Beyond elastic rebound: extracting permanent strain from interseismic deformation

GPS数据在研究构造板块边界方面的主要用途之一是了解断层运动的当前速率和了解断层如何相互作用。这种理解可以帮助我们更好地评估地震风险，因为它有助于我们更好地理解断层系统的长期行为。参与该项目的研究人员将试图调和两种模型，一种是表征单一断层的模型，另一种是着眼于整个板块边界的长期演化的模型。这项工作的结果对板块边界移动的速度以及断层周围的地面如何随时间变形具有重要意义。这项工作将使用两个例子，在台湾，另一个在南加州。比较和对比这两个领域将提高对地震过程的整体理解。拟议的研究目的是开发大地测量数据的动态模型，将传统的弹性模型扩展到包括永久变形。该方法是建立粘弹塑性边界元模型，在该模型中，变形的地壳受到远场应力和断层滑动的加载，而周围的地壳则响应于载荷而变形。他们将使用大地测量数据、从震源机制数据推断的应力状态以及地质和热年代学数据来约束变形模型。在台湾，他们将使用GPS衍生的水平和垂直速度场、全岛水准网络和整个地壳的应力方向来解决台湾造山过程中有关断层结构的几个关键悬而未决的问题。他们将测试几种深断裂几何模型和一种拟议的深部底侵过程，以抬升山脉的核心。模型结果将与低温热年代学进行比较。在南加州，这项研究将检验走滑断层系统的长期变形模型，以确定各种推动力(板块边界力、重力势能、地幔阻力)的相对贡献，并将预测的长期断层滑动速率与地质滑动速率估计进行比较。他们将专注于一个重要的突出问题，即变形部分作为断层外非弹性屈服分布通过地壳发生，而变形是由断层上的滑动调节的。

One of the main uses of GPS data in studying the boundaries of tectonic plates is to understand current rates for fault movements and understand how faults interact. This kind of understanding can all feed into a better assessment of earthquake hazards because it helps us better understand the longer term behavior of fault systems. The researchers in the project will try to reconcile two kinds of models, those that characterize single faults with those that look at long-term evolution of a full plate boundary. The results of this work have important implications for how fast plate boundaries are moving and how the ground around faults deforms over time. The work will use two examples, on in Taiwan, and the other in Southern California. Comparing and contrasting the two areas will improve overall understanding of earthquakes processes.The purpose of the proposed research is to develop dynamic models of geodetic data that extend traditional elastic models to include permanent deformation. The approach is to develop viscoelastic-plastic boundary element models in which the deforming crust is loaded by far-field stresses and faults slip and the surrounding crust deforms in response to the loads. They will employ geodetic data, stress state inferred from focal mechanism data, and geologic and thermochronologic data to constrain the deformation models. In Taiwan they will use the GPS-derived horizontal and vertical velocity fields, an island-wide leveling network, and stress orientations throughout the crust to address several key outstanding issues about the fault architecture responsible for mountain building processes in Taiwan. They will test several models of deep fault geometry and a proposed deep-seated underplating processfor uplifting the core of the mountain range. Model results will be compared with low-temperature thermochronology. In southern California the research will examine models of long-term deformation across the strike-slip fault system to determine the relative contributions of various pate-driving forces (plate boundary forces, gravitational potential energy, mantle drag) and compare predicted long-term fault slip rates with geologic slip rate estimates. They will focus on the important outstanding problem of the portion of deformation that occurs as off-fault inelastic yielding distribution through the crust versus deformation that is accommodated by slip on faults.