A reassessment of outer-rise seismicity and its implications for the mechanics of oceanic lithosphere
A reassessment of outer-rise seismicity and its implications for the mechanics of oceanic lithosphere
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DOI：
10.1093/gji/ggu013
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发表时间：
2014-04-01
影响因子：
2.8
通讯作者：
Jackson, J.
中科院分区：
文献类型：
--
作者：
Craig, T. J.;Copley, A.;Jackson, J.
本文采用体波模拟方法对俯冲带外隆起和外海沟斜坡下的海洋岩石圈内发生的全球性地震的震源参数进行了约束。这些数据随后被用来绘制下行板块弯曲进入俯冲带时岩石圈的应力状态图。我们的研究结果为海洋岩石圈外隆断裂提供了新的约束条件，这对于理解板块驱动力在俯冲系统中的传递具有重要意义。在所有情况下，浅层正断层地震都是在板块顶部观测到的，与任何更深的逆冲断层地震在深度上是分开的。在外隆起各类型断层的深度范围中，没有发现与俯冲界面上的大型逆冲断层地震相关的时间变化。从沟槽法向伸展到压缩的过渡深度与变形主要由板拉引起的面内应力和弯曲应力共同驱动的模型一致。结合地震学对板块弹性核厚度的约束和板块曲率的估计，我们给出了外隆起岩石圈强度的上限，对于恒定屈服应力模型，岩石圈强度要求小于或接近300 MPa，或者由小于或接近0.3的有效摩擦系数控制。
We use body-waveform modelling to constrain the source parameters of earthquakes occurring globally in oceanic lithosphere beneath the subduction zone outer rise and outer trench slope. These data are then used to map the stress state in the lithosphere of the downgoing plate as it bends into the subduction zone. Our results provide new constraints on the faulting of oceanic lithosphere at the outer rise, which is important for understanding the transmission of plate-driving forces through the subduction system. In all cases, shallow normal-faulting earthquakes are observed at the top of the plate, and are separated in depth from any deeper thrust-faulting earthquakes. No temporal variation associated with large thrust-faulting earthquakes on the subduction interface is seen in the depth extent of each type of faulting at the outer rise. The transition depth from trench-normal extension to compression is found to vary in agreement with models in which deformation is driven by the combination of in-plane stresses and bending stresses, resulting principally from slab pull. Combining the seismologically derived constraints on the thickness of the elastic core of the plate with estimates of the plate curvature, we place upper bounds on the strength of the lithosphere at the outer rise, which is required to be less than or similar to 300 MPa for a constant yield stress model, or governed by an effective coefficient of friction of less than or similar to 0.3.