An Updated, Homogeneous, and Declustered Earthquake Catalog for South Korea and Neighboring Regions

Abstract. The fundamental components for evaluating seismic hazards and forecasting earthquake events in a region include a complete and homogeneous earthquake catalog. Previously, a few studies were performed to combine earthquake databases from various sources to produce a unified earthquake catalog for the Korean Peninsula. To conduct seismic hazard assessments across these regions, this study proposes creating a comprehensive, up-to-date, and unified earthquake catalog for South Korea and its neighboring regions using data from multiple sources. We collected data from the Korea Meteorological Administration (KMA), the International Seismological Centre (ISC), and the Japan Meteorological Agency (JMA). The earthquake database covers the time-period from 1905 to 2023, and the geographical area spans 31°–43° N and 122°–132.5° E. As creating a new earthquake catalog entails combining information from many earthquake record sources, we avoided duplication of occurrences that may arise during the integration process by carefully analyzing the timing and location criteria for each earthquake event. To unify the magnitude scale and produce a homogeneous earthquake catalog, both global and regional empirical equations were used to convert the moment magnitude (M_W) and other reported magnitude scales. The resulting homogeneous catalog comprises 63,298 earthquake events, with M_W ranging from 2.0 to 7.9. Declustering of the homogeneous catalog was then conducted to remove dependent events, such as foreshocks and aftershocks, and to identify the mainshocks. Four declustering methods were used to compare and examine their individual influences on mainshock identification in the catalog. The resulting unified and declustered earthquake catalog provides a useful and dependable database for seismicity analysis, seismotectonic studies, and seismic hazard assessments in and around South Korea.