Collaborative Research: Quantifying the Dynamics of Asia Using GPS, Geologic and Shear-Wave Splitting Data, and Large-Scale Flow Models

这项工作旨在提高对大陆形变动力学的理解，大陆形变是“板块构造时代”尚未解决和高度争论的主要问题之一。两个终端成员模特主宰了现场。在第一种方法中，岩石圈被视为一组坚硬的“块体”，由有限的变形区隔开，它们的运动由施加在块体边缘的力控制。在第二种情况下，岩石圈被视为一个粘性连续体，变形受相对板块运动和岩石圈内重力势能(GPE)梯度产生的浮力的共同驱动。亚洲是地球表面最大的扩散形变区。因此，这是一个研究大陆如何以及为什么变形的天然实验室。亚洲的活动变形在地质学上得到了相当好的记录。该项目结合了一个新的大地测量得出的速度和应变率场，覆盖整个大陆。这个速度场的一个主要特征是整个中亚东部从贝加尔岛以东向南到舜达地块的自东向东南运动。块体模型不能再现这一特征，在块体模型中，变形完全是由“刚性的”印度压头撞击亚洲岩石圈所驱动的。考虑浮力和板间耦合的更全面的薄片模拟工作仍然不足以解释这一特征。这项研究正在研究导致亚洲大陆变形的驱动力，特别强调在GPS数据中观察到的东部边缘的东移，方法是(1)结合最新的GPS解和亚洲的地质数据来确定整个大陆的完整运动应变率和速度场，(2)计算GPE变化(使用岩石圈模型)和岩石圈底部的牵引力(使用来自全球层析成像的地幔流动模型)，(3)使用GPE梯度和基本牵引力产生的运动学数据和应力场来估计边界应力，并最终确定解释大地测量观测的一组一致的力。此外，剪切波分裂观测结合地表运动场被用作独立的估计，以直接求解东亚下方的流动方向，以了解东迁的起源。这项工作的更广泛影响包括支持早期职业女性研究人员，支持和培训一名研究生，以及一名女性本科生。

This work aims at improving the understanding of the dynamics of continental deformation, one of the major unresolved -- and highly debated -- issues of the "plate tectonics era". Two end-member models dominate the scene. In the first one, the lithosphere is treated as a set of rigid "blocks" separated by finite zones of deformation, whose motions are controlled by forces applied at the edges of the blocks. In the second one, the lithosphere is treated as a viscous continuum and deformation is driven by both relative plate motions and buoyancy forces resulting from gravitational potential energy (GPE) gradients within the lithosphere.Asia is the largest zone of diffuse deformation on the surface of the Earth. As such, it is a natural laboratory to study how and why continents deform. Active deformation in Asia is fairly well documented geologically. This project incorporates a new geodetically-derived velocity and strain rate field that covers the entire continent. A key feature of this velocity field is the east- to southeastward motion of the entire eastern portion of central Asia from east of Baikal south to the Sunda block. This feature is not reproduced by block models where deformation is solely driven by the collision of a "rigid" Indian indenter into the Asian lithosphere. More comprehensive thin sheet modeling efforts that account for buoyancy forces and inter-plate coupling, are still not sufficient to explain this feature.This study is examining the driving forces responsible for continental deformation in Asia, with a particular emphasis on the eastward migration of the eastern margin observed in the GPS data by (1) combining the most recent GPS solutions and geologic data in Asia to determine a complete kinematic strain rate and velocity field over the entire continent, (2) computing the contribution of GPE variations (using lithospheric models) and of tractions at the base of the lithosphere (using mantle flow models derived from global tomography), (3) using the kinematic data and stress fields resulting from GPE gradients and basal traction to estimate boundary stresses and, eventually, determining a consistent set of forces that explain the geodetic observations. Additionally, shear-wave splitting observations in conjunction with the surface kinematic field are being used as an independent estimate, to directly solve for the direction of flow beneath East Asia in order to understand the origin of the eastward migration.Among the broader impacts of this work are support for an early career female researchers, support and training of a graduate student, and a female undergraduate.