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Broad depth range seismic imaging of the subducted Nazca Slab, North Chile

机译:智利北部纳斯卡俯冲板的宽深度地震成像

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In this paper, we present a compilation of modem seismic and seismological methods applied to image the subduction process in North Chile, South America. We use data from active and passive seismic experiments that were acquired within the framework of the German Collaborative Research Center SFB267 'Deformation Processes in the Andes'. The investigation area is located between 20degrees and 25degrees S and extends from the trench down to 100 kin. depth. In the depth range between the sea bottom and 15 km, we process an offshore seismic reflection profile using a recently developed velocity-model-independent stacking procedure. We find that the upper part of the subducting oceanic lithosphere in this depth range is characterized by a horst-and-graben structure. This structure supports an approximately 3 kin thick coupling zone between the plates, In the depth range between 15 and 45 km, we analyse the spatial distribution of aftershocks of the Antofagasta earthquake (1995). The aftershock hypocenters are concentrated in an approximately 3 km thick layer. Finally, in the depth range between 45 and 100 km, we apply Kirchhoff prestack depth migration to the onshore ANCORP profile. A double reflection zone is observed between 45 and 60 km depth, which may represent the upper and lower boundary of the subducted oceanic crust. Over the whole range down to more than 80-90 km depth, we obtain an image of the subducting slab. At that depth, the hypocenters of local earthquakes deviate significantly in the direction perpendicular to the slab face from the reflective parts of the slab. Consequently, our results yield a complete seismic image of the downgoing plate and the associated seismic coupling zone. (C) 2002 Published by Elsevier Science B.V. [References: 18]
机译:在本文中,我们提出了一种现代地震和地震学方法的汇编,用于对南美洲智利北部的俯冲过程进行成像。我们使用来自主动和被动地震实验的数据,这些数据是在德国合作研究中心SFB267“安第斯山脉的变形过程”的框架内获得的。调查区域位于南纬20度到25度之间,从海沟向下延伸到100 kin。深度。在海底和15 km之间的深度范围内,我们使用最近开发的与速度模型无关的叠加程序来处理海上地震反射剖面。我们发现,在该深度范围内俯冲的海洋岩石圈的上部具有霍尔斯特-格拉本结构的特征。该结构支撑了板块之间大约3 kin厚的耦合带。在15至45 km的深度范围内,我们分析了安托法加斯塔地震(1995)余震的空间分布。余震震源集中在约3 km厚的层中。最后,在45至100 km的深度范围内,我们将Kirchhoff叠前深度偏移应用于陆上ANCORP剖面。在45至60 km的深度之间观察到一个双反射带,这可能代表俯冲洋壳的上下边界。在整个深度超过80-90 km的范围内,我们获得了俯冲板的图像。在该深度处,局部地震的震源在垂直于板面的方向上偏离板的反射部分。因此,我们的结果产生了下倾板和相关地震耦合带的完整地震图像。 (C)2002由Elsevier Science B.V.出版[参考文献:18]

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