Seismic Hazard Assessment in the Southeastern Korean Peninsula for Large Earthquakes in Northern Kyushu, Japan: A 3D Numerical Simulation of Pseudodynamic Rupture Scenarios

Abstract

Active fault segments in the Northern Kyushu area are of concern in seismic hazard analysis of the southeastern Korean Peninsula (KP) due to their proximity. In this study, we numerically simulate the peak ground motions at the southeastern KP for Mw 6.7–7.1 earthquake scenarios at five major active fault segments located in northern Kyushu: Kego SouthEastern, Nishiyama OshimaOki, Nishiyama Nishiyama, Kikugawa Central, and Kikugawa Northern fault segments. We conducted fully 3D seismic-wave propagation simulations integrating 3D seismic velocity model and earthquake scenarios generated through pseudodynamic rupture modeling. After applying the region-specific attenuation value, the predicted peak ground velocities (PGVs) ranged from 0.18 cm/s (modified Mercalli intensity [MMI] III) to 26.76 cm/s (MMI VIII), depending on the earthquake scenarios. The PGV distributions were influenced by several factors, such as crustal velocity anomalies, rupture directivity, and the distribution of source parameters on the fault plane. Despite the fixed fault geometries, magnitudes, and hypocenters, significant variations in peak ground-motion distributions were simulated due to differences in the source statistics. The estimated probability density distributions of PGV indicated a significant likelihood of peak ground motions surpassing 20 cm/s in the Yeongnam Province. Furthermore, we identify a linear relationship between the average PGV values and standard deviation across 20 scenarios for each fault segment, to quantify the uncertainty in the PGV distributions.