Do forearc crustal faults rupture in response to stress changes from megathrust earthquakes?

Ashley Streig博士获得美国国家科学基金会EAR博士后奖学金，在俄勒冈州立大学开展研究和扩大参与计划。该项目将重点建立一个可能因特大逆冲地震而破裂的卡斯卡迪亚前弧断层的时空目录。在大逆冲地震发生后的几个月或几年里，由应力扰动引发的断层破裂对沿俯冲带的沿海地区的地震危险性有很大的影响。利用俯冲带地震记录来评估这些断层上地震的时空关系，将有助于了解地壳对大型逆冲事件的反应，并使地质学家能够更仔细地考虑卡斯卡迪亚更广泛的潜在活动震源，以及建立更全面的地壳结构动力学模型。整合拟议的地壳断层活动研究将涉及通过与美国国家科学基金会资助的“增加地球科学多样性”项目合作，向代表性不足的本科生提供服务；学生将通过实地考察、指导和实地助理参与。该项目的地貌和古地震研究将使研究者能够直接评估这些断层上地表破裂地震的滑动历史。这些事件发生的时间将与陆上古地震沉降研究直接相关，这些研究已经确定了埋藏森林和沼泽地层的年代，以及卡斯卡迪亚地震的近海浊积岩记录。该项目的方法包括使用新的激光雷达数据来绘制和表征长期（10,000 -100,000年）断层表达，并使用古地震技术来评估沿卡斯卡迪亚俯冲带的几个关键地壳断层的短期（1,000-10,000年）活动。陆上地壳前弧断层的时空活动信息将用于对特大逆冲地震后的应力降进行定性比较。

Dr. Ashley Streig has been awarded an NSF EAR Postdoctoral fellowship to carry out a research and broadening participation plan at Oregon State University. The project will focus on establishing a temporal and spatial catalog of forearc faults in Cascadia that may have ruptured as a consequence of megathrust earthquakes. Triggered fault rupture from stress perturbations in the months, and years following a megathrust earthquake has great implications for seismic hazard for coastal regions along subduction zones. Evaluating the spatial and temporal relationship of earthquakes on these faults with the record of subduction zone earthquakes will provide insight on the crustal response to megathrust events and will allow geologists to more carefully consider the broader range of potentially active seismic sources in Cascadia, as well as develop more holistic models of crustal structural dynamics. Integration of the proposed research on crustal fault activity will involve outreach to underrepresented undergraduate students through partnership with NSF funded "Increasing Diversity in Earth Sciences" program; students will be engaged through field trips, and mentoring, and as field assistants. Geomorphic and paleoseismic studies of this project will allow the investigator to directly evaluate the slip history of surface rupturing earthquakes on these faults. The timing of these events will be directly correlated with onshore paleoseismic subsidence studies that have dated buried forests and marsh stratigraphy, and the offshore turbidite record for Cascadia earthquakes. The methodology in this project includes using new LiDAR data to map and characterize the long-term (10,000 -100,000 yr.) fault expression and using paleoseismic techniques to evaluate the shorter term (1,000-10,000 yr.) activity of several key crustal faults along the Cascadia subduction zone. Information on spatial and temporal activity of onshore crustal forearc faults will be used to make a qualitative comparison of stress drops post megathrust earthquakes.