Collaborative Research: Improving the Chronology of Deformation and Earthquakes at La Rinconada, Argentina: Testing Segmentation and Recurrence Patterns of Blind Thrust Regimes

了解盲逆冲断层（不到达地球的断层）的地震潜力？在美国的洛杉矶和西雅图等人口稠密地区以及世界各地地震活跃区内的其他人口中心，地震危险性很大。关于破坏性地震断层的长期行为的关键问题包括地震的大小和频率，以及它们如何在时间和空间上变化。更好地了解过去地震的时间和规模是预测未来事件、确定当地和区域地震灾害特征以及告知公众和应急规划人员的重要信息。然而，人口稠密的地区很难研究，因为混凝土、建筑物和发展掩盖了活动断层的表现。本研究对阿根廷圣胡安附近的一个活动断层系统进行了研究，以更好地了解几个活动的盲冲断层的地表表现和地震历史，该系统与美国大都市区内的盲断层具有结构相似性，但具有该地区基本未受干扰的优势。该项目的重点是对地震断层变形和断裂的河流阶地和冲积层收集的大量样品进行测年。根据这些新数据，将建立过去5次大地震在盲断层系统上的时间。新时代的数据将允许与早期工作中记录的附近断层系统的地震历史进行比较，这些断层负责1944年和1977年该地区的破坏性地震。该项目将测试单个断层上的地震频率是否具有准周期性（因此是可预测的），这些断层系统是否会产生及时聚集的地震，并测试过去的一些地震是否可能破坏了一个更大的震源区域，或者与历史事件一样被限制在相同的震源维度。与该项目的早期成果一样，阿根廷合作者和其他人将利用该项目的新成果来限制地震危害，告知地震工程师，并教育公众有关地震危害的知识。

Understanding the earthquake potential of blind thrust faults (faults that do not reach the Earth?s surface) has major seismic hazard implications for heavily populated areas such as Los Angeles and Seattle in the United States as well as other population centers within seismically active regions around the World. Key questions regarding the long-term behavior of destructive earthquake faults include what are the size and frequency of earthquakes and how do those vary in time and space. Better knowledge of the timing and sizes of past earthquakes is essential information used to forecast future events, to characterize local and regional seismic hazards, and to inform the public and emergency planners. Heavily populated areas, however, are difficult to study because concrete, buildings, and development obscure the expression of active faults. In this study, an active fault system near San Juan Argentina, which bears structural similarities to blind faults within metropolitan regions in the United States, but has the advantage that the area is largely undisturbed, is being investigated to better understand the surficial expression and earthquake history of several active blind thrust faults. This project is focused on dating of a large suite of samples collected from river terraces and alluvium deformed and faulted by the earthquake faults. From these new data, the timing of the past five large earthquakes on the blind fault system will be established. The new age data will allow comparison with the earthquake history of nearby fault systems documented in earlier work, faults that were responsible for damaging earthquakes in 1944 and 1977 in the region. This project will test whether earthquake frequency on individual faults is quasi-periodic (and therefore predictable), whether these fault systems produce earthquakes that cluster in time, and test whether some past earthquake may have ruptured a larger source region or have been confined to the same source dimensions as the historical events. Like the results from an earlier phase of this project, the Argentinean collaborators and others will use the new results from this project to constrain seismic hazard, inform earthquake engineers, and educate the public about earthquake hazards.