Toomey DR, Wilcock WSD, Solomon SC, Hammond WC, Orcutt JA
D. R. Toomey and W. C. Hammond, Department of Geological Sciences, University of Oregon, Eugene, OR 97403, USA. W. S. D. Wilcock, School of Oceanography, University of Washington, Seattle, WA 98195, USA. S. C. Solomon, Department of Terrestrial.
Science. 1998 May 22;280(5367):1224-7. doi: 10.1126/science.280.5367.1224.
Relative travel time delays of teleseismic P and S waves, recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment, have been inverted tomographically for upper-mantle structure beneath the southern East Pacific Rise. A broad zone of low seismic velocities extends beneath the rise to depths of about 200 kilometers and is centered to the west of the spreading center. The magnitudes of the P and S wave anomalies require the presence of retained mantle melt; the melt fraction near the rise exceeds the fraction 300 kilometers off axis by as little as 1%. Seismic anisotropy, induced by mantle flow, is evident in the P wave delays at near-vertical incidence and is consistent with a half-width of mantle upwelling of about 100 km.
在“地幔电磁与层析成像（MELT）实验”期间记录的远震P波和S波的相对传播时间延迟，已通过层析成像反演得到东太平洋海隆南部下方上地幔结构。一个广阔的低地震波速带在海隆下方延伸至约200公里深处，并以扩张中心以西为中心。P波和S波异常的大小表明存在残留的地幔熔体；海隆附近的熔体分数比离轴300公里处的熔体分数仅高出1%。由地幔流动引起的地震各向异性在近垂直入射的P波延迟中很明显，并且与约100公里宽的地幔上涌半宽度一致。
