Fast Fluid Movement in the Earth’s Outer Core from Seismic Observations and High Performance Computing

周莹 副教授

美国弗吉尼亚理工大学

2023.06.21（星期三）10:00，理科二号楼2821

报告摘要：

The solid inner core grows through crystallization of the liquid metallic outer core. This process releases latent heat as well as light elements, providing thermal and chemical buoyancy forces to drive the Earth’s geodynamo. Here we investigate temporal changes in the liquid outer core by measuring travel times of core-penetrating SKS waves produced by pairs of large earthquakes at close hypocenters. While the majority of the measurements do not require a change in the outer core at a decade time-scale, we observe SKS waves that propagate through the upper half of the outer core in the low latitude Pacific travel about one second faster at the time when the second earthquake occurred, about 20 years after the first earthquake. Based on hypocenter grid search and SPECFEM wave propagation simulations, we show that the double-differential travel time anomalies can not be explained by earthquake hypocenter differences but suggest about 1-1.5% increase in P-wave speed in the outer core in localized regions with a lateral radius of about 800 km. This wavespeed increase can be explained by 2–3% of density deficit, possibly associated with high concentration light elements in transient flows in the outer core, with a flow speed in the order of 40 km/year. This observation opens the possibility of monitoring fluid movement in the outer core using seismic data and high-performance computing. I will talk about computational resources at Virginia Tech, recent research projects and PhD opportunities.

报告人简介：

周莹，博士，美国弗吉尼亚理工大学副教授。1996 年毕业于浙江大学地球科学系，1999 年获得中科院地球 物理研究所硕士学位。 2005 年普林斯顿大学博士。2004-2006 年加州理工大学地震实验室博士后。 主要研 究方向有地震波的衍射成像，地球内部的波速异常，速度间断面，地震波的衰减结构以及相关的动力学分析。