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

这项快速反应研究补助金(RAPID)奖是一项详细研究，专门关注2011年3月11日日本东北9.0级地震(这是有记录以来最大的地震之一)中，由可液化土壤覆盖的一组选定的强地面运动记录站的土壤条件。地震发生后，岩土极端事件勘测协会(Geer)的一个先遣团队前往日本，与来自日本岩土学会、城市地震工程中心和港口与机场研究所的日本同事协调易腐烂数据的收集和研究工作。在这次访问中，在发生液化的关键强地面运动记录站进行的圆锥渗透测试(CPT)和面波频谱分析(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先遣小组走访了关东平原地区可液化土壤之下的14个强地面运动记录站，其中包括几个同时有井下和地面记录的站。这些观测站的峰值地面加速度在0.14到0.22克之间，其中7个观测站观测到了地面液化的证据。此外，港口和机场研究所表示，他们在更靠北的地方有几个强地震动记录站，那里的震动更强，下面是可液化的土壤，包括一些经过地基改善的。这些关键的地面运动记录代表了一组独特的数据，它们捕捉到了这次9.0级地震造成的长时间震动期间软土的动态响应和液化。因此，这些数据可用于锚定液化触发曲线和改进量级比例因子，评估估计地表变形的程序，并评估可液化土壤的动态场地响应分析模型。然而，在随后的分析能够准确进行之前，对这些地点进行适当的表征是必不可少的一步。目前，这些场地的地下信息仅限于每个场地的单一标准贯入试验(SPT)和井下横波速度(Vs)剖面。将获得六个或更多最重要的强震记录站的CPT测深和来自SASW测试的许多额外的VS剖面。在美国和世界大部分地区，在评估液化触发时，CPT通常比SPT更受欢迎，但由于各种原因，CPT在日本相对不常见，这项工作不太可能由我们的日本同事完成。这项工作是一项重要而有价值的贡献，将提高这些案例的价值，并将它们与美国的实践联系起来。这个项目的紧迫性是因为：(1)震后修复工作的可能性，这可能会改变关键地点的地面条件，以及(2)需要快速分发CPT和SASW结果，如果在将地面运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预测和模拟液化效应的程序的显著进步。自1964年新泻地震以来，美国和日本之间一直存在着重大的研究合作。这两个国家都从这一伙伴关系中受益，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，通过促进研究人员和学生在我们各自国家的测试实践方面的交叉培训，努力延续这一传统，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.