日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS24] 海底~海面を貫通する海域観測データの統合解析

2019年5月26日(日) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:有吉 慶介(国立研究開発法人海洋研究開発機構)、木戸 元之(東北大学 災害科学国際研究所)、稲津 大祐(東京海洋大学)、高橋 成実(防災科学技術研究所)

[MIS24-P07] ヒクランギ沈み込み帯における非潮汐成分の係数補正を用いた海底圧力計の地殻変動検出

*井上 智裕1村本 智也2稲津 大祐3伊藤 喜宏4日野 亮太5太田 和晃4鈴木 秀市5 (1.京都大学、2.産業技術総合研究所、3.東京海洋大学、4.京都大学防災研究所、5.東北大学)

Seafloor observation networks with ocean bottom pressure gauges (OBPG) are widely deployed to detect seafloor crustal deformation derived from tectonic events, such as slow slip events (SSE) now observed in many subduction zones worldwide. Data processing to detect SSE from OBPG data has, however, a serious issue, in which the observed pressure data as the height of the water column above OBPGs includes both the tidal and non-tidal components from oceanic mass shifts, as well as the tectonic components. Because the non-tidal component has amplitude and duration comparable to those of tectonic component, it should be removed from the observed data appropriately for detecting SSE. A global barotropic ocean model has been recently utilized to detect vertical displacement during SSEs from observed pressure data (e.g. Muramoto et al., 2019). Driven by assimilated surface wind vectors and air pressure at the sea surface from atmospheric disturbances (Inazu et al., 2012), the model simulates the total pressure field at the bottom of the sea. However, the modeled non-tidal components are not necessarily coincident with those of the observed records especially in amplitudes. We here propose a novel correction method to reduce the effect of non-tidal component on observed OBP records in the Hikurangi subduction margin.
To reduce the non-tidal component on observed data, we minimize differences between observed and modeled non-tidal components on OBPG data using amplitude correction factor. The observed and modeled components show high correlation with no phase difference, whereas their amplitudes are not completely consistent with each other; the amplitude of the modeled component is generally smaller than that of the observed one in the target area. After removing tidal components and instrumental drift with BAYTAP08 (Tamura et al., 2008), we calculate a correction factor that is a scaling factor of observed/modeled amplitudes of non-tidal components by minimizing the total residual between observed and corrected model amplitude. After multiplying the correction factor to the modeled one, we remove it from the observed OBPG data to reduce the non-tidal variations more effectively than previous works. As the results, variances of time series of OBP record after removal of tide and non-tidal components decreased ~ 30% at most. It is expected that detection ability of tectonic movement is improved by taking pressure differences from the record at a reference site, which is also processed by the same procedure.