Dynamics of Slab Detachment

该项目是第一个使用全动态热对流数值模型(二维和三维球面几何)来探索板块拆离的项目，能够处理拆离过程及其地质表现。板块拆离(或剥离)可能发生在大陆或海脊与海沟碰撞等事件之后的俯冲带，这阻止了现有的板块有效地将未俯冲的岩石圈拉入地幔。然而，甚至连伴随着板片拆离的变形的最基本的方面也不被理解：例如，板片(顶面或底面)的位置拆离是否影响所产生的变形？板片拆离过程提供了一个独特的机会来约束上地幔的粘性结构，这是理解地幔对流和板块构造的流变学控制的一个重要方面。该项目的主要重点是描述板块拆离动力学对岩石圈、板块和上地幔热流变结构的依赖，包括由于年龄、成分、俯冲速度和几何形状而导致的岩石圈/板块结构横向变化的重要性。在广泛的2-D模型之后，将设计3-D模型来探索下加利福尼亚州南部的中新世板块拆离事件。专注于下加利福尼亚州/墨西哥西部地区的3-D模型是对当前NARS-BAJA地震实验(由边际计划资助)的补充，该实验将为高分辨率地震层析成像提供数据，可能照亮浅层法拉隆板块，并提供各向异性测量，以限制地幔中的区域流动。此外，该奖项将为研究生提供参与多学科研究所需的经验和背景，教授地球动力学建模方法以及各种地质观测的构造和地球物理影响。

This project is the first to explore slab detachment using fully-dynamic, numerical models of thermal convection, (in 2-D and 3-D spherical geometry), capable of treating both the process of detachment and its geological expression.Slab detachment (or break-off) may occur in subduction zones following an event such as continent or ridge collision with the trench, which prevents the existing slab from effectively pulling the unsubducted lithosphere into the mantle. However, even the most basic aspects of deformation accompanying slab detachment are not understood: for example, does the location detachmentinitiates in the slab (top or bottom surface) influence the resulting deformation?The slab detachment process provides a unique opportunity to place constraints on the upper mantle viscosity structure, one important aspect of understanding the rheologic controls on mantle convection and plate tectonics. The main focus of the project is to characterize the dependence of slab detachment dynamics on therheologic structure of the lithosphere, slab and upper mantle, including the importance of lateral changes in lithospheric/slab structure due to age, composition, subduction velocity and geometry. Broad 2-D modelling will be followed by 3-D models designed to explore the Miocene slab detachment event in southern Baja California.The 3-D models focused on the Baja California/western Mexico region are complementary to the current NARS-Baja seismic experiment (funded through the MARGINS program), which will provide the data for high resolution seismic tomographic images, possibly illuminating the shallow Farallon slab, and anisotropymeasurements providing constraints on regional flow in the mantle. In addition, this award will provide a graduate student with the experience and background necessary to participate in multi-disciplinary research by teaching both geodynamic modelling methods and the tectonic and geophysical implications of a variety ofgeological observations.