Steady‐State Effective Normal Stress in Subduction Zones Based on Hydraulic Models and Implications for Shallow Slow Earthquakes
Steady‐State Effective Normal Stress in Subduction Zones Based on Hydraulic Models and Implications for Shallow Slow Earthquakes
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基于水力模型的俯冲带稳态有效正应力及其对浅层慢地震的影响
DOI：
10.1029/2022jb025995
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Noda Hiroyuki
中科院分区：
文献类型：
--
作者：
Kaneki Shunya;Noda Hiroyuki
有效正应力的空间分布对于理解断层运动是必不可少的。虽然Rice（1992，https：//doi.org/10.1016/s0074-6142（08）62835-1）提出了一个具有恒定流体性质的垂直走滑断层带的稳态解，但基于Rice（1992，https：//doi.org/10.1016/s0074-6142（08）62835-1）概念的适用于其他构造环境的模型尚未开发。这种模型在俯冲带中特别重要，因为人们经常讨论低震和慢震之间的关系。为了定量研究俯冲带浅区局部减少的原因，我们进行了模型计算，将俯冲带的特征机制。我们的基本模型考虑了蒙皂石脱水效应和俯冲的机械效应，得出的结果与Rice（1992，https：//doi.org/10.1016/s0074-6142（08）62835-1）报道的结果一致：梯度随深度的增加而显著减小，而实际流体性质排除了在深度处几乎恒定的可能性。我们得到了一个单调增加，随着深度的增加，物理上合理的解决方案，并未能产生一个本地减少。展布断层和流体泄漏的存在，但不能局部减少。我们发现，局部的渗透性下降，局部周围的不透水带，因此，可能会导致发生浅慢地震。由脱水反应引起的水释放可能不是主导因素，尽管蒙脱石脱水释放二氧化硅并促进其沉淀。
The spatial distribution of effective normal stress, , is essential for understanding the fault motion. Although Rice (1992, https://doi.org/10.1016/s0074-6142(08)62835-1) proposed a steady‐state solution for a vertical strike‐slip fault zone with constant fluid properties, models that are based on the concept by Rice (1992, https://doi.org/10.1016/s0074-6142(08)62835-1) and are applicable for other tectonic settings have not yet been developed. Such a model is particularly important in subduction zones because the relationship between low and slow earthquakes is often discussed. To quantitatively examine the causes of a local decrease in on a shallow region of the subduction zone, we performed model calculations that incorporated mechanisms characteristic to subduction zones. Our basic model, which considers the effect of smectite dehydration and the mechanical effect of subduction, yields results that are consistent with those reported by Rice (1992, https://doi.org/10.1016/s0074-6142(08)62835-1): the gradient of remarkably decreases with the increase in depth, whereas the realistic fluid properties rule out nearly constant at depth. We obtained a monotonic increase in with the increase in depth for the physically sound solutions and failed to generate a local decrease in . The presence of a splay fault and fluid leakage though it cannot decrease locally. We found that a local decrease in permeability decreased locally around an impermeable zone and, thus, possibly led to the occurrence of shallow slow earthquakes. The water release caused by the dehydration reaction may not be the dominant factor, although smectite dehydration releases silica and promotes its precipitation.
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