Abstract On April 1, 2014, a large earthquake (Mw = 8.1) ruptured the central part of a historic seismic gap in northern Chile. In order to study the relationship between the co-seismic rupture characteristics and the crustal structure of the subduction zone, we processed a trench-perpendicular seismic reflection profile acquired across the zone of maximum slip and generated a P-wave velocity model. The results show a frontal prism in the continental wedge characterized by low velocities that increase rapidly towards the shore and acted as a barrier for trench-ward propagation of aftershocks. Landward, a transition zone with increasing upper crust velocity (4–5 km/s) concentrates most of the aftershocks. In addition, a trench-ward dipping set of fault zones is observed along the continental wedge associated to the Iquique forearc basin formation (1.5 km thick at the depocenter on this profile). We identify three stratigraphic units within the basin. A landward tilt and thickness increase is detected in each stratigraphic unit, along with growth strata and domino structures, suggesting landward migration of syn-extensional deformation in response to basal subduction erosion. By extrapolating our results to the plate boundary and based on published focal mechanisms of intra-crustal seismicity, we find a strong spatial correlation between the Iquique basin and the highest slip area for the 2014 earthquake, suggesting long-term extensional deformation due to coseismic tensional stresses.

中文翻译：

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2014年伊基克Mw8.1地震震源区上覆大陆楔的地震构造与构造

摘要 2014 年 4 月 1 日，一场大地震（Mw = 8.1）破坏了智利北部一个历史性地震裂隙的中心部分。为了研究同震破裂特征与俯冲带地壳结构之间的关系，我们处理了跨越最大滑移带的海沟垂直地震反射剖面，并生成了纵波速度模型。结果显示，大陆楔中的锋棱柱以低速度为特征，向海岸快速增加，并作为余震向海沟传播的屏障。向陆方向，上地壳速度增加（4-5 公里/秒）的过渡带集中了大部分余震。此外，沿着与伊基克弧前盆地地层相关的大陆楔观察到一组向海沟倾斜的断层带（该剖面沉积中心厚 1.5 公里）。我们确定了盆地内的三个地层单元。在每个地层单元中都检测到向陆倾斜和厚度增加，以及生长地层和多米诺骨牌结构，表明响应于基底俯冲侵蚀的同向变形向陆迁移。通过将我们的结果外推到板块边界并基于已发表的地壳内地震活动的震源机制，我们发现伊基克盆地与 2014 年地震的最高滑动区之间存在很强的空间相关性，这表明由于同震张力引起的长期拉伸变形。压力。我们确定了盆地内的三个地层单元。在每个地层单元中都检测到向陆倾斜和厚度增加，以及生长地层和多米诺骨牌结构，表明响应于基底俯冲侵蚀的同向变形向陆迁移。通过将我们的结果外推到板块边界并基于已发表的地壳内地震活动的震源机制，我们发现伊基克盆地与 2014 年地震的最高滑动区之间存在很强的空间相关性，这表明由于同震张力引起的长期拉伸变形。压力。我们确定了盆地内的三个地层单元。在每个地层单元中都检测到向陆倾斜和厚度增加，以及生长地层和多米诺骨牌结构，表明响应于基底俯冲侵蚀，同向变形向陆地迁移。通过将我们的结果外推到板块边界并基于已发表的地壳内地震活动的震源机制，我们发现伊基克盆地与 2014 年地震的最高滑动区之间存在很强的空间相关性，这表明由于同震张力引起的长期拉伸变形。压力。