DS0104 -

Volcano destabilizations: from observation to an integrated model of active deformation – SlideVOLC

Volcano destabilizations: from observation to an integrated model of active deformation

- Towards a better understanding of the flank destabilizations in volcanic areas. <br />- A multi-disciplinary and integrated study.

Towards a better understanding of the volcano destabilizations

Large-scale deformation and flank instabilities of volcanoes represent a significant hazard because they can lead to major edifice destabilizations and large landslides. In an island environment, flank collapse can also trigger tsunami with catastrophic impacts on the coastline. Basaltic volcanoes are amongst the largest volcanic edifices on Earth. On these huge active volcanoes, the continuous action of magmatic pressure leads to large deformation that ultimately control the volcano structure and topography with more or less mobile flanks, which respond to long-lasting stress field conditions (gravitational stress, magmatic processes and/or regional tectonics...). On La Réunion, a major destabilization of the Piton de la Fournaise flank occurring today would trigger tsunami with catastrophic impacts on the coastline population of the island and around the Indian Ocean. Indeed, 80% of the 840,000 inhabitants of La Réunion and most of the economic activities are located on the coastal fringe. It is thus of major interest for the scientific community to study and understand the large-scale deformation and flank instabilities of volcanoes and for society to educate the public on this hazard. <br />Our capability of predicting such catastrophic events relies on both our understanding of the complex link between the stress field, the volcanic and hydrothermal processes, and our ability to interpret the monitored signals as precursors. This project, focussed on Piton de la Fournaise volcano, aims to integrate new geophysical and geochemical observations into a coherent, global and realistic model. <br />We propose i) to bring new inputs to the models with the imaging, via multi-disciplinary innovative methods, of the extent of the volcano deformation, the main fracture networks, the hydrothermal system, and by constraining the true edifice rheology, and ii) to use this new information to model the deformation distribution over the volcano and the flank destabilization dynamics.

Our project is particularly innovative as it combines an unique dataset from multidisciplinary studies.
1) Imaging of the volcano:
1a) Ground deformation: jointly analysis of conventional DInSAR, PSInSAR, GNSS data and stereo-photogrammetry.
1b) 3D fracture mapping: visible and thermal infrared measurements and imagery via drone flights.
1c) Fluid circulations: deep and high resolution Electrical Resistivity Tomography
1d) Edifice rheology: laboratory analyses on rocks samples (physical properties - porosity, permeability, Vp/Vs measurements, uniaxial compression experiments - mineral analyses).
2) Numerical modelling: integration of these datasets into a global and realistic model.
This integration has not yet been done because of the only very recent evolution of volcano knowledge and monitoring networks at Piton de la Fournaise, and the need for new technologies to bring robust inputs to the models, as the ones just validated by our team in volcanic context: deep ERT to characterize the underlying deep structures and hydrothermal system, and Infra-Red imaging by drone flights for high resolution 3D fracture mapping.

The main deliverables of the project will be:
1) New imaging of the Piton de la Fournaise volcano (deformation, fracture networks, hydrothermal system extension, edifice rheology) at the scale of the whole edifice, via multidisciplinary innovative investigations.
2) The integration of these new data into realistic models to better understand and anticipated the volcano's flank instabilities.
3) For the general public and authorities: addition of an amendment to the current ORSEC plan for paroxysmal events, as volcano flank instabilities; update of the “Atlas des Risques Majeurs à La Réunion” (i.e. Atlas of major hazards at La Réunion; flood, storm, forest fire, tsunami….) from department; and dissemination for the general public.

The perspective is the production of a realistic “3D numerical volcano”, i.e. an integrated model of volcano edifice deformation using realistic rheology and hydro-mechanical coupling (with physical scenarios of the 3D thermal and deformation regime of the Piton de la Fournaise’s edifice), helping in the understanding and the monitoring of the volcano flanks stability and dynamics, and able to predict the time and scale evolution of edifice deformation during and between eruptive events.

The scientific impact of this project will benefit directly to the (1) volcanological observatory of Piton de la Fournaise (OVPF) but also the (2) volcanological community as a whole.
(1) The implementation of operational tools (PSInSAR) in compleme

Large-scale deformation and flank instabilities of volcanoes represent a significant hazard because they can lead to major edifice destabilizations and large landslides. In an island environment, flank collapse can also trigger tsunami with catastrophic impacts on the coastline population of proximal and distal locations. Basaltic volcanoes, like Etna (Italy), Hawaiian volcanoes (USA) and Piton de la Fournaise (La Réunion Island, France), are amongst the largest volcanic edifices on Earth. On these huge active volcanoes, the continuous action of magmatic pressure leads to large deformation areas that ultimately control the volcano structure and topography with more or less mobile flanks, which respond to long-lasting stress field conditions (gravitational stress, magmatic processes and/or regional tectonics...). On La Réunion, a major destabilization of the Piton de la Fournaise flank occurring today would trigger tsunami with catastrophic impacts on the coastline population of the island and around the Indian Ocean. Indeed, 80% of the 840,000 inhabitants of La Réunion and most of the economic activities are located on the coastal fringe. It is thus of major interest for the scientific community to study and understand the large-scale deformation and flank instabilities of volcanoes and for society to educate the public on this hazard that is currently disregarded on effusive basaltic volcanoes, especially on La Réunion where the volcano is known as a popular hike, especially during eruptive stages.
Our capability of predicting such catastrophic events relies on both our understanding of the complex link between the stress field, the volcanic and hydrothermal processes, and our ability to interpret the monitored signals as precursors. This project, focussed on Piton de la Fournaise volcano, aims to integrate new geophysical and geochemical observations into a coherent, global and realistic model.
We propose i) to bring new inputs to the models with the imaging, via multi-disciplinary innovative methods, of the extent of the volcano deformation, the main fracture networks, the hydrothermal system, and by constraining the true edifice rheology, and ii) to use this new information to model the deformation distribution over the volcano and the flank destabilization dynamics.
The final purpose is the production of a realistic “3D numerical volcano”, i.e. an integrated model of volcano edifice deformation using realistic rheology and hydro-mechanical coupling (with physical scenarios of the 3D thermal and deformation regimes of the Piton de la Fournaise’s edifice), aiding an understanding of the volcano flanks stability and dynamics, and able to predict the time and scale evolution of edifice deformation during and between eruptive events.
This project is particularly innovative as it combines the integration of new data from multidisciplinary studies into improved numerical modelling and produces a realistic numerical volcano.
The knowledge accumulated on Piton de la Fournaise will be exported to other volcanoes worldwide, notably Etna and Kilauea, which share common features with Piton de la Fournaise, most notably flank instabilities and huge landslides during their past activity. This project, which includes both observations and modelling, involves a research team that has all the skills and abilities required to conduct and carry out such a study. This frame ensures ideal conditions that can extend our research methods to similar volcanoes in Europe and worldwide.

Project coordinator

Madame Aline PELTIER (Institut de Physique du Globe de Paris)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IPGP Institut de Physique du Globe de Paris

Help of the ANR 285,937 euros
Beginning and duration of the scientific project: September 2016 - 36 Months

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