Dynamics of Slab Detachment

该项目是第一个使用全动态的热对流数值模型（二维和三维球面几何）来探索板状拆离的项目，能够处理拆离过程及其地质表现。板块分离（或断裂）可能发生在俯冲带，发生在大陆或洋脊与海沟碰撞等事件之后，这阻止了现有板块有效地将未俯冲的岩石圈拉入地幔。然而，即使是伴随板分离的变形的最基本方面也不清楚：例如，在板（顶部或底部表面）中开始分离的位置是否影响所产生的变形？板块拆离过程提供了一个独特的机会来约束上地幔黏性结构，这是理解地幔对流和板块构造流变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、板块和上地幔流变结构的依赖关系，包括岩石圈/板块结构横向变化的重要性，这些变化是由年龄、成分、俯冲速度和几何形状引起的。广泛的2-D模型将在3-D模型之后，设计用于探索下加利福尼亚州南部中新世板块剥离事件。针对下加利福尼亚州/墨西哥西部地区的三维模型是对目前的NARS-Baja地震实验（由edge项目资助）的补充，后者将提供高分辨率地震层析成像数据，可能会照亮浅层Farallon板块，以及提供地幔区域流动约束的各向异性测量。此外，该奖项将通过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含义，为研究生提供参与多学科研究所需的经验和背景。

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.