Program 2 Internal structure and deformation of volcanic edifices

Program Participating laboratories :  LMV (Laboratoire Magmas et Volcans)  LPC (Laboratoire de Physique Corpusculaire)  LIMOS (Laboratoire Informatique, Modélisation et Optimisation des Systèmes)  LM (Laboratoire de Mathématiques)

Background and objective of the program  Volcanic crises (eruptions, volcano-tectonic events, fluids emergence, …) are the last stage of a chain of processes occurring in the Mantle and the Crust.  In this program, we focus on the static and dynamic internal structure of volcanoes (other aspects are studied by other ClerVolc programs)  This research involves both the application of established methods and the development of new equipments and methods

For example, geophysical methods provide insights in the internal structure and dynamics of volcanoes, but with various spatial and time resolution, and … Background and objective of the program

To understand how volcanoes work, we have to translate geophysical images into geological images. The quality of the latter strongly depends on the accuracy of geophysical data and models Background and objective of the program

Or, the measurement of the surface displacements before, during and after a volcanic crisis carries information on underground magma or hydrothermal fluids movements or on volcano-tectonic (slide, collapse, …) phenomena, but … Background and objective of the program

but … the understanding of the source(s) depends on more or less sophisticated approaches Background and objective of the program

 In order to better understand the internal processes of volcanoes and to anticipate their short and long term behaviours, we need to: - To improve the methods that allows us quantify the static and dynamic structure of volcanoes - To develop new methods for this purpose - To better characterize eruption and volcano-tectonic event precursor signals at volcanoes in state of unrest Background and objective of the program

Anticipated program Static imagery of the interior of volcanoes: - Established geophysical methods: gravity, resistivity, magnetism, seismic tomography, ground penetrating radar - New method: muon imagery Dynamic imagery of the interior of volcanoes: - Deformation measurement and modeling - Seismic studies - Dynamic muon imagery

Muon imagery Short term  Development of the equipment and of the processing of the data  2D and 3D images  Validation of the method by comparison with other geophysical results  test site : Puy de Dôme Long term  Development of a portable, autonomous, remotely controlled muon station  Study of the static and dynamic structure of active volcanoes (expected first site : Stromboli)  Sharing of the new method with the scientific community

Muon imagery Short term  Development of the equipment and of the processing of the data Col de Ceyssat Grotte Taillerie 867 m 2 km 107 deg 1074 m 1.2 km

Medium and long term  Development of a portable, autonomous, remotely controlled muon station Muon imagery

Deformation measurements and modeling Surface displacement measurements by radar interferometry   PITRE (Processeur InSAR Temps Réel Évolutif) - - Towards the near real-time processing of a high flux of data - - Ability to react in near real-time during crises - - Increase the reliability and accuracy of the measurements   CASOAR 2.0. Web interface for the production and consultation of InSAR data online

Deformation measurements and modeling Modeling surface displacements   Improvement and development of numerical models Mixed boundary element method combined with Monte Carlo inversion and linear inversion - - Improve computation of direct model - - Parallelization of the Monte Carlo type inversions - - Use of Green functions to take into account the topography and the heterogeneities - - High speed resolution of large matrices - - Input of source constrains (sign, value)   Publish collaborative and evolving programs that can also be used by non-experts

Seismic approaches   Data from observatories and temporary networks   Techniques : precise location of events, classification, identification of multiplets, coda interferometry, tomography, wave modeling. Internal structure, plumbing system and correlation of signals with activity

Intitiatives in Muon imagery  Acquisition of muon imagery of the Puy de Dôme from two different angle  Improvement in the precise positioning of the muon telescope  Start of a Clervolc PhD (LPC-LIMOS) on the 3D reconstruction from muon imagery  Preliminary works on: portable muon station (Clervolc engineer expected in 2013) and on the development of “intelligent” sensor networks

Intitiatives in INSAR-deformation modeling  Elaboration of a technique for the characterization of lava flows (thickness, volume, cooling) using Insar data  Tests (in 2D) of the applicability of the fictive frontiers approach to simulate fracturing in elastic medium, in order to develop later fast inversions of surface displacements in an heterogeneous medium  Start of parallelization of the existing codes (completion requires full-time engineer) Seismology  Participation to the multidisciplinary experience at Stromboli volcano (Theme 1) Geophysics  Geophysical study of the muon test site of the Puy de Dôme (gravity, resistivity) -> high resolution seismic tomography planned in 2013 (Clervolc PhD)  Study of the fastest growing resurgent dome on Earth (Yenkahe, Vanuatu)  origin, mechanism and dynamics of the resurgence in calderas

Conclusion Program 2 Internal structure and deformation of volcanic edifices ↓ Effective and productive collaboration between the different participating laboratories