日本地球惑星科学連合2018年大会

講演情報

[EJ] ポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS10] 地震波伝播:理論と応用

2018年5月24日(木) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:西田 究(東京大学地震研究所)、白石 和也(海洋研究開発機構)、新部 貴夫((株)地球科学総合研究所、共同)、澤崎 郁(防災科学技術研究所)

[SSS10-P13] 東北沖の陸海統合3次元構造モデルに基づくアジョイントカーネルの計算と波形インバージョンによる構造モデル改良の考察

*岡元 太郎1竹中 博士2中村 武史3 (1.東京工業大学 理学院 地球惑星科学系、2.岡山大学大学院 自然科学研究科、3.防災科学技術研究所 地震津波防災研究部門)

キーワード:アジョイント・カーネル、3次元差分法、GPU計算

At the subduction zones, the heterogeneous structure strongly affects the propagation of the seismic waves. Such structural effect can cause significant distortions in the waveforms and biases in the estimation of the earthquake source parameters, including the earthquake locations. Thus it is important to construct precise three-dimensional (3D) structure models with which we are able to reproduce the seismic waveforms from the subduction zone earthquakes. In this paper, we study the sensitivity kernels to improve the parameters of the structure model at the Tohoku-oki area of the Japan trench. We generate the sensitivity kernels based on the method presented by Tanimoto and Okamoto (2014). The forward and adjoint wavefields are computed based on a land-ocean unified 3D structure model (Okamoto et al. submitted). Thus the “starting model” of the inversion is a 3D model, not a standard, one-dimensional model. The numerical simulations are performed using the scheme of HOT-FDM (Nakamura 2012) with multi-GPU acceleration (Okamoto et al. 2013) on the TSUBAME supercomputer at Tokyo Institute of Technology. As a preliminary analysis, we selected a single component from a station (TYS from F-net of NIED) for a shallow interplate earthquake on 2003/11/1 (Mw5.8). In order to reduce the biases in the earthquake parameters used in generating the synthetic waveforms, they are estimated by FAMT method (Okamoto et al. 2017) based on the 3D model. We construct the sensitivity kernels of rigidity for frequency components from 0.024 to 0.53 Hz (210 components in total). The size of the target region is 300 km x 350 km in horizontal and 15 km in vertical, and the region is divided into sub-blocks of 50 km x 50 km x 5 km. Then we invert the residuals between the observed and synthetic spectral components (Fourier coefficients) for the rigidity perturbations of the blocks. This preliminary result shows perturbations with amplitudes of about 1 to a few percent at each of the layers. We will presents further inversion analysis and discuss the improvements in the spectral components and waveforms. (We are grateful to NIED for providing the waveform data. This research is partially supported by KAKENHI (16K05535), HPCI System Research Project (Project ID: hp130118) and JHPCN (Project ID: jh170022-NAJ).)