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1. Vs-based Evaluation of Select Liquefaction Case Histories from the 2010-2011 Canterbury Earthquake Sequence

   Wood, C.M. (January 2017, Journal of geotechnical and geoenvironmental engineering)

   The 2010–2011 Canterbury earthquake sequence included a number of events that triggered recurrent soil liquefaction at many locations in Christchurch, New Zealand. However, the most severe liquefaction was induced by the Mw7.1 September 4, 2010, Darfield and Mw6.2 February 22, 2011, Christchurch earthquakes. The combination of well-documented liquefaction surface manifestations during multiple events, densely recorded ground motions during these events, and detailed subsurface characterization information at the selected sites provides an unprecedented opportunity to add quality case histories to the empirical soil liquefaction database. The authors have already documented and published 50 high-quality liquefaction case histories from these earthquakes using cone penetration test (CPT) data. This paper examines 46 of these case histories using shear-wave velocity (Vs) profiles derived from surface wave (SW) methods and a Christchurch-specific Vs correlation based on CPT tip resistance. The Vs profiles have been used to evaluate the two most commonly used Vs-based simplified liquefaction evaluation procedures (i.e., Andrus and Stokoe and Kayen et al.). An error index (EI ) has been used to quantify the overall performance of these two procedures in relation to liquefaction observations. Although the two procedures are essentially equivalent for sites with normalized Vs (i.e., Vs1) <180 m=s, the Kayen et al. procedure, with 15% probability of liquefaction, provides better predictions of liquefaction triggering for sites with Vs1 greater than 180 m=s. Additionally, total EI values obtained using Vs profiles from surface wave testing in conjunction with the Kayen et al. procedure are lower than two other CPT-based triggering procedures but higher than the total EI value obtained using the Idriss and Boulanger CPT-based procedure. 

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2. Field assessment of liquefaction prediction models based on geotechnical versus geospatial data, with lessons for each

   https://doi.org/10.1177/8755293019899951  

   Geyin, Mertcan; Baird, Alex J.; Maurer, Brett W. (February 2020, Earthquake Spectra)

   Semi-empirical models based on in situ geotechnical tests have been the standard-of-practice for predicting soil liquefaction since 1971. More recently, prediction models based on free, readily available data were proposed. These “geospatial” models rely on satellite remote-sensing to infer subsurface traits without in situ tests. Using 15,223 liquefaction case-histories from 24 earthquakes, this study assesses the performance of 23 models based on geotechnical or geospatial data using standardized metrics. Uncertainty due to finite sampling of case-histories is accounted for and used to establish statistical significance. Geotechnical predictions are significantly more efficient on a global scale, yet successive models proposed over the last 20 years show little or no demonstrable improvement. In addition, geospatial models perform equally well for large subsets of the data—a provocative finding given the relative time- and cost-requirements underlying these predictions. Through this performance comparison, lessons for improving each class of model are elucidated in detail. 

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3. Geotechnical aspects of the 2016 Kaikoura Earthquake on the South Island of New Zealand

   Stringer, M.E. (January 2017, Bulletin of the New Zealand Society for Earthquake Engineering)

   The magnitude Mw7.8 ‘Kaikōura’ earthquake occurred shortly after midnight on 14 November 2016. This paper presents an overview of the geotechnical impacts on the South Island of New Zealand recorded during the post-event reconnaissance. Despite the large moment magnitude of this earthquake, relatively little liquefaction was observed across the South Island, with the only severe manifestation occurring in the young, loose alluvial deposits in the floodplains of the Wairau and Opaoa Rivers near Blenheim. The spatial extent and volume of liquefaction ejecta across South Island is significantly less than that observed in Christchurch during the 2010-2011 Canterbury Earthquake Sequence, and the impact of its occurrence to the built environment was largely negligible on account of the severe manifestations occurring away from the areas of major development. Large localised lateral displacements occurred in Kaikōura around Lyell Creek. The soft fine-grained material in the upper portions of the soil profile and the free face at the creek channel were responsible for the accumulation of displacement during the ground shaking. These movements had severely impacted the houses which were built close (within the zone of large displacement) to Lyell Creek. The wastewater treatment facility located just north of Kaikōura also suffered tears in the liners of the oxidation ponds and distortions in the aeration system due to ground movements. Ground failures on the Amuri and Emu Plains (within the Waiau Valley) were small considering the large peak accelerations (in excess of 1g) experienced in the area. Minor to moderate lateral spreading and ejecta was observed at some bridge crossings in the area. However, most of the structural damage sustained by the bridges was a result of the inertial loading, and the damage resulting from geotechnical issues were secondary. 

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4. Earthquake Geotechnical Engineering Reconnaissance Methods and Advances

   Bray, J.D. (July 2019, 7th International Conference on Earthquake Geotechnical Engineering)

   Earthquake geotechnical engineering is an experience-driven discipline. Field observations are particularly important, because it is difficult to replicate in the laboratory the characteristics and response of in situ soil deposits. Much of the data generated by a major earthquake is perishable, so it is critical that it is collected soon after an event occurs. Detailed mapping and surveying of damaged and undamaged areas provides the data for the well-documented case histories that drive the development of many of the earthquake geotechnical engineering design procedures. New technologies are being employed to capture earthquake-induced ground deformation, including Light Detection and Ranging, Structure-from-Motion, and Unmanned Aerial Vehicles. Post-earthquake reconnaissance has moved beyond taking photographs and field notes to taking advantage of technologies that can capture ground and structure deformations more completely and accurately. Moreover, electronic data enables effective sharing and archiving of the measurements. Unanticipated observations from major events often catalyze new research directions. Important advancements are possible through post-event research if their effects are captured and shared effectively. An overview of some of recent integrated technology deployments and their role in advancing knowledge are presented. 

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5. Select liquefaction case histories from the 2001 Nisqually, Washington, earthquake: A digital data set and assessment of model performance

   https://doi.org/10.1177/87552930231174244  

   Rasanen, Ryan A; Geyin, Mertcan; Maurer, Brett W (January 2023, Earthquake Spectra)

   While soil liquefaction is common in earthquakes, the case-history data required to train and test state-of-practice prediction models remains comparatively scarce, owing to the breadth and expense of data that comprise a single case history. The 2001 Nisqually, Washington, earthquake, for example, occurred in a metropolitan region and induced damaging liquefaction in the urban cores of Seattle and Olympia, yet case-history data have not previously been published. Accordingly, this article compiles 24 cone-penetration-test (CPT) case histories from free-field locations. The many methods used to obtain and process the data are detailed herein, as is the structure of the digital data set. The case histories are then analyzed by 18 existing liquefaction response models to determine whether any is better, and to compare model performance in Nisqually against global observations. While differences are measured, both between models and against prior global case histories, these differences are often statistically insignificant considering finite-sample uncertainty. This alludes to the general inappropriateness of championing models based on individual earthquakes or otherwise small data sets, and to the ongoing needs for additional case-history data and more rigorous adherence to best practices in model training and testing. 

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