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

这项工作的目的是增进对大陆变形动力学的了解，这是“板块构造时代”尚未解决和争议很大的主要问题之一。两个端元模型占主导地位的场景。在第一种方法中，岩石圈被视为一组由有限变形区分隔的刚性“块体”，其运动由施加在块体边缘的力控制。第二种方法把岩石圈看作是一个粘性连续体，岩石圈的变形是由板块相对运动和岩石圈内重力势能梯度引起的浮力共同驱动的。因此，它是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有相当好的记载。该项目包括一个新的大地测量导出的速度和应变率场，覆盖整个大陆。这一速度场的一个关键特征是整个中亚东部从贝加尔湖以东向南到巽他地块的东向东南运动。这一特点是不能复制块模型的变形是完全由一个“刚性”的印度压头到亚洲岩石圈的碰撞驱动。考虑浮力和板块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。这项研究正在研究亚洲大陆变形的驱动力，特别强调了在GPS数据中观察到的东缘向东迁移，结合亚洲最新的GPS解和地质数据，确定整个大陆的完整运动学应变率和速度场，（2）计算GPE变化的贡献（使用岩石圈模型）和岩石圈底部的牵引力（使用从全球层析成像导出的地幔流模型），（3）利用运动学数据和由GPE梯度和基底牵引力产生的应力场来估计边界应力，并最终确定一组解释大地测量观测的一致的力。此外，剪切波分裂观测结合地面运动场被用作一个独立的估计，直接解决东亚下方的流动方向，以了解东向迁移的起源，这项工作的更广泛的影响是支持早期职业女性研究人员，支持和培训研究生，女本科生。

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.