The 2024 M_L 4.8 Buan earthquake sequence and aligned multiple clusters in the southwestern Korean Peninsula

Intraplate earthquakes can produce destructive seismic events despite occurring far from active plate boundaries and in seemingly tectonically stable regions. This study investigates the seismicity and fault stability in the southwestern Korean Peninsula, focusing on the 2024 M_L 4.8 Buan earthquake sequence and surrounding seismic clusters. We identified distinct spatial patterns and fault orientations influencing local seismicity, revealing that the Buan mainshock occurred along a steep, NNE-SSW trending, right-lateral strike-slip fault, intersecting nearly orthogonally with a less active WNW-ESE oriented fault. Stress inversion analysis indicated a predominantly horizontal maximum principal stress oriented approximately ENE-WSW. Rate-and-state friction simulations demonstrated high rupture potential for the NNE-SSW fault under current stress conditions, whereas the WNW-ESE fault required significantly reduced frictional strength, localized heterogeneities in fault properties, or dynamic triggering to rupture. The NNE-SSW aligned earthquake clusters and the coherence of their focal mechanisms further confirmed that they are likely in favorable conditions for seismic activity within this fault system. At the same time, the uneven distribution and localized clustering of these earthquakes suggest complex fault fragmentation and localized strain concentration. These findings highlight the importance of detailed fault characterization to enhance understanding intraplate earthquake mechanisms and improve seismic hazard assessments.