| ZHOU Zhiyuan,LIN Jian,ZHANG Fan. 2018. Modeling of normal faulting in the subducting plates of the Tonga, Japan, Izu-Bonin and Mariana Trenches: implications for near-trench plate weakening. Acta Oceanologica Sinica, 37(11):53－60 |
| Modeling of normal faulting in the subducting plates of the Tonga, Japan, Izu-Bonin and Mariana Trenches: implications for near-trench plate weakening |
| 汤加、日本、伊豆-小笠原与马里亚纳海沟俯冲板块正断层模拟：对俯冲板块弱化的影响 |
| Received:March 29, 2018 |
| DOI：10.1007/s13131-018-1146-z |
| Key words:normal fault geodynamic model plate weakening flexural bending elasto-plastic deformation |
| 中文关键词: 正断层 地球动力学模拟 板块弱化 板块挠曲 弹塑性变形 |
| 基金项目: |
| Author Name | Affiliation | E-mail | | ZHOU Zhiyuan | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | LIN Jian | Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 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 | | ZHANG Fan | Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China | |
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| Abstract: |
| The plate flexure and normal faulting characteristics along the Tonga, Japan, Izu-Bonin and Mariana Trenches are investigated by combining observations and modeling of elastoplastic deformation of the subducting plate. The observed average trench relief is found to be the smallest at the Japan Trench (3 km) and the largest at the Mariana Trench (4.9 km), and the average fault throw is the smallest at the Japan Trench (113 m) and the largest at the Tonga Trench (284 m). A subducting plate is modeled to bend and generate normal faults subjected to three types of tectonic loading at the trench axis: vertical loading, bending moment, and horizontal tensional force. It is inverted for the solutions of tectonic loading that best fit the observed plate flexure and normal faulting characteristics of the four trenches. The results reveal that a horizontal tensional force (HTF) for the Japan Trench is 33%, 50% and 60% smaller than those of the Mariana, Tonga and Izu-Bonin Trenches, respectively. The normal faults are modeled to penetrate to a maximum depth of 29, 23, 32 and 32 km below the sea floor for the Tonga, Japan, Izu-Bonin and Mariana Trenches, respectively, which is consistent with the depths of relocated normal faulting earthquakes in the Japan and Izu-Bonin Trenches. Moreover, it is argued that the calculated horizontal tensional force is generally positively correlated with the observed mean fault throw, while the integrated area of the reduction in the effective elastic thickness is correlated with the trench relief. These results imply that the HTF plays a key role in controlling the normal faulting pattern and that plate weakening can lead to significant increase in the trench relief. |
| 中文摘要: |
| 通过对比实际观测与弹塑性变形模型，研究了沿着汤加、日本、伊豆-小笠原、马里亚纳海沟的板块挠曲与正断层特征。观测表明，平均海沟挠曲量在日本海沟最小（3公里），马里亚纳海沟最大（4.9公里），而平均正断层垂直断距在日本海沟最小（113米），汤加海沟最大（284米）。模拟了俯冲板块在三种构造加载的作用下发生弯曲变形并产生正断层的过程：垂向加载（V0）、弯矩（M0）和水平拉张力（F0）。在板块挠曲与正断层特征的双重约束下，反演得到了四个海沟的最佳模型解。结果显示，日本海沟的水平张力分别比马里亚纳、汤加和伊豆-小笠原海沟小33%、50%和60%。汤加、日本、伊豆-小笠原、马里亚纳海沟的正断层最深可达海底以下29，23，32和32公里，这与重新定位后的日本与伊豆-小笠原地震深度一致。此外，反演得到的水平张拉力与观测到的平均垂直断距呈一定正相关性，而计算得到的有效弹性厚度减少量与观测到的海沟挠曲量也相关。这些结果表明，水平张拉力在正断层发展过程中起着关键控制作用，板块弱化可导致板块挠曲量的显著增加。 |
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