seismic velocity imaging and monitoring of volcanic areas using ambient seismic noise

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Seismic velocity imaging and monitoring of volcanic areas using ambient seismic noise F. Brenguier (OVPF/IPGP), D. Clarke (IPGP), N. M. Shapiro (IPGP), M. Campillo (LGIT), E. Larose (LGIT) Laboratoire de Géophysique Interne et Tectonophysique (Grenoble) Institut de Physique du Globe de Paris/ Observatoire Volcanologique du Piton de la Fournaise

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Seismic velocity imaging and monitoring of volcanic areas using ambient seismic noise. F. Brenguier (OVPF/IPGP), D. Clarke (IPGP), N. M. Shapiro (IPGP), M. Campillo (LGIT), E. Larose (LGIT). Institut de Physique du Globe de Paris/ Observatoire Volcanologique du Piton de la Fournaise. - PowerPoint PPT Presentation

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  • Seismic velocity imaging and monitoring of volcanic areas using ambient seismic noiseF. Brenguier (OVPF/IPGP), D. Clarke (IPGP), N. M. Shapiro (IPGP), M. Campillo (LGIT), E. Larose (LGIT)Laboratoire de Gophysique Interne et Tectonophysique (Grenoble)Institut de Physique du Globe de Paris/ Observatoire Volcanologique du Piton de la Fournaise

  • Noise sourcesShapiro et al. (2005)sensorVirtual seismic source reconstruction

  • A case study: Piton de la Fournaise volcano, La Runion island

  • 3D velocity imaging Virtual sources

  • Brenguier et al., GRL, 2007effusive material3D velocity imaging Resultssolidified intrusivemagma bodiesPerturbations to a horizontally averaged modelPerturbations to a vertically averaged model

  • WEVp compared to Vs tomographyPrno et al., JVGR, 2009

  • ProspectsNeed to invert for a joint Vp/Vs tomographic modelStudy of the link between seismicity and solidified intrusive magma bodies or magma reservoir using double difference relocalisationImprove the Vs tomographic model by using broad-band seismic noise records

  • Synthetic velocity decreaseTemporal changes of seismic velocities using cross-correlations of seismic noise

  • Velocity changes on Piton de la Fournaise

  • Brenguier et al., Nature Geoscience, 2008Velocity drops preceding eruptions

  • Velocity change regionalization

  • Seismic velocity changes as a proxy for magma forcing (1)Magma forcing involves dilatancy of volcanic edificesShih-Che Yuan, J. P. Harrison (2004), An empirical dilatancy index for the dilatant deformation of rock International Journal of Rock Mechanics and Mining Sciences, Volume 41, Issue 4= magma forcingWe use the term magma forcing do describe the mechanisms of stress induced magma pressurization and injection.

  • Seismic velocity changes as a proxy for magma forcing (2)O'Connell, R. J., and B. Budiansky (1974), Seismic Velocities in Dry and Saturated Cracked Solids, J. Geophys. Res., 79(35), 54125426 Seismic velocities are strongly sensitive to crack density.

  • Link between temporal changes and structure

  • Long-term velocity changesClarke et al., In preparationcoherencecoherenceALL STATIONSSUMMIT STATIONSRelative travel time changeRelative travel time changeVELOCITY DECREASESyear

  • Peltier et al., JVGR, 2009Relative travel time changeyearEruptive cyclescoherence

  • Conclusions

    We measure relative velocity changes with a precision of 0.02 %,These changes are linked to dilatation induced by stress changes,We identified precursors to the volcanic eruptions.

    Prospects

    We are looking to localize the velocity changes at depth (4D tomography),Develop real-time passive monitoring procedures in Observatories,

    Conclusions and prospects

  • UnderVolc project20 broad-band seismometers + 16 gps + 1 infrasound sensor + photogrammetric system Continuous recording and radio real-time data transfer and data distribution at day+1

  • Thank you for your attention !Related presentations:

    S23C-03. Temporal changes of seismic wavefield during the 2007 eruptions of Piton de la Fournaise, La Runion island . Y. Aoki; V. Ferrazzini S53A-1811

    V23D-2107. A real time process for detection, clustering, and relocation of volcano-tectonic events at Piton de La Fournaise volcano.. F. Massin ; V. Ferrazzini; P. Bachelery; Z. Duputel We are gratefull to the Piton de la Fournaise volcanological Observatory staff for providing high quality data !

  • Toward real-time monitoringEruption of July 2006

  • http://www.fournaise.info/eruption2avril07.phpThe last eruption of April 2007Toward real-time monitoring