| Zhang Fan,Lin Jian,Zhou Zhiyuan. 2019. Intra-trench variations in flexural bending of the subducting Pacific Plate along the Tonga-Kermadec Trench. Acta Oceanologica Sinica, 38(11):81－90 |
| Intra-trench variations in flexural bending of the subducting Pacific Plate along the Tonga-Kermadec Trench |
| 汤加-克马德克海沟俯冲板块挠曲变形与板块弱化 |
| Received:April 26, 2018 |
| DOI：10.1007/s13131-019-1493-4 |
| Key words:Tonga-Kermadec Trench|horizon deep|axial vertical force|axial bending moment|effective elastic thickness|flexural curvature analysis |
| 中文关键词: 汤加-克马德克海沟 地平线深渊 海沟轴垂直荷载 海沟轴弯矩 板块有效弹性厚度 板块曲率分析 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41976064, 91958211, 41890813, 91858207, 91628301, U1606401, 41976066 and 41706056; the Programs of the Chinese Academy of Sciences under contract Nos Y4SL021001, QYZDY-SSW-DQC005 and 133244KYSB20180029; the National Key Research and Development Program of China under contract Nos 2018YFC0309800 and 2018YFC0310100; the China Ocean Mineral Resources R&D Association under contract No. DY135-S2-1-04. |
| Author Name | Affiliation | E-mail | | Zhang Fan | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 510301, China | | | Lin Jian | Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | jlin@whoi.edu | | Zhou Zhiyuan | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 510301, China | |
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| Abstract: |
| We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench. Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles. Results of the analyses revealed significant along-trench variations in plate flexural bending: the trench relief (W0) of 1.9 to 5.1 km; trench-axis vertical loading (V0) of –0.5×1012 to 2.2×1012 N/m; axial bending moment (M0) of 0.1×1017 to 2.2×1017 N; effective elastic plate thickness seaward of the outer-rise region (TeM) of 20 to 65 km, trench-ward of the outer-rise (Tem) of 11 to 33 km, and the transition distance (Xr) of 20 to 95 km. The Horizon Deep, the second greatest trench depth in the world, has the greatest trench relief (W0 of 5.1 km) and trench-axis loading (V0 of 2.2×1012 N/m); these values are only slightly smaller than that of the Challenger Deep (W0 of 5.7 km and V0 of 2.9×1012 N/m) and similar to that of the Sirena Deep (W0 of 5.2 km and V0 of 2.0×1012 N/m) of the Mariana Trench, suggesting that these deeps are linked to great flexural bending of the subducting plates. Analyses using three independent methods, i.e., the TeM/Tem inversion, the flexural curvature/yield strength envelope analysis, and the elasto-plastic bending model with normal faults, all yielded similar average Te reduction of 28%–36% and average Te reduction area S△Te of 1 195–1 402 km2 near the trench axis. The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes. Comparisons of the Manila, Philippine, Tonga-Kermadec, Japan, and Mariana Trenches revealed that the average values of TeM and Tem both in general increase with the subducting plate age. |
| 中文摘要: |
| 本文详细研究了太平洋俯冲板块沿着位于西南太平洋的汤加-克马德克（Tonga-Kermadec）海沟的变形特征，定量分析了的板块弹塑性挠曲沿着海沟的变化。本研究通过拟合板块挠曲剖面来计算海沟轴处的垂直荷载、弯矩及板块有效弹性厚度的变化，结果揭示了沿汤加-克马德克海沟俯冲板块挠曲变形的巨大变化：由应力造成的海沟深度（W0）的变化范围为1.9到5.1公里：海沟轴处垂直荷载（V0）的变化范围为-0.5 1012到2.2 1012 N/m：海沟轴处弯矩（M0）的变化范围为0.1 1017到2.2 1017 N。在海沟前缘隆起处（outer rise）向海一侧，各组剖面的板块有效弹性厚度（TeM）的变化范围为20到65公里：而在向海沟轴一侧，板块有效弹性厚度（Tem）的变化范围为11到33公里，由从最大到最小弹性厚度的减小发生在距离海沟轴处（xr）20到95公里处。汤加海沟最深处的地平线深渊（Horizon Deep）为世界第二深的深渊，其受力变形深度（W0=5.1 km）以及海沟轴处所受垂直荷载（V0=2.2 1012 N/m）都为汤加海沟的最大，只比马里亚纳海沟的挑战者深渊（Challenger Deep）处稍小（W0=5.7 km，V0=2.9 1012 N/m），而与第三大深渊塞丽娜深渊（Sirena Deep）相似（W0=5.2 km，V0=2.0 1012 N/m），以上结果表明这些深渊均与巨大的板块挠曲变形有关。本文通过三种独立方法来研究俯冲板块有效弹性厚度在海沟附近的减小程度，包括TeM/Tem反演，板块挠曲曲率/屈服强度包络分析，以及弹塑性弯曲模型及正断层模拟。三种方法所得到的结论基本一致：板块有效弹性厚度在海沟附近平均减小了28-36%，减小面积为1195到1402 km2，其范围与观测到的板块前缘隆起处正断层地震分布情况吻合。本文还对比研究了马尼拉、菲律宾、汤加-克马德克、日本及马里亚纳海沟的俯冲板块绕曲变形，结果显示俯冲板块的有效弹性厚度在向海一侧的值（TeM）以及在海沟轴附近的值（Tem）均与俯冲板块年龄成正比。 |
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