Dynamic earthquake rupture modeling considering regional crustal stress conditions in southeastern Korea

The Korean Peninsula is located in a low-seismicity zone at the eastern margin of the Eurasian plate. However, the 2016 Gyeongju and 2017 Pohang earthquakes, which occurred in southeastern Korea, highlight the importance of advanced seismic hazard assessment and mitigation in this region. We successfully performed spontaneous dynamic rupture modeling by considering the crustal stress field in southeastern Korea, constrained by earthquake focal mechanism data, to better understand the seismic hazard in the region. We found that the geologically recognized Yangsan fault trace near the location of the Gyeongju earthquake is not aligned well with the favorable shear rupture directions, given the current crustal stress field in the region. The fault needs to be very weak (i.e., have a low static friction coefficient) to initiate a large earthquake rupture. However, our dynamic model results show that the fault plane constrained by the focal mechanism solution of the 2016 Gyeongju earthquake is more favorably aligned for shear rupture under the current stress condition and that it may be able to produce a relatively large earthquake if the extension of the fault is quite long (~60 km). This type of dynamic rupture modeling study may help to more accurately elucidate the seismic hazard in a low-seismicity zone such as southeastern Korea.