A ubiquitous low-velocity layer at the base of the mantle transition zone

作者：Shen, Xuzhang; Yuan, Xiaohui^*; Li, Xueqing

来源：Geophysical Research Letters, 2014, 41(3): 836-842.

DOI：10.1002/2013GL058918

• mantle discontinuity
• receiver function
• slant stack
• mineral phase transformation
• the 600 discontinuity
• the X-discontinuity

Global stacks of receiver functions clearly exhibit the upper mantle stratification. Besides the most prominent seismic discontinuities, such as the Moho and the 410 and 660km discontinuities, a negative discontinuity is detected at a depth of similar to 600km, indicating a low-velocity layer at the base of the mantle transition zone. The slant-slack technique helps to identify the primary conversions from the multiple reverberations. Presence of the negative 600km discontinuity underneath both continent and ocean island stations, where the crustal thickness significantly differs, also precludes the possible cause of crustal reverberations. We conclude that the negative 600km discontinuity could be a global feature, possibly resulted from accumulation of ancient subducted oceanic crust. The X-discontinuity at similar to 300km depth is also observed in our global stacks, which can be explained by the coesite-stishovite phase transformation.

• 出版日期2014-2-16
• 单位中国地震局兰州地震研究所