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

地壳中的断层是如何演化的？1906年的旧金山大地震引发了地震科学的研究，自那以后的100年里，地质学家对断层如何积聚压力和相互作用有了很多了解。然而，断层行为仍然无法预测。了解活动断层的下一次革命将不仅仅是考虑单个断层，而是考虑整个三维断层系统。这个项目正在开发创新的计算机工具，以增强我们对故障系统演变的理解，同时也将聋人高中生纳入研究项目。本研究通过假设断层的演化使系统中的能量最小化来研究断层的系统演化；换句话说，故障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，断层系统的演化在三维计算机模型中进行了模拟。特别是，当构造环境发生变化时，断层系统是如何适应的？例如，在伸展构造环境中发育的断层在后期收缩下可能变形效率较低。计算机模型显示，在这样的构造移动中，一些断层重新激活，一些连接起来，一些新的、更有效的断层面发育起来。世界上许多地方都经历了地壳构造的变化。特别令人感兴趣的是，在过去的600万年里，南加州现今的断层系统是如何演变的。人口密集和活动断层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用桌面实验验证断层演化的模型预测。断层被放入一层厚厚的粘土中，然后被拉伸以模拟地球的变形。这些实验是由研究人员以及全国三所高中的聋哑教师和学生进行的。将失聪学生纳入项目可能：1)激发对地球科学的终身兴趣；2)激励失聪学生在大学里学习科学；3)提高学生的技术沟通技能；4)利用他们的空间可视化技能增强学生的能力；5)消除将地球科学视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空间认知技能，这对分析相互作用的三维断层面至关重要。事实上，地球科学家可以从聋人社区学习3D数据呈现的创新方法。

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.