models, and understanding provided by our study prove useful for modellers that require the tensile strength of volcanic rocks for their models.

The characterization of volcanic hydrothermal systems (VHS) is fundamental for the early detection of precursors to phreatic or magmatic eruptions and for understanding hazards related to slope instabilities. Since these phenomena can be related to pore-fluid dynamics within the volcanic edifice, monitoring the spatial distribution of the different fluid phases (water, air, vapor) is of great importance. Ambient noise seismic interferometry has been employed for this task, correlating temporal changes in seismic velocities with variations in the water table depth in volcanic areas. However, this technique usually considers that above this depth, the pore space within the rock is totally occupied by a gaseous phase. This, in turn, implies that the body wave velocities and the density of the unsaturated zone are constant values, which is expected to impact on the determination of the water table depth. In this work, we assess the influence of partial saturation in the unsaturated zone of a VHS on ambient seismic noise, by employing a comprehensive rock physics model based on a saturation profile given by the Van Genuchten model. We focus on the sensitivity of Rayleigh waves, which are usually considered to be the most important contribution to the ambient seismic noise. We consider an altered andesite layer overlying a half-space consisting of a relatively unaltered andesite representing the volcanic basement, which is representative of the VHS of La Soufrière de Guadeloupe volcano (Eastern Caribbean, France). We base our rock physics model on Gassmann’s equations to compute body wave velocities as a function of fluid saturation. We compute Rayleigh wave phase velocities for different positions of the water table and analyze their relative difference with respect to a reference scenario that corresponds to the mean value of the water table depth in this region. Our results suggest that the existence of a partial water saturation distribution could affect the Rayleigh wave velocities, and that this effect depends on the range of frequencies considered and the degree of hydrothermal alteration of the medium. For highly altered andesite, characterized by a higher porosity and a lower rock-mass stiffness, the relative variation in velocity obtained with a partial saturation distribution can be up to twice or down to half of the variation for the scenario corresponding to a constant saturation, depending on the frequency range considered. The depth sensitivity kernels of the Rayleigh wave phase velocities exhibit significant variations within regions with variable water content for frequencies between 4 and 6 Hz, which indicates that these seismic waves are able to distinguish the presence of a partial saturation distribution. These results indicate that relative velocity differences derived from ambient noise interferometry provide the possibility of inferring spatial distributions of water content and, therefore, density variations within VHS. This technique therefore emerges as a useful tool to inform on volcanic hazards related to hydrothermal activity, such as erratic explosions and partial flank collapses.

Lava dome collapse hazards are intimately linked with their morphology and internal structure. We present new lava dome emplacement models that use calibrated rock strengths and allow material behaviour to be simulated for three distinct units: (1) a ductile, fluid core; (2) a solid upper carapace; and (3) disaggregated talus slopes. We first show that relative proportions of solid and disaggregated rock depend on rock strength, and that disaggregated talus piles can act as an unstable substrate and cause collapse, even in domes with a high rock strength. We then simulate sequential dome emplacement, demonstrating that renewed growth can destabilise otherwise stable pre-existing domes. This destabilisation is exacerbated if the pre-existing dome has been weakened following emplacement, e.g., through processes of hydrothermal alteration. Finally, we simulate dome growth within a crater and show how weakening of crater walls can engender sector collapse. A better understanding of dome growth and collapse is an important component of hazard mitigation at dome-forming volcanoes worldwide.

Sample location maps and photographs, sample photographs, thin section images, mineral componentry of the samples, additional methods, selected laboratory data, more details on the upscaling and model, and additional models.

International audience; The Pontgibaud Crustal Fault Zone (CFZ) in the French Massif Central provides an opportunity to evaluate the high-temperature geothermal potential of these naturally permeable zones. Previous 2D modeling of heat and mass transfer in a fault zone highlighted that a subvertical CFZ concentrates the highest temperature anomalies at shallow depths. By comparing the results of these large-scale 2D numerical models with field data, the depth of the 150°C isotherm was estimated to be at a depth of 2.5 km. However, these results did not consider 3D effects and interactions between fluids, deformation and temperature. A combined multidisciplinary approach makes it possible to better constrain the variation of permeability in 3D. This variation is then integrated into 3D numerical modeling. Based on a thermo-poroelastic assumption, a preliminary 3D THM numerical model is presented. A first parametric study highlights the role of permeability, stress direction and stress intensity on fluid flow. In particular, three different convective patterns have been identified: finger-like, blob-like and double-like convective patterns. Finally, a large-scale 3D numerical model of the Pontgibaud CFZ, based on THM coupling and the comparison with field data (temperature, heat flux, electrical resistivity), allows us to observe the convective pattern at the origin of the rise of the 150°C isotherm to economically exploitable depths. This result is obtained for values of permeability, intensity and direction of stresses comparable to the parametric study. Although simplified hypotheses have been used, 3D field data have been reproduced. Finally, we tried to understand the observed effects of poroelasticity on fluid flow.

International audience; Numerous recent studies indicate that crustal-scale fault zones represent efficient conduits for meteoric fluids to flow down to mid-crustal depths (Haines et al., 2016). The present study aims to understand the potential of a new and novel type of geothermal system for high temperature and electricity production: Crustal Fault Zones (CFZ). One such example is the Pontgibaud fault zone (French Massif Central), a 30 km-long and 3 km-wide mineralized fault zone. The Pontgibaud fault zone is also characterized by numerous CO2-rich-thermo-mineral springs. Moreover, this area is also defined by local and regional surface heat flow values of 110 mW/m 2 (International Heat Flow Commission database) involving temperature gradients between 37 and 41 °C/km. The Pontgibaud fault zone has been well studied in the last few years (Bellanger et al., 2017), electrical conductivity anomalies have been identified (Ars et al., 2019) and the temperature anomaly has been estimated (Duwiquet et al., 2019). Estimation of the geothermal resource have been established by 2D geological numerical modelling, with Thermal-Hydraulic (TH) coupling. Here we propose to integrate structural field observation into 3D geological numerical modelling with Thermal-Hydraulic-(Mechanical) (TH(M)) coupling. We then evaluate the various applications for high-temperature geothermal exploitation.

One of the most persistent beliefs about hypnosis is its ability to transcend mnemonic abilities. This belief has paved the way to the use of hypnosis in the clinical and legal arenas. The authors review the phenomena of hypnotic hypermnesia, pseudo-memories, and amnesia in light of current knowledge of hypnosis and memory. The investigation of the relation between hypnosis and memory processes has played an important role in our understanding of memory in action. Hypnosis provides a fertile field to explore the social, neuropsychological, and cognitive variables at play when individuals are asked to remember or to forget their past. We suggest promising avenues of research that may further our knowledge of the building blocks of memories and the mechanisms that leads to forgetfulness.

Catheter-related blood stream infections may be reduced by interdialytic locking with Taurolidine, a nontoxic antimicrobial agent. A formulation of 1.35% Taurolidine in 4% citrate (TC) is associated with a greater need for thrombolysis to maintain catheter patency than 5000 U/ml heparin. Our aim was to determine whether addition of 500 Units/ml of heparin to TC reduces the need for thrombolysis. TCH (1.35% taurolidine, 4% citrate and 500 U/ml heparin) was compared to TC and Heparin 5000 U/ml using retrospective data. Hundred and six adult hemodialysis patients with internal jugular tunnelled intravascular catheters using TCH were compared with 34 patients using TC and 34 patients using heparin 5000 U/ml respectively. Outcomes were time to first use of thrombolysis and bacteremia rates.TCH reduced the need for thrombolysis compared to TC (hazard ratio, 0.2; 95%CI: 0.06, 0.5; p < 0.001) and was not significantly different from heparin 5000 U/ml (hazard ratio, 1.4; 95%CI: 0.5, 3.9; p = 0.5). The bacteremia rates from all causes were 1.33, 1.22 and 3.25 per 1000 catheter- days (p < 0.001) in the TCH, TC and heparin groups respectively. Addition of 500 U/ml heparin to TC reduces the need for thrombolysis without increasing bacteremia and may achieve patency comparable to heparin 5000 U/ml.

There are modules for all of the common system administration tasks available in Ansible. There are currently 495 modules shipped with Ansible, which is a huge increase over the 141 modules that shipped with it in October 2013. Writing your own modules can be a great way to add custom functionality to Ansible so that you can integrate with your internal systems using the same, user friendly syntax that Ansible provides.

Depending on which operating system you use, there are various ways to install Ansible. On Linux, you can either install Ansible from source or build a packaged version of Ansible that you install with your system’s package manager.

In Chapter 1, you put together a simple playbook and ran it against your Vagrant machine using the vagrant provision command. You can run that same playbook against any machine that also has a running SSH server by using the ansible-playbook command. First, however, you need an inventory file. In this chapter, we’ll take a look at what an inventory file is, how to run ansible-playbook without Vagrant, and how to leverage the inventory file when you have a complex inventory of machines with which you need to interact.