Comparison of earthquake catalogs for the Korean Peninsula declustered using three different methods

Earthquake catalogs include dependent earthquakes, which are spatiotemporally related, and independent or background earthquakes. In order to predict long-term seismicity or conduct a seismic hazard assessment, the dependent earthquakes must be removed to generate a declustered earthquake catalog. Several declustering methods have been proposed to date; however, the result of seismic hazard assessment may vary depending on which declustering methods are selected. In the present study, the catalog of earthquakes that were observed between 2016 and 2021 in and around the Korean Peninsula is declustered using the methods proposed by Gardner and Knopoff [1974], Reasenberg [1985], and Zhuang et al. [2002], and the resultant catalogs are compared. The seismicity parameters (a- and b-values) in the Gutenberg-Richter relationship are found to vary among the three declustered catalogs, thus affecting long-term earthquake predictions and seismic hazard assessment. The raw (original) and three declustered catalogs are also tested to see whether they follow the Poisson process. The minimum magnitude ( ) above which the null hypothesis of the Poisson process cannot be rejected in the earthquake catalogs ranges from 1.6 to 2.2, depending on the declustered catalog. Further, the obtained herein shows a large value compared to the completeness magnitude estimated in the present study. Comparing the curves representing the cumulative number of background earthquakes against the elapsed time for the declustered catalogs shows that the method by Zhuang et al. [2002] produces the result in the closest agreement with the real background seismicity curve.