[S-SS09] 強震動・地震災害

[SSS09-P20] Chinese site classification based on time-averaged shear wave velocity for the top 30 meters (V_S30)

*Junju Xie¹、Kewei Li¹、Xiaojun Li²、Zhao An ¹、Pengfei Wang³ (1.Institute of Gepphysics,China Earthquake Administration、2.Beijing University of Technology、3.University of California, Los Angeles)

キーワード：site classification, shear wave velocity, seismic fortification, VS30-based models, seismic design codes

Classification of engineering sites is essential when considering different site conditions, for seismic fortification in seismic design codes. However, because of the different site classification methods currently used, it is difficult for China to share site metadata (e.g., site classes) and relevant studies with a larger community. This issue also prevents China from utilizing well-established models that are based on the time-averaged shear wave velocity for the top 30 m (V_S30). In this study, we first assembled the shear wave velocity (V_S) profile data from various sites in Mainland China, Japan, and California, to study the statistical characteristics of V_S30 and the equivalent shear wave velocity (V_Se, time-averaged within soil layers for no more than 20 m) . Notably, a single V_Se parameter could not be used to significantly distinguish between the different Chinese site classes, especially for site classes III and IV that consider soil layers deeper than 20 m. However, the V_S30 values of the Chinese site classes from I₀ to IV portrayed significant distinctions. We also developed a novel V_S30-based site classification method for Chinese sites. The boundaries of V_S30 for each Chinese site class were determined by maximizing the correct classification rate. The mean and intervals of the V_S30 values for each Chinese site class were also calculated. This novel method of classification can facilitate the connection of Chinese site classes with well-developed V_S30-based models and simplify the process of site metadata sharing between China and other countries.