Spatiotemporal coupling of correlation fractal dimension and b-value in seismic zones of Taiwan: Statistical trends, regional variations, and physical implications

This study investigates the spatiotemporal relationship between the correlation fractal dimension (Dc) and the Gutenberg–Richter b-value across 27 seismic zones in Taiwan, using earthquake catalog data from 1973 to 2023. Temporal evolution curves reveal diverse Dc trends, with several eastern and central zones (e.g., S04, S14A, S06) showing pronounced long-term decreases, potentially reflecting stress concentration and fault segmentation effects. Spatial mapping of earthquake epicenters and event statistics highlights strong heterogeneity in seismic productivity. Regression analyses indicate significant positive Dc–b correlations in selected zones, with Pearson’s R² exceeding 0.8 in S05B, S06, and S17A, implying consistent scaling behavior between magnitude–frequency distributions and spatial clustering. Fixed-window versus cumulative-window b-value comparisons reveal that Δb variations are most pronounced in tectonically active zones, coinciding with higher Kendall and Pearson correlation coefficients between Dc and b-values. These results demonstrate that the coupled evolution of Dc and b-values provides a sensitive indicator of seismogenic state changes, particularly in regions with persistent stress loading. The proposed multi-parameter approach offers new potential for seismic hazard assessment by integrating spatial fractal analysis with temporal magnitude–frequency variations, thereby enhancing the understanding of regional earthquake preparation processes in Taiwan’s complex tectonic environment.