Seismic hazard assessment of South Korea

Abstract

Korea is located on the eastern margin of the Eurasian Plate. Although it is far from a plate boundary (the closest distance is about 400-500km), the seismicity is affected by the complex interaction of the collision of the Indo-Australian and the Eurasian plates, and the subduction of the Philippine Sea plates beneath the Eurasian plate along the Japan and the Ryukyu trenches respectively. This paper presents a study on seismic horizontal ground motions for rock sites in South Korea. As part of the study, historical and recent earthquakes have been used. A seismic source model has been developed which incorporates the Korean local tectonic and subduction of the Philippines Sea Plate. Also, recently published empirical and stochastic attenuation relationships have been have been adopted. The seismic hazard for spectral accelerations at structural periods of short period (0.1s) and 1.0 seconds having a 2% probability of being exceeded in the next 50 years are presented as hazard contour maps across South Korea. De-aggregation plots are also shown for a few major cities to investigate the earthquake magnitude and distance combinations. The results show that the subduction zones near Japan contribute significantly to the seismic hazard in South Korea particularly for the longer structural period ground motion.