Japan Geoscience Union Meeting 2016

Presentation information

International Session (Poster)

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

[S-IT08] Structure and Dynamics of Suboceanic Mantle: Theories and Observations

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Jun Korenaga(Department of Geology and Geophysics, Yale University), Hitoshi Kawakatsu(Earthquake Research Institute, University of Tokyo), James Gaherty(Lamont Doherty Earth Observatory), Kiyoshi Baba(Earthquake Research Institute, University of Tokyo)

5:15 PM - 6:30 PM

[SIT08-P04] Possibility of anisotropic structure in electrical conductivity for the upper mantle beneath northwestern Pacific Ocean

*Kiyoshi Baba1, Hisashi Utada1 (1.Earthquake Research Institute, The University of Tokyo)

Keywords:marine magnetotellurics, electrical conductivity, anisotropy, lithosphere, asthenosphere, Northwestern Pacific Ocean

We have estimated isotropic one-dimensional (1-D) structure in electrical conductivity beneath the northwestern Pacific through Normal Oceanic Mantle Project. However, the model did not explain observed magnetotelluric (MT) responses perfectly. The misfits should be attributed to the lateral heterogeneity and/or anisotropic structure. In this study, we examined if some possible anisotropic structures can explain the observed MT responses better or not. We consider anisotropic structures that the conductivity in the asthenospheric mantle is higher in the direction parallel to the current plate motion (~N63°W) and that the conductivity in the lithospheric mantle is higher in the direction parallel to the past plate spreading direction (~N22°W). We also consider the effect on surface heterogeneity due to ocean-land distribution and bathymetric change. We simulated MT responses in the survey area A (northwest of the Shatsky Rise) to the 3-D surface heterogeneity over 1-D anisotropic structures and compared with the MT responses observed and simulated to the isotropic model. The result showed that any models considered in this study did not improve the misfit to the data, suggesting that rather laterally heterogeneous structure is more likely.