RAPID: Cone Penetration Testing (CPT) and Spectral Analysis of Surface Waves (SASW) Testing at Seismograph Stations with Liquefiable Soils Affected by the Tohoku Earthquake, Japan

这项快速反应研究（Rapid）资助是针对2011年3月11日日本东北9.0级地震的一项详细研究，该研究特别关注在可液化土壤下的一组强地面运动记录站的土壤条件特征，该地震是有史以来最大的地震之一。地震发生后，来自岩土极端事件勘测协会（GEER）的先遣队前往日本，与来自日本岩土学会、城市地震工程中心和港口机场研究所的日本同事协调易腐数据的收集和研究工作。在这次访问中，在发生液化的主要强地面运动记录站进行的锥突穿透测试（CPT）和表面波频谱分析（SASW）测试被确定为美国可以为美日联合侦察工作做出贡献的优先研究任务。GEER先遣队访问了关东平原地区可液化土壤下的14个强地面运动记录站，其中包括几个井下和地面记录站。这些观测站的峰值地面加速度范围为0.14 ~ 0.22 g，其中7个观测站观测到地表液化的证据。此外，港口和机场研究所表示，他们在更北的地方有几个强烈的地面运动记录站，那里的震动更强，下面是可液化的土壤，包括一些地面改善。这些关键的地面运动记录代表了一组独特的数据，记录了这次9.0级地震产生的长时间震动中软土的动态反应和液化。因此，这些数据可用于锚定液化触发曲线和细化震级比例因子，评估估算地表变形的程序，并评估可液化土壤的动态现场响应分析模型。然而，在准确地进行后续分析之前，对这些位点进行适当的表征是必不可少的一步。目前，这些井场的地下信息仅限于单个标准穿透测试（SPT）和每个井场的井下横波速度（Vs）剖面。在六个或更多最重要的强地面运动记录站进行的SASW测试将获得CPT测深和许多额外的v剖面。在美国和世界大部分地区，CPT通常比SPT更适合用于评估液化触发，但由于各种原因，CPT在日本相对不常见，我们的日本同事不太可能进行这项工作。这项工作是一个重要而有价值的贡献，将提高这些案例历史的价值，并将它们与美国的实践联系起来。该项目的紧迫性是由于：(1)震后修复工作可能会改变关键站点的地面条件；(2)需要快速分发CPT和SASW结果，如果在地震动记录用于其他研究之前获得这些结果，将产生最大的影响。这项研究的结果预计将有助于在美国和世界其他地方用于预测和模拟液化效应的程序方面取得重大进展。自1964年新泻地震以来，美国和日本之间存在着重要的研究合作。两国都从这种伙伴关系中受益，并将这些经验作为跳板，在抗震设计和建筑标准方面引领世界其他地区。CPT和SASW测试将与我们的日本同事密切协调，通过促进我们各自国家的研究人员和学生在测试实践方面的交叉培训，努力继续这一传统，为新的和重要的国际合作提供途径。

This Grant for Rapid Response Research (RAPID) award is for a detailed study that focuses specifically on characterizing the soil conditions at a select set of strong ground motion recording stations that are underlain by liquefiable soils in regards to the March 11, 2011 magnitude 9.0 Tohoku, Japan Earthquake, which ranks as one of the largest in recorded history. In the aftermath of the earthquake, an advance team from the Geotechnical Extreme Events Reconnaissance (GEER) Association traveled to Japan to coordinate perishable data collection and research efforts with our Japanese colleagues from the Japanese Geotechnical Society, the Center for Urban Earthquake Engineering, and the Port and Airport Research Institute. On this visit, Cone Penetration Testing (CPT) and Spectral Analysis of Surface Waves (SASW) testing at key strong ground motion recording stations where liquefaction occurred were identified as priority research tasks that the US could contribute to joint US-Japan reconnaissance efforts. The GEER Advance Team visited 14 strong ground motion recording stations underlain by liquefiable soils in the Kanto Plain region, including several with both downhole and surface recordings. Peak ground accelerations at these stations ranged from 0.14 to 0.22 g, and surface evidence of liquefaction was observed at 7 of them. In addition, the Port and Airport Research Institute has indicated they have several strong ground motion recording stations further to the north, where shaking was stronger, that are underlain by liquefiable soils, including some with ground improvements. These key ground motion recordings represent a unique set of data that captures the dynamic response and liquefaction of soft soils during long-duration shaking produced by this M9.0 earthquake. As such, these data can be used to anchor liquefaction triggering curves and refine magnitude scaling factors, assess procedures for estimating ground surface deformations, and evaluate dynamic site response analysis models for liquefiable soils. However, proper characterization of these sites is an imperative step before subsequent analyses can be performed accurately. Subsurface information at these sites is currently limited to a single Standard Penetration Test (SPT) and downhole shear wave velocity (Vs) profile at each site. CPT soundings and many additional Vs profiles from SASW testing at six or more of the most significant strong ground motion recording stations will be obtained. CPT is often preferred over SPT in the US and much of the world for evaluating liquefaction triggering, but CPT is relatively uncommon in Japan for various reasons, and it is unlikely that this work will be performed by our Japanese colleagues. This work is an important and valuable contribution that will enhance the value of these case histories and tie them to US practice. The urgency of this project is due to: (1) the possibility of post-earthquake repair work that could modify ground conditions at key sites, and (2) the need for rapid distribution of CPT and SASW results, which will have maximum impact if obtained before the ground motion records are used for other research studies.The results of this study are expected to contribute to a significant advancement in the procedures used to predict and model liquefaction effects across the US and elsewhere in the world. Significant research collaborations have existed between the US and Japan since the 1964 Niigata Earthquake. Both counties have benefitted from this partnership, and have used these experiences as a spring board to lead the rest of the world in seismic design and building standards. The CPT and SASW testing will be performed in close coordination with our Japanese colleagues in an effort to continue this tradition by facilitating cross-training of researchers and students on testing practices in our respective countries, providing an avenue for new and important international collaborations.