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首页> 外文期刊>Physics of the Earth and Planetary Interiors: A Journal Devoted to Obsevational and Experimerntal Studies of the Chemistry and Physics of Planetary Interiors and Their Theoretical Interpretation >Anomalous seismicity in the lower crust of the Santiago Basin, Chile
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Anomalous seismicity in the lower crust of the Santiago Basin, Chile

机译：智利圣地亚哥盆地下地壳的异常地震活动

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摘要

In central Chile, intraplate, crustal seismicity is mostly constrained to the upper 20 km; nevertheless, sparse observations of earthquakes have been reported deeper, without a definitive explanation. In the lower crust of the Santiago Basin, located within a compressional, subduction environment, we have observed a series of events organized in two clusters. This work presents a detailed study of these earthquakes, recorded from November 2002 to April 2005, with depths from 28 to 36 km and nnagnitudes ranging from 2.8 to 4.3. Using a local network (composed of vertical short-periods, broadbands, and accelerometers) we performed a time and spectral waveform analysis to determine their exact location and certain source parameters: seismic moment, corner frequency, and seismic energy. We found that each cluster presents extremely well correlated waveforms, indicating that each event in the Cluster ruptures the same patch in the same fashion. Even more, we determined that representative events show a large apparent stress drop, releasing six times More energy than interplate events, for a given seismic moment. The most plausible interpretation seems to be a decollement between the crust and the mantle, where few (but Strong) asperities are located in a broader region that continuously creeps. We believe that this work will help improve our understanding of the processes involved in subduction zones, as well as the assessment of the Seismic Hazard for the Santiago Metropolitan Area.
机译：在智利中部，板内，地壳的地震活动主要被限制在上部20 km。但是，据报道，对地震的稀疏观测更加深入，没有明确的解释。在处于压缩俯冲环境中的圣地亚哥盆地下地壳中，我们观察到了一系列以两个星团组织的事件。这项工作提供了对这些地震的详细研究，记录了2002年11月至2005年4月的地震，深度为28至36 km，震级为2.8至4.3。使用本地网络（由垂直短周期，宽带和加速度计组成），我们进行了时间和频谱波形分析，以确定它们的确切位置和某些震源参数：地震矩，转折频率和地震能量。我们发现，每个簇呈现出非常相关的波形，表明簇中的每个事件都以相同的方式破裂相同的斑块。更重要的是，我们确定了在给定的地震时刻，代表性事件表现出较大的表观应力降，释放出的能量比板间事件多出六倍。最合理的解释似乎是地壳和地幔之间的挠曲，其中很少（但很强）的粗糙位于不断蠕变的较宽区域内。我们相信这项工作将有助于我们更好地了解俯冲带所涉及的过程，以及对圣地亚哥都市圈地震危险性的评估。

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