Contributions of Ductile Shear Zones to Postseismic Deformation: Mechanical Advances and Data Assimilation

地震后经常发生的快速无震形变为了解地壳的力学行为提供了一个自然机会。记录地震后变形的大地测量数据集在过去几年中变得更加丰富和详细，但对这些数据集的许多研究仅限于记录一种特定的机制与观测数据“一致”。被认为是负责过程的各种候选机制证明了震后变形在地球动力学中的重要性，但也证明了我们目前对这一现象缺乏了解。拟议的研究将通过数据同化算法将能够同时考虑多种流变行为的建模框架与大地测量观测相结合。这种方法将确定与数据一致的过程范围，并排除其他过程，直接从大地测量数据限制地壳的流变性。将建立剪切带形成和演化与发震断层相耦合的模型，以解决震后形变的来源是分布的还是局部的。拟议的研究将有助于了解地壳动力学过程的基本知识，并有助于我们评估它们对地震灾害的贡献。对剪切带形成的更好的理解将对构造地质学和机械工程产生影响，在这些领域，本土化是一个永久的问题。这项工作的数据同化方面将有助于引入一种广泛成功的科学方法来解决断层力学问题。该项目代表了调查人员互补的研究领域的合并，一个是地球动力学，另一个是大地测量和数据同化。

The rapid aseismic deformation that often follows earthquakes provides a natural opportunity to learn about the mechanical behavior of the Earth's crust. Geodetic data sets documenting postseismic deformation have become much more plentiful and detailed in the last few years, yet many studies of these data sets have been limited to documenting that a particular mechanism "is consistent with" the observed data. The wide variety of candidate mechanisms that have been proposed as the responsible process testifies to the importance of postseismic deformation in geodynamics, but also to our current lack of understanding of this phenomenon. The proposed study will combine a modeling framework that can simultaneously consider multiple rheological behaviors with the geodetic observations through a data assimilation algorithm. This approach, will identify the range of processes consistent with the data and rule out others, constraining the rheology of the crust directly from geodetic data. Models of shear zone formation and evolution coupled with a seismogenic fault will be developed to address whether the source of postseismic deformation is distributed or localized.The proposed study will contribute to basic knowledge of dynamical processes in the Earth's crust and to our ability to evaluate their contribution to earthquake hazards. The improved understanding of shear zone formation will have implications for structural geology and mechanical engineering, where localization is a permanent concern. The data assimilation aspect of this work will help introduce a widely successful scientific approach to fault mechanics problems. The project represents the merging of the complementary research fields of the investigators, geodynamics for one, and geodesy and data assimilation for the other.--