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

这项合作的美日快速反应研究赠款(RAPID)奖将调查2016年4月日本熊本地震序列(KES)后观察到的意外和鲜为人知的岩土现象。岩土极端事件侦察(GEER)组织动员了一支美国侦察小组，在KES发生后立即勘探受影响的区域。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，因为它们具有独特的、意想不到的和鲜为人知的性质，以及它们对美国和世界各地抗震设计和安全的重要潜在影响。这些案例除其他外包括：阿索火山喷口内一个长达10公里的无法解释的洼地地带，对建筑物和输电线路造成重大破坏；一座蓄满水库的大型大坝溢洪道发生断层破裂；对土壤液化及其对如此规模的地震和明显的场地条件的影响的观测令人惊讶地有限。这一快速奖励通过以下方式支持对这些观测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、土壤变形和结构沉降或倾斜信息；(2)从潜在的感兴趣的案例地点收集初步的岩土、地震、地质和地形信息；以及(3)对取回的样本进行一套全面的实验室测试，然后进行初步模拟，以评估土壤对液化的抵抗力和在循环荷载下的反应。通过这样做，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复原力。通过这项研究与日本研究人员的合作将改善两国之间的关系和合作，并将为参与该项目的私人投资机构和研究生提供宝贵的国际研究经验。这笔赠款将通过加强对地震引起的地面变形和液化触发的基本了解，促进岩土地震工程的科学和实践。这一快速项目将能够收集与2016年日本KES的山体滑坡、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。在知识经济之后观察到的一些现象不能用现有的知识状态或当前的分析和/或经验预测模型来解释。这些现象可能会对美国地质和地貌相似的地区的抗震设计产生重要影响。从受影响的地点收集信息，然后进行实验室测试和分析，将增加我们对KES之后观察到的岩土现象的根本原因的理解，这些现象最终将影响岩土地震工程实践的状态。工程界将受益于了解为什么土壤液化没有发生到该地区预测的程度。基于无人机的航空摄影和地面激光雷达技术相结合的三维数字表面建模技术的联合应用，将促进岩土工程遥感的科学和艺术，并将改善收集岩土地震现象地表证据的方式。此外，从这次快速地震中收集的初步现场和实验室数据将指导和激励更大的国际合作研究努力，以更彻底地调查所观察到的独特的岩土现象和这一系列地震造成的破坏。

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.