Kinematic and Dynamic Models of Actively Deforming Lithosphere of the Western US

随着地球观测站提供的全球定位系统在美国西部的扩展，地球动力学家准备在我们对岩石圈变形过程的理解方面取得快速进展。作为贡献，我们正在开发新的方法来模拟岩石圈的变形，并将模型预测与地表运动的GPS测量进行比较。我们的方法是共同开发美国西部岩石圈变形的运动学和动力学模型，以解决关于岩石圈变形的一系列长期存在的问题，包括：1.美国西部的变形方式是什么？2.各种驱动力对岩石圈变形的相对影响是什么？3.岩石圈的流变性是什么？流变性是如何随深度变化的？4.岩石圈变形是自驱动的，并与地幔流动脱钩吗？5.沿断层滑动在哪里，地震和地震？以及，6.断层通过岩石圈中的弹性和粘性过程传递载荷在多大程度上相互作用？我们正在开发长期和地震间变形的运动学模型，该模型将用于推断岩石圈的粘性结构、断层滑动速率、地震间断层蠕动的分布和岩石圈块体运动。为了做到这一点，我们正在构建3D地震周期模型，该模型由弹性裂解圈中的断层组成，该裂解圈覆盖在分层的粘性塑料圈上。我们正在研究地幔和地壳深断裂的地震后松弛过程在空间和时间上可能在GPS地震间变形测量中明显的程度，以及这些过程对我们估计的断层滑移率的影响程度。我们还超越了纯粹的运动学模型，开发了长期岩石圈变形的薄板弹塑性模型，在该模型中，断层在远场板块驱动力、重力势能变化引起的内体力和基底牵引力的响应下滑动。将这些长期运动的预测与我们的震间形变模型和GPS观测相结合，我们正试图推断各种驱动力对岩石圈变形的相对贡献。

With the recent expansion of the GPS network in the western US provided by the PBO component of Earthscope, geodynamicists are poised to make rapid progress in our understanding of the processes by which the lithosphere deforms.As a contribution, we are developing new methods for modeling the deformation of the lithosphere and comparing model predictions to GPS measurements of surface motions. Our approach is to jointly develop kinematic and dynamic models of lithosphere deformation in the western US to address a series of long-standing problems about how the lithosphere deforms including: 1. What is the mode of deformation in the western US? 2. What is the relative influence of various driving forces on lithosphere deformation? 3. What is the rheology of the lithosphere and how does rheology change with depth? 4. Is lithosphere deformation self-driving and decoupled from mantle flow? 5. Where is slip along faults aseismic and seismic? And, 6. To what extent do faults interact mechanically by transfer of loads through elastic and viscous processes in the lithosphere?We are developing kinematic models of long-term and interseismic deformation that will be used to infer the viscosity structure of the lithosphere, fault slip rates, distribution of interseismic fault creep, and lithospheric block motions. To do this we are constructing 3D earthquake cycle models consisting of faults in an elastic schizosphere overlying a layered viscous plastosphere. We are examining the extent in space and time to which postseismic relaxation processes in the mantle and on deep crustal faults might be evident in GPS measurements of interseismic deformation and to what extent these processes influence our estimates of fault slip rates. We are also moving beyond purely kinematic models and developing thin-plate elasto-plastic models of long-term lithosphere deformation in which faults slide in response to far-field plate driving forces, internal body forces due to variations in gravitational potential energy, and basal tractions. Combining these predictions of long-term motions with our interseismic deformation models and GPS observations, we are trying to infer the relative contributions of the various driving forces to lithosphere deformation.