CAREER: Experimental investigation of deformation and slip behaviors of subduction megathrust rocks

毁灭性的地震和海啸在俯冲带反复发生，大地震事件之间的时间间隔从几十年到几百年不等。长期的国际合作研究和教育项目对于提高对震源物理的理解和将过去的知识传递给后代是必要的。为了进一步了解大型逆冲板块边界断层的变形和滑动行为以及俯冲带地震的物理性质，本项目涉及在板块边界断层预计的高压和高温条件下对天然断层岩石进行创新性变形和摩擦实验。为了扩大学生在实验岩石变形和俯冲带地震和海啸灾害方面的学习机会，首席研究员开发了新的教育计划，包括高级顶点课程，研究生和地球科学和工程早期职业科学家的培训课程，以及一次国际实地考察，将教育学生俯冲带地震和海啸以及减轻自然灾害的危害。该教育计划旨在提供岩石变形的动手实验经验和对俯冲带地震的见解。通过这些项目，下一代研究人员将接受培训，以促进在构造、地球动力学和工程问题上的跨学科和国际合作，并将发现和减轻自然灾害的成果传递给子孙后代。根据大量的地球物理和地质观测，包括低地震速度、高反射棱镜楔锥角和脉状构造等，推断出沿大逆冲板块边界断层发育高孔隙流体压力，从而导致断层强度低。该项目将验证低有效应力下的变形和滑动行为可能控制沿大型逆冲板块边界断层观察到的滑动事件和地震频谱的假设。对天然大逆冲断层岩进行了控制孔隙压力下的真三轴压缩试验、常规三轴拉伸试验和三轴摩擦试验。通过控制孔隙压力的大小和加压速率，可以在一定的加载路径和加载速率下获得较低的有效压力。该系列实验将记录孔隙压力升高、加载路径和加载速率对剪切、张拉、张剪混合断裂和摩擦行为形成的影响，从而为板块边界断层滑移相关的脉体形成提供力学视角。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。

Devastating earthquakes and tsunamis recur in subduction zones, and the time interval between large earthquake events ranges from decades and centuries. Long-lasting international collaborative research and education programs are necessary to advance understanding of earthquake source physics and transfer the knowledge from the past events to future generations. To advance understanding of deformation and slip behaviors of megathrust plate boundary faults and physics of earthquakes in subduction zones, this project involves development of innovative deformation and friction experiments on natural fault rocks at elevated pressure and temperature conditions that are anticipated along the plate boundary faults. To expand students' learning opportunities on experimental rock deformation and subduction zone earthquake and tsunami hazards, the principal investigator develops new education programs including a senior capstone course, a training course for graduate students and early-career scientists in geoscience and engineering, and an international field trip that will educate students on subduction zone earthquakes and tsunamis and hazard mitigation for natural disasters. The education programs are designed to provide hands-on laboratory experience in rock deformation and insights into subduction zone earthquakes. Trough these programs, next-generation researchers will be trained to facilitate interdisciplinary and international collaborations on tectonic, geodynamic, and engineering problems and to advance the transfer of discovery and natural hazard mitigation to future generations. Development of elevated pore fluid pressure along the megathrust plate boundary faults and thus low strength of faults are inferred from many geophysical and geological observations including low seismic velocity, high reflectivity taper angle of the accretionary prism wedge, and vein formation. This project will test the hypothesis that deformation and slip behaviors at low effective stress may control a spectrum of slip events and earthquakes observed along the megathrust plate boundary faults. A series of true-triaxial compression tests, conventional triaxial extension tests, and triaxial friction experiments under controlled pore pressure will be conducted on natural megathrust fault rocks. Low effective pressure at a range of loading paths and rates will be achieved by controlling of magnitude and pressurization rates of pore pressure. The series of experiments will document the effects of elevated pore pressure and loading paths and rates on the formation of shear, extensional, and hybrid extension-shear fracture and frictional behaviors, and thus can provide mechanical perspectives on vein formation associated with slip along the plate boundary faults.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.