RAPID/Collaborative Research: Advancing Probabilistic Fault Displacement Hazard Assessments by Collecting Perishable Data from the 2023 Turkiye Earthquake Sequence

位于Türkiye的东安纳托利亚断层长300公里的7.8级地震破裂是全球观测到的最大的走滑破裂之一。与此同时，S断裂上最大余震的150公里长的M7.5级破裂，产生了8m量级的地表位移，平均超过2023年国家地震灾害模型更新时使用的位移-长度关系的50%以上。这些断裂与加利福尼亚州的圣安德烈亚斯断裂系统(SAFS)具有相似的构造背景，因此，在美国降低风险的背景下，通过与Türkiye断裂断裂的比较来评估NSHM是重要的。如果SAFS出现类似的破裂，将威胁到主要城市中心、国防设施和其他关键基础设施的人口和经济。因此，观测和记录沿这些极长和罕见的破裂的位移对于从经验和数字上了解和再现地震破裂过程、减少区域灾害模型中的不确定性和降低分布式基础设施系统的风险至关重要，这些基础设施系统对社区的健康和繁荣至关重要，而且容易受到地面变形，如供水和天然气管道的影响。来自快速反应研究基金(RAPID)实地工作的发现和开源数据集将通过NSHM的未来改进来指导公共政策和工程设计准则，以及更大程度上促进社会福祉和国防的决策者。为了完成这项工作，美国和Türkiye的学术界和政府机构之间建立了合作伙伴关系；团队成员多样，包括职业生涯早期的科学家和高级科学家、地球技术地震工程师和地震地质学家、美国和国内的合作者，以及来自代表性不足背景的科学家。这项工作的智力价值在于为工程应用建立了一种新的断层破裂场填图范例。虽然有现场、实验室和数字证据表明，浅层地质条件影响断层位移，但证据充其量是定性的，因此记录的数据无法整合到减少风险的工程模型中。为了在工程应用的预测经验模型中捕捉到这些影响，需要一种新的数据集，将每个断层位移测量点与岩土场地特征测量相关联。主要野外目标包括通过以下方式描述2023年的破裂：(1)用高分辨率(厘米级)GNSS调查、照片、地面激光雷达和无人机地形模型绘制主要断层破裂的地图；(2)记录文化和地貌特征的离散和易腐烂的偏移量；(3)描述形变区的宽度和样式；(4)伴随着使用活动震源和环境波场面波方法的亚公里尺度的动态场地特征测量，以及水平与垂直频谱比(HVSR)测量，来描述2023年的破裂。(5)为场地描述工作提供地质背景(例如，主要的地质过程和沉积单元)，以及(6)确定重力破坏和液化等次要影响。直接来自现场数据的洞察和缩放行为将提供第一个预期构成下一代断层位移数据集的内容，该数据集将允许未来的PFDHA模型捕获与当地地质条件和断层几何等参数相关的可重复影响。该奖项反映了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。

The 300-km-long magnitude (M) 7.8 earthquake rupture along the East Anatolian Fault in Türkiye is one of the largest strike-slip ruptures instrumented globally. At the same time, the 150-km-long M7.5 rupture of the largest aftershock on the Sürgü fault, produced surface displacements on the order of 8 m, exceeding, on average, the displacement-length relations used for the 2023 National Seismic Hazard Model (NSHM) update by more than fifty percent. These ruptures share a similar tectonic setting with the San Andreas Fault System (SAFS) in California, so evaluating the NSHM by comparison with the Türkiye fault ruptures is important in the context of risk reduction in the US. A similar rupture on the SAFS, often referred to as 'The Big One' in California, will threaten the population and economy of major urban centers, national defense installations, and other critical infrastructures. Observing and documenting displacements along these exceedingly long and rare ruptures is therefore critical to understanding and reproducing earthquake rupture processes, empirically and numerically; to reducing uncertainty in regional hazard models; and reducing the risk of distributed infrastructure systems that are vital to the health and prosperity of communities, and vulnerable to ground deformation, such as water and gas pipelines. Findings and open-source datasets from this Grant for Rapid Response Research (RAPID) fieldwork will guide public policy and engineering design codes through future improvements of the NSHM, as well as decision makers for a greater extent of societal well-being and national defense. To complete this work, partnerships between academia and government agencies in both the US and Türkiye have been established; the team is diverse and includes a balance of early-career scientists and senior scientists, geotechnical earthquake engineers and earthquake geologists, US-based and in-country collaborators, and scientists from underrepresented backgrounds. The intellectual merit of this work lies in setting a new paradigm in fault rupture field mapping for engineering applications. While there is field, laboratory and numerical evidence that shallow geological conditions affect fault displacements, the evidence is at best qualitative, and thus the documented data cannot be integrated in engineering models for risk reduction. In order to capture these effects in predictive empirical models for engineering applications, new kind of dataset is needed that associates each fault displacement measurement site with geotechnical site characterization measurements. The primary field objectives include characterization of the 2023 ruptures by means of: (1) mapping the main fault rupture with high-resolution (cm-scale) GNSS surveys, photographs, ground-based lidar, and UAV-based terrain models, (2) documenting discrete and perishable offsets of cultural and geomorphic features, (3) characterizing the width and style of the deformation zone, (4) accompanying the measurements of the transient deformation zones with dynamic site characterization measurements on a sub-km scale using active source and ambient wavefield surface wave methods, along with horizontal to vertical spectral ratio (HVSR) measurements, (5) providing geological context (e.g., dominant geological processes and depositional units) for site characterization efforts, and (6) identifying secondary effects such as gravitational failures and liquefaction. Insights and scaling behaviors stemming directly from the field data will provide the first of what is envisioned to constitute the next-generation fault displacement datasets that will allow future PFDHA models to capture repeatable effects associated with local geologic conditions and fault geometry among other parameters.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.