Mantle shear-wave tomography and the fate of subducted slabs
Mantle shear-wave tomography and the fate of subducted slabs
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DOI：
10.1098/rsta.2002.1077
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发表时间：
2002-11-15
期刊：
影响因子：
5
通讯作者：
Grand, SP
中科院分区：
文献类型：
--
作者：
Grand, SP
本文提出了一个新的地幔剪切速度三维变化的地震模型。该模型完全来自剪切体波旅行时间。分析中使用了多跳剪切波、岩芯反射波以及穿过岩芯的SKS和SKKS波。在这项研究中使用的数据集的一个独特的方面是使用体波，在地幔中的浅深度，其中一些是三重的。与其他全球剪切模式进行了比较。虽然相互竞争的模型显示出显著的差异，但大多数模型都有几个大规模的结构。高速异常多与俯冲带有关。在某些地区，异常仅延伸到下地幔浅层，而在其他地区，板状高速结构似乎延伸到地幔最深处。地幔底部显示出与俯冲带有关的长波高速带。在全球层析成像模型中看到的不均匀性很难用地幔流来解释，因为从一个俯冲带到另一个俯冲带的结构变化。对地震图像最简单的解释是，板块一般穿透到地幔最深处，尽管流动可能是零星的。板块下沉的中断可能与660 km的不连续性有关。
A new seismic model of the three-dimensional variation in shear velocity throughout the Earth's mantle is presented. The model is derived entirely from shear bodywave travel times. Multibounce shear waves, core-reflected waves and SKS and SKKS waves that travel through the core are used in the analysis. A unique aspect of the dataset used in this study is the use of bodywaves that turn at shallow depths in the mantle, some of which are triplicated. The new model is compared with other global shear models. Although competing models show significant variations, several large-scale structures are common to most of the models. The high-velocity anomalies are mostly associated with subduction zones. In some regions the anomalies only extend into the shallow lower mantle, whereas in other regions tabular high-velocity structures seem to extend to the deepest mantle. The base of the mantle shows long-wavelength high-velocity zones also associated with subduction zones. The heterogeneity seen in global tomography models is difficult to interpret in terms of mantle flow due to variations in structure from one subduction zone to another. The simplest interpretation of the seismic images is that slabs in general penetrate to the deepest mantle, although the flow is likely to be sporadic. The interruption in slab sinking is likely to be associated with the 660 km discontinuity.