Comparison of earthquake catalogs declustered from three different methods in the Korean Peninsula

Abstract

Abstract The earthquake catalog includes both dependent earthquakes, which are spatio-temporally related to each other, and independent or background earthquakes. In order to predict the long-term seismicity or perform seismic hazard research, the dependent earthquakes must be removed to generate a declustered earthquake catalog. However, several declustering methods have been proposed, and the evaluation of seismic hazard may vary depending on the selected declustering method. 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 of Gardner and Knopoff (1974), Reasenberg (1985), and Zhuang et al. (2002), and the resultant catalogs are compared. The values of the seismicity parameters (a and b) in the Gutenberg-Richter relationship are estimated from the declustered catalogs, and are seen to vary depending on the declustering method, thereby affecting the results of long-term earthquake prediction or seismic hazard analysis. In addition, three approaches are used to test whether the original (raw) and declustered catalogs follow the Poisson process or not. The minimum magnitude (Mp) above which the null hypothesis of the Poisson process cannot be rejected in the earthquake catalog is shown to range from 1.6 to 2.2 depending on the declustered catalog and the test method used. Further, the Mp obtained herein shows a large value compared to the completeness magnitude estimated in the present study. A comparison of the curves representing the cumulative number of background earthquakes versus the elapsed time for the various declustered catalogs shows that the method of Zhuang et al. (2002) gives the closest agreement with the real background seismicity curve.