CAREER: Thermochronometric and textural signatures of fault damage zones and stimulating middle school student interest in earthquake science

地震在断层表面和裸露的断层岩石上产生热量，从而提供了过去地震的温度记录。记录地震活跃断裂带中纳米到微地震化石产生的温度和结构，有可能改变我们对地震周期中热在断层强度中的作用的理解，以及我们重建地震百万年历史的能力，从而完善现代地震危害分析。该项目开发了一种新的方法，通过实地观测、纳米到微观尺度的断层表面表征、高空间分辨率断层岩石低温热年代学和新的高速、赤铁矿变形实验来模拟实验室地震，来识别和量化犹他州瓦萨奇断裂带现有断层表面上过去地震产生的摩擦热。这项职业资助的研究和教育部分通过提供从中学到博士后研究人员的多个学术水平的指导机会来推进预期的社会成果，旨在招募、培训和准备多样化的STEM（科学、技术、工程和数学）劳动力。该项目将支持一名女性早期职业科学家、一名博士后、两名研究生和四名本科生研究助理。该奖项支持的教育计划为位于地震活跃的瓦萨奇断裂带阴影下的农村社区的300多名中学生、教师和他们的父母提供了实地和实验室教育和研究经验。在这个项目中产生的教育活动模块将用于吸引瓦萨奇前线其他地方的中学生。该教育计划将在中学生人生的关键时刻塑造和发展他们的STEM身份。这是塑造下一代STEM劳动力的基础，并增加了学生在高中、大学和研究生院学习STEM课程的可能性。自然和实验断层的结构、参数和古温度可以整合到犹他州地质调查局发布的危险地图的构建中。对学生、教师和家长进行断层、地震和地质灾害的教育，将使利益相关者了解这些报告及其周围环境，以及他们面临的重大地震灾害。破译断层损伤带微震活动记录对于理解断层动力减弱、地震破裂和传播、复发间隔和地震自相似性等过程的原位物理意义至关重要。这项CAREER资助涉及一项跨学科研究和教育计划，旨在记录“镜像”或高光、光反射赤铁矿和二氧化硅滑动表面的古温度，以了解地震周期中的变形机制和断层强度演化。这些表面被假设为保持瞬时的高温，从而产生微地震的纹理和热时指纹。UT Wasatch断层下盘损伤带的天然断层岩是一个理想的研究和教育实验室，将与新型旋转剪切实验中产生的赤铁矿表面进行比较。研究阶段包括：镜面赤铁矿和硅包覆断层的现场表征；高速旋转剪切实验，记录赤铁矿摩擦、温度、微观结构和氦（He）损失；用原子力显微镜、聚焦离子束扫描电子显微镜和透射电子显微镜对自然和实验样品进行纳米到微观尺度的表征；采用赤铁矿（铀钍）/氦（He）、磷灰石He和磷灰石裂变径迹测年的高空间分辨率低温热时测定法；并综合自然和实验断层面观测。本文采用的赤铁矿He、磷灰石He和磷灰石裂变径迹热时计策略反映了破译复杂时空热重置特征的新方法。结合显微结构并与实验结果进行对比，这些断层原位古温标直接反映了赤铁矿和硅石断层闪热等潜在的动态弱化机制。综合教育计划采用基于地点和研究的实地和实验室学习活动，并与榜样持续接触，以促进中学生对地震科学和STEM的兴趣，并向准备不足和服务不足的人群通报相关的地震危害。该五年计划开发并使用这些学习模块，用于5- 6年级的教育，并在位于地震活跃的瓦萨奇断层带阴影下的农村社区开展教师讲习班。教育活动反映了项目研究活动，在学生形成潜在STEM身份的关键年龄为他们提供真正的科学体验。

Earthquakes generate heat on fault surfaces and exposed fault rocks that provide a temperature record of past earthquakes. Documenting temperatures and textures produced by fossil nano- to micro-earthquakes in seismically active fault zones has the potential to transform our understanding of the role of heat in fault strength during the seismic cycle and our ability to reconstruct the million-year history of earthquakes that refine modern seismic hazard analysis. This project develops a new approach for identifying and quantifying friction-generated heat from past earthquakes on now exposed fault surfaces in the Wasatch fault zone of Utah with field observations, nano- to microscale fault surface characterization, high-spatial resolution fault rock low-temperature thermochronology, and novel high-velocity, hematite deformation experiments to simulate laboratory earthquakes. The research and education components of this CAREER grant advance desired societal outcomes by offering mentoring opportunities at multiple academic levels from middle school through postdoctoral researcher designed to recruit, train, and prepare a diverse STEM (science, technology, engineering and mathematics) workforce. The project will support a female, early career scientist, a postdoctoral fellow, two graduate students, and four undergraduate research assistants. The education plan supported by this award provides field and laboratory education and research experiences for over 300 middle school students, teachers, and their parents in a rural community located in the shadow of the seismically-active Wasatch fault zone. Education activity modules produced during this project will used to engage middle school students elsewhere along the Wasatch front. The education plan will shape and develop middle school students' STEM identities at a critical time in their lives. This is fundamental for shaping future generation of STEM workforce and increases the likelihood that students will engage with STEM courses in high school, college, and graduate school. Natural and experimental fault textures, parameters, and paleotemperatures can be integrated into construction of hazard maps published by the Utah Geological Survey. Education of students, teachers, and parents about faults, earthquakes, and geohazards will enable stakeholders to understand these reports, their surroundings, and the significant seismic hazards they face.Deciphering the fault damage zone record of microseismicity is critical for understanding in situ physics of processes promoting fault dynamic weakening, earthquake rupture and propagation, recurrence intervals, and earthquake self-similarity. This CAREER grant involves a transdisciplinary research and education plan to document paleotemperatures on 'mirrored'or high gloss, light reflective hematite and silica slip surfaces to understand deformation mechanisms and fault strength evolution during the seismic cycle. These surfaces are hypothesized to preserve transient, elevated temperatures that yield textural and thermochronometric fingerprints of microearthquakes. Natural fault rocks in the Wasatch fault footwall damage zone, UT, are an ideal research and education laboratory and will be compared with hematite surfaces produced in novel rotary-shear experiments. Research phases include: field characterization of mirrored hematite and silica-coated faults; high-velocity, rotary-shear experiments to document hematite friction, temperature, microstructure, and helium (He) loss; nano- to micro-scale characterization of natural and experimental samples with atomic force microscopy, focused ion beam-scanning electron, and transmission electron microscopy; high-spatial resolution, low-temperature thermochronometry using hematite (Uranium-Thorium)/Helium (He), apatite He, and apatite fission-track dating; and synthesis of natural and experimental fault surface observations. Hematite He, apatite He, and apatite fission track thermochronometry strategies employed here reflect new approaches to decipher complex spatial and temporal thermal-resetting signatures. When coupled with microtextures and compared with experimental results, these in situ fault paleotemperatures proxies bear directly on potential hematite and silica fault dynamic weakening mechanisms such as flash heating of asperities. The integrated education plan applies place-based and research-based field and lab learning activities and sustained engagement with role models to facilitate middle school student interest in earthquake science and STEM, and inform an underprepared and underserved population about relevant seismic hazards. The 5-year plan develops and uses these learning modules for 5th-6th grade education along with teacher workshops in a rural community situated in the shadow of the seismically-active Wasatch fault zone. Education activities mirror project research activities to provide students experiences doing real science at a critical age when they are forming their potential STEM identities.