High-resolution relocation and mechanism of aftershocks of the 2007 Tocopilla (Chile) earthquake
High-resolution relocation and mechanism of aftershocks of the 2007 Tocopilla (Chile) earthquake
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2007年托科皮亚（智利）地震的高分辨率重定位和余震机制
DOI：
10.1093/gji/ggt163
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发表时间：
2007
影响因子：
2.8
通讯作者：
R. Madariaga
中科院分区：
文献类型：
--
作者：
Fuenzalida;B. Schurr;M. Lancieri;M. Sobiesiak;R. Madariaga
我们详细研究了2007年11月14日智利北部托科皮亚Mw7.7地震的余震分布。这次地震破坏了智利北部裂隙南端发震带的下部，该地区在 1877 年发生了最后一次大逆冲地震。托科皮亚的余震分几个步骤发生：第一天它们位于同震破裂带内的海岸沿线。第二天之后，他们向梅希约内斯半岛附近的海洋区域扩展。最终在12月，它们集中在南部，靠近2007年12月16日米奇拉中深度地震的未来破裂带。余震序列由永久IPOC（智利综合板块边界观测站）网络和主事件后两周安装的临时工作组网络记录。总共识别了 1238 个事件，并且直接从地震图中读取地震到达时间。最初，我们使用单事件过程定位这些事件，然后使用双差法和互相关技术重新定位它们，以测量余震群的时间差。我们测试了一维速度模型和考虑了俯冲纳斯卡板块存在的二维速度模型。搬迁显着缩小了余震分布的宽度：在内陆地区，余震成像的板块界面厚度小于2 km。这两个速度模型对于海岸下方的地震给出了相似的结果，对于靠近海沟的事件给出了更大的差异。余震成像的表面长度为 160 公里。它从破裂带北部的30公里深度延伸至50公里；梅希约内斯半岛附近 5 至 55 公里深度之间。我们观察到俯冲界面倾角在 30 公里深度处从 18° 变化到 24°。我们认为倾角的这种变化与主事件破裂带的上限密切相关。我们还研究了余震的震源机制，大部分都是像主震一样的逆冲事件。随着余震活动明显减弱，2007年12月13日，梅希约内斯半岛近海发生ML6.1事件，地震活动重新活跃。三天后，Mw6.8 米奇拉板内地震导致一条几乎垂直的断层因板片推挤机制而破裂。这次事件的余震位置定义了一个深度约 11 公里的平面区域，位于俯冲界面的正下方。
We study the distribution of the aftershocks of TocopillaMw7.7 earthquake of 2007 November 14 in northern Chile in detail. This earthquake broke the lower part of the seismogenic zone at the southern end of the Northern Chile gap, a region that had its last megathrust earthquake in 1877. The aftershocks of Tocopilla occurred in several steps: the first day they were located along the coast inside the co-seismic rupture zone. After the second day they extended ocean-wards near the Mejillones peninsula. Finally in December they concentrated in the South near the future rupture zone of the Michilla intermediate depth earthquake of 2007 December 16. The aftershock sequence was recorded by the permanent IPOC (Integrated Plate Boundary Observatory in Chile) network and the temporary task force network installed 2 weeks after the main event. A total of 1238 events were identified and the seismic arrival times were directly read from seismograms. Initially we located these events using a single event procedure and then we relocated them using the double-difference method and a cross-correlation technique to measure time differences for clusters of aftershocks. We tested a 1-D velocity model and a 2-D one that takes into account the presence of the subducted Nazca Plate. Relocation significantly reduced the width of the aftershock distribution: in the inland area, the plate interface imaged by the aftershocks is thinner than 2 km. The two velocity models give similar results for earthquakes under the coast and a larger difference for events closer to the trench. The surface imaged by the aftershocks had a length of 160 km. It extends from 30 to 50 km depth in the northern part of the rupture zone; and between 5 and 55 km depth near the Mejillones peninsula. We observed a change in the dip angle of the subduction interface from 18° to 24° at a depth of 30 km. We propose that this change in dip is closely associated with the upper limit of the rupture zone of the main event. We also studied the focal mechanisms of the aftershocks, most of them were thrust events like the mainshock. As the aftershock activity was significantly reduced, on 2007 December 13, anML6.1 event occurred offshore of the Mejillones peninsula reactivating the seismicity. Three days later the Michilla intraslab earthquake ofMw6.8 ruptured an almost vertical fault with slab-push mechanism. The aftershocks locations of this event define a planar zone about 11 km in depth, situated right bellow the subduction interface.
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作者：
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影响因子：
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作者：
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DOI：
10.1029/jb094ib01p00665
发表时间：
1989-01-10
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS
影响因子：
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作者：
CIFUENTES, IL
通讯作者：
CIFUENTES, IL