Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG20] Intermediate-depth and deep earthquakes: their origins and material properties of subducting slabs

Tue. May 24, 2016 10:45 AM - 12:15 PM 201A (2F)

Convener:*Keiko Kuge(Department of Geophysics, Graduate School of Science, Kyoto University), Saeko Kita(National Research Institute for Earth Science and Disaster Prevention), Alexandre Schubnel(CNRS), Geoffrey Abers(Cornell University, Department of Earth and Atmospheric Sciences, New York, USA), Chair:Alexandre Schubnel(CNRS), Tatsuhiko Hara(International Institute of Seismology and Earthquake Engineering, Building Research Institute)

11:45 AM - 12:00 PM

[SCG20-11] Dehydration-driven stress transfer as a mechanism for lower Wadati-Benioff earthquakes

*Ferrand Pascal Thomas1, Nadège Hilairet2, Sarah Incel1, Damien Deldicque1, Julien Gasc3,4, Loïc Labrousse5, Joerg Renner6, Yanbin Wang4, Alexandre Schubnel1 (1.Ecole Normale Supérieure, UMR 8538, PSL Research University, Paris, 75005, France, 2.Unité Matériaux et Transformations, UMR 8207, Villeneuve d'Ascq, 59655, France, 3.Géosciences Montpellier, 34090, France, 4.GeoSoilEnviroCARS, University of Chicago, Argonne, IL 60439, USA, 5.Institut des Sciences de la Terre de Paris, Univeristé Pierre et Marie Curie, Paris, 75005, France, 6.Institut für Geologie, Mineralogie und Geophysik, Ruhr Universität Bochum, 44780, Germany)

Keywords:Antigorite, Olivine, Earthquakes, Mantle, Lower Wadati-Benioff Plane, Pseudotachylyte

Although extensively documented, intermediate-depth earthquakes (40-400 km) within subducting oceanic slabs remain enigmatic. Here we reconcile more than a decade of apparently contradictory experimental studies on the possible link between these earthquakes and serpentine dehydration. We show that for realistic compositions, antigorite dehydration triggers dynamic embrittlement of sintered olivine-antigorite aggregates deformed at confining pressure and temperature conditions representative of intermediate-depth seismicity (1 to 3.5 GPa, 500 to 800°C). At 1.1 GPa pressure, dehydration of antigorite in volume proportion as low as 5% triggers dynamic shear failure of the olivine load-bearing network. For higher contents, deformation remains silent and distributed. At 3.5 GPa pressure, acoustic emissions are observed for mixtures with up to 50% antigorite. In both cases, dehydration of antigorite proportion as low as 5% is sufficient to trigger analogs of lower Wadati-Benioff earthquakes in the laboratory. Intermediate-depth seismicity could therefore ultimately be seen as an indicator for the degree of hydration in subducting lithospheric mantle.