Japan Geoscience Union Meeting 2018

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Tectonophysics

[S-IT27] Property and role of liquids inside the Earth

Tue. May 22, 2018 9:00 AM - 10:30 AM A11 (Tokyo Bay Makuhari Hall)

convener:Tatsuya Sakamaki(Department of Earth Science, Tohoku University), Yoichi Nakajima(Kumamoto University, Priority Organization for Innovation and Excellence), Chairperson:Sakamaki Tatsuya(Tohoku University), Nakajima Yoichi(Kumamoto University )

9:00 AM - 9:15 AM

[SIT27-01] Understanding of low velocity anomaly in the asthenosphere inferred from elastic wave velocity measurement of partially molten rocks

*Tomonori Ohashi1, Tatsuya Sakamaki1, Naoki Hisano1, Yuji Higo2, Yuki Shibazaki3, Akio Suzuki1 (1.Department of Earth Science, Tohoku University, 2.Japan Synchrotron Radiation Research Institute, 3.Frontier Research Institute for Interdisciplinary Sciences, Tohoku University)

Keywords:partial melting, elastic wave velocity, asthenosphere

The low velocity anomaly at the top of asthenosphere is one of important seismological features, and expected to be formed by carbon dioxide (CO2)-induced partial melting of mantle rock. For better constraint on the melt fraction and distribution in the low-velocity zone, a comparison between experimental velocity and geophysical observation is a straightforward approach. Here we have measured the elastic wave velocity of olivine + carbonate melt using in-situ ultrasonic technique under conditions relevant to the top of asthenosphere. Both of compressional (VP) and shear (VS) wave velocities became smaller with increasing the volume fraction of melt in the sample, and we found quantitatively the velocity attenuation as a function of melt fraction. Comparing with the low-velocity zone, we succeeded in understanding a suitable amount of melt in the asthenosphere. The presence of magmas below the lithosphere could serve as a lubricant for the dynamics of plate tectonics and be a magma source of petit-spot volcanoes located at the outer rise of the oceanic plate.