Probing the Northern Chile Megathrust With Seismicity: The 2014 M8.1 Iquique Earthquake Sequence
Probing the Northern Chile Megathrust With Seismicity: The 2014 M8.1 Iquique Earthquake Sequence
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DOI：
10.1029/2019jb017794
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
Hugo Soto;C. Sippl;B. Schurr;Juliane Kummerow;G. Asch;F. Tilmann;D. Comte;S. Ruiz;O. Oncken
中科院分区：
文献类型：
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作者：
Hugo Soto;C. Sippl;B. Schurr;Juliane Kummerow;G. Asch;F. Tilmann;D. Comte;S. Ruiz;O. Oncken
我们使用了来自100个永久和临时地震台的数据来研究与2014年4月1日智利北部伊基克M8.1级地震相关的地震活动图像。对地震资料应用多阶段自动事件定位方法，共探测和定位了主震前1个月和主震后9个月的前震、余震和背景地震活动约1.9万次。前震围绕主震凹凸体的上倾边界，余震主要发生在主震凹凸体的上倾和下倾两个带上。上倾地震活动主要位于巨型逆冲带上的过渡性摩擦带，可用主震及其最大余震引起的库仑破裂应力增大而产生的慢滑过程所产生的震前应力载荷和库仑破裂应力增大所引起的余滑来解释。余震进一步向南滑动也引发了余震，并在几个EW向冲击带中反复发生地震。我们将这些条纹解释为周围蠕变的标志，这可能表明断层力学的变化，并可能有构造起源，由假定的巨型逆冲波纹的流体诱导的破坏引起。巨型逆冲余震终止于外大陆楔形体中朝海正面棱柱下方，在速度增强条件下可能表现为地震。内部楔形物位于更远的陆地上，覆盖着巨型逆冲的地震孕育区。进一步向下倾斜，余震与大地上分解的两个主要余滑块反相关，并与库仑破裂应力增加部分相关，总体上表明了不均匀的摩擦行为。在约40-50公里深度的稀疏地震活动区之后，在约55-65公里深度发生了最深的板块界面余震，这些余震发生在倾角明显不同的两个群中。
We used data from >100 permanent and temporary seismic stations to investigate seismicity patterns related to the 1 April 2014 M8.1 Iquique earthquake in northern Chile. Applying a multistage automatic event location procedure to the seismic data, we detected and located ~19,000 foreshocks, aftershocks, and background seismicity for 1 month preceding and 9 months following the mainshock. Foreshocks skirt around the updip limit of the mainshock asperity; aftershocks occur mainly in two belts updip and downdip of it. The updip seismicity primarily locates in a zone of transitional friction on the megathrust and can be explained by preseismic stress loading due to slow‐slip processes and afterslip driven by increased Coulomb failure stress due to the mainshock and its largest aftershock. Afterslip further south also triggered aftershocks and repeating earthquakes in several EW striking streaks. We interpret the streaks as markers of surrounding creep that could indicate a change in fault mechanics and may have structural origin, caused by fluid‐induced failure along presumed megathrust corrugations. Megathrust aftershocks terminate updip below the seaward frontal prism in the outer continental wedge that probably behaves aseismically under velocity‐strengthening conditions. The inner wedge locates further landward overlying the megathrust's seismogenic zone. Further downdip, aftershocks anticorrelate with the two major afterslip patches resolved geodetically and partially correlate with increased Coulomb failure stress, overall indicating heterogeneous frictional behavior. A region of sparse seismicity at ~40‐ to 50‐km depth is followed by the deepest plate interface aftershocks at ~55‐ to 65‐km depth, which occur in two clusters of significantly different dip.