[S-CG56] 変動帯ダイナミクス

[SCG56-01] アジョイント法を用いたマントルの熱対流の復元

★招待講演

*中尾 篤史¹、桑谷 立¹、伊藤 伸一²、長尾 大道² (1.国立研究開発法人海洋研究開発機構 海域地震火山部門、2.東京大学 地震研究所)

キーワード：アジョイント法、逆問題、層流、マントル対流、流体力学

Active tectonic zones, including the Japan Island Arc, are characterized by partial melting and complex deformation due to material and heat supply and stress concentration. Quantifying active tectonic zones is therefore key to understanding the volcanism and seismicity. However, we have little direct information about active tectonic zones: geophysical observations, including seismic and electromagnetic tomography, provide only the current crust and mantle state and no time series, while geological observations provide only surface information and no information about the Earth's deep interior. Therefore, it is necessary to resolve the unknown parameters of active tectonic zones, such as deep stress, flow, and deformation processes, by combining observations and geodynamic theory. We then developed an adjoint-based data assimilation code for plate motion and mantle convection. The algorithm iteratively solves the forward and adjoint equations of mass, momentum, and energy conservation to minimize the error between observed and modeled values of plate velocities and mantle temperature. We will present the results of data assimilation on a simple 2-D Cartesian coordinate using synthetic data, and show how past mantle thermal convection is reconstructed as a function of the assimilated data and flow structures.