Correction factors for GMMs considering site and topographic effects in South Korea

Abstract

In the past five years, the local magnitude (M-L) 5.8 Gyeongju and M(L)5.4 Pohang earthquakes have caused significant damage to the southeastern Korean Peninsula. To evaluate the ground motion recorded during these earthquakes, we compared them with the Korean ground motion models (GMMs), also known as the ground motion prediction equations (GMPEs), Next Generation Attenuation of Ground Motions (NGA) GMMs for Western U.S. and Central and Eastern North America. The ground motions exhibit amplification near a period of 0.1 s compared to the predicted spectral accelerations. These amplifications are likely to be attributed to site and topographic effects. The existing GMMs do not account for the topographic amplification which might be prevalent in the mountainous regions of Korea. Therefore, we propose correction factors for the predicted ground motions for various periods in terms of magnitude, source-to-site distance, V-S30, and relative elevation. The standard deviation values of the residuals significantly decreased by applying these correction models.