Anisotropy-revealed change in hydration along the Alaska subduction zone
Anisotropy-revealed change in hydration along the Alaska subduction zone
复制标题
各向异性揭示了阿拉斯加俯冲带沿线水合作用的变化
DOI：
10.1130/g48860.1
复制
发表时间：
2021
期刊：
影响因子：
5.8
通讯作者：
Lynner, Colton
中科院分区：
文献类型：
--
作者：
Lynner, Colton
俯冲带中的巨型逆冲断层地震行为受多种因素控制，包括俯冲板片的水化状态。增加的水化作用通过降低构造板块之间沿着界面的物质强度来减少破坏性大地震的发生。了解俯冲带水化作用的变化对于正确评估每个区域造成的总体危害是必要的。幸运的是，地震各向异性强烈依赖于俯冲地壳和岩石圈的水化作用。我目前的剪切波分裂测量，照亮各向异性的变化，因此水合作用，俯冲太平洋板块下的阿拉斯加俯冲带（北方太平洋）。剪切波分裂的变化与大逆冲断层地震的行为变化直接相关。我的测量结果表明，舒马金地震空白的特点是一个水化俯冲板，解释了长期缺乏大地震。在紧邻的塞米迪段，定期经历重大事件，观察表明一个水化程度低得多的板块。这些结果是由太平洋板块的古扩张组构的优先排列驱动的。当组构与海沟的方向更接近时，外隆断层和板块水合作用增强。这些结果突出了在大的破坏性地震的生产中，预先存在的板结构和随后的水合作用的变化的重要性。
Megathrust earthquake behavior in subduction zones is controlled by a variety of factors including the hydration state of the subducting slab. Increased hydration reduces the occur-rence of great, damaging earthquakes by diminishing the strength of the material along the interface between tectonic plates. Understanding variations in hydration in subductions zones is necessary for properly assessing the overall hazard posed by each region. Fortunately, seismic anisotropy is strongly dependent upon hydration of the subducting crust and litho-sphere. I present shear-wave splitting measurements that illuminate changes in anisotropy, and therefore hydration, of the subducting Pacific plate beneath the Alaska subduction zone (northern Pacific Ocean). Variations in shear-wave splitting directly correlate to changes in the behavior of great, megathrust earthquakes. My measurements show that the Shumagin seismic gap is characterized by a hydrated subducting slab, explaining the long-term lack of great earthquakes. Observations in the immediately adjacent Semidi segment, which experiences great events regularly, indicate a far less hydrated slab. These results are driven by the preferential alignment of paleo-spreading fabrics of the Pacific plate. Where fabrics are more closely aligned with the orientation of the trench, outer-rise faulting and plate hydration is enhanced. These results highlight the importance of changes in preexisting slab structures and subsequent hydration in the production of great, damaging earthquakes.