地球系统科学论坛第689期

应澳门新莆京app9817曹毅教授和章军锋教授的邀请，同济大学“百人”特聘研究员马知途博士将来我校进行学术交流和访问。

报告时间：12月25日（星期三） 下午14:00‒15:30

报告地点：主楼412

报告题目：

大洋上地幔内部由脱水层控制的小尺度对流——来自海底地形和瑞利面波相速度的证据

Evidence for dehydration-modulated small-scale convection in the oceanic upper mantle from seafloor bathymetry and Rayleigh wave phase velocity

报告人学术简介：

马知途博士2008年本科毕业于北京大学。2015年于美国加州大学圣迭戈分校Scripps海洋研究所，获地球科学博士学位。2015年在布朗大学地球、环境与行星科学系从事博士后研究。2019年在哈佛大学地球和行星科学系任研究助理。2019年7月加入同济大学，现为同济大学青年百人、研究员。主要从事天然地震与地球动力学方面的研究。到目前为止，取得的主要创新研究成果包括：（1）全球岩石圈地震波速度的高精度成像；（2）大洋岩石圈演化；（3）全球岩石圈地震波衰减结构成像和地震波各向异性。共计在EPSL、JGR、GJI等国际学术期刊发表论文11篇（第一作者6篇）。

报告内容简介：

It is well established that the evolution of oceanic lithosphere departs from the predictions of the half-space cooling model (HSC). Understanding the magnitude, spatial distribution and physical origin of this departure is fundamental to our understanding of plate tectonics and the Earth’s thermal evolution. Here we analyze Rayleigh wave phase velocities and seafloor topography separately along spreading-history trajectories, which track each piece of seafloor since its formation at the mid-ocean ridge, in the Pacific and the Atlantic basins. We identify the age along each trajectory at which HSC fails to satisfy the observations. Bathymetry and seismic velocity yield consistent results on whether or not HSC gives a statistically better fit to the observations than the plate cooling model at 80% of the locations we examine. Locations of HSC failure identified by velocity but not topography overlap with SS precursor detections in the Pacific, suggesting partial melting at these locations. For the locations where the two data sets agree, in the Atlantic the probability of HSC failure is correlated with the axial depth of the present-day ridge. Along trajectories for which the present-day ridge is shallow (deep), HSC failure occurs later (earlier). A similar dependence in the Pacific is difficult to observe since both ridge depth and HSC failure age vary little. We show that the patterns of HSC failure are best explained by small-scale convection in the oceanic upper mantle for which the onset time is governed by rheological stratification created by partial melting at the ridge.

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澳门新莆京app9817

GPMR国家重点实验室

2019年11月