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首页> 外文期刊>Geosphere >Geologic controls on up-dip and along-strike propagation of slip during subduction zone earthquakes from a high-resolution seismic reflection survey across the northern limit of slip duri...
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Geologic controls on up-dip and along-strike propagation of slip during subduction zone earthquakes from a high-resolution seismic reflection survey across the northern limit of slip duri...

机译：在俯冲区地震过程中，滑坡在悬垂区域地震期间，从北极极限的高分辨率地震反射调查的地震过程中的地质控制。

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A grid of closely spaced, high-resolution multichannel seismic (MCS) reflection profiles was acquired in May 2012 over the outer accretionary prism up dip from the patch of greatest slip during the 2010 M w 8.8 Maule earthquake (offshore Chile) to complement a natural-source seismic experiment designed to monitor the post-earthquake response of the outer accretionary prism. We describe the MCS data and discuss the implications for the response of the accretionary prism during the earthquake and for the long-term evolution of the margin. The most notable observation from the seismic reflection survey is a rapid north-to-south shift over a short distance from nearly total frontal accretion of the trench sediments to nearly total underthrusting of undeformed trench sediments that occurs near the northern edge of slip in the 2010 earthquake. Integrating our structural observations with other geological and geophysical observations, we conclude that sediment subduction beneath a shallow décollement is associated with propagation of slip to the trench during great earthquakes in this region. The lack of resolvable compressive deformation in the trench sediment along this segment of the margin indicates that the plate boundary here is very weak, which allowed the outer prism to shift seaward during the earthquake, driven by large slip down dip. The abrupt shift from sediment subduction to frontal accretion indicates a stepdown in the plate boundary fault, similar to the stepovers that commonly arrest slip propagation in strike-slip faults. We do not detect any variation along strike in the thickness or reflective character of the trench sediments adjacent to the change in deformation front structure. This change, however, is correlated with variations in the morphology and structure of the accretionary prism that extend as far as 40 km landward of the deformation front. We speculate that forearc structural heterogeneity is the result of subduction of an anomalously shallow or rough portion of plate that interacted with and deformed the overlying plate and is now deeply buried. This study highlights need for three-dimensional structural images to understand the interaction between geology and slip during subduction zone earthquakes.
机译：在2012年5月在2012年5月在2010年5月在2010年5月8日毛泽东（海上智利）期间，在2012年5月在2012年5月倾斜的浸渍浸入了自然的曲线 - 源地震实验，旨在监测外部增生棱镜的地震响应。我们描述了MCS数据，并讨论了地震期间对棱镜的响应的影响，以及余量的长期演变。从地震反射调查的最值得注意的观察是从沟槽沉积物的几乎全面的前距离距离距离的快速南到南迁移到几乎完全欠稳压的未变形的沟槽沉积物，在2010年的北边的北边边缘附近发生地震。与其他地质和地球物理观测相结合我们的结构观察，我们得出结论，浅层沉积物下方的沉积物俯冲与在该地区的大地震期间对沟槽的滑动繁殖相关。沿着该边缘段的沟槽沉积物中缺乏可分解的压缩变形表明，这里的板边界非常弱，这使得外棱镜在地震期间将海向后移动，由大滑倒下降驱动。从沉积物俯冲到正面吸收的突然转变表示板边界断层的降压，类似于逐步停滞在防滑断层中的滑动传播。我们没有检测到沟槽沉积物的厚度或反射特性沿着变形前结构的变化的变化的厚度或反射特性的任何变化。然而，这种变化与膨胀棱镜的形态和结构的变化相关联，该棱镜的变形棱镜延伸到变形前沿40公里。我们推测，前臂结构异质性是俯冲与覆盖板相互作用并变形的板的异常浅或粗糙部分的俯冲，现在深埋。本研究突出了三维结构图像需要了解地下地层地质和滑动之间的相互作用。

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