CAREER: Response of Fault Systems to Shifts in Tectonic Regime: Implications for the Evolution of and Present-Day Activity of Fault Systems in Southern California

地壳断层是如何演化的？ 自 1906 年旧金山地震引发地震科学研究以来的 100 年来，地质学家对断层如何累积应力以及如何相互作用有了很多了解。 然而，故障行为仍然无法预测。理解活动断层的下一次革命将不仅考虑单个断层，而且考虑整个三维断层系统。该项目正在开发创新的计算机工具，以增强我们对断层系统演化的理解，并将聋哑高中生纳入研究计划。这项研究通过假设断层演化以最小化系统中的能量来研究断层的系统演化；换句话说，断层系统沿着阻力最小的路径生长。通过评估与活动断层相关的工作，在三维计算机模型中模拟断层系统的演化。 特别是，当构造环境发生变化时，断层系统如何适应？ 例如，在伸展构造环境中发育的断层可能会在后来的收缩作用下低效变形。 计算机模型显示，在这种构造转变时，一些断层重新激活，一些断层连接起来，并且一些新的、更有效的断层面形成。 世界许多地区都经历了结构性转变。 特别令人感兴趣的是当今南加州的断层系统在过去 600 万年中是如何演变的。 密集的人口和活跃的断层作用的结合使得了解南加州的断层演化对于估计未来地震的潜在损害非常重要。该项目的一个重要组成部分是通过桌面实验验证断层演化的模型预测。 断层被放入厚厚的粘土层中，然后拉伸以模拟地球的变形。 这些实验由研究人员以及全国三所高中的聋哑教师和学生进行。 将聋哑学生纳入该项目可以：1）激发对地球科学的终生兴趣，2）激励聋哑学生在大学里追求科学，3）提高学生的技术沟通能力，4）利用他们的空间可视化技能增强学生的能力，5）消除地球科学作为一种健全职业的观点。聋哑学生使用美国手语，这是一种固有的空间语言。 空间语言的使用有望培养对于分析相互作用的三维断层表面至关重要的空间认知技能。事实上，地球科学家可以从聋人群体中学习呈现 3D 数据的创新方法。

How do faults in the Earth's crust evolve? In the 100 years since the 1906 San Francisco earthquake, which instigated the study of earthquake science, geologists have learned much about how faults accumulate stress and interact with one another. However, fault behavior still cannot be predicted. The next revolution in understanding active faulting will consider not just individual faults but entire systems of three-dimensional faults. This project is developing innovative computer tools that will enhance our understanding of fault system evolution and is also incorporating deaf high school students into the research program.This study investigates the systemic evolution of faults by assuming that faults evolve to minimize the energy in the system; in other words, fault systems grow along paths of least resistance. By assessing the work associated with active faulting, the evolution of fault systems is simulated in three-dimensional computer models. In particular, how do fault systems adapt when their tectonic setting changes? For example, faults that developed in an extensional tectonic setting might deform inefficiently under later contraction. The computer models show that upon such tectonic shifts, some faults reactivate, some link up and some new, more efficient fault surfaces develop. Many parts of the world have undergone tectonic shifts. Of particular interest is how the present-day fault systems in Southern California, evolved over the last 6 million years. The combination of dense population and active faulting makes understanding fault evolution in Southern California quite important for estimating potential damage from future earthquakes.An important component of this project is the validation of model predictions of fault evolution with table-top experiments. Faults are put into a thick layer of clay that is then stretched to simulate deformation of the Earth. The experiments are being performed by the researchers as well as deaf teachers and students at three high schools around the country. Incorporating deaf students into the project may: 1) motivate life-long interest in geoscience, 2) inspire deaf students to pursue science in college, 3) improve the technical communication skills of the students 4) empower students by utilizing their spatial visualization skills and 5) dispel views of geoscience as an able-bodied occupation. Deaf students use American Sign Language, an inherently spatial language. The use of spatial language is expected to foster spatial cognitive skills critical for analyzing interacting, three-dimensional fault surfaces. In fact, geoscientists may learn from the deaf community innovative approaches for presentation of 3D data.