Numerical simulations of the propagation path and the arrest of fluid-filled fractures in the Earth

Dahm, Torsten

doi:10.1046/j.1365-246x.2000.00102.x

Cited by 150 publications

(176 citation statements)

References 43 publications

(57 reference statements)

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“…We simply assume that the dikes propagate orthogonal to σ3. Numerical models of dike propagation (Dahm, 2000;Maccaferri et al, 2011) and analog experiments (Watanabe et al, 2002) revealed that dike trajectories depend on the competition between dike overpressure and the external stresses (i.e., loading or unloading). High-overpressure dikes are expected to propagate straight, insensitive to spatial inhomogeneities of the stress field.…”

Section: Unloading Pressure Vs Dike Overpressure Control On the Erupmentioning

confidence: 99%

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Corbi

Rivalta

Pinel

et al. 2015

Earth and Planetary Science Letters

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Calderas are topographic depressions formed by the collapse of a partly drained magma reservoir. At volcanic edifices with calderas, eruptive fissures can circumscribe the outer caldera rim, be oriented radially and/or align with the regional tectonic stress field. Constraining the mechanisms that govern this spatial arrangement is fundamental to understand the dynamics of shallow magma storage and transport and evaluate volcanic hazard. Here we show with numerical models that the previously unappreciated unloading effect of caldera formation may contribute significantly to the stress budget of a volcano. We first test this hypothesis against the ideal case of Fernandina, Gal ‡pagos, where previous models only partly explained the peculiar pattern of circumferential and radial eruptive fissures and the geometry of the intrusions determined by inverting the deformation data. We show that by taking into account the decompression due to the caldera formation, the modeled edifice stress field is consistent with all the observations. We then develop a general model for the stress state at volcanic edifices with ! 1 calderas based on the competition of caldera decompression, magma buoyancy forces and tectonic stresses. These factors control: 1) the shallow accumulation of magma in stacked sills, consistently with observations; 2) the conditions for the development of circumferential and/or radial eruptive fissures, as observed on active volcanoes. This top-down control exerted by changes in the distribution of mass at the surface allows better understanding of how shallow magma is transferred at active calderas, contributing to forecasting the location and type of opening fissures.

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Section: Unloading Pressure Vs Dike Overpressure Control On the Erupmentioning

confidence: 99%

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Corbi

Rivalta

Pinel

et al. 2015

Earth and Planetary Science Letters

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“…[61] Geophysical observations [Battaglia et al, 2005], numerical [Dahm, 2000] and analog models [Rivalta and Dahm, 2005] indicate that dikes grow upward or laterally from the source region. Thus it is unlikely that the stress changes induced by the shallow dike would promote the injection of magma downward to the deeper dike.…”

Section: Eruption Modelmentioning

confidence: 99%

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

Wauthier¹,

Cayol²,

Kervyn³

et al. 2012

J. Geophys. Res.

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along a 20 km-long fracture network extending from the volcano to the city of Goma. The event was captured by InSAR data from the ERS-2 and RADARSAT-1 satellites. A combination of 3D numerical modeling and inversions is used to analyze these displacements. Using Akaike Information Criteria, we determine that a model with two subvertical dikes is the most likely explanation for the 2002 InSAR deformation signal. A first, shallow dike, 2 km high, is associated with the eruptive fissure, and a second, deeper dike, 6 km high and 40 km long, lies about 3 km below the city of Goma. As the deep dike extends laterally for 20 km beneath the gas-rich Lake Kivu, the interaction of magma and dissolved gas should be considered as a significant hazard for future eruptions. A likely scenario for the eruption is that the magma supply to a deep reservoir started ten months before the eruption, as indicated by LP events and tremor. Stress analysis indicates that the deep dike could have triggered the injection of magma from the lake and shallow reservoir into the eruptive dike. The deep dike induced the opening of the southern part of this shallow dike, to which it transmitted magma though a narrow dike. This model is consistent with the geochemical analysis, the lava rheology and the pre-and post-eruptive seismicity. We infer low overpressures (1-10 MPa) for the dikes. These values are consistent with lithostatic crustal stresses close to the dikes and low magma pressure. As a consequence, the dike direction is probably not controlled by stresses but rather by a reduced tensile strength, inherited from previous rift intrusions. The lithostatic stresses indicate that magmatic activity is intense enough to relax tensional stresses associated with the rift extension.

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“…Assuming a closed system, a dyke will tend to be emplaced such that it minimizes the total potential energy 15,16,17 , Θ T , equal to:…”

mentioning

confidence: 99%

Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland

Sigmundsson

Hooper

Hreinsdóttir

et al. 2014

Nature

466

577

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On 31 August a new eruption began from the same fissure and is still ongoing at the time of writing. After 4 September the movement associated with the dyke was minor, suggesting an approximate equilibrium between inflow of magma into the dyke and magma flowing out of it feeding the eruption. Minor eruptions may have occurred under Vatnajškull; shallow ice depressions marked by circular crevasses (ice cauldrons) were discovered in the period 27/08-07/09, indicating leakage of magma or magmatic heat to the glacier causing basal melting ( Fig. 1 and 2b). On 5 September, aircraft radar profiling showed that the ice surface in the centre of the B ‡r!arbunga caldera had subsided 16 m relative to the surroundings, resulting in a 0.32±0.08 km 3 subsidence bowl ( can be compared to a 1 day interferogram over the ice surface spanning 27 -28 August (Fig. 1), that has maximum line-of-sight (LOS) increase of 57 cm, indicating 55-70 cm of subsidence, during 24 hours. From 24 August to 6 September 16 M≥5 earthquakes occurred on the caldera boundary.Over 22000 earthquakes were automatically detected 16/08-06/09 2014, 5000 of which have been manually checked. Four thousand of these have been relatively relocated, defining the dyke segments. Ground deformation in areas outside the Vatnajškull ice cap, and on nunataks within the ice cap, is well mapped by a combination of InSAR, continuously recording GPS sites, and campaign GPS measurements. The GPS observations and analysis give the temporal evolution of the three-dimensional displacements used in the modelling (Fig. 1). Interferometric analysis of synthetic aperture radar images from the COSMO-SkyMed, RADARSAT-2 and TerraSAR-X satellites was used to form 11 interferograms showing LOS change spanning different time intervals (Supplementary Fig. 2). The analysis of seismic and geodetic data is described in Methods.Initial modelling of the dyke, with no a priori constraints on position, strike or dip, show the deformation data require the dyke to be approximately vertical and line up with the seismicity (Extended Data item 4). We therefore fixed the dip to be vertical and the lateral position of the dyke to coincide with the earthquake locations.We modelled the dyke as a series of rectangular patches and estimated the opening and slip on each patch ( Fig. 3a; see Supplementary Figures 3-4 for slip and standard deviations of opening). We used a Markov-chain Monte Carlo approach to estimate 7 the multivariate probability distribution for all model parameters (Methods) on each day 16/08-06/09 2014 (Fig. 2d). The results suggest that most of the magma injected into the dyke is shallower than the seismicity, which mostly spans the depth range from 5 to 8 km below sea level (see Fig. 2c and Methods). While magma may extend to depths greater than 9 km near the centre of the ice cap, towards the edge of the ice cap where constraints from InSAR and GPS are much better, significant opening is all shallower than 5 km (Fig. 3a). The total volume intruded into the dyke by 28 August was 0.48-0...

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Numerical simulations of the propagation path and the arrest of fluid-filled fractures in the Earth

Cited by 150 publications

References 43 publications

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland

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