Seismic imaging of the Cocos plate subduction zone system in central Mexico
Seismic imaging of the Cocos plate subduction zone system in central Mexico
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墨西哥中部科科斯板块俯冲带系统的地震成像
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
R. Clayton
中科院分区：
文献类型：
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作者：
Younghee Kim;M. Miller;F. Pearce;R. Clayton
使用墨西哥中部的中美洲俯冲实验（MASE）线的宽带数据，使用基于广义氡变换的迁移对墨西哥中部俯冲的科科斯板块和覆盖的大陆岩石圈进行成像。我们的图像提供了对相对年轻的海洋岩石圈俯冲过程及其在北美大陆下方复杂几何形状的深入了解。转换和反射相位图像显示了北美大陆岩石圈下方Cocos海洋岩石圈的完整水平构造底侵作用，清晰的图像显示了一个非常薄的低速洋壳（7-8公里），在阿卡普尔科以15-20度倾斜，然后从中美洲海沟大约300公里处倾斜。在更远的内陆，板块似乎突然从几乎水平的形状变成了在跨墨西哥火山带（TMVB）下方大约75度的陡峭倾斜几何形状。当板块在TMVB下方弯曲时，迁移图像描绘了从俯冲海洋莫霍面到距离海岸约230 km的大陆莫霍面的过渡，这两种过渡在以前的地震图像中都没有清楚地分辨出来。TMVB下方的深层地震结构在上地幔内约65-75 km处显示出显著的负不连续性（快到慢）。这一特征在弧下水平延伸（约100 km），可能描绘了一层积水部分熔体的顶部。
Broadband data from the Meso‐America Subduction Experiment (MASE) line in central Mexico were used to image the subducted Cocos plate and the overriding continental lithosphere beneath central Mexico using a generalized radon transform based migration. Our images provide insight into the process of subducting relatively young oceanic lithosphere and its complex geometry beneath continental North America. The converted and reverberated phase image shows complete horizontal tectonic underplating of the Cocos oceanic lithosphere beneath the North American continental lithosphere, with a clear image of a very thin low‐velocity oceanic crust (7–8 km) which dips at 15–20 degrees at Acapulco then flattens approximately 300 km from the Middle America Trench. Farther inland the slab then appears to abruptly change from nearly horizontal to a steeply dipping geometry of approximately 75 degrees underneath the Trans‐Mexican Volcanic Belt (TMVB). Where the slab bends underneath the TMVB, the migrated image depicts the transition from subducted oceanic Moho to continental Moho at ∼230 km from the coast, neither of which were clearly resolved in previous seismic images. The deeper seismic structure beneath the TMVB shows a prominent negative discontinuity (fast‐to‐slow) at ∼65–75 km within the upper mantle. This feature, which spans horizontally beneath the arc (∼100 km), may delineate the top of a layer of ponded partial melt.