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Transferts de magma au volcan du Piton de la Fournaise déterminés par la modélisation 3D de données d'interférométrie radar entre 1998 et 2000

Abstract : After five and a half years of quiescence, Piton de la Fournaise volcano (Réunion Island, Indian Ocean) entered into a new active period in March 1998. Synthetic aperture radar interferometry (InSAR) data show complex displacements associated with the first five eruptions that occurred between 1998 and 2000. A method was developed to find realistic geometries and overpressures of dike intrusions from the InSAR data. This method is based on a combination of a fully 3D boundary element method and a Monte Carlo inversion. The noise characteristics of the data are taken into account in the inversions. Synthetic tests show that a model is successfully retrieved within predicted narrow confidence intervals. Neglecting topography was shown to result in poor modelling at depth and in overestimation of overpressure or opening. Application of the method to each eruption requires specific parameterizations of the model(s); in some cases, a curved dike surface must be introduced, and in other cases, simultaneous inversions for two dikes are required. Most of the estimated dikes dip seaward with a typical angle of 65 degrees. The dike associated with the first eruption of the cycle (March 1998) is found to originate from sea level (2600 m below the summit), whereas those dikes associated with subsequent eruptions are estimated to be shallower than about 1000 m below the ground. Laterally elongated dikes, preeruption deformations and seismic swarms can be explained by a level of neutral buoyancy less than 1000m beneath the ground. This is consistent with the presence of magma reservoirs at this level. For the studied period, the intruded volume amounts to 8% of the lava flow volume. The spatial periodicity of dike intrusions from the northern to the southern flank is consistent with stress transfer models. Finally, Coulomb stress analysis shows that the five eruptions modelled mostly encourage slip on potential subhorizontal planes located 1000–1500m above sea level.
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https://tel.archives-ouvertes.fr/tel-00011582
Contributor : Yo Fukushima <>
Submitted on : Friday, February 10, 2006 - 1:07:54 PM
Last modification on : Monday, October 19, 2020 - 11:09:29 AM
Long-term archiving on: : Monday, September 17, 2012 - 11:50:47 AM

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  • HAL Id : tel-00011582, version 1

Citation

Yo Fukushima. Transferts de magma au volcan du Piton de la Fournaise déterminés par la modélisation 3D de données d'interférométrie radar entre 1998 et 2000. Geophysics [physics.geo-ph]. Université Blaise Pascal - Clermont-Ferrand II, 2005. English. ⟨NNT : 2005CLF21633⟩. ⟨tel-00011582⟩

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