RAPID/Collaborative Research: Investigating Unanticipated Geotechnical Phenomena in Kumamoto, Japan, Observed from the April 2016 Earthquake Sequence

这项美日合作快速反应研究基金（Rapid）将调查2016年4月日本熊本地震序列（KES）后观察到的未预料到的和知之甚少的岩土工程现象。地质极端事件勘察组织（GEER）在地震发生后立即动员了一支美国勘察队对受灾地区进行勘察。美国团队与日本调查人员合作，确定了值得进一步调查的重要案例历史，因为它们具有独特的、未预料到的、鲜为人知的性质，以及它们对美国和世界各地的地震设计和安全的重要潜在影响。这些历史案例包括：在阿苏山火山口内有一个无法解释的10公里长的洼地，对建筑物和输电线路造成了重大破坏；溃坝：通过大坝泄洪道的断层，使水库蓄水；令人惊讶的是，对土壤液化及其对这种规模的地震和明显的现场条件的影响的观察有限。RAPID项目通过以下方式支持对这些观测结果背后的潜在原因的详细研究：(1)使用最先进的遥感技术，从已知的液化和主要滑坡地点收集易腐烂的表面拓扑结构、土壤变形和结构沉降或倾斜信息；(2)从潜在的有价值的历史案例地点收集初步的岩土、地震、地质和地形信息；(3)对回收的样品进行了综合的室内试验，然后进行了初步的模拟，以评估土壤的液化抗力和循环荷载下的响应。在此过程中，该奖项有助于提高岩土地震工程关键领域的知识和实践水平，从而提高全球岩土结构和基础设施的弹性。通过与日本研究人员的合作，将改善两国之间的关系和合作，并将为参与本项目的pi和研究生提供宝贵的国际研究经验。这项拨款将通过加强对地震引起的地面变形和液化触发的基本理解，推进岩土地震工程的科学和实践。RAPID项目将从2016年日本地震中收集与滑坡、液化触发和影响以及地震引起的地面变形有关的有价值和易腐烂的信息。在KES之后观察到的许多现象无法用现有的知识或当前的分析和/或经验预测模型来解释。这些现象可能对美国地质和地貌相似地区的地震设计产生重要影响。从受影响地点收集的信息，以及实验室测试和分析，将增加我们对KES后观察到的岩土工程现象的潜在原因的理解，这将最终影响岩土地震工程实践的状态。工程界将从了解为什么土壤液化没有发生到预测的程度中受益。联合应用基于无人机的航空摄影和地面激光雷达技术的三维数字表面建模将推进岩土工程遥感的科学和艺术，并将改善岩土地震现象地表证据的收集方式。此外，从RAPID收集的初步现场和实验室数据将指导和启发更大的国际合作研究工作，以更彻底地调查观测到的独特岩土现象和这一系列地震的损害。

This collaborative U.S.-Japan Grant for Rapid Response Research (RAPID) award will investigate unanticipated and poorly understood geotechnical phenomena observed following the April 2016 Kumamoto earthquake sequence (KES) in Japan. The Geotechnical Extreme Events Reconnaissance (GEER) organization mobilized a U.S. reconnaissance team to explore the affected area immediately following the KES. The U.S. team in collaboration with Japanese investigators identified significant case histories that warrant further investigation due to their unique, unanticipated, and poorly understood nature, as well as their important potential implications for seismic design and safety in the U.S. and around the world. These case histories include, among other things: an unexplained 10km-long depression zone within the Mount Aso volcano caldera that caused significant damage to structures and transmission lines; a fault rupture through the spillway of a large dam impounding a full reservoir; and surprisingly limited observations of soil liquefaction and its effects for an earthquake of this size and apparent site conditions. This RAPID award supports a detailed study of the underlying causes behind these observations through: (1) the use of state-of-the-art remote sensing techniques to collect perishable surface topology, soil deformation, and structure settlement or tilt information from known liquefaction and major landslide sites; (2) the collection of preliminary geotechnical, seismic, geologic, and topographic information from potential case history sites of interest; and (3) the performance of a comprehensive set of laboratory tests on retrieved samples followed by preliminary simulations to evaluate the soil's resistance to liquefaction and response under cyclic loading. In doing so, this award contributes to the state of knowledge and practice in critical areas of geotechnical earthquake engineering and hence, the resilience of geotechnical structures and infrastructure globally. Collaboration with Japanese researchers through this study will improve the relationship and cooperation between the two countries, and will provide valuable international research experience for the PIs and the graduate students involved in this project. This grant will advance the science and practice of geotechnical earthquake engineering by enhancing the fundamental understanding of seismic-induced ground deformations and liquefaction triggering. This RAPID project will enable the collection of valuable and perishable information related to landslides, liquefaction triggering and effects, and earthquake-induced ground deformations from the 2016 KES in Japan. There are a number of phenomena observed after the KES that cannot be explained by the existing state of knowledge or current analytical and/or empirical prediction models. These phenomena could have important implications for seismic design in locations with similar geology and geomorphology in the U.S. Information collected from the affected sites followed by laboratory testing and analysis will increase our understanding of the underlying causes of the geotechnical phenomena observed following the KES, which will ultimately impact the state of geotechnical earthquake engineering practice. The engineering community will benefit from learning why soil liquefaction did not occur to the extent that it was predicted in this region. Joint application of 3D digital surface modeling using UAV-based aerial photography and terrestrial LiDAR techniques will advance the science and art of remote sensing in geotechnical engineering and will improve the way surficial evidence of geotechnical earthquake phenomena is collected. Further, preliminary field and laboratory data collected from this RAPID will guide and inspire a larger international collaborative research effort to more thoroughly investigate the observed unique geotechnical phenomena and damage from this series of earthquakes.