Imaging the lithosphere-asthenosphere boundary beneath the Pacific using SS waveform modeling
Imaging the lithosphere-asthenosphere boundary beneath the Pacific using SS waveform modeling
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DOI：
10.1029/2010jb008070
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发表时间：
2011-07-28
影响因子：
3.9
通讯作者：
Shearer, Peter M.
中科院分区：
文献类型：
--
作者：
Rychert, Catherine A.;Shearer, Peter M.
大洋岩石圈构成了地球大部分的构造板块，也可能是大陆岩石圈的组成部分。大洋岩石圈 - 软流圈边界的深度和性质对于我们理解构造板块的定义以及岩石圈的演化至关重要。尽管根据热传导冷却模型，大洋岩石圈随着年龄增长会冷却、增厚和下沉这一点已得到充分证实，但对于构造板块的这种相对简单的认识还没有被完全理解。古老（>7000万年）的海洋深度比预测的要浅。此外，对大洋岩石圈下边界进行精确成像已被证明具有挑战性。在这里，我们使用一种新方法，通过对17年地震数据中叠加的SS波形形状的变化进行建模，直接绘制出了一个可能是横跨太平洋板块的岩石圈 - 软流圈边界的地震不连续面的深度和性质。不连续面的深度从25千米到130千米不等，并且与沿着地幔流线距洋脊的距离相关。这意味着大洋岩石圈 - 软流圈边界的深度取决于下伏软流圈的温度，其由930℃的最佳拟合等温线定义，95%的置信区间为820 - 1020℃，尽管在一些位置观测到的清晰度意味着除了温度之外可能还需要一种机制。
Oceanic lithosphere constitutes the bulk of Earth's tectonic plates and also likely represents the building blocks of the continental lithosphere. The depth and nature of the oceanic lithosphere-asthenosphere boundary are central to our understanding of the definition of the tectonic plates and lithospheric evolution. Although it is well established that oceanic lithosphere cools, thickens, and subsides as it ages according to conductive cooling models, this relatively simple realization of the tectonic plates is not completely understood. Old (> 70 Ma) ocean depths are shallower than predicted. Furthermore, precise imaging of the lower boundary of the oceanic lithosphere has proven challenging. Here we directly map the depth and nature of a seismic discontinuity that is likely the lithosphere-asthenosphere boundary across the Pacific plate using a new method that models variations in the shapes of stacked SS waveforms from 17 years of seismic data. The depth to the discontinuity varies from 25 to 130 km and correlates with distance from the ridge along mantle flow lines. This implies that the depth of the oceanic lithosphere-asthenosphere boundary depends on the temperature of the underlying asthenosphere, defined by a best fitting isotherm at 930 degrees C with a 95% confidence region of 820-1020 degrees C, although the sharpness of the observations in some locations implies a mechanism besides temperature may also be required.