Investigating the nature and timing of development of the Eastern California shear zone (ECSZ) in southeastern California

太平洋板块和北美板块之间的边界包括圣安德烈亚斯断层和一个称为东加州剪切带的更广泛的变形区域，该剪切带包含活动和非活动部分。本计画调查不活跃的东加州剪切带的断层，以限制断层的时间尺度和样式。这些信息将有助于理解板块边界的结构性变窄和不活跃段的废弃，这对于限制加州南部地震断层的演变非常重要。该项目结合了实地研究、详细的断层分析和地质年代学，以研究在非活动段演化过程中变形的岩石。要做到这一点，该项目将包括一个团队的研究生，本科生和社区大学的学生从一个主要是西班牙裔人口谁将获得宝贵的经验，在进行科学和科学交流。学生还将参与当地地球科学活动的外联机会，与社区互动。横跨太平洋-北美板块边界的相对转换运动由圣安德烈亚斯断层系统提供，较小但相当大的部分发生在被称为东加州剪切带（ECSZ）的广泛分布变形区内。ECSZ可以被细分为一个活跃的部分，目前占20-25%的相对板块运动，和一个古ECSZ，今天基本上是不活跃的。本项目的目标是通过实地研究、结构分析和地质/热年代学应用于特征良好的熊峡谷砾岩（BCC）（与古ECSZ的演化同时代形成）来约束古ECSZ内变形的时间尺度和样式。火山灰层的透长石40 Ar/39 Ar年龄与BCC碎屑透长石40 Ar/39 Ar年龄的耦合将制约沉积的时间尺度。基底岩石的热年代学结合断层岩的结构和薄片分析将记录古ECSZ活动时应变场的变化，断层方解石的U-Pb定年将限制断层活动的时间尺度。记录这种有点神秘的早期历史是至关重要的了解结构狭窄的ECSZ成一个活跃的带和废弃的古ECSZ。该项目将资助研究生和本科生，他们将反映UTEP的大部分西班牙裔人口。学生将获得宝贵的经验，实地工作，结构分析，地质/热年代学，建模技术和科学交流。该奖项反映了NSF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。

The boundary between the Pacific and North American plates includes the San Andreas fault and a wider region of deformation called the Eastern California shear zone, which contains active and inactive segments. This project investigates faults in the inactive Eastern California shear zone to constrain the timescales and styles of faulting through time. This information will help to understand the structural narrowing of the plate boundary and abandonment of the inactive segment, which is important for constraining the evolution of earthquake-producing faults in southern California. This project combines field studies, detailed fault analysis, and geochronology to study rocks that were deformed during evolution of the inactive segment. To do this, the project will include a team of graduate, undergraduate, and community college students from a largely Hispanic population who will each gain valuable experience in conducting science and scientific communication. Students will also be involved with outreach opportunities at local earth science events to interact with the community. Relative transform motion across the Pacific-North America plate boundary is accommodated by the San Andreas fault system, with a lesser, but substantial, portion occurring within a broad zone of distributed deformation known as the Eastern California shear zone (ECSZ). The ECSZ can be subdivided into an active segment that currently takes up 20-25% of the relative plate motion, and a paleo-ECSZ that is largely inactive today. The goal of this project is to constrain the timescales and styles of deformation within the paleo-ECSZ through field studies, structural analysis, and geo/thermochronology applied to the well-characterized Bear Canyon conglomerate (BCC) that formed coeval with evolution of the paleo-ECSZ. 40Ar/39Ar sanidine ages on tephra layers coupled with detrital sanidine 40Ar/39Ar of the BCC will constraint timescales of deposition. Thermochronology of basement rocks coupled with structural and thin section analysis of fault rocks will document changing strain fields as the paleo-ECSZ became active, and U-Pb dating of fault calcite will constrain timescales of faulting. Documenting this somewhat cryptic earlier history is crucial for understanding structural narrowing of the ECSZ into an active belt and abandonment of the paleo-ECSZ. This project will fund graduate and undergraduate students who will reflect the largely Hispanic population of UTEP. Students will gain valuable experience with field work, structural analysis, geo/thermochronology, modeling techniques, and scientific communication. Outreach opportunities at local earth science events will be used to build relationships with the community and community college.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.