RUI: The Frazier Mountain Paleoseismic Site: Evaluation of Fault Behavior Models with Geologic Data from the Big Bend Section of the San Andreas Fault, CA

RUI：弗雷泽山古地震遗址：利用加利福尼亚州圣安德烈亚斯断层大弯曲部分的地质数据评估断层行为模型

• 批准号: 0838294
• 负责人: Cynthia Liutkus
• 金额: $ 21.96万
• 依托单位: Appalachian State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838294&HistoricalAwards=false
• 关键词: RUI; Frazier; Mountain; Paleoseismic; Site

The characteristic earthquake model is based on the idea that over time, rupture segments and earthquake displacements at a point along a fault are fairly constant so all large earthquakes are similar in size and extent. This model has dominated fault behavior theory for the San Andreas fault because it generally agrees with several aspects of historic data. However, to test fault behavior models, long (1000 year) records of earthquake ages and slip along a fault are needed but an approximately 200 km gap in paleoseismic sites near the Big Bend prevents correlation of earthquakes along the southern San Andreas fault. In this project, research collaboration between Appalachian State University, the University of Oregon and the U.S.Geological Survey is filling this gap at site near Frazier Mountain in southern California. The goals of this investigation are to (1) extend the record of earthquakes to greater than 1000 years, (2) determine slip per event by detailed structural mapping of offset layers, and (3) develop a chronostratigraphic framework that combines traditional radiocarbon dating with paleoclimate indicators to provides additional temporal attributes for correlating earthquakes between sites. These data will contribute to earthquake rupture scenarios for the past 1500 years along the southern San Andreas fault for comparison with fault behavior models and add a dataset to the small pool of studies that permit tests of earthquake recurrence models and comparison of slip rates on different time scales.Despite its fame, the San Andreas fault is poorly understood. For example, while sufficient data exist to forecast about a 59% chance of an earthquake larger than M6.7 on the southern San Andreas fault in the next 30 years, the portion of the fault that will rupture and the amount of slip that will be produced is unknown, in part due to a spatial gap in the available paleoseismic records. Paleoseismologic studies investigate recent deposits and offsets produced by large earthquakes to determine the age and displacement of past earthquakes. This study will result in paleoseismic data from this gap and which will be used to refine models of fault behavior and earthquake recurrence. Because these models underpin probabilistic seismic hazard analyses required by Federal and State agencies and which set insurance rates, building codes, and allocation of seismic hazard mitigation resources, adding this critical data will further scientific understanding of faults and ultimately reduce societal risk from earthquakes.

特征地震模型是基于这样一种思想，即随着时间的推移，破裂段和地震位移在一个点沿着断层是相当恒定的，所以所有的大地震在大小和程度上是相似的。这个模型主导了圣安德烈亚斯断层的断层行为理论，因为它通常与历史数据的几个方面一致。然而，为了测试断层行为模型，需要地震年龄和沿沿着滑动的长（1000年）记录，但大弯附近的古地震遗址中约200 km的间隙阻止了沿沿着南部圣安德烈亚斯断层的地震相关性。在这个项目中，阿巴拉契亚州立大学、俄勒冈州大学和美国地质调查局之间的研究合作正在填补加州南部弗雷泽山附近的这一空白。本次调查的目标是（1）将地震记录扩展到1000年以上，（2）通过详细的偏移层结构图确定每次事件的滑动，（3）开发一个年代地层框架，将传统的放射性碳测年与古气候指标相结合，为不同地点之间的地震关联提供额外的时间属性。这些数据将有助于地震破裂的情况下，在过去的1500年沿着南部圣安德烈亚斯断层与故障行为模型进行比较，并添加一个数据集的小池的研究，允许测试地震复发模型和比较滑动率在不同的时间scale.Despite它的名气，圣安德烈亚斯断层知之甚少。例如，虽然有足够的数据预测未来30年内圣安德烈亚斯断层南部发生6.7级以上地震的可能性为59%，但断层断裂的部分和产生的滑动量是未知的，部分原因是现有古地震记录中存在空间空白。古地震学研究调查最近的沉积物和大地震产生的偏移，以确定过去地震的年龄和位移。这项研究将导致从这个空白的古地震数据，并将用于完善模型的断层行为和地震复发。由于这些模型支持联邦和州机构所要求的概率地震灾害分析，并设定保险费率、建筑规范和地震灾害缓解资源的分配，因此添加这些关键数据将进一步科学地了解断层，并最终降低地震的社会风险。