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Observatoires sous-marins et r le pour la d tection des glissements sous-marins et des tsunamis

Tsunami Sources. EarthquakesTsunami source modelStatic (before/after) topography changeA priori knowledge of fault geometry is requiredVolcanoesMultiple source typesCaldeira collapse (Santorin, Krakatau)LandslidesExplosionsSlope instabilitesTsunami source modelDynamic effects must be includedDetectionRemote vs. in situ sensors .

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Observatoires sous-marins et r le pour la d tection des glissements sous-marins et des tsunamis

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    1. Observatoires sous-marins et rôle pour la détection des glissements sous-marins et des tsunamis Pierre Henry, CEREGE - Collège de France Roland Person, IFREMER, Brest Anne Deschamps, Nicole Bethoux, Geosciences Azur, Villefranche-sur-Mer et Sophia-Antipolis

    2. Tsunami Sources Earthquakes Tsunami source model Static (before/after) topography change A priori knowledge of fault geometry is required Volcanoes Multiple source types Caldeira collapse (Santorin, Krakatau) Landslides Explosions Slope instabilites Tsunami source model Dynamic effects must be included Detection Remote vs. in situ sensors

    3. New sounds from the shallow and deep ends of subduction

    4. Very low frequency earthquakes - Obara and Ito (2005)

    5. Related Questions - What is the difference between an accretionary wedge and a landslide ? Detection What is the importance of slow slip (rupture propagation velocity << Rayleigh wave velocity) in tsunami generation during an earthquake ? How do silent slip events make noise ? Prevision Is the catastrophic evolution of landslides controlled by the properties of the sliding surface ? What controls the seismic-aseismic transition in subduction zones ? Mechanics How does fluid pressure vary in a decollement and how does it relate with deformation ?

    6. Sismomètres fond de mer large bandes

    7. LIMO Installatin of (Cabled) Borehole Observatories on the Ligurian Margin Pierre Henry, Roland Person, Charles K. Paull, Nicole Béthoux, Anne Deschamps, Achim Kopf, Sébastien Migeon, Barbara Romanowicz, Etienne Ruellan, Françoise Sage, Bruno Savoye, Ralph Stephen, Nabil Sultan.

    8. Observatory context ESONET Network of Excellence Optical cable link to ANTARES Neutrino telescope IODP needs test site for borehole instrumentation Ifremer center in Toulon can provide logistic support (ROV servicing)

    9. LIMO - Science focus Approach gravity driven processes at different scales Alpine collapse, margin failure and subduction initiation Failure of sedimented slope Coupling between stress, pore-pressure and strain external forcing (sea level, fluid migration, sedimentation and compaction, airports) vs. internal processes (dilatancy, compaction) Influence of coastal aquifers on offshore slope stability

    10. Seismometer borehole(s) Cased (ROV accessible) hole Broadband Test short period strings (SEIS-Cork) Location Ideally: above seismicity cluster N of Var canyon Alternate: on Var Levee

    11. Hydrogeology boreholes Address permeability-scale dependency in clay rich hemipelagite/turbidite series. Develop alternatives to packers and CORKs.

    12. Submarine slope monitoring Strain and pore pressure Observatory components repeat AUV surveys -> evolution of morphology (E. Ruellan) seafloor OBS + tiltmeter (P. Charvis, Y. Guglielmi) Fiber optic distributes strain and temperature sensor network below seafloor pore pressure, temperature (N. Sultan, J.F. Rollin) electrical conductivity (coastal sites - P. Pezard) strain (tiltmeters ?) Implementation Need for a seafloor drill -> alternate platform MeBo ? (Bremen University, A. Kopf) Telemetry

    13. What will be the main benefit for society ? Awareness Would Damocles feel better with a strain meter ?

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