Collaborative Research: Paleoseismology of the M7.3 1915 Pleasant Valley Earthquake Ruptures

该项目旨在利用地质学评估1915年在内华达州欢乐谷发生7.3级地震的断层上过去发生的大地震的规模和发生频率，这是一项科学、教育和外联合作计划的基础。正是通过对个别地震的累积研究，研究界获得了观察，以了解地震破裂及其在活动构造过程中的作用。从该项目中获得的信息将被纳入国家危险地图，旨在减少未来地震中建筑基础设施和生命线的故障和生命损失。三个研究所的合作旨在为本科生和研究生提供机会，在一个积极的研究项目框架内学习与地震科学有关的方法和概念，开发用于教育和研究的在线和课堂材料，在内华达农村大学校园和里诺内华达大学之间建立联系。三个参与机构中的两个的首席研究人员是职业生涯早期的女性研究人员。这项研究将考虑近代史上发生的为数不多的大陆大地震之一，并消除我们对盆地和山脉以及内华达中部地震带活动构造的集体理解中的一个重大空白。这项研究将量化过去地震的时间和1915年发生7.3兆瓦地震的断层上的平均滑动速度。使用现代加速器质谱仪放射性碳谱、光学受激发光和陆地宇宙成因测年方法，结合本文提出的古地震沟槽研究，将产生以下观测：1)评估盆地和山脉内部内华达中部地震带向北滑动速率增加的程度，2)确定欢乐谷过去的事件历史是否显示出在南部内华达中部地震带观察到的事件的反复聚集，3)解决1915年断裂的链是否在过去的地震中表现出相同的行为，4)将晚更新世期间的地质滑动速率与现代地震相比较，5)对应用于相同沉积物的多种测年技术进行交叉验证，以及6)对欢乐谷冲积扇沉积的时间进行定量限制，以此作为评估具有相同地貌和土壤特征的相邻山脉前缘断层滑动速率的可能工具。总而言之，大陆正断层地震破裂很少，可以用来收集与破裂和复发特征有关的观测。这项研究将提供基础，比较1915年断裂和以前发生的断裂的特征，包括1915年断裂和全球其他地方的断裂。收集的数据将对地震复发的概念模型和地震过程的物理模型进行观测，这构成了地震危险性分析的基础。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project to use geology to assess the past size and frequency of occurrence of large earthquakes on the fault that produced the magnitude 7.3 1915 Pleasant Valley earthquake in Nevada forms the underpinnings of a collaborative program of science, education and outreach. It is through the cumulative study of individual earthquakes that the research community gains observations to understand earthquake ruptures and their role in active tectonic processes. The information gained in this project will be incorporated into the National Hazard Maps designed to reduce failure of building infrastructure and lifelines and loss of life in future earthquakes. The collaboration of three institutes is designed to provide the opportunity for undergraduate and graduate students to learn methods and concepts bearing on earthquake science in the framework of an active research project, lead to the development of online and classroom materials for education and research, create links between rural Nevada college campuses and the University of Nevada, Reno. Principal investigators at two of the three participating institutions are early career female researchers.The study will consider one of the few large continental earthquakes that occurred in recent history and remove a significant void in our collective understanding of active tectonics in the Basin and Range and the Central Nevada Seismic Belt. This research will quantify the timing of past earthquakes and the average rate of slip on the fault that produced the Mw 7.3 1915 earthquake. The use of modern Accelerator Mass Spectrometry radiocarbon, Optical Stimulated Luminescence, and Terrestrial Cosmogenic dating methods in conjunction with paleoearthquake trenching investigations proposed herein will yield observations to 1) assess the northward extent to which slip rate is elevated along the Central Nevada Seismic Belt within the interior of the Basin and Range, 2) to determine whether the past history of events in Pleasant Valley exhibits repeated clustering of events that is observed in the Central Nevada Seismic Belt to the south, 3) address whether or not strands of the 1915 rupture separated by a 4 kilometer step in trace exhibited the same behavior in past earthquakes, 4) compare geologic rates of slip during the late Pleistocene as compared to modern geodesy, 5) cross-check multiple dating techniques applied to the same sediments, and 6) develop quantitative constraints on the timing of alluvial fan deposition in Pleasant Valley as a possible tool for assessing fault slip rates on adjacent range fronts exhibiting the same geomorphic and soil characteristics. In sum, there are few continental normal fault earthquake ruptures on which to gather observations bearing on the characteristics of rupture and recurrence. This study will provide the basis to compare and contrast characteristics of the 1915 ruptures to those that occurred before, both on the 1915 fault and elsewhere around the globe. The data collected will place observational bounds on conceptual models of earthquake recurrence and the physics of earthquake processes that form the underpinnings of seismic hazard analysis.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.