Collaborative Research: Paired paleoseismic and slip rate analysis of the central Garlock fault: Towards a true dated path of incremental slip on a major strike-slip fault

合作研究：加洛克中央断层的成对古地震和滑动率分析：寻找主要走滑断层上增量滑动的真正过时路径

• 批准号: 1650377
• 负责人: James Dolan
• 金额: $ 35.22万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650377&HistoricalAwards=false
• 关键词: Collaborative; Research; Paired; paleoseismic; slip

Knowledge of historic and prehistoric recurrence intervals and slip rates for large faults is important for seismic hazard assessment as well as understanding the fundamentals of earthquake mechanics. Long-term records are essential since recurrence intervals for large earthquakes typically exceed modern instrumental records (e.g. Tohoku, Cascadia, etc.). Paleoseismic studies and slip rate measurements are used to assess recurrence intervals and earthquake potential for active faults or fault networks. These studies suggest earthquakes may cluster both spatially and temporally, slip rates may change significantly over time, and some fault networks demonstrate coordinated behavior, but definitive studies in support of these ideas are sparse. Previous paleoseismic and slip rate studies on the Garlock fault, southern California, suggest that it may have experienced fast slip events that correlate with earthquake clusters that alternated with slow slip events, or seismic lulls, that correlate with decreased rates of strain accumulation. This study would provide a definitive analysis of the prehistoric record of earthquake occurrence and fault slip in order to determine if this behavior is typical for the Garlock fault over the past 15,000 years. The results will help the scientific community better understand what controls the occurrence of large earthquakes on systems of faults so that more informed earthquake forecasts are possible. Other desired societal outcomes include full participation of women and underrepresented minorities in STEM, improved STEM educator development through a teacher summer research program, and development of a globally competitive STEM workforce through training of undergraduate and graduate students.There is mounting evidence that the occurrence of large earthquakes on both single faults and fault systems is not a random process. For example, earthquakes commonly cluster in both space and time. The growing recognition that earthquake occurrence can be highly irregular in time and space will eventually call for a new and more sophisticated method of seismic hazard analysis that takes this behavior into account. Before such new methods can be developed, however, it is necessary to understand the nature of phenomena such as earthquake clustering and the conditions under which they occur. This project will develop a detailed prehistoric record of fault slip as a function of time for the Garlock fault, a fault known to have produced earthquakes with pronounced clustering over time. For example, the Garlock fault produced four large earthquakes in the past 2,000 years, no earthquakes between 2,000 and 5,000 thousand years ago, and two earthquakes between 5,000 and 7,000 thousand years ago. This project tests whether this clustering, which has been observed at one location on the fault, is also reproducible at two other locations along the fault and extends the record of prehistoric earthquakes farther back in time to document whether the fault has been seismically quiescent for any other millennia. To do so, paleoseismic and incremental slip rate data will be acquired from the central Garlock fault through: (a) excavation of paleoseismic trenches at three sites, two of which were previously un-datable because of the dearth of datable carbon; (b) documentation of incremental fault slip rates at two sites for offsets ranging from 30-80m; (c) dating of additional small (3-18 m) offsets based on analysis of GeoEarthScope lidar data at several sites to better constrain the dated slip-path during the past few earthquakes; (d) compilation of these and previous data into a comprehensive, published record of incremental slip and paleo-earthquake ages for the Garlock fault, facilitating comparison with similar data from other major faults. Utilization of the new post-IR-IRSL225 single-grain luminescence dating method will allow the research team to determine the ages of previously un-datable strata and landforms.

对大断层的历史和史前复发间隔和滑移率的了解对于地震危害评估以及了解地震力学的基本原理很重要。长期记录是必不可少的，因为大地震的复发间隔通常超过现代的工具记录（例如Tohoku，Cascadia等）。古介质研究和滑移速率测量用于评估主动断层或断层网络的复发间隔和地震潜力。这些研究表明，地震可能在空间和时间上聚集，滑移速率可能会随着时间的推移发生巨大变化，并且某些断层网络表现出协调的行为，但是支持这些思想的确定性研究很少。先前对加利福尼亚州Garlock断层的古糖震和滑移率研究表明，它可能经历了与地震簇相关的快速滑移事件，这些事件与慢速滑移事件或地震效果交替的地震簇相关，这与降低的应变率相关。这项研究将对地震发生和断层滑移的史前记录提供明确的分析，以确定过去15，000年中Garlock断层是否典型的行为。结果将有助于科学界更好地了解是什么控制了故障系统上大地震的发生，从而有可能进行更明智的地震预测。其他期望的社会成果包括妇女的全面参与和代表性不足的STEM参与，通过教师夏季研究计划改善了STEM教育者的发展，以及通过培训本科生和研究生的培训来开发全球竞争激烈的STEM劳动力。单个断层和断层系统上的大地震不是一个随机过程。 例如，地震通常在时空聚集。 人们对地震发生可能在时间和空间上可能是高度不规则的认识，最终将要求采用一种新的，更复杂的地震危害分析方法，从而考虑到这种行为。 但是，在开发这种新方法之前，有必要了解现象的性质，例如地震聚类及其发生的条件。 该项目将开发出详细的故障滑移记录，这是Garlock故障的时间的函数，这是一个已知的断层，随着时间的流逝，已知的地震引起了明显的聚类。 例如，Garlock的断层在过去2,000年中引起了四次大地震，没有2,000至5,000年前的地震，在5,000至7,000千年前的两次地震。 该项目测试该集群是否在断层上的一个位置观察到的聚类是否在其他两个位置也可以重现，并将史前地震的记录延伸到更远的时间，以记录该错误是否在任何地震上都静止不动。其他几千年。为此，通过：（a）在三个地点的壁carlock沟沟进行），从中央的Garlock断层中获取了古震差和递增的滑移率数据，其中两个以前是由于数据缺乏的； （b）在两个位点的增量断层滑移率的记录，范围为30-80m； （c）基于对多个地点的地球景点雷达数据分析的分析，对其他小（3-18 m）的偏移进行了约会，以更好地限制过去几个地震的过时的滑动路径； （d）将这些数据和以前的数据汇编为Garlock断层的全面，已发表的增量滑移和古Quake age年龄的记录，从而促进了与其他主要故障的相似数据的比较。利用新的后IIR-IRSL225单颗粒发光约定方法将使研究团队能够确定以前不可依赖的地层和地面的年龄。