Traditional inverse distance weighting (IDW) interpolation is a process employed to estimate unknown values based on neighborhoods in 2D space. Proposed in this study is an improved IDW interpolation method that uses 3D search neighborhoods for effective interpolation on vertically connected observation data, such as water level, depth, and altitude. Borehole data are the data collected by subsurface boring activities and exhibit heterogeneous spatial distribution as they are densely populated near civil engineering or construction sites. In addition, they are 3D spatial data that show different subsurface characteristics by depth. The subsurface characteristics observed as such are used as core data in spatial modeling in fields, such as geology modeling, estimation of groundwater table distribution, global warming assessment, and seismic liquefaction assessment, among others. Therefore, this study proposed a seismic liquefaction assessment and mapping workflow using an improved IDW application by combining geographic information system (GIS) (ArcGIS (Esri, Redlands, CA, USA)), NURBS-based 3D CAD system (Rhino/Grasshopper (Robert McNeel & Associates, Seattle, WA, USA)), and numerical analysis system (MATLAB (MathWorks, Natick, MA, USA)). The 3D neighborhood search was conducted by the B-rep-based 3D topology analysis, and the mapping was done under the 2.5D environment by combining the voxel layer, DEM, and aerial images. The experiment was performed by collecting data in Songpa-gu, Seoul, which has the highest population density among the OECD countries. The results of the experiment showed between 7 and 105 areas with liquefaction potentials according to the search distance and the method of the approach. Finally, this study improved users’ accessibility to interpolation results by producing a 3D web app that used REST API based on OGC I3S Standards. Such an approach can be applied effectively in spatial modeling that uses 3D observation data, and in the future, it can contribute to the expansion of 3D GIS application.

An earthquake of moment magnitude 5.4 occurred in Pohang, South Korea on November 15, 2017. This earthquake of moderate magnitude induced failures of structures and buildings and led to ground displacements. Approximately 600 sand boils were observed in the vicinity of the epicenter. We conduct 26 multichannel analysis of surface waves (MASW) tests and obtain three shear wave velocity ($V_S$ ) profiles from suspension Compression (P) and Shear (S) wave logging at liquefied and nonliquefied sites near the epicenter. The phase velocities at frequencies lower than 10 Hz at the liquefied sites were smaller than those at the nonliquefied sites. The cyclic stress ratios (CSRs), cyclic resistance ratios (CRRs), and factors of safety were calculated. The CRR curves for these approaches predicted sand boils in Pohang with an accuracy of 79.5%. The liquefaction potential index (LPI) was calculated at 29 sites and is geospatially interpolated to create maps near the epicenter. The LPI maps had a maximum accuracy of 77% when LPI thresholds were 8 and 2 for two approaches from the literature. The high accuracies from both local and regional liquefaction evaluations demonstrate the applicability of the existing approaches for moderate earthquakes in South Korea.

This study describes the methodology employed to construct a seismic fragility function based on a pre-existing numerical model tailored for underground stations. Employing a dynamic numerical model, a comprehensive analysis encompassing 110 distinct cases was conducted, each varying in soil depth and classification. Seismic waves, conforming to the standard design spectrum, were utilized within these numerical analyses. The formulation of the fragility function within the constructed model follows a structured approach, segmented by damage indices and severity levels. This systematic breakdown serves to outline the fundamental framework for establishing the fragility function, providing insights into its development process. Subsequently, the derived fragility function underwent a rigorous comparative analysis against established seismic fragility functions from prior studies. This comparative assessment serves as a critical evaluation tool, allowing for an appraisal of the suitability and robustness of the newly developed fragility function in relation to existing benchmarks.

Traditionally, in the codes for seismic performance evaluation of pile-supported structures (PSS), the piles are modeled using either a virtual fixed-point (VFP) method or a soil spring method, which can additionally simulate soil-pile interactions. The applicability and accuracy of the VFP method, which is originated from statically loaded piles, to evaluate piles under seismic loads has not been sufficiently explored, despite the popularity of the technique. Thus, this study evaluates the applicability of the VFP in the seismic design of PSS through pseudostatic and response spectrum analyses (RSA). Our results indicated that there was a significant difference in between the experimentally derived and VFP model-derived values for the natural period, acceleration, and moment response of the structure. This difference occurs because the soil-pile interaction is simulated through the fixed end in the VFP model.

Since Shinhama is unimproved clay soil, the long-term surface settlement has been monitored continuously from 1970’s. It has been also confirmed that the settlement is being accelerated by some earthquakes, and a significant change in the settlement patterns was observed in the 2011 off the Pacific coast of Tohoku earthquake. In this study, the concept of the consolidation settlement potential, which represents the maximum value of the consolidation settlement, was proposed and applied to estimate the post-earthquake settlement quantitatively using the undisturbed clayey specimen taken from the Shinhama, Shiogama, Japan. Furthermore, a map of post-earthquake consolidation settlement was proposed as the result of this study, and finally the consolidation settlement resulted from the 2011 off the Pacific coast of Tohoku earthquake was reviewed based on the finite strain consolidation approach.