Global controls on aftershock productivity: roles of magnitude and tectonic setting

Abstract. Aftershock productivity varies substantially among large earthquakes, yet the relative roles of magnitude, tectonic environment, and source properties remain incompletely resolved at the global scale. Here we perform a comprehensive, data-driven analysis of aftershock productivity for all Mw ≥ 7.0 mainshocks worldwide since 1976, using a homogeneous workflow based on USGS/NEIC catalogs, PB2002 plate-boundary geometries, and uniformly defined aftershock windows (r ≤ 200 km, t ≤ 30 days, M ≥ 4.5). Mainshock events are classified into three tectonic domains—subduction, other plate boundaries, and intraplate/crustal—allowing systematic comparison of productivity patterns across geodynamic settings. Across all tectonic classes, aftershock productivity scales linearly with mainshock magnitude in log-space, with nearly identical slopes (b ≈ 0.76–0.81), indicating a universal magnitude-controlled triggering mechanism. In contrast, intercepts differ significantly among tectonic environments: subduction earthquakes are systematically the most productive, followed by other plate-boundary events and intraplate earthquakes. Depth and distance to the nearest plate boundary exert weaker but physically interpretable secondary influences, with productivity decreasing for deeper ruptures and for intraplate events located far from plate boundaries. Residual analysis and multivariate correlations confirm that magnitude and tectonic setting explain the dominant share of global variability, whereas depth and distance provide secondary, context-dependent modulation. Together, these results establish the first unified, physically interpretable global framework of aftershock productivity, quantifying both universal magnitude-driven scaling and environment-specific productivity offsets. The findings provide actionable constraints for global ETAS parameterization, operational aftershock forecasting, and seismic-hazard models for future great earthquakes.