The pre-mainshock, post-mainshock, and combined pre-mainshock and post-mainshock sequences of the mL 7.4 Haicheng earthquake on February 4, 1975, are shown in Figure S5 as magnitude rank-ordering plots (non-normalized complementary cumulative frequency-magnitude distribution, CCFMD) for various density threshold fth.
Based on the completeness magnitude mc (vertical gray line) and the dragon-king earthquake candidate transition magnitude mt (vertical gray dashed line), the testing framework for the dragon-king earthquake separates the frequency-magnitude distribution into three different regions: the incomplete part (light gray solid circles), the Gutenberg-Richter part (dark gray solid circles), and the dragon-king candidate part (black solid circles).