Seismic evidence for convection-driven motion of the North American plate
Seismic evidence for convection-driven motion of the North American plate
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DOI：
10.1038/nature05675
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发表时间：
2007-03
期刊：
影响因子：
64.8
通讯作者：
D. Eaton;A. Frederiksen
中科院分区：
文献类型：
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作者：
D. Eaton;A. Frederiksen
自板块构造发现以来，板块运动驱动力的相对重要性一直存在争议。这个问题的解决一直受到基底牵引力估计的不确定性的阻碍，基底牵引力控制着岩石圈板块和下伏地幔对流之间的耦合。热点轨迹保存了过去板块运动的记录，并提供了可以检查板块表面和下伏地幔区域之间相对运动的标记。在这里，我们表明，115-140百万年的大流星热点轨道在北美东部的表面表达是不一致的，相对于其位置在200公里的深度，从板块重建模型和地震层析成像研究推断。错位随着年龄的增长而增加，与板块底部相对于其表面的向西位移一致，平均速率为3.8 ± 1.8 mm yr-1。在这里，年龄限制的“穿刺点”，使直接估计的表面和底面的板块之间的相对运动。基底的相对位移大致平行于地震快轴和计算的地幔流，这表明软流圈流动可能使岩石圈龙骨变形，并对北美板块的这一部分施加驱动力。
Since the discovery of plate tectonics, the relative importance of driving forces of plate motion has been debated,. Resolution of this issue has been hindered by uncertainties in estimates of basal traction, which controls the coupling between lithospheric plates and underlying mantle convection,,. Hotspot tracks preserve records of past plate motion and provide markers with which the relative motion between a plate’s surface and underlying mantle regions may be examined. Here we show that the 115–140-Myr surface expression of the Great Meteor hotspot track in eastern North America is misaligned with respect to its location at 200 km depth, as inferred from plate-reconstruction models and seismic tomographic studies. The misalignment increases with age and is consistent with westward displacement of the base of the plate relative to its surface, at an average rate of 3.8 ± 1.8 mm yr-1. Here age-constrained ‘piercing points’ have enabled direct estimation of relative motion between the surface and underside of a plate. The relative displacement of the base is approximately parallel to seismic fast axes and calculated mantle flow, suggesting that asthenospheric flow may be deforming the lithospheric keel and exerting a driving force on this part of the North American plate.