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SUMMARY:The mechanics of intermediate and deep focus earthquakes
DTSTART:20160318T121500
DTEND:20160318T131500
DTSTAMP:20260506T071800Z
UID:681c0508f6a0611eb8c3995b32a056f108b25fe3143ecc22b7a97d7c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Dr Alexandre Schubnel\, Associate Researcher at CNRS and
  Associate Professor at ENS\, Paris\, France\nAt least part of the subduct
 ing slab seismic activity could be triggered by phase transformations and 
 mineral reactions. However\, the way mineral reactions can modify the defo
 rmation regime of deep rocks\, from ductile to brittle (embrittlement) is 
 still poorly understood and remains one of the outstanding unsolved proble
 ms of geophysics and rock mechanics.\nHere\, we provide experimental evide
 nce that\, under differential stress at high pressure and temperature cond
 itions (3-5GPa/800-1000°C)\, shear fractures nucleate and propagate at th
 e onset of the olivine -> spinel transition in the Mg2GeO4 analogue system
 . The propagation of these fractures is sufficiently rapid to radiate ener
 gy in the form of intense acoustic emissions (AEs). Using a similar set-up
 \, a second set of experiments demonstrates that glaucophane and lawsonite
  mixtures\, two of the principal mineral water carriers in the subducted o
 ceanic crust\, undergo dynamic fracture instabilities when deformed within
  the eclogite field (3GPa/400-800°C). This time\, AEs are observed due re
 spectively to the glaucophane breakdown into jadeite and talc under low te
 mperature and lawsonite dehydration under higher temperature. Finally\, de
 formation experiments performed on partially serpentinized peridotites at 
 2-4 GPa\, 500-700°C\, demonstrate that 5% serpentine in sufficient to tri
 gger dehydration embrittlement of the peridotite body. In this case\, low 
 serpentine contents may favor initiation of mechanical failure of the oliv
 ine “load bearing” network.\n  Put together\, our observations provid
 e strong experimental evidence of the role played by mineral reactions on 
 earthquake triggering in mantle conditions\, both in the Wadati-Benioff do
 uble plane of seismicity and in the Earth mantle's transition zone.\n(full
  abstract as pdf available on memento)\nBio : Alexandre Schubnel has a dou
 ble appointment:\n1) as an associate researcher at the Centre National de 
 la Recherche Scientifique\, and\n2) as an associate professor at the Labor
 atoire de Géologie of Ecole Normale Supérieure in Paris\, France. His re
 search interests lie in experimental Rock Physics and Earthquake Mechanics
 . In 2014\, Alexandre Schubnel was awarded the bronze medal of CNRS and th
 e Gouilloud-Schlumberger award of the French National Academy of Sciences 
 for his work on  “laboratory earthquakes"The mechanics of intermediate 
 and deep focus earthquakes
LOCATION:GCB330 http://plan.epfl.ch/?lang=fr&room=GCB330
STATUS:CONFIRMED
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