CAREER: Using seismic sources to probe megathrust fault conditions

在俯冲带，一个海洋构造板块滑到一个大陆板块之下，这里会发生毁灭性的地震和海啸，使世界上一些人口最稠密的沿海地区处于危险之中。卡斯卡迪亚俯冲带，从加利福尼亚北部延伸到不列颠哥伦比亚省西南部，每几百年就会发生一次9级的“巨型逆冲”地震（不规则的时间），最近一次是在300多年前。在CAREER奖的支持下，范和他的团队将利用大型地震仪阵列20多年来的地震数据来表征卡斯卡迪亚俯冲带断层的特性，以及日本和阿拉斯加的俯冲断层。他们将研究这三个地点的断层带性质如何与地震滑动行为相对应，这对于预测未来的大逆冲地震破裂及其潜在影响是必要的。研究成果将纳入一个多管齐下的教育和推广计划，包括本科生教学、本科生和研究生的研究和指导，以及一个涉及加州高中科学教师的持续推广项目。大逆冲滑动事件与断裂环境在地震旋回中共同演化。了解俯冲带各种滑动事件的源过程，有助于阐明俯冲界面的非均质应力和强度条件。成像精细尺度的材料特性也可以提供对可能调节各种滑移事件发展的物理机制的见解。该合同将同时研究这两个方面，系统地探测、定位和模拟特大逆冲发震斑块边缘的极低频地震，解决小到中等震级地震的有限源属性，以及用高频体波相位成像断层带属性。总的来说，这些结果将用于跟踪断裂带环境的时空演变，揭示不同滑动事件之间的相互作用和触发过程。该合同将比较研究三个俯冲带，包括日本、卡斯卡迪亚和阿拉斯加俯冲带，使用陆上和海上地震记录。预期的小尺度性质的发现可能适用于所有大型逆冲断层，而应力和强度非均质性的发现可以根据日本俯冲带的知识为卡斯卡迪亚和阿拉斯加的未来危险提供信息。该教育计划将实施基础和可持续的桥梁活动，为来自代表性不足的少数群体的学生建立通往地震学和地球物理学学位和职业的途径。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。

Subduction zones, where an oceanic tectonic plate slides beneath a continental plate, host devastating earthquakes and tsunamis that put some of the world’s most densely populated coastal regions at risk. The Cascadia Subduction Zone, which extends from northern California to southwest British Columbia, produces magnitude 9 'megathrust' earthquakes every few hundred years (on an irregular schedule), and the last was over three hundred years ago. Supported by this CAREER award, Fan and his group will use over two decades of earthquake data from large arrays of seismometers to characterize properties of the Cascadia Subduction Zone fault, as well as subduction faults in Japan and Alaska. They will investigate how fault zone properties in all three locations correspond to earthquake slip behaviors, which is necessary to forecast future megathrust earthquake ruptures and their potential impacts. The research findings will be incorporated into a multi-pronged education and outreach plan combining undergraduate instruction, undergraduate and graduate student research and mentoring, and a continuous outreach project involving California high school science teachers. Megathrust slip events and faulting environments co-evolve during seismic cycles. Understanding the source processes of various slip events at subduction zones can illuminate heterogeneous stress and strength conditions along the subduction interface. Imaging fine-scale material properties can also offer insights into physical mechanisms that may regulate the development of various types of slip events. This award will investigate these two aspects simultaneously by systematically detecting, locating, and modeling very low frequency earthquakes at megathrust seismogenic patch edges, resolving finite-source attributes of small to moderate magnitude earthquakes, and imaging fault zone properties with high-frequency body wave phases. Collectively, the results will be used to track spatiotemporal evolutions of the fault zone environments and unravel the interaction and triggering processes among different slip events. The award will comparatively study three subduction zones, including the Japan, Cascadia, and Alaska subduction zones, using both onshore and offshore seismic records. The expected findings on small-scale properties might be universal to all megathrust faults, while findings on stress and strength heterogeneities could inform future hazards at Cascadia and Alaska based on the knowledge from the Japan subduction zone. The education initiative will put into place foundational and sustainable bridging activities that will establish pathways for students from underrepresented minority groups into seismology and geophysics degrees and careers.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.