Zenisu Ridge: mechanical model of formation
Zenisu Ridge: mechanical model of formation
复制标题
Zenisu 海岭：地层力学模型
DOI：
10.1016/0040-1951(89)90390-9
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发表时间：
1989
期刊：
影响因子：
2.9
通讯作者：
X. Pichon
中科院分区：
文献类型：
--
作者：
N. Chamot‐Rooke;X. Pichon
在Kaiko项目期间进行了海束、地震和潜水调查，发现菲律宾海板块东北端有显著的挤压变形，这与最近伊豆-小川弧与日本中部的碰撞有关。泽尼苏海脊是南开海槽以南几十公里处的一个线性地形高地，其底部的洋内逆冲作用得到了构造、磁力和重力数据的支持。我们从一块弹塑性薄板的压缩力学破坏的角度研究了泽尼苏山脊的形成，该薄板在海沟处俯冲并受到区域轴向力的作用。在整个数值计算中使用了流变包络的概念。基于对现今远离变形区的弯曲的详细研究，我们估计了所涉及的弯曲力：隆起高120~150m，沿南开海槽的压应力约为−100 Mpa。在泽尼苏岭地区，由于伊豆半岛附近的碰撞，叠加了额外的压应力。我们计算了破坏前的偏应力垂直分布，发现偏应力在沟槽区深度20-25公里处最大，在凸起附近的海面60-100公里处再次最大。讨论了在整个岩石圈厚度范围内连接这两个极大值的逆冲力的发展。该模型预测，泽尼苏海脊的形成不是在4 Ma之前，而是在海脊接近南开海槽时，由于弯曲应力的重新分布而导致的渐进式构造抬升。
Seabeam, seismic and submersible surveys took place during the Kaiko Project and revealed significant compressive deformation at the northeastern end of the Philippine Sea plate, related to the recent collision of the Izu-Ogasawara Arc against Central Japan. Intraoceanic thrusting at the base of the Zenisu Ridge, a linear topographic high running a few tens of kilometers south of the Nankai Trough, is supported by tectonic, magnetic and gravimetric data. We investigate the formation of the Zenisu Ridge in terms of compressive mechanical failure of a thin elastic-perfectly plastic plate, subducting at a trench and subject to a regional compressive axial force. The rheological envelope concept is used throughout the numerical calculations. Based on a detailed study of flexure of the present-day bending far from the deformation zone, we evaluate the bending forces involved: the bulge is 120 to 150 m high and the compressive stress all along the Nankai Trough is about −100 MPa. In the Zenisu Ridge area, an additional compressive stress is superimposed due to the nearby collision at Izu-Peninsula. We compute the vertical distribution of the deviatoric stress before failure and find that the deviatoric stress is maximum at a depth of 20–25 km in the trench area, and again at the surface 60 to 100 km seaward, in the vicinity of the bulge. The development of a thrust joining these two maxima through the entire thickness of the lithosphere is discussed. The model predicts that the formation of the Zenisu Ridge did not occur before 4 Ma and is caused by progressive tectonic uplift due to the redistribution of bending stresses as the ridge approaches the Nankai Trough.