The Fine Structure of a Seismogenic Zone Revealed by Aftershocks of the 2014 Iquique Mw 8.1 Earthquake

大多数全球地震都发生在俯冲带上。在大地震(M&GT；8)中，沿着这些会聚的板块边界，板块之间的界面向下破裂到约40公里深。海沟标志着俯冲的开始，发生大破裂的地震孕育区几乎完全位于海洋前弧下。拟议项目的目的是利用余震序列的高分辨率定位技术，加深我们对结构对海洋前弧震后松弛过程的影响的理解。在这里，我们想要集中在智利北部的侵蚀边缘，2014年4月1日发生的8.1级伊基克地震打破了海洋弧前。我们建议将2014年12月至2016年11月期间安装的14个海底观测站24个月的连续数据与IPOC永久网络和临时陆上观测站的数据结合起来。近海OBS数据与陆上地震学数据的整合提供了一个岸线交叉数据集，该数据集具有全面成像智利北部前弧实体的出色能力。以前的数据集只能捕捉到大陆架以下的近海区域或从弧线到海岸线的陆上部分。在这里，我们有弥合这一差距的独特机会。特别是，我们想要调查2014年破裂地区的地震活动，以及向伊基克地震南部剩余地震空区的过渡，上次地震是在1877年破裂的。在该项目的第一阶段，我们计划对地震活动进行探测和定位，以获得高分辨率的地震目录。这将有助于解决地震后活动与构造特征之间的空间关系，如板块界面的地形变化、张性断层、孕震带的内部结构或瞬时流体向上覆板块的迁移，从而建立脱水过程与上板块地震活动分布之间的可能联系。在此基础上，应用局部地震层析成像技术，确定了弧前的二维和三维速度结构和波速比，有助于更好地了解弧前的横向和下倾构造变化。这些发现将与最近的高分辨率反射地震网格和2016年与RV Langseth获得的3D折射实验数据集的结果一起进行解释。因此，这里提出的项目的目标是一种独特的整体方法，将岸线交叉地震学数据与来自2D和3D活动地震实验的信息以及对构造分段数据的构造约束相结合。

The majority of global earthquakes occur along subduction zones. During great earthquakes (M>8) along these convergent plate boundaries the interface between the plates ruptures down to depths of ~40 km. The trench marks the onset of subduction and the seismogenic zone where large ruptures occur is almost exclusively located beneath the marine forearc. The objective of the proposed project is to nurture our understanding of the structural influence on postseismic relaxation processes of a marine forearc using high-resolution location techniques of an aftershock sequence. Here, we want to focus on the erosive margin in North Chile where the Mw 8.1 Iquique earthquake on 1 April 2014 ruptured the marine forearc. We propose to combine 24 months of continuous data from 14 ocean bottom stations (OBS) installed between December 2014 and November 2016 with the data from the permanent IPOC network and temporary landstations. The integration of the offshore OBS data with the onshore seismology data provides a shore-line crossing data set with the exceptional capability to fully image the Northern Chilean forearc in its entity. Previous data sets were only capable to capture the offshore domain up to the continental shelf or the onshore portion from the arc to the coastline. Here, we have the unique opportunity to bridge this gap. In particular, we want to investigate seismicity in the 2014 rupture area and the transition to the remaining seismic gap to the south of the Iquique earthquake, which last ruptured in 1877. In the first phase of the project we plan to detect and locate the seismicity in order to obtain a high-resolution earthquake catalogue. This will allow resolving the spatial relation between postseismic activity and structural features such as variations in the topography of the plate interface, splay faults, internal structure of the seismogenic zone or transient fluid migration into the overriding plate, to establish a possible correlation between dehydration processes and the seismicity distribution in the upper plate. Then, local earthquake tomography will be applied to determine the 2D and 3D vp and vp/vs velocity structure and will contribute to a better understanding of lateral and downdip structural changes of the forearc. The findings will be jointly interpreted with the results of a recent high-resolution reflection seismic grid and a 3D refraction experiment dataset acquired during 2016 with RV Langseth. The project proposed here hence targets a unique holistic approach by combining shore-line crossing seismology data with information from 2D and 3D active seismic experiments and structural constraints on tectonic segmentation data.