Dynamic Rupture Models of the 2016 ML 5.8 Gyeongju, South Korea, Earthquake, Constrained by a Kinematic Rupture Model and Seismic Waveform Data

Abstract

ABSTRACT The ML 5.8 earthquake that jolted Gyeongju in southeastern Korea in 2016 was the country’s largest inland event since instrumental seismic monitoring began in 1978. We developed dynamic rupture models of the Gyeongju event constrained by near-source ground-motion data using full 3D spontaneous dynamic rupture modeling with the slip-weakening friction law. Based on our results, we propose two simple dynamic rupture models with constant strength excess (SE) and slip-weakening distance (Dc) that produce near-source ground-motion waveforms compatible with recorded ones in the low-frequency band. Both dynamic models exhibit relatively large stress-drop values, consistent with previous estimates constrained by source spectrum analyses. The fracture energy estimates were also larger than those predicted by a scaling relationship with the seismic moment. The dynamic features constrained in this study by spontaneous rupture modeling and waveform comparison may help understand the source and ground-motion characteristics of future large events in southeastern Korea and thus the seismic hazard of the region.