From Slab Coupling to Slab Pull: Stress Segmentation in the Subducting Nazca Plate
From Slab Coupling to Slab Pull: Stress Segmentation in the Subducting Nazca Plate
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DOI：
10.1029/2018gl078793
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发表时间：
2018-06-16
影响因子：
5.2
通讯作者：
Shapiro, Serge A.
中科院分区：
文献类型：
--
作者：
Bloch, Wasja;Schurr, Bernd;Shapiro, Serge A.
我们调查的应力场，纳斯卡板块在俯冲过程中经历的南美板块下，确定的震源机制的中度俯冲相关的地震连续从20至120公里的深度和反转的应力方向的四个板块区域。我们的研究结果表明，急剧终止的耦合带，其特征是挤压应力，隆起的覆盖山脉，并可能激活预先存在的板状结构。在该区域的上方和下方，板拉力是主要应力。在板表面附近，我们还发现了遗传结构激活的标志。在板块的更深处，断层的方向更有可能仅由应力场控制。沿着俯冲路径，我们发现应力场的绝对板拉分量的增加与事件率的增加和发生M > 7中深地震的可能性有关。
We investigate the stress field that the Nazca slab experiences during subduction beneath the South American plate by determining the focal mechanisms of moderate subduction-related earthquakes continuously from 20- to 120-km depth and inverting for the stress directions of four slab regions. Our results show the sharp termination of the coupling zone, which is characterized by compressional stresses, uplift of the overlying mountain range, and likely the activation of preexisting slab structures. Beyond and below this zone slab pull is the dominant stress. Near the slab surface, we also find signatures of the activation of inherited structures. Deeper in the slab, fault orientations are more likely controlled by the stress field alone. Along the subduction pathway, we find indication for an increase of the absolute slab pull component of the stress field that correlates with an increase in event rate and the occurrence possibility of M > 7 intermediate depth earthquakes.