EAR-PF: Fault-rock trapped-charge and 4He/3He thermochronometry: new paleothermometers to assess scales and rates of fault slip

EAR-PF：断层岩石俘获电荷和 4He/3He 测温仪：用于评估断层滑动规模和速率的新型古温度计

• 批准号: 1952905
• 负责人: Margaret Odlum
• 金额: $ 17.4万
• 依托单位: Odlum, Margaret
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2024-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952905&HistoricalAwards=false
• 关键词: EAR; PF; Fault; rock; trapped

Dr. Margaret Odlum has been awarded the NSF EAR Postdoctoral Fellowship to carry out research as well as a professional development plan at Utah State University (USU) under the mentorship of Professors Alexis K Ault and Tammy Rittenour. The goal of the project is to develop new approaches to fingerprint past earthquakes in fault rocks. Pinpointing evidence of ancient seismicity is important for understanding earthquake processes and mechanics and building a more complete record of fault activity, which collectively inform hazard assessment in seismically active fault systems. Most of the energy during an earthquake is given off as heat, which imparts a thermal and/or chemical signature in fault rocks. Proposed research uses coupled luminescence properties of minerals and He isotope thermometry integrated with textural analysis to access the thermal record of earthquake events across the full range of seismic slip rates, as well as temporal and spatial scales to inform fault slip processes. Complementary age information provided by these methods will provide a more continuous record of deformation over historical to geological timescales which is essential to understand earthquake cycles in a particular fault. This research will be conducted on the Wasatch and Hurricane faults in Utah. These are young, seismically active faults that are adjacent to Utah’s two largest population centers along the Wasatch Front and in the Saint George region, respectively. New approaches developed here will create pathways for researchers to quantify the spectrum of fault slip behavior in other fault systems. Dr. Odlum’s professional development plan is aimed at growing STEM workforce and engaging women, an underrepresented group in Utah in STEM, in earthquake science research and geotechnical skill-building. A seismic hazards module developed in partnership with the Utah Geological Survey will impact students enrolled in the new USU GeoPaths program, and reach a wider undergraduate community by sharing the module with other universities located in the Intermountain Seismic Zone and Wasatch Front region, as well as online through the USU Geosciences webpage and GeoMinutes YouTube channel, thus extending the reach and impact of this work.The goal of this research is to develop new approaches to identify, quantify, and date frictional heating caused by seismic slip in the rock record across the full range of seismic slip rates (micrometers/sec to tens of meters/sec). Much (~90%) of the energy budget during an earthquake goes into work done overcoming frictional resistance and dissipates as heat. The magnitude of temperature rise across a fault is a function of slip velocity, material properties, and strain localization. Frictional heat, in turn, impacts these factors and the interplay between variables controls fault strength during the seismic cycle. Transient, elevated temperatures impart textural and/or geochemical signatures in fault rocks. This project will combine trapped-charge analysis on quartz and feldspar with hematite and apatite 4He/3He thermochronometry of fault surfaces and underlying host-rock to recover paleotemperatures associated with seismic slip. The seismically active Wasatch and Hurricane faults in Utah will be the first field sites for applying this novel approach. Both seismogenic normal faults have textural evidence of past coseismic frictional-heat, bulk hematite (U-Th)/He dates that reflect thermal resetting or mineralization during earthquake slip within the viable age range for trapped-charge thermochronometry (0.5 Ma), and pose seismic risk to large population centers in Utah. Coupled paleotemperature and textural information from fault surfaces will inform dynamic weakening mechanisms operative during coseismic slip and improve understanding of rheological changes to fault materials that accompany fault thermal evolution and in-situ earthquake mechanics and fault strength in the upper seismogenic zone. Complementary temporal information on fault slip from trapped-charge and 4He/3He thermochronometry will fill a critical temporal data gap between historical, geodetic, and paleo-seismic (1 - 10,000 years) and low-temperature thermochronometric (100,000 - 1,000,000 years) records of deformation, with direct applications to seismic hazards assessment. The new thermochronometric approach to extract coseismic fault temperatures and temporal constraints on deformation applied here is transferable to other fault systems, giving researchers new tools to access the record of fault slip across seismic slip rates.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Margaret Odlum博士获得了美国国家科学基金会EAR博士后奖学金，在美国犹他州立大学（USU）教授Alexis K Ault和Tammy Rittenour的指导下进行研究和专业发展计划。该项目的目标是开发新的方法来识别断层岩石中过去地震的指纹。精确定位古代地震活动的证据对于理解地震过程和力学以及建立更完整的断层活动记录非常重要，这些记录共同为地震活跃断层系统的危险评估提供信息。地震时的大部分能量以热的形式释放出来，这在断层岩石中产生了热和/或化学特征。拟议的研究利用矿物的耦合发光特性和He同位素测温与结构分析相结合，在地震滑动率的全范围内获取地震事件的热记录，以及时空尺度来了解断层滑动过程。这些方法提供的补充年龄信息将提供一个更连续的历史到地质时间尺度上的变形记录，这对于理解特定断层的地震周期是必不可少的。这项研究将在犹他州的瓦萨奇断层和飓风断层上进行。这些是年轻的、地震活跃的断层，分别位于犹他州两个最大的人口中心Wasatch Front和圣乔治地区。这里开发的新方法将为研究人员在其他断层系统中量化断层滑动行为谱创造途径。Odlum博士的专业发展计划旨在增加STEM劳动力，并吸引女性参与地震科学研究和岩土技术技能建设。在犹他州，女性在STEM领域的代表性不足。与犹他州地质调查局合作开发的地震危害模块将影响参加新USU地质路径计划的学生，并通过与位于山间地震带和Wasatch Front地区的其他大学共享该模块，以及通过USU地球科学网页和GeoMinutes YouTube频道在线分享该模块，从而扩大这项工作的范围和影响。这项研究的目标是开发新的方法，在整个地震滑动率范围内（微米/秒到几十米/秒），识别、量化和确定岩石记录中由地震滑动引起的摩擦加热。地震中大部分（约90%）的能量收支都用于克服摩擦阻力，并以热量的形式散失。断层上的温升幅度是滑移速度、材料特性和应变局部化的函数。摩擦热反过来又影响这些因素，而变量之间的相互作用控制着地震周期中的断层强度。短暂的、升高的温度赋予断层岩石的结构和/或地球化学特征。该项目将结合石英和长石的圈闭电荷分析与断层表面和下伏寄主岩的赤铁矿和磷灰石4He/3He热时测定，以恢复与地震滑动有关的古温度。犹他州地震活跃的瓦萨奇断层和飓风断层将是应用这种新方法的第一个现场。这两个发震正断层都有过去同震摩擦热的结构证据，在圈闭电荷热时测定（0.5 Ma）的可行年龄范围内，反映了地震滑动期间的热重置或矿化，并对犹他州的大型人口中心构成地震风险。来自断层表面的耦合古温度和结构信息将为同震滑动过程中的动态弱化机制提供信息，并提高对断层热演化过程中断层物质流变变化的理解，以及对上发震区地震力学和断层强度的理解。从圈闭断层和4He/3He热时学获得的断层滑动的补充时间信息将填补历史、大地测量和古地震（1 - 1万年）与低温热时学（10万- 100万年）变形记录之间的关键时间数据空白，并直接应用于地震灾害评估。新的热时计方法可以提取同震断层温度和变形的时间约束，并可应用于其他断层系统，为研究人员提供了新的工具来获取断层滑动记录。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Seismicity recorded in hematite fault mirrors in the Rio Grande rift

里奥格兰德裂谷赤铁矿断层镜记录的地震活动

• DOI: 10.1130/ges02426.1
• 发表时间: 2021
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: Odlum, M.L.;Ault, A.K.;Channer, M.A.;Calzolari, G.
• 通讯作者: Calzolari, G.

Shallow Rupture Propagation of Pleistocene Earthquakes Along the Hurricane Fault, UT, Revealed by Hematite (U‐Th)/He Thermochronometry and Textures

• DOI: 10.1029/2021gl094379
• 发表时间: 2021-08
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Madison P. Taylor;A. Ault;M. Odlum;D. Newell

Investigation of quartz luminescence properties in bedrock faults: Fault slip processes reduce trap depths, lifetimes, and sensitivity

基岩断层中石英发光特性的研究：断层滑动过程降低了圈闭深度、寿命和灵敏度

• DOI: 10.1016/j.radmeas.2022.106784
• 发表时间: 2022
• 期刊: Radiation Measurements
• 影响因子: 2
• 作者: Odlum, Margaret L.;Rittenour, Tammy;Ault, Alexis K.;Nelson, Michelle;Ramos, Evan J.
• 通讯作者: Ramos, Evan J.