NSFGEO-NERC: Latest Pleistocene-Holocene incremental slip record of the Kekerengu-Jordan fault system, northern South Island, New Zealand

沿着走滑断层的大地震破裂的标准模型是，产生地震的滑动发生在单一的表面上。2016年11月14日，新西兰凯库拉7.8级地震动摇了人们对断层滑动行为的看法。这一事件最初似乎是由沿着单一断层滑动造成的，但事实证明更加复杂，在一个称为马尔伯勒断层系统的断层网络中，滑动从一个断层跳到另一个断层。在这个项目中，来自英国南加州大学和新西兰的一个研究小组将使用各种尖端方法来重建马尔伯勒断裂系统之一的科克伦古-约旦断裂系统的滑动和古地震历史，该断裂系统在2016年的事件中经历了约12米的滑动。这个项目收集的数据将与系统中其他断层的数据结合使用，以更好地了解地震复发率，更重要的是，这些断层之间的时间和空间联系，这在凯库拉地震之前显然没有得到很好的理解。了解大地震对日益城市化的美国人口的威胁，对于促进采取积极有效的措施减少未来的生命和财产损失至关重要。然而，由于目前缺乏关于相互关联的地震断层系统如何在具有潜在破坏性的大地震中储存和释放地震能量的信息，人们对大地震在时间和空间上的发生情况的理解仍然严重受限。全面的数据集，如本项目将产生的数据集，将揭示断层系统中的主要断层如何相互作用，以产生潜在的破坏性地震。这些类型的观测反过来将使人们能够更好地预测美国类似的断层网络会带来什么，特别是在地震多发的加利福尼亚州，但更普遍的是，预测美国大部分地区的所有主要断层。该项目有可能造福社会或推动预期的社会成果，办法是让妇女充分参与STEM，通过外联活动提高STEM的公众科学素养，通过更好地了解地震潜在的基本过程来改善社会个人的福祉，这将提高建立地震灾害模型的能力，通过研究生培训发展一支多样化的、具有全球竞争力的STEM工作人员队伍，并通过国际合作增加伙伴关系。主要目的是增进对区域断层网络集体行为的了解，特别是地震群和应变瞬变等紧急现象的重要性，这些现象在目前对地震物理的理解中可能无法预料到，也没有在当前的地震危险评估战略中考虑在内。越来越多的证据表明，大地震在单个断层和断层系统上的发生都不是一个随机过程，在区域断层系统中，随着时间和空间上地震聚集的观察增加，断层滑动速率的增量变化，断层加载速率的变化，以及在力学互补的断层上潜在地协调滑动的消长。尽管彻底了解这种现象的原因和共性对于断层力学、地震物理学和更准确地评估地震危险性具有基本的重要性，但对这些行为的重要性的评估一直受到严重的数据限制。特别是，全面的古地震和增量断层滑动速率数据集太少，无法全面评估主要板块边界断裂系统在时间和空间上的集体行为。这项研究以新西兰南岛北部太平洋-澳大利亚板块边界为重点，以完整的最新更新世-全新世(15ka至今)板块边界滑动增量记录为基础，涵盖了该系统中的所有主要构造。研究小组将在以前工作的基础上，通过为克克伦古-约旦断层系统开发可靠的记录，该系统是一个85公里长的斜向反右旋断层系统，是板块边界陆上部分滑动最快的断层，每年滑动25-30毫米。2016年凯库拉7.8级地震中，科克伦古-约旦断层系统的滑动产生了大部分瞬间释放。新的IR IRSL225发光测年协议将用于Kekerengu-Jordan断层系统上的关键地点，以及新西兰政府收集的具有新的震后高分辨率激光雷达数据的更多地点。这项新的发光测年技术为研究地区典型的贫碳沉积物提供了精确和可重复性的测年，其精度与放射性碳测年大致相同。将递增的断层偏移量和沟槽观测与IR后IRSL225年代测定和碳14分析相结合，将得出沿断层系统的详细断层滑移率和地震年龄，这些断层系统跨越数十次地震。结合陆上和近海断层的现有数据集，包括科克伦古-约旦断层系统下的俯冲巨型逆冲，这项研究将促进对最新更新世-全新世期间板块边界应变释放的全面、系统水平的分析。这一裁决反映了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。

The standard model for rupture of large earthquakes along strike-slip faults is that the slip that generates the earthquake occurs on a single surface. The November 14, 2016 Kaikoura, New Zealand, magnitude 7.8 earthquake shook up this thinking about fault slip behavior. In what initially seemed to be an event resulting from slip along a single fault, turned out to be more complex with slip jumping from one fault to another within a network of faults called the Marlborough fault system. In this project, a research team from the University of Southern California, United Kingdom, and New Zealand will use a variety of cutting-edge methods to reconstruct the slip and paleo-earthquake history of one of the Marlborough fault system faults, the Kekerengu-Jordan fault system, which experienced about 12 meters of slip in the 2016 event. Data collected in this project would be used in conjunction with data from other faults in system to better understand earthquake recurrence rates and, more importantly, the temporal and spatial linkage between these faults, something that was clearly not well understood before the Kaikoura earthquake. Understanding the threat from major earthquakes to an increasingly urbanized American population is of critical importance for facilitating proactive and efficient measures to reduce future loss of life and property. Yet understanding of what to expect in terms of the occurrence of large earthquakes in time and space remains severely limited by the current lack of information about how entire systems of inter-connected earthquake faults store and release seismic energy in large, potentially damaging earthquakes. Comprehensive data sets, such as those that will result from this project will reveal how the major faults in a fault system interact with one another to generate potentially damaging earthquakes. These kinds of observations will, in turn, allow for better forecasting of what to expect from similar fault networks in the United States, particularly in earthquake-prone California, but more generally for all of the major faults that underlie large parts of the country. The project has potential to benefit society or advance desired societal outcomes through full participation of women in STEM, increased public scientific literacy with STEM through outreach activities, improved well-being of individuals in society by better understanding of fundamental processes underlying earthquakes that would improve the capability to model earthquake hazards, development of a diverse, globally competitive STEM workforce through graduate student training, and increased partnerships through international collaboration.The primary aim is to advance understanding of the collective behavior of regional fault networks, particularly the importance of emergent phenomena such as earthquake clusters and strain transients that may not be expected in the current understanding of earthquake physics and that are not accounted for in current seismic hazard assessment strategies. Mounting evidence suggests that the occurrence of large earthquakes on both single faults and fault systems is not a random process, with increasing observations of temporal and spatial earthquake clustering, changes in incremental fault slip rates, variations in fault loading rates, and potentially coordinated waxing and waning of slip on mechanically complementary faults in regional fault systems. Although a thorough understanding of both the causes and generality of such phenomena is of basic importance for fault mechanics, earthquake physics, and more accurate assessment of seismic hazard, evaluation of the importance of these behaviors has been severely data limited. In particular, there are too few comprehensive paleo-earthquake and incremental fault slip rate data sets to fully assess the collective behavior of major plate-boundary fault systems in time and space. This study focuses on the Pacific-Australia plate boundary in northern South Island New Zealand in order to document a complete latest-Pleistocene-Holocene (15 ka-present) record of incremental plate boundary slip encompassing all major structures in the system. The research team will build on previous work by developing robust records for the Kekerengu-Jordan fault system, an 85-km-long, oblique reverse-dextral fault system, which is the fastest-slipping fault in the onshore part of the plate boundary at 25-30 mm/year. Slip on the Kekerengu-Jordan fault system generated most of the moment release in the 2016 Mw=7.8 Kaikoura earthquake. The new post-IR IRSL225 luminescence dating protocol will be used at key sites on the Kekerengu-Jordan fault system, and at additional sites located with the new post-earthquake high-resolution lidar data collected by the New Zealand government. This new luminescence dating technique provides precise and reproducible dating of carbon-poor sediments typical of those in the study area with precision roughly equal to that of radiocarbon dating. Combining incremental fault offsets and trench observations with post-IR IRSL225 dating, and carbon-14 analysis will yield detailed fault slip rates and earthquake ages along the fault system spanning individual ruptures back though several dozen earthquakes. In conjunction with existing data sets from both the onshore and offshore faults, including the subduction megathrust that underlies the Kekerengu-Jordan fault system, the research will facilitate a comprehensive, system-level analysis of plate-boundary strain release through time and space during latest Pleistocene-Holocene time.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.