Collaborative Research: Constraining Fault Displacement Histories and Lithospheric Dynamics using Geology and Geophysics

这个项目的目标是提高我们的理解如何地壳规模的结构与岩石圈规模的动力学和现今的地壳应变场使用南部圣安德烈亚斯断层带作为一个天然实验室。 具体来说，研究集中在确定的时间尺度上的位移速率变化的各种故障组成的圣安德烈斯断层带附近的圣贝纳迪诺，加州。 一种新的建模技术的基础上的平滑样条理论正在开发中推断瞬时断层位移率从现有的位移率平均从大地测量和地质研究。 时变位移速率估计的条件下，总的位移跨越一组故障是保守的，通过时间。 初步结果表明，圣安德烈亚斯和圣哈辛托断层带的位移速率在百万年、十万年和一万年的时间尺度上有明显的变化。 尽管随着时间的推移变化很大，但现有数据与总流离失所率恒定的概念是一致的。 东加州剪切带断层的贡献也正在探索中。 圣哈辛托断层的诞生与圣安德烈亚斯断层中一个主要的限制性弯曲的发展相关。 瞬时位移速率估计表明，圣安德烈亚斯断层速率减慢了约80%，与圣哈辛托断层的形成一致。 这些断层的形成和位移速率的变化数据对岩石圈动力学有一定的意义。 该项目的一个重要部分是使用非线性二维和三维数值模型，包括脆性弹塑性和粘弹性流变学，以了解所观察到的位移速率变化的潜在动态过程。 目前正在利用数值试验来探索控制断裂带形成和演化的参数，包括评估地壳增厚的相对重要性、斜向断层段的正应力变化以及下地壳和上地幔的粘性强度。

The goal of this project is to improve our understanding of how crustal-scale structures relate to lithospheric-scale dynamics and present-day crustal strain fields using the southern San Andreas fault zone as a natural laboratory. Specifically, the research is concentrating on a determination of the time-scales over which displacement rates vary on the various faults composing the San Andreas fault zone near San Bernardino, California. A new modeling technique based on the theory of smoothing splines is being developed to infer instantaneous fault displacement rates from available displacement rate averages from geodetic and geological studies. Time-variable displacement rates are estimated subject to the condition that the total displacement across a set of faults is conserved through time. Preliminary results indicate appreciable variations in displacement rate for the San Andreas and San Jacinto fault zones on million, 100 thousand, and 10 thousand year time-scales. Despite large variations through time, existing data are consistent with the notion of a constant total displacement rate. The contribution of eastern California shear zone faults is also being explored. The birth of the San Jacinto fault correlates with the development of a major restraining bend in the San Andreas fault. Instantaneous displacement rate estimates indicate that the San Andreas fault rate slowed by some 80 percent coincident with the formation of the San Jacinto fault. These fault formation and displacement rate variation data have implications for lithospheric dynamics. An important part of this project is the use of nonlinear 2D and 3D numerical models that include brittle elastic-plastic and visco-elastic rheologies to understand possible dynamic processes underlying the observed displacement rate changes. Numerical experiments are being used to explore the parameters that control fault zone formation and evolution, including an assessment of the relative importance of crustal thickening, variations in normal stress on oblique fault segments, and the viscous strength of the lower crust and upper mantle.