Mechanical and hydrological effects of seamount subduction on megathrust stress and slip
Mechanical and hydrological effects of seamount subduction on megathrust stress and slip
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DOI：
10.1038/s41561-020-0542-0
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发表时间：
2020-03-01
影响因子：
18.3
通讯作者：
Ellis, Susan
中科院分区：
文献类型：
--
作者：
Sun, Tianhaozhe;Saffer, Demian;Ellis, Susan
在海山俯冲过程中不断变化的应力和孔隙流体压力，如结合了机械和水文过程的数值模型所模拟的，有助于解释观察到的巨型逆冲断层滑动模式，据认为，粗糙海底和海山的俯冲会影响一系列广泛的地球动力学过程，包括巨型逆冲断层滑动行为、弧前流体流动和上覆板块的长期结构演变。虽然有许多概念模型描述海山俯冲的影响，但我们对潜在变形和流体过程的定量和机械理解仍然不完整。在这里，我们调查沉积物固结，断层和应力和孔隙流体压力的演变之间的相互作用，在响应海山俯冲，使用的数值模型，耦合机械和水文过程，并受到实验室和现场观测。研究结果表明，俯冲地形驱动了构造载荷、沉积物固结和大型逆冲断层应力状态的显著空间变化。俯冲海山前缘下倾，挤压和排流作用增强，断层正应力大，围岩超固结。海山尾流中的应力阴影导致沉积物孔隙度异常高。这些变化有助于解释所观察到的大规模逆冲断层滑动模式，地震和微震活动有利于海山的下倾边缘，而上倾应力阴影中的滑动或缓慢滑动。
Changing stresses and pore fluid pressures during subduction of seamounts, as simulated with a numerical model that couples mechanical and hydrological processes, help explain observed patterns of megathrust slip.Subduction of rough seafloor and seamounts is thought to impact a broad range of geodynamic processes, including megathrust slip behaviour, forearc fluid flow and long-term structural evolution in the overriding plate. Although there are many conceptual models describing the effects of seamount subduction, our quantitative and mechanistic understanding of the underlying deformation and fluid processes remains incomplete. Here we investigate the interplay between sediment consolidation, faulting and the evolution of stress and pore fluid pressure in response to seamount subduction, using a numerical model that couples mechanical and hydrological processes and is constrained by laboratory and field observations. Our results show that subducting topography drives marked spatial variations in tectonic loading, sediment consolidation and megathrust stress state. Downdip of a subducting seamount on its leading flank, enhanced compression and drainage lead to large fault-normal stress and overconsolidated wall rocks. A stress shadow in the seamount's wake leads to anomalously high sediment porosity. These variations help explain observed patterns of megathrust slip, with earthquakes and microseismicity favoured at the downdip edge of seamounts and aseismic or slow slip in the updip stress shadow.