Berkeley Seismological Laboratory, Berkeley, CA 94720, USA.
Science. 2013 Oct 11;342(6155):227-30. doi: 10.1126/science.1241514. Epub 2013 Sep 5.
Understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists. Using full-waveform seismic tomography, we imaged a pattern of horizontally elongated bands of low shear velocity, most prominent between 200 and 350 kilometers depth, which extends below the well-developed low-velocity zone. These quasi-periodic fingerlike structures of wavelength ~2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers. Below 400 kilometers depth, velocity structure is organized into fewer, undulating but vertically coherent, low-velocity plumelike features, which appear rooted in the lower mantle. This suggests the presence of a dynamic interplay between plate-driven flow in the low-velocity zone and active influx of low-rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer.
理解驱动板块运动的不同尺度对流之间的关系以及热点火山活动仍然让地球物理学家感到困惑。我们使用全波形地震层析成像技术，对水平拉长的低速剪切带模式进行成像，这些低速剪切带在 200 至 350 公里深处最为明显，延伸至发育良好的低速带下方。这些准周期性的指状结构，波长约为 2000 公里，与绝对板块运动方向平行排列，绵延数千公里。在 400 公里深度以下，速度结构组织成较少的、波动但垂直连贯的低速羽状物特征，这些特征似乎扎根于下地幔中。这表明，在低速带中由板块驱动的流动和来自深部地幔源的低刚性物质的活跃涌入之间存在着一种动态相互作用，这些物质在移动的上边界层下方被水平偏转。
