Elasto-plastic deformation and plate weakening due to normal faulting in the subducting plate along the Mariana Trench
Elasto-plastic deformation and plate weakening due to normal faulting in the subducting plate along the Mariana Trench
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马里亚纳海沟俯冲板块正断层导致的弹塑性变形和板块弱化
DOI：
10.1016/j.tecto.2018.04.008
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发表时间：
2018
期刊：
影响因子：
2.9
通讯作者：
Lin Jian
中科院分区：
文献类型：
--
作者：
Zhou Zhiyuan;Lin Jian
通过挠曲弯曲和正断层特征的分析以及地球动力学模拟，研究了马里亚纳海沟沿着俯冲板块弹塑性变形的变化。大多数正断层起始于外隆区，并向海沟轴线方向发展，走向大多与当地海沟轴线近平行。测得的平均海沟地形和最大断层落差在南部地区（分别为5公里和320米）明显大于北方和中部地区（2公里和200米）。俯冲板块被模拟为一个弹塑性板在海沟轴向受到构造载荷。计算的应变率和速度揭示了一个阵列的正断层状剪切带的上板，导致显着的故障引起的偏应力减少。然后，我们反演的解决方案，最适合观察到的挠曲弯曲和正常断层的特点，揭示正常断层渗透到海底下的深度为21，20和32公里的北方，中部和南部地区，分别与所观察到的深度重新定位的正常断层地震在马里亚纳海沟中部。计算的南部地区更深的正断层可能导致大约两倍的水被带入地幔每单位沟长度比北方和中部地区。我们进一步计算了正断层作用使南部地区的有效弹性板厚Teby局部减小了52%，北方和中部地区减小了33%。最佳拟合解显示，南部地区（51-64°）的拉力视角度大于北方（22-35°）和中部地区（20-34°），这与沿沿着马里亚纳海沟的俯冲板块的地震确定倾角总体向南增加有关。
We investigated variations in the elasto-plastic deformation of the subducting plate along the Mariana Trench through an analysis of flexural bending and normal fault characteristics together with geodynamic modeling. Most normal faults were initiated at the outer-rise region and grew toward the trench axis with strikes mostly subparallel to the local trench axis. The average trench relief and maximum fault throws were measured to be significantly greater in the southern region (5 km and 320 m, respectively) than the northern and central regions (2 km and 200 m). The subducting plate was modeled as an elasto-plastic slab subjected to tectonic loading at the trench axis. The calculated strain rates and velocities revealed an array of normal fault-like shear zones in the upper plate, resulting in significant faulting-induced reduction in the deviatoric stresses. We then inverted for solutions that best fit the observed flexural bending and normal faulting characteristics, revealing normal fault penetration to depths of 21, 20, and 32 km beneath the seafloor for the northern, central, and southern regions, respectively, which is consistent with the observed depths of the relocated normal faulting earthquakes in the central Mariana Trench. The calculated deeper normal faults of the southern region might lead to about twice as much water being carried into the mantle per unit trench length than the northern and central regions. We further calculated that normal faulting has reduced the effective elastic plate thicknessTeby up to 52% locally in the southern region and 33% in both the northern and central regions. The best-fitting solutions revealed a greater apparent angle of the pulling force in the southern region (51–64°) than in the northern (22–35°) and central (20–34°) regions, which correlates with a general southward increase in the seismically-determined dip angle of the subducting slab along the Mariana Trench.