The 2022 Goesan earthquake of the moment magnitude 3.8 along the buried fault in the central Korean Peninsula

Abstract

On October 28, 2022, a moment magnitude (Mw) 3.8 earthquake occurred in Goesan, South Korea, typically characterized as a stable continental region. Herein, we analyze 42 earthquakes, including the Mw 3.8 earthquake, the largest foreshock (Mw 3.3), which preceded the mainshock by 17 s, and the largest aftershock (Mw 2.9). The primary aim of this study is to identify interactions among the seismic events. To this end, we utilized the permanent seismic networks with the closest station at 8.3 km from the epicenter, and the temporary network deployed eight hours after the mainshock’s occurrence. Relocation results delineate that the mainshock occurred at the southeastern tip of the hypocenter distribution of three foreshocks, trending west-northwest–east-southeast. The aftershocks form an overall spatially diffused seismic pattern that propagates toward both ends of the inferred lineament in the downdip direction. The rupture directivity of the mainshock, along with waveform similarity across the mainshock and foreshocks, confirms the inferred geometry, corresponding well with the focal mechanisms of the mainshock and the largest foreshock. We demonstrate that the change in Coulomb failure stress (ΔCFS) by the largest foreshock was positive where the mainshock occurred and that the mainshock generated ΔCFS capable of triggering the propagation of the aftershocks.