A narrowly spaced double‐seismic zone in the subducting Nazca plate
A narrowly spaced double‐seismic zone in the subducting Nazca plate
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俯冲纳斯卡板块中间隔狭窄的双地震带
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
F. Waldhauser
中科院分区：
文献类型：
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作者：
A. Rietbrock;F. Waldhauser
安第斯山脉中部以下(80-130公里)中深地震的高精度重新定位揭示了一个精细的双层瓦达蒂-贝尼奥夫带(WBZ)。地震活动的上、下带相隔约9公里，分别发生在大洋地壳顶部和大洋地幔最上层。对震源机制和波形相似性的分析表明，流体过程是导致事件的原因。洋壳中的地震发生在先前存在的正断层上，这是由于变质脱水造成的水力脆化，以及在狭窄的深度范围内连接两层的亚垂直断层。两层均以伸展断裂为主，表明板片拉力是本段纳斯卡板块最主要的应力来源，取代了可能的不弯曲力。
High‐precision relocations of intermediate‐depth earthquakes (80–130 km) below the Central Andes reveal a fine‐scale double‐layered Wadati‐Benioff zone (WBZ). Upper and lower band of seismicity are separated by about 9 km and occur at the top of the oceanic crust and in the uppermost oceanic mantle, respectively. Analysis of focal mechanisms and waveform similarities indicate that fluid processes are causing the events. Earthquakes in the oceanic crust occur on pre‐existing normal faults due to hydraulic embrittlement from metamorphic dehydration, and on subvertical faults that connect the two layers in a narrow depth range. Extensional faulting predominates in both layers, indicating that slab pull forces are the dominant stress source superseding possible unbending forces in this segment of the Nazca plate.