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

沿<s:1>基耶东部安纳托利亚断层的300公里长的7.8级地震破裂是全球测量到的最大的走滑破裂之一。与此同时，Sürgü断层上150公里长的最大余震的7.5级破裂产生了8米左右的地表位移，平均超过了2023年国家地震危险模型（NSHM）更新中使用的位移-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层系统（SAFS）具有相似的构造背景，因此通过与<s:1> rkiye断层破裂进行比较来评估NSHM在美国降低风险的背景下非常重要。类似的SAFS破裂，通常被称为加州的“大破裂”，将威胁到主要城市中心的人口和经济、国防设施和其他关键基础设施。因此，观察和记录沿着这些极长且罕见的裂缝的位移，对于从经验和数值上理解和再现地震破裂过程至关重要；减少区域灾害模型的不确定性；减少分布式基础设施系统的风险，这些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的影响，比如水和天然气管道。这项快速反应研究（Rapid）实地工作的发现和开源数据集将通过NSHM的未来改进指导公共政策和工程设计规范，以及决策者在更大程度上的社会福祉和国防。为了完成这项工作，美国和日本的学术界和政府机构之间建立了伙伴关系；该团队是多元化的，包括早期职业科学家和资深科学家、岩土地震工程师和地震地质学家、美国和国内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断层破裂场测绘的新范式。虽然有现场、实验室和数值证据表明浅层地质条件会影响断层位移，但这些证据充其量是定性的，因此记录的数据不能集成到工程模型中以降低风险。为了在工程应用的预测经验模型中捕捉这些影响，需要将每个断层位移测量点与岩土工程站点特征测量相关联的新型数据集。主要的现场目标包括通过以下手段对2023年的裂缝进行表征：(1)利用高分辨率（厘米尺度）GNSS调查、照片、地面激光雷达和基于无人机的地形模型绘制主断层破裂图；(2)记录离散和易腐烂的文化和地貌特征偏移；(3)表征变形带的宽度和样式；(4)利用有源和环境波场表面波方法在亚公里尺度上对瞬态变形带进行动态现场表征测量。以及水平与垂直光谱比（HVSR）测量，(5)为现场表征工作提供地质背景（例如，主要地质过程和沉积单元），以及(6)识别次要影响，如重力失效和液化。直接来自现场数据的洞察力和缩放行为将为下一代断层位移数据集提供第一个设想，这将使未来的PFDHA模型能够捕获与当地地质条件和断层几何形状以及其他参数相关的可重复效应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.