Finite Plate Model of Western United States Tectonics

该项目的目的是了解大陆如何变形，变形如何在空间上分布，以及十年尺度GPS导出的速度如何与长期地质断层滑动速率相关。美国西部的活动构造由有限数量的弹塑性岩石圈板块或块体表示，这些实体的角速度和内部应变率通过GPS速度、地震滑动矢量方位角和断层滑动率的反演来估计。该方法形式上考虑了地球的弹性变形，使得包括断层上的滑动速率的长期变形可以与可能主要是弹性的短期变形分开。块反演接口与有限元代码，使更现实的有限厚度板模型可以用来超越迄今为止使用的半空间近似。这项工作导致以下方面的改进：（1）可用于改进地震灾害模型的断层滑动速率估计，（2）了解大地测量和地质断层滑动速率之间的关系以及粘弹性和有限厚度板块模型的作用，（3）提供有关驱动机制信息的地壳块体旋转速率，以及（4）模拟大规模变形区域的方法。此外，该项目将导致更好地了解美国西部的构造，大陆一般如何变形，以及通常采样不同时间尺度的大地测量和地质数据如何相互关联。这项工作将使人们更好地了解美国西部的地震可能性，并进一步了解现代大地测量数据，如地球观测仪板块边界观测站收集的数据，将如何切实有助于绘制地震灾害风险图。

The purpose of this project is to understand how continents deform, how the deformation is spatially distributed, and how decade-scale GPS-derived velocities relate to long-term geologic fault slip rates. The active tectonics of the western United States is represented by a finite number of elastic-plastic, lithospheric plates, or blocks, and the angular velocities of and internal strain rates within those entities are estimated by inversion of GPS velocities, earthquake slip vector azimuths, and fault slip rates. The method formally takes into account the elastic deformation of the Earth so that the long-term deformation that includes the slip rates on faults can be separated from the short-term deformation that may be largely elastic. The block inversion is interfaced with a finite element code so that more realistic finite-thickness plate models can be used to go beyond the half-space approximations used to date. The work is leading to improvements in (1) estimates of fault slip rates that can be used to improve earthquake hazard models, (2) understanding of how geodetic and geologic fault slip rates are related and the roles of viscoelastic and finite-thickness plate models, (3) crustal block rotation rates that provide information about driving mechanisms, and (4) approaches to modeling large-scale deforming regions. Furthermore, this project will to lead to an improved understanding of the tectonics of the western United States, how continents deform in general, and how geodetic and geologic data, that commonly sample different time scales, are related. The work will lead to an increased understanding of earthquake potential in the western United States and will further understanding of how modern geodetic data, such as those to be collected by the EarthScope Plate Boundary Observatory, will contribute in a practical way to seismic hazard risk maps.