Evaluation of the applicability of ground motion models (GMMs) for South Korea

Abstract

South Korea was considered a stable continental region (SCR) until the recent seismic events, specifically the 5.5- and 5.4- magnitude earthquakes in Gyeongju and Pohang, respectively, highlighting the need for reliable ground-motion models (GMMs), which are key to seismic hazard assessment analysis. Although it is appropriate to employ GMMs that are tailored to regional characteristics, irrespective of whether they are developed based on a stochastic method or actual data, a model that is similar to the tailored GMM can also be used. Recently, several earthquakes with magnitudes greater than 5 have occurred in South Korea, enabling us to assess whether the GMMs previously developed in Korea or those applied for South Korea's disaster management system are suitable for use throughout the country. Therefore, this study conducted an evaluation to assess the suitability of GMMs tailored to domestic characteristics. GMMs developed for various regions including active crustal regions, SCRs, and South Korea, were employed. Amplification functions were applied to several GMMs developed for hard rock sites. A total of 48 GMMs, considering site effects, were compared using the Korean earthquake ground motion data. The suitability of GMMs for Korea was assessed through statistical techniques such as log-likelihood method, multivariate logarithmic score, Euclidean distance-based ranking, Euclidean metric distance, deviance information criterion, and cumulative-distribution-based area metric method. Ensemble GMMs were also developed based on the rank results and analyzed using statistical methods. Un-normalized weight was used to calculate the outcomes of the above mentioned six ranking methods, and weighted GMMs were judged to be optimal for South Korea.